Preparation Method of Flame-Retardant, High-Refractive-Index, Melting-Drip-Resistant Acrylate Resin Coating

Abstract

The present invention relates to a preparation method of a flame-retardant, high-refractive-index, melt-drop-resistant water-based acrylate resin coating. Water, an emulsifier, and methacrylic acid are added to a reaction vessel and stirred for reaction, and then monomer A, DOPO, and N-vinylcarbazole are added; the temperature is raised to 75-85 °C, an initiator is added dropwise, and the reaction is carried out for 1-2 h to obtain a core-layer emulsion; at the same time, all of monomer B and the initiator are added dropwise, and the reaction is stirred for 1-2 h, then DOPO is added, the temperature is lowered to 50 °C, emulsifier B is added, the reaction time is 30-60 min, then N-vinylcarbazole is added, and the reaction is carried out for 0.25-0.5 h. Then, an ammonium polyphosphate solution, aluminum sulfate, and a chitosan / gelatin composite microsphere are added, and high-speed shear emulsification is carried out, and the pH value is adjusted to 7-8 to obtain a flame-retardant, high-refractive-index, melt-drop-resistant water-based acrylate resin coating; the obtained acrylate resin coating has the advantages of a high oxygen index, no melt dripping during combustion, and a high film refractive index.

Description

Technical Field

[0001] The present invention relates to a preparation method of a waterborne acrylate resin coating, and particularly to a preparation method of a flame-retardant, high-refractive-index, and melt-drop-resistant waterborne acrylate resin coating. Background Art

[0002] In recent years, intelligent optoelectronic devices such as flexible displays and micro sensors have been in a rapid development stage. High-performance optical materials are the basis for realizing the functions of advanced optical devices. Although traditional inorganic optical materials have advantages such as high strength, high refractive index, and low dispersion, their disadvantages of high brittleness, large weight, and high processing difficulty limit their application in advanced optical devices. Organic optical materials have become the preferred materials for advanced optical devices due to their advantages such as adjustable properties, light texture, and easy processing, and are applied in fields such as high-performance substrates, encapsulation materials for light-emitting diodes (LEDs), and microlenses for charge-coupled devices (CCDs) or complementary metal-oxide-semiconductor (CMOS) image sensors. However, compared with inorganic optical materials, the molecular structure characteristics of organic optical materials result in poor thermal stability and low refractive index. Among them, the refractive index is the most critical parameter of organic optical materials, and the disadvantage of low refractive index hinders the progress of high-precision optical devices.

[0003] Yunhui Tang et al. synthesized three acrylate monomers (M-1, M-2, and M-3) containing different chemical structures (fluorene group, thiadiazole group, and diphenyl sulfide group) by a simple one-step method, and prepared acrylate polymers P-1, P-2, and P-3 by free radical melt polymerization. Their thermal stability is higher than 250 °C, and the refractive indices are 1.62, 1.61, and 1.64 (550 nm) respectively. The light transmittance at a wavelength of 450 nm exceeds 90%. However, the P-2 film is light yellow, which comes from the regular arrangement of molecular chains caused by polar thiadiazole and the aggregation of chromophores, resulting in color and reduced light transmittance, and there is no waterborne acrylate resin emulsion used in organic optical materials.

[0004] The invention patent CN111303478A relates to a material for a naked-eye 3D display screen and a preparation method thereof. The method includes the following steps: providing a polymer solution in which a matrix material is dissolved in a volatile solvent, where the matrix material is an optically transparent material and the volatile solvent is not miscible with water; in a constant-temperature and constant-humidity closed container, casting the polymer solution on an optically transparent substrate, and promoting the nucleation and growth of water droplets on the surface of the polymer solution through the volatilization of the volatile solvent; leaving the optically transparent substrate cast with the polymer solution to stand in the constant-temperature and constant-humidity closed container. After the volatile solvent and water droplets are completely volatilized, a microscopic structure of spherical pits left by the water droplets is formed on the surface of the matrix material, thus obtaining the material for the naked-eye 3D display screen. The resin materials used are mainly styrene-butadiene-styrene block copolymer, polycarbonate, polyethyleneimine or polymethyl methacrylate, and their light transmittance is lower than 95%. This invention patent does not emphasize flame retardancy and melt dripping resistance in terms of heat resistance, and uses pure methyl methacrylate as a monomer without using composite acrylate monomers either.

[0005] Regarding flame retardancy, relevant research reports that the invention patent CN118931301A relates to a preparation method of a flame-retardant, washable, and moderately compatible waterborne acrylate resin coating. Add water, an emulsifier, and methacrylic acid, stir and react for 60 min, then add monomer A, a charring agent intermediate, DOPO, and 3,4-epoxy-1-butene, and emulsify for 20 - 30 min; heat up to 80 - 90 °C, dropwise add an initiator, react for 1 - 2 h, then add diethanolamine and react for 1 - 2 h to obtain a core layer emulsion; simultaneously dropwise add monomer B and an initiator, keep the temperature at 75 - 85 °C and stir and react for 1.5 h, then add DOPO, 3,4-epoxy-1-butene, and an initiator, react at 60 - 70 °C for 1 h, cool down to 50 °C, add emulsifier B, react for 30 min, and adjust the pH value to 7 - 8 with ammonia water to obtain a flame-retardant, washable, and moderately compatible waterborne acrylate resin coating. The obtained acrylate resin has good flame retardancy and washability. This invention patent has good flame retardancy, but does not involve high refraction, and the acrylate resin does not characterize the flame retardant oxygen index, and there is still room for improvement in pkHHR. Since electrical components release a large amount of heat after long-term use, resulting in a decrease in their refractive index and flame retardancy, it is necessary to continue to improve.

