A method for preparing an aqueous epoxy resin emulsifier and emulsion thereof

Abstract

This invention discloses a waterborne epoxy resin emulsifier and its emulsion preparation method, relating to the field of environmentally friendly coatings technology. The invention involves mixing and reacting epoxy resin and a terminal amine-type polyether amine of a specific molecular weight in a solvent to obtain a waterborne epoxy resin emulsifier. This invention prepares the waterborne epoxy resin emulsifier under catalyst-free conditions. The resulting emulsifier has a structure homologous to epoxy resin and exhibits excellent compatibility. The waterborne epoxy resin emulsion prepared based on this emulsifier has uniform particle size and good stability, solving the problems of poor compatibility and easy migration of traditional externally added emulsifiers, as well as the need for catalysts in chemical modification methods. It can be widely used in fields such as environmentally friendly anti-corrosion coatings.

Description

Technical Field

[0001] This invention relates to the field of environmentally friendly coatings technology, and in particular to a water-based epoxy resin emulsifier and a method for preparing its emulsion. Background Technology

[0002] Epoxy resins are widely used in various fields such as metal corrosion protection, adhesives, and composite materials due to their excellent bonding properties, chemical corrosion resistance, mechanical properties, and electrical insulation. However, traditional epoxy resins are oil-based systems, and their dilution and dispersion processes rely on large amounts of organic solvents, releasing large amounts of volatile organic compounds (VOCs) during the construction phase. These VOCs not only cause serious environmental pollution but also directly harm human health, which is inconsistent with the current green chemical development concept. Therefore, the water-based transformation of epoxy resins has become a core direction for industry development.

[0003] Waterborne epoxy resin emulsions, using water as the dispersion medium, possess significant advantages such as low VOC content, safety and environmental friendliness, and convenient storage and transportation. The overall performance of these emulsions hinges on the research and development level of the emulsifier, making it a core focus of waterborne epoxy technology development. Existing waterborne epoxy emulsifiers are mainly divided into two categories: externally applied emulsifiers and chemically modified emulsifiers. However, both have significant drawbacks: externally applied emulsifiers have poor compatibility with epoxy resins, easily migrating and precipitating within the system, leading not only to insufficient emulsion stability but also significantly reducing the water resistance and adhesion of subsequent metal anti-corrosion coatings; chemically modified emulsifiers achieve self-emulsification by introducing hydrophilic groups into the epoxy resin molecular chain, but existing preparation technologies mostly rely on catalysts to initiate the reaction, making the process more complex, and residual catalysts can adversely affect product performance. The emulsifying activity of existing waterborne epoxy resin emulsifiers varies, resulting in a wide particle size distribution and poor stability of the emulsion, which makes it difficult to meet the application requirements of high-performance waterborne epoxy emulsions in fields such as metal corrosion protection, adhesives, and composite materials.

[0004] In summary, existing waterborne epoxy resin emulsifiers and their emulsion preparation technologies still have many shortcomings. Developing a catalyst-free, simple, stable, and low-cost method for preparing waterborne epoxy resin emulsifiers and their emulsions is of great significance for promoting the industrial application of waterborne epoxy resins in the field of environmentally friendly coatings, and has become a technical problem that the industry urgently needs to solve. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing an aqueous epoxy resin emulsifier and its emulsion, so as to solve the problems existing in the prior art.

[0006] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of this invention is to provide a method for preparing an aqueous epoxy resin emulsifier, comprising the following steps: The aqueous epoxy resin emulsifier is obtained by mixing and reacting epoxy resin and amine-terminated polyetheramine in a solvent. The molecular weight of the terminal amine polyetheramine is 1000-5000; The mixing reaction is carried out at a temperature of 100-135℃ for 3-6 hours. The molar ratio of the terminal amine polyetheramine to the epoxy resin is 1:1 to 1:5.

[0007] As a further preferred embodiment of the present invention, the epoxy resin includes E51, E44 or E20.

[0008] As a further preferred embodiment of the present invention, the solvent is propylene glycol methyl ether (PM).

[0009] As a further preferred embodiment of the present invention, the amount of the solvent is 10-30 wt. of the total amount of the terminal amine polyetheramine and epoxy resin.

[0010] As a further preferred embodiment of the present invention, mechanical stirring is performed during the mixing reaction, and the stirring speed is 300-600 r / min.

