A high weather-resistant epoxy coating and preparation method thereof

Abstract

The invention discloses a high weather-resistant epoxy coating and a preparation method thereof, and belongs to the technical field of epoxy coatings. It comprises the following raw materials in parts by weight: 80-100 parts of bisphenol A type 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-resistant additive. Wherein, the weather-resistant additive can significantly improve the heat resistance and UV resistance of the coating, and the hindered phenolic antioxidant can suppress the damage of the oxidation reaction to the coating; the phenolic resin and the bisphenol A type epoxy resin form a dense cross-linked structure under the action of the curing accelerator, further improving the thermal stability of the coating, and the prepared coating is a powder coating, which avoids reducing pollution to the environment and harm to human health. In summary, the coating prepared by the present invention improves the weather resistance of the coating from multiple aspects of anti-oxidation, heat resistance and UV resistance, and 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 in particular relates to a highly weather-resistant epoxy coating and a preparation method thereof. Background Art

[0002] In modern industry and construction, coatings are widely used, and their performance directly affects the service life and appearance quality of the coated objects. Epoxy coatings, with their excellent adhesion, hardness, chemical resistance and other characteristics, occupy an important position in many fields such as anti-corrosion and decoration. However, with the increasing complexity of the industrial environment and the increase in the service life of outdoor facilities, higher requirements are placed on the weather resistance of epoxy coatings. When traditional epoxy coatings are exposed to outdoor environments for a long time, they will be corroded by various factors such as ultraviolet rays, rain, wind and sand, high and low temperature cycles, etc., causing the coating to become powdered, cracked, and faded, resulting in a decrease in its protective performance and a shortened service life, thereby losing its 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] Furthermore, ordinary epoxy coatings soften and decompose in high-temperature environments, causing a sharp decline in the coating's physical and mechanical properties, leading to blistering and flaking, making them ineffective in protecting the substrate and potentially posing safety risks. For example, in oil refining plants, where pipe and equipment surface temperatures sometimes exceed 150°C, ordinary epoxy coatings struggle to provide long-term, stable protection. Furthermore, on high-temperature furnaces, chimneys, and other facilities, ordinary epoxy coatings are unable to withstand the thermal stress changes associated with high temperatures.

[0004] While there are currently several technologies and products on the market designed to improve the weather and heat resistance of epoxy coatings, they still have many shortcomings. Some improvements involve adding additives such as UV absorbers and light stabilizers to enhance weather resistance, while heat-resistant fillers or additives are added to improve heat resistance. However, these additives lack synergistic effects, resulting in insufficient performance. Furthermore, the addition of multiple additives can affect the homogeneity of epoxy coatings.

[0005] Finally, traditional epoxy resin coatings are solvent-based, have 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 demands in the field of epoxy coating technology. 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 through the following technical solutions:

[0008] A highly weather-resistant epoxy coating 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-resistant auxiliary agent.

[0009] As a further technical solution, the curing accelerator is one of 2-methylimidazole and 2-ethyl-4-methylimidazole.

[0010] As a further technical solution, the antioxidant is a hindered phenol antioxidant.

[0011] The phenolic resin of the present invention can form a dense cross-linked structure with bisphenol A epoxy resin under the action of a curing accelerator after curing, greatly improving the heat resistance of the coating and enhancing its weather resistance. In addition, the added hindered phenolic antioxidant can capture free radicals and improve the antioxidant performance of the coating.

[0012] As a further technical solution, the weathering agent is prepared by the following steps:

[0013] Step B1: In a three-necked flask equipped with a thermometer, a condenser, and a magnetic stirrer, anhydrous toluene is first added. Under a nitrogen atmosphere and an ice bath at 0°C, cyanuric chloride, resorcinol, and aluminum chloride are added in sequence. The mixture is magnetically stirred for 10-15 minutes. The ice bath is removed, and the temperature of the apparatus is raised to 78°C (oil bath temperature control ±2°C). The mixture is stirred for 5 hours. After the reaction is complete, the mixture is extracted with dichloromethane, the organic phases are combined, and then washed with saturated sodium bicarbonate until neutral. The toluene is removed by rotary evaporation, and the residue is recrystallized from hot ethanol to obtain product A.

[0014] As a further technical solution, in step B1, the ratio of anhydrous toluene, cyanuric chloride, resorcinol, and aluminum chloride is 150 mL: 18.2 g: 36.1 g: 2.2 g.

