Graphitic carbon nitride with metal oxide and production process thereof

Abstract

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.

Description

[0001] DESCRIPTION

[0002] TITLE OF INVENTION

[0003] GRAPHITIC CARBON NITRIDE WITH METAL OXIDE AND PRODUCTION PROCESS THEREOF

[0004] TECHNICAL FIELD

[0005] The present invention mainly relates to a process for preparing graphitic carbon nitrides, in particular a process for preparing a mixture of graphitic carbon nitride with metal oxide.

[0006] BACKGROUND ART

[0007] A UV protecting effect is one of key factors for cosmetic products. Graphitic carbon nitride, which is an inorganic compound, is known to exhibit UV absorbing properties. Regarding techniques for manufacturing carbon nitride materials, some documents have been published so far.

[0008] For example, JP2020-152609A discloses a method for producing graphitic carbon nitride in a higher yield and at a lower cost, and to provide a novel graphitic carbon nitride.

[0009] Make-up cosmetic compositions are used in order to provide keratinous substances, such as skin, in particular facial skin, with desired color appearance. A development for a new efficient manufacturing process for graphitic carbon nitrides as eco-friendly, UV absorbing materials is demanded.

[0010] DISCLOSURE OF INVENTION

[0011] As objective of the present invention is to provide a process for manufacturing graphitic carbon nitrides efficiently, which are suitable in cosmetic use.

[0012] The above objective of the present invention can be achieved by a process for preparing graphitic carbon nitrides, comprising a step of heating at least one precursor compound with at least one metal oxide particle.

[0013] The precursor compound may be selected from urea, thiourea, melamine, guanidine, arginine, cyanamide, dicyandiamide, and a salt thereof, and combinations thereof.

[0014] The metal oxide particle may be selected from silica (SiCL), zeolite and aluminium oxide (AI2O3) particles, and mixtures and composites thereof.

[0015] The metal oxide particle may have an average particle size ranging from 0.01 to 30 pm, preferably from 0.05 to 20 pm.

[0016] The weight ratio of the precursor compound and the metal oxide particle may 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 in particular from 1 :5 to 5:1.

[0017] The heating may be carried out at least 450 °C and for a period of at least 1 minute. The heating may be carried out in the presence of oxygen-containing species, such as O2 (especially with oxygen flux) and / or humidity.

[0018] The process may comprise additional pre-heating step for the precursor compound or the metal oxide particle, or both of the precursor compound and the metal oxide particle.

[0019] The graphitic carbon nitride may have a porous structure.

[0020] 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.

[0021] The weight ratio of the graphitic carbon nitride and the metal oxide particle in the product may 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 in particular from 1 :5 to 5: 1.

[0022] The mixture product may have an onset absorption edge value ranging from 390 to 430 nm, preferably from 395 to 420 nm.

[0023] The present invention also relates to a use of the mixture product according to the present invention as UV absorbers.

[0024] The present invention also relates to a composition, preferably a cosmetic composition for keratinous substances, such as skin, comprising the mixture product according to the present invention.

[0025] The composition may be a sunscreen composition.

[0026] BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 shows IR spectra of the products according to Example 4 and Comparative Example 3 in the examples.

[0028] Figure 2 shows a comparison of the UV-vis absorption spectra curve between the products according to Example 1 and Comparative Example 1 in a form of 0.1% by weight of suspension in water.

[0029] Figure 3 shows UV-vis absorption spectra curve measured with the mixture product according to Example 4 in a form of 0.1% by weight of suspension in water.

[0030] BEST MODE FOR CARRYING OUT THE INVENTION

[0031] After diligent research, the inventors have surprisingly found that graphitic carbon nitrides having at least one heptazine unit can be efficiently produced by heating precursor compounds with metal oxide particles, and that the product is suitable for cosmetic use, and thus completed the invention.

[0032] Thus, the present invention mainly relates to a process for preparing graphitic carbon nitrides comprising a step of heating precursor compounds with metal oxide particles. The inventors of the present invention discovered that making graphitic carbon nitrides provides the graphitic carbon nitrides with enhanced whiteness.

[0033] Thus, the process according to the present invention can produce graphitic carbon nitrides with enhanced whiteness.

[0034] Hereafter, the present invention will be described in a detailed manner.

[0035] [Process]

[0036] The present invention 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.

