An aging-resistant and flame-retardant epoxy resin coating and its preparation process

Abstract

This invention provides an aging-resistant flame-retardant epoxy resin coating and its preparation process, belonging to the field of coating preparation technology. The preparation process includes the following steps: preparing a flame-retardant additive; preparing coated modified black phosphorus nanosheets; preparing modified hollow glass microspheres; and preparing an epoxy resin coating. This invention first dissolves 3,4-dihydroxybenzaldehyde and 2-amino-4-methylphenol in anhydrous ethanol and then heats them under reflux. This causes the aldehyde group in 3,4-dihydroxybenzaldehyde to undergo dehydration condensation with the amino group in 2-amino-4-methylphenol, generating an intermediate containing an imine bond. Then, the intermediate and hexachlorocyclotriphosphazene are dissolved separately and mixed for reaction. This allows the phenolic hydroxyl group in the intermediate to undergo a nucleophilic substitution reaction with the hexachlorocyclotriphosphazene, generating a flame-retardant additive containing phosphorus and a Schiff base structure. This flame-retardant additive has good compatibility with the epoxy resin matrix, is not easily precipitated, and can effectively improve the flame-retardant performance of the epoxy resin coating.

Description

Technical Field

[0001] This invention relates to the field of coating preparation technology, specifically to an aging-resistant and flame-retardant epoxy resin coating and its preparation process. Background Technology

[0002] Epoxy resin coatings are widely used in construction, transportation, chemical, and electronics industries due to their excellent adhesion, corrosion resistance, and mechanical properties. However, traditional epoxy resin coatings are susceptible to UV radiation and environmental factors when used outdoors, leading to coating aging, yellowing, chalking, and cracking, which severely affects their service life. Furthermore, epoxy resin itself is a flammable material, posing a fire hazard during use; therefore, flame retardants need to be added to improve its flame-retardant properties.

[0003] Organophosphorus compounds can impart flame-retardant properties to epoxy resin-based coatings. Currently, most phosphorus-containing flame retardants provide flame-retardant activity through a combination of gas-phase and condensed-phase reactions, polymer carbonization promotion, and coking effects. However, most organophosphorus flame retardants typically have small molecular weights and significant differences in chemical structure from epoxy resins, resulting in weak interactions between the two. This leads to poor compatibility with the epoxy resin matrix and easy exudation, thus affecting their flame-retardant modification effect on epoxy resin coatings. Furthermore, excessive addition can easily reduce the mechanical properties of the resin matrix, leading to deterioration of the material's physical and mechanical properties.

[0004] Black phosphorus nanosheets possess typical characteristics of two-dimensional nanomaterials. Their honeycomb layer stacked structure can reflect and scatter ultraviolet rays. Adding them to epoxy resin coatings is expected to reduce the direct exposure of epoxy resin to ultraviolet rays, thus playing a physical shielding role and improving the coating's resistance to ultraviolet aging. However, the strong van der Waals forces between the layers of black phosphorus nanosheets make them prone to agglomeration in the epoxy resin matrix, thereby reducing their dispersibility. Furthermore, the interfacial bonding force between black phosphorus nanosheets and the epoxy resin matrix is ​​weak, which makes it easy for black phosphorus nanosheets to detach from the matrix during epoxy resin curing and use, resulting in a decrease in the coating's resistance to ultraviolet aging.

[0005] Therefore, it is necessary to propose an aging-resistant flame-retardant epoxy resin coating and its preparation process that has good compatibility between the flame retardant and the epoxy resin matrix, is not prone to precipitation, and can improve the dispersibility of black phosphorus nanosheets, so as to extend the service life of the coating. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide an aging-resistant and flame-retardant epoxy resin coating and its preparation process.

[0007] A preparation process for an aging-resistant and flame-retardant epoxy resin coating includes the following steps:

[0008] S1: Preparation of flame retardant additives

[0009] Flame retardant additives were prepared using 3,4-dihydroxybenzaldehyde, 2-amino-4-methylphenol and hexachlorocyclotriphosphazene as raw materials;

[0010] S2: Preparation of coated modified black phosphorus nanosheets

[0011] Alkali lignin was quaternized and reacted with dopamine hydrochloride to prepare a polymer modifier, which was then used to modify aminated black phosphorus nanosheets to obtain coated modified black phosphorus nanosheets.

[0012] S3: Preparation of modified hollow glass microspheres

[0013] The pre-treated hollow glass microspheres were aminated, then reacted with hexamethylene diisocyanate trimer, and finally a fluoropolymer was added to react and obtain modified hollow glass microspheres.

[0014] S4: Preparation of epoxy resin coatings

[0015] Add 90-100 parts by weight of bisphenol A type epoxy resin to 95-100 parts by weight of organic solvent and stir thoroughly to dissolve. Then add 32-36 parts by weight of the above-mentioned flame retardant additive, 10-12 parts by weight of coated modified black phosphorus nanosheets and 20-30 parts by weight of modified hollow glass microspheres. After stirring thoroughly, add 20-30 parts by weight of curing agent, 1-2 parts by weight of defoamer, 1-2 parts by weight of leveling agent and 3-5 parts by weight of plasticizer. After thorough mixing, the epoxy resin coating is obtained.

[0016] Furthermore, S1 specifically includes the following steps:

[0017] S1.1: Add 3,4-dihydroxybenzaldehyde and 2-amino-4-methylphenol to anhydrous ethanol at a solid-liquid ratio of (1.2-1.4) g: 1 g: (20-30) mL, then add glacial acetic acid to adjust the pH to 4-5, and heat to reflux at 70-80℃ for 8-12 h. After cooling to room temperature, filter, wash and vacuum dry to obtain the intermediate.

