High-weather-resistance epoxy coating and preparation method thereof

Abstract

The invention discloses a high-weather-resistance epoxy coating and a preparation method thereof, and belongs to the technical field of epoxy coatings. Comprising the following raw materials in parts by weight: 80-100 parts of bisphenol A epoxy resin, 30-38 parts of phenolic resin, 1-3 parts of a curing accelerator, 15-23 parts of pigment, 3-5 parts of an antioxidant and 4-12 parts of a weather-proof additive. Wherein the weather-resistant additive can significantly improve the heat resistance and ultraviolet resistance of the coating, and the hindered phenol antioxidant can inhibit the damage of oxidation reaction to the coating; phenolic resin and bisphenol A epoxy resin form a compact cross-linked structure under the action of a curing accelerator, the thermal stability of the coating is further improved, the prepared coating is a powder coating, pollution to the environment and harm to human health are reduced, and in conclusion, the coating has the advantages of environmental protection and environmental protection. The weather resistance of the prepared coating is improved from the aspects of oxidation resistance, heat resistance, ultraviolet resistance and the like, and the coating is environmentally friendly and has important application value in the technical field of epoxy coatings.

Description

Technical Field

[0001] The present invention belongs to the technical field of epoxy coatings, and specifically, relates to a highly weather-resistant epoxy coating and a preparation method thereof. Background Art

[0002] In the modern industrial and construction fields, coatings are widely used, and their performance directly affects the service life and appearance quality of the coated objects. Epoxy coatings occupy an important position in multiple fields such as anti-corrosion and decoration due to their excellent adhesion, hardness, chemical corrosion resistance, etc. However, with the increasing complexity of the industrial environment and the increase in the service life of outdoor facilities, higher requirements are put forward for the weather resistance of epoxy coatings. When traditional epoxy coatings are exposed to the outdoor environment for a long time, they will be eroded by various factors such as ultraviolet rays, rain, sand, and high and low temperature cycles, resulting in phenomena such as powdering, cracking, and fading of the coating, leading to a decline in its protective performance, shortening of the service life, and thus losing the protective effect on the substrate, seriously affecting the normal use and aesthetics of equipment and buildings. This problem limits the application of epoxy coatings in outdoor or harsh environments.

[0003] In addition, in high-temperature environments, ordinary epoxy coatings will soften and decompose, and the physical and mechanical properties of the coating will drop sharply, resulting in problems such as blistering and peeling, unable to effectively protect the substrate, and even potentially causing safety hazards. For example, in petroleum refining units, the surface temperature of pipelines and equipment sometimes exceeds 150°C, and ordinary epoxy coatings are difficult to play a long-term stable protective role; on facilities such as high-temperature furnaces and chimneys, ordinary epoxy coatings cannot withstand the thermal stress changes brought about by high temperatures.

[0004] At present, although there are already some technologies and products in the market aiming to improve the weather resistance and heat resistance of epoxy coatings, there are still many deficiencies. Some improvement methods enhance the weather resistance by adding ultraviolet absorbers, light stabilizers and other additives, and improve the heat resistance by adding heat-resistant fillers or additives. However, there is no synergistic effect among these additives, resulting in insufficient performance, and adding multiple additives will also affect the homogeneity of epoxy coatings.

[0005] Finally, traditional epoxy resin coatings are solvent-based, with a high VOC content and poor environmental performance. In summary, there is an urgent need to invent an environmentally friendly and highly weather-resistant epoxy coating to meet the higher requirements in the technical field of epoxy coatings. Summary of the Invention

[0006] The purpose of the present invention is to overcome the defects of the prior art and provide a highly weather-resistant epoxy coating and a preparation method thereof.

[0007] The purpose of the present invention can be achieved by the following technical solutions: A highly weather-resistant epoxy coating, comprising the following raw materials in parts by weight: 80-100 parts of bisphenol A epoxy resin, 30-38 parts of phenolic resin, 1-3 parts of curing accelerator, 15-23 parts of pigment, 3-5 parts of antioxidant, and 4-12 parts of weather resistance aid.

[0008] As a further technical solution, the curing accelerator is one of 2-methylimidazole and 2-ethyl-4-methylimidazole.