[0037] The term "graphitic" in graphitic carbon nitride 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 or a sheet structure. The graphitic carbon nitride is generally solid at room temperature, and in a powder form.

[0038] The graphitic carbon nitride of the present invention may comprise at least one heptazine unit. In the present specification, the heptazine unit means a hetero-fused ring consisting of three hetero rings consisting of C atoms and N atoms, represented with CeN?. Thus, the graphitic carbon nitride of the present invention may have a heptazine-based monolayer structure.

[0039] The graphitic carbon nitride of the present invention may comprise at least one heptazine unit, at least one triazine unit, and a combination 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.

[0040] 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 nano-porous structure. The pores may exist on the layered structure of the graphitic carbon nitride between heptazine units and triazine units.

[0041] The graphitic carbon nitride of the present invention can exhibit a UV absorption property. Preferably, the graphitic carbon nitride has the absorption effect against both regions of UV-B and UV-A rays. UV-B rays here means UV rays having a wavelength between 280 to 320 nm. UV-A rays here means UV rays having a wavelength between 320 to 400 nm. An absorption curve in a range of ultraviolet light and visible light can be measured by, for example, ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy.

[0042] The process according to the present invention comprises a step of heating at least one precursor compound with at least one metal oxide particle. Thus, the process according to the present invention comprise a step of heating a mixture of at least one precursor compound and at least one metal oxide particle.

[0043] One precursor compound may be used as a raw material of the graphitic carbon nitride, or two or more precursor compounds may be are used in combination.

[0044] The precursor compound may be selected from the precursor known by one skilled in the art, for example, urea, thiourea, melamine, guanidine, arginine, cyanamide, dicyandiamide, and a salt 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 a salt thereof and the combination thereof.

[0045] The salt of the precursor compound is not particularly limited, but mention can be made of salts with inorganic acids, such as carbonic acid and hydrochloric acid.

[0046] In one preferred embodiment of the present invention, only one precursor compound is used.

[0047] The at least one precursor compound is heated with at least one metal oxide particle in the process. The metal oxide particle may be selected from silica (SiCh), zeolite, aluminium oxide (AI2O3) particles, and mixtures thereof, and preferably selected from silica (SiCh) 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 particle can work as a catalyst for a synthesis of the graphitic carbon nitrides.

[0048] The metal oxide particle may have an average particle size of 0.01 pm or more, preferably 0.05 pm or more, and / or of 30 pm or less, preferably 25 pm or less, and more preferably 20 pm or less. The term “average particle size” used herein can represent a volume-average size mean diameter which is given by the statistical particle size distribution to half of the population, referred to as D50. For example, the average particle size can be measured by a laser diffraction particle size distribution analyzer, such as Mastersizer 2000 by Malvern Corp.

[0049] The metal oxide particle may have an average particle size ranging from 0.01 to 30 pm, preferably from 0.05 to 25 pm.

[0050] In one embodiment of the present invention, the metal oxide particle is porous. In this embodiment, the pore diameter of the metal oxide particle is not particularly limited, but may range from 0.3 nm to 1 nm.

[0051] The weight ratio of the precursor compound to the metal oxide particle is not particularly limited. For example, the weight ratio of the precursor compound and the metal oxide particle may 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 in particular from 1 :5 to 5: 1.

[0052] The process according to the present invention comprise a step of heating a mixture of the at least one precursor compound and the at least one metal oxide particle.

[0053] The temperature for heating may be at least 450 °C. Preferably, the heating is carried out at 500 °C or more, and more preferably at 525 °C or more, and may be 800 °C or less.

[0054] The period or the heating may be at least 1 minute. Preferably, the period of the heating is at least 10 minutes, more preferably at least 20 minutes, and / or within 30 hours, and more preferably within 25 hours.

[0055] The heating can be carried out in air, in noble gas, such as argon or helium, or in inert gas, such as nitrogen. In preferred embodiments of the present invention, the heating is carried out in air or in argon. In one preferred embodiment, the heating is carried out in a presence of oxygen, such as in air. In one preferred embodiment, the heating process may be carried out in a presence of oxygencontaining species, such as O2, humidity, O3, atomic O, and / or ionic oxygen, as an oxidizing agent. While not wishing to be bound by theory, it is believed that more porous graphitic carbon nitride can be obtained when the heating is carried out in the presence of oxygencontaining species. In the preferred embodiment, the heating is carried out in air, or in noble gas or inert gas including oxygen-containing species.

