A waterborne epoxy emulsion, its preparation method and application

Abstract

This invention belongs to the field of coating technology, specifically relating to a waterborne epoxy emulsion, its preparation method, and its application. The invention involves mixing a first epoxy resin, an organic alcohol polymer, and a ring-opening addition reaction catalyst, and conducting a ring-opening addition reaction under a protective atmosphere to obtain a waterborne epoxy emulsifier. The waterborne epoxy emulsifier, water, a second epoxy resin, and an active epoxy diluent are then mixed and defoamed to obtain the waterborne epoxy emulsion. This waterborne epoxy emulsion exhibits low viscosity, good leveling properties, and good stability.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, specifically relating to an aqueous epoxy emulsion, its preparation method, and its application. Background Technology

[0002] Epoxy resin molecules possess polar groups such as epoxy end groups, hydroxyl groups, and ether bonds. These groups enable epoxy resin molecules to form electromagnetic adsorption or chemical bonds with adjacent interfaces, resulting in strong adhesion between epoxy resin coatings and substrates such as metal, wood, and concrete. Epoxy resins exhibit excellent properties in terms of crosslinking density, electrical insulation, and chemical resistance, and are widely used as protective coatings, including but not limited to applications in aerospace, anti-corrosion coatings, building materials, and industrial floor coatings.

[0003] However, traditionally used epoxy resins, such as liquid bisphenol A epoxy resin E-51, have a viscosity of 12,000–15,000 mPa·s at room temperature, and bisphenol A epoxy acrylate YC3381S is nearly solid at room temperature. Therefore, they cannot be used directly and require large amounts of ketones, esters, and cycloalkane solvents to dissolve them. This results in high levels of volatile organic compounds (VOCs), which are extremely harmful to the environment and human health, limiting their application and development. Therefore, developing environmentally friendly waterborne epoxy emulsions to replace solvent-based epoxy emulsions is imperative.

[0004] Waterborne epoxy emulsions have seen rapid market demand growth due to their environmental friendliness and low VOC content, but they still face many challenges in performance improvement. Viscosity, leveling, and stability are key performance indicators for waterborne epoxy emulsions, significantly impacting their application properties, coating quality, and durability. Currently, commercially available waterborne epoxy emulsions suffer from poor storage stability, excessively high viscosity, and poor leveling. Related technologies utilize emulsifiers with hydrophilic segments such as phytic acid, polyetheramine, and polyethylene glycol diglycidyl ether, which result in poor emulsification of epoxy resins in the later stages, leading to high emulsion viscosity. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide an aqueous epoxy emulsion, its preparation method and application, wherein the aqueous epoxy emulsion has low viscosity, good leveling properties and good stability.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing an aqueous epoxy emulsion, comprising the following steps:

[0008] The first epoxy resin, organic alcohol polymer and ring-opening addition reaction catalyst are mixed and the ring-opening addition reaction is carried out in a protective atmosphere to obtain an aqueous epoxy emulsifier.

[0009] The aqueous epoxy emulsifier, water, second epoxy resin and active epoxy diluent are mixed and defoamed to obtain an aqueous epoxy emulsion.

[0010] Preferably, the first epoxy resin and the second epoxy resin are independently glycidyl ether epoxy resins; the organic alcohol polymer is a hydroxyl-terminated organic alcohol polymer; the hydroxyl-terminated organic alcohol polymer includes one or more of polyethylene glycol, polyethylene glycol derivatives, polyvinyl alcohol, polypropylene glycol, PEG block copolymers, polyoxyalkylene glycol, and polyoxyethylene glycol-oxypropylene glycol.

[0011] Preferably, the molar ratio of epoxy groups in the first epoxy resin to hydroxyl groups in the organic alcohol polymer is (1-2):1.

[0012] Preferably, the ring-opening addition reaction catalyst is one or more of boron trifluoride diethyl ether, tetrabutylammonium bromide, hexadecyltrimethylammonium bromide, triethanolamine, and potassium persulfate.

[0013] Preferably, the ring-opening addition reaction is carried out at a temperature of 70–110°C and for a duration of 2–8 hours.

[0014] Preferably, the active epoxy diluent comprises one or more of ethylene glycol diglycidyl ether, butylene glycol diglycidyl ether, hexanediol diglycidyl ether, octyl glycol diglycidyl ether, and γ-glycidyl etheroxypropyltrimethoxysilane.