[0006] Currently, when acrylate resins are used in optical materials, there are problems such as low refractive index and area shrinkage after curing, resulting in the need to re-coat the film. Moreover, optical instruments release a large amount of heat after long-term use, and it is necessary to consider flame retardancy and melt dripping indicators. Therefore, it is imperative to develop acrylate resin materials with high refractive index. Summary of the Invention

[0007] The present invention aims to solve the problems that acrylate resins have a low oxygen index when burning, produce molten droplets and smoke during combustion, and also solve the defect of low refractive index of acrylate resins. In addition, since the acrylate resin is used at high temperature first and then at room temperature during the film-forming process, due to the influence of the traditional principle of thermal expansion and contraction, part of the film area shrinks during cooling, affecting the surface smoothness. Based on this, phosphorus trichloride is used to enhance the acidity in the heating environment, making the carbon layer formed by carbon nanotubes more dense. Bis(2-ethylhexanoic acid) hydroxyaluminum enhances the density of the carbon layer of carbon nanotubes, reduces the molten droplets of acrylate resins, and the alumina generated by its heating and combustion has good thermal conductivity, improving the flame retardancy of carbon nanotubes and the flame retardancy of acrylate resins. 2-Mercapto-1,3,4-thiadiazole is selected. It is a heterocyclic compound containing nitrogen and sulfur. It reacts with acryloyl chloride to obtain an acrylic monomer containing double bonds and nitrogen and sulfur on the main chain. Then it is introduced into the chain segment of acrylate resin. The refractive index group-modified acrylic monomer is used in the core layer and shell layer of acrylate resin, improving the overall refractive index of acrylate resin. At the same time, taking advantage of the fact that the shrinkage rate of microspheres decreases slightly under dry conditions, the decrease amplitude of the acrylate resin film at room temperature is reduced, facilitating industrial production.

[0008] A preparation method of a flame-retardant, high-refractive-index, and molten-droplet-resistant acrylate resin coating is prepared according to the following steps:

[0009] (1) Prepare the core layer emulsion: Add 500-700 g of water, 13-19 g of emulsifier A, and 25-45 g of methacrylic acid to a reaction vessel, mix and stir evenly, heat up to 50-55 °C, stir and react for 30-60 min, then add monomer A, 13.4-14.5 g of DOPO, and 0.4-0.6 g of N-vinylcarbazole, and emulsify for 30-40 min; heat up to 65 °C and reflux water, heat up to 75-85 °C, dropwise add 12-14 g of initiator, the dropping time is 0.5-1.5 h, and react for 1-2 h to obtain the core layer emulsion;

[0010] (2) While simultaneously dropping monomer B and 10 - 14 g of initiator into the core layer emulsion obtained in step (1), the dropping time is 1 - 1.5 h, keep the temperature at 70 - 85 °C and stir for reaction for 1 - 2 h, then add 6.9 - 12.2 g of DOPO, react at 70 - 80 °C for 1 - 2 h, cool down to 50 °C, add 14 - 21 g of emulsifier B, react for 30 - 60 min, then add 0.5 - 0.6 g of N-vinylcarbazole, react for 0.25 - 0.5 h, then add 14.2 g of ammonium polyphosphate solution dissolved in 10 g of water, 0.5 - 1.3 g of aluminum sulfate, 0.1 - 0.2 g of ammonium molybdate and 0.5 - 0.8 g of chitosan / gelatin composite microspheres, under the rotation speed of 1000 - 2000 r / min, carry out high-speed shear emulsification for 0.5 - 1 h, wait for the foam to disappear, add ammonia water to adjust the pH value to 7 - 8, to obtain a flame-retardant, high refractive index and melt-drop resistant acrylic resin coating;

[0011] The monomer A is composed of 20 - 35 g of ethyl acrylate, 22 - 38 g of methyl methacrylate, 18 - 32 g of 2-hydroxyethyl acrylate, 6 - 12 g of amino-functionalized carbon nanotubes and 3.4 - 6.2 g of high refractive index material;

[0012] The monomer B is composed of 8 - 14 g of amino-functionalized carbon nanotubes, 12 - 54 g of methyl methacrylate, 55 - 92 g of 2-hydroxyethyl acrylate and 3.2 - 5.8 g of high refractive index material.

[0013] The emulsifier A is composed of sodium dodecyl benzene sulfonate and AEO-9 mixed according to the mass ratio of 2.5:1.

[0014] The preparation method of the amino-functionalized carbon nanotubes is as follows:

[0015] 0.7 g of carbon nanotubes are ultrasonically dispersed for 2 - 3 h under the action of 100 mL of concentrated sulfuric acid and concentrated nitric acid with a volume ratio of 3:1 - 4:1. After ultrasonic treatment, the carbon nanotube solution is diluted with 100 mL of water, the acid solution is filtered by a vacuum pump and washed with deionized water until neutral, and dried overnight at 100 - 105 °C to obtain carboxylated carbon nanotubes; then 3.6 g of phosphorus trichloride is dissolved in 10 mL of DMF solution, add 0.2 - 0.4 g of carboxylated carbon nanotubes and 4.5 - 4.7 g of bis(2-ethylhexanoic acid)hydroxyaluminum, react at 50 - 60 °C for 30 - 60 min, then place it in a constant temperature oil bath at 70 - 80 °C, add 7.7 - 9.4 g of acrylamide and react for 2 - 4 h, wash it clean with 10 mL of DMF and 30 mL of toluene in turn, filter and vacuum dry overnight at 100 - 105 °C to obtain amino-functionalized carbon nanotubes.

[0016] The initiator is any one of ammonium persulfate and potassium persulfate.

[0017] The preparation method of the high refractive index material is as follows: Under a nitrogen atmosphere, 7.3 g of dimercaptothiadiazole is uniformly dissolved in 40 mL of anhydrous dichloromethane, 22 mL of triethylamine and 2.2 - 2.9 g of phthalic anhydride are added, and the mixture is stirred at -5°C for 0.5 - 1 h. Then, 20 mL of a mixed solution of acryloyl chloride and dichloromethane with a volume ratio of 1:1 is slowly added drop by drop using a dropping funnel, and the reaction is carried out at room temperature for 24 h. Next, the solution is extracted 2 - 3 times with a 10% HCl aqueous solution to neutralize the excess triethylamine, and then extracted 2 - 3 times with a saturated sodium chloride aqueous solution to obtain the high refractive index material.

