A bio-based carbon quantum dot modified g-C3N4 epoxy-acrylate composite emulsion and preparation method

Abstract

The present invention discloses a bio-based carbon quantum dot-modified g-C3N4 epoxy-acrylate composite emulsion, which is prepared from 50 to 150 parts of epoxy-acrylate emulsion and 10 to 30 parts of bio-based carbon quantum dot-modified g-C3N4 dispersion. The preparation method includes the steps of preparing the epoxy-acrylate emulsion, preparing the bio-based carbon quantum dot-modified g-C3N4 dispersion, and preparing the bio-based carbon quantum dot-modified g-C3N4 epoxy-acrylate composite emulsion. The present invention solves the problems of low epoxy resin content in the prior art epoxy-acrylate emulsion, poor mixed dispersion stability of functional particle / polymer composite emulsion, and poor corrosion resistance of functional particle / polymer composite coating. The modified g-C3N4 and water-based epoxy-acrylate emulsion work together, and fully utilize the high shielding properties of g-C3N4 to improve the corrosion resistance of the coating.

Description

Technical Field

[0001] The present invention relates to the technical field of epoxy-acrylate composite materials, in particular to a bio-based carbon quantum dot modified g-C3N4 epoxy-acrylate composite emulsion and a preparation method thereof. Background Art

[0002] Epoxy-acrylate (EP-acrylate) emulsions combine the advantages of both epoxy and acrylate resins and are currently a research hotspot for waterborne epoxy coatings. However, due to the polymerization inertness of epoxy resins, it is difficult to prepare EP-acrylate emulsions with high epoxy resin content under emulsion polymerization conditions, which greatly restricts their practical application in the field of anti-corrosion coatings.

[0003] Combining functional particles with excellent barrier properties with organic polymers that exhibit superior film-forming properties has become an effective approach to improving the overall performance of existing coatings. In recent years, research has focused on incorporating nano-zinc oxide, nano-titanium dioxide, carbon nanotubes, and graphene into various polymer composite coatings. Graphene coatings, due to their advantages such as thin coating thickness, light film weight, and electrical conductivity, have become a focus of research and development worldwide. However, further research has shown that only a complete graphene layer can block corrosion factors, while defects in the graphene film can even trap chloride ions, accelerating corrosion, thus limiting their practical application.

[0004] Barrier properties and bonding strength are crucial for corrosion resistance and longevity. Carbon-based hybrid materials offer excellent stability, mechanical properties, and corrosion resistance. For example, graphite-like carbon nitride (g-C3N4) is a lamellar carbon-based material with excellent physical barrier properties, preventing the penetration of H2O, O2, and electrolytes. The presence of nitrogen atoms in g-C3N4 reduces its electrical conductivity and thus its galvanic corrosion with the metal substrate. Adding g-C3N4 as a modifier to organic polymers to prepare polymer composite coatings can, on the one hand, address or prevent the common failure of coatings caused by wear defects; on the other hand, it can protect the substrate by blocking corrosion from corrosive agents such as water, oxygen, and chloride ions. However, g-C3N4 has poor compatibility with organic polymers, and directly adding g-C3N4 to epoxy-acrylate emulsions easily leads to aggregation, rendering it ineffective.

[0005] Carbon quantum dots (CQDs) are a new type of nanomaterial. Due to their large number of hydrophilic groups, they have good water solubility and dispersibility, and have the advantage of a simple preparation process. The biomass used to prepare carbon quantum dots (CQDs) is easy to obtain from multiple sources and has minimal environmental pollution. Therefore, compounding biomass carbon quantum dots with g-C3N4 and then adding them to epoxy-acrylate can not only improve the dispersibility of g-C3N4 in the emulsion, but also maximize the shielding properties of the carbon-based hybrid material, providing a new technical solution to address the performance defects of epoxy-acrylate composites. Summary of the Invention

[0006] The purpose of the present invention is to provide a bio-based carbon quantum dot modified g-C3N4 epoxy-acrylate composite emulsion to address the problems of low epoxy resin content in the above-mentioned epoxy-acrylate composite emulsion, low dispersibility of graphite-like carbon nitride in water-based anti-corrosion coatings, poor compatibility and poor anti-corrosion performance. The composite emulsion has the advantages of high epoxy resin content, good dispersion stability of g-C3N4 in the emulsion, good anti-corrosion performance, strong environmental protection and simple preparation process.

