A nano porcelain coating for galvanized guardrail steel plate coating renovation and a preparation method thereof

Abstract

The application discloses a kind of nano porcelain coating for galvanized guardrail steel plate coating renovation and a preparation method thereof, and belongs to the technical field of coating.The nano porcelain coating for galvanized guardrail steel plate coating renovation of the application comprises, by mass fraction, 20-30 mass parts of epoxy resin base material, 4-6 mass parts of epoxy diluent, 30-45 mass parts of titanium-containing filler, 0.5-1 mass part of dispersant, 0.5-1 mass part of defoaming agent, 0.5-1 mass part of accelerator, 5-10 mass parts of solvent, 8-10 mass parts of amine curing agent and 1-3 mass parts of carbon disulfide.The titanium-containing filler is obtained by in-situ hydrolysis of titanium tetrachloride on the surface of hexagonal boron nitride.The amine curing agent comprises 4,5-dimethyl-1,2-phenylenediamine, phosphoramide curing agent, modified polyamide and modified aliphatic amine.The accelerator comprises any one or several of bis(triphenylphosphine)ammonium chloride, phenol, salicylic acid and tris(dimethylaminomethyl)phenol.The solvent is any one or several of methyl ethyl ketone, dimethylbenzene, butanol, methyl isobutyl ketone and toluene.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a nano-ceramic coating for renovating galvanized guardrail steel plates and its preparation method. Background Technology

[0002] With the rapid development of my country's transportation infrastructure, higher demands are being placed on the durability and aesthetics of guardrail materials for road safety protection facilities such as highways, urban expressways, and bridges. Galvanized steel guardrail plates are widely used in various road projects due to their excellent corrosion resistance and economy. However, during long-term service, the organic coating on the galvanized layer is prone to aging phenomena such as powdering, cracking, and peeling due to multiple environmental factors, including ultraviolet radiation, acid rain erosion, salt spray corrosion, mechanical scratches, and temperature changes. This not only affects the appearance of the guardrail but also weakens its overall corrosion resistance, shortens its service life, and increases maintenance costs.

[0003] To extend the service life of guardrails and reduce total lifecycle costs, coating renovation has become an economical and efficient maintenance method. In recent years, nano-ceramic coatings, due to their high hardness, excellent weather resistance, self-cleaning properties, and good adhesion, have been increasingly applied to the protection and renovation of metal substrates. Among them, nano-ceramic coatings, based on resin and supplemented with functional fillers such as nano-titanium dioxide, can not only form a dense physical barrier, effectively blocking the penetration of water vapor, oxygen, and corrosive ions, but also, nano-titanium dioxide itself has photocatalytic activity and self-cleaning ability, which can improve the coating's stain resistance and environmental adaptability to a certain extent. However, there are still obvious shortcomings in the actual application of galvanized guardrail steel plate renovation: on the one hand, the wear resistance of the coating is limited, and it is prone to scratches or even local damage during frequent wind and sand erosion, vehicle scratches, or cleaning operations, leading to protection failure; on the other hand, although it has a certain degree of corrosion resistance, in harsh environments such as high humidity, high salt, or industrial pollution, the coating's density is insufficient or the interfacial bonding is weak, which can easily cause local corrosion and spread along the coating / substrate interface, making it difficult to meet the requirements of long-term outdoor service of guardrails.

[0004] Therefore, there is an urgent need to develop a nano-ceramic coating that combines excellent wear resistance and corrosion resistance. Summary of the Invention

[0005] The purpose of this invention is to provide a nano-ceramic coating for the renovation of galvanized guardrail steel plates and its preparation method, so as to solve the technical problems mentioned in the background art.

[0006] The technical solution to achieve the objective of this invention is:

[0007] In a first aspect, the present invention provides a nano-ceramic coating for the renovation of galvanized guardrail steel plates. By mass, the raw material components include 20-30 parts by mass of epoxy resin base, 4-6 parts by mass of epoxy diluent, 30-45 parts by mass of titanium-containing filler, 0.5-1 parts by mass of dispersant, 0.5-1 parts by mass of defoamer, 0.5-1 parts by mass of accelerator, 5-10 parts by mass of solvent, 8-10 parts by mass of amine curing agent, 1-3 parts by mass of carbon disulfide, and 0.5-1 parts by mass of silane coupling agent.

[0008] Furthermore, the epoxy resin base material includes any one or at least a combination of two of bisphenol A type epoxy resin, bisphenol F type epoxy resin, and diglycidyl 4,5-epoxyhexane-1,2-dicarboxylic acid.