[0011] As a further preferred embodiment of the present invention, the epoxy resin is first dissolved in a solvent, and then an amine-terminated polyetheramine is added at 70-80°C.

[0012] The second technical solution of the present invention is to provide an aqueous epoxy resin emulsifier prepared by the above preparation method.

[0013] The third technical solution of this invention provides a method for preparing an aqueous epoxy resin emulsion, comprising the following steps: The above-mentioned waterborne epoxy resin emulsifier is mixed with epoxy resin, then water is added, and the mixture is stirred and reacted to obtain the waterborne epoxy resin emulsion.

[0014] As a further preferred embodiment of the present invention, the reaction system temperature when water is added is 35-55 °C; and the stirring reaction time is 30-90 min. As a further preferred embodiment of the present invention, the waterborne epoxy resin emulsifier is 10-50 wt. of the epoxy resin.

[0015] As a further preferred embodiment of the present invention, the mass of water is 10-50 wt% of the mass of the aqueous epoxy resin emulsion.

[0016] As a further preferred embodiment of the present invention, the stirring speed during the reaction is 500-1000 r / min.

[0017] The fourth technical solution of the present invention: providing an aqueous epoxy resin emulsion prepared by the above preparation method.

[0018] Fifth technical solution of the present invention: to provide the application of the above-mentioned waterborne epoxy resin emulsion in the field of coatings.

[0019] As a further preferred embodiment of the present invention, the present invention provides the application of the above-mentioned waterborne epoxy resin emulsion in the field of environmentally friendly anti-corrosion coatings.

[0020] This invention utilizes terminal amine-type polyether amines of a specific molecular weight to chemically modify epoxy resin, giving the modified epoxy resin hydrophilic and lipophilic properties, thus creating a high-performance waterborne epoxy resin emulsifier (AE). This AE is then compounded with epoxy resin, and deionized water is added dropwise, followed by a phase inversion process to prepare a waterborne epoxy resin emulsion. The emulsifier AE has a homologous molecular structure to epoxy resin, exhibiting excellent compatibility and avoiding the migration and stratification problems associated with traditional externally added emulsifiers. This results in a waterborne epoxy resin emulsion with excellent stability. Furthermore, using water as the dispersion medium reduces VOC emissions, meeting green environmental protection requirements.

[0021] To ensure the hydrophilic-lipophilic balance of the emulsifier, this invention selects terminal amine-type polyetheramines with a molecular weight of 1000-5000 as modifiers to modify the epoxy resin matrix. The polyetheramine provides hydrophilic groups; if its molecular weight is too small or too large, it will lead to an imbalance in hydrophilic and lipophilic properties, affecting the emulsifier's performance. An amphiphilic emulsifier (AE) is prepared by a ring-opening grafting reaction between the epoxy groups on the epoxy resin and the amino groups on the polyetheramine under catalyst-free conditions. This simplifies the preparation process and effectively avoids the adverse effects of catalyst residue on product performance. The resulting emulsifier possesses both high emulsifying activity and good compatibility, laying the foundation for the stable preparation of subsequent emulsions.

[0022] This invention enables targeted control of product performance, resulting in emulsions with uniform particle size that do not separate after standing for 90 days or after centrifugation at 3000 r / min for 30 min, exhibiting excellent stability and fully meeting the application requirements in the field of environmentally friendly coatings.

[0023] The preparation process of this invention is mild and easy to operate. The solvent used can be effectively removed, the emulsion uses water as the dispersion medium, and the content of volatile organic compounds (VOCs) is extremely low, which meets the requirements of environmental protection policies and the concept of green chemical development. At the same time, the raw materials used are easy to obtain, the cost is controllable, and it has the potential for large-scale industrial production.

[0024] The present invention discloses the following technical effects: This invention successfully prepared a self-emulsifying emulsifier (AE) with a structure homologous to the epoxy resin backbone by directly reacting terminal amine-type polyetheramines with a molecular weight of 1000-5000 with epoxy resin under catalyst-free conditions. This fundamentally solves the migration and precipitation problems caused by poor compatibility of traditional added nonionic emulsifiers, and significantly improves the long-term stability and water resistance of the emulsion and the final coating.