[0007] The second object of the present invention is to provide a method for preparing the bio-based carbon quantum dot modified g-C3N4 epoxy-acrylate composite emulsion.

[0008] The above object of the present invention is achieved by the following scheme: a bio-based carbon quantum dot modified g-C3N4 epoxy-acrylate composite emulsion is prepared from the following components in parts by weight:

[0009] 50-150 parts of epoxy-acrylate emulsion;

[0010] 10-30 parts of bio-based carbon quantum dot modified g-C3N4 dispersion.

[0011] The epoxy-acrylate emulsion is prepared by pre-emulsifying and dispersing a mixed monomer containing epoxy resin E-44 with an emulsifier to form a seed mini-emulsion, which is then added dropwise to the acrylate monomer for mini-emulsion polymerization.

[0012] The preparation method of the epoxy-acrylate emulsion comprises the following steps:

[0013] (1) Add 45-112.5 parts of epoxy resin, 50-90 parts of methyl methacrylate, 5-15 parts of butyl acrylate and 1-5 parts of methacrylic acid into a reaction vessel, heat to 50-60° C., and stir evenly to prepare a base material;

[0014] (2) 0.5-1 part of modified polyoxyolefin, 3-6 parts of alkylphenol polyoxyethylene ether ammonium sulfate, 1-4 parts of alkyl diphenyl ether sulfonic acid disodium salt, and 200-300 parts of deionized water are mixed and stirred uniformly to prepare an emulsifier solution; the emulsifier solution is added dropwise to the base material, and vigorously stirred at 50-60° C. for 15-35 minutes to prepare an E-44 monomer miniemulsion;

[0015] (3) Dissolve 2-8 parts of sodium bicarbonate and 0.5-2 parts of initiator in 120-180 parts of deionized water, mix well, add to the E-44 monomer miniemulsion, and heat to 78-80° C. with stirring to obtain the first batch;

[0016] (4) taking 80-130 parts of methyl methacrylate, 120-180 parts of butyl acrylate, 2-6 parts of methacrylic acid, and 3-10 parts of diacetone acrylamide (DAAM), and stirring them uniformly to prepare a first mixed monomer;

[0017] (5) After the first kettle material is heated to 78-82° C., the first mixed monomer in step (4) is uniformly added dropwise within 3-4 hours, and at the same time, an initiator solution prepared by mixing 0.5-2 parts of initiator, 1-2 parts of alkylphenol polyoxyethylene ether ammonium sulfate, 1-4 parts of alkylphenol polyoxyethylene ether and 50-70 parts of deionized water is added dropwise within 3.5-4.5 hours; after the initiator solution is added dropwise, the mixture is kept warm for 15-20 minutes, heated to 80-90° C. and kept warm for 10-20 minutes, and the epoxy-acrylate emulsion is obtained by discharging the material.

[0018] Preferably, the modified polyoxyolefin can be Disponil LS 500 produced by BASF of Germany.

[0019] (DLS500).

[0020] Preferably, the alkylphenol polyoxyethylene ether ammonium sulfate can be an emulsifier with model number CO-436.

[0021] Preferably, the disodium salt of alkyl diphenyl ether sulfonate can be sodium dodecyl diphenyl ether disulfonate, model number DSB.

[0022] Preferably, the alkylphenol polyoxyethylene ether may be an emulsifier with a model number of OP-10.

[0023] Preferably, the initiator is potassium persulfate or ammonium persulfate.

[0024] Preferably, the mass ratio of the epoxy resin, methyl methacrylate, butyl acrylate and methacrylic acid in step (1) is 1:0.83:0.14:0.03.

[0025] Preferably, the mass ratio of methyl methacrylate, butyl acrylate, methacrylic acid and diacetone acrylamide (DAAM) in step (4) is 1:1.36:0.04:0.05.

[0026] Preferably, in the step (5), the first kettle material is heated to 80° C., the first mixed monomer is started to be added dropwise, and the addition is completed in 4 hours. After the first mixed monomer is added dropwise for 0.5 hours, the aqueous solution is started to be added dropwise, and the addition is completed in 4.5 hours. After the addition is completed, the reaction is kept warm for 20 minutes, and then the temperature is raised to 85° C. and the reaction is carried out for 15 minutes to obtain the epoxy-acrylate emulsion.