[0018] The emulsifier B described above is AEO-9.

[0019] The preparation method of the chitosan / gelatin composite microspheres:

[0020] (1) Dissolve 5 - 6 g of chitosan in 50 mL of a 4% acetic acid aqueous solution by mass, and dissolve 3 - 4 g of gelatin in 40 mL of deionized water at 55°C. Then, mix the chitosan aqueous solution and the gelatin aqueous solution to form a chitosan / gelatin mixed solution;

[0021] (2) Add 30 mL of paraffin and 5 g of span80 to a three-necked flask, heat to 50 - 60°C, stir for 15 - 30 min, and slowly drip the chitosan / gelatin mixed solution in step (1) into the three-necked flask using a separatory funnel. The dripping time is 15 min, and emulsification is carried out at 60 - 70°C for 30 - 40 min. After the emulsification is completed, quickly cool down to 20°C, and add 1 mL of 50% glutaraldehyde by mass percentage, and cure for 0.5 - 1 h. After the curing is completed, centrifuge with a high-speed centrifuge and collect the composite microspheres, wash them with acetone and isopropanol, and then dry them to obtain the chitosan / gelatin composite microspheres.

[0022] The positive effects of the present invention are as follows:

[0023] (1) The present invention constructs a flame-retardant, high-refractive-index, melt-drop-resistant waterborne acrylate resin coating, aiming to solve the problems that acrylate resins have a low oxygen index during combustion and are prone to generate melt drops and smoke when burning, and at the same time make up for the defect of the low refractive index of acrylate resins. Since the acrylate resin is used at high temperature first and then at room temperature during the film-forming process, during this process, the area of the film shrinks partially during cooling, affecting the surface smoothness. Based on this, phosphorus trichloride is used to enhance the acidity in the heating environment, making the carbon layer formed by carbon nanotubes denser, while bis(2-ethylhexanoic acid)aluminum hydroxide plays a role in enhancing the denseness of the carbon layer of carbon nanotubes, reducing the melt drops of acrylate resins, and the alumina generated by its combustion when heated is a good heat-conducting material itself, improving the flame retardancy of carbon nanotubes. DOPO cooperates with N-vinylcarbazole to undergo a free radical reaction, improving the flame retardancy of acrylate resins from the chain segments; DOPO cooperating with N-vinylcarbazole as a charring agent can solve the problem of melt drops generated during the combustion of acrylate films. The oxygen index of the acrylate film is 26%, while when using DOPO cooperating with N-vinylcarbazole and APP for flame retardancy, the oxygen index of the acrylate film can exceed 29%. Among them, aluminum sulfate and ammonium molybdate are complexed with APP, improving the dispersion stability of APP, improving the stability of the acrylate resin emulsion, and at the same time N-vinylcarbazole can also assist in increasing the refractive index of the resin; 2,5-dimercapto-1,3,4-thiadiazole is selected, which is a heterocyclic compound containing nitrogen and sulfur. It reacts with acryloyl chloride to obtain an acrylate monomer containing double bonds and having nitrogen and sulfur on the main chain, and then it is introduced into the chain segments of acrylate resins. The modified acrylate monomer with this refractive group is used in the core layer and shell layer of acrylate resins to increase the refractive index of acrylate resins; at the same time, taking advantage of the characteristic that the shrinkage rate of microspheres decreases little under dry conditions, the decrease amplitude of the acrylate resin film at room temperature is reduced, facilitating industrial production.

[0024] (2) The aminated carbon nanotube modifier introduces a dense carbon layer compound into the molecular chain of acrylamide; the aminated carbon nanotube modifier is obtained by subjecting carbon nanotubes to strong acid oxidation with sulfuric acid and nitric acid, resulting in a large number of hydroxyl and carboxyl groups on the surface of the carbon nanotubes. Since traditional carbon nanotubes are thin and light, when used in waterborne acrylate resin films, they can cause a decrease in melt droplets, but do not significantly increase their oxygen index. Therefore, it is necessary to improve the density of the products during combustion so that the carbon layer can bear the heat impact of combustion in an environment with a high oxygen content. In this invention, phosphorus trichloride reacts with some of the hydroxyl and carboxyl groups in carboxylated carbon nanotubes and aluminum bis(2-ethylhexanoate) hydroxide, introducing an acyl chloride bond into the system, and then reacting with acrylamide to introduce a double bond group into the system. This double bond group can react with acrylic monomers under the action of an initiator to introduce a char-forming part into the molecular chain of acrylate resin. In this reaction, phosphorus trichloride enhances the acidity under a heating environment, making the carbon layer formed by carbon nanotubes denser, while aluminum bis(2-ethylhexanoate) hydroxide enhances the density of the carbon layer of carbon nanotubes, and the alumina generated by its combustion upon heating is a good heat-conducting material itself, improving the flame retardancy of carbon nanotubes and thus the flame retardancy of acrylate resin.

[0025] (3) This invention selects 2,5-dimercapto-1,3,4-thiadiazole, which is a heterocyclic compound containing nitrogen and sulfur. In a basic environment of triethylamine, the hydrogen of the SH group ionizes, causing the acid anhydride of phthalic anhydride to open, and the remaining SH reacts with acryloyl chloride to obtain an acrylic monomer containing a double bond and having nitrogen and sulfur on the main chain. Then, it is introduced into the chain segment of acrylate resin, enabling monomer units with high refraction to be more evenly distributed in the acrylate resin chain segment, increasing the refractive index of the acrylate resin chain segment. At the same time, in order to make the distribution of the refractive monomer units more uniform, the acrylate monomer modified with this refractive group is used in the core layer and shell layer of acrylate resin, improving the overall refractive index of acrylate resin.