[0056] In a preferred embodiment, in addition to oxygen in the air, the heating process is carried out in the presence of oxygen-containing species, such as O2, humidity, ozone O3, O atomic and / or ionic oxygen, as an oxidizing agent.

[0057] In a preferred embodiment, the heating process is carried out in a presence of oxygencontaining species of O2, in particular oxygen flux, and / or humidity. The term "oxygen flux" can mean an oxygen flow in the present specification.

[0058] Preferably the oxidizing agent used during the heating step is in a gas form.

[0059] According one embodiment the oxygen source is neither from permanganate salt nor from hydrogen peroxide.

[0060] 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 pre-heating step prior to the heating step as explained above.

[0061] The pre-heating step may be applied to the precursor compound or the metal oxide particle, or both of the precursor compound and the metal oxide particle.

[0062] The temperature for the pre-heating may at least 200 °C. Preferably, the pre-heating is carried out at 250 °C or more, and more preferably at 275 °C or more, and may be 800 °C or less.

[0063] The period for the pre-heating may be at least 5 minutes. Preferably, the period of the preheating is at least 10 minutes, more preferably at least 20 minutes, and / or within 30 hours, and more preferably within 25 hours.

[0064] The pre-heating can be carried out in air, in noble gas, such as argon or helium, or in inert gas, such as nitrogen. In preferred embodiments of the present invention, the pre-heating is carried out in air or in argon. In one preferred embodiment, the heating process is carried out in a presence of oxygen, such as in air.

[0065] In one embodiment of the present invention, a cooling step is present between heating steps. Thus, in one embodiment, the cooling step is included between the first heating step and the second heating step. The temperature for the cooling step is not particularly limited, but for example, the temperature is cooled to a room temperature (about 25 °C). The period of the cooling step is not particularly limited, but for example is about from 1 minute to 24 hours.

[0066] The process according to the present invention can produce the graphitic carbon nitride with an improved yield. For example, the process according to the present invention can produce the graphitic carbon nitride in a weight yield of 6% or more, preferably 7% or more, and more preferably 8% or more.

[0067] [Mixture Product]

[0068] The present invention also relates to the mixture product prepared by the process of the process according to the present invention.

[0069] The product of the present invention comprises the graphitic carbon nitrides and the metal oxide particles. Thus the product of the present invention is a mixture of the graphitic carbon nitride and the metal oxide particles. The same descriptions of the graphitic carbon nitride and the metal oxide particle can be applied to the explanations for the product here.

[0070] The weight ratio of the graphitic carbon nitride to the metal oxide particle in the product is not particularly limited. For example, the weight ratio of the graphitic carbon nitride and the metal oxide particle in the product may 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 in particular from 1 :5 to 5:1.

[0071] The mixture product of the present invention can exhibit a UV absorption property because of the presence of the graphitic carbon nitride. Preferably, the mixture product has the absorption effect against both regions of UV-B and UV-A rays.

[0072] The UV absorption property of the mixture product of the present invention can be represented by an onset absorption edge value (nm). The onset absorption edge value can be defined with a wavelength (nm) at an intersection of a straight line drawn to fit a region where an absorbance curve drops sharply from a shorter wavelength side of an absorbance curve, and a straight line drawn to fit an absorbance curve in a wavelength range of 500 to 550 nm.

[0073] Example 1 in Figure 2 depicts an example of the onset absorption property being 400 nm, which is a wavelength at the intersection of the (1) straight line drawn to fit a region where the absorbance curve drops sharply from a shorter wavelength side of the absorbance curve, and the (2) straight line drawn to fit the absorbance curve in a certain range of a wavelength range between 500 to 550 nm, where the absorbance curve becomes constantly low. An absorption curve in a range of ultraviolet light and visible light can be measured by, for example, ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy.

[0074] The inventors of the present invention surprisingly discovered that the mixture product of the present invention can exhibit a lower onset absorption edge value than a product produced without the metal oxide particle. The lower onset absorption edge value indicates the less color the product has, and less color materials can exhibit enhanced whiteness. Thus, the mixture product of the present invention is versatilely applicable to various uses, in particular a use in cosmetic products.