[0015] In step B1, cyanuric chloride and resorcinol undergo an alkylation reaction under the catalysis of aluminum chloride, and the two are combined in a molar ratio of 1:3; the reaction formula is as follows:

[0016]

[0017] Step B2: Add 2-aminobenzotriazole, triethylamine, anhydrous toluene, and 1,3-dichloropropane to a three-necked flask equipped with a thermometer, a condenser, and a magnetic stirrer. After magnetic stirring for 10-20 minutes, introduce nitrogen as a protective gas and heat the apparatus. When the temperature reaches 70°C, magnetic stirring is carried out at this temperature for 3 hours. After completion of the reaction, rotary evaporation and column chromatography purification are performed to obtain product B.

[0018] As a further technical solution, the ratio of 2-aminobenzotriazole, triethylamine, anhydrous toluene, and 1,3-dichloropropane used in step B2 is 13.4 g:10.1 g:100 mL:12.7 g.

[0019] In step B2, 2-aminobenzotriazole and 1,3-dichloropropane undergo a nucleophilic substitution reaction under the catalysis of triethylamine. The two are coordinated in a 1:1 molar ratio. 1,3-dichloropropane is slightly excessive to reduce side reactions. The reaction formula is as follows:

[0020]

[0021] Step B3, in a three-necked flask equipped with a thermometer, a constant pressure dropping funnel, a condenser and a magnetic stirrer, anhydrous toluene is first added, and the air is replaced by nitrogen; Product A and Product B are added to the flask in sequence, and then sodium hydroxide and deionized water are mixed and stirred until the sodium hydroxide is completely dissolved, and then added to the flask using a constant pressure dropping funnel, and then the device is heated. When the temperature reaches 75°C, the reaction is kept warm for 8 hours. After the reaction is complete, the mixture is filtered while hot, rotary evaporated, purified by column chromatography, and dried to obtain a weathering additive;

[0022] As a further technical solution, the ratio of anhydrous toluene, product A, product B, sodium hydroxide and deionized water in step B3 is 200 mL:40.5 g:62.9 g:11.9 g:30 mL.

[0023] In step B3, sodium hydroxide can react with the phenolic hydroxyl group at the para position in the product A molecule to form a more nucleophilic sodium phenolate, which then reacts with the chlorine atom on the product B molecule; the two are combined in a molar ratio of 1:3; the reaction formula is as follows:

[0024]

[0025] The weathering agent prepared by the present invention is a triazine anti-ultraviolet agent. 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 anti-ultraviolet agent, the π-π conjugated system in the anti-ultraviolet agent molecule can absorb the energy of ultraviolet photons, causing the molecule to transition from a ground state to an excited state, and releasing the absorbed ultraviolet energy back to the environment in the form of harmless heat energy, fluorescence or phosphorescence, thereby greatly improving the anti-ultraviolet performance of the coating. In addition, the weathering agent molecule also contains a triazole ring group. The CN bond and the NN bond in the triazole ring have high bond energy and are not easy to break, thereby greatly improving the heat resistance of the coating. Finally, multiple benzene ring structures are introduced into the weathering agent, which not only further improves the heat resistance of the coating but also enhances the compatibility with bisphenol A epoxy resin.

[0026] The present invention also provides a method for preparing a highly weather-resistant epoxy coating, comprising the following steps:

[0027] Step A1: adding bisphenol A epoxy resin, phenolic resin, curing accelerator, pigment, antioxidant and weathering agent into a high-speed mixer, stirring and mixing uniformly to obtain a mixture;

[0028] Step A2: transferring the mixed material obtained in step A1 to a twin-screw extruder so that the material is fully melt-mixed in the extruder to form a uniform molten material;

[0029] Step A3: The molten material obtained in step A2 is quickly cooled by a cooling tablet press to allow the material to cool and solidify to form a flake material, which is then crushed in a grinder and sieved to remove larger particles to obtain a highly weather-resistant epoxy coating.

[0030] As a further technical solution, the stirring speed in step A1 is 800-1000 r / min, and the stirring time is 10-15 min.

[0031] As a further technical solution, in step A2, the temperature of zone 1 of the twin-screw extruder is 90-100°C, the temperature of zone 2 is 100-110°C, the temperature of zone 3 is 110-120°C, the temperature of zone 4 is 120-130°C, and the temperature of zone 5 is 130-140°C.