[0026] (4) This invention uses a chitosan and gelatin composite system under the curing condition of glutaraldehyde to synthesize chitosan / gelatin composite microspheres. Utilizing the characteristic that the shrinkage rate of the microspheres decreases slightly under dry conditions, it reduces the decrease amplitude of the acrylate resin film at room temperature, facilitating industrial production. Specific embodiments Example 1

[0027] A preparation method of a flame-retardant, high-refraction, and melt-drop-resistant waterborne acrylate resin coating is prepared according to the following steps:

[0028] (1) Preparation of the core layer emulsion: Add 500 g of water, 13 g of emulsifier A (sodium dodecylbenzenesulfonate and AEO-9 in a mass ratio of 2.5:1), and 25 g of methacrylic acid to a reaction vessel. Mix and stir evenly, heat up to 50 °C, stir and react for 30 min. Then add monomer A, 13.4 g of DOPO, and 0.4 g of N-vinylcarbazole, and emulsify for 30 min. Heat up to 65 °C and reflux with water, then heat up to 75 °C, and dropwise add 12 g of ammonium persulfate initiator (dissolved in 20 g of water) over 0.5 h. React for 1 h to obtain the core layer emulsion.

[0029] (2) While dropping monomer B and 10 g of initiator (dissolved in 10 g of water) into all of the core layer emulsion obtained in step (1) simultaneously, the dropping time is 1 h. Keep stirring and reacting at 70 °C for 1 h, then add 6.9 g of DOPO and react at 70 °C for 1 h. Cool down to 50 °C, add 14 g of emulsifier B (AEO-9), react for 30 min, then add 0.5 g of N-vinylcarbazole and react at 70 °C for 0.25 h. At 40 °C, add 14.2 g of ammonium polyphosphate solution (dissolved in 10 g of water), 0.5 g of aluminum sulfate, 0.1 g of ammonium molybdate, and 0.5 g of chitosan / gelatin composite microspheres. Under a rotation speed of 1000 r / min, perform high-speed shear emulsification for 0.5 h. Wait for the foam to disappear, add ammonia water to adjust the pH value to 7 - 8 to obtain a flame-retardant, high-refractive-index, melt-drop-resistant acrylic resin coating.

[0030] The monomer A is composed of 20 g of ethyl acrylate, 22 g of methyl methacrylate, 18 g of 2-hydroxyethyl acrylate, 6 g of amino-functionalized carbon nanotubes, and 3.4 g of high-refractive-index material.

[0031] The monomer B is composed of 8 g of amino-functionalized carbon nanotubes, 12 g of methyl methacrylate, 55 g of 2-hydroxyethyl acrylate, and 3.2 g of high-refractive-index material.

[0032] The preparation method of the amino-functionalized carbon nanotubes is as follows:

[0033] Disperse 0.7 g of carbon nanotubes under the action of 100 mL of concentrated sulfuric acid and concentrated nitric acid with a volume ratio of 3:1 by ultrasonic treatment for 2 h. After ultrasonic treatment, dilute the carbon nanotube solution with 100 mL of water, filter the acid solution with a vacuum pump, and wash with deionized water until neutral. Dry overnight at 100 °C to obtain carboxylated carbon nanotubes. Then dissolve 3.6 g of phosphorus trichloride in 10 mL of DMF solution, add 0.2 g of carboxylated carbon nanotubes and 4.5 g of bis(2-ethylhexanoic acid)hydroxyaluminum, react at 50 °C for 30 min, then place it in a 70 °C constant temperature oil bath and add 7.7 g of acrylamide to react for 2 h. Wash it clean with 10 mL of DMF and 30 mL of toluene in sequence, filter, and dry overnight under vacuum at 100 °C to obtain amino-functionalized carbon nanotubes.

[0034] The preparation method of the high refractive index material is as follows: Under a nitrogen atmosphere, 7.3 g of dimercaptothiadiazole is uniformly dissolved in 40 mL of anhydrous dichloromethane, 22 mL of triethylamine and 2.2 g of phthalic anhydride are added, and the mixture is stirred at -5°C for 0.5 h. Then, 20 mL of a mixed solution of acryloyl chloride and dichloromethane with a volume ratio of 1:1 is added dropwise using a dropping funnel, and the reaction is carried out at room temperature for 24 h. The reaction solution is extracted twice with a 10% HCl aqueous solution to neutralize the excess triethylamine, and then extracted twice with a saturated sodium chloride aqueous solution to obtain the high refractive index material.

[0035] The preparation method of chitosan / gelatin composite microspheres:

[0036] (1) Dissolve 5 g of chitosan in 50 mL of a 4% acetic acid aqueous solution by mass, and dissolve 3 g of gelatin in 40 mL of deionized water at 55°C. Then, mix the chitosan aqueous solution and the gelatin aqueous solution to form a chitosan / gelatin mixed solution;

[0037] (2) Add 30 mL of paraffin and 5 g of span80 to a three-necked flask, heat to 50°C, stir for 15 min, and drop the chitosan / gelatin mixed solution in step (1) into the three-necked flask using a separatory funnel. The dropping time is 15 min, and emulsification is carried out at 60°C for 30 min. After emulsification, quickly cool to 20°C, add 1 mL of 50% glutaraldehyde by mass, and cure for 0.5 h. Centrifuge with a high-speed centrifuge and collect the composite microspheres, wash them with acetone and isopropanol, and then dry them to obtain the chitosan / gelatin composite microspheres. Example Two

[0038] The preparation method of the flame-retardant, high refractive index, and melt-drop resistant water-based acrylate resin coating is prepared according to the following steps:

[0039] (1) Prepare the core layer emulsion: Add 700 g of water, 19 g of emulsifier A (sodium dodecylbenzenesulfonate and AEO-9 in a mass ratio of 2.5:1), and 45 g of methacrylic acid to a reaction vessel, mix and stir evenly, heat to 55°C, and stir and react for 60 min. Then, add monomer A, 14.5 g of DOPO, and 0.6 g of N-vinylcarbazole, and emulsify for 40 min; heat to 65°C to reflux water, heat to 85°C, and dropwise add 14 g of potassium persulfate initiator (dissolved in 20 g of water). The dropping time is 1.5 h, and the reaction is carried out for 2 h to obtain the core layer emulsion;