[0075] The mixture product of the present invention may have the onset absorption edge value of 390 nm or more, preferably 395 nm or more, and in general 430 nm or less, preferably 420 nm or less.

[0076] The graphitic carbon nitride of the present invention may have the onset absorption edge value ranging from 390 to 430 nm, preferably from 395 to 420 nm. [Use]

[0077] The present invention also relates to a use of the mixture product of the present invention as UV absorbers. For example, the UV absorber of the present invention can be used in paints, coatings, as a filler especially of plastics, and cosmetics. The UV absorber can be UVA and / or B absorber.

[0078] Because the mixture product of the present invention has sufficient UV absorption property and less color, it is very useful for various products requiring UV protection.

[0079] [Composition]

[0080] The present invention also relates to a composition including the mixture 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 skin. In one preferred embodiment, the composition according to the present invention is a sunscreen composition.

[0081] The keratinous substance here means a material containing keratin as a main constituent element, and examples thereof include the skin, scalp, nails, lips, hair, and the like, and preferably skin.

[0082] Because the mixture product of the present invention can show sufficient UV absorption property and less color, the cosmetic composition according to present invention can provide keratinous substances with sufficient UV protection without change of color tone.

[0083] The details of the compositions for the use according to the present invention are explained in the section titled [Process] above.

[0084] EXAMPLES

[0085] The present invention will be described in a more detailed manner by way of examples. However, these examples should not be construed as limiting the scope of the present invention.

[0086] [Preparation]

[0087] Example 1

[0088] 0.6 g of urea was pre-heated at 300 °C in air for 1 hour. The pre-heated urea was mixed with 2.4 g of zeolite (HS-642, Powder, Sodium Mordenite, FUJIFILM Wako Chemical Corporation, crystal size: 0.1 pm x 0.5 pm, average particle size: 12 pm, pore aperture: 0.7 nm) and the mixture was heated at 550 °C in air for 1 hour to produce the mixture of graphitic carbon nitride and zeolite.

[0089] Comparative Example 1

[0090] 3 g of urea was pre-heated at 300 °C in air for 1 hour. The pre-heated urea alone was heated at 550 °C in air for 1 hour to produce the graphitic carbon nitride alone. Example 2

[0091] A mixture of 10 g of urea and 3 g of silica (average particle size: 5 pm) was heated at 600 °C in air for 2 hours to produce the mixture of graphitic carbon nitride and silica.

[0092] Example 3

[0093] 3 g of silica (average particle size: 5 pm) was pre-heated at 600 °C in air for 2 hours. The pre-heated silica was mixed with 10 g of urea, and the mixture was heated at 600 °C in air for

[0094] 2 hours to produce the mixture of graphitic carbon nitride and silica.

[0095] Comparative Example 2

[0096] 10 g of urea was heated at 600 °C in air for 2 hours to produce the graphitic carbon nitride alone.

[0097] Example 4

[0098] 3 g of silica (average particle size: 5 pm) was pre-heated at 600 °C in air for 2 hours. The pre-heated silica was mixed with 10 g of urea, and the mixture was heated at 300 °C in air for

[0099] 4 hours and then 600 °C in air for 2 hours to produce the mixture of graphitic carbon nitride and silica.

[0100] Comparative Example 3

[0101] 10 g of urea was heated at 300 °C in air for 4 hours and then 600 °C in air for 2 hours to produce the graphitic carbon nitride alone.

[0102] [Evaluation]

[0103] The following evaluations were conducted on the obtained powder samples.

[0104] (Yield)

[0105] Yield of the obtained graphitic carbon nitride was calculated in each of the processes by measuring the weight of the products.

[0106] (Morphology Analysis)

[0107] The IR spectrum of the produced powder was obtained using attenuated total reflection (ATR) method. The peak assigned to heptazine units appears at 804 cm’1, which is higher wavenumber than those of triazine units (814 cm’1for melamine, 808 cm’1for melam), according to Nan Liu et al (ACS Omega, 2020, 5, 12557-12567).

[0108] Figure 1 shows IR spectra of the products according to Example 4 and Comparative Example 3. The spectra of the product according to Example 1 exhibits a peak derived from the structure of graphitic carbon nitride and silica.

[0109] Also, according to the morphology analysis, it was confirmed that all of the graphitic carbon nitrides produced in the examples include heptazine units. (UV Absorption / Diffuse Transmittance Property)

[0110] The performance of light absorption of the powder samples in the wavelength range of ultraviolet light and visible light was evaluated using ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy (UV2500PC, Shimadzu Corporation) coupled with an integrating sphere.