[0015] Preferably, the mass ratio of the waterborne epoxy emulsifier to water is (5-25):100; and the mass ratio of water to the second epoxy resin is (8-14):10.

[0016] Preferably, the mass ratio of the reactive epoxy diluent to the second epoxy resin is (1-5):10.

[0017] The present invention also provides an aqueous epoxy emulsion prepared by the preparation method described in the above technical solution.

[0018] The present invention also provides the application of the waterborne epoxy emulsion described in the above technical solution in coatings.

[0019] This invention provides a method for preparing an aqueous epoxy emulsion, comprising the following steps: mixing a first epoxy resin, an organic alcohol polymer, and a ring-opening addition reaction catalyst, and carrying out a ring-opening addition reaction in a protective gas to obtain an aqueous epoxy emulsifier; mixing the aqueous epoxy emulsifier, water, a second epoxy resin, and an active epoxy diluent, and then degassing to obtain an aqueous epoxy emulsion.

[0020] This invention adds a first epoxy resin to improve the oleophilicity of the waterborne epoxy emulsifier, making it highly compatible with the emulsion system. Adding an organic alcohol polymer reduces the viscosity of the first epoxy resin and makes the waterborne epoxy emulsifier hydrophilic, thus enabling the first epoxy resin to better compatibility with the waterborne system. This allows the waterborne epoxy emulsifier to more effectively encapsulate the droplets of the waterborne epoxy emulsion, reducing the interaction between droplets, lowering the viscosity of the waterborne epoxy emulsion, and forming a stable interfacial film at the oil-water interface, reducing the interfacial tension and improving the stability and leveling properties of the emulsion. Adding a ring-opening addition reaction catalyst lowers the activation energy of the reaction, accelerates the reaction rate, increases the degree of reaction, and makes the structure of the waterborne epoxy emulsifier uniform and its performance stable, further improving the emulsification effect and enhancing the stability of the waterborne epoxy emulsion. Adding an active epoxy diluent reduces the viscosity of the epoxy resin, lowers the surface tension, optimizes the emulsification process, and makes the epoxy resin easier to disperse into fine droplets by the waterborne epoxy emulsifier, forming a stable emulsion. The results of the examples show that the waterborne epoxy emulsion prepared by the present invention has low viscosity, good leveling properties, and good stability. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the preparation method of the aqueous epoxy emulsion in an embodiment of the present invention;

[0022] Figure 2 The infrared spectrum of the aqueous epoxy emulsifier prepared in Example 1. Detailed Implementation

[0023] This invention provides a method for preparing an aqueous epoxy emulsion, comprising the following steps:

[0024] The first epoxy resin, organic alcohol polymer and ring-opening addition reaction catalyst are mixed and the ring-opening addition reaction is carried out in a protective atmosphere to obtain an aqueous epoxy emulsifier.

[0025] The aqueous epoxy emulsifier, water, second epoxy resin and active epoxy diluent are mixed and defoamed to obtain an aqueous epoxy emulsion.

[0026] Unless otherwise specified, the present invention does not have special requirements on the source of raw materials used, and commercially available products well known to those skilled in the art can be used.

[0027] The present invention mixes a first epoxy resin, an organic alcohol polymer and a ring-opening addition reaction catalyst, and carries out a ring-opening addition reaction in a protective gas to obtain an aqueous epoxy emulsifier.

[0028] In one embodiment, the first epoxy resin is a glycidyl ether epoxy resin; the glycidyl ether epoxy resin includes glycidyl ether epoxy resin E44 and / or glycidyl ether epoxy resin E51, with E51 being a specific embodiment; the epoxy value of the first epoxy resin is 0.41–0.54 mol / 100g, with 0.48–0.54 mol / 100g being a specific embodiment. The epoxy resin used in this invention has a similar epoxy value and surface tension to the aqueous epoxy emulsion system, which helps to improve the compatibility between the emulsifier and the aqueous epoxy emulsion system and enhance the emulsification effect. The epoxy value of the epoxy resin affects the mechanical strength and thermal stability after the emulsion is cured.

