Waterborne epoxy emulsion as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of coatings, and particularly relates to a waterborne epoxy emulsion as well as a preparation method and application thereof. The preparation method comprises the following steps: mixing first epoxy resin, an organic alcohol polymer and a ring-opening addition reaction catalyst, and carrying out ring-opening addition reaction in protective gas to obtain a waterborne epoxy emulsifier; and mixing the water-based epoxy emulsifier, water, second epoxy resin and an active epoxy diluent, and defoaming to obtain the water-based epoxy emulsion. The waterborne epoxy emulsion is small in viscosity, good in leveling property and good in stability.

Description

Technical Field

[0001] The invention belongs to the technical field of coatings, and specifically relates to a water-based epoxy emulsion and a preparation method and application thereof. Background Art

[0002] The molecular structure of epoxy resin has polar groups such as epoxy terminal groups, hydroxyl groups and ether bonds. These groups can make the epoxy resin molecules produce electromagnetic adsorption or chemical bonds with adjacent interfaces, so its coating can produce strong adhesion with the surface of substrates such as metal, wood, concrete, etc. Epoxy resin has excellent properties in cross-linking density, electrical insulation properties and chemical resistance. It is widely used as a protective coating, including but not limited to the aerospace field, anti-corrosion coating application field, building materials field, industrial floor coating field, etc.

[0003] However, the conventional epoxy resins, such as liquid bisphenol A epoxy resin E-51, have a viscosity of 12000-15000 mPa·s at room temperature, and bisphenol A epoxy acrylate YC3381S is close to solid at room temperature, so it cannot be used directly. A large amount of ketone, ester, and cycloalkane solvents are needed to dissolve it, resulting in a high content of volatile organic compounds (VOC), which is extremely harmful to the environment and human health, limiting its application and development. Therefore, it is imperative to develop environmentally friendly water-based epoxy emulsions to replace solvent-based epoxy emulsions.

[0004] The market demand for waterborne epoxy emulsions is growing rapidly due to their environmental protection and low VOC advantages, but they still face many challenges in improving performance. Among them, viscosity, leveling and stability are important performance indicators of waterborne epoxy emulsions, which have a significant impact on the construction performance, coating quality and durability of the emulsion. At present, waterborne epoxy emulsions on the market have problems such as poor storage stability, high viscosity and poor leveling. The related technology uses emulsifiers constructed with hydrophilic segments such as phytic acid, polyether amine and polyethylene glycol diglycidyl ether, which have poor emulsification effect on epoxy resin in the later stage, resulting in high viscosity of the emulsion. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a water-based epoxy emulsion and a preparation method and application thereof, wherein the water-based epoxy emulsion has low viscosity, good leveling property and good stability.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

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

[0008] The first epoxy resin, the organic alcohol polymer and the ring-opening addition reaction catalyst are mixed, and a ring-opening addition reaction is carried out in a protective gas to obtain a water-based epoxy emulsifier;

[0009] The water-based epoxy emulsifier, water, a second epoxy resin and an active epoxy diluent are mixed and then degassed to obtain a water-based 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 terminal hydroxyl organic alcohol polymer; the terminal hydroxyl organic alcohol polymer includes one or more of polyethylene glycol, polyethylene glycol derivatives, polyvinyl alcohol, polypropylene glycol, PEG blocks, polyoxyalkylene glycol and polyoxyethylene glycol-oxypropylene glycol.

[0011] Preferably, 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.

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

[0013] Preferably, the temperature of the ring-opening addition reaction is 70 to 110° C.; the time of the ring-opening addition reaction is 2 to 8 hours.

[0014] Preferably, the active epoxy diluent includes one or more of ethylene glycol diglycidyl ether, butanediol diglycidyl ether, hexanediol diglycidyl ether, octanediol diglycidyl ether and γ-glycidyloxypropyltrimethoxysilane.

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

[0016] Preferably, the mass ratio of the active 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 scheme.