[0018] S1.2: Add the above intermediate to anhydrous tetrahydrofuran at a solid-liquid ratio of 1g:(10-20)mL, stir thoroughly to dissolve, then add triethylamine, stir thoroughly to disperse, and obtain a mixed solution;

[0019] S1.3: Dissolve hexachlorocyclotriphosphazene in anhydrous tetrahydrofuran at a solid-liquid ratio of 1g:(8-10)mL to prepare a hexachlorocyclotriphosphazene solution. Place the above mixed solution in an ice-water bath at 3-5℃ and add the hexachlorocyclotriphosphazene solution dropwise while stirring. After the addition is complete, heat and stir the reaction at 40-50℃ for 12-16h. Then remove the tetrahydrofuran by vacuum distillation, wash with deionized water until neutral, and recrystallize with methanol to obtain the flame retardant additive.

[0020] Furthermore, S2 specifically includes the following steps:

[0021] S2.1: Add alkali lignin to a 20% sodium hydroxide solution at a solid-liquid ratio of 1g:(3-5)mL, stir thoroughly to dissolve, then add 3-chloro-2-hydroxypropyltrimethylammonium chloride, and heat and stir at 80-90℃ for 3-4h. After dialysis purification and freeze drying, quaternized alkali lignin is obtained.

[0022] S2.2: Add the above quaternized alkali lignin to Tris buffer solution with pH 8-9 at a solid-liquid ratio of 1g:(20-30)mL, stir thoroughly to dissolve, then add dopamine hydrochloride, hydrogen peroxide and ammonium persulfate, and stir to react for 20-24h. After dialysis purification and freeze drying, the polymer modifier is obtained.

[0023] S2.3: Add silane coupling agent KH550 to 60% ethanol solution at a volume ratio of 1:(98-100), and adjust the pH to 4-5 with acetic acid. Then add ultrasonically cleaned and dried black phosphorus nanosheets at a solid-liquid ratio of 1g:(20-30)mL, disperse ultrasonically for 10-20min, and heat at 50-60℃ for 2-3h. Filter to obtain aminated black phosphorus nanosheets.

[0024] S2.4: Dissolve the above polymer modifier in Tris buffer at a solid-liquid ratio of 1g:(60-70)mL, then add the above aminated black phosphorus nanosheets at a solid-liquid ratio of 1g:(180-200)mL. After ultrasonic dispersion for 30-40min, add 0.1mol / L sodium hydroxide solution to adjust the pH to 7-8, and heat and stir the reaction at 50-60℃ for 10-12h under nitrogen protection. After centrifugation, washing and vacuum drying, the coated modified black phosphorus nanosheets are obtained.

[0025] Furthermore, S3 specifically includes the following steps:

[0026] S3.1: Add hollow glass microspheres with a particle size of 10μm to a 0.2-0.3mol / L sodium hydroxide solution at a solid-liquid ratio of 1g:(30-40)mL, heat and stir at 75-85℃ for 1-2h, filter and wash until neutral to obtain pretreated microspheres;

[0027] S3.2: The pretreated microbeads were ultrasonically mixed with deionized water and anhydrous ethanol at a mass ratio of 1:(1-3):(8-10), and then silane coupling agent KH550 was added. The mixture was stirred at 70-80℃ for 2-3 hours. After filtration, washing and vacuum drying, aminated microbeads were obtained.

[0028] S3.3: Add the above-mentioned aminated microbeads to the mixed solvent at a solid-liquid ratio of 1g:(30-40)mL and disperse by ultrasonication to obtain a microbead dispersion. At the same time, dissolve the hexamethylene diisocyanate trimer in the mixed solvent at a solid-liquid ratio of 1g:(10-20)mL to obtain a hexamethylene diisocyanate trimer solution.

[0029] S3.4: Add the above microbead dispersion to the above hexamethylene diisocyanate trimer solution at a volume ratio of 1:(3-5), stir and react for 3-4 hours to obtain isocyanate modified microbead dispersion;

[0030] S3.5: Dissolve the fluoropolymer in a mixed solvent at a solid-liquid ratio of 1g:(20-30)mL, then add an equal volume of the above isocyanate-modified microsphere dispersion, stir for 8-10h, filter, wash and dry to obtain modified hollow glass microspheres, wherein the fluoropolymer is a copolymer of alternating trifluorochloroethylene and vinyl ester.

[0031] Furthermore, the molar ratio of triethylamine to the intermediate is (2.4-2.6):1, and the molar ratio of hexachlorocyclotriphosphazene to the intermediate is 1:(2.4-2.8).

[0032] Furthermore, the molar ratio of 3-chloro-2-hydroxypropyltrimethylammonium chloride to alkali lignin is (1.2-1.4):1, and the molar ratio of quaternized alkali lignin to dopamine hydrochloride is (2-4):1.

[0033] Furthermore, the volume ratio of hydrogen peroxide to Tris buffer is 1:(120-140), and the mass ratio of ammonium persulfate to quaternized alkali lignin is 1:(90-100).

[0034] Furthermore, the mass ratio of silane coupling agent KH550 to hollow glass microspheres is 1:(90-100), and the mixed solvent is prepared by mixing ethyl acetate, xylene and butyl acetate in a mass ratio of (1-2):1:(1.1-1.3).

[0035] Furthermore, the curing agent is at least one of alicyclic amine modified curing agent, polyether amine modified curing agent, and fatty amine modified curing agent; the defoamer is an organosilicon defoamer; the leveling agent is an organosilicon leveling agent; at least one of DOS plasticizer, ESO plasticizer, and stearic acid; and the organic solvent is at least one of xylene, propylene glycol, acetone, butanone, and ethyl acetate.

[0036] Furthermore, an aging-resistant and flame-retardant epoxy resin coating is prepared by the preparation process of an aging-resistant and flame-retardant epoxy resin coating described in any one of the above claims.