[0009] Furthermore, the defoamer is any one or more of BYK-066, EFKA-2722, Deqian 6800, and BYK-A530.

[0010] Furthermore, the dispersant is any one or more of BYK-110, BYK-ATU, BYK-2009, and BYK-2155.

[0011] Furthermore, the epoxy diluent includes propylene oxide butyl ether, cyclohexane oxide, and terminal epoxy polyether silicone oil.

[0012] Furthermore, the silane coupling agent used is KH-560.

[0013] Furthermore, the titanium-containing filler is obtained by in-situ hydrolysis of titanium tetrachloride on the surface of hexagonal boron nitride.

[0014] Further, the amine curing agent includes any one or a combination of several of 4,5-dimethyl-1,2-phenylenediamine, phosphoramide curing agents, modified polyamides, and modified aliphatic amines; the phosphoramide curing agent is obtained by reacting spirocyclic pentaerythritol diphosphate diphosphoryl chloride with 4-amino-2-hydroxybenzaldehyde.

[0015] Furthermore, the accelerator includes any one or more of bis(triphenylphosphine)ammonium chloride, phenol, salicylic acid, and tri-(dimethylaminomethyl)phenol.

[0016] Further, the solvent is any one or more of methyl ethyl ketone, xylene, butanol, methyl isobutyl ketone, and toluene; preferably, the solvent is obtained by mixing xylene, butanol, toluene, and methyl isobutyl ketone in a mass ratio of 2:1:2:4.

[0017] Secondly, a method for preparing a nano-ceramic coating for renovating galvanized guardrail steel plates as described in the first aspect includes the following preparation steps:

[0018] (1) Mix the phosphoramide curing agent with 8 to 10 times its mass of anhydrous ethanol, and then add dropwise an anhydrous ethanol solution containing 4,5-dimethyl-1,2-phenylenediamine, wherein the mass ratio of 4,5-dimethyl-1,2-phenylenediamine to anhydrous ethanol is 1:(10 to 20). Stir and reflux for 3.5 to 4.5 hours, then cool to room temperature. After removing the solvent by filtration, recrystallize with anhydrous ethanol, dry under reduced pressure, and then mix with modified polyamide and modified aliphatic amine to obtain a premixed curing agent.

[0019] (2) Mix epoxy resin base material, epoxy diluent, titanium-containing filler, dispersant, defoamer, silane coupling agent and solvent evenly, and ultrasonically disperse for 25-35 minutes. Then add accelerator, premixed curing agent and carbon disulfide and continue mixing and stirring for 10-20 minutes to obtain nano-ceramic coating for galvanized guardrail steel plate coating renovation.

[0020] Further, the preparation method of the phosphoramide curing agent is as follows: 55-59 parts by weight of 4-amino-2-hydroxybenzaldehyde and 160-240 parts by weight of acetonitrile are mixed, heated to 55-65°C under nitrogen protection, and stirred for 1-2 hours. Then, 58-60 parts by weight of spirocyclic pentaerythritol diphosphate diphosphoryl chloride are added, and the mixture is kept warm and stirred for 1.5-2.5 hours. Then, the temperature is raised to 70-80°C and stirred for 5-7 hours. The mixture is filtered, washed 2-4 times with acetonitrile, and vacuum dried at 65-75°C for 11-13 hours to obtain the phosphoramide curing agent.

[0021] Further, the preparation method of the titanium-containing filler is as follows: 1 part by mass of hexagonal boron nitride is added to 20 parts by mass of deionized water and ultrasonically dispersed for 25-35 min to obtain a hexagonal boron nitride dispersion; 1.5-2 parts by mass of titanium tetrachloride and deionized water are mixed at a volume ratio of 1:(25-35), stirred for 25-35 min, and then added to the hexagonal boron nitride dispersion. The pH is then adjusted to 5.5-6 with 5 mol / L sodium hydroxide solution, and stirring is continued for 25-35 min. The mixture is then heated to 175-185℃ for hydrothermal reaction for 9-11 h. After cooling to room temperature, the mixture is centrifuged, washed, dried, ground, and passed through a 200-mesh sieve to obtain the titanium-containing filler.

[0022] Further, the mass ratio of the phosphoramide curing agent, 4,5-dimethyl-1,2-phenylenediamine, modified polyamide, and modified aliphatic amine is (2.4-2.5):(0.5-0.6):(0-5):(0-5).