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

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

[0020] The present invention adds a first epoxy resin to improve the lipophilicity of the water-based epoxy emulsifier, so that it has high compatibility with the emulsion system; adding an organic alcohol polymer can reduce the viscosity of the first epoxy resin and make the water-based epoxy emulsifier hydrophilic, so that the first epoxy resin can be better compatible with the water-based system, so that the water-based epoxy emulsifier can more effectively wrap the droplets of the water-based epoxy emulsion, reduce the interaction between the droplets, reduce the viscosity of the water-based epoxy emulsion, and form a stable interface film at the oil-water interface, reduce the oil-water interfacial tension, thereby improving the stability and leveling of the emulsion; adding a ring-opening addition reaction catalyst can reduce the activation energy of the reaction, accelerate the reaction rate, improve the reaction degree, and make the structure of the water-based epoxy emulsifier uniform and the performance stable, which can further improve the emulsification effect and improve the stability of the water-based epoxy emulsion; adding an active epoxy diluent can reduce the viscosity of the epoxy resin, reduce the surface tension, optimize the emulsification process, and make the epoxy resin more easily dispersed into fine droplets by the water-based epoxy emulsifier to form a stable emulsion. The results of the examples show that the waterborne epoxy emulsion prepared by the present invention has low viscosity, good leveling property and good stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the preparation method of waterborne epoxy emulsion in an embodiment of the present invention;

[0022] Figure 2 This is the infrared spectrum of the water-based epoxy emulsifier prepared in Example 1. DETAILED DESCRIPTION

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

[0024] The first epoxy resin, the organic alcohol polymer and the ring-opening addition reaction catalyst are mixed, and a ring-opening addition reaction is carried out in a protective gas to obtain a water-based epoxy emulsifier;

[0025] The water-based epoxy emulsifier, water, a second epoxy resin and an active epoxy diluent are mixed and then degassed to obtain a water-based epoxy emulsion.

[0026] Unless otherwise specified, the present invention has no special requirements on the sources of the raw materials used, and commercially available products known to those skilled in the art may be used.

[0027] The invention mixes a first epoxy resin, an organic alcohol polymer and a ring-opening addition reaction catalyst, performs a ring-opening addition reaction in a protective gas, and obtains a water-based epoxy emulsifier.

[0028] As an 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, and the specific embodiment is glycidyl ether epoxy resin E51; the epoxy value of the first epoxy resin is 0.41-0.54 mol / 100g, and the specific embodiment is 0.48-0.54 mol / 100g. The epoxy resin used in the present invention has a similar epoxy value to the water-based epoxy emulsion system and has a similar surface tension, which helps to improve the compatibility of the emulsifier with the water-based epoxy emulsion system and enhance the emulsification effect. The epoxy value of the epoxy resin will affect the mechanical strength and thermal stability after the emulsion is cured.

[0029] As an 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, polyoxyalkylene glycol and polyoxyethylene glycol-oxypropylene glycol, and in a specific embodiment, it is polyethylene glycol; the polyethylene glycol includes one or more of polyethylene glycol 2000, polyethylene glycol 4000, polyethylene glycol 6000, polyethylene glycol 8000 and polyethylene glycol 10000, and in a specific embodiment, it is polyethylene glycol 6000 or polyethylene glycol 8000; the weight average molecular weight of the organic alcohol polymer is 2000-10000, and in a specific embodiment, it is 4000-8000; the content of hydroxyl in the organic alcohol polymer is 12-63 mgKOH / g, and in a specific embodiment, it is 20-50 mgKOH / g. The hydroxyl content in the organic alcohol polymer will affect the hydrophilicity of the prepared emulsifier. The organic alcohol polymer used in the present invention can reduce the viscosity of the epoxy resin and make the water-based epoxy emulsifier have a certain hydrophilicity, so that the epoxy resin can be better compatible with the water-based system.

[0030] As an embodiment, the mass ratio of the first epoxy resin to the organic alcohol polymer is 1:(2.5-12.5), and as another embodiment, it is 1:(5-10); in a specific embodiment 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 group in the first epoxy resin to the hydroxyl group in the organic alcohol polymer is (1-2):1, and in a specific embodiment, 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, so that the epoxy resin having lipophilicity itself is grafted with a hydrophilic group hydroxyl group, and by controlling the ratio of the epoxy resin and the organic alcohol polymer, the obtained water-based epoxy emulsifier has both lipophilicity and hydrophilicity, thereby further improving the stability of the water-based epoxy emulsion.