[0037] Compared with the prior art, the present invention has at least the following beneficial effects:

[0038] 1. In this invention, 3,4-dihydroxybenzaldehyde and 2-amino-4-methylphenol are first dissolved in anhydrous ethanol and subjected to a reflux reaction, causing the aldehyde group in 3,4-dihydroxybenzaldehyde to undergo dehydration condensation with the amino group in 2-amino-4-methylphenol to generate an intermediate containing an imine bond. Then, the intermediate and hexachlorocyclotriphosphazene are dissolved separately and mixed for further reaction, allowing the phenolic hydroxyl group in the intermediate to undergo a nucleophilic substitution reaction with the hexachlorocyclotriphosphazene, generating a flame-retardant additive containing phosphorus and a Schiff base structure. When this flame-retardant additive is added to epoxy resin, on the one hand, the phenolic hydroxyl group in the flame-retardant additive can react with the epoxy resin... During the curing process, the groups undergo ring-opening reactions to form covalent bonds. The amino groups can act as catalysts or cross-linking points for the curing reaction of epoxy resin, enhancing the chemical bonding between the flame retardant additive and the epoxy resin. On the other hand, the phosphorus-nitrogen and phosphorus-oxygen bonds introduced by hexachlorocyclotriphosphazene have strong polarity, similar to the polarity of the ether bonds and hydroxyl groups of epoxy resin, which can reduce phase separation. Therefore, the flame retardant additive has good compatibility with the epoxy resin matrix and is not easy to precipitate, which can effectively improve the flame retardant properties of epoxy resin coatings. In addition, the chemical bonding between the flame retardant additive and the epoxy resin matrix also helps to improve the mechanical properties of epoxy resin coatings.

[0039] 2. In this invention, alkali lignin is quaternized by adding 3-chloro-2-hydroxypropyltrimethylammonium chloride. The quaternized alkali lignin is then dissolved in Tris buffer, and dopamine hydrochloride, hydrogen peroxide, and ammonium persulfate are added to react, thus preparing a polymer modifier for the graft polymerization of polydopamine and quaternized alkali lignin. This polymer modifier is then used to modify aminated black phosphorus nanosheets. After the polymer modifier coats the surface of the black phosphorus nanosheets, the hydrophobic segments and polar groups of the polymer modifier react with the epoxy resin. The compatibility of the hydrophobic regions and polar groups of the resin enables molecular-level dispersion, thereby effectively improving the dispersibility of black phosphorus nanosheets in epoxy resin and reducing agglomeration. In addition, since polydopamine in the polymer modifier can absorb ultraviolet light, and quaternized alkali lignin can inhibit the oxidative degradation of epoxy resin through free radical scavenging, the coating modification of black phosphorus nanosheets with this polymer modifier before its addition to epoxy resin coating can further improve the UV aging resistance of epoxy resin, thereby effectively extending the service life of epoxy resin coating.

[0040] 3. In this invention, the surface of the insulating glass microspheres is first pretreated, and then aminated using a silane coupling agent. This is followed by a nucleophilic addition reaction with hexamethylene diisocyanate trimer to introduce isocyanate groups onto the surface of the microspheres. Finally, a reaction with a fluoropolymer is carried out, chemically grafting the fluoropolymer onto the surface of the microspheres. This modification of the microspheres, forming a coating layer, not only effectively improves the compatibility between the microspheres and the epoxy resin matrix, but also, due to the CF bonds in the fluoropolymer... With high bond energy, the modified hollow glass microspheres, when added to epoxy resin coatings, can reduce the degree of ultraviolet light irradiation on the epoxy resin matrix, thereby improving the anti-ultraviolet aging performance of the epoxy resin coatings. In addition, when the modified hollow glass microspheres are added to epoxy resin coatings together with the modified black phosphorus nanosheets, the layered structure of the black phosphorus nanosheets can form a barrier layer to inhibit the permeation of oxygen and water vapor, while the hollow glass microspheres can reduce heat conduction. Therefore, the combination of the two can synergistically slow down the thermo-oxidative aging rate and improve the thermo-oxidative aging resistance of epoxy resin coatings. Attached Figure Description

[0041] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate embodiments of the present disclosure and, together with the specification, further serve to explain the principles of the present disclosure and enable those skilled in the art to implement and use the present disclosure.

[0042] Figure 1 This is a flowchart illustrating the preparation process of the aging-resistant and flame-retardant epoxy resin coating used in the embodiments of the present invention. Detailed Implementation

[0043] The following describes in detail, with reference to the accompanying drawings and specific embodiments, an aging-resistant and flame-retardant epoxy resin coating and its preparation process provided by the present invention.

[0044] Example 1

[0045] A preparation process for an aging-resistant and flame-retardant epoxy resin coating, such as... Figure 1 As shown, it includes the following steps:

[0046] S1: Preparation of flame retardant additives

[0047] S1.1: 3,4-Dihydroxybenzaldehyde and 2-amino-4-methylphenol were added to anhydrous ethanol at a solid-liquid ratio of 1.2g:1g:20mL, and glacial acetic acid was added to adjust the pH to 4. The mixture was heated to reflux at 70℃ for 8h. After cooling to room temperature, the intermediate was obtained by filtration, washing and vacuum drying.

[0048] S1.2: Add the above intermediate to anhydrous tetrahydrofuran at a solid-liquid ratio of 1g:10mL, stir thoroughly to dissolve, then add triethylamine, stir thoroughly to disperse, and obtain a mixed solution, wherein the molar ratio of triethylamine to intermediate is 2.4:1;

[0049] S1.3: Hexachlorocyclotriphosphazene was dissolved in anhydrous tetrahydrofuran at a solid-liquid ratio of 1g:8mL to prepare a hexachlorocyclotriphosphazene solution. The above mixed solution was then placed in an ice-water bath at 3℃, and the hexachlorocyclotriphosphazene solution was added dropwise while stirring. After the addition was completed, the mixture was heated and stirred at 40℃ for 12h. Then, the tetrahydrofuran was removed by vacuum distillation, and the mixture was washed with deionized water until neutral and recrystallized from methanol to obtain a flame retardant additive. The molar ratio of hexachlorocyclotriphosphazene to the intermediate was 1:2.4.