[0009] As a further technical solution, the antioxidant is a hindered phenol antioxidant.

[0010] In the present invention, the phenolic resin can form a dense cross-linked structure after curing with bisphenol A epoxy resin under the action of a curing accelerator, greatly improving the heat resistance of the coating and enhancing the weather resistance; in addition, the added hindered phenol antioxidant can capture free radicals and improve the antioxidant performance of the coating.

[0011] As a further technical solution, the weather resistance aid is prepared by the following steps: Step B1: In a three-necked flask equipped with a thermometer, a condenser and a magnetic stirrer, first add anhydrous toluene. Under a nitrogen atmosphere and an ice bath condition of 0 °C, successively add cyanuric chloride, resorcinol and aluminum trichloride, and stir magnetically for 10-15 min. Remove the ice bath, and heat the device to 78 °C (oil bath temperature control ±2 °C), and stir and react for 5 h. After the reaction is completed, extract with dichloromethane. After combining the organic phases, wash with saturated sodium bicarbonate until neutral, rotary evaporate to remove toluene, and recrystallize the residue with hot ethanol to obtain product A; As a further technical solution, the dosage ratio of anhydrous toluene, cyanuric chloride, resorcinol and aluminum trichloride in step B1 is 150 mL: 18.2 g: 36.1 g: 2.2 g.

[0012] In step B1, cyanuric chloride and resorcinol undergo an alkylation reaction under the catalysis of aluminum trichloride, and the two are combined in a molar ratio of 1:3; the reaction formula is as follows: Step B2: In a three-necked flask equipped with a thermometer, a condenser and a magnetic stirrer, add 2-aminobenzotriazole, triethylamine, anhydrous toluene and 1,3-dichloropropane. After stirring magnetically for 10-20 min, introduce nitrogen as a protective gas, heat the device, and when the temperature reaches 70 °C, stir and react at this temperature for 3 h. After the reaction is completed, rotary evaporate and purify by column chromatography to obtain product B; As a further technical solution, the dosage ratio of 2-aminobenzotriazole, triethylamine, anhydrous toluene and 1,3-dichloropropane in step B2 is 13.4 g: 10.1 g: 100 mL: 12.7 g.

[0013] In step B2, 2-aminobenzotriazole and 1,3-dichloropropane undergo a nucleophilic substitution reaction under the catalysis of triethylamine, and they are combined in a molar ratio of 1:1; and 1,3-dichloropropane is slightly in excess to reduce side reactions. The reaction formula is as follows: Step B3: In a three-necked flask equipped with a thermometer, a constant-pressure dropping funnel, a condenser, and a magnetic stirrer, first add anhydrous toluene and displace the air with nitrogen; sequentially add product A and product B into the flask, then mix sodium hydroxide and deionized water, stir until the sodium hydroxide is completely dissolved, and then use the constant-pressure dropping funnel to add it to the flask. Then heat the device. When the temperature reaches 75 °C, keep the temperature for reaction for 8 h. After the reaction is completed, filter while it is hot, perform rotary evaporation, purify by column chromatography, and dry to obtain the weather resistance aid; As a further technical solution, in step B3, the dosage ratio of anhydrous toluene, product A, product B, sodium hydroxide, and deionized water is 200 mL: 40.5 g: 62.9 g: 11.9 g: 30 mL.

[0014] In step B3, sodium hydroxide can react with the phenolic hydroxyl group at the para position in the molecule of product A to form a phenolate with stronger nucleophilicity, and then react with the chlorine atom on the molecule of product B; they are combined in a molar ratio of 1:3. The reaction formula is as follows: The weather resistance aid prepared by the present invention belongs to a triazine ultraviolet absorber, and its core structure is a s-triazine ring with three phenolic hydroxyl groups on the ring. This structure has strong ultraviolet absorption ability. When ultraviolet rays irradiate a coating containing the triazine ultraviolet absorber, the π-π conjugate system in the ultraviolet absorber molecule can absorb the energy of ultraviolet photons, causing the molecule to transition from the ground state to the excited state, and releasing the absorbed ultraviolet energy back to the environment in the form of harmless heat energy, fluorescence, or phosphorescence, greatly improving the ultraviolet resistance of the coating. In addition, the weather resistance aid molecule also contains a triazole ring group. The C-N bond and N-N bond in the triazole ring have relatively high bond energies and are not easily broken, which can greatly improve the heat resistance of the coating. Finally, multiple benzene ring structures are introduced into the weather resistance aid, which not only further improves the heat resistance of the coating but also enhances the compatibility with bisphenol A epoxy resin.