[0031] As an embodiment, the ring-opening addition reaction catalyst is one or more of boron trifluoride ethyl etherate, tetrabutylammonium bromide, hexadecyltrimethylammonium bromide, triethanolamine and potassium persulfate, and in a specific embodiment, it is boron trifluoride ethyl etherate.

[0032] As an 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 ring-opening addition reaction catalysts require different reaction temperatures and reaction times, and the reaction degrees achieved are also different. The present invention reduces the activation energy of the reaction by limiting the type of ring-opening addition reaction catalyst and the mass ratio of the ring-opening addition reaction catalyst to the epoxy resin, accelerates the reaction rate, shortens the reaction time, and improves the reaction degree, so that the prepared water-based epoxy emulsifier has a uniform structure and stable performance, further improves the emulsification effect, and improves the stability of the water-based epoxy emulsion, which can avoid the problem of low reaction degree and unachievable catalytic reaction effect caused by too low catalyst dosage, and can also avoid the problem of gelation caused by excessive dosage.

[0034] As an embodiment, the first epoxy resin, polyethylene glycol and the ring-opening addition reaction catalyst are mixed as follows: the first epoxy resin and the polyethylene glycol are mixed and dehydrated, and then the ring-opening addition reaction catalyst is added; the first epoxy resin and the polyethylene glycol are mixed under heating and stirring conditions; the heating temperature is 60 to 90°C, and in a specific embodiment, it is 60°C, 70°C, 80°C or 90°C; the stirring rate is 200 to 400rpm, and in another embodiment, it is 250 to 350rpm; in a specific embodiment, the stirring rate is 200rpm, 250rpm, 300rpm, 350rpm or 400rpm; the first epoxy resin and the polyethylene glycol are mixed for 0.5 to 1h, and in a specific embodiment, it is 0.5h or 1h.

[0035] As an embodiment, the dehydration is vacuum dehydration; the dehydration temperature is 60-90°C, and in specific embodiments, it is 60°C, 70°C, 80°C or 90°C; the dehydration time is 20-120min, and in specific embodiments, it is 20min, 40min, 60min, 80min, 100min or 120min. The present invention ensures sufficient dehydration by limiting the temperature and time of dehydration.

[0036] As an embodiment, the method of adding the ring-opening addition reaction catalyst is dropwise addition; 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] The invention can ensure that the ring-opening addition reaction is carried out more fully by limiting the dropping rate of the ring-opening addition reaction catalyst, and can also enhance the controllability of the reaction, thereby avoiding the implosion phenomenon caused by the excessively fast dropping rate, which will cause the product to gel and is not conducive to use.

[0038] As an implementation mode, the protective gas is nitrogen.

[0039] As an embodiment, the temperature of the ring-opening addition reaction is 70-110°C, and in specific embodiments, it is 70°C, 80°C, 90°C, 100°C or 110°C; the time of the ring-opening addition reaction is 2-8h, and in specific embodiments, it is 2h, 3h, 4h, 5h or 6h. The present invention limits the temperature and time of the ring-opening addition reaction to ensure that the ring-opening addition reaction is more fully carried out.

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

[0041] In the present invention, a ring-opening addition reaction occurs between the epoxy group of the epoxy resin and the hydroxyl group to generate an ether bond and release water molecules. The specific reaction formula is as follows:

[0042]

[0043] The present invention improves the lipophilicity of the water-based epoxy emulsifier by adding a first epoxy resin, so that the emulsifier can be compatible with the water-based epoxy emulsion system; reduces the viscosity of the first epoxy resin by adding an organic alcohol polymer, and makes the water-based epoxy emulsifier have a certain hydrophilicity, so that the first epoxy resin can be better compatible with the water-based system. The water-based epoxy emulsifier prepared by the present invention can more effectively wrap the droplets, reduce the interaction between the droplets, and reduce the viscosity of the water-based epoxy emulsion; and when the oil phase is added dropwise to the water phase, the water-based epoxy emulsifier can quickly form a stable interface film at the oil-water interface, reduce the oil-water interfacial tension, thereby improving the stability of the emulsion, and preventing the emulsion from stratification or precipitation during storage, thereby extending the service life of the emulsion.