[0029] In one embodiment, the organic alcohol polymer is a hydroxyl-terminated organic alcohol polymer; the hydroxyl-terminated organic alcohol polymer includes one or more of polyethylene glycol, polyethylene glycol derivatives, polyvinyl alcohol, polypropylene glycol, PEG block copolymers, polyoxyalkylene glycols, and polyoxyethylene glycol-oxypropylene glycol, with polyethylene glycol being used in a specific embodiment; the polyethylene glycol includes one or more of polyethylene glycol 2000, polyethylene glycol 4000, polyethylene glycol 6000, polyethylene glycol 8000, and polyethylene glycol 10000, with polyethylene glycol 6000 or polyethylene glycol 8000 being used in a specific embodiment; the weight-average molecular weight of the organic alcohol polymer is 2000-10000, with 4000-8000 being used in a specific embodiment; the hydroxyl content in the organic alcohol polymer is 12-63 mgKOH / g, with 20-50 mgKOH / g being used in a specific embodiment. The hydroxyl content in the organic alcohol polymer affects the hydrophilicity of the prepared emulsifier. The organic alcohol polymer used in this invention can reduce the viscosity of epoxy resin and give the waterborne epoxy emulsifier a certain degree of hydrophilicity, thereby enabling the epoxy resin to be better compatible with the waterborne system.

[0030] In one embodiment, the mass ratio of the first epoxy resin to the organic alcohol polymer is 1:(2.5-12.5), and in another embodiment, it is 1:(5-10). In specific embodiments of the present invention, the mass ratio of the first epoxy resin to the organic alcohol polymer is 1:2.5, 1:5, 1:7.5, 1:10, or 1:12.5; the molar ratio of the epoxy groups in the first epoxy resin to the hydroxyl groups in the organic alcohol polymer is (1-2):1, and in specific embodiments, it is 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, or 2:1. The present invention modifies the epoxy resin with an organic alcohol polymer, grafting hydrophilic hydroxyl groups onto the inherently lipophilic epoxy resin. By controlling the ratio of epoxy resin to organic alcohol polymer, the resulting waterborne epoxy emulsifier possesses both lipophilic and hydrophilic properties, thereby further improving the stability of the waterborne epoxy emulsion.

[0031] In one embodiment, the ring-opening addition reaction catalyst is one or more of boron trifluoride diethyl ether, tetrabutylammonium bromide, hexadecyltrimethylammonium bromide, triethanolamine, and potassium persulfate, with boron trifluoride diethyl ether being a specific example.

[0032] In one embodiment, the mass ratio of the ring-opening addition reaction catalyst to the first epoxy resin is (1-4):100, and in specific embodiments it is 1:100, 2:100, 3:100 or 4:100.

[0033] Different types of catalysts for ring-opening addition reactions require different reaction temperatures and times, resulting in varying degrees of reaction. This invention reduces the activation energy of the reaction by limiting the type of catalyst and the mass ratio of the catalyst to epoxy resin, thereby accelerating the reaction rate, shortening the reaction time, and increasing the degree of reaction. This results in a waterborne epoxy emulsifier with a uniform structure and stable performance, further improving the emulsification effect and enhancing the stability of the waterborne epoxy emulsion. This avoids the problems of insufficient reaction degree and inadequate catalytic effect due to insufficient catalyst dosage, while also preventing gelation due to excessive catalyst dosage.

[0034] In one embodiment, the first epoxy resin, polyethylene glycol, and ring-opening addition catalyst are mixed as follows: after removing water from the mixture of the first epoxy resin and polyethylene glycol, the ring-opening addition catalyst is finally added; the first epoxy resin and polyethylene glycol are mixed under heating and stirring conditions; the heating temperature is 60-90°C, specifically 60°C, 70°C, 80°C, or 90°C in this embodiment; the stirring rate is 200-400 rpm, or 250-350 rpm in another embodiment; in this embodiment, the stirring rate is 200 rpm, 250 rpm, 300 rpm, 350 rpm, or 400 rpm; the mixing time of the first epoxy resin and polyethylene glycol is 0.5-1 h, specifically 0.5 h or 1 h in this embodiment.

[0035] In one implementation, the water removal is performed by vacuum dewatering; the dewatering temperature is 60–90°C, specifically 60°C, 70°C, 80°C, or 90°C in this embodiment; the dewatering time is 20–120 minutes, specifically 20 minutes, 40 minutes, 60 minutes, 80 minutes, 100 minutes, or 120 minutes in this embodiment. This invention ensures thorough water removal by limiting the dewatering temperature and time.

[0036] In one embodiment, the catalyst for the ring-opening addition reaction is added dropwise; the dropwise addition rate is 0.01 to 0.08 mL / min, and in specific embodiments, it is 0.01 mL / min, 0.02 mL / min, 0.03 mL / min, 0.04 mL / min, 0.05 mL / min, 0.06 mL / min, 0.07 mL / min, or 0.08 mL / min.

