Epoxy resin composite coating and preparation method thereof

Abstract

The invention relates to the field of coatings, and particularly discloses an epoxy resin composite coating and a preparation method thereof.The epoxy resin composite coating comprises a component A and a component B. The component A comprises hydrogenated bisphenol A epoxy resin, a solvent, filler, a defoaming agent, a flatting agent, a dispersing agent and a toughening agent; the component B comprises the following raw materials in parts by weight: a curing agent and a diluent; wherein the toughening agent in the component A comprises a nano montmorillonite-polyurethane microsphere compound and modified nano silicon dioxide, and the modified nano silicon dioxide is prepared by taking nano silicon dioxide as a core material, taking an acrylate layer as an inner core layer and taking a siloxane layer as a shell layer; the preparation method comprises the following steps: mixing hydrogenated bisphenol A epoxy resin with a solvent, adding the rest raw materials of the component A, and mixing to obtain the component A; and mixing the curing agent with the diluent to obtain the component B. The bisphenol A type epoxy resin composite coating has the characteristic of further improving the impact resistance, especially the low-temperature impact resistance, of the bisphenol A type epoxy resin composite coating.

Description

Technical Field

[0001] The present invention relates to the field of coatings, and more specifically, to an epoxy resin composite coating and a preparation method thereof. Background Art

[0002] Epoxy resins, an important class of thermosetting resins, are widely used in coatings, adhesives, composite materials, and electronic packaging due to their excellent mechanical properties, adhesion, chemical resistance, and electrical insulation. Among them, bisphenol A epoxy resin, due to the presence of benzene rings and ether bonds in its structure, offers excellent heat resistance and impact resistance, making it one of the most widely used epoxy resins.

[0003] However, with the continuous improvement of industrial technology and environmental protection requirements, traditional epoxy resins have problems such as slow curing speed, poor weather resistance, and high brittleness. In particular, traditional bisphenol A epoxy resin molecules contain unsaturated double bonds, which are prone to breakage under ultraviolet light or heat, causing the material to yellow and become brittle, making it difficult to meet the comprehensive requirements of high-performance coating materials for mechanical properties and other indicators.

[0004] Compared with traditional bisphenol A epoxy resin, hydrogenated bisphenol A epoxy resin converts double bonds into saturated bonds through a hydrogenation process to form a stable six-membered ring structure. As an epoxy resin that does not contain double bonds in its molecular structure, it has advantages such as good weather resistance. The physical properties of the cured product are similar to those of bisphenol A epoxy resin. As a weather-resistant epoxy resin, it is suitable for outdoor occasions with high weather resistance requirements.

[0005] Although hydrogenation treatment reduces the brittleness of traditional bisphenol A epoxy resin, hydrogenated bisphenol A epoxy resin has a rigid molecular structure and large internal stress inside the cured coating. When subjected to external impact, these factors work together to make the cured coating brittle and have poor impact resistance. It is prone to cracking and even peeling. In particular, its limited low-temperature impact resistance causes microcracks and peeling in the coating at low temperatures, affecting its long-term reliability.

[0006] Therefore, how to further improve the impact resistance of bisphenol A epoxy resin composite coatings, especially the low-temperature impact resistance, is of great significance to the service life and reliability of the coating. Summary of the Invention

[0007] In order to further improve the impact resistance, especially the low-temperature impact resistance, of a bisphenol A epoxy resin composite coating, the present application provides an epoxy resin composite coating and a preparation method thereof.

[0008] In a first aspect, the present application provides an epoxy resin composite coating, which adopts the following technical solution: An epoxy resin composite coating comprises component A and component B, wherein component A comprises the following raw materials in parts by weight: 60-75 parts of hydrogenated bisphenol A epoxy resin, 15-25 parts of solvent, 20-30 parts of filler, 0.2-0.5 parts of defoamer, 0.3-0.8 parts of leveling agent, 0.5-1 parts of dispersant and 5-10 parts of toughening agent; Component B includes the following raw materials in parts by weight: 45-55 parts of curing agent and 5-10 parts of diluent; Among them, the toughening agent in component A includes a nano-montmorillonite-polyurethane microsphere composite and modified nano-silica in a mass ratio of 1: (1.3-1.5). The modified nano-silica is made of nano-silica as the core material, an acrylate layer as the inner core layer and a silicone layer as the outer shell layer.