[0015] The present invention also proposes a preparation method of a high weather resistance epoxy coating, including the following steps: Step A1: Add bisphenol A epoxy resin, phenolic resin, curing accelerator, pigment, antioxidant, and weather resistance aid into a high-speed mixer, stir and mix evenly to obtain a mixed material; Step A2: Transfer the mixed material obtained in step A1 to a twin-screw extruder to fully melt and mix the materials in the extruder to form a uniform molten material; Step A3: Rapidly cool the molten material obtained in Step A2 through a cooling press to cool and solidify the material into sheet-shaped material, and then crush it in a pulverizer, screen it, and remove larger particles to obtain a highly weather-resistant epoxy coating.

[0016] As a further technical solution, the rotation speed of stirring in Step A1 is 800 - 1000 r / min, and the stirring time is 10 - 15 min.

[0017] As a further technical solution, in Step A2, the temperature of the first zone of the twin-screw extruder is 90 - 100 °C, the temperature of the second zone is 100 - 110 °C, the temperature of the third zone is 110 - 120 °C, the temperature of the fourth zone is 120 - 130 °C, and the temperature of the fifth zone is 130 - 140 °C.

[0018] As a further technical solution, in Step A3, the temperature of the cooling roller in the cooling press is 20 - 30 °C.

[0019] As a further technical solution, in Step A3, the mesh number of screening is a sieve with 80 - 100 meshes.

[0020] The prepared coating is a powder coating. Compared with solvent-based coatings, it has no solvent pollution, lower VOC, and is more environmentally friendly.

[0021] Advantages of the present invention: 1. The self-made weather-resistant additive of the present invention can significantly improve the heat resistance and anti-ultraviolet performance of the coating, reduce the damage of ultraviolet rays to the coating, and delay aging phenomena such as powdering and fading. 2. The present invention adds a hindered phenol antioxidant, which can inhibit the damage of oxidation reaction to the coating and extend the service life of the coating in an oxidative environment. 3. Phenolic resin and bisphenol A epoxy resin form a dense cross-linked structure under the action of a curing accelerator, further improving the thermal stability of the coating, which can withstand the thermal stress changes in a high-temperature environment and avoid problems such as softening, decomposition, and foaming. 4. The prepared coating is a powder coating, which avoids the use of organic solvents in traditional solvent-based epoxy coatings, reduces environmental pollution and harm to human health, and meets the requirements of environmental protection regulations. In summary, the coating prepared by the present invention improves the weather resistance of the coating from multiple aspects of antioxidant, heat resistance, and anti-ultraviolet, and is environmentally friendly, having important application value in the technical field of epoxy coatings. Specific embodiments

[0022] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0023] Embodiment 1 Preparation of weather-resistant additive: Step B1: In a three-necked flask equipped with a thermometer, a condenser, and a magnetic stirrer, first add 150 mL of anhydrous toluene. Under a nitrogen atmosphere and an ice bath condition of 0 °C, sequentially add 18.2 g of cyanuric chloride, 36.1 g of resorcinol, and 2.2 g of aluminum trichloride. Stir magnetically for 10 min, remove the ice bath, and heat the device to 78 °C. Stir and react for 5 h. After the reaction is completed, extract with dichloromethane. After combining the organic phases, wash with saturated sodium bicarbonate until neutral. Rotate and evaporate to remove toluene. Recrystallize the residue with hot ethanol to obtain product A; Step B2: In a three-necked flask equipped with a thermometer, a condenser, and a magnetic stirrer, add 40.2 g of 2-aminobenzotriazole, 30.3 g of triethylamine, 300 mL of anhydrous toluene, and 38.1 g of 1,3-dichloropropane. After stirring magnetically for 20 min, introduce nitrogen as a protective gas and heat the device. When the temperature reaches 70 °C, stir and react at this temperature for 3 h. After the reaction is completed, perform rotary evaporation and column chromatography purification to obtain product B; Step B3: In a three-necked flask equipped with a thermometer, a constant-pressure dropping funnel, a condenser, and a magnetic stirrer, first add 200 mL of anhydrous toluene and displace the air with nitrogen. Sequentially add 40.5 g of product A and 62.9 g of product B to the flask. Then mix 11.9 g of sodium hydroxide and 30 mL of deionized water, stir until the sodium hydroxide is completely dissolved, and then use a constant-pressure dropping funnel to add it to the flask. Then heat the device. When the temperature reaches 75 °C, keep the temperature and react for 8 h. After the reaction is completed, filter while it is hot, perform rotary evaporation, column chromatography purification, and drying to obtain the weather-resistant additive.