[0027] The bio-based carbon quantum dot modified C3N4 uses pollen as a raw material, uses a microwave method to prepare a bio-based carbon quantum dot solution, and uses a melamine (C3H6N6) urea and other calcination methods to prepare C3N4.

[0028] The preparation method of the bio-based carbon quantum dot modified C3N4 comprises the following steps:

[0029] (1) According to the following ratio, weigh 1g of pollen, add 0.3-1.5mL of passivating agent and 5-20mL of deionized water, stir evenly, and microwave in a 700-900W microwave oven for 2-10min to obtain a brown-red solid; dissolve the brown-red solid in 10-30mL of deionized water, and centrifuge at a speed of 8000-9000r / min for 5-10 minutes; the filtrate obtained after filtration is the first bio-based carbon quantum dot solution;

[0030] (2) Weigh 5-30 g of melamine, heat it to 480-560 ° C at a rate of 12 ° C / min, and calcine it in a muffle furnace for 4 hours. Then, after cooling, a large piece of light yellow solid is obtained, which is crushed to obtain g-C3N4;

[0031] (3) Take 20 mL of the first bio-based carbon quantum dot solution, add 0.05 g of g-C3N4, and then ultrasonicate it with 200-400 W ultrasound for 2 h and stir it at room temperature for 24 h to prepare a bio-based carbon quantum dot-modified g-C3N4 dispersion.

[0032] Preferably, the pollen is camellia pollen or pine pollen.

[0033] Preferably, the passivating agent is ethylenediamine or o-phenylenediamine.

[0034] The preparation method of the bio-based carbon quantum dot modified g-C3N4 epoxy-acrylate composite emulsion comprises the following steps: mixing the bio-based carbon quantum dot modified g-C3N4 dispersion with the epoxy-acrylate emulsion, and stirring them evenly to obtain the bio-based carbon quantum dot modified g-C3N4 epoxy-acrylate composite emulsion.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. Through miniemulsion polymerization, epoxy resin is hybridized in acrylate emulsion polymerization to increase the epoxy resin content in the epoxy-acrylate emulsion. The process is simple and easy to operate. The epoxy part of this hybrid emulsion can react with the water-based amine curing agent during film formation to form the continuous phase of the coating. The macromolecular acrylate latex particles are dispersed in the cross-linked network to form a dense coating film, which improves the barrier and mechanical properties of the coating.

[0037] 2. The modification of g-C3N4 by bio-based carbon quantum dots improves the dispersibility of g-C3N4 in epoxy-acrylate emulsion (such as Figure 4 、 Figure 5 As shown in the figure, after modification with carbon quantum dots, the agglomeration of g-C3N4 was significantly weakened, the average particle size of g-C3N4 was reduced from 3375nm to 125nm, the polydispersity was also reduced, and it could be evenly dispersed in the emulsion), thus enhancing the interfacial interaction between the carbon material and the polymer;

[0038] 3. The modified g-C3N4 is uniformly dispersed in the epoxy cross-linked network, maximizing the high shielding properties of the carbon material, enhancing the wear resistance of the coating, and at the same time blocking corrosion factors such as water, oxygen and chloride ions to protect the substrate; Tables 2 and 3 show the water resistance and alkali resistance test results of different emulsion films. It can be seen that the water resistance and alkali resistance of the composite coating of g-C3N4 and epoxy-acrylate are significantly improved after modification with bio-based carbon quantum dots.

[0039] 4. After compounding biomass carbon quantum dots with g-C3N4 and adding them to epoxy-acrylate, it can not only improve the dispersibility of g-C3N4 in the emulsion, but also maximize the shielding performance of carbon-based hybrid materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is the particle size distribution diagram of epoxy-acrylate emulsion with different E-44 contents;

[0041] Figure 2 This is the infrared spectrum of bio-based carbon quantum dots prepared by microwave method;

[0042] Figure 3 is the X-ray diffraction pattern of graphite phase carbon nitride;

[0043] Figure 4 DLS graph of bio-based carbon quantum dots modified g-C3N4 dispersed in water.

[0044] Figure 5 This is the dispersion film formation diagram of g-C3N4 and g-C3N4 / N-CQDs in emulsion. DETAILED DESCRIPTION

[0045] The present invention will be further described below with reference to the following embodiments. The following description is merely a preferred embodiment of the present invention and does not limit the present invention in any other form. Any person skilled in the art may utilize the above disclosed technical content to make equivalent embodiments with equivalent variations. Any simple modification or equivalent variation of the following embodiments made in accordance with the technical essence of the present invention without departing from the content of the present invention shall fall within the scope of protection of the present invention.