[0009] By adopting the above technical solution, the composite coating in this application uses hydrogenated bisphenol A epoxy resin as the base resin. The hydrogenation treatment of the benzene ring in its molecular structure reduces the rigidity of the bisphenol A epoxy resin, which has higher flexibility and impact resistance. In this technology, a toughening agent is also added in this application, and the toughening agent includes a nano-montmorillonite-polyurethane microsphere composite and modified nano-silica. Compared with the traditional use of rubber particles or thermoplastic resin as a toughening agent, it improves the impact resistance of the epoxy resin while also reducing its hardness and wear resistance. In this application, nano-montmorillonite is used as a rigid particle component. When the coating is impacted, the nanoparticles prevent crack propagation and trigger a micro-crack toughening mechanism to absorb energy. Improve impact resistance; moreover, the layered structure of montmorillonite can disperse stress and prevent crack propagation, while the glass transition temperature and elastomeric properties of polyurethane microspheres can still maintain soft impact resistance in low temperature environments. Its compatibility with epoxy resin is achieved through the entanglement between molecular chains to form an "island structure", which can improve low-temperature impact resistance through elastic deformation. The addition of nano-montmorillonite-polyurethane microsphere composite forms a rigid-flexible gradient structure. Nano-montmorillonite is preferentially distributed at the front of crack propagation, inhibiting the opening of the crack tip, and polyurethane microspheres absorb impact energy through local plastic deformation. The synergistic effect of the two significantly improves the impact resistance of the composite coating without significantly reducing the hardness and wear resistance of the coating.

[0010] Modified nano-silica uses nano-silica as the core material, an acrylate layer as the inner core layer, and a siloxane layer as the outer layer. The addition of modified nano-silica not only utilizes its nano-effect to improve its impact resistance, but also acts as a rigid component to improve the coating's wear resistance and hardness. The acrylate layer of the modified nano-silica has good soft impact resistance and a certain degree of compatibility with epoxy resin. It can act as a bridge to alleviate the interfacial stress difference between the nano-silica core material and the epoxy resin matrix, allowing the nano-silica to be better dispersed in the epoxy resin. The siloxane layer can strengthen the interfacial bonding with the epoxy resin through hydrogen bonding and π-π interactions, reducing stress concentration, helping to tightly bond the nano-silica to the epoxy resin matrix, and further improving the coating's impact resistance.

[0011] Ultimately, the nano-montmorillonite-polyurethane microsphere composite and modified nano-silica in this application form a rigid-flexible gradient structure within the coating. The nano-montmorillonite has high rigidity and is primarily distributed at the crack propagation front, inhibiting crack tip opening. The polyurethane microspheres have good impact resistance and elasticity, absorbing impact energy through localized plastic deformation. The modified nano-silica falls somewhere in between, providing both a certain degree of rigidity to enhance coating strength and improving impact resistance through a microcrack toughening mechanism.

[0012] When impacted, the nano-montmorillonite first acts to inhibit crack initiation and expansion. The polyurethane microspheres then absorb some of the impact energy through plastic deformation. Simultaneously, the modified nano-silica further disperses stress, inducing microcrack toughening and preventing further crack growth. This multi-layered protection mechanism enables the coating to better withstand external impact and damage, significantly improving its service life and reliability.

[0013] Optionally, the nano-montmorillonite-polyurethane microsphere composite is prepared by the following method: The nano-montmorillonite is mixed with water and hydroxyethyl cellulose to prepare a suspension, and then a polyurethane prepolymer is added thereto. The suspension is ultrasonically treated for 20-30 minutes, allowed to stand for 20-24 hours, and filtered to obtain a nano-montmorillonite-polyurethane microsphere composite.

[0014] By adopting the above technical solution, nano-montmorillonite is mixed with water and hydroxyethyl cellulose, and the nano-montmorillonite is used as an adsorbent and physical support, and the hydroxyethyl cellulose is used as a dispersant and anti-settling agent to effectively prevent the agglomeration of the nano-montmorillonite particles and improve their dispersion stability. Then, a polyurethane prepolymer is added to form a polyurethane wrapped or loaded on the nano-montmorillonite in the solvent water, and finally the nano-montmorillonite-polyurethane microsphere composite is prepared. It is used as a toughening agent to significantly improve the impact resistance of the epoxy resin coating.

[0015] Optionally, when preparing the nano-montmorillonite-polyurethane microsphere composite, the mass ratio of nano-montmorillonite and water is 1: (2-3), the amount of hydroxyethyl cellulose added is 5-8wt% of the nano-montmorillonite, and the mass ratio of polyurethane prepolymer to nano-montmorillonite is 1: (1.8-2.2).

[0016] Optionally, the modified nano-silica is prepared by the following method: 1) Mix vinyltrimethoxysilane with water and ethanol, then add hydroxyethyl cellulose and nano-silica, adjust the pH to 4-5.5, heat to 50-60°C, stir for 60-90 minutes, filter and dry to obtain primary modified nano-silica; 2) Mix methyl methacrylate, hydroxyethyl acrylate and acrylic acid to prepare a monomer mixture, mix alkylphenol polyoxyethylene ether and water, then add primary modified nano-silica, heat to 60-70°C, add the monomer mixture and initiator, and then keep the temperature to react for 2-3 hours to form a primary emulsion with nano-silica as the core material and acrylate as the inner core layer; 3) Cool the primary emulsion to 30-40°C, then add vinyltrimethoxysilane and adjust the pH to 7.5-8.5 by adding ammonia water. After reacting for 3-4 hours, filter, wash with alcohol and dry to obtain modified nano-silica.

