Anti-aging flame-retardant epoxy resin coating and preparation process thereof

Abstract

The invention provides an anti-aging flame-retardant epoxy resin coating and a preparation process thereof, and belongs to the technical field of coating preparation. The preparation process comprises the following steps: preparing the flame-retardant additive; preparing a coated modified black phosphorus nanosheet; preparing modified hollow glass beads; preparing the epoxy resin coating. The preparation method comprises the following steps: dissolving 3, 4-dihydroxy benzaldehyde and 2-amino-4-methylphenol in absolute ethyl alcohol, carrying out a heating reflux reaction, carrying out dehydration condensation on an aldehyde group in the 3, 4-dihydroxy benzaldehyde and an amino group in the 2-amino-4-methylphenol to generate an imine bond-containing intermediate, respectively dissolving the intermediate and phosphonitrilic chloride trimer, and carrying out a reaction to obtain the phosphonitrilic chloride trimer. The preparation method comprises the following steps: firstly, adding phosphonitrilic chloride into an intermediate, then mixing for reaction, enabling phenolic hydroxyl groups in the intermediate and phosphonitrilic chloride trimer to be subjected to nucleophilic substitution reaction to generate the flame-retardant additive containing phosphorus and a Schiff base structure, and the flame-retardant additive has relatively good compatibility with an epoxy resin matrix, is not easy to separate out and can effectively improve the flame-retardant property of the epoxy resin coating.

Description

Technical Field

[0001] The present invention relates to the technical field of coating preparation, and particularly relates to an anti-aging and flame-retardant epoxy resin coating and a preparation process thereof. Background Art

[0002] Epoxy resin coatings are widely used in fields such as construction, transportation, chemical industry, and electronics due to their excellent adhesion, corrosion resistance, and mechanical properties. However, when traditional epoxy resin coatings are used outdoors, they are easily affected by ultraviolet radiation and environmental factors, resulting in coating aging, such as yellowing, powdering, and cracking, which seriously affects their service life. In addition, epoxy resin itself is a flammable material, and there is a fire hazard during use. Therefore, it is necessary to add a flame retardant to improve its flame retardant performance.

[0003] Organophosphorus compounds can endow epoxy resin-based coatings with flame retardant properties. Currently, most phosphorus-containing flame retardants provide flame retardant activity through a combination of gas-phase reactions and condensed-phase reactions, polymer carbonization promotion, and charring effects. However, most organophosphorus-based flame retardants usually have a relatively small molecular weight and a large chemical structure difference from epoxy resin, resulting in a weak interaction between the two, poor compatibility with the epoxy resin matrix, and easy exudation, thus affecting their flame retardant modification effect on epoxy resin coatings. Moreover, an excessive addition amount is likely to reduce the mechanical properties of the resin matrix, leading to the deterioration of the physical and mechanical properties of the material.

[0004] Black phosphorus nanosheets have typical two-dimensional nanomaterial characteristics, and their honeycomb layer stacking structure can reflect and scatter ultraviolet light. Adding them to epoxy resin coatings is expected to reduce the direct irradiation of ultraviolet light on epoxy resin, playing a physical shielding role to improve the anti-ultraviolet aging performance of the coatings. However, there is a strong van der Waals force between the layers of black phosphorus nanosheets, which makes black phosphorus nanosheets prone to agglomeration in the epoxy resin matrix, thus reducing their dispersibility. Moreover, the interfacial bonding force between black phosphorus nanosheets and the epoxy resin matrix is weak, which makes black phosphorus nanosheets easy to detach from the matrix during the curing and use of epoxy resin, resulting in a decrease in the anti-ultraviolet aging performance of the coating.

[0005] Based on this, it is necessary to propose an anti-aging and flame-retardant epoxy resin coating and a preparation process thereof, in which the flame retardant has good compatibility with the epoxy resin matrix, is not easy to precipitate, and can improve the dispersibility of black phosphorus nanosheets to extend the service life of the coating. Summary of the Invention

[0006] Aiming at the deficiencies existing in the prior art, the purpose of the present invention is to provide an anti-aging and flame-retardant epoxy resin coating and a preparation process thereof.

[0007] A preparation process of an anti-aging and flame-retardant epoxy resin coating includes the following steps: S1: Prepare a flame retardant additive The flame retardant additive is prepared using 3,4-dihydroxybenzaldehyde, 2-amino-4-methylphenol and hexachlorocyclotriphosphazene as raw materials; S2: Preparation of coated modified black phosphorus nanosheets The alkali lignin is quaternized and reacted with dopamine hydrochloride to prepare a polymer modifier, and then the aminated black phosphorus nanosheets are modified to obtain coated modified black phosphorus nanosheets; S3: Preparation of modified hollow glass microspheres The hollow glass microspheres after alkalization pretreatment are amino-treated, and then reacted with hexamethylene diisocyanate trimer, and finally a fluorine-containing polymer is added to react to obtain modified hollow glass microspheres; S4: Preparation of epoxy resin coating 90-100 parts by mass of bisphenol A epoxy resin are added to 95-100 parts by mass of an organic solvent, and the mixture is fully stirred and dissolved. Then, 32-36 parts by mass of the flame retardant additive, 10-12 parts by mass of coated modified black phosphorus nanosheets and 20-30 parts by mass of modified hollow glass microspheres are added, and the mixture is fully stirred and mixed. Then, 20-30 parts by mass of a curing agent, 1-2 parts by mass of a defoaming agent, 1-2 parts by mass of a leveling agent and 3-5 parts by mass of a plasticizer are added, and the mixture is fully mixed to obtain an epoxy resin coating.