[0023] Furthermore, the nano-ceramic coating for refurbishing the galvanized guardrail steel plate coating is first cured at 55-65℃ for 5-6 hours, and then heated to 75-80℃ for 8-12 hours.

[0024] Furthermore, the accelerator comprises at least 0.1 to 0.3 parts by weight of bis(triphenylphosphine)ammonium chloride.

[0025] By adopting the above technical solution, the present invention has the following beneficial effects:

[0026] (1) The raw material components of the nano-ceramic coating for refurbishing galvanized guardrail steel plate coating of the present invention include epoxy resin base, epoxy diluent, titanium-containing filler, dispersant, defoamer, accelerator, solvent, amine curing agent, carbon disulfide and silane coupling agent; wherein, by introducing titanium-containing filler, the corrosion resistance and wear resistance of the nano-ceramic coating in the application of galvanized guardrail steel plate coating refurbishment are effectively improved.

[0027] (2) The epoxy diluent of the present invention includes propylene oxide butyl ether, cyclohexane oxide, and terminal epoxy polyether silicone oil. The molecular structure of the epoxy diluent contains epoxy groups that can participate in the epoxy curing reaction. While reducing the viscosity of the resin base system, it can participate in the construction of the cross-linking network together with epoxy resin and amine curing agent. On the one hand, the reduction in viscosity is beneficial to increasing the solid content of the coating, reducing the amount of solvent without sacrificing the construction performance, thereby forming a denser and thicker coating structure. On the other hand, epoxy diluents with different structures have a regulatory effect on the topology of the cross-linking network. Propylene oxide butyl ether and cyclohexane oxide can moderately reduce the cross-linking density, introduce flexible segments, and improve the flexibility and impact resistance of the coating. Terminal epoxy polyether silicone oil, due to the flexibility of the silicon-oxygen backbone and the tendency of surface enrichment, further optimizes the internal stress distribution of the coating and enhances the surface density, making the coating structure more uniform and less defective during the curing process, thereby significantly improving the wear resistance of the coating and providing a guarantee for the long-term protection of galvanized guardrail steel plates in complex service environments.

[0028] (3) The titanium-containing filler used in this invention is obtained by in-situ hydrolysis of titanium tetrachloride on the surface of hexagonal boron nitride. Hexagonal boron nitride, also known as "white graphene", has high impermeability, high hardness, excellent electrical insulation, chemical inertness and excellent thermal stability. When introduced into the epoxy resin system, it can not only effectively fill the micropores generated during the resin curing process, but its unique two-dimensional sheet structure can also build a "maze effect" inside the coating, significantly extending the penetration path of corrosive media (such as water vapor, chloride ions, etc.), thereby improving the wear resistance and corrosion resistance of the nano-titanium ceramic coating. However, hexagonal boron nitride is prone to agglomeration in epoxy resin matrices, exhibiting poor dispersibility and limiting its full performance. This invention addresses this by in-situ loading titanium dioxide onto the surface of hexagonal boron nitride nanosheets. This increases the spacing between the hexagonal boron nitride layers, effectively weakening the van der Waals forces between the layers, suppressing agglomeration, and improving dispersion stability in the resin. Furthermore, the introduction of titanium dioxide further hinders the diffusion rate of corrosive media between the hexagonal boron nitride layers, strengthening the "maze barrier" effect, thereby significantly improving the overall corrosion resistance of the coating.

[0029] (4) In the preparation process of the nano-ceramic coating of the present invention, a phosphoramide curing agent is first premixed with 4,5-dimethyl-1,2-phenylenediamine, and then added to the system together with the remaining amine curing agent; wherein, the phosphoramide curing agent is prepared by reacting spirocyclic pentaerythritol diphosphate diphosphoryl chloride with 4-amino-2-hydroxybenzaldehyde; the benzaldehyde group in the phosphoramide curing agent can undergo a condensation reaction with the amino group in the 4,5-dimethyl-1,2-phenylenediamine molecule to generate in situ a Schiff base structure compound with tetradentate coordination ability; during coating application, this tetradentate Schiff base structure can react with the galvanized guardrail steel plate after grinding, degreasing and pickling activation treatment. Exposed zinc ions undergo coordination to form stable zinc-Schiff base complexes, thereby constructing chemical anchoring points at the coating-substrate interface and significantly improving the coating's adhesion and corrosion resistance to galvanized steel sheets. Simultaneously, during the curing process, unreacted epoxy resin base containing cyclohexane and epoxy diluent undergo copolymerization with carbon disulfide under the synergistic catalytic action of the zinc-Schiff base complex and the accelerator bis(triphenylphosphine)ammonium chloride, generating sulfur-containing heterocyclic or thioether cross-linked structures. This further densifies the coating network, enhancing its resistance to wear and corrosion penetration, thus synergistically improving the wear resistance and corrosion resistance of the nano-ceramic coating. Detailed Implementation

[0030] To better understand the above technical solution, the following will provide a detailed explanation of the technical solution in conjunction with specific implementation methods.