[0017] By adopting the above technical solution, vinyltrimethoxysilane is hydrolyzed under acidic conditions to generate silanol, which undergoes a condensation reaction with the hydroxyl groups on the surface of the nano-silica to form a siloxane bond, thereby introducing the vinyl group to the surface of the silica to form an active site. Then, under the action of an initiator, the acrylate monomer forms a polymer layer on the surface of the nano-silica to achieve the coating of the nano-silica, and the unsaturated double bond in the acrylate monomer forms a bond with the vinyl group, thereby achieving in-situ polymerization of the acrylate monomer on the surface of the nano-silica. Finally, after cooling, vinyltrimethoxysilane is added. Under alkaline conditions, its silane coupling agent is hydrolyzed to generate silanol, which undergoes a condensation reaction with the hydroxyl groups in the acrylate layer. At the same time, it can also form a chemical bond with acrylic acid to form an outer siloxane layer. Active groups such as vinyl in the siloxane layer can participate in the curing reaction of the epoxy resin, forming additional cross-linking points to increase its cross-linking density, thereby increasing its hardness. In addition, the flexible segments in the siloxane segments can also buffer the stress concentration at the crack tip and prevent the crack from expanding. Ultimately, the addition of the toughening agent in this application improves the impact resistance of the coating while retaining its better hardness and wear resistance.

[0018] Optionally, when preparing the modified nano-silica, the mass ratio of vinyltrimethoxysilane to water and ethanol in step 1) is 1:(3-4):(2-3), the amount of hydroxyethyl cellulose added is 3-5wt% of the vinyltrimethoxysilane, and the amount of nano-silica added is 4-6 times the mass of the vinyltrimethoxysilane; In step 2), the addition mass ratio of methyl methacrylate, hydroxyethyl acrylate and acrylic acid is 1: (0.6-0.8): (0.5-0.8), the addition mass ratio of alkylphenol polyoxyethylene ether and water is 1: (12-15), and the addition amount of alkylphenol polyoxyethylene ether is 0.3-0.5wt% of the primary modified nano-silica, the addition mass ratio of primary modified nano-silica to the monomer mixture is 1: (0.8-1), and the addition amount of initiator is 0.5-1wt% of the monomer mixture; In step 3), the amount of vinyltrimethoxysilane added is 8-10% of the initial nano-silica.

[0019] By adopting the above technical solution and using the above addition ratio to prepare modified nano-silica as a toughening agent in combination with a nano-montmorillonite-polyurethane microsphere composite, the coating has better impact resistance and better hardness and wear resistance.

[0020] Optionally, in the preparation process of modified nano-silica, in step 2), after adding the monomer mixture and the initiator and keeping the reaction for 1-2 hours, polyethylene glycol monomethyl ether is added, and the amount of polyethylene glycol monomethyl ether added is 3-5wt% of the initial modified nano-silica, and then the reaction is continued to form a primary emulsion.

[0021] By adopting the above technical scheme, when the primary modified nano-silica containing vinyl groups is reacted with the monomer mixture under the action of an initiator, the hydroxyl group in the polyethylene glycol monomethyl ether reacts with the carboxyl group of acrylic acid in the acrylate layer to introduce an ether bond into the polymer molecular chain, and then the hydroxyl group thereof reacts with the hydroxyl group on the nano-silica to achieve the anchoring of the ether bond on the silica. On the one hand, the ether bond can form a hydrogen bond with the epoxy group of the epoxy resin, etc., thereby improving the interfacial bonding force between the modified nano-silica and the epoxy resin matrix and effectively transferring stress. Moreover, the introduction of the ether bond increases the flexible chain segment on the surface of the nano-silica, which can deform when subjected to force, relieve stress concentration, and reduce the network density after the epoxy resin is cured. This steric hindrance effect at the molecular level enables the resin chain segment to obtain a higher degree of freedom of movement, thereby greatly improving the plastic deformation ability of the material during molding, and thereby improving the impact resistance of the coating.

[0022] Optionally, in component A, the defoaming agent is a silicone defoaming agent, the leveling agent is an acrylic leveling agent, the filler is nano-silica or carbon black, and the solvent is a mixture of xylene and butyl glycidyl ether in a mass ratio of 1: (0.2-0.3).

[0023] Optionally, the curing agent in component B is a polyamide curing agent and a polyetheramine curing agent in a mass ratio of 1: (0.3-0.4); the diluent is a mixture of xylene and butyl glycidyl ether in a mass ratio of 1: (0.2-0.3).