[0040] (2) To all the core layer emulsions obtained in step (1), simultaneously add dropwise all of monomer B and 14 g of potassium persulfate initiator (dissolved in 14 g of water). The dropping time is 1.5 h. Keep stirring and reacting at 85 °C for 2 h. Then add 12.2 g of DOPO and react at 80 °C for 2 h. Cool down to 50 °C, add 21 g of AEO-9 emulsifier B, react for 60 min. Then add 0.6 g of N-vinylcarbazole and react for 0.5 h. Then add 14.2 g of ammonium polyphosphate solution dissolved in 10 g of water, 1.3 g of aluminum sulfate, 0.2 g of ammonium molybdate and 0.8 g of chitosan / gelatin composite microspheres. Under the rotation speed of 2000 r / min, carry out high-speed shear emulsification for 1 h. Wait for the foam to disappear, adjust the pH value to 7 - 8 with ammonia water to obtain a flame-retardant, high-refractive-index, melt-drop-resistant acrylic resin coating;

[0041] The monomer A is composed of 35 g of ethyl acrylate, 38 g of methyl methacrylate, 32 g of 2-hydroxyethyl acrylate, 12 g of amino-functionalized carbon nanotubes and 6.2 g of high-refractive-index material;

[0042] The monomer B is composed of 14 g of amino-functionalized carbon nanotubes, 54 g of methyl methacrylate, 92 g of 2-hydroxyethyl acrylate and 5.8 g of high-refractive-index material.

[0043] The preparation method of the amino-functionalized carbon nanotubes is as follows:

[0044] Under the action of 100 mL of concentrated sulfuric acid and concentrated nitric acid with a volume ratio of 4:1, ultrasonically disperse 0.7 g of carbon nanotubes for 3 h. After ultrasonic treatment, dilute the carbon nanotube solution with 100 mL of water, filter it with a vacuum pump, and wash it with deionized water until neutral. Dry it at 105 °C overnight to obtain carboxylated carbon nanotubes; then dissolve 3.6 g of phosphorus trichloride in 10 mL of DMF solution, add 0.4 g of carboxylated carbon nanotubes and 4.7 g of bis(2-ethylhexanoic acid)aluminum hydroxide, react at 60 °C for 60 min, then place it in an 80 °C constant temperature oil bath and add 9.4 g of acrylamide to react for 4 h. Wash it successively with 10 mL of DMF and 30 mL of toluene, filter it, and vacuum dry it at 105 °C overnight to obtain amino-functionalized carbon nanotubes.

[0045] The preparation method of the high-refractive-index material is as follows: Under a nitrogen atmosphere, dissolve 7.3 g of 2,5-dimercapto-1,3,4-thiadiazole uniformly in 40 mL of anhydrous dichloromethane, add 22 mL of triethylamine and 2.9 g of phthalic anhydride, stir at -5 °C for 0.5 - 1 h, slowly add dropwise 20 mL of a mixed solution of acryloyl chloride and dichloromethane with a volume ratio of 1:1 using a dropping funnel, react at room temperature for 24 h, then extract the solution with 10% HCl aqueous solution for 2 - 3 times to neutralize the excess triethylamine, and then extract it with saturated sodium chloride aqueous solution for 2 - 3 times to obtain the high-refractive-index material.

[0046] The preparation method of the chitosan / gelatin composite microspheres:

[0047] (1) Dissolve 6 g of chitosan in 50 mL of a 4% acetic acid aqueous solution by mass, and dissolve 4 g of gelatin in 40 mL of deionized water at 55 °C. Then mix the chitosan aqueous solution and the gelatin aqueous solution to form a chitosan / gelatin mixture.

[0048] (2) Add 30 mL of paraffin and 5 g of span80 to a three-necked flask, heat to 60 °C, stir for 30 min. Use a separatory funnel to drop the chitosan / gelatin mixture from step (1) into the three-necked flask. The dropping time is 15 min, emulsify at 70 °C for 40 min. After emulsification, quickly cool to 20 °C, add 1 mL of 50% glutaraldehyde by mass, cure for 1 h. After curing, centrifuge with a high-speed centrifuge and collect the composite microspheres, wash with acetone and isopropyl alcohol and then dry to obtain the chitosan / gelatin composite microspheres. Example 3

[0049] A method for preparing a flame-retardant, high-refractive-index, melt-drop-resistant water-based acrylate resin coating is prepared according to the following steps:

[0050] (1) Prepare the core layer emulsion: Add 600 g of water, 16 g of emulsifier A (a mixture of sodium dodecylbenzenesulfonate and AEO-9 in a mass ratio of 2.5:1), and 35 g of methacrylic acid to a reaction vessel, mix and stir evenly, heat to 50 °C, stir and react for 45 min. Then add monomer A, 14 g of DOPO, and 0.5 g of N-vinylcarbazole, emulsify for 35 min; heat to 65 °C and reflux with water, heat to 80 °C, dropwise add 13 g of ammonium persulfate initiator (dissolved in 20 g of water), the dropping time is 1 h, react for 1.5 h to obtain the core layer emulsion;

[0051] (2) While dropping all of monomer B and 12 g of ammonium persulfate initiator (dissolved in 20 g of water) into all of the core layer emulsion obtained in step (1), the dropping time is 1 h, keep the temperature at 75 °C and stir and react for 1.5 h. Then add 9.5 g of DOPO, react at 75 °C for 1.5 h, cool to 50 °C, add 17.5 g of emulsifier B AEO-9, react for 45 min. Then add 0.55 g of N-vinylcarbazole, react for 0.35 h. Then add 14.2 g of ammonium polyphosphate solution (dissolved in 10 g of water), 0.9 g of aluminum sulfate, 0.15 g of ammonium molybdate, and 0.65 g of chitosan / gelatin composite microspheres, and carry out high-speed shear emulsification at a rotation speed of 1500 r / min for 0.75 h. Wait for the foam to disappear, add ammonia water to adjust the pH value to 7 - 8 to obtain the flame-retardant, high-refractive-index, melt-drop-resistant water-based acrylate resin coating;

[0052] The monomer A is composed of 27.5 g of ethyl acrylate, 30 g of methyl methacrylate, 25 g of 2-hydroxyethyl acrylate, 9 g of amino-functionalized carbon nanotubes, and 4.8 g of a high-refractive-index material;

[0053] The monomer B is prepared by mixing 11 g of aminated carbon nanotubes, 33 g of methyl methacrylate, 73.5 g of 2-hydroxyethyl acrylate, and 4.5 g of a high refractive index material.