[0044] The raw materials of the epoxy resin and the organic alcohol polymer used in the present invention are simple, easy to obtain and low-cost, the synthesis method is simple and easy to repeat, 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, so that the aqueous epoxy emulsion prepared subsequently has low viscosity and good stability.

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

[0046] As an embodiment, the water is deionized water; the mass ratio of the aqueous 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] The water-based epoxy emulsifier can reduce the oil-water interfacial tension and enable the epoxy resin to form a stable dispersed phase in water. The mass ratio of the water-based epoxy emulsifier to water in the present invention can ensure that the water-based epoxy emulsifier forms a uniform adsorption layer at the oil-water interface, thereby effectively reducing the oil-water interfacial tension, promoting the emulsification process, ensuring the emulsification effect of the emulsifier, reducing the emulsion particle size, and enhancing the stability of the emulsion.

[0048] As an 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, and the specific embodiment is glycidyl ether epoxy resin E51; the epoxy value of the second epoxy resin is 0.41-0.54 mol / 100 g, and the specific embodiment is 0.48-0.54 mol / 100 g. The second epoxy resin in the present invention has a similar epoxy value to the first epoxy resin used in the water-based epoxy emulsifier, has a similar surface tension, can improve the compatibility of the water-based epoxy emulsifier with the water-based epoxy emulsion system, and improve the stability of the emulsion.

[0049] As an embodiment, the active epoxy diluent includes one or more of ethylene glycol diglycidyl ether, butanediol diglycidyl ether, hexanediol diglycidyl ether, octanediol diglycidyl ether and γ-glycidyl ether oxypropyl trimethoxy silane, and in the specific embodiment, hexanediol diglycidyl ether and γ-glycidyl ether oxypropyl trimethoxy silane. The active epoxy diluent used in the present invention can reduce the viscosity and surface tension of the emulsion system, improve fluidity and dispersibility, optimize the emulsification process, and make the epoxy resin more easily dispersed into fine droplets by the emulsifier, forming an emulsion with uniform particle size distribution, thereby helping to improve stability, so that the prepared emulsion has low viscosity and good leveling properties.

[0050] As an embodiment, the mass ratio of the active 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. Too high viscosity will lead to emulsification difficulties and uneven distribution of emulsion particle size; too low viscosity may affect the stability of the emulsion. Therefore, the present invention adds an active epoxy diluent and utilizes its low viscosity characteristics to dilute the high viscosity components in the epoxy resin, improve the fluidity of the system, and ensure that the system has a moderate viscosity, thereby meeting the requirements of the emulsification process. The present invention limits the mass ratio of the active epoxy diluent to the second epoxy resin to ensure that the system has a suitable viscosity before emulsification, further reduces the viscosity of the second epoxy resin, reduces surface tension, optimizes the emulsification process, and makes the second epoxy resin more easily dispersed into fine droplets by the emulsifier to form a stable emulsion, so that the prepared emulsion has better leveling properties.

[0052] As an embodiment, the mass ratio of water to the second epoxy resin is (8-14):10, and in specific embodiments, it is 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 the present invention, water as a continuous phase can dilute the epoxy resin, disperse it into fine emulsion particles, reduce the overall viscosity of the emulsion, help to form emulsion particles with uniform particle size distribution, reduce collisions and agglomeration between particles, thereby improving the stability of the emulsion, avoiding the high viscosity of the emulsion that may be caused by low water content, poor leveling, and avoiding the low viscosity of the emulsion due to high water content, and poor stability. The present invention limits the mass ratio of water to the second epoxy resin to ensure that the emulsion system has good viscosity, leveling and stability.

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

[0054] As an embodiment, the aqueous epoxy emulsifier, water, the second epoxy resin and the active epoxy diluent are mixed as follows: the aqueous epoxy emulsifier is first mixed with water to obtain an aqueous phase; the second epoxy resin and the active epoxy diluent are second mixed to obtain an oil phase; the oil phase is dropped into the aqueous phase for third mixing.