[0050] S2: Preparation of coated modified black phosphorus nanosheets

[0051] S2.1: Add alkali lignin to a 20% sodium hydroxide solution at a solid-liquid ratio of 1g:3mL, stir thoroughly to dissolve, then add 3-chloro-2-hydroxypropyltrimethylammonium chloride, and heat and stir at 80℃ for 3-4 hours. After dialysis purification and freeze drying, quaternized alkali lignin is obtained, wherein the molar ratio of 3-chloro-2-hydroxypropyltrimethylammonium chloride to alkali lignin is 1.2:1.

[0052] S2.2: The above-mentioned quaternized alkali lignin was added to Tris buffer solution at pH 8 at a solid-liquid ratio of 1g:20mL, stirred thoroughly to dissolve, then dopamine hydrochloride, hydrogen peroxide and ammonium persulfate were added, and the mixture was stirred and reacted for 20h. After dialysis purification and freeze drying, the polymer modifier was obtained. The molar ratio of quaternized alkali lignin to dopamine hydrochloride was 2:1, the volume ratio of hydrogen peroxide to Tris buffer solution was 1:120, and the mass ratio of ammonium persulfate to quaternized alkali lignin was 1:90.

[0053] S2.3: Add silane coupling agent KH550 to 60% ethanol solution at a volume ratio of 1:98, and add acetic acid to adjust the pH to 4. Then add ultrasonically cleaned and dried black phosphorus nanosheets at a solid-liquid ratio of 1g:20mL, ultrasonically disperse for 10min, and heat at 50℃ for 2h. Filter to obtain aminated black phosphorus nanosheets.

[0054] S2.4: Dissolve the above polymer modifier in Tris buffer at a solid-liquid ratio of 1g:60mL, then add the above aminated black phosphorus nanosheets at a solid-liquid ratio of 1g:180mL. After ultrasonic dispersion for 30min, add 0.1mol / L sodium hydroxide solution to adjust the pH to 7, and heat and stir at 50℃ for 10h under nitrogen protection. After centrifugation, washing and vacuum drying, the coated modified black phosphorus nanosheets are obtained.

[0055] S3: Preparation of modified hollow glass microspheres

[0056] S3.1: Hollow glass microspheres with a particle size of 10 μm were added to a 0.2 mol / L sodium hydroxide solution at a solid-liquid ratio of 1 g: 30 mL. The solution was heated and stirred at 75 °C for 1 h. After filtration and washing until neutral, pretreated microspheres were obtained.

[0057] S3.2: The pretreated microspheres were ultrasonically mixed with deionized water and anhydrous ethanol at a mass ratio of 1:1:8, and then silane coupling agent KH550 was added. The mixture was stirred at 70°C for 2 hours. After filtration, washing and vacuum drying, aminated microspheres were obtained. The mass ratio of silane coupling agent KH550 to hollow glass microspheres was 1:90.

[0058] S3.3: The above-mentioned aminated microbeads were added to a mixed solvent at a solid-liquid ratio of 1g:30mL and ultrasonically dispersed to obtain a microbead dispersion. At the same time, hexamethylene diisocyanate trimer was dissolved in the mixed solvent at a solid-liquid ratio of 1g:10mL to obtain a hexamethylene diisocyanate trimer solution. The mixed solvent was prepared by mixing ethyl acetate, xylene and butyl acetate in a mass ratio of 1:1:1.1.

[0059] S3.4: Add the above microbead dispersion to the above hexamethylene diisocyanate trimer solution at a volume ratio of 1:3, stir and react for 3 hours to obtain isocyanate modified microbead dispersion;

[0060] S3.5: Dissolve JF-2X type FEVE fluorinated resin in a mixed solvent at a solid-liquid ratio of 1g:20mL, then add an equal volume of the above isocyanate modified microsphere dispersion, stir and react for 8h, and obtain modified hollow glass microspheres after filtration, washing and drying.

[0061] S4: Preparation of epoxy resin coatings

[0062] 90 parts by weight of bisphenol A type epoxy resin were added to 95 parts by weight of xylene and stirred thoroughly to dissolve. Then, 32 parts by weight of the above-mentioned flame retardant additive, 10 parts by weight of coated modified black phosphorus nanosheets and 20 parts by weight of modified hollow glass microspheres were added and stirred thoroughly. After mixing thoroughly, 20 parts by weight of alicyclic amine modified curing agent, 1 part by weight of organosilicon defoamer, 1 part by weight of organosilicon leveling agent and 3 parts by weight of DOS plasticizer were added and mixed thoroughly to obtain epoxy resin coating.

[0063] Example 2

[0064] A preparation process for an aging-resistant and flame-retardant epoxy resin coating, such as... Figure 1 As shown, it includes the following steps:

[0065] S1: Preparation of flame retardant additives

[0066] S1.1: 3,4-Dihydroxybenzaldehyde and 2-amino-4-methylphenol were added to anhydrous ethanol at a solid-liquid ratio of 1.3g:1g:25mL, and glacial acetic acid was added to adjust the pH to 4.5. The mixture was then heated to reflux at 75℃ for 9 hours. After cooling to room temperature, the mixture was filtered, washed and vacuum dried to obtain the intermediate.

[0067] S1.2: Add the above intermediate to anhydrous tetrahydrofuran at a solid-liquid ratio of 1g:15mL, stir thoroughly to dissolve, then add triethylamine, stir thoroughly to disperse, and obtain a mixed solution, wherein the molar ratio of triethylamine to intermediate is 2.5:1;

[0068] S1.3: Hexachlorocyclotriphosphazene was dissolved in anhydrous tetrahydrofuran at a solid-liquid ratio of 1g:9mL to prepare a hexachlorocyclotriphosphazene solution. The above mixed solution was then placed in an ice-water bath at 4℃, and the hexachlorocyclotriphosphazene solution was added dropwise while stirring. After the addition was completed, the mixture was heated and stirred at 45℃ for 14h. Then, the tetrahydrofuran was removed by vacuum distillation, and the mixture was washed with deionized water until neutral and recrystallized from methanol to obtain a flame retardant additive. The molar ratio of hexachlorocyclotriphosphazene to the intermediate was 1:2.6.