[0031] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.

[0032] The following embodiments are only used to illustrate the technical solutions of the present invention more clearly, and should not be used to limit the scope of protection of the present invention.

[0033] The epoxy resin used is epoxy resin TDE-85.

[0034] The epoxy diluent is obtained by mixing propylene oxide butyl ether, cyclohexane oxide, and terminal epoxy polyether silicone oil IOTA-EO9000 in a mass ratio of 1:2:2.

[0035] KH-560 was used as the silane coupling agent.

[0036] The accelerator consists of 0.2 parts by weight of bis(triphenylphosphine)ammonium chloride, 0.1 parts by weight of phenol, 0.1 parts by weight of salicylic acid, and 0.6 parts by weight of tri-(dimethylaminomethyl)phenol.

[0037] The dispersant used is BYK-110.

[0038] The defoamer is BYK-066.

[0039] The solvent is obtained by mixing xylene, butanol, toluene, and methyl isobutyl ketone in a mass ratio of 2:1:2:4.

[0040] The modified polyamide is Huntsman Aradur 450BD.

[0041] The modified fatty amine is Evonik Chemical's Ancamine 2089M.

[0042] Example 1

[0043] A method for preparing a nano-ceramic coating for renovating galvanized steel guardrails includes the following preparation steps:

[0044] (1) A phosphoramide curing agent was mixed with 8 times its mass of anhydrous ethanol, and then an anhydrous ethanol solution containing 4,5-dimethyl-1,2-phenylenediamine was added dropwise. The mass ratio of 4,5-dimethyl-1,2-phenylenediamine to anhydrous ethanol was 1:10. After stirring and refluxing for 3.5 h, the mixture was cooled to room temperature. The solvent was removed by filtration, and the mixture was recrystallized with anhydrous ethanol and dried under reduced pressure. Then it was mixed with modified polyamide and modified aliphatic amine to obtain a premixed curing agent. The mass ratio of phosphoramide curing agent, 4,5-dimethyl-1,2-phenylenediamine, modified polyamide, and modified aliphatic amine was 2.4:0.6:1.5:1.5.

[0045] (2) Mix 20 parts by weight of epoxy resin base material, 4 parts by weight of epoxy diluent, 30 parts by weight of titanium-containing filler, 0.5 parts by weight of dispersant, 0.5 parts by weight of defoamer, 5 parts by weight of solvent, and 0.5 parts by weight of silane coupling agent evenly, and ultrasonically disperse for 25 min. Then add 1 part by weight of accelerator, 6 parts by weight of premixed curing agent, and 1 part by weight of carbon disulfide, and continue mixing and stirring for 10 min to obtain nano-ceramic coating for galvanized guardrail steel plate coating renovation.

[0046] The preparation method of the phosphoramide curing agent is as follows: 55 parts by weight of 4-amino-2-hydroxybenzaldehyde and 160 parts by weight of acetonitrile are mixed, heated to 55°C under nitrogen protection, and stirred for 1 hour. Then, 58 parts by weight of spirocyclic pentaerythritol diphosphate diphosphoryl chloride are added, and the mixture is kept warm and stirred for 1.5 hours. Then, the temperature is raised to 70°C and stirred for 5 hours. The mixture is filtered, washed twice with acetonitrile, and dried under vacuum at 65°C for 11 hours to obtain the phosphoramide curing agent.

[0047] The preparation method of the titanium-containing filler is as follows: 1 part by mass of hexagonal boron nitride is added to 20 parts by mass of deionized water and ultrasonically dispersed for 25 min to obtain a hexagonal boron nitride dispersion; 1.5 parts by mass of titanium tetrachloride and deionized water are mixed at a volume ratio of 1:25, stirred for 25 min, and then added to the hexagonal boron nitride dispersion. The pH is then adjusted to 5.5 with 5 mol / L sodium hydroxide solution, and stirring is continued for 25 min. The mixture is then heated to 175℃ for hydrothermal reaction for 9 h. After cooling to room temperature, the mixture is centrifuged, washed, dried, ground, and passed through a 200-mesh sieve to obtain the titanium-containing filler.