[0024] Optionally, the component B further comprises 0.5-1 parts by weight of triethanolamine.

[0025] By adopting the above technical solution, triethanolamine is used as a curing accelerator to accelerate the curing reaction and shorten the curing time.

[0026] In a second aspect, the present application provides a method for preparing an epoxy resin composite coating, which adopts the following technical solution: A method for preparing an epoxy resin composite coating comprises the following steps: Preparation of component A: Mix hydrogenated bisphenol A epoxy resin with a solvent, add the remaining raw materials of component A, and mix to prepare component A; Preparation of component B: Mix the curing agent and the diluent to prepare component B.

[0027] By adopting the above technical solution, the method provided by this application is simple, convenient and easy to industrialize.

[0028] In summary, this application has the following beneficial effects: 1. In this application, the nano-montmorillonite-polyurethane microsphere composite and modified nano-silica form a rigid-flexible gradient structure in the coating. Nano-montmorillonite has high rigidity and is mainly distributed at the crack propagation front, which plays a role in inhibiting the opening of the crack tip; polyurethane microspheres have good soft impact resistance and elasticity, absorbing impact energy through local plastic deformation; modified nano-silica is somewhere in between, with a certain degree of rigidity to enhance the coating strength, and can also improve the coating's impact resistance through the microcrack toughening mechanism; 2. When preparing modified nano-silica in the present application, when the primary modified nano-silica containing vinyl groups is reacted with the monomer mixture under the action of an initiator, the hydroxyl group in polyethylene glycol monomethyl ether reacts with the carboxyl group of acrylic acid in the acrylate layer to introduce an ether bond into the polymer molecular chain, and then cooperates with the hydroxyl group on the nano-silica to achieve the anchoring of the ether bond on the silica. On the one hand, its ether bond can form a hydrogen bond with the epoxy group of the epoxy resin, etc., thereby improving the interfacial bonding force between the modified nano-silica and the epoxy resin matrix and effectively transferring stress. Moreover, the introduction of the ether bond increases the flexible chain segment on the surface of the nano-silica, which can deform when subjected to force, relieve stress concentration, and reduce the network density after the epoxy resin is cured. This steric hindrance effect at the molecular level enables the resin chain segment to obtain a higher degree of freedom of movement, thereby greatly improving the plastic deformation ability of the material during molding, thereby improving the impact resistance of the coating. DETAILED DESCRIPTION

[0029] The present application is further described in detail below with reference to the examples. It is particularly noted that if no specific conditions are specified in the following examples, the reactions are carried out according to conventional conditions or the conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following examples can be obtained from common commercial sources.

[0030] In the following examples, the hydrogenated bisphenol A epoxy resin is a hydrogenated bisphenol A epoxy resin with an epoxy value of 0.51-0.54 eq / 100 g produced by Yantai Aolifu Chemical Co., Ltd. The defoaming agent is an organosilicon defoaming agent, specifically the organosilicon defoaming agent model th-5800 produced by Shandong Wanhua Tianhe New Materials Co., Ltd. The leveling agent is an acrylic leveling agent of model BYK-385; The dispersant used is Disperbyk-180.

[0031] The polyamide curing agent is polyamide curing agent 650 from Shandong Jinhong New Material Technology Co., Ltd. The polyetheramine curing agent used is a polyetheramine curing agent of model D230 produced by Shanghai Fuqi Industry and Trade Co., Ltd. and BASF.

[0032] The polyurethane prepolymer is a polyurethane prepolymer model HF131 purchased from Shenzhen Carbon Union Technology Co., Ltd.

[0033] The following preparation example is a preparation example of modified nano-silica In the following preparation examples, polyethylene glycol monomethyl ether was selected from polyethylene glycol monomethyl ether with product number 0708 from Shandong Tengbo Chemical Technology Co., Ltd.

[0034] Preparation Example 1 A method for preparing modified nano-silica comprises the following steps: 1) Vinyltrimethoxysilane was mixed with water and ethanol in a mass ratio of 1:3.5:2.5, and then hydroxyethyl cellulose and nano-silica were added. The pH was adjusted to 4.5, the temperature was raised to 55°C, and the mixture was stirred for 75 minutes. The mixture was filtered and dried to obtain primary modified nano-silica. The amount of hydroxyethyl cellulose added is 4wt% of vinyltrimethoxysilane, and the amount of nanosilica added is 5 times the mass of vinyltrimethoxysilane; 2) Methyl methacrylate, hydroxyethyl acrylate, and acrylic acid were mixed in a mass ratio of 1:0.7:0.6 to prepare a monomer mixture, alkylphenol polyoxyethylene ether OP-10 and water were mixed in a mass ratio of 1:14, and then the primary modified nano-silica prepared in step 1) was added. The temperature was raised to 65° C., and the monomer mixture and initiator ammonium persulfate were added. The mixture was then kept warm for 2.5 hours to form a primary emulsion with nano-silica as the core material and acrylate as the inner core layer; Among them, the addition amount of alkylphenol polyoxyethylene ether (OP-10) is 0.4wt% of the primary modified nano-silica, the addition mass ratio of primary modified nano-silica to monomer mixture is 1:0.9, and the addition amount of initiator is 0.8wt% of the monomer mixture; 3) Cool the primary emulsion to 35°C, then add vinyltrimethoxysilane in an amount of 9% of the primary modified nano-silica, and add ammonia water to adjust the pH to 8. After reacting for 3.5 hours, filter, wash with alcohol, and dry to obtain modified nano-silica.