[0111] The UV-vis absorption spectra of the powder samples suspended in water in Fine quartz cell (two transparent Sides, 2 mm (optical path length) x 10 mm H45 mm, Tokyo Garasu Kikai Co., Ltd.) were collected using UV- Visible spectrophotometer (V750, Jasco Inc.) coupled with an integrating sphere. The suspensions were sonicated using Ultrasonic Cleaner (ASU- 3M, AS ONE Corporation) before the measurement.

[0112] The onset adsorption edge value was estimated from UV-vis diffuse reflectance spectrum of each sample.

[0113] Figure 2 shows a comparison of the UV-vis absorption spectra curve between Example 1 and Comparative Example 1. Example 1 showed a lower onset absorption edge value than Comparative Example 1 , indicating that the obtained powder according to Example 1 exhibits less color than Comparative Example 1.

[0114] Also, Figure 3 shows the UV-vis absorption spectra curve measured with the mixture product according to Example 4 in a form of 0.1% by weight of suspension in water.

[0115] The results are summarized in Table 1 below.

[0116] Table 1

[0117] As can be seen from the results in Table 1, the process according to Examples 1 to 4 could produce the graphitic carbon nitride with a higher yield. Thus, the process according to the present invention could efficiently produce the graphitic carbon nitride. In addition, the produced mixture product according to Example 1 exhibited lower onset absorption edge value than Comparative Example 1, indicating that the mixture product according to Example 1 is less color. The lower onset absorption edge value indicates that the products according to the present invention show enhanced whiteness. Thus, it can be concluded that the process according to the present invention is very useful for manufacturing graphitic carbon nitrides, and the product prepared by the process of the present invention is very useful for various products requiring UV protection, in particular cosmetics, because it can provide keratinous substances with sufficient UV protection without change of color tone.

Claims

CLAIMS1. A process for preparing graphitic carbon nitride comprising a step of heating at least one precursor compound with at least one metal oxide particle.

2. The process according to Claim 1 , wherein the precursor compound is selected from urea, thiourea, melamine, guanidine, arginine, cyanamide, dicyandiamide, and a salt thereof, and combinations thereof.

3. The process according to Claim 1 or 2, wherein the metal oxide particle is selected from silica (SiCh), zeolite, aluminium oxide (AI2O3), and mixtures and composites thereof.

4. The process according to any one of the preceding claims, wherein the metal oxide particle has an average particle size ranging from 0.01 to 30 pm, preferably from 0.05 to 20 pm.

5. The process according to any one of the preceding claims, wherein the weight ratio of the precursor compound and the metal oxide particle ranges 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 in particular from 1 :5 to 5:1.

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

7. The process according to any one of the preceding claims, wherein the heating is carried out in the presence of oxygen-containing species, such as O2, humidity, O3, O atomic and / or ionic oxygen as an oxidizing agent; preferably the oxidizing agent used during the heating step is in a gas form; more preferably the oxygen-containing species is neither from permanganate salt nor from hydrogen peroxide.

8. The process according to any one of the preceding claims, comprising additional preheating step for the precursor compound or the metal oxide particle, or both of the precursor compound and the metal oxide particle.

9. The process according to any one of the preceding claims, wherein the graphitic carbon nitride has a porous structure.

10. A mixture product prepared by the process according to any one of the preceding claims, comprising the graphitic carbon nitride and the metal oxide particle.

11. The mixture product according to Claim 10, wherein the weight ratio of the graphitic carbon nitride and the metal oxide particle ranges 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 in particular from 1 :5 to 5 : 1.

12. The mixture product according to Claims 10 or 11 , having an onset absorption edge value ranging from 390 to 430 nm, preferably from 395 to 420 nm.

13. A use of the mixture product according to Claims 10 or 11 , as a paint active, as apigment, as a filler especially of plastics or as a cosmetic active.

14. A use of the mixture product according to Claim 10 or 11 as a UV absorber.

15. Composition comprising the graphitic carbon nitride according to the preceding claim and water and / or at least one organic media.

16. A composition, preferably a cosmetic composition for keratinous substances, such as skin, comprising the mixture product according to Claim 10 or 11.

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

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