[0032] As a further technical solution, in step A3, the temperature of the cooling roller in the cooling tablet press is 20-30°C.

[0033] As a further technical solution, the mesh size of the sieve in step A3 is 80-100 mesh.

[0034] The prepared coating is a powder coating, which has no solvent pollution, lower VOC and is more environmentally friendly than solvent-based coatings.

[0035] Beneficial effects of the present invention:

[0036] 1. The self-made weathering additive of the present invention can significantly improve the heat resistance and UV resistance of the coating, reduce the damage of ultraviolet rays to the coating, and delay aging phenomena such as powdering and fading;

[0037] 2. The present invention adds hindered phenol antioxidants, which can inhibit the damage of oxidation reaction to the coating and extend the service life of the coating in an oxidizing environment;

[0038] 3. Phenolic resin and bisphenol A epoxy resin form a dense cross-linked structure under the action of curing accelerator, which further improves the thermal stability of the coating, can withstand thermal stress changes in high temperature environment, and avoid problems such as softening, decomposition, and blistering;

[0039] 4. The prepared coating is a powder coating, which avoids the use of organic solvents in traditional solvent-based epoxy coatings, reduces pollution to the environment and harm to human health, and complies with environmental protection regulations.

[0040] In summary, the coating prepared by the present invention improves the weather resistance of the coating from multiple aspects such as anti-oxidation, heat resistance and UV resistance, and is environmentally friendly, and has important application value in the field of epoxy coating technology. DETAILED DESCRIPTION

[0041] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0042] Example 1

[0043] Preparation of weathering additives:

[0044] Step B1, in a three-necked flask equipped with a thermometer, a condenser and a magnetic stirrer, 150 mL of anhydrous toluene was first added, and under a nitrogen atmosphere and an ice bath at 0°C, 18.2 g of cyanuric chloride, 36.1 g of resorcinol and 2.2 g of aluminum chloride were added in sequence. The mixture was magnetically stirred for 10 minutes, the ice bath was removed, and the apparatus was heated to 78°C. The mixture was stirred for 5 hours. After the reaction was complete, the mixture was extracted with dichloromethane, the organic phases were combined and washed with saturated sodium bicarbonate until neutral, the toluene was removed by rotary evaporation, and the residue was recrystallized from hot ethanol to obtain product A;

[0045] Step B2, in a three-necked flask equipped with a thermometer, a condenser and a magnetic stirrer, 40.2 g of 2-aminobenzotriazole, 30.3 g of triethylamine, 300 mL of anhydrous toluene and 38.1 g of 1,3-dichloropropane were added, and after magnetic stirring for 20 minutes, nitrogen was introduced as a protective gas and the device was heated. When the temperature reached 70°C, the reaction was magnetically stirred at this temperature for 3 hours. After the reaction was completed, rotary evaporation and column chromatography purification were performed to obtain product B;

[0046] 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 replace the air with nitrogen; 40.5 g of product A and 62.9 g of product B are added to the flask in sequence, and then 11.9 g of sodium hydroxide and 30 mL of deionized water are mixed and stirred until the sodium hydroxide is completely dissolved, and then a constant pressure dropping funnel is used to add it to the flask, and then the device is heated. When the temperature reaches 75 ° C, the reaction is kept warm for 8 hours. The reaction is complete, filtered while hot, rotary evaporated, purified by column chromatography, and dried to obtain a weathering additive.

[0047] Example 2

[0048] Preparation of highly weather-resistant epoxy coatings:

[0049] Step A1: 80 g of bisphenol A epoxy resin E-12, 30 g of novolac 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 weathering agent prepared in Example 1 were added to a high-speed mixer and stirred at a speed of 800 r / min for 10 min to obtain a mixture;

[0050] Step A2: transferring the mixed material 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 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.) so that the materials are fully melted and mixed in the extruder to form a uniform molten material;

[0051] Step A3: The molten material obtained in step A2 is rapidly cooled by a cooling tablet press (the cooling roller temperature is 20° C.) to allow the material to cool and solidify into a flake material, which is then crushed in a grinder and passed through an 80-mesh sieve to remove larger particles to obtain a highly weather-resistant epoxy coating.