[0046] The present invention uses a miniemulsion hybrid polymerization method and a microwave method to prepare a bio-based carbon quantum dot modified g-C3N4 epoxy-acrylate composite emulsion, which is mainly prepared by the following steps:

[0047] (1) Preparation of epoxy-acrylate emulsion: Add the base material to a four-necked flask equipped with a stirrer, a reflux condenser, and a thermometer, heat to 55°C, stir evenly, then drop the emulsifier solution into the base material, vigorously stir and emulsify at 55°C for 30 minutes to form an E-44 monomer miniemulsion; then add the initial initiator solution in sequence, continue to heat to 80°C, start to drop the first mixed monomer, and finish it in 4 hours, start to drop the second initiator solution 0.5 hours after the monomers are added, and finish it in 4.5 hours, keep the temperature for reaction for 0.5 hours after the addition, then heat to 85°C for reaction for 0.5 hours, and then discharge the material to obtain epoxy-acrylate emulsion;

[0048] (2) Synthesis of bio-based carbon quantum dots (N-CQDs): Weigh 1 g of camellia pollen sample, add 0.8 mL of ethylenediamine, and then add 10 mL of deionized water; stir evenly and microwave in a microwave oven at 800 W for 7 minutes. After the microwave is finished, dissolve the brown-red solid in 20 mL of deionized water and centrifuge at 8500 r / min for 7 minutes; the filtrate obtained after filtration is the bio-based carbon quantum dot solution;

[0049] (3) Preparation of graphite phase g-C3N4: Melamine (C3H6N6) was weighed and calcined in a muffle furnace at 520°C for 4 hours at a heating rate of 12°C / min. After cooling, a large piece of light yellow solid was obtained, which was crushed to obtain g-C3N4.

[0050] (4) Modification of graphite phase g-C3N4: Take 20 mL of N-CQDs solution, add 0.05 g of prepared g-C3N4, and then ultrasonicate for 2 h and stir at room temperature for 24 h; then filter the dispersion through a nylon membrane under continuous stirring; after filtration, transfer it into a beaker to obtain a carbon quantum dot-modified g-C3N4 dispersion.

[0051] Example 1

[0052] The preparation method of epoxy-acrylate emulsion comprises the following steps:

[0053] (1) In a four-necked flask, 90 g of epoxy resin, 75 g of methyl methacrylate, 12.5 g of butyl acrylate, and 2.5 g of methacrylic acid were weighed, heated to 55° C., and stirred to obtain a base material;

[0054] (2) Weigh 0.75 g of modified polyoxyolefin DLS500, 4 g of alkylphenol polyoxyethylene ether ammonium sulfate, 2 g of sodium dodecyl diphenyl ether disulfonate, and 225 g of deionized water, and stir them evenly to obtain an emulsifier solution; after stirring the emulsifier solution evenly, add it dropwise to the above-mentioned base material, and stir at 55° C. and 1600 r / min for 30 min to obtain an E-44 monomer miniemulsion;

[0055] (3) Dissolve 2.8 g of sodium bicarbonate and 1 g of initiator KPS in 125 g of deionized water, mix well, add to the above-mentioned E-44 monomer miniemulsion, and heat to 80° C. with stirring to obtain the first batch;

[0056] (4) Weighing 110 g of methyl methacrylate, 150 g of butyl acrylate, 4 g of methacrylic acid, and 6 g of diacetone acrylamide and stirring them evenly to obtain a first mixed monomer;

[0057] (5) After the first kettle material is heated to 80° C., the first mixed monomer in step (4) is uniformly added dropwise within 4 hours, and at the same time, an initiator solution prepared by 1 g of ammonium persulfate, 1.36 g of CO-436, 1 g of OP-10 and 66 g of deionized water is added dropwise within 4.5 hours; after the initiator solution is added dropwise, the mixture is kept warm for 16 minutes, and then the temperature is raised to 85° C. and kept warm for 12 minutes, and the epoxy-acrylate emulsion is obtained by discharging the material.