[0055] The present invention adopts the method of dripping the oil phase into the water phase, the water phase is used as the continuous phase, and the oil phase is used as the dispersed phase to be dispersed into fine droplets. Since the surface area of ​​the dispersed phase droplets increases, the emulsifier can more effectively wrap the droplets and reduce the interaction between the droplets, so that the viscosity of the water-based epoxy emulsion is reduced; and when the oil phase is dripped into the water phase, the emulsifier can quickly form a stable interface film at the oil-water interface, reduce the oil-water interfacial tension, thereby improving the stability of the emulsion, and preventing the emulsion from stratification or precipitation during storage, thereby extending the service life of the emulsion.

[0056] As an embodiment, the temperature of the first mixing is 30-40°C, and in a specific embodiment, it is 30°C or 40°C; the first mixing is carried out under stirring; the stirring rate is 100-300rpm, and in another embodiment, it is 150-250rpm; in a specific embodiment, the stirring rate is 100rpm, 150rpm, 200rpm, 250rpm or 300rpm. As an embodiment, the time of the first mixing is 0.5-1h, and in a specific embodiment, it is 0.5h or 1h.

[0057] As an embodiment, the temperature of the second mixing is 30-50°C, and in a specific embodiment, it is 30°C, 40°C or 50°C; the second mixing is carried out under stirring; the stirring rate is 100-300rpm, and in another embodiment, it is 150-250rpm; in a specific embodiment, the stirring rate is 100rpm, 150rpm, 200rpm, 250rpm or 300rpm. As an embodiment, the time of the second mixing is 0.5-1h, and in a specific embodiment, it is 0.5h or 1h.

[0058] As an embodiment, the rate of the dripping is 1 to 8 mL / min, and in specific embodiments, it is 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. The present invention limits the dripping rate to ensure that the third mixing is more fully performed.

[0059] As an embodiment, the temperature of the third mixing is 30-40°C, and in a specific embodiment, it is 30°C or 40°C; the third mixing is carried out under stirring; the stirring rate is 500-700rpm, and in another embodiment, it is 550-650rpm; in a specific embodiment, the stirring rate is 500rpm, 550rpm, 600rpm, 650rpm or 700rpm. As an embodiment, the time of the third mixing is 3-4h, and in a specific embodiment, it is 3h or 4h.

[0060] As an embodiment, the degassing device is a planetary mixer; the degassing time is 1 to 2 minutes, and in a specific embodiment, it is 1 minute or 2 minutes; the degassing speed is 1500 to 2000 rpm, and in a specific embodiment, it is 1500 rpm, 1600 rpm, 1700 rpm, 1800 rpm, 1900 rpm or 2000 rpm. The present invention removes bubbles in the product by limiting the degassing time and speed, ensures the quality and performance of the product, and further improves the stability of the waterborne epoxy emulsion.

[0061] Figure 1 FIG. 1 is a schematic diagram of a process for preparing a water-based epoxy emulsion according to an embodiment of the present invention. Figure 1 As shown, the present invention mixes epoxy resin and polyethylene glycol, removes water, and drops a catalyst into the obtained mixture for synthesis to prepare a water-based epoxy emulsifier; then the obtained water-based epoxy emulsifier is mixed with water to obtain a water phase, and the oil phase obtained by mixing the epoxy resin and the active epoxy diluent is dropped into the water phase for mixing and degassing to obtain a water-based epoxy emulsion.