[0069] S2: Preparation of coated modified black phosphorus nanosheets

[0070] S2.1: Alkali lignin was added to a 20% sodium hydroxide solution at a solid-liquid ratio of 1g:4mL, stirred thoroughly to dissolve, and then 3-chloro-2-hydroxypropyltrimethylammonium chloride was added. The mixture was heated and stirred at 85℃ for 3.5h. After dialysis purification and freeze-drying, quaternized alkali lignin was obtained, wherein the molar ratio of 3-chloro-2-hydroxypropyltrimethylammonium chloride to alkali lignin was 1.3:1.

[0071] S2.2: The above-mentioned quaternized alkali lignin was added to Tris buffer solution with pH 8.5 at a solid-liquid ratio of 1g:25mL, stirred thoroughly to dissolve, then dopamine hydrochloride, hydrogen peroxide and ammonium persulfate were added, and the mixture was stirred and reacted for 22h. After dialysis purification and freeze drying, the polymer modifier was obtained. The molar ratio of quaternized alkali lignin to dopamine hydrochloride was 3:1, the volume ratio of hydrogen peroxide to Tris buffer solution was 1:130, and the mass ratio of ammonium persulfate to quaternized alkali lignin was 1:95.

[0072] S2.3: Add silane coupling agent KH550 to 60% ethanol solution at a volume ratio of 1:99, and adjust the pH to 4.5 with acetic acid. Then add ultrasonically cleaned and dried black phosphorus nanosheets at a solid-liquid ratio of 1g:25mL, ultrasonically disperse for 15min, and heat at 55℃ for 2.5h. Filter to obtain aminated black phosphorus nanosheets.

[0073] S2.4: Dissolve the above polymer modifier in Tris buffer at a solid-liquid ratio of 1g:65mL, then add the above aminated black phosphorus nanosheets at a solid-liquid ratio of 1g:190mL. After ultrasonic dispersion for 35min, add 0.1mol / L sodium hydroxide solution to adjust the pH to 7.5, and heat and stir at 55℃ for 11h under nitrogen protection. After centrifugation, washing and vacuum drying, the coated modified black phosphorus nanosheets are obtained.

[0074] S3: Preparation of modified hollow glass microspheres

[0075] S3.1: Hollow glass microspheres with a particle size of 10 μm were added to a 0.25 mol / L sodium hydroxide solution at a solid-liquid ratio of 1 g: 35 mL. The solution was heated and stirred at 80 °C for 1.5 h. After filtration and washing until neutral, pretreated microspheres were obtained.

[0076] S3.2: The pretreated microspheres were ultrasonically mixed with deionized water and anhydrous ethanol at a mass ratio of 1:2:9, and then silane coupling agent KH550 was added. The mixture was stirred at 75°C for 2.5 h. After filtration, washing and vacuum drying, aminated microspheres were obtained. The mass ratio of silane coupling agent KH550 to hollow glass microspheres was 1:95.

[0077] S3.3: The above-mentioned aminated microbeads were added to a mixed solvent at a solid-liquid ratio of 1g:35mL and ultrasonically dispersed to obtain a microbead dispersion. At the same time, hexamethylene diisocyanate trimer was dissolved in the mixed solvent at a solid-liquid ratio of 1g:15mL to obtain a hexamethylene diisocyanate trimer solution. The mixed solvent was prepared by mixing ethyl acetate, xylene, and butyl acetate in a mass ratio of 1.5:1:1.2.

[0078] S3.4: Add the above microbead dispersion to the above hexamethylene diisocyanate trimer solution at a volume ratio of 1:4, and stir for 3.5 h to obtain isocyanate modified microbead dispersion;

[0079] S3.5: Dissolve JF-2X type FEVE fluorinated resin in a mixed solvent at a solid-liquid ratio of 1g:25mL, then add an equal volume of the above isocyanate modified microsphere dispersion, stir and react for 9h, and obtain modified hollow glass microspheres after filtration, washing and drying.

[0080] S4: Preparation of epoxy resin coatings

[0081] 95 parts by weight of bisphenol A type epoxy resin were added to 97.5 parts by weight of propylene glycol and stirred thoroughly to dissolve. Then, 34 parts by weight of the above-mentioned flame retardant additive, 11 parts by weight of coated modified black phosphorus nanosheets and 25 parts by weight of modified hollow glass microspheres were added and stirred thoroughly. Then, 25 parts by weight of polyetheramine modified curing agent, 1.5 parts by weight of silicone defoamer, 1.5 parts by weight of silicone leveling agent and 4 parts by weight of ESO plasticizer were added and stirred thoroughly to obtain epoxy resin coating.

[0082] Example 3

[0083] A preparation process for an aging-resistant and flame-retardant epoxy resin coating, such as... Figure 1 As shown, it includes the following steps:

[0084] S1: Preparation of flame retardant additives

[0085] S1.1: 3,4-Dihydroxybenzaldehyde and 2-amino-4-methylphenol were added to anhydrous ethanol at a solid-liquid ratio of 1.4g:1g:30mL, and glacial acetic acid was added to adjust the pH to 5. The mixture was then heated to reflux at 80℃ for 10h. After cooling to room temperature, the mixture was filtered, washed and vacuum dried to obtain the intermediate.