[0008] Furthermore, S1 specifically includes the following steps: 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, add glacial acetic acid to adjust the pH to 4-5, and heat under reflux at 70-80 ° C for 8-12 h. After cooling to room temperature, filter, wash and vacuum dry to obtain an intermediate; S1.2: Add the above intermediate into anhydrous tetrahydrofuran at a solid-liquid ratio of 1 g: (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. Place the mixed solution in a 3-5℃ ice water bath and drop the hexachlorocyclotriphosphazene solution while stirring. After the addition is complete, heat and stir at 40-50℃ for 12-16h. Then, distill under reduced pressure to remove tetrahydrofuran, wash with deionized water until neutral, and recrystallize with methanol to obtain a flame retardant additive.

[0009] Furthermore, S2 specifically includes the following steps: S2.1: Add alkali lignin into a 20% sodium hydroxide solution according to a solid-liquid ratio of 1 g : (3 - 5) mL, stir well to dissolve, then add 3-chloro-2-hydroxypropyltrimethylammonium chloride, and heat and stir for reaction at 80 - 90 °C for 3 - 4 h. After dialysis purification and freeze-drying, quaternized alkali lignin is obtained; S2.2: Add the above quaternized alkali lignin into a Tris buffer solution with a pH of 8 - 9 according to a solid-liquid ratio of 1 g : (20 - 30) mL, stir well to dissolve, then add dopamine hydrochloride, hydrogen peroxide and ammonium persulfate, and stir for reaction for 20 - 24 h. After dialysis purification and freeze-drying, a polymer modifier is obtained; S2.3: Add silane coupling agent KH550 into a 60% ethanol solution according to a volume ratio of 1 : (98 - 100), add acetic acid to adjust the pH to 4 - 5, then add ultrasonically cleaned and dried black phosphorus nanosheets according to a solid-liquid ratio of 1 g : (20 - 30) mL, ultrasonically disperse for 10 - 20 min, and heat and react at 50 - 60 °C for 2 - 3 h, filter to obtain amino-functionalized black phosphorus nanosheets; S2.4: Dissolve the above polymer modifier in a Tris buffer solution according to a solid-liquid ratio of 1 g : (60 - 70) mL, then add the above amino-functionalized black phosphorus nanosheets according to a solid-liquid ratio of 1 g : (180 - 200) mL. After ultrasonically dispersing for 30 - 40 min, add 0.1 mol / L sodium hydroxide solution to adjust the pH to 7 - 8, and under nitrogen protection, heat and stir for reaction at 50 - 60 °C for 10 - 12 h. After centrifugal separation, washing and vacuum drying, coated and modified black phosphorus nanosheets are obtained.

[0010] Further, S3 specifically includes the following steps: S3.1: Add hollow glass microspheres with a particle size of 10 μm into a 0.2 - 0.3 mol / L sodium hydroxide solution according to a solid-liquid ratio of 1 g : (30 - 40) mL, heat and stir at 75 - 85 °C for 1 - 2 h. After suction filtration and washing until neutral, pretreated microspheres are obtained; S3.2: Ultrasonically mix the above pretreated microspheres with deionized water and absolute ethanol according to a mass ratio of 1 : (1 - 3) : (8 - 10), then add silane coupling agent KH550, and stir for reaction at 70 - 80 °C for 2 - 3 h. After filtration, washing and vacuum drying, amino-functionalized microspheres are obtained; S3.3: Add the above amino-functionalized microspheres into a mixed solvent according to a solid-liquid ratio of 1 g : (30 - 40) mL and ultrasonically disperse to obtain a microsphere dispersion. At the same time, dissolve hexamethylene diisocyanate trimer in the mixed solvent according to a solid-liquid ratio of 1 g : (10 - 20) mL to obtain a hexamethylene diisocyanate trimer solution; S3.4: Add the above microbead dispersion into the above hexamethylene diisocyanate trimer solution at a volume ratio of 1:(3 - 5), and stir and react for 3 - 4 h to obtain an isocyanate-modified microbead dispersion; S3.5: Dissolve the fluoropolymer in the mixed solvent at a solid-liquid ratio of 1 g:(20 - 30) mL, then add an equal volume of the above isocyanate-modified microbead dispersion, stir and react for 8 - 10 h, and obtain modified hollow glass microspheres after filtration, washing and drying. Among them, the fluoropolymer is a copolymer with alternating arrangement of chlorotrifluoroethylene and vinyl ester.

[0011] Further, 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).

[0012] Further, 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.

[0013] Further, the volume ratio of hydrogen peroxide to Tris buffer solution is 1:(120 - 140), and the mass ratio of ammonium persulfate to quaternized alkali lignin is 1:(90 - 100).

[0014] Further, 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 according to a mass ratio of (1 - 2):1:(1.1 - 1.3).