[0062] The present invention adds epoxy resin to improve the lipophilicity of the water-based epoxy emulsifier, so that the emulsifier can be compatible with the water-based epoxy emulsion system; by adding polyethylene glycol, the viscosity of the epoxy resin is reduced, and the water-based epoxy emulsifier has a certain hydrophilicity, so that the epoxy resin can be better compatible with the water-based system; by adding a catalyst, the activation energy of the reaction is reduced, the reaction rate is accelerated, the reaction degree is increased, the emulsifier structure is uniform, the performance is stable, the emulsification effect is further improved, and the stability of the water-based epoxy emulsion is improved. In addition, the present invention adds a water-based epoxy emulsifier, and the emulsifier can be adsorbed on the surface of the water-based epoxy emulsion droplets to form a protective film to prevent the droplets from aggregating and merging with each other. This protective effect can reduce the disordered collision of the droplets, making the particle size distribution of the droplets more uniform and thus narrower, thereby 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 reduced, the emulsification process is optimized, and the epoxy resin is more easily dispersed into fine droplets by the emulsifier to form a stable emulsion, so that the prepared emulsion has better leveling properties.

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

[0064] As an embodiment, the viscosity of the aqueous epoxy emulsion is 30 to 550 mPa·s, and in specific embodiments, it is 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 to 9, and in specific embodiments, it is 6, 8 or 9; the stability is 1 to 4, and in specific embodiments, it is 1, 2 or 4; the average particle size of the aqueous epoxy emulsion is 500 to 30000 nm, and in specific embodiments, it is 26731 nm, 2527 nm, 998 nm, 852 nm, 7171 nm, 7605 nm, 3944 nm, 5044 nm or 5711 nm.

[0065] The waterborne epoxy emulsion prepared by the invention has low viscosity, good leveling property and good stability.

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

[0067] The present invention has no special limitation on the application field of the coating, and the coating may be applied to the aerospace field, the field of anti-corrosion coatings, the field of building materials, the field of industrial floor coatings, etc.

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

[0069] Example 1

[0070] (1) 14 g of glycidyl ether epoxy resin E5 and 30 g of terminal hydroxyl polyethylene glycol 6000 were placed in an oil bath at 90° C. and mixed for 0.5 h under stirring conditions at 300 rpm; the temperature was lowered to 70° C. and vacuumed to remove water for 1 h; then 0.08 g of a ring-opening addition reaction catalyst boron trifluoride ether was added dropwise to the reactor at a rate of 0.02 mL / min through a constant flow pump, and the ring-opening addition reaction was carried out under nitrogen atmosphere at 90° C. and stirring conditions at 300 rpm for 4 h. A water-based epoxy emulsifier is obtained; the mass ratio of the glycidyl ether epoxy resin E51 to the terminal hydroxyl polyethylene glycol 6000 is 1:7.5, the epoxy value of the glycidyl ether epoxy resin E51 is 0.51 mol / 100 g, and the molar ratio of the epoxy group in the glycidyl ether epoxy resin E51 to the hydroxyl group in the terminal hydroxyl polyethylene glycol 6000 is 2:1; the mass ratio of the ring-opening addition reaction catalyst boron trifluoride ethyl ether to the glycidyl ether epoxy resin E51 is 2:100;

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

[0072] Example 2

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

[0074] Example 3

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

[0076] Example 4

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

[0078] Embodiments 5 to 9

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

[0080] Comparative Example 1

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

[0082] Performance Testing

[0083] (1) The present invention conducted viscosity tests, leveling tests and stability tests on the water-based epoxy emulsions prepared in Examples 1 to 9 and the commercially available water-based epoxy emulsion DY-128. The viscosity test is carried out as follows: according to the single cylinder rotation viscometer method for the determination of adhesive viscosity in accordance with the standard GB / T 2794-2013, the viscosity test is carried out at a test temperature of 25°C for 2 minutes; the leveling test is carried out as follows: according to the standard ASTM D2801 pull-down method for the test method of determining the leveling characteristics of the coating, the leveling is divided into 0 to 10 levels, with 0 being the worst leveling and 10 being the best; the stability test is carried out as follows: according to the standard GB / T 11543-2008 method for the characteristic test of medium and high viscosity emulsions of surfactants and the evaluation method for their emulsification ability, the emulsion is placed at a constant temperature of 40°C for 72 hours, the phenomena presented by the emulsion are observed, and the stability is divided into 1 to 6 levels, with 1 being good uniformity and 6 being complete separation of the two phases; the particle size test is carried out as follows: the morphology of the emulsion droplets is observed under an optical microscope. The prepared emulsion was lightly coated on a glass slide, covered with a cover glass (20×20 mm), and the sample was placed on the stage of the microscope. The objective lens was adjusted to observe the droplet morphology and take pictures. Afterwards, 100 droplets were randomly selected using the matching capture2.4 software to calculate the diameter distribution of the emulsion droplets, and the diameter of the droplets was determined using the three-point circle method. The results are shown in Table 1.