[0037] This invention, by limiting the dropping rate of the catalyst for the ring-opening addition reaction, can ensure that the ring-opening addition reaction proceeds more fully and enhance the controllability of the reaction, avoiding the burst polymerization phenomenon caused by excessively fast dropping rate. Burst polymerization will cause the product to gel, which is not conducive to use.

[0038] In one embodiment, the protective gas is nitrogen.

[0039] In one implementation, the temperature of the ring-opening addition reaction is 70–110°C, specifically 70°C, 80°C, 90°C, 100°C, or 110°C in specific embodiments; the time of the ring-opening addition reaction is 2–8 hours, specifically 2 hours, 3 hours, 4 hours, 5 hours, or 6 hours in specific embodiments. This invention ensures a more complete ring-opening addition reaction by limiting the temperature and time of the reaction.

[0040] In one embodiment, the ring-opening addition reaction is carried out under stirring conditions; the stirring rate is 200-400 rpm, and in another embodiment it is 250-350 rpm; in a specific embodiment, the stirring rate is 200 rpm, 250 rpm, 300 rpm, 350 rpm or 400 rpm.

[0041] In this invention, a ring-opening addition reaction occurs between the epoxy groups and hydroxyl groups of the epoxy resin, forming an ether bond and releasing water molecules. The specific reaction formula is as follows:

[0042]

[0043] This invention improves the oleophilicity of the waterborne epoxy emulsifier by adding a first epoxy resin, enabling the emulsifier to be compatible with the waterborne epoxy emulsion system. It also reduces the viscosity of the first epoxy resin and imparts a certain degree of hydrophilicity to the waterborne epoxy emulsifier by adding an organic alcohol polymer, thus further enhancing its compatibility with the waterborne system. The waterborne epoxy emulsifier prepared by this invention can more effectively encapsulate droplets, reducing interactions between droplets and lowering the viscosity of the waterborne epoxy emulsion. Furthermore, when the oil phase is added to the aqueous phase, the waterborne epoxy emulsifier can rapidly form a stable interfacial film at the oil-water interface, reducing interfacial tension and improving emulsion stability. This also prevents stratification or precipitation during storage, extending the emulsion's service life.

[0044] The epoxy resin and organic alcohol polymer used in this invention are simple, readily available and inexpensive raw materials. The synthesis method is simple and reproducible, the reaction conditions are controllable, the synthesized emulsifier has a simple structure, the reaction is easy to control, and the emulsifier has a good effect, thereby resulting in low viscosity and good stability of the waterborne epoxy emulsion prepared subsequently.

[0045] After obtaining the waterborne epoxy emulsifier, the present invention mixes the waterborne epoxy emulsifier, water, second epoxy resin and active epoxy diluent, and then degassing to obtain a waterborne epoxy emulsion.

[0046] In one embodiment, the water is deionized water; the mass ratio of the waterborne epoxy emulsifier to water is (5-25):100, and in specific embodiments it is 5:100, 10:100, 15:100, 20:100 or 25:100.

[0047] Waterborne epoxy emulsifiers can reduce the interfacial tension between oil and water, enabling epoxy resin to form a stable dispersed phase in water. In this invention, the mass ratio of waterborne epoxy emulsifier to water ensures that the waterborne epoxy emulsifier forms a uniform adsorption layer at the oil-water interface, thereby effectively reducing the interfacial tension, promoting the emulsification process, ensuring the emulsifying effect of the emulsifier, reducing emulsion particle size, and enhancing emulsion stability.

[0048] In one embodiment, the second epoxy resin is a glycidyl ether epoxy resin; the glycidyl ether epoxy resin includes glycidyl ether epoxy resin E44 and / or glycidyl ether epoxy resin E51, with E51 being used in a specific embodiment; the epoxy value of the second epoxy resin is 0.41–0.54 mol / 100g, with 0.48–0.54 mol / 100g being used in a specific embodiment. In this invention, the second epoxy resin has a similar epoxy value and surface tension to the first epoxy resin used in the waterborne epoxy emulsifier, which improves the compatibility between the waterborne epoxy emulsifier and the waterborne epoxy emulsion system, and enhances the stability of the emulsion.