[0015] Further, the curing agent is at least one of alicyclic amine-modified curing agent, polyether amine-modified curing agent, and aliphatic amine-modified curing agent; the defoaming agent is an organosilicon defoaming agent; the leveling agent is an organosilicon leveling agent; at least one of DOS plasticizer, ESO plasticizer, and stearic acid; the organic solvent is at least one of xylene, propylene glycol, acetone, butanone and ethyl acetate.

[0016] Further, an anti-aging and flame-retardant epoxy resin coating is prepared by the preparation process of an anti-aging and flame-retardant epoxy resin coating described in any one of the above.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: 1. In the present invention, 3,4-dihydroxybenzaldehyde and 2-amino-4-methylphenol are first dissolved in absolute ethanol and subjected to heating under reflux. The aldehyde group in 3,4-dihydroxybenzaldehyde undergoes dehydration condensation with the amino group of 2-amino-4-methylphenol to form an intermediate containing an imine bond. Then, the intermediate and hexachlorocyclotriphosphazene are separately dissolved and then mixed for reaction, so that the phenolic hydroxyl group in the intermediate undergoes a nucleophilic substitution reaction with hexachlorocyclotriphosphazene to form a flame retardant additive containing a phosphorus element and a Schiff base structure. After adding this flame retardant additive to epoxy resin, on the one hand, the phenolic hydroxyl group in the flame retardant additive can undergo a ring-opening reaction with the epoxy group of epoxy resin during the curing process to form a covalent bond, and the amino group can act as a catalyst or crosslinking point for the curing reaction of epoxy resin, enhancing the chemical bonding between the flame retardant additive and epoxy resin. On the other hand, the phosphorus-nitrogen bond and phosphorus-oxygen bond introduced by hexachlorocyclotriphosphazene have strong polarity and are similar to the polarity of the ether bond and hydroxyl group of epoxy resin, which can reduce phase separation. Therefore, this flame retardant additive has good compatibility with the epoxy resin matrix and is not easily precipitated, and can effectively improve the flame retardant performance of the epoxy resin coating. In addition, the chemical bonding between the flame retardant additive and the epoxy resin matrix also helps to improve the mechanical properties of the epoxy resin coating.

[0018] 2. In the present invention, 3-chloro-2-hydroxypropyltrimethylammonium chloride is added for reaction to quaternize alkali lignin. Then, the quaternized alkali lignin is dissolved in Tris buffer solution, and dopamine hydrochloride, hydrogen peroxide, and ammonium persulfate are added for reaction to prepare a polymer modifier obtained by graft polymerization of polydopamine and quaternized alkali lignin. Then, the amino-functionalized black phosphorus nanosheets are modified with this polymer modifier. After the polymer modifier coats the surface of the black phosphorus nanosheets, due to the compatibility of the hydrophobic segment and polar group of the polymer modifier with the hydrophobic region and polar group of epoxy resin respectively, molecular-level dispersion is achieved, thereby effectively improving the dispersion of black phosphorus nanosheets in epoxy resin and reducing aggregation. In addition, since polydopamine in the polymer modifier can absorb ultraviolet light and quaternized alkali lignin can inhibit the oxidative degradation of epoxy resin by scavenging free radicals, after coating and modifying the black phosphorus nanosheets with this polymer modifier and then adding them to the epoxy resin coating, the anti-ultraviolet aging performance of the epoxy resin can be further improved, thereby effectively extending the service life of the epoxy resin coating.

[0019] 3. In the present invention, the hollow glass microspheres are first subjected to surface pretreatment, and their surfaces are aminated using a silane coupling agent. Then, they are mixed with hexamethylene diisocyanate trimer for a nucleophilic addition reaction to introduce isocyanate groups on the surfaces of the hollow glass microspheres. Finally, they are reacted with a fluoropolymer, and the fluoropolymer is grafted onto the surfaces of the hollow glass microspheres through a chemical reaction to modify the hollow glass microspheres. After forming a coating layer, it can not only effectively improve the compatibility between the hollow glass microspheres and the epoxy resin matrix, but also, due to the relatively high bond energy of the C-F bond in the fluoropolymer, after adding the modified hollow glass microspheres to the epoxy resin coating, it can reduce the degree of ultraviolet light irradiation on the epoxy resin matrix, thereby achieving the effect of improving the anti-ultraviolet aging performance of the epoxy resin coating. In addition, after adding the modified hollow glass microspheres and the coated and modified black phosphorus nanosheets to the epoxy resin coating together, the lamellar structure of the black phosphorus nanosheets can form a barrier layer to inhibit the penetration 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 rate of thermal oxygen aging and improve the anti-thermal oxygen aging performance of the epoxy resin coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings incorporated herein and constituting a part of the specification illustrate embodiments of the present disclosure and, together with the specification, are further used to explain the principles of the present disclosure and enable those skilled in the relevant art to implement and use the present disclosure.

[0021] Figure 1 It is a process flow chart of the preparation of the anti-aging and flame-retardant epoxy resin coating adopted in the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The following describes in detail an anti-aging and flame-retardant epoxy resin coating and its preparation process provided by the present invention with reference to the drawings and specific embodiments.