[0052] Example 3

[0053] Preparation of highly weather-resistant epoxy coatings:

[0054] Step A1: 90 g of bisphenol A epoxy resin E-12, 34 g of novolac 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 weathering agent prepared in Example 1 were added to a high-speed mixer and stirred at a speed of 900 r / min for 15 min to obtain a mixture;

[0055] Step A2: transferring the mixed material 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 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.) so that the materials are fully melted and mixed in the extruder to form a uniform molten material;

[0056] Step A3: The molten material obtained in step A2 is rapidly cooled by a cooling tablet press (the cooling roller temperature is 20-30°C) to allow the material to cool and solidify into a flake material, which is then crushed in a grinder and passed through a 90-mesh sieve to remove larger particles to obtain a highly weather-resistant epoxy coating.

[0057] Example 4

[0058] Preparation of highly weather-resistant epoxy coatings:

[0059] Step A1: 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 weathering agent prepared in Example 1 were added to a high-speed mixer and stirred at a speed of 1000 r / min for 15 min to obtain a mixture;

[0060] Step A2: transferring the mixed material 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 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.) so that the materials are fully melted and mixed in the extruder to form a uniform molten material;

[0061] Step A3: The molten material obtained in step A2 is rapidly cooled by a cooling tablet press (the cooling roller temperature is 20-30°C) to allow the material to cool and solidify into a flake material, which is then crushed in a grinder and passed through a 100-mesh sieve to remove larger particles to obtain a highly weather-resistant epoxy coating.

[0062] Comparative Example 1

[0063] The commercially available ultraviolet absorber UV-1 was used to replace the weathering agent in Example 4, and the remaining steps were the same as those in Example 4.

[0064] Comparative Example 2

[0065] A commercially available epoxy resin powder coating produced by Guorun Hengke was used.

[0066] The performance tests of Examples 2, 3, and 4 and Comparative Examples 1 and 2 were carried out, and the results are shown in the following table:

[0067]

[0068] As can be seen from the above table, the coatings prepared in the embodiments of the present invention have higher UV resistance and heat resistance than the comparative examples due to the addition of the self-made weathering additive of the present invention. Therefore, the present invention has important application value in the field of epoxy coating technology.

[0069] Throughout the specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0070] The above contents are merely examples and explanations of the present invention. Any modifications or additions made by those skilled in the art to the described specific embodiments, or replacements made in a similar manner, shall fall within the scope of protection of the present invention.

Claims

1. A highly weather-resistant epoxy coating, characterized in that: The invention 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 weathering agent; Wherein, the weathering additive is prepared by the following steps: Step B1: In a flask, add anhydrous toluene, and under nitrogen atmosphere and ice bath conditions, add cyanuric chloride, resorcinol and aluminum chloride in sequence, stir, and react at 78° C. for 5 hours. The reaction is completed to obtain product A; Step B2: Add 2-aminobenzotriazole, triethylamine, anhydrous toluene and 1,3-dichloropropane to a flask, stir, introduce nitrogen, and stir at 70° C. for 3 h. The reaction is completed to obtain product B; Step B3: Add anhydrous toluene to a flask and replace the air with nitrogen; add product A and product B to the flask in sequence, then mix sodium hydroxide and deionized water, add the mixture to the flask, and react at 75° C. for 8 hours. The reaction is completed to obtain a weathering agent; Among them, the ratio of anhydrous toluene, cyanuric chloride, resorcinol and aluminum chloride in step B1 is 150mL:18.2g:36.1g:2.2g; the ratio of 2-aminobenzotriazole, triethylamine, anhydrous toluene and 1,3-dichloropropane in step B2 is 13.4g:10.1g:100mL:12.7g; the ratio of anhydrous toluene, product A, product B, sodium hydroxide and deionized water in step B3 is 200mL:40.5g:62.9g:11.9g:30mL.

2. 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.

3. A highly weather-resistant epoxy coating according to claim 1, characterized in that: The antioxidant is a hindered phenol antioxidant.

4. The method for preparing a highly weather-resistant epoxy coating according to any one of claims 1 to 3, wherein: The following steps are involved: Step A1: Stir and mix bisphenol A epoxy resin, phenolic resin, curing accelerator, pigment, antioxidant and weathering agent to obtain a mixture; Step A2: transferring the mixed material obtained in step A1 to a twin-screw extruder so that the material is fully melt-mixed in the extruder to form a uniform molten material; Step A3: The molten material obtained in step A2 is quickly cooled by a cooling tablet press to solidify the material, and then crushed and sieved to obtain a highly weather-resistant epoxy coating.

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