[0084] Table 1 Performance evaluation of waterborne epoxy emulsion

[0085]

[0086]

[0087] It can be seen from the data in Table 1 that the aqueous epoxy emulsion prepared in Example 1 has the lowest viscosity and the best leveling property, but slightly inferior stability; both Examples 2 and 3 have lower viscosities, and Example 3 has better stability; Example 4 has the best stability, but slightly higher viscosity, which is caused by the amount of aqueous epoxy emulsifier used; and Comparative Example 1 has the worst stability and poor leveling property.

[0088] From the above tests, it can be seen that the water-based epoxy emulsion prepared by the present invention has low viscosity, good leveling property and good stability.

[0089] (2) Figure 2 This is the infrared spectrum of the water-based epoxy emulsifier prepared in Example 1.

[0090] Depend on Figure 2 It can be seen that 3460cm -1 The characteristic absorption peak of hydroxyl group -OH in the emulsifier molecule is at 2880cm -1 The peak at 1620cm is the stretching vibration peak of the methylene -CH2- in the polyethylene glycol segment; -1 and 1470cm -1The peak at 1120cm is the vibration absorption peak of the six-membered ring skeleton on the benzene ring in the epoxy resin segment; -1 The stretching vibration peak of the ether bond -CO- is at 840cm -1 It is the characteristic peak of para-substituted benzene ring. From the infrared spectrum, we can see that at 915cm -1 There was no characteristic absorption peak of epoxy group, which proved that the epoxy resin and polyethylene glycol underwent a ring-opening addition reaction and consumed the epoxy group.

[0091] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention rather than all the embodiments. People can also obtain other embodiments based on this embodiment without creativity, 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 following steps are involved: The first epoxy resin, the organic alcohol polymer and the ring-opening addition reaction catalyst are mixed, and a ring-opening addition reaction is carried out in a protective gas to obtain a water-based epoxy emulsifier; The water-based epoxy emulsifier, water, a second epoxy resin and an active epoxy diluent are mixed and then degassed to obtain a water-based epoxy emulsion.

2. The preparation method according to claim 1, characterized in that: The first epoxy resin and the second epoxy resin are independently glycidyl ether epoxy resins; the organic alcohol polymer is a terminal hydroxyl organic alcohol polymer; the terminal hydroxyl organic alcohol polymer includes one or more of polyethylene glycol, polyethylene glycol derivatives, polyvinyl alcohol, polypropylene glycol, PEG block, polyoxyalkylene glycol and polyoxyethylene glycol-oxypropylene glycol.

3. The preparation method according to claim 1 or 2, characterized in that: 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.

4. The preparation method according to claim 1, characterized in that: The ring-opening addition reaction catalyst is one or more of boron trifluoride etherate, tetrabutylammonium bromide, hexadecyltrimethylammonium bromide, triethanolamine and potassium persulfate.

5. The preparation method according to claim 1, characterized in that: The temperature of the ring-opening addition reaction is 70 to 110° C.; the time of the ring-opening addition reaction is 2 to 8 hours.

6. The preparation method according to claim 1, characterized in that: The active epoxy diluent includes one or more of ethylene glycol diglycidyl ether, butanediol diglycidyl ether, hexanediol diglycidyl ether, octanediol diglycidyl ether and γ-glycidyl ether oxypropyl trimethoxy silane.

7. The preparation method according to claim 1, characterized in that: The mass ratio of the water-based epoxy emulsifier to water is (5-25):100; the mass ratio of water to the second epoxy resin is (8-14):

10.

8. The preparation method according to claim 1 or 6, characterized in that: The mass ratio of the active epoxy diluent to the second epoxy resin is (1-5):

10.

9. Aqueous epoxy emulsion prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the water-based epoxy emulsion according to claim 9 in coatings.

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