[0023] Example 1 A preparation process of an anti-aging and flame-retardant epoxy resin coating, as Figure 1 shown, includes the following steps: S1: Prepare a flame retardant additive S1.1: Add 3,4-dihydroxybenzaldehyde and 2-amino-4-methylphenol to absolute ethanol according to a solid-liquid ratio of 1.2 g: 1 g: 20 mL, then add glacial acetic acid to adjust the pH to 4, and heat under reflux at 70 °C for 8 h. After cooling to room temperature, filter, wash, and vacuum dry to obtain an intermediate; S1.2: Add the above intermediate to absolute tetrahydrofuran according to a solid-liquid ratio of 1 g: 10 mL, stir well to dissolve, then add triethylamine and stir well to disperse to obtain a mixed solution, where the molar ratio of triethylamine to the intermediate is 2.4: 1; S1.3: Dissolve hexachlorocyclotriphosphazene in anhydrous tetrahydrofuran at a solid-liquid ratio of 1g:8mL to prepare a hexachlorocyclotriphosphazene solution, then place the mixed solution in a 3°C ice-water bath, and dropwise add the hexachlorocyclotriphosphazene solution while stirring. After the dropwise addition is completed, heat and stir at 40°C for 12h, then distill under reduced pressure to remove tetrahydrofuran, then wash with deionized water until neutral and recrystallize with methanol to obtain a flame retardant additive, wherein the molar ratio of hexachlorocyclotriphosphazene to the intermediate is 1:2.4; 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 1 g:3 mL, stir and dissolve, then add 3-chloro-2-hydroxypropyltrimethylammonium chloride, and heat and stir at 80°C for 3-4 hours, dialysis purification and freeze-drying to obtain quaternized alkali lignin, wherein the molar ratio of 3-chloro-2-hydroxypropyltrimethylammonium chloride to alkali lignin is 1.2:1; S2.2: adding the above quaternized alkali lignin to a Tris buffer solution with a pH of 8 at a solid-liquid ratio of 1 g:20 mL, stirring and dissolving, then adding dopamine hydrochloride, hydrogen peroxide and ammonium persulfate, stirring and reacting for 20 hours, dialysis purification and freeze-drying to obtain a polymer modifier, wherein the molar ratio of quaternized alkali lignin to dopamine hydrochloride is 2:1, the volume ratio of hydrogen peroxide to Tris buffer is 1:120, and the mass ratio of ammonium persulfate to quaternized alkali lignin is 1:90; S2.3: Silane coupling agent KH550 was added to 60% ethanol solution at a volume ratio of 1:98, and acetic acid was added to adjust the pH to 4, and then black phosphorus nanosheets after ultrasonic cleaning and drying were added at a solid-liquid ratio of 1g:20mL, ultrasonic dispersion was performed for 10min, and the reaction was heated at 50°C for 2h, and filtered to obtain amino black phosphorus nanosheets; S2.4: The polymer modifier is dissolved in Tris buffer at a solid-liquid ratio of 1g:60mL, and then the amino-modified black phosphorus nanosheets are added at a solid-liquid ratio of 1g:180mL. After ultrasonic dispersion for 30min, 0.1mol / L sodium hydroxide solution is added to adjust the pH to 7, and the mixture is heated and stirred at 50°C for 10h under nitrogen protection. After centrifugal separation, washing and vacuum drying, the coated modified black phosphorus nanosheets are obtained; S3: Preparation of modified hollow glass microspheres S3.1: Add hollow glass microspheres with a particle size of 10 μm into 0.2 mol / L sodium hydroxide solution at a solid-liquid ratio of 1 g:30 mL, heat and stir at 75 °C for 1 h, filter and wash to neutrality to obtain pretreated microspheres; S3.2: ultrasonically mixing the pretreated microbeads with deionized water and anhydrous ethanol in a mass ratio of 1:1:8, adding silane coupling agent KH550, and stirring and reacting at 70°C for 2h, filtering, washing and vacuum drying to obtain aminated microbeads, wherein the mass ratio of silane coupling agent KH550 to hollow glass microbeads is 1:90; S3.3: adding the above-mentioned amino microbeads to a mixed solvent at a solid-liquid ratio of 1g:30mL, and dispersing by ultrasonication to obtain a microbead dispersion, and dissolving hexamethylene diisocyanate trimer in the mixed solvent at a solid-liquid ratio of 1g:10mL to obtain a hexamethylene diisocyanate trimer solution, wherein the mixed solvent is prepared by mixing ethyl acetate, xylene and butyl acetate at a mass ratio of 1:1:1.1; S3.4: adding the microbead dispersion to the hexamethylene diisocyanate trimer solution at a volume ratio of 1:3, stirring and reacting for 3 hours to obtain an isocyanate-modified microbead dispersion; S3.5: Dissolve JF-2X FEVE fluorine-containing resin in a mixed solvent at a solid-liquid ratio of 1g:20mL, add an equal volume of the above-mentioned isocyanate-modified microsphere dispersion, stir and react for 8h, filter, wash and dry to obtain modified hollow glass microspheres; S4: Preparation of epoxy resin coating 90 parts by mass of bisphenol A epoxy resin are added to 95 parts by mass of xylene, and the mixture is thoroughly stirred and dissolved. Then, 32 parts by mass of the above-mentioned flame retardant additive, 10 parts by mass of coated modified black phosphorus nanosheets and 20 parts by mass of modified hollow glass microspheres are added, and the mixture is thoroughly stirred and mixed. Then, 20 parts by mass of alicyclic amine modified curing agent, 1 part by mass of silicone defoaming agent, 1 part by mass of silicone leveling agent and 3 parts by mass of DOS plasticizer are added, and the mixture is thoroughly mixed to obtain an epoxy resin coating.