[0035] Preparation Example 2 A method for preparing modified nano-silica comprises the following steps: 1) Vinyltrimethoxysilane was mixed with water and ethanol in a mass ratio of 1:3:2, and then hydroxyethyl cellulose and nano-silica were added. The pH was adjusted to 4, the temperature was raised to 50°C, and the mixture was stirred for 60 minutes. The mixture was filtered and dried to obtain primary modified nano-silica. The amount of hydroxyethyl cellulose added is 3wt% of vinyltrimethoxysilane, and the amount of nanosilica added is 4 times the mass of vinyltrimethoxysilane; 2) Methyl methacrylate, hydroxyethyl acrylate, and acrylic acid were mixed in a mass ratio of 1:0.6:0.5 to prepare a monomer mixture, alkylphenol polyoxyethylene ether OP-10 and water were mixed in a mass ratio of 1:12, and then the primary modified nano-silica prepared in step 1) was added. The temperature was raised to 60°C, and the monomer mixture and initiator ammonium persulfate were added. The mixture was then kept warm for 3 hours to form a primary emulsion with nano-silica as the core material and acrylate as the inner core layer; Among them, the addition amount of alkylphenol polyoxyethylene ether (OP-10) is 0.3wt% of the primary modified nano-silica, the addition mass ratio of primary modified nano-silica to monomer mixture is 1:0.8, and the addition amount of initiator is 0.5wt% of the monomer mixture; 3) Cool the primary emulsion to 30°C, then add vinyltrimethoxysilane, the amount of vinyltrimethoxysilane added is 8% of the primary modified nano-silica, and add ammonia water to adjust the pH to 7.5. After reacting for 3 hours, filter, wash with alcohol and dry to obtain modified nano-silica.

[0036] Preparation Example 3 A method for preparing modified nano-silica comprises the following steps: 1) Vinyltrimethoxysilane was mixed with water and ethanol in a mass ratio of 1:4:3, and then hydroxyethyl cellulose and nano-silica were added. The pH was adjusted to 5.5, the temperature was raised to 60°C, and the mixture was stirred for 60 minutes. The mixture was filtered and dried to obtain primary modified nano-silica. The amount of hydroxyethyl cellulose added is 5wt% of vinyltrimethoxysilane, and the amount of nanosilica added is 6 times the mass of vinyltrimethoxysilane; 2) Methyl methacrylate, hydroxyethyl acrylate, and acrylic acid are mixed in a mass ratio of 1:0.8:0.8 to prepare a monomer mixture, alkylphenol polyoxyethylene ether OP-10 and water are mixed in a mass ratio of 1:15, and then the primary modified nano-silica prepared in step 1) is added. The temperature is raised to 70°C, and the monomer mixture and initiator ammonium persulfate are added. The mixture is then kept warm for 2 hours to form a primary emulsion with nano-silica as the core material and acrylate as the inner core layer; Among them, the addition amount of alkylphenol polyoxyethylene ether (OP-10) is 0.5wt% of the primary modified nano-silica, the addition mass ratio of primary modified nano-silica to the monomer mixture is 1:1, and the addition amount of initiator is 1wt% of the monomer mixture; 3) Cool the primary emulsion to 40°C, then add vinyltrimethoxysilane, the amount of vinyltrimethoxysilane added is 10% of the primary modified nano-silica, and add ammonia water to adjust the pH to 8.5. After reacting for 4 hours, filter, wash with alcohol and dry to obtain modified nano-silica.

[0037] Preparation Example 4 A method for preparing modified silica is carried out according to the method in Preparation Example 1, except that in step 2), after adding a monomer mixture and an initiator and incubating for a reaction for 1.5 hours, polyethylene glycol monomethyl ether is also added, and the amount of polyethylene glycol monomethyl ether added is 4wt% of the initial modified nano-silica, and the reaction is continued for 1 hour to form a primary emulsion.

[0038] Preparation Example 5 A method for preparing modified silica is carried out according to the method in Preparation Example 1, except that in step 2), after adding a monomer mixture and an initiator and incubating for a reaction for 1.5 hours, polyethylene glycol monomethyl ether is also added, and the amount of polyethylene glycol monomethyl ether added is 3wt% of the initial modified nano-silica, and the reaction is continued for 1 hour to form a primary emulsion.