[0048] Example 2

[0049] A method for preparing a nano-ceramic coating for renovating galvanized steel guardrails includes the following preparation steps:

[0050] (1) A phosphoramide curing agent was mixed with 9 times its mass of anhydrous ethanol, and then an anhydrous ethanol solution containing 4,5-dimethyl-1,2-phenylenediamine was added dropwise. The mass ratio of 4,5-dimethyl-1,2-phenylenediamine to anhydrous ethanol was 1:15. After stirring and refluxing for 4 hours, the mixture was cooled to room temperature. The solvent was removed by filtration, and the mixture was recrystallized with anhydrous ethanol and dried under reduced pressure. Then it was mixed with modified polyamide and modified aliphatic amine to obtain a premixed curing agent. The mass ratio of phosphoramide curing agent, 4,5-dimethyl-1,2-phenylenediamine, modified polyamide, and modified aliphatic amine was 2.5:0.5:2:2.

[0051] (2) Mix 25 parts by weight of epoxy resin base material, 5 parts by weight of epoxy diluent, 38 parts by weight of titanium-containing filler, 0.8 parts by weight of dispersant, 0.8 parts by weight of defoamer, 8 parts by weight of solvent, and 0.8 parts by weight of silane coupling agent evenly, and ultrasonically disperse for 30 min. Then add 1 part by weight of accelerator, 7 parts by weight of premixed curing agent, and 2 parts by weight of carbon disulfide, and continue mixing and stirring for 15 min to obtain nano-ceramic coating for galvanized guardrail steel plate coating renovation.

[0052] The preparation method of the phosphoramide curing agent is as follows: 57 parts by weight of 4-amino-2-hydroxybenzaldehyde and 200 parts by weight of acetonitrile are mixed, heated to 60°C under nitrogen protection, and stirred for 1.5 h. Then, 59 parts by weight of spirocyclic pentaerythritol diphosphate diphosphoryl chloride are added, and the mixture is kept warm and stirred for 2 h. Then, the temperature is raised to 75°C and stirred for 6 h. The mixture is filtered, washed three times with acetonitrile, and dried under vacuum at 70°C for 12 h to obtain the phosphoramide curing agent.

[0053] The preparation method of the titanium-containing filler is as follows: 1 part by mass of hexagonal boron nitride is added to 20 parts by mass of deionized water and ultrasonically dispersed for 30 min to obtain a hexagonal boron nitride dispersion; 1.8 parts by mass of titanium tetrachloride and deionized water are mixed at a volume ratio of 1:30, stirred for 30 min, and then added to the hexagonal boron nitride dispersion. The pH is then adjusted to 6 with 5 mol / L sodium hydroxide solution, and stirring is continued for 30 min. The mixture is then heated to 180℃ for hydrothermal reaction for 10 h. After cooling to room temperature, the mixture is centrifuged, washed, dried, ground, and passed through a 200-mesh sieve to obtain the titanium-containing filler.

[0054] Example 3

[0055] A method for preparing a nano-ceramic coating for renovating galvanized steel guardrails includes the following preparation steps:

[0056] (1) Mix the phosphoramide curing agent with 10 times its mass of anhydrous ethanol, and then add dropwise an anhydrous ethanol solution containing 4,5-dimethyl-1,2-phenylenediamine, wherein the mass ratio of 4,5-dimethyl-1,2-phenylenediamine to anhydrous ethanol is 1:20. After stirring and refluxing for 4.5 h, cool to room temperature, filter to remove the solvent, recrystallize with anhydrous ethanol, dry under reduced pressure, and then mix with modified polyamide and modified aliphatic amine to obtain a premixed curing agent; the mass ratio of phosphoramide curing agent, 4,5-dimethyl-1,2-phenylenediamine, modified polyamide, and modified aliphatic amine is 2.5:0.5:2.5:2.5;

[0057] (2) Mix 30 parts by weight of epoxy resin base material, 6 parts by weight of epoxy diluent, 45 parts by weight of titanium-containing filler, 1 part by weight of dispersant, 1 part by weight of defoamer, 10 parts by weight of solvent, and 1 part by weight of silane coupling agent evenly, and ultrasonically disperse for 35 min. Then add 1 part by weight of accelerator, 8 parts by weight of premixed curing agent, and 3 parts by weight of carbon disulfide, and continue mixing and stirring for 20 min to obtain nano-ceramic coating for galvanized guardrail steel plate coating renovation.