[0024] Example 2 A preparation process of an aging-resistant flame-retardant epoxy resin coating, such as Figure 1 As shown, the following steps are included: 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 1.3 g:1 g:25 mL, add glacial acetic acid to adjust the pH to 4.5, and heat under reflux at 75°C for 9 h. After cooling to room temperature, filter, wash and vacuum dry to obtain an intermediate; S1.2: Add the above intermediate into 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 the intermediate is 2.5:1; S1.3: Dissolve hexachlorocyclotriphosphazene in anhydrous tetrahydrofuran at a solid-liquid ratio of 1 g: 9 mL to prepare a hexachlorocyclotriphosphazene solution. Then, place the above mixed solution in an ice bath at 4 °C, and while stirring, dropwise add the hexachlorocyclotriphosphazene solution. After the addition is complete, heat and stir the reaction at 45 °C for 14 h. Subsequently, remove tetrahydrofuran by vacuum distillation, and then wash with deionized water until neutral and recrystallize with methanol to obtain a flame retardant additive. Among them, the molar ratio of hexachlorocyclotriphosphazene to the intermediate is 1:2.6; S2: Prepare coated and modified black phosphorus nanosheets S2.1: Add alkali lignin to a 20% sodium hydroxide solution at a solid-liquid ratio of 1 g: 4 mL, stir and dissolve thoroughly, then add 3-chloro-2-hydroxypropyltrimethylammonium chloride, and heat and stir the reaction at 85 °C for 3.5 h. After dialysis purification and freeze-drying, obtain quaternized alkali lignin. Among them, the molar ratio of 3-chloro-2-hydroxypropyltrimethylammonium chloride to alkali lignin is 1.3:1; S2.2: Add the above quaternized alkali lignin to a Tris buffer solution with a pH of 8.5 at a solid-liquid ratio of 1 g: 25 mL, stir and dissolve thoroughly, then add dopamine hydrochloride, hydrogen peroxide, and ammonium persulfate, and stir the reaction for 22 h. After dialysis purification and freeze-drying, obtain a polymer modifier. Among them, the molar ratio of quaternized alkali lignin to dopamine hydrochloride is 3:1, and the volume ratio of hydrogen peroxide to the Tris buffer solution is 1:130, and the mass ratio of ammonium persulfate to quaternized alkali lignin is 1:95; S2.3: Add silane coupling agent KH550 to a 60% ethanol solution at a volume ratio of 1:99, add acetic acid to adjust the pH to 4.5, then add ultrasonically cleaned and dried black phosphorus nanosheets at a solid-liquid ratio of 1 g: 25 mL, ultrasonically disperse for 15 min, and heat and react at 55 °C for 2.5 h, then filter to obtain amino-functionalized black phosphorus nanosheets; S2.4: Dissolve the above polymer modifier in Tris buffer solution at a solid-liquid ratio of 1 g: 65 mL, then add the above amino-functionalized black phosphorus nanosheets at a solid-liquid ratio of 1 g: 190 mL. After ultrasonically dispersing for 35 min, add 0.1 mol / L sodium hydroxide solution to adjust the pH to 7.5, and under nitrogen protection, heat and stir the reaction at 55 °C for 11 h. After centrifugal separation, washing, and vacuum drying, obtain coated and modified black phosphorus nanosheets; S3: Prepare modified hollow glass microspheres S3.1: Add hollow glass microspheres with a particle size of 10 μm to a 0.25 mol / L sodium hydroxide solution at a solid-liquid ratio of 1 g: 35 mL, heat and stir at 80 °C for 1.5 h. After suction filtration and washing until neutral, obtain pretreated microspheres; S3.2: ultrasonically mixing the pretreated microbeads with deionized water and anhydrous ethanol in a mass ratio of 1:2:9, adding silane coupling agent KH550, and stirring at 75°C for 2.5 hours, filtering, washing and vacuum drying to obtain amino microbeads, wherein the mass ratio of silane coupling agent KH550 to hollow glass microbeads is 1:95; S3.3: adding the above-mentioned amino microbeads to a mixed solvent at a solid-liquid ratio of 1g:35mL, and dispersing by ultrasonication to obtain a microbead dispersion, and dissolving hexamethylene diisocyanate trimer in the mixed solvent at a solid-liquid ratio of 1g:15mL to obtain a hexamethylene diisocyanate trimer solution, wherein the mixed solvent is prepared by mixing ethyl acetate, xylene and butyl acetate at a mass ratio of 1.5:1:1.2; S3.4: adding the microbead dispersion to the hexamethylene diisocyanate trimer solution at a volume ratio of 1:4, stirring and reacting for 3.5 hours to obtain an isocyanate-modified microbead dispersion; S3.5: Dissolve JF-2X FEVE fluorine-containing resin in a mixed solvent at a solid-liquid ratio of 1g:25mL, add an equal volume of the above-mentioned isocyanate-modified microsphere dispersion, stir and react for 9h, filter, wash and dry to obtain modified hollow glass microspheres; S4: Preparation of epoxy resin coating Add 95 parts by mass of bisphenol A epoxy resin to 97.5 parts by mass of propylene glycol, stir thoroughly to dissolve, add 34 parts by mass of the above-mentioned flame retardant additive, 11 parts by mass of coated modified black phosphorus nanosheets and 25 parts by mass of modified hollow glass microspheres, stir thoroughly to mix, then add 25 parts by mass of polyether amine modified curing agent, 1.5 parts by mass of silicone defoaming agent, 1.5 parts by mass of silicone leveling agent and 4 parts by mass of ESO plasticizer, mix thoroughly to obtain epoxy resin coating.