[0024] Embodiment 2 Preparation of highly weather-resistant epoxy coating: Step A1: Add 80 g of bisphenol A epoxy resin E-12, 30 g of linear phenolic resin (produced by Shandong Shengquan Group, model PF-6601), 1 g of 2-methylimidazole, 15 g of phthalocyanine blue, 3 g of antioxidant 1010, and 4 g of the weather-resistant additive prepared in Embodiment 1 to a high-speed mixer. Stir at a speed of 800 r / min for 10 min to obtain a mixture; Step A2: Transfer the mixture obtained in Step A1 to a twin-screw extruder (the temperature of the first zone of the twin-screw extruder is 90 - 100 °C, the second zone is 100 - 110 °C, the third zone is 110 - 120 °C, the fourth zone is 120 - 130 °C, and the fifth zone is 130 - 140 °C) to fully melt and mix the materials in the extruder to form a uniform molten material; Step A3: Quickly cool the molten material obtained in Step A2 through a cooling press (the temperature of the cooling roller is 20 °C) to cool and solidify the material into a sheet material, then crush it in a crusher and pass it through a 80-mesh sieve to remove larger particles, obtaining a highly weather-resistant epoxy coating.

[0025] Example 3 Preparation of a highly weather-resistant epoxy coating: Step A1: Add 90 g of bisphenol A epoxy resin E-12, 34 g of linear phenolic resin (produced by Shandong Shengquan Group, model PF-6601), 2 g of 2-methylimidazole, 19 g of phthalocyanine blue, 4 g of antioxidant 1010, and 8 g of the weather-resistant additive prepared in Example 1 to a high-speed mixer, and stir at a speed of 900 r / min for 15 min to obtain a mixture; Step A2: Transfer the mixture obtained in Step A1 to a twin-screw extruder (the temperature of the first zone of the twin-screw extruder is 90 - 100 °C, the second zone is 100 - 110 °C, the third zone is 110 - 120 °C, the fourth zone is 120 - 130 °C, and the fifth zone is 130 - 140 °C) to fully melt and mix the materials in the extruder to form a uniform molten material; Step A3: Quickly cool the molten material obtained in Step A2 through a cooling press (the temperature of the cooling roller is 20 - 30 °C) to cool and solidify the material into a sheet material, then crush it in a crusher and pass it through a 90-mesh sieve to remove larger particles, obtaining a highly weather-resistant epoxy coating.

[0026] Example 4 Preparation of a highly weather-resistant epoxy coating: Step A1: Add 100 g of bisphenol A epoxy resin E-12, 38 g of linear phenolic resin (produced by Shandong Shengquan Group, model PF-6601), 3 g of 2-ethyl-4-methylimidazole, 23 g of phthalocyanine green, 5 g of antioxidant 1010, and 12 g of the weather-resistant additive prepared in Example 1 to a high-speed mixer, and stir at a speed of 1000 r / min for 15 min to obtain a mixture; Step A2: Transfer the mixture obtained in Step A1 to a twin-screw extruder (the temperature of the first zone of the twin-screw extruder is 90 - 100 °C, the second zone is 100 - 110 °C, the third zone is 110 - 120 °C, the fourth zone is 120 - 130 °C, and the fifth zone is 130 - 140 °C) to fully melt and mix the materials in the extruder, forming a uniform molten material; Step A3: Quickly cool the molten material obtained in Step A2 through a cooling press (the temperature of the cooling roller is 20 - 30 °C) to cool and solidify the material into a sheet-like material, and then crush it in a crusher and pass it through a 100-mesh sieve to remove larger particles, obtaining a highly weather-resistant epoxy coating.