[0086] S1.2: Add the above intermediate to anhydrous tetrahydrofuran at a solid-liquid ratio of 1g:20mL, stir thoroughly to dissolve, then add triethylamine, stir thoroughly to disperse, and obtain a mixed solution, wherein the molar ratio of triethylamine to intermediate is 2.6:1;

[0087] S1.3: Hexachlorocyclotriphosphazene was dissolved in anhydrous tetrahydrofuran at a solid-liquid ratio of 1g:10mL to prepare a hexachlorocyclotriphosphazene solution. The above mixed solution was then placed in an ice-water bath at 5°C, and the hexachlorocyclotriphosphazene solution was added dropwise while stirring. After the addition was completed, the mixture was heated and stirred at 50°C for 16h. Then, the tetrahydrofuran was removed by vacuum distillation, and the mixture was washed with deionized water until neutral and recrystallized from methanol to obtain a flame retardant additive. The molar ratio of hexachlorocyclotriphosphazene to the intermediate was 1:2.8.

[0088] S2: Preparation of coated modified black phosphorus nanosheets

[0089] S2.1: Alkali lignin was added to a 20% sodium hydroxide solution at a solid-liquid ratio of 1g:5mL, stirred thoroughly to dissolve, and then 3-chloro-2-hydroxypropyltrimethylammonium chloride was added. The mixture was heated and stirred at 90℃ for 4 hours. After dialysis purification and freeze-drying, quaternized alkali lignin was obtained, wherein the molar ratio of 3-chloro-2-hydroxypropyltrimethylammonium chloride to alkali lignin was 1.4:1.

[0090] S2.2: The above-mentioned quaternized alkali lignin was added to Tris buffer solution with pH 9 at a solid-liquid ratio of 1g:30mL, stirred thoroughly to dissolve, then dopamine hydrochloride, hydrogen peroxide and ammonium persulfate were added, and the mixture was stirred and reacted for 24h. After dialysis purification and freeze drying, the polymer modifier was obtained. The molar ratio of quaternized alkali lignin to dopamine hydrochloride was 4:1, the volume ratio of hydrogen peroxide to Tris buffer solution was 1:140, and the mass ratio of ammonium persulfate to quaternized alkali lignin was 1:100.

[0091] S2.3: Add silane coupling agent KH550 to 60% ethanol solution at a volume ratio of 1:100, and add acetic acid to adjust the pH to 5. Then add ultrasonically cleaned and dried black phosphorus nanosheets at a solid-liquid ratio of 1g:30mL, ultrasonically disperse for 20min, and heat at 60℃ for 3h. Filter to obtain aminated black phosphorus nanosheets.

[0092] S2.4: Dissolve the above polymer modifier in Tris buffer at a solid-liquid ratio of 1g:70mL, then add the above aminated black phosphorus nanosheets at a solid-liquid ratio of 1g:200mL. After ultrasonic dispersion for 40min, add 0.1mol / L sodium hydroxide solution to adjust the pH to 8, and heat and stir at 60℃ for 12h under nitrogen protection. After centrifugation, washing and vacuum drying, the coated modified black phosphorus nanosheets are obtained.

[0093] S3: Preparation of modified hollow glass microspheres

[0094] S3.1: Hollow glass microspheres with a particle size of 10 μm were added to a 0.3 mol / L sodium hydroxide solution at a solid-liquid ratio of 1 g: 40 mL. The solution was heated and stirred at 85 °C for 2 h. After filtration and washing until neutral, pretreated microspheres were obtained.

[0095] S3.2: The pretreated microspheres were ultrasonically mixed with deionized water and anhydrous ethanol at a mass ratio of 1:3:10, and then silane coupling agent KH550 was added. The mixture was stirred at 80°C for 3 hours. After filtration, washing and vacuum drying, aminated microspheres were obtained. The mass ratio of silane coupling agent KH550 to hollow glass microspheres was 1:100.

[0096] S3.3: The above-mentioned aminated microbeads were added to a mixed solvent at a solid-liquid ratio of 1g:40mL and ultrasonically dispersed to obtain a microbead dispersion. At the same time, hexamethylene diisocyanate trimer was dissolved in the mixed solvent at a solid-liquid ratio of 1g:20mL to obtain a hexamethylene diisocyanate trimer solution. The mixed solvent was prepared by mixing ethyl acetate, xylene and butyl acetate in a mass ratio of 2:1:1.3.

[0097] S3.4: Add the above microbead dispersion to the above hexamethylene diisocyanate trimer solution at a volume ratio of 1:5, stir and react for 4 hours to obtain isocyanate modified microbead dispersion;

[0098] S3.5: Dissolve JF-2X type FEVE fluorinated resin in a mixed solvent at a solid-liquid ratio of 1g:30mL, then add an equal volume of the above isocyanate modified microsphere dispersion, stir and react for 10h, and obtain modified hollow glass microspheres after filtration, washing and drying.

[0099] S4: Preparation of epoxy resin coatings

[0100] 100 parts by weight of bisphenol A type epoxy resin were added to 100 parts by weight of acetone and stirred thoroughly to dissolve. Then, 36 parts by weight of the above-mentioned flame retardant additive, 12 parts by weight of coated modified black phosphorus nanosheets and 30 parts by weight of modified hollow glass microspheres were added and stirred thoroughly. After mixing thoroughly, 30 parts by weight of fatty amine modified curing agent, 2 parts by weight of organosilicon defoamer, 2 parts by weight of organosilicon leveling agent and 5 parts by weight of stearic acid were added and mixed thoroughly to obtain epoxy resin coating.

[0101] Comparative Example 1

[0102] The difference between Comparative Example 1 and Example 1 is that step S1 is removed, and the flame retardant additive in step S4 is also removed.

[0103] Comparative Example 2

[0104] The difference between Comparative Example 2 and Example 1 is that the flame retardant additive in step S4 is replaced with an equal amount of triphenyl phosphate.

[0105] Comparative Example 3

[0106] The difference between Comparative Example 3 and Example 1 is that step S2 is removed, and the coated modified black phosphorus nanosheets in step S4 are replaced with an equal amount of black phosphorus nanosheets.