[0058] The preparation method of the phosphoramide curing agent is as follows: 59 parts by weight of 4-amino-2-hydroxybenzaldehyde and 240 parts by weight of acetonitrile are mixed, heated to 65°C under nitrogen protection, and stirred for 2 hours. Then, 60 parts by weight of spirocyclic pentaerythritol diphosphate diphosphoryl chloride are added, and the mixture is kept warm and stirred for 2.5 hours. Then, the temperature is raised to 80°C and stirred for 7 hours. The mixture is filtered, washed 4 times with acetonitrile, and dried under vacuum at 75°C for 13 hours to obtain the phosphoramide curing agent.

[0059] The preparation method of the titanium-containing filler is as follows: 1 part by mass of hexagonal boron nitride is added to 20 parts by mass of deionized water and ultrasonically dispersed for 35 min to obtain a hexagonal boron nitride dispersion; 2 parts by mass of titanium tetrachloride and deionized water are mixed at a volume ratio of 1:35, stirred for 35 min, and then added to the hexagonal boron nitride dispersion. The pH is then adjusted to 6 with 5 mol / L sodium hydroxide solution, and stirring is continued for 35 min. The mixture is then heated to 185℃ for hydrothermal reaction for 11 h. After cooling to room temperature, the mixture is centrifuged, washed, dried, ground, and passed through a 200-mesh sieve to obtain the titanium-containing filler.

[0060] Comparative Example 1

[0061] The difference between Comparative Example 1 and Example 2 is that the raw material components of the nano-ceramic coating for galvanized guardrail steel plate coating renovation include: 25 parts by weight of epoxy resin base, 5 parts by weight of epoxy diluent, 13 parts by weight of hexagonal boron nitride, 25 parts by weight of nano titanium dioxide, 0.8 parts by weight of dispersant, 0.8 parts by weight of defoamer, 8 parts by weight of solvent, 0.8 parts by weight of silane coupling agent, 1 part by weight of accelerator, 7 parts by weight of premixed curing agent, and 2 parts by weight of carbon disulfide. The remaining components and steps are the same as in Example 2.

[0062] Comparative Example 2

[0063] The difference between Comparative Example 2 and Example 2 is that 25 parts by weight of epoxy resin base material, 5 parts by weight of epoxy diluent, 38 parts by weight of nano titanium dioxide, 0.8 parts by weight of dispersant, 0.8 parts by weight of defoamer, 8 parts by weight of solvent, 0.8 parts by weight of silane coupling agent, 1 part by weight of accelerator, 7 parts by weight of premixed curing agent, and 2 parts by weight of carbon disulfide are used. The remaining components and steps are the same as in Example 2.

[0064] Comparative Example 3

[0065] The difference between Comparative Example 3 and Example 2 lies in step (1), which is: mixing phosphoramide curing agent, 4,5-dimethyl-1,2-phenylenediamine, modified polyamide and modified fatty amine in a mass ratio of 2.5:0.5:2:2, and the remaining components and steps are the same as in Example 2.

[0066] Comparative Example 4

[0067] The difference between Comparative Example 4 and Example 2 is that the accelerator is 0.2 parts by mass of phenol, 0.2 parts by mass of salicylic acid, and 0.6 parts by mass of tris-(dimethylaminomethyl)phenol, while the other components and steps are the same as in Example 2.

[0068] Comparative Example 5

[0069] The difference between Comparative Example 5 and Example 2 is that 25 parts by weight of epoxy resin base material, 5 parts by weight of epoxy diluent, 38 parts by weight of nano titanium dioxide, 0.8 parts by weight of dispersant, 0.8 parts by weight of defoamer, 8 parts by weight of solvent, 0.8 parts by weight of silane coupling agent, 1 part by weight of accelerator, and 7 parts by weight of premixed curing agent are used. The remaining components and steps are the same as in Example 2.

[0070] Example of effect

[0071] Clean and dry the galvanized guardrail steel plate to ensure the surface is dry, free of oil and water. Then, sand the rusted areas with sandpaper or wire. For severely rusted areas, use a rust remover. Rinse with water, then grind the surface smooth. Pickle with a mixture of 20 mL / L sulfuric acid, 40 mL / L nitric acid, and 40 mL / L hydrochloric acid for 5 minutes. Then, evenly coat the surface with the nano-ceramic coatings for galvanized guardrail steel plate renovation of Examples 1-3 and Comparative Examples 1-5. After curing at 60°C for 5 hours, raise the temperature to 75-80°C and cure for 12 hours to obtain the nano-titanium ceramic coating for galvanized guardrail steel plate renovation.