[0025] Example 3 A preparation process of an aging-resistant flame-retardant epoxy resin coating, such as Figure 1 As shown, the following steps are included: 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 1.4 g:1 g:30 mL, add glacial acetic acid to adjust the pH to 5, and heat under reflux at 80°C for 10 h. After cooling to room temperature, filter, wash and vacuum dry to obtain an intermediate; S1.2: Add the above intermediate into 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 the intermediate is 2.6:1; S1.3: Dissolve hexachlorocyclotriphosphazene in anhydrous tetrahydrofuran at a solid-liquid ratio of 1 g: 10 mL to prepare a hexachlorocyclotriphosphazene solution. Then place the above mixed solution in an ice bath at 5 °C, and while stirring, dropwise add the hexachlorocyclotriphosphazene solution. After the addition is complete, heat and stir the reaction at 50 °C for 16 h. Subsequently, remove tetrahydrofuran by vacuum distillation, and then wash with deionized water until neutral and recrystallize with methanol to obtain a flame retardant additive, where the molar ratio of hexachlorocyclotriphosphazene to the intermediate is 1:2.8; S2: Prepare coated and modified black phosphorus nanosheets S2.1: Add alkali lignin to a 20% sodium hydroxide solution at a solid-liquid ratio of 1 g: 5 mL, stir well to dissolve, then add 3-chloro-2-hydroxypropyltrimethylammonium chloride, and heat and stir the reaction at 90 °C for 4 h. After dialysis purification and freeze-drying, obtain quaternized alkali lignin, where the molar ratio of 3-chloro-2-hydroxypropyltrimethylammonium chloride to alkali lignin is 1.4:1; S2.2: Add the above quaternized alkali lignin to a Tris buffer solution with a pH of 9 at a solid-liquid ratio of 1 g: 30 mL, stir well to dissolve, then add dopamine hydrochloride, hydrogen peroxide, and ammonium persulfate, and stir the reaction for 24 h. After dialysis purification and freeze-drying, obtain a polymer modifier, where the molar ratio of quaternized alkali lignin to dopamine hydrochloride is 4:1, and the volume ratio of hydrogen peroxide to the Tris buffer solution is 1:140, and the mass ratio of ammonium persulfate to quaternized alkali lignin is 1:100; S2.3: Add silane coupling agent KH550 to a 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 1 g: 30 mL, ultrasonically disperse for 20 min, and heat and react at 60 °C for 3 h, then filter to obtain amino-functionalized black phosphorus nanosheets; S2.4: Dissolve the above polymer modifier in a Tris buffer solution at a solid-liquid ratio of 1 g: 70 mL, then add the above amino-functionalized black phosphorus nanosheets at a solid-liquid ratio of 1 g: 200 mL. After ultrasonically dispersing for 40 min, add 0.1 mol / L sodium hydroxide solution to adjust the pH to 8, and under nitrogen protection, heat and stir the reaction at 60 °C for 12 h. After centrifugal separation, washing, and vacuum drying, obtain coated and modified black phosphorus nanosheets; S3: Prepare modified hollow glass microspheres S3.1: Add hollow glass microspheres with a particle size of 10 μm to a 0.3 mol / L sodium hydroxide solution at a solid-liquid ratio of 1 g: 40 mL, heat and stir at 85 °C for 2 h. After suction filtration and washing until neutral, obtain pretreated microspheres; S3.2: ultrasonically mixing the pretreated microbeads with deionized water and anhydrous ethanol in a mass ratio of 1:3:10, adding silane coupling agent KH550, and stirring at 80°C for 3h, filtering, washing and vacuum drying to obtain aminated microbeads, wherein the mass ratio of silane coupling agent KH550 to hollow glass microbeads is 1:100; S3.3: adding the above-mentioned amino microbeads to a mixed solvent at a solid-liquid ratio of 1g:40mL, and dispersing by ultrasonication to obtain a microbead dispersion, and dissolving hexamethylene diisocyanate trimer in the mixed solvent at a solid-liquid ratio of 1g:20mL to obtain a hexamethylene diisocyanate trimer solution, wherein the mixed solvent is prepared by mixing ethyl acetate, xylene and butyl acetate at a mass ratio of 2:1:1.3; S3.4: adding the microbead dispersion to the hexamethylene diisocyanate trimer solution at a volume ratio of 1:5, stirring and reacting for 4 hours to obtain an isocyanate-modified microbead dispersion; S3.5: Dissolve JF-2X FEVE fluorine-containing resin in a mixed solvent at a solid-liquid ratio of 1g:30mL, add an equal volume of the above-mentioned isocyanate-modified microsphere dispersion, stir and react for 10 hours, filter, wash and dry to obtain modified hollow glass microspheres; S4: Preparation of epoxy resin coating 100 parts by mass of bisphenol A epoxy resin is added to 100 parts by mass of acetone, and the mixture is thoroughly stirred and dissolved. Then, 36 parts by mass of the flame retardant additive, 12 parts by mass of coated modified black phosphorus nanosheets and 30 parts by mass of modified hollow glass microspheres are added, and the mixture is thoroughly stirred and mixed. Then, 30 parts by mass of fatty amine modified curing agent, 2 parts by mass of silicone defoaming agent, 2 parts by mass of silicone leveling agent and 5 parts by mass of stearic acid are added, and the mixture is thoroughly mixed to obtain an epoxy resin coating.