[0039] Preparation Example 6 A method for preparing modified silica is carried out according to the method in Preparation Example 1, except that in step 2), after adding a monomer mixture and an initiator and incubating for a reaction for 1.5 hours, polyethylene glycol monomethyl ether is also added, and the amount of polyethylene glycol monomethyl ether added is 5wt% of the initial modified nano-silica, and the reaction is continued for 1 hour to form a primary emulsion.

[0040] Preparation Example 7 A method for preparing modified silicon dioxide is carried out according to the method in Preparation Example 1, except that step 1) is not performed, and in step 2) an equal amount of the primary modified nano-silica is replaced with nano-silica.

[0041] Comparative Preparation Example 1 A method for preparing modified silicon dioxide is carried out according to the method in Preparation Example 1, except that step 3) is not performed, and the primary emulsion prepared in step 2) is filtered and then dried to prepare modified nano-silica.

[0042] Example 1 A method for preparing an epoxy resin composite coating comprises the following steps: Preparation of component A: 65 kg of hydrogenated bisphenol A epoxy resin was mixed with 20 kg of solvent, and then 8 kg of toughening agent, 25 kg of filler, 0.8 kg of dispersant, 0.5 kg of leveling agent and 0.3 kg of defoaming agent were added in sequence and stirred to prepare component A; Preparation of component B: Component B was prepared by mixing 50 kg of curing agent, 8 kg of diluent and 0.8 kg of triethanolamine.

[0043] The curing agent in component B is a mixture of a polyamide curing agent and a polyetheramine curing agent in a mass ratio of 1:0.35, and the diluent is a mixture of xylene and butyl glycidyl ether in a mass ratio of 1:0.25. The filler in component A is nano-silica, the solvent is a mixture of xylene and butyl glycidyl ether in a mass ratio of 1:0.25; the toughening agent is a mixture of nano-montmorillonite-polyurethane microsphere composite and modified nano-silica in a mass ratio of 1:1.4; The modified nano-silica was prepared using the modified nano-silica prepared in Preparation Example 1. The nano-montmorillonite-polyurethane microsphere composite was prepared by the following method: Nano-montmorillonite was mixed with water and hydroxyethyl cellulose to prepare a suspension, and then a polyurethane prepolymer was added. The suspension was ultrasonically treated for 25 minutes, allowed to stand for 25 hours, and filtered to obtain a nano-montmorillonite-polyurethane microsphere composite. The mass ratio of nano-montmorillonite to water was 1:2.5, and the amount of hydroxyethyl cellulose added was 6wt% of the nano-montmorillonite. The mass ratio of polyurethane prepolymer to nano-montmorillonite was 1:2.

[0044] Example 2 A method for preparing an epoxy resin composite coating comprises the following steps: Preparation of component A: 60 kg of hydrogenated bisphenol A epoxy resin was mixed with 15 kg of solvent, and then 5 kg of toughening agent, 20 kg of filler, 0.5 kg of dispersant, 0.3 kg of leveling agent and 0.2 kg of defoaming agent were added in sequence and stirred to prepare component A; Preparation of component B: Component B was prepared by mixing 45 kg of curing agent, 5 kg of diluent and 0.5 kg of triethanolamine.

[0045] The curing agent in component B is a mixture of a polyamide curing agent and a polyetheramine curing agent in a mass ratio of 1:0.3, and the diluent is a mixture of xylene and butyl glycidyl ether in a mass ratio of 1:0.2. The filler in component A is nano-silica, the solvent is a mixture of xylene and butyl glycidyl ether in a mass ratio of 1:0.2; the toughening agent is a mixture of nano-montmorillonite-polyurethane microsphere composite and modified nano-silica in a mass ratio of 1:1.3; The modified nano-silica was prepared in Preparation Example 2, and the nano-montmorillonite-polyurethane microsphere composite was prepared by the following method: Nano-montmorillonite was mixed with water and hydroxyethyl cellulose to prepare a suspension, and then a polyurethane prepolymer was added. After ultrasonic treatment for 20 minutes, the suspension was allowed to stand for 20 hours, and the nano-montmorillonite-polyurethane microsphere composite was obtained after filtration. The mass ratio of nano-montmorillonite to water was 1:2, and the amount of hydroxyethyl cellulose added was 5wt% of the nano-montmorillonite. The mass ratio of polyurethane prepolymer to nano-montmorillonite was 1:1.8.

[0046] Example 3 A method for preparing an epoxy resin composite coating comprises the following steps: Preparation of component A: 75 kg of hydrogenated bisphenol A epoxy resin was mixed with 25 kg of solvent, and then 10 kg of toughening agent, 30 kg of filler, 1 kg of dispersant, 0.8 kg of leveling agent and 0.5 kg of defoaming agent were added in sequence and stirred to prepare component A; Preparation of component B: Component B was prepared by mixing 55 kg of curing agent, 10 kg of diluent and 1 kg of triethanolamine.