[0072] Wear resistance: Using an HT-1000 friction and wear testing machine, the normal load was 20N, the friction time was 120min, the rotation speed was 400r / min, the friction radius was 4mm, and the grinding ball was a silicon nitride ceramic ball with a diameter of 5mm. The samples were ultrasonically cleaned with alcohol before and after wear, and then dried. They were weighed 3 times, and the average value was used to calculate the wear amount.

[0073] Adhesion test: Adhesion is tested according to ASTM D4541.

[0074] Corrosion resistance test: The corrosion resistance of the samples is tested using a salt spray test chamber. A coating sample with a thickness of (100±5) μm is sealed at the edges and placed in the salt spray chamber. The salt spray pressure is adjusted to 0.05–0.17 MPa, and a 5.0% (w / w) NaCl solution is sprayed continuously for 720 hours. The surface changes of the coating are observed, and discoloration and loss of gloss are allowed in the final evaluation. After 720 hours, if the coating shows no signs of blistering, cracking, or peeling, it is rated as "compliant".

[0075] Table 1 below shows the performance test results of the nano-ceramic coatings used for renovating galvanized guardrail steel plates in Examples 1-3 and Comparative Examples 1-5:

[0076] Table 1

[0077]

[0078]

[0079] As shown in Table 1, the coatings prepared by the nano-ceramic coatings for galvanized guardrail steel plate coating renovation in Examples 1-3 have good wear resistance, corrosion resistance, and high adhesion.

[0080] The difference between Comparative Example 1 and Example 2 is that the nano-ceramic coating used for refurbishing the coating of galvanized guardrail steel plates directly adds 13 parts by weight of hexagonal boron nitride and 25 parts by weight of nano titanium dioxide, instead of titanium-containing fillers obtained by in-situ hydrolysis of titanium tetrachloride on the surface of hexagonal boron nitride. The resulting coating has weaker wear resistance, weaker corrosion resistance, and lower adhesion.

[0081] The difference between Comparative Example 2 and Example 2 is that the nano-ceramic coating used for refurbishing the galvanized guardrail steel plate coating directly adds 38 parts by weight of nano-titanium dioxide instead of titanium-containing filler obtained by in-situ hydrolysis of titanium tetrachloride on the surface of hexagonal boron nitride. The resulting coating has weaker wear resistance, weaker corrosion resistance, and lower adhesion.

[0082] The difference between Comparative Example 3 and Example 2 is that the phosphoramide curing agent, 4,5-dimethyl-1,2-phenylenediamine, modified polyamide, and modified aliphatic amine were directly mixed in a mass ratio of 2.5:0.5:2:2, instead of pre-reacting the phosphoramide curing agent and 4,5-dimethyl-1,2-phenylenediamine. The resulting coating has weaker wear resistance, weaker corrosion resistance, and lower adhesion.

[0083] The difference between Comparative Example 4 and Example 2 is that the accelerator did not contain bis(triphenylphosphine)ammonium chloride, resulting in a coating with weaker wear resistance and corrosion resistance.

[0084] The difference between Comparative Example 5 and Example 2 is that the nano-ceramic coating used for renovating the coating of galvanized guardrail steel plates did not contain carbon disulfide, resulting in a coating with weaker wear resistance and corrosion resistance.

[0085] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A nano-ceramic coating for recoating a galvanized guardrail steel sheet, characterized by, By weight, the raw material components include 20-30 parts epoxy resin base, 4-6 parts epoxy diluent, 30-45 parts titanium-containing filler, 0.5-1 parts dispersant, 0.5-1 parts defoamer, 0.5-1 parts accelerator, 5-10 parts solvent, 8-10 parts amine curing agent, 1-3 parts carbon disulfide, and 0.5-1 parts silane coupling agent; the titanium-containing filler is obtained by in-situ hydrolysis of titanium tetrachloride on the surface of hexagonal boron nitride; the amine curing agent includes... The coating comprises any one or a combination of several of the following: 4,5-dimethyl-1,2-phenylenediamine, phosphoramide curing agents, modified polyamides, and modified aliphatic amines; the phosphoramide curing agent is obtained by reacting spirocyclic pentaerythritol diphosphate diphosphoryl chloride with 4-amino-2-hydroxybenzaldehyde; the accelerator includes bis(triphenylphosphino)ammonium chloride; in the preparation process of the nano-ceramic coating, the phosphoramide curing agent is first premixed with 4,5-dimethyl-1,2-phenylenediamine, and then added to the system together with the remaining amine curing agent.