[0107] Comparative Example 4

[0108] The difference between Comparative Example 4 and Example 1 is that steps S2.1-2.2 and S2.4 are removed, and the coated modified black phosphorus nanosheets in step S4 are replaced with an equal amount of aminated black phosphorus nanosheets obtained in step S2.3.

[0109] Comparative Example 5

[0110] The difference between Comparative Example 5 and Example 1 is that step S3 is removed, and the modified neutral glass microspheres in step S4 are replaced with an equal amount of hollow glass microspheres.

[0111] Comparative Example 6

[0112] The difference between Comparative Example 6 and Example 1 is that the coated modified black phosphorus nanosheets in step S4 are replaced with an equal amount of modified hollow glass microspheres.

[0113] Comparative Example 7

[0114] The difference between Comparative Example 7 and Example 1 is that the modified hollow glass microspheres in step S4 are replaced with an equal amount of coated modified black phosphorus nanosheets.

[0115] Test case

[0116] Test 1: The epoxy resin coatings prepared in Examples 1-3 and Comparative Examples 1-2 were uniformly coated on steel plates. After curing, it was observed whether white spots or powdery substances were precipitated on the surface of each coating. The limiting oxygen index was tested using an oxygen index meter. The results are shown in Table 1.

[0117] Table 1: Test Results of Limiting Oxygen Index and Flammability Rating of Coating

[0118]

[0119] As shown in Table 1, in Comparative Example 1, the limiting oxygen index of the coating without the addition of flame retardant additives was significantly lower than that of Example 1, indicating that the addition of flame retardant additives can effectively improve the flame retardant performance of epoxy resin coatings. In addition, in Comparative Example 2, after replacing the flame retardant additives with additive-type organophosphorus flame retardants, white powder was precipitated on the coating surface, indicating that it had poor compatibility with the epoxy resin matrix. However, in Examples 1-3, no precipitation was observed on the coating surface, indicating that the flame retardant additives of the present invention have good compatibility with the epoxy resin matrix.

[0120] Test 2: The epoxy resin coatings prepared in Examples 1-3 and Comparative Example 1 were poured into molds and cured to form cured products. The tensile properties were then tested according to GB / T 1040.1-2006. The results are shown in Table 2.

[0121] Table 2: Tensile property test results

[0122]

[0123] As shown in Table 2, the tensile strength of the epoxy resin coating cured in Comparative Example 1 without the addition of flame retardant additives was significantly lower than that in Example 1. This shows that flame retardant additives help improve the mechanical properties of epoxy resin coatings.

[0124] Test 3: The epoxy resin coatings prepared in Examples 1-3 and Comparative Examples 3-4 were poured into molds for curing and irradiated with a 300W ultraviolet lamp for 360 hours. The color difference value was then measured using a CM-2300D colorimeter. The results are shown in Table 3.

[0125] Table 3: Color Difference Value Test Results

[0126]

[0127] As shown in Table 3, in Comparative Example 3, the UV irradiation color difference value of the epoxy resin coating obtained without modifying the black phosphorus nanosheets was much lower than that of Example 1. In Comparative Example 4, the UV aging color difference value of the epoxy resin coating obtained after replacing the polymer modifier-modified black phosphorus nanosheets with silane coupling agent-modified nanosheets was also lower than that of Example 1. It can be seen that surface coating modification of black phosphorus nanosheets with polymer modifiers can improve the UV aging resistance of the coating.

[0128] Furthermore, in Comparative Example 5, the UV irradiation color difference value of the epoxy resin coating obtained without surface modification of the hollow glass microspheres was much lower than that of Example 1. It can be seen that modifying the hollow glass microspheres with fluoropolymers can effectively improve the UV aging resistance of the epoxy resin coating.

[0129] Test 4: The epoxy resin coatings prepared in Examples 1-3 and Comparative Examples 6-7 were coated on galvanized sheets. After curing at room temperature for 2 days, the coatings were heat-aged at 100°C for 30 days in a heat aging test chamber. The results are shown in Table 4.

[0130] Table 4: Results of thermo-oxidative aging test

[0131]

[0132] As shown in Table 4, when only modified hollow glass microspheres or coated modified black phosphorus nanosheets were added in Comparative Examples 6 and 7, the epoxy resin coatings formed showed yellowing after 30 days of thermo-oxidative aging. This shows that the combination of coated modified black phosphorus nanosheets and modified hollow glass microspheres can synergistically slow down the thermo-oxidative aging rate and improve the thermo-oxidative aging resistance of epoxy resin coatings.