[0049] In one embodiment, the reactive epoxy diluent includes one or more of ethylene glycol diglycidyl ether, butanediol diglycidyl ether, hexanediol diglycidyl ether, octanediol diglycidyl ether, and γ-glycidyl etheroxypropyltrimethoxysilane, with hexanediol diglycidyl ether and γ-glycidyl etheroxypropyltrimethoxysilane being used in specific embodiments. The reactive epoxy diluent used in this invention can reduce the viscosity and surface tension of the emulsion system, improve fluidity and dispersibility, optimize the emulsification process, and make it easier for the epoxy resin to be dispersed into fine droplets by the emulsifier, forming an emulsion with a uniform particle size distribution, thereby contributing to improved stability and resulting in an emulsion with low viscosity and good leveling properties.

[0050] In one embodiment, the mass ratio of the reactive epoxy diluent to the second epoxy resin is (1-5):10, and in specific embodiments it is 1:10, 2:10, 3:10, 4:10 or 5:10.

[0051] Before emulsification, the viscosity of the epoxy resin system needs to be moderate to facilitate the subsequent emulsification process. Excessive viscosity leads to emulsification difficulties and uneven particle size distribution in the emulsion; excessively low viscosity may affect the stability of the emulsion. Therefore, this invention utilizes the low viscosity of an active epoxy diluent to dilute the high-viscosity component in the epoxy resin, improving the system's flowability and ensuring a suitable viscosity to meet the requirements of the emulsification process. This invention further reduces the viscosity of the second epoxy resin by limiting the mass ratio of the active epoxy diluent to the second epoxy resin to ensure appropriate viscosity before emulsification, thereby reducing the surface tension and optimizing the emulsification process. This makes it easier for the second epoxy resin to be dispersed into fine droplets by the emulsifier, forming a stable emulsion with better leveling properties.

[0052] In one embodiment, the mass ratio of water to the second epoxy resin is (8-14):10, specifically 8:10, 9:10, 10:10, 11:10, 12:10, 13:10, or 14:10. Within the mass ratio range of water to the second epoxy resin provided by this invention, water, as the continuous phase, can dilute the epoxy resin, dispersing it into fine emulsion particles, reducing the overall viscosity of the emulsion, and helping to form emulsion particles with uniform particle size distribution. This reduces particle collisions and aggregation, thereby improving the stability of the emulsion. It avoids both excessively high emulsion viscosity and poor leveling properties due to low water content, and low emulsion viscosity and poor stability due to high water content. This invention ensures that the emulsion system has good viscosity, leveling properties, and stability by limiting the mass ratio of water to the second epoxy resin.

[0053] In one implementation, the mixing time is 1 to 6 hours, and in a specific embodiment it is 4 to 6 hours.

[0054] In one embodiment, the aqueous epoxy emulsifier, water, second epoxy resin, and reactive epoxy diluent are mixed as follows: the aqueous epoxy emulsifier and water are first mixed to obtain an aqueous phase; the second epoxy resin and reactive epoxy diluent are second mixed to obtain an oil phase; and the oil phase is dropwise added to the aqueous phase for a third mixing.

[0055] This invention employs a method of adding an oil phase dropwise to an aqueous phase, with the aqueous phase serving as the continuous phase and the oil phase as the dispersed phase, dispersed into fine droplets. Due to the increased surface area of ​​the dispersed phase droplets, the emulsifier can more effectively encapsulate the droplets, reducing interactions between them and thus lowering the viscosity of the aqueous epoxy emulsion. Furthermore, when the oil phase is added to the aqueous phase, the emulsifier can rapidly form a stable interfacial film at the oil-water interface, reducing interfacial tension and thereby improving the emulsion's stability. This also prevents stratification or precipitation during storage, extending the emulsion's service life.

[0056] In one embodiment, the temperature of the first mixing is 30–40°C, specifically 30°C or 40°C in a specific embodiment; the first mixing is carried out under stirring conditions; the stirring rate is 100–300 rpm, or 150–250 rpm in another embodiment; in a specific embodiment, the stirring rate is 100 rpm, 150 rpm, 200 rpm, 250 rpm, or 300 rpm. In one embodiment, the time for the first mixing is 0.5–1 hour, specifically 0.5 hours or 1 hour in a specific embodiment.

[0057] In one embodiment, the temperature of the second mixing is 30–50°C, specifically 30°C, 40°C, or 50°C in some embodiments; the second mixing is carried out under stirring conditions; the stirring rate is 100–300 rpm, or 150–250 rpm in another embodiment; in a specific embodiment, the stirring rate is 100 rpm, 150 rpm, 200 rpm, 250 rpm, or 300 rpm. In one embodiment, the time for the second mixing is 0.5–1 hour, specifically 0.5 hours or 1 hour in some embodiments.