[0054] The preparation method of the aminated carbon nanotubes is as follows:

[0055] 0.7 g of carbon nanotubes are ultrasonically dispersed for 2.5 h under the action of 100 mL of concentrated sulfuric acid and concentrated nitric acid with a volume ratio of 3.5:1. After ultrasonic treatment, the carbon nanotube solution is diluted with 100 mL of water, filtered by a vacuum pump, and washed with deionized water until neutral, and then dried overnight at 100 °C to obtain carboxylated carbon nanotubes; then 3.6 g of phosphorus trichloride is dissolved in 10 mL of DMF solution, 0.3 g of carboxylated carbon nanotubes and 4.6 g of aluminum hydroxybis(2-ethylhexanoate) are added, and the reaction is carried out at 55 °C for 45 min, then placed in a constant temperature oil bath at 75 °C and 8.5 g of acrylamide is added for reaction for 3 h, and then washed successively with 10 mL of DMF and 30 mL of toluene, filtered and dried under vacuum at 100 °C overnight to obtain aminated carbon nanotubes.

[0056] The preparation method of the high refractive index material is as follows: Under a nitrogen atmosphere, 7.3 g of 2,5-dimercapto-1,3,4-thiadiazole is uniformly dissolved in 40 mL of anhydrous dichloromethane, 22 mL of triethylamine and 2.6 g of phthalic anhydride are added, stirred at -5 °C for 0.75 h, and a mixed solution of 20 mL of acryloyl chloride and dichloromethane with a volume ratio of 1:1 is slowly added dropwise using a dropping funnel, reacted at room temperature for 24 h, and then the solution is extracted 3 times with 10% aqueous HCl solution to neutralize the excess triethylamine, and then extracted 3 times with saturated sodium chloride aqueous solution to obtain the high refractive index material.

[0057] The preparation method of the chitosan / gelatin composite microspheres:

[0058] (1) 5.5 g of chitosan is dissolved in 50 mL of a 4% acetic acid aqueous solution by mass, and 3.5 g of gelatin is dissolved in 40 mL of deionized water at 55 °C, and then the chitosan aqueous solution and the gelatin aqueous solution are mixed into a chitosan / gelatin mixed solution;

[0059] (2) 30 mL of paraffin and 5 g of span80 are added to a three-necked flask, heated to 55 °C, stirred for 30 min, and the chitosan / gelatin mixed solution in step (1) is added dropwise to the three-necked flask using a separating funnel, the dropping time is 15 min, emulsified at 65 °C for 35 min, and after emulsification, the temperature is quickly lowered to 20 °C, and 1 mL of 50% glutaraldehyde by mass is added for curing for 0.75 h. After curing, the composite microspheres are centrifuged by a high-speed centrifuge and collected, washed with acetone and isopropanol, and then dried to obtain the chitosan / gelatin composite microspheres.

[0060] Pour the prepared acrylate resin coating into a polytetrafluoroethylene mold, control the thickness to 3 mm, and conduct tests such as the melt dripping test and cone calorimeter test.

[0061] Melt dripping test

[0062] (1) Specimen preparation: Place the prepared acrylate resin film in a thermostatic and humidistatic chamber set at 23°C ± 0.5°C and humidity 50% ± 5% for 48 h. Then take it out and cut it into specimens of 110 cm × 10 cm × 3 mm. Prepare 2 sets of specimens, with 5 specimens in each group.

[0063] (2) Parameter setting: Clamp about 5 mm from the upper end to make the specimen vertical downward. Place a rosin wood board at the lower end of the specimen, and pad about 0.3 g of absorbent cotton on the board. Place it evenly on the board. Adjust the gas flow rate to 105 ± 5 mL / min to make the height of the flame reach 20 ± 1 mm. Set the combustion time to 10 s.

[0064] (3) Flame application and recording: After setting the parameters, start the flame application for ignition. After 10 s of ignition, press the afterflame time start button. When the specimen finishes burning and only has sparks left, press the afterflame combustion end button to enter the afterglow time. When it completely extinguishes, press the afterglow time end button to record the afterflame time and afterglow time of combustion.

[0065] (4) Melt dripping observation: During the combustion process, pay attention to observing whether there is melt dripping during combustion, and whether the melt dripping onto the lower absorbent cotton will cause secondary combustion, and record the observation results.

[0066] Using ASTM E1354 - 1990 (2004 standard), analyze and determine with the cone calorimeter 2000 of FTT Company in the UK. The specimen is 10 cm × 10 cm and the thickness is 3 mm, and the heat radiation power is 12 kW / m 2 , measure the maximum heat release rate pkHHR kW / m 2 , THR total heat release MJ / m², the smoke generation rate pSPR reaches the peak m 2 / s and the highest total smoke release (TSR) m 2 / m 2 .

[0067] The yellowing resistance is determined by observing the color change after irradiating under an ultraviolet lamp under simulated sunlight for 48 h to determine the yellowing resistance. Use a bulb - type yellowing resistance instrument of model HZ - 3017 for testing.

[0068] Use a UV - 7504 type ultraviolet - visible spectrophotometer to test the light transmittance of the polymer film and observe the light transmittance at 450 nm.

[0069] The refractive index is measured for the film using an Abbe refractometer.

[0070] The shrinkage rate of the film is the area of the polyurethane emulsion film formed at 80°C and the area after cooling to room temperature. The shrinkage rate is the percentage of the difference between the area at room temperature and the area of the film formed at 80°C to the area of the film formed at 80°C.