[0026] Comparative Example 1 The difference between this comparative example 1 and example 1 is that step S1 is removed, and the flame retardant additive in step S4 is removed.

[0027] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the flame retardant additive in step S4 is replaced by an equal amount of triphenyl phosphate.

[0028] Comparative Example 3 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 by an equal amount of black phosphorus nanosheets.

[0029] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that steps S2.1 - 2.2 and S2.4 are removed, and the coated and modified black phosphorus nanosheets in step S4 are replaced with an equal amount of amino-functionalized black phosphorus nanosheets prepared in step S2.3.

[0030] Comparative Example 5 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.

[0031] Comparative Example 6 The difference between Comparative Example 6 and Example 1 is that the coated and modified black phosphorus nanosheets in step S4 are replaced with an equal amount of modified hollow glass microspheres.

[0032] Comparative Example 7 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 and modified black phosphorus nanosheets.

[0033] Test Example Test 1: The epoxy resin coatings prepared in Examples 1 - 3 and Comparative Examples 1 - 2 were evenly coated on steel plates. After curing, the surfaces of each coating were observed for white spots or powdery substances, and the limiting oxygen index was measured using an oxygen index meter. The results are shown in Table 1.

[0034] Table 1: Test Results of the Limiting Oxygen Index and Combustion Grade of the Coatings

[0035] As shown in Table 1, after no flame retardant additive was added in Comparative Example 1, the limiting oxygen index of the coating was significantly lower than that of Example 1, indicating that the addition of the flame retardant additive can effectively improve the flame retardant performance of the epoxy resin coating. In addition, after the flame retardant additive was replaced with an additive-type organophosphorus flame retardant in Comparative Example 2, white powder precipitated on the coating surface, indicating poor compatibility with the epoxy resin matrix. However, no precipitation occurred on the surfaces of the coatings in Examples 1 - 3, indicating good compatibility between the flame retardant additive of the present invention and the epoxy resin matrix.

[0036] Test 2: The epoxy resin coatings prepared in Examples 1 - 3 and Comparative Example 1 were poured into molds for curing to form cured products, and then the tensile properties were tested according to the method of GB / T 1040.1 - 2006. The results are shown in Table 2.

[0037] Table 2: Test Results of Tensile Properties

[0038] As shown in Table 2, after no flame retardant additive was added in Comparative Example 1, the tensile strength of the cured product of the epoxy resin coating prepared was significantly lower than that of Example 1. Thus, it can be seen that the flame retardant additive helps to improve the mechanical properties of the epoxy resin coating.

[0039] Test 3: The epoxy resin coatings prepared in Examples 1-3 and Comparative Examples 3-4 were poured into a mold for curing, irradiated with a 300 W ultraviolet lamp for 360 h, and then the color difference value was measured using a CM-2300D color difference meter. The results are shown in Table 3.

[0040] Table 3: Test results of color difference value

[0041] As shown in Table 3, after the black phosphorus nanosheets were not modified in Comparative Example 3, the ultraviolet irradiation color difference value of the epoxy resin coating prepared was much lower than that of Example 1. And in Comparative Example 4, after the polymer modifier-modified black phosphorus nanosheets were replaced with silane coupling agent-modified nanosheets, the ultraviolet aging color difference value of the epoxy resin coating prepared was also lower than that of Example 1. Thus, it can be seen that after the surface of black phosphorus nanosheets was coated and modified with a polymer modifier, the anti-ultraviolet aging performance of the coating can be improved.

[0042] In addition, after the hollow glass microspheres were not surface-modified in Comparative Example 5, the ultraviolet irradiation color difference value of the epoxy resin coating prepared was also much lower than that of Example 1. It can be seen that after the hollow glass microspheres were modified with a fluoropolymer, the anti-ultraviolet aging performance of the epoxy resin coating can be effectively improved.

[0043] Test 4: The epoxy resin coatings prepared in Examples 1-3 and Comparative Examples 6-7 were respectively coated on galvanized sheets. After curing at room temperature for 2 days, they were thermally aged in a thermal aging test chamber at 100 °C for 30 days, and the situation of the coatings was observed. The results are shown in Table 4.