[0058] In one implementation, the dropping rate is 1–8 mL / min, specifically 1 mL / min, 2 mL / min, 3 mL / min, 4 mL / min, 5 mL / min, 6 mL / min, 7 mL / min, or 8 mL / min in specific embodiments. This invention ensures more thorough third-stage mixing by limiting the dropping rate.

[0059] In one embodiment, the temperature of the third mixing is 30–40°C, specifically 30°C or 40°C in a specific embodiment; the third mixing is carried out under stirring conditions; the stirring rate is 500–700 rpm, or 550–650 rpm in another embodiment; in a specific embodiment, the stirring rate is 500 rpm, 550 rpm, 600 rpm, 650 rpm, or 700 rpm. In one embodiment, the time for the third mixing is 3–4 hours, specifically 3 hours or 4 hours in a specific embodiment.

[0060] In one implementation, the degassing equipment is a planetary mixer; the degassing time is 1-2 minutes, specifically 1 minute or 2 minutes in this embodiment; the degassing speed is 1500-2000 rpm, specifically 1500 rpm, 1600 rpm, 1700 rpm, 1800 rpm, 1900 rpm, or 2000 rpm in this embodiment. This invention removes air bubbles from the product by limiting the degassing time and speed, ensuring product quality and performance, and further improving the stability of waterborne epoxy emulsions.

[0061] Figure 1 This is a schematic diagram of the preparation method of the aqueous epoxy emulsion in an embodiment of the present invention. Figure 1 As shown, the present invention involves mixing epoxy resin and polyethylene glycol, removing water, and then adding a catalyst dropwise to the resulting mixture to synthesize an aqueous epoxy emulsifier. The aqueous epoxy emulsifier is then mixed with water to obtain an aqueous phase. An oil phase obtained by mixing epoxy resin and an active epoxy diluent is dropwise added to the aqueous phase for mixing and degassing to obtain an aqueous epoxy emulsion.

[0062] This invention adds epoxy resin to improve the lipophilicity of waterborne epoxy emulsifiers, enabling the emulsifiers to be compatible with waterborne epoxy emulsion systems. By adding polyethylene glycol, the viscosity of the epoxy resin is reduced, and the waterborne epoxy emulsifier acquires a certain degree of hydrophilicity, thus allowing the epoxy resin to better compatibility with waterborne systems. By adding a catalyst, the activation energy of the reaction is lowered, the reaction rate is accelerated, and the degree of reaction is increased, resulting in a more uniform emulsifier structure and more stable performance, further improving the emulsification effect and enhancing the stability of waterborne epoxy emulsions. Furthermore, this invention adds a water-based epoxy emulsifier, which can be adsorbed onto the surface of the water-based epoxy emulsion droplets to form a protective film, preventing the droplets from agglomerating and merging. This protective effect reduces disordered collisions of droplets, making the droplet size distribution more uniform and narrower, thus obtaining a water-based epoxy emulsion with a narrow particle size distribution and good stability. By adding an active epoxy diluent, the viscosity of the epoxy resin is reduced, the surface tension is lowered, and the emulsification process is optimized, making it easier for the epoxy resin to be dispersed into fine droplets by the emulsifier to form a stable emulsion, resulting in better leveling properties of the prepared emulsion.

[0063] The present invention also provides an aqueous epoxy emulsion prepared by the preparation method described in the above technical solution.

[0064] In one embodiment, the viscosity of the aqueous epoxy emulsion is 30–550 mPa·s, specifically 34 mPa·s, 96 mPa·s, 230 mPa·s, 533 mPa·s, 50 mPa·s, 38 mPa·s, 57 mPa·s, or 62 mPa·s; the leveling property is 6–9, specifically 6, 8, or 9; and the stability is 1–4, specifically 1, 2, or 4. The average particle size of the aqueous epoxy emulsion is 500–30000 nm, specifically 26731 nm, 2527 nm, 998 nm, 852 nm, 7171 nm, 7605 nm, 3944 nm, 5044 nm, or 5711 nm.

[0065] The aqueous epoxy emulsion prepared by this invention has low viscosity, good leveling properties, and good stability.

[0066] The present invention also provides the application of the waterborne epoxy emulsion described in the above technical solution in coatings.