[0047] The curing agent in component B is a mixture of a polyamide curing agent and a polyetheramine curing agent in a mass ratio of 1:0.4, and the diluent is a mixture of xylene and butyl glycidyl ether in a mass ratio of 1:0.3. The filler in component A is nano-silica, the solvent is a mixture of xylene and butyl glycidyl ether in a mass ratio of 1:0.3; the toughening agent is a mixture of nano-montmorillonite-polyurethane microsphere composite and modified nano-silica in a mass ratio of 1:1.5; The modified nano-silica was prepared in Preparation Example 3. The nano-montmorillonite-polyurethane microsphere composite was prepared by the following method: Nano-montmorillonite was mixed with water and hydroxyethyl cellulose to prepare a suspension, and then a polyurethane prepolymer was added. After ultrasonic treatment for 30 minutes, the suspension was allowed to stand for 24 hours, and the nano-montmorillonite-polyurethane microsphere composite was obtained after filtration. The mass ratio of nano-montmorillonite to water was 1:3, and the amount of hydroxyethyl cellulose added was 8wt% of the nano-montmorillonite. The mass ratio of polyurethane prepolymer to nano-montmorillonite was 1:2.2.

[0048] Examples 4-7 A method for preparing an epoxy resin composite coating is carried out according to the method in Example 1, except that the modified nano-silica is the modified nano-silica prepared in Preparation Examples 4-7.

[0049] Comparative Example 1 A method for preparing an epoxy resin composite coating is carried out according to the method in Example 1, except that the modified nano-silica is the modified nano-silica prepared in Comparative Preparation Example 1.

[0050] Comparative Example 2 A method for preparing an epoxy resin composite coating is carried out according to the method in Example 1, except that a nano-montmorillonite-polyurethane microsphere composite is used as the toughening agent.

[0051] Comparative Example 3 A method for preparing an epoxy resin composite coating is carried out according to the method in Example 1, except that an equal amount of modified nano-silica in the toughening agent is replaced by nano-silica.

[0052] Performance testing The component A and component B prepared in the examples and comparative examples of the present application were mixed in a mass ratio of 100:20 to prepare a composite coating for application. The mixed composite coating was subjected to impact resistance tests at room temperature of 25°C and low temperature of -10°C, respectively, with reference to the method of HG / T 4759-2014. The statistical results are shown in Table 1 below. In addition, the abrasion resistance was tested with reference to GB / T 22374-2018 (test conditions: 1000g / 800r); the paint film hardness was measured by the pencil method with reference to GB / T 6739-2022, and the test results are shown in Table 1 below.

[0053] Table 1: Continued Table 1: Referring to the test results in Table 1 above, the epoxy resin composite coating prepared in the embodiment of the present application has excellent impact resistance and also has good wear resistance and hardness, taking into account impact resistance and rigidity. Combined with the test results of Example 1 and Examples 4-6, when preparing the modified nano-silica, when polyethylene glycol monomethyl ether is added after a period of in-situ polymerization, the introduction of its ether bond further improves its impact resistance, especially low-temperature impact resistance. Combined with the test results of Example 7, when an acrylate layer is formed on the nano-silica, when the nano-silica is directly added to the monomer mixture for emulsion polymerization, its impact resistance is reduced compared to Example 1, especially the low-temperature performance, and its wear resistance is also reduced. After introducing vinyl into the surface of the nano-silica and then reacting with the monomer mixture to achieve in-situ polymerization, the final coating has better impact resistance.

[0054] Combined with the test results of Example 1 and Comparative Example 1, it can be seen that when the modified nano-silica is prepared and the acrylate is polymerized on the silica without a silane layer, its impact resistance is significantly reduced, and its hardness and wear resistance are reduced. The organic silane layer helps to improve the interface bonding between the modified nano-silica and the epoxy resin, and forms additional cross-linking points to improve its hardness and wear resistance; combined with the test results of Comparative Example 2, when the toughening agent is only selected from the nano-montmorillonite-polyurethane microsphere composite, its impact resistance is significantly reduced, and its hardness is also low. Combined with the test results of Comparative Example 3, the performance of the nano-silica is also significantly reduced when it is directly added. After modification, it is significantly improved for the performance of the coating when combined with the nano-montmorillonite-polyurethane microsphere composite.