[0044] Table 4: Test results of thermal-oxidative aging

[0045] As shown in Table 4, when only modified hollow glass microspheres or coated and modified black phosphorus nanosheets were added in Comparative Example 6 and Comparative Example 7, the coatings formed by the epoxy resin coatings prepared showed yellowing after 30 days of thermal-oxidative aging. Thus, it can be seen that the combination of coated and modified black phosphorus nanosheets and modified hollow glass microspheres can synergistically slow down the thermal-oxidative aging rate and improve the anti-thermal-oxidative aging performance of the epoxy resin coating.

[0046] The above embodiments are only illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A preparation process of an aging-resistant flame-retardant epoxy resin coating, characterized in that: The steps include: S1: Preparation of flame retardant additives The flame retardant additive is prepared using 3,4-dihydroxybenzaldehyde, 2-amino-4-methylphenol and hexachlorocyclotriphosphazene as raw materials; S2: Preparation of coated modified black phosphorus nanosheets The alkali lignin is quaternized and reacted with dopamine hydrochloride to prepare a polymer modifier, and then the aminated black phosphorus nanosheets are modified to obtain coated modified black phosphorus nanosheets; S3: Preparation of modified hollow glass microspheres The hollow glass microspheres after alkalization pretreatment are amino-treated, and then reacted with hexamethylene diisocyanate trimer, and finally a fluorine-containing polymer is added to react to obtain modified hollow glass microspheres; S4: Preparation of epoxy resin coating 90-100 parts by mass of bisphenol A epoxy resin are added to 95-100 parts by mass of an organic solvent, and the mixture is fully stirred and dissolved. Then, 32-36 parts by mass of the flame retardant additive, 10-12 parts by mass of coated modified black phosphorus nanosheets and 20-30 parts by mass of modified hollow glass microspheres are added, and the mixture is fully stirred and mixed. Then, 20-30 parts by mass of a curing agent, 1-2 parts by mass of a defoaming agent, 1-2 parts by mass of a leveling agent and 3-5 parts by mass of a plasticizer are added, and the mixture is fully mixed to obtain an epoxy resin coating.

2. The preparation process of an aging-resistant flame-retardant epoxy resin coating according to claim 1, characterized in that: S1 specifically includes the following steps: 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, add glacial acetic acid to adjust the pH to 4-5, and heat under reflux at 70-80 ° C for 8-12 h. After post-treatment, an intermediate is obtained; S1.2: Add the above intermediate into anhydrous tetrahydrofuran at a solid-liquid ratio of 1 g: (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. Place the mixed solution in a 3-5℃ ice water bath, add the hexachlorocyclotriphosphazene solution dropwise while stirring, and then heat and stir at 40-50℃ to react for 12-16h. Then, remove the tetrahydrofuran by distillation under reduced pressure, and then wash and recrystallize to obtain a flame retardant additive.

3. The preparation process of an aging-resistant flame-retardant epoxy resin coating according to claim 2, characterized in that: S2 specifically includes the following steps: S2.1: Add alkali lignin to a 20% sodium hydroxide solution at a solid-liquid ratio of 1 g: (3-5) mL, stir thoroughly to dissolve, then add 3-chloro-2-hydroxypropyltrimethylammonium chloride, heat and stir at 80-90°C for 3-4 hours, dialyze and freeze-dry to obtain quaternized alkali lignin; S2.2: dissolve the quaternized alkali lignin in a Tris buffer solution with a pH of 8-9 at a solid-liquid ratio of 1 g: (20-30) mL, add dopamine hydrochloride, hydrogen peroxide and ammonium persulfate, and stir to react for 20-24 hours, dialyze and freeze-dry to obtain a polymer modifier; S2.3: Add silane coupling agent KH550 to 60% ethanol solution at a volume ratio of 1: (98-100), and add acetic acid to adjust the pH to 4-5, then add ultrasonically cleaned and dried black phosphorus nanosheets at a solid-liquid ratio of 1g: (20-30)mL, ultrasonically disperse for 10-20min, and heat at 50-60℃ for reaction for 2-3h, filter, and obtain amino black phosphorus nanosheets; S2.4: The above polymer modifier is dissolved in Tris buffer at a solid-liquid ratio of 1g: (60-70)mL, and then the above amino-modified black phosphorus nanosheets are added at a solid-liquid ratio of 1g: (180-200)mL. After ultrasonic dispersion for 30-40min, 0.1mol / L sodium hydroxide solution is added to adjust the pH to 7-8, and the reaction is heated and stirred at 50-60°C for 10-12h under nitrogen protection. After post-treatment, the coated modified black phosphorus nanosheets are obtained.

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

5. The preparation process of an aging-resistant flame-retardant epoxy resin coating according to claim 2, 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).

6. The preparation process of an aging-resistant flame-retardant epoxy resin coating according to claim 3, 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.

7. The preparation process of an aging-resistant flame-retardant epoxy resin coating according to claim 3, 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).

8. The process for preparing an aging-resistant flame-retardant epoxy resin coating according to claim 4, 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).

9. The process for preparing an aging-resistant 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 defoaming agent is an organosilicon defoaming agent; 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.

10. An aging-resistant flame-retardant epoxy resin coating, characterized in that: The coating is prepared by the preparation process of an ageing-resistant flame-retardant epoxy resin coating as described in any one of claims 1 to 9.

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