[0067] This invention does not have any particular limitation on the application field of the coating, and it can be used in aerospace, anti-corrosion coating, building materials, industrial floor coating, etc.

[0068] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0069] Example 1

[0070] (1) Add 4g of glycidyl ether epoxy resin E51 and 6000g of hydroxyl-terminated polyethylene glycol. 30g was placed in a 90℃ oil bath and mixed for 0.5h under stirring at 300rpm; the mixture was then cooled to 70℃ and vacuum-dried for 1h; then 0.08g of boron trifluoride diethyl ether, a ring-opening addition catalyst, was added dropwise to the reactor at a rate of 0.02mL / min using a constant flow pump. The ring-opening addition reaction was carried out for 4h under a nitrogen atmosphere at 90℃ and stirring at 300rpm to obtain an aqueous epoxy emulsifier; the mass ratio of glycidyl ether epoxy resin E51 to hydroxyl-terminated polyethylene glycol 6000 was 1:7.5, the epoxy value of glycidyl ether epoxy resin E51 was 0.51mol / 100g, and the molar ratio of epoxy groups in glycidyl ether epoxy resin E51 to hydroxyl groups in hydroxyl-terminated polyethylene glycol 6000 was 2:1; the mass ratio of boron trifluoride diethyl ether, a ring-opening addition catalyst, to glycidyl ether epoxy resin E51 was 2:100.

[0071] (2) Mix 0.5g of the aqueous epoxy emulsifier and 10g of deionized water obtained in step (1) at 30℃ and 150rpm for 0.5h to obtain the aqueous phase; add glycidyl ether epoxy resin E51 10g of hexanediol diglycidyl ether (an active epoxy diluent), 2g of γ-glycidyl etheroxypropyltrimethoxysilane (an active epoxy diluent), and 1g of glycidyl etheroxypropyltrimethoxysilane were mixed at 40℃ and 200rpm for 0.5h to obtain an oil phase. The oil phase was then added dropwise to the aqueous phase at a rate of 1mL / min using a constant flow pump. The mixture was stirred at 30℃ and 600rpm for 3h, and then degassed at 1500rpm in a planetary mixer for 1min to obtain an aqueous epoxy emulsion. The mass ratio of the aqueous epoxy emulsifier to water was 5:100, the mass ratio of the active epoxy diluent to glycidyl ether epoxy resin was 3:10, and the mass ratio of water to glycidyl ether epoxy resin was 1:1.

[0072] Example 2

[0073] The difference between this embodiment and embodiment 1 is that 0.5g of waterborne epoxy emulsifier in step (2) is replaced with 1.0g, and the rest is the same as in embodiment 1.

[0074] Example 3

[0075] The difference between this embodiment and embodiment 1 is that 0.5g of waterborne epoxy emulsifier in step (2) is replaced with 1.5g, and the rest is the same as in embodiment 1.

[0076] Example 4

[0077] The difference between this embodiment and embodiment 1 is that 0.5g of waterborne epoxy emulsifier in step (2) is replaced with 2.0g, and the rest is the same as in embodiment 1.

[0078] Examples 5-9

[0079] The difference from Example 2 is that the molar ratios of epoxy groups in glycidyl ether epoxy resin E51 to hydroxyl groups in hydroxyl-terminated polyethylene glycol 6000 are 1:1, 1.2:1, 1.4:1, 1.6:1, and 1.8:1, respectively, while the rest are the same as in Example 2.

[0080] Comparative Example 1

[0081] Commercially available water-based epoxy emulsion DY-128.

[0082] Performance testing

[0083] (1) The present invention conducts viscosity tests, leveling tests and stability tests on the waterborne epoxy emulsions prepared in Examples 1 to 9 and the commercially available waterborne epoxy emulsion DY-128. The viscosity test was conducted according to the standard GB / T 2794-2013, "Determination of Viscosity of Adhesives - Single-Cylinder Rotational Viscometer Method," at a test temperature of 25℃ for 2 minutes. The leveling property test was conducted according to the standard ASTM D2801, "Test Method for Determining the Leveling Properties of Coatings - Pull-Down Method," classifying leveling properties into 0 to 10 levels, with 0 being the worst and 10 the best. The stability test was conducted according to the standard GB / T 11543-2008, "Test Method for the Characteristics of Medium and High Viscosity Emulsions of Surfactants and Evaluation Method for Their Emulsifying Ability," placing the emulsion at a constant temperature of 40℃ for 72 hours and observing the phenomena observed. The stability was classified into 1 to 6 levels, with 1 being good uniformity and 6 being complete phase separation. The particle size test involved observing the morphology of the emulsion droplets using an optical microscope. The prepared emulsion was lightly spread onto a glass slide, covered with a coverslip (20×20mm), and the sample was placed on the microscope stage. The objective lens was adjusted, and the droplet morphology was observed and photographed. Subsequently, using the accompanying Capture 2.4 software, 100 droplets were randomly selected to statistically analyze the diameter distribution of the emulsion droplets, and the droplet diameter was determined using the three-point circle determination method. The results are shown in Table 1.