[0055] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. An epoxy resin composite coating, characterized in that: It includes component A and component B. Component A includes the following raw materials in parts by weight: 60-75 parts of hydrogenated bisphenol A epoxy resin, 15-25 parts of solvent, 20-30 parts of filler, 0.2-0.5 parts of defoamer, 0.3-0.8 parts of leveling agent, 0.5-1 parts of dispersant and 5-10 parts of toughening agent; Component B includes the following raw materials in parts by weight: 45-55 parts of curing agent and 5-10 parts of diluent; Among them, the toughening agent in component A includes a nano-montmorillonite-polyurethane microsphere composite and modified nano-silica in a mass ratio of 1: (1.3-1.5). The modified nano-silica is made of nano-silica as the core material, an acrylate layer as the inner core layer and a silicone layer as the outer shell layer.

2. The epoxy resin composite coating according to claim 1, wherein: The nano-montmorillonite-polyurethane microsphere composite was prepared by the following method: The nano-montmorillonite is mixed with water and hydroxyethyl cellulose to prepare a suspension, and then a polyurethane prepolymer is added thereto. The suspension is ultrasonically treated for 20-30 minutes, allowed to stand for 20-24 hours, and filtered to obtain a nano-montmorillonite-polyurethane microsphere composite.

3. The epoxy resin composite coating according to claim 2, characterized in that: When preparing the nano-montmorillonite-polyurethane microsphere composite, the mass ratio of nano-montmorillonite to water is 1: (2-3), the amount of hydroxyethyl cellulose added is 5-8wt% of the nano-montmorillonite, and the mass ratio of polyurethane prepolymer to nano-montmorillonite is 1: (1.8-2.2).

4. The epoxy resin composite coating according to claim 1, wherein: The modified nano-silica is prepared by the following method: 1) Mix vinyltrimethoxysilane with water and ethanol, then add hydroxyethyl cellulose and nano-silica, adjust the pH to 4-5.5, heat to 50-60°C, stir for 60-90 minutes, filter and dry to obtain primary modified nano-silica; 2) Mix methyl methacrylate, hydroxyethyl acrylate and acrylic acid to prepare a monomer mixture, mix alkylphenol polyoxyethylene ether and water, then add primary modified nano-silica, heat to 60-70°C, add the monomer mixture and initiator, and then keep the temperature to react for 2-3 hours to form a primary emulsion with nano-silica as the core material and acrylate as the inner core layer; 3) Cool the primary emulsion to 30-40°C, then add vinyltrimethoxysilane and adjust the pH to 7.5-8.5 by adding ammonia water. After reacting for 3-4 hours, filter, wash with alcohol and dry to obtain modified nano-silica.

5. The epoxy resin composite coating according to claim 4, characterized in that: When preparing the modified nano-silica, the mass ratio of vinyltrimethoxysilane to water and ethanol in step 1) is 1:(3-4):(2-3), the amount of hydroxyethyl cellulose added is 3-5wt% of the vinyltrimethoxysilane, and the amount of nano-silica added is 4-6 times the mass of the vinyltrimethoxysilane; In step 2), the addition mass ratio of methyl methacrylate, hydroxyethyl acrylate and acrylic acid is 1: (0.6-0.8): (0.5-0.8), the addition mass ratio of alkylphenol polyoxyethylene ether and water is 1: (12-15), and the addition amount of alkylphenol polyoxyethylene ether is 0.3-0.5wt% of the primary modified nano-silica, the addition mass ratio of primary modified nano-silica to the monomer mixture is 1: (0.8-1), and the addition amount of initiator is 0.5-1wt% of the monomer mixture; In step 3), the amount of vinyltrimethoxysilane added is 8-10% of the initial nano-silica.

6. The epoxy resin composite coating according to claim 4, characterized in that: During the preparation of modified nano-silica, in step 2), after adding the monomer mixture and the initiator and keeping the reaction warm for 1-2 hours, polyethylene glycol monomethyl ether is added, and the amount of polyethylene glycol monomethyl ether added is 3-5wt% of the initial modified nano-silica, and then the reaction is continued to form a primary emulsion.

7. The epoxy resin composite coating according to claim 1, characterized in that: In component A, the defoamer is a silicone defoamer, the leveling agent is an acrylic leveling agent, the filler is nano-silica or carbon black, and the solvent is a mixture of xylene and butyl glycidyl ether in a mass ratio of 1: (0.2-0.3).

8. The epoxy resin composite coating according to claim 1, characterized in that: The curing agent in component B is a polyamide curing agent and a polyetheramine curing agent in a mass ratio of 1: (0.3-0.4); the diluent is a mixture of xylene and butyl glycidyl ether in a mass ratio of 1: (0.2-0.3).

9. The epoxy resin composite coating according to claim 1, characterized in that: The component B further comprises 0.5-1 parts by weight of triethanolamine.

10. The method for preparing an epoxy resin composite coating according to any one of claims 1 to 9, wherein: The following steps are involved: Preparation of component A: Mix hydrogenated bisphenol A epoxy resin with a solvent, add the remaining raw materials of component A, and mix to prepare component A; Preparation of component B: Mix the curing agent and the diluent to prepare component B.

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