[0058] Comparison sample 2

[0059] Comparative Sample 2 was prepared by adding the kettle material according to the recipe in Table 2 below to a four-necked flask equipped with a stirrer, condenser, thermometer, and constant pressure funnel. The mixture was rapidly stirred in an 80°C water bath until the bottom temperature reached 80°C. The initial initiator was then added, and the temperature returned to 80°C. The seed monomer was then added dropwise to the bottom over 16 minutes. After a 10-minute incubation, the core monomer and core initiator were added dropwise simultaneously. After 4-4.5 hours, the incubation was continued for 15 minutes. The shell monomer and shell initiator were then added dropwise simultaneously over 2-2.5 hours. The mixture was then incubated for 30 minutes before being discharged.

[0060] Regardless of whether the epoxy resin is in the core layer and the methacrylic acid is in the shell layer, or the methacrylic acid is in the core layer and the epoxy resin is in the shell layer, when the epoxy resin content exceeds 8% (of the total monomer content), the gel content of the composite emulsion is as high as 2% (of the total emulsion content).

[0061] Table 2 is the formula of comparative sample 2

[0062]

[0063] Comparison sample 3

[0064] Comparative sample 3 was placed in a four-necked flask with an agitator, a condenser, a thermometer and a constant pressure funnel. A certain amount of kettle material was added according to the formula in Table 3 below, and the mixture was rapidly stirred in a water bath at 80°C until the bottom material temperature rose to 80°C. The initial initiator was added and the temperature returned to 80°C; the seed monomer was added dropwise to the bottom material within 18 minutes; after keeping warm for 10 minutes, the core monomer and initiator were started to be added dropwise at the same time, and the dripping was completed in about 3 hours, and the mixture was kept warm for 30 minutes; the transition monomer and the remaining initiator were started to be added dropwise at the same time, and the dripping was completed in 30 minutes, and the mixture was kept warm for 10 minutes; the shell monomer and initiator were started to be added dropwise at the same time, and the dripping was completed in 2 hours, and the mixture was kept warm for 30 minutes before discharging; when the modified epoxy resin content was as high as 12% (of the total solids), the gel content of the composite emulsion was 3% (of the total emulsion amount).

[0065] Table 3 is the formula table of comparative sample 3

[0066]

[0067] The particle size and stability of the epoxy-acrylate emulsion prepared above were tested, and the results were as follows Figure 1 As shown in Table 1 below, Figure 1 Curve 1 is an E-44 content of 15% with an average particle size of 72.91 nm; Curve 2 is an E-44 content of 25% with an average particle size of 127.38 nm; Curve 3 is an E-44 content of 20% with an average particle size of 89.35 nm.

[0068] Table 1 Storage stability of different epoxy-acrylate emulsions

[0069]

[0070]

[0071] From the above charts and comparative tests, it can be seen that the miniemulsion hybrid polymerization method greatly increases the epoxy resin content but does not affect the latex particle size and stability.

[0072] Example 2

[0073] The preparation method of bio-based carbon quantum dot modified C3N4, the steps are as follows:

[0074] (1) Weigh 1 g of camellia pollen, add 0.8 mL of ethylenediamine, and then add 10 mL of deionized water. After stirring evenly, microwave it in a microwave oven at 800 W for 7 minutes. After the microwave is finished, the brown-red solid is dissolved in 20 mL of deionized water and centrifuged at 8500 r / min for 7 minutes. The filtrate obtained after filtration is the bio-based carbon quantum dot solution. Its structure is detected by infrared spectroscopy, as shown in the attached figure. Figure 2 As shown;

[0075] (2) Weigh 10 g of melamine (C3H6N6) and calcine it in a muffle furnace at 520°C for 4 hours at a heating rate of 12°C / min. After cooling, a large piece of light yellow solid was obtained, which was crushed to obtain g-C3N4. The structure of the solid was detected by XRD, as shown in the attached figure. Figure 3 As shown in the figure, it can be seen that the product is g-C3N4.

[0076] (3) Take 20mL of N-CQDs aqueous dispersion, add 0.05g of prepared g-C3N4, and then ultrasonicate it at 300W for 2h and stir it at room temperature for 24h; then filter the dispersion through a nylon membrane under continuous stirring, and transfer it into a beaker to obtain a carbon quantum dot modified g-C3N4 dispersion. The dispersion stability was tested, as shown in the attached figure. Figure 4 As shown in the figure, it can be seen that after modification with carbon quantum dots, the agglomeration of g-C3N4 is significantly weakened, the dispersion in water is improved, the particle size is greatly reduced, and the polydispersity is also reduced.