[0027] Comparative Example 1 Use the commercially available ultraviolet absorber UV-1 to replace the weather-resistant additive in Example 4, and the remaining steps are the same as those in Example 4.

[0028] Comparative Example 2 Use the commercially available epoxy resin powder coating produced by Guorun Hengke.

[0029] Perform performance tests on Examples 2, 3, 4 and Comparative Examples 1 and 2, and the measured results are shown in the following table: As can be seen from the above table, for the coatings prepared in the examples of the present invention, due to the addition of the self-made weather-resistant additive of the present invention, their ultraviolet resistance and heat resistance are higher than those of the comparative examples. Therefore, the present invention has important application value in the technical field of epoxy coatings.

[0030] In the description of the specification, the description with reference to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0031] The above content is only an example and explanation of the present invention. Those skilled in the art of the present technology make various modifications or supplements to the described specific embodiments or use similar methods for substitution, which should all fall within the protection scope of the present invention.

Claims

1. A high weather-resistant epoxy coating, characterized in that, It comprises the following raw materials in parts by weight: 80 - 100 parts of bisphenol A epoxy resin, 30 - 38 parts of phenolic resin, 1 - 3 parts of curing accelerator, 15 - 23 parts of pigment, 3 - 5 parts of antioxidant, and 4 - 12 parts of weather resistance aid; Among them, the weather resistance aid is prepared through the following steps: Step B1: In a flask, add anhydrous toluene. Under a nitrogen atmosphere and ice bath conditions, successively add cyanuric chloride, resorcinol, and aluminum trichloride. After stirring, stir and react at 78 °C for 5 h. After the reaction is completed, product A is obtained; Step B2: In a flask, add 2 - aminobenzotriazole, triethylamine, anhydrous toluene, and 1,3 - dichloropropane. After stirring, introduce nitrogen, and stir and react at 70 °C for 3 h. After the reaction is completed, product B is obtained; Step B3: In a flask, add anhydrous toluene, and displace the air with nitrogen; successively add product A and product B to the flask, then mix sodium hydroxide and deionized water and add them to the flask. React at 75 °C for 8 h. After the reaction is completed, the weather resistance aid is obtained.

2. The high weather-resistant epoxy coating according to claim 1, wherein In step B1, the dosage ratio of anhydrous toluene, cyanuric chloride, resorcinol, and aluminum trichloride is 150 mL:18.2 g:36.1 g:2.2 g.

3. The high weather-resistant epoxy coating according to claim 1, characterized in that In step B2, the dosage ratio of 2 - aminobenzotriazole, triethylamine, anhydrous toluene, and 1,3 - dichloropropane is 13.4 g:10.1 g:100 mL:12.7 g.

4. The high weather-resistant epoxy coating according to claim 1, wherein In step B3, the dosage ratio of anhydrous toluene, product A, product B, sodium hydroxide, and deionized water is 200 mL:40.5 g:62.9 g:11.9 g:30 mL.

5. A highly weather-resistant epoxy coating according to claim 1, characterized in that, The curing accelerator is one of 2 - methylimidazole and 2 - ethyl - 4 - methylimidazole.

6. The high weather-resistant epoxy coating according to claim 1, wherein, The antioxidant is a hindered phenol antioxidant.

7. A preparation method of a highly weather-resistant epoxy coating according to any one of claims 1-6, characterized in that, It comprises the following steps: Step A1: Stir and mix bisphenol A epoxy resin, phenolic resin, curing accelerator, pigment, antioxidant, and weather resistance aid evenly to obtain a mixed material; Step A2: Transfer the mixed material obtained in step A1 to a twin - screw extruder to make the material fully melt and mix in the extruder to form a uniform molten material; Step A3: Quickly cool the molten material obtained in step A2 through a cooling press to cool and solidify the material, then crush it and sieve it to obtain a high - weather - resistant epoxy coating.

Images