[0133] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A preparation process for an aging-resistant and flame-retardant epoxy resin coating, characterized in that, Includes the following steps: S1: Preparation of flame retardant additives S1.1: Add 3,4-dihydroxybenzaldehyde and 2-amino-4-methylphenol to anhydrous ethanol at a solid-liquid ratio of (1.2-1.4) g: 1 g: (20-30) mL, then add glacial acetic acid to adjust the pH to 4-5, and heat to reflux at 70-80℃ for 8-12 h. After post-treatment, the intermediate is obtained. S1.2: Add the above intermediate to anhydrous tetrahydrofuran at a solid-liquid ratio of 1g:(10-20)mL, stir thoroughly to dissolve, then add triethylamine, stir thoroughly to disperse, and obtain a mixed solution; S1.3: Dissolve hexachlorocyclotriphosphazene in anhydrous tetrahydrofuran at a solid-liquid ratio of 1g:(8-10)mL to prepare a hexachlorocyclotriphosphazene solution. Then place the above mixed solution in an ice-water bath at 3-5℃ and add the hexachlorocyclotriphosphazene solution dropwise while stirring. Then heat and stir the reaction at 40-50℃ for 12-16h. Subsequently, remove the tetrahydrofuran by vacuum distillation, and then wash and recrystallize to obtain the flame retardant additive. S2: Preparation of coated modified black phosphorus nanosheets S2.1: Add alkali lignin to a 20% sodium hydroxide solution at a solid-liquid ratio of 1g:(3-5)mL, stir thoroughly to dissolve, then add 3-chloro-2-hydroxypropyltrimethylammonium chloride, and heat and stir at 80-90℃ for 3-4h. After dialysis and freeze-drying, quaternized alkali lignin is obtained. S2.2: Dissolve the above-mentioned quaternized alkali lignin in Tris buffer solution with pH 8-9 at a solid-liquid ratio of 1g:(20-30)mL, then add dopamine hydrochloride, hydrogen peroxide and ammonium persulfate, and stir for 20-24h. After dialysis and freeze drying, the polymer modifier is obtained. S2.3: Add silane coupling agent KH550 to 60% ethanol solution at a volume ratio of 1:(98-100), and adjust the pH to 4-5 with acetic acid. Then add ultrasonically cleaned and dried black phosphorus nanosheets at a solid-liquid ratio of 1g:(20-30)mL, disperse ultrasonically for 10-20min, and heat at 50-60℃ for 2-3h. Filter to obtain aminated black phosphorus nanosheets. S2.4: Dissolve the above polymer modifier in Tris buffer at a solid-liquid ratio of 1g:(60-70)mL, then add the above aminated black phosphorus nanosheets at a solid-liquid ratio of 1g:(180-200)mL. After ultrasonic dispersion for 30-40min, add 0.1mol / L sodium hydroxide solution to adjust the pH to 7-8, and heat and stir the reaction at 50-60℃ for 10-12h under nitrogen protection. After post-treatment, coated modified black phosphorus nanosheets are obtained. S3: Preparation of modified hollow glass microspheres The pre-treated hollow glass microspheres were aminated, then reacted with hexamethylene diisocyanate trimer, and finally a fluoropolymer was added to react and obtain modified hollow glass microspheres. S4: Preparation of epoxy resin coatings Add 90-100 parts by weight of bisphenol A type epoxy resin to 95-100 parts by weight of organic solvent and stir thoroughly to dissolve. Then add 32-36 parts by weight of the above-mentioned flame retardant additive, 10-12 parts by weight of coated modified black phosphorus nanosheets and 20-30 parts by weight of modified hollow glass microspheres. After stirring thoroughly, add 20-30 parts by weight of curing agent, 1-2 parts by weight of defoamer, 1-2 parts by weight of leveling agent and 3-5 parts by weight of plasticizer. After thorough mixing, the epoxy resin coating is obtained.

2. The preparation process of an aging-resistant and flame-retardant epoxy resin coating according to claim 1, characterized in that, S3 specifically includes the following steps: S3.1: The hollow glass microspheres with a particle size of 10 μm after alkalization pretreatment are ultrasonically mixed with deionized water and anhydrous ethanol at a mass ratio of 1:(1-3):(8-10). Then, silane coupling agent KH550 is added and the mixture is stirred at 70-80℃ for 2-3 hours. After post-treatment, aminated microspheres are obtained. S3.2: Add the above-mentioned aminated microbeads to the mixed solvent at a solid-liquid ratio of 1g:(30-40)mL and disperse by ultrasonication to obtain a microbead dispersion. At the same time, dissolve the hexamethylene diisocyanate trimer in the mixed solvent at a solid-liquid ratio of 1g:(10-20)mL to obtain a hexamethylene diisocyanate trimer solution. S3.3: Add the above microbead dispersion to the above hexamethylene diisocyanate trimer solution at a volume ratio of 1:(3-5), stir and react for 3-4 hours to obtain isocyanate modified microbead dispersion; S3.4: Dissolve the fluoropolymer in a mixed solvent at a solid-liquid ratio of 1g:(20-30)mL, then add an equal volume of the above isocyanate-modified microsphere dispersion, stir for 8-10h, and then filter, wash and dry to obtain modified hollow glass microspheres.

3. The preparation process of an aging-resistant and flame-retardant epoxy resin coating according to claim 1, characterized in that, The molar ratio of triethylamine to the intermediate is (2.4-2.6):1, and the molar ratio of hexachlorocyclotriphosphazene to the intermediate is 1:(2.4-2.8).

4. The preparation process of an aging-resistant and flame-retardant epoxy resin coating according to claim 1, characterized in that, The molar ratio of 3-chloro-2-hydroxypropyltrimethylammonium chloride to alkali lignin is (1.2-1.4):1, and the molar ratio of quaternized alkali lignin to dopamine hydrochloride is (2-4):

1.

5. The preparation process of an aging-resistant and flame-retardant epoxy resin coating according to claim 1, characterized in that, The volume ratio of hydrogen peroxide to Tris buffer is 1:(120-140), and the mass ratio of ammonium persulfate to quaternized alkali lignin is 1:(90-100).

6. The preparation process of an aging-resistant and flame-retardant epoxy resin coating according to claim 2, characterized in that, The mass ratio of silane coupling agent KH550 to hollow glass microspheres is 1:(90-100), and the mixed solvent is prepared by mixing ethyl acetate, xylene and butyl acetate in a mass ratio of (1-2):1:(1.1-1.3).

7. The preparation process of an aging-resistant and flame-retardant epoxy resin coating according to claim 1, characterized in that, The curing agent is at least one of alicyclic amine modified curing agent, polyether amine modified curing agent, and fatty amine modified curing agent; the defoamer is an organosilicon defoamer; the leveling agent is an organosilicon leveling agent; at least one of DOS plasticizer, ESO plasticizer, and stearic acid; and the organic solvent is at least one of xylene, propylene glycol, acetone, butanone, and ethyl acetate.

8. An aging-resistant and flame-retardant epoxy resin coating, characterized in that, It is prepared by the preparation process of an aging-resistant and flame-retardant epoxy resin coating as described in any one of claims 1-7.

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