[0071] Table 1 Properties of the films formed by flame-retardant, high-refractive-index, and melt-drop-resistant waterborne acrylate resins

[0072] Index Example 1 Example 2 Example 3 Comparative Example pkHHR 198.2 196.4 190.5 241.6 THR 26.4 28.9 31.5 36.8 Droplet condition No droplet dripping No droplet dripping No droplet dripping No droplet dripping pSPR smoke generation rate 0.08 0.09 0.10 0.12 TSR 112 108 114 120 Yellowing resistance (grade) 4.0 4.0 4.0 4.0 Oxygen index (%) 29.8 29.2 30.2 26.5 Refractive index 1.69 1.71 1.72 1.51 Transmittance (%) 95.2 95.8 96.1 94.1 Film shrinkage rate (%) 3.2 3.8 2.9 4.6

[0073] The comparative example is Example 1 of the invention patent CN118813107B. It can be found from Table 1 that the flame-retardant indexes such as pkHHR, THR, melt-drop situation, pSPR smoke generation rate, and TSR of the acrylate resin films obtained in Examples 1 to 3 of the present invention are all better than those of the comparative example, and the refractive-index indexes such as refractive index and light transmittance are also relatively good, and the shrinkage rate of the film decreases less.

[0074] Taking Example 3 of the present invention as a comparison.

[0075] Table 2 Properties of the films formed by flame-retardant, high-refractive-index, and melt-drop-resistant waterborne acrylate resins

[0076] Example 3 Composition Combustion droplet phenomenon A large number of droplets Without amino-functionalized carbon nanotubes pkHHR 268.3 Without amino-functionalized carbon nanotubes THR 48.6 Without amino-functionalized carbon nanotubes pSPR smoke generation rate 0.324 Without amino-functionalized carbon nanotubes TSR 165.3 Without amino-functionalized carbon nanotubes Oxygen index (%) 28.6 Without amino-functionalized carbon nanotubes Combustion droplet phenomenon With droplets but no dripping With amino-functionalized carbon nanotubes, without bis(2-ethylhexanoic acid) aluminum hydroxide pkHHR 242.6 With amino-functionalized carbon nanotubes, without bis(2-ethylhexanoic acid) aluminum hydroxide THR 37.6 With amino-functionalized carbon nanotubes, without bis(2-ethylhexanoic acid) aluminum hydroxide pSPR smoke generation rate 0.262 With amino-functionalized carbon nanotubes, without bis(2-ethylhexanoic acid) aluminum hydroxide TSR 138.6 With amino-functionalized carbon nanotubes, without bis(2-ethylhexanoic acid) aluminum hydroxide Oxygen index (%) 29.2 With amino-functionalized carbon nanotubes, without bis(2-ethylhexanoic acid) aluminum hydroxide Combustion droplet phenomenon Melting without dripping With amino-functionalized carbon nanotubes, without acrylamide pkHHR 230.5 With amino-functionalized carbon nanotubes, without acrylamide THR 38.6 With amino-functionalized carbon nanotubes, without acrylamide Oxygen index (%) 29.3 With amino-functionalized carbon nanotubes, without acrylamide pkHHR 213.5 With amino-functionalized carbon nanotubes, without phosphorus trichloride Oxygen index (%) 28.4 With amino-functionalized carbon nanotubes, without phosphorus trichloride Oxygen index (%) 26.2 Without DOPO Oxygen index (%) 26.0 Without APP Oxygen index (%) 28.8 Without aluminum sulfate Oxygen index (%) 28.4 Without N-vinylcarbazole

[0077] It can be seen from Table 2 that amino carbon nanotubes, aluminum bis(2-ethylhexanoate), acrylamide, DOPO, APP, aluminum sulfate, and N-vinylcarbazole all have a significant effect on improving the flame-retardant performance of acrylate resins.

[0078] Table 3 Properties of the films formed by flame-retardant, high-refractive-index, and melt-drop-resistant waterborne acrylate resins

[0079] Example 3 Composition Yellowing resistance (grade) 3.0 Without high refractive index material Refractive index 1.42 Without high refractive index material Transmittance (%) 91.8 Without high refractive index material Yellowing resistance (grade) 3.5 With high refractive index material, without acryloyl chloride Refractive index 1.62 With high refractive index material, without acryloyl chloride Transmittance (%) 92.3 With high refractive index material, without acryloyl chloride Yellowing resistance (grade) 3.0 With high refractive index material, without 2,5-dimercapto-1,3,4-thiadiazole Refractive index 1.46 With high refractive index material, without 2,5-dimercapto-1,3,4-thiadiazole Transmittance (%) 90.3 With high refractive index material, without 2,5-dimercapto-1,3,4-thiadiazole Refractive index 1.57 With high refractive index material, without phthalic anhydride Yellowing resistance (grade) 3.5 With high refractive index material, without phthalic anhydride

[0080] It can be found from Table 3 that high-refractive-index materials, acryloyl chloride, phthalic anhydride, and 2,5-dimercapto-1,3,4-thiadiazole all have a great influence on the refractive-index resistance of acrylate resins. High-refractive-index materials can increase the refractive index of the acrylate resin segments and make the distribution of refractive monomer units more uniform at the same time.

[0081] Table 4 Properties of the films formed by flame-retardant, high-refractive-index, and melt-drop-resistant waterborne acrylate resins

[0082] Example 3 Composition Film shrinkage rate (%) 4.6 Without N-vinylcarbazole Film shrinkage rate (%) 5.2 Without chitosan / gelatin composite microspheres

[0083] As can be seen from Table 4, N-vinylcarbazole and chitosan / gelatin composite microspheres have a great influence on the film shrinkage rate of acrylate resins. The nitrogen condensed ring structure of N-vinylcarbazole makes it show less shrinkage after curing and has good heat resistance. Under dry conditions, the chitosan / gelatin composite microspheres have the advantage of a small decrease in shrinkage rate, reducing the decrease in the film of acrylate resin at room temperature. In addition, the addition of ammonium molybdate improves the precipitation-free property of the acrylate resin emulsion for 96 hours, while there is a small amount of precipitation in the acrylate resin emulsion without ammonium molybdate after 96 hours.