2. The nano-ceramic coating for repainting of galvanized guardrail steel sheet according to claim 1, characterized by, The accelerator also includes any one or more of phenol, salicylic acid, and tris-(dimethylaminomethyl)phenol.

3. The nano-ceramic coating for repainting of galvanized guardrail steel sheet according to claim 1, characterized by, The solvent is any one or more of methyl ethyl ketone, xylene, butanol, methyl isobutyl ketone, and toluene.

4. A method for preparing a nano-ceramic coating for recoating a galvanized guardrail steel sheet according to any one of claims 1 to 3, characterized in that, The preparation steps include the following: (1) Mix the phosphoramide curing agent with 8 to 10 times its mass of anhydrous ethanol, and then add dropwise an anhydrous ethanol solution containing 4,5-dimethyl-1,2-phenylenediamine, wherein the mass ratio of 4,5-dimethyl-1,2-phenylenediamine to anhydrous ethanol is 1:(10 to 20). Stir and reflux for 3.5 to 4.5 hours, then cool to room temperature. After removing the solvent by filtration, recrystallize with anhydrous ethanol, dry under reduced pressure, and then mix with modified polyamide and modified aliphatic amine to obtain a premixed curing agent. (2) Mix epoxy resin base material, epoxy diluent, titanium-containing filler, dispersant, defoamer, silane coupling agent and solvent evenly, and ultrasonically disperse for 25-35 minutes. Then add accelerator, premixed curing agent and carbon disulfide and continue mixing and stirring for 10-20 minutes to obtain nano-ceramic coating for galvanized guardrail steel plate coating renovation.

5. The preparation method of the nano-ceramic coating for refurbishing galvanized guardrail steel plates according to claim 4, characterized in that, The preparation method of the phosphoramide curing agent is as follows: 55-59 parts by weight of 4-amino-2-hydroxybenzaldehyde and 160-240 parts by weight of acetonitrile are mixed, heated to 55-65°C under nitrogen protection, and stirred for 1-2 hours. Then, 58-60 parts by weight of spirocyclic pentaerythritol diphosphate diphosphoryl chloride are added, and the mixture is kept at the same temperature and stirred for 1.5-2.5 hours. Then, the temperature is raised to 70-80°C and stirred for 5-7 hours. The mixture is filtered, washed 2-4 times with acetonitrile, and vacuum dried at 65-75°C for 11-13 hours to obtain the phosphoramide curing agent.

6. The method of claim 4, wherein the nano-ceramic coating for galvanized guardrail steel sheet coating renovation is prepared by mixing 0.5 to 1.5 parts by weight of the nano-ceramic coating for galvanized guardrail steel sheet coating renovation of claim 4 with 99 to 98.5 parts by weight of a solvent. The preparation method of the titanium-containing filler is as follows: 1 part by mass of hexagonal boron nitride is added to 20 parts by mass of deionized water and ultrasonically dispersed for 25-35 min to obtain a hexagonal boron nitride dispersion; 1.5-2 parts by mass of titanium tetrachloride and deionized water are mixed at a volume ratio of 1:(25-35), stirred for 25-35 min, and then added to the hexagonal boron nitride dispersion. The pH is then adjusted to 5.5-6 with 5 mol / L sodium hydroxide solution, and stirring is continued for 25-35 min. The mixture is then heated to 175-185℃ for hydrothermal reaction for 9-11 h. After cooling to room temperature, the mixture is centrifuged, washed, dried, ground, and passed through a 200-mesh sieve to obtain the titanium-containing filler.

7. The method of claim 4, wherein the nano-ceramic coating for galvanized guardrail steel sheet coating renovation is prepared by mixing 0.5 to 1.5 parts by weight of the nano-ceramic coating for galvanized guardrail steel sheet coating renovation of claim 4 with 99 to 98.5 parts by weight of a solvent. The mass ratio of the phosphoramide curing agent, 4,5-dimethyl-1,2-phenylenediamine, modified polyamide, and modified aliphatic amine is (2.4-2.5):(0.5-0.6):(0-5):(0-5).

8. The method for preparing the nano-ceramic coating for renovating galvanized guardrail steel plates according to claim 4, characterized in that, The nano-ceramic coating for refurbishing the galvanized guardrail steel plate coating is first cured at 55-65℃ for 5-6 hours, and then the temperature is raised to 75-80℃ for 8-12 hours.

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