[0084] Table 1 Performance Evaluation of Waterborne Epoxy Emulsions

[0085]

[0086]

[0087] As shown in Table 1, the waterborne epoxy emulsion prepared in Example 1 has the lowest viscosity and the best leveling properties, but its stability is slightly inferior. Examples 2 and 3 both have relatively low viscosity, with Example 3 showing better stability. Example 4 exhibits the best stability, but its viscosity is slightly higher, which is due to the amount of waterborne epoxy emulsifier used. Comparative Example 1 has the worst stability and poor leveling properties.

[0088] The above tests show that the waterborne epoxy emulsion prepared by this invention has low viscosity, good leveling properties, and good stability.

[0089] (2) Figure 2 The infrared spectrum of the aqueous epoxy emulsifier prepared in Example 1.

[0090] Depend on Figure 2 It can be known that 3460cm -1 The peak at 2880 cm⁻¹ is the characteristic absorption peak of the hydroxyl group (-OH) in the emulsifier molecule. -1 The peak at 1620 cm⁻¹ represents the stretching vibration peak of the methylene-CH₂- group in the polyethylene glycol chain; -1 and 1470cm -1The peak at 1120 cm⁻¹ represents the vibrational absorption peak of the six-membered ring skeleton on the benzene ring in the epoxy resin chain segment. -1 The peak at 840 cm⁻¹ represents the stretching vibration of the ether bond -CO-. -1 This is a characteristic peak of para-substitution of the benzene ring. As can be seen from the infrared spectrum, this peak is at 915 cm⁻¹. -1 The absence of characteristic absorption peaks for epoxy groups indicates that the epoxy resin underwent a ring-opening addition reaction with polyethylene glycol, consuming the epoxy groups.

[0091] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing an aqueous epoxy emulsion, characterized in that, The steps are as follows: (1) Add 4g of glycidyl ether epoxy resin E51 and 6000g of hydroxyl-terminated polyethylene glycol. 30g was placed in a 90℃ oil bath and mixed for 0.5h under stirring at 300rpm; the mixture was then cooled to 70℃ and vacuum-dried for 1h; then 0.08g of boron trifluoride diethyl ether, a ring-opening addition catalyst, was added dropwise to the reactor at a rate of 0.02mL / min using a constant flow pump. The ring-opening addition reaction was carried out for 4h under a nitrogen atmosphere at 90℃ and stirring at 300rpm to obtain an aqueous epoxy emulsifier; the mass ratio of glycidyl ether epoxy resin E51 to hydroxyl-terminated polyethylene glycol 6000 was 1:7.5, the epoxy value of glycidyl ether epoxy resin E51 was 0.51mol / 100g, and the molar ratio of epoxy groups in glycidyl ether epoxy resin E51 to hydroxyl groups in hydroxyl-terminated polyethylene glycol 6000 was 2:1; the mass ratio of boron trifluoride diethyl ether, a ring-opening addition catalyst, to glycidyl ether epoxy resin E51 was 2:

100. (2) 1.5g of the aqueous epoxy emulsifier and 10g of deionized water obtained in step (1) were mixed at 30℃ and 150rpm for 0.5h to obtain an aqueous phase; 10g of glycidyl ether epoxy resin E51, 2g of active epoxy diluent hexanediol diglycidyl ether, and 1g of active epoxy diluent γ-glycidyl etheroxypropyltrimethoxysilane were mixed at 40℃ and 200rpm for 0.5h to obtain an oil phase; then the oil phase was added dropwise to the aqueous phase at a rate of 1mL / min using a constant flow pump, and mixed at 30℃ and 600rpm for 3h, and then degassed in a planetary mixer at 1500rpm for 1min to obtain an aqueous epoxy emulsion.

2. The aqueous epoxy emulsion prepared by the method of claim 1.

3. The application of the waterborne epoxy emulsion according to claim 2 in coatings.

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