Claims

1. A method for preparing a flame retardant, high refractive, and drip resistant aqueous acrylic resin coating, characterized in that: Prepare according to the following steps: (1) Preparation of core layer emulsion: Add 500-700 g of water, 13-19 g of emulsifier A, and 25-45 g of methacrylic acid into a reaction container, mix and stir evenly, heat to 50-55°C, stir and react for 30-60 min, then add monomer A, 13.4-14.5 g of DOPO, and 0.4-0.6 g of N-vinyl carbazole, and emulsify for 30-40 min; heat to 65°C, pass reflux water, heat to 75-85°C, dropwise add 12-14 g of initiator, dropwise add for 0.5-1.5 h, react for 1-2 h, and obtain core layer emulsion; (2) To the core layer emulsion obtained in step (1), 10-14 g of monomer B and initiator are added dropwise at the same time for 1-1.5 h, and the mixture is stirred at 70-85 °C for 1-2 h. Then 6.9-12.2 g of DOPO is added, and the mixture is reacted at 70-80 °C for 1-2 h. The mixture is cooled to 50 °C, and 14-21 g of emulsifier B is added for 30-60 min. Then 0.5-0.6 g of N-vinyl carbazole is added, and the mixture is reacted at 70-80 °C for 0.25-0.5 h. Then 14.2 g of ammonium polyphosphate solution dissolved in 10 g of water, 0.5-1.3 g of aluminum sulfate, 0.1-0.2 g of ammonium molybdate, and 0.5-0.8 g of chitosan / gelatin composite microspheres are added at 40-50 °C. 1000-2000 At a speed of r / min, high-speed shear emulsification is performed for 0.5-1h, and when the foam disappears, ammonia water is added to adjust the pH value to 7-8 to obtain a flame-retardant, high-refractive, and drip-resistant water-based acrylic resin coating; The monomer A is prepared by mixing 20-35g of ethyl acrylate, 22-38g of methyl methacrylate, 18-32g of hydroxyethyl acrylate, 6-12g of amino carbon nanotubes, and 3.4-6.2g of high refractive material; the preparation method of the amino carbon nanotubes is as follows: 0.7 g of carbon nanotubes were subjected to ultrasonic dispersion treatment for 2 to 3 h in concentrated sulfuric acid and 100 mL of concentrated nitric acid in a volume ratio of 3: 1 to 4:

1. After ultrasonication, the carbon nanotube solution was diluted with 100 mL of water, filtered with a vacuum pump, washed with deionized water until neutral, and dried at 100 to 105° C. overnight to obtain carboxylated carbon nanotubes; 3.6 g of phosphorus trichloride was dissolved in 10 mL of DMF solution, 0.2 to 0.4 g of carboxylated carbon nanotubes and 4.5 to 4.7 g of bis(2-ethylhexanoic acid) hydroxyaluminum were added, reacted at 50 to 60° C. for 30 to 60 min, then placed in a constant temperature oil bath at 70 to 80° C., 7.7 to 9.4 g of acrylamide were added and reacted for 2 to 4 h, washed with 10 mL of DMF and 30 mL of toluene in sequence, filtered, and dried at 100 to 105° C. overnight in vacuum to obtain amino carbon nanotubes; The monomer B is prepared by mixing 8-14g of amino carbon nanotubes, 12-54g of methyl methacrylate, 55-92g of hydroxyethyl acrylate and 3.2-5.8g of high refractive material.

2. The method for preparing the flame-retardant, high-refractive, and drip-resistant aqueous acrylic resin coating according to claim 1, characterized in that: The emulsifier A is prepared by mixing sodium dodecylbenzene sulfonate and AEO-9 in a mass ratio of 2.5:

1.

3. The method for preparing the flame-retardant, high-refractive, and drip-resistant aqueous acrylic resin coating according to claim 1, characterized in that: The initiator is any one of ammonium persulfate and potassium persulfate.

4. The method for preparing the flame-retardant, high-refractive, and drip-resistant aqueous acrylic resin coating according to claim 1, characterized in that: The preparation method of the high-refractive material is as follows: under a nitrogen atmosphere, 7.3 g of dithiothiadiazole is uniformly dissolved in 40 mL of anhydrous dichloromethane, 22 mL of triethylamine and 2.2-2.9 g of phthalic anhydride are added, and the mixture is stirred at -5°C for 0.5-1 h. A dropping funnel is used to slowly dropwise add 20 mL of a 1:1 volume ratio of acryloyl chloride to dichloromethane solution, and the mixture is reacted at room temperature for 24 h. The reaction solution is then extracted 2-3 times with a 10% HCl aqueous solution to neutralize excess triethylamine, and then extracted 2-3 times with a saturated sodium chloride aqueous solution to obtain a high-refractive material.

5. The method for preparing the flame-retardant, high-refractive, and drip-resistant aqueous acrylic resin coating according to claim 1, characterized in that: The emulsifier B is AEO-9.

6. The method for preparing the flame-retardant, high-refractive, and drip-resistant aqueous acrylic resin coating according to claim 1, characterized in that: Preparation method of chitosan / gelatin composite microspheres: (1) Dissolve 5-6 g of chitosan in 50 mL of 4% by mass acetic acid aqueous solution, and dissolve 3-4 g of gelatin in 40 mL of deionized water at 55°C, then mix the chitosan aqueous solution and the gelatin aqueous solution to form a chitosan / gelatin mixed solution; (2) Add 30 mL of paraffin wax and 5 g of span80 into a three-necked flask, heat to 50-60°C, stir for 15-30 min, and slowly drip the chitosan / gelatin mixed solution in step (1) into the three-necked flask using a separatory funnel for 15 min. Emulsify at 60-70°C for 30-40 min. After emulsification, quickly cool to 20°C, add 1 mL of 50% glutaraldehyde, and solidify for 0.5-1 h. After solidification, centrifuge and collect the composite microspheres using a high-speed centrifuge, wash with acetone and isopropanol, and dry to obtain chitosan / gelatin composite microspheres.