[0077] The preparation method of bio-based carbon quantum dot modified g-C3N4 epoxy-acrylate composite emulsion includes the following steps: mixing 11 parts of the carbon quantum dot modified g-C3N4 dispersion prepared above with 110 parts of epoxy-acrylate emulsion, and stirring evenly to obtain the bio-based carbon quantum dot modified g-C3N4 epoxy-acrylate composite emulsion.

[0078] The film formation and corrosion resistance of the film were tested. Figure 5 As shown in Tables 4 and 5 (the mass ratio of carbon quantum dot-modified g-C3N4 to epoxy-acrylate emulsion is 1:10), it can be seen that the agglomeration of g-C3N4 is significantly reduced after modification with carbon quantum dots, and it is well dispersed in the emulsion. The water resistance and alkali resistance of the composite coating are also improved.

[0079] Figure 2 This is the infrared spectrum of bio-based carbon quantum dots prepared by microwave method. NH stretching vibration peaks appear between 3750 and 3600 cm-1, free OH stretching vibration peaks appear at 3648.23 cm-1, CH stretching vibration peaks on unsaturated carbon and symmetric CH2 stretching vibration peaks appear at 3294.42 cm-1 and 2927.03 cm-1, C=O and C=C stretching vibration peaks appear between 1750 and 1500 cm-1, -C=N stretching vibration peak appears at 1455.2 cm-1, and CN stretching vibration peak appears at 1066.1 cm-1. The inclusion of NH stretching vibration in the microwave infrared spectrum indicates that ethylenediamine not only acts as a passivating agent in the microwave method but also adds more nitrogen to the system.

[0080] Figure 3 This is the XRD spectrum of graphite phase carbon nitride particles. There are two obvious peaks in the spectrum, 13.0° and 27.4°, which are consistent with the standard spectrum of g-C3N4. Figure 1 To.

[0081] Figure 4 The DLS images of g-C3N4 dispersion in water before and after modification show that after modification with carbon quantum dots, the agglomeration of g-C3N4 is significantly reduced, the dispersion in water is improved, the particle size is greatly reduced, and the polydispersity is also reduced.

[0082] Figure 5 The figure shows the film formation of g-C3N4 mixed with epoxy-acrylate emulsion before and after modification with bio-based carbon quantum dots (the left side is after modification, and the right side is unmodified). It can be seen that after modification with bio-based carbon quantum dots, g-C3N4 is well dispersed in the epoxy-acrylate emulsion, while there is obvious agglomeration before modification.

[0083] Tables 4 and 5 below show the water and alkali resistance test results of g-C3N4 and epoxy-acrylate composite emulsion films, both pure and before and after modification with bio-based carbon quantum dots. As can be seen, the water and alkali resistance of the g-C3N4 and epoxy-acrylate composite coatings were significantly improved after modification with bio-based carbon quantum dots.

[0084] Table 4 Water resistance test results of pure emulsion, g-C3N4 mixed emulsion, and g-C3N4 hybrid material composite emulsion

[0085]

[0086]

[0087] Table 5 Alkali resistance test results of pure emulsion, g-C3N4 mixed emulsion, and g-C3N4 hybrid material composite emulsion

[0088]

[0089] The above is only a preferred embodiment of the present invention and should not be used to limit the scope of implementation of the present invention. In other words, any simple equivalent changes and modifications made according to the scope of protection of the present invention and the content of the invention description are still within the scope of the patent of the present invention.

Claims

1. A bio-based carbon quantum dot modified g-C3N4 epoxy-acrylate composite emulsion, characterized by: Prepared from the following components in parts by weight: 50-150 parts of epoxy-acrylate emulsion; 10-30 parts of bio-based carbon quantum dot modified g-C3N4 dispersion; The preparation method of the epoxy-acrylate emulsion comprises the following steps: (1) Add 45-112.5 parts of epoxy resin, 50-90 parts of methyl methacrylate, 5-15 parts of butyl acrylate and 1-5 parts of methacrylic acid into a reaction vessel, heat to 50-60°C, and stir evenly to prepare a base material; (2) Take 0.5-1 parts of modified polyoxyolefin, 3-6 parts of alkylphenol polyoxyethylene ether ammonium sulfate, 1-4 parts of alkyl diphenyl ether sulfonic acid disodium salt and 200-300 parts of deionized water, mix and stir evenly to prepare an emulsifier solution; add the emulsifier solution dropwise to the base material, stir vigorously at 50-60°C for 15-35 minutes to prepare E-44 monomer miniemulsion; (3) Dissolve 2-8 parts of sodium bicarbonate and 0.5-2 parts of initiator in 120-180 parts of deionized water, mix well, add to the E-44 monomer miniemulsion, and heat to 78-80°C with stirring to obtain the first batch; (4) 80-130 parts of methyl methacrylate, 120-180 parts of butyl acrylate, 2-6 parts of methacrylic acid and 3-10 parts of diacetone acrylamide are mixed and stirred to prepare a first mixed monomer; (5) After heating the first kettle material to 78-82°C, uniformly add the first mixed monomer in step (4) dropwise within 3-4 hours, and at the same time, add dropwise within 3.5-4.5 hours an initiator solution prepared by mixing 0.5-2 parts of initiator, 1-2 parts of alkylphenol polyoxyethylene ether ammonium sulfate, 1-4 parts of alkylphenol polyoxyethylene ether and 50-70 parts of deionized water; after the initiator solution is added, keep the temperature for 15-20 minutes, heat to 80-90°C and keep the temperature for 10-20 minutes; The preparation method of the bio-based carbon quantum dot modified g-C3N4 dispersion comprises the following steps: (1) According to the following ratio, weigh 1 g of pollen, add 0.3-1.5 mL of passivating agent and 5-20 mL of deionized water, stir evenly, and microwave in a microwave oven at 700-900 W for 2-10 min to obtain a brown-red solid; dissolve the brown-red solid in 10-30 mL of deionized water and centrifuge at 8000-9000 r / min for 5-10 minutes; the filtrate obtained after filtration is the first bio-based carbon quantum dot solution; (2) Weigh 5-30 g of melamine, heat it to 480-560 °C at a rate of 12 °C / min, and calcine it in a muffle furnace for 4 hours. Then, after cooling, a large piece of light yellow solid is obtained, which is crushed to obtain g-C3N4; (3) Take 20 mL of the first bio-based carbon quantum dot solution, add 0.05 g of g-C3N4, and then ultrasonicate.

2. The bio-based carbon quantum dot modified g-C3N4 epoxy-acrylate composite emulsion according to claim 1, characterized in that: The modified polyoxyolefin is Disponil LS 500 from BASF of Germany; the disodium salt of alkyl diphenyl ether sulfonate is sodium dodecyl diphenyl ether disulfonate; the alkylphenol polyoxyethylene ether is OP-10; and the initiator is potassium persulfate or ammonium persulfate.

3. The bio-based carbon quantum dot modified g-C3N4 epoxy-acrylate composite emulsion according to claim 1, characterized in that: The mass ratio of the epoxy resin, methyl methacrylate, butyl acrylate and methacrylic acid in step (1) is 1:0.83:0.14:0.

03.

4. The bio-based carbon quantum dot modified g-C3N4 epoxy-acrylate composite emulsion according to claim 1, characterized in that: The mass ratio of methyl methacrylate, butyl acrylate, methacrylic acid and diacetone acrylamide in step (4) is 1:1.36:0.04:0.

05.

5. The bio-based carbon quantum dot modified g-C3N4 epoxy-acrylate composite emulsion according to claim 1, characterized in that: In step (5), the first kettle material is heated to 80°C, and the first mixed monomer is added dropwise, and the addition is completed within 4 hours. 0.5 hours after the first mixed monomer is added dropwise, the initiator solution is added dropwise, and the addition is completed within 4.5 hours. After the addition is completed, the mixture is kept warm for reaction for 20 minutes, and then heated to 85°C for reaction for 15 minutes.

6. The bio-based carbon quantum dot modified g-C3N4 epoxy-acrylate composite emulsion according to claim 1, characterized in that: The pollen is camellia pollen or pine pollen; and the passivating agent is ethylenediamine or o-phenylenediamine.

7. The method for preparing the bio-based carbon quantum dot modified g-C3N4 epoxy-acrylate composite emulsion according to any one of claims 1 to 6, characterized in that: The carbon quantum dot-modified g-C3N4 dispersion prepared above was mixed with the epoxy-acrylate emulsion and stirred evenly.

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