[0025] This invention provides a waterborne epoxy resin emulsifier preparation process that eliminates the need for a catalyst, simplifying the synthesis steps, reducing production costs, and avoiding the adverse effects of catalyst residue on product performance and environmental friendliness. The emulsifier in this invention possesses an ideal hydrophilic-lipophilic balance, and combined with an optimized phase-inversion emulsification process, results in a waterborne epoxy emulsion with uniform particle size distribution, forming a stable oil-in-water system. Furthermore, the entire system exhibits extremely low VOC content, aligning with the development trend of green and environmentally friendly coatings, and is suitable for applications such as high-performance waterborne anti-corrosion coatings. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 The color change of the system before and after the reaction of the waterborne epoxy resin emulsifier in Example 1 is shown.

[0028] Figure 2 The image shows the Fourier transform infrared (FT-IR) spectra of polyetheramine, epoxy resin, and waterborne epoxy resin emulsifier (AE) in Example 1.

[0029] Figure 3 The thermogravimetric (TGA) graphs of polyetheramine, epoxy resin and waterborne epoxy resin emulsifier (AE) in Example 1 are shown.

[0030] Figure 4 The centrifugal stability and 90-day static stability of the aqueous epoxy resin emulsions prepared by polyetheramines of different molecular weights in Example 8 are shown.

[0031] Figure 5 The centrifugal stability of the aqueous epoxy resin emulsion prepared in Example 5 is shown in (a), which is a graph showing the relationship between the centrifugal stability of the emulsion and the emulsification temperature; (b) is a graph showing the relationship between the centrifugal stability of the emulsion and the molar ratio of the emulsifier and the amount of emulsifier added; and (c) is a comparison graph showing the appearance of the prepared aqueous epoxy emulsion after centrifugation under different molar ratios of polyetheramine in the emulsifier and epoxy resin.

[0032] Figure 6 The static stability of the aqueous epoxy resin emulsion prepared in Example 5 is shown in (a) the static stability relationship of the emulsion after 90 days under different molar ratios of polyetheramine in the emulsifier to epoxy resin (percentage of unseparated volume to total volume); and (b) the comparison of the appearance of the corresponding emulsion after 90 days of static standing.

[0033] Figure 7 The particle size distribution of aqueous epoxy resin emulsions (labeled as 1:1-30%) prepared by different molar ratios of polyetheramine and epoxy resin in the emulsifier in Example 5 is shown. Among them, (a) is a polyetheramine to epoxy resin molar ratio of 1:1 (labeled as 1:1-30%); (b) is a polyetheramine to epoxy resin molar ratio of 1:4 (labeled as 1:4-30%).

[0034] Figure 8 The electrochemical impedance spectroscopy (EIS) of the aqueous epoxy resin coating (labeled as 1:4-30%) prepared in Example 9 after immersion in 3.5% NaCl solution for 10 h is shown; where (a) is the Nyquist plot and (b) is the Bode plot. Detailed Implementation

[0035] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0036] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0037] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0038] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0039] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0040] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0041] The phase inversion process described in this embodiment of the invention is a well-known technique to those skilled in the art. Specifically, after the epoxy resin and emulsifier are thoroughly mixed under high-speed stirring, deionized water is slowly added to the system. At this point, the system is a water-in-oil (W / O) emulsion. When the amount of water increases to a certain critical value (phase inversion point), the system changes from a water-in-oil (W / O) emulsion to an oil-in-water (O / W) emulsion. Water is then added to dilute the emulsion to the required solid content to obtain an aqueous epoxy resin emulsion.

[0042] All raw materials used in the following embodiments of the present invention were purchased commercially: epoxy resins (epoxy resin E51, epoxy resin E44, and epoxy resin E20) and water-based epoxy curing agent (industrial grade) were purchased from Baling Petrochemical Co., Ltd.; polyetheramines with a molecular weight of 1000-5000 were purchased from Yangzhou Chenhua New Materials Co., Ltd.; and propylene glycol methyl ether (analytical grade) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. Deionized water was prepared in the laboratory. Unless otherwise specified, room temperature in the present invention is 25±2 °C.

[0043] The amine-terminated polyetheramines used in the embodiments and comparative examples of this invention are poly(ethylene oxide-co-propylene oxide) etheramines with single-terminal primary amine end capping, and their general structural formula is as follows: ; Where x is the number of repeating units in ethylene oxide (EO) and y is the number of repeating units in propylene oxide (PO).

[0044] The polyetheramines of different molecular weights used in the examples and comparative examples are as follows: Table 1 Ethylene oxide repeating unit (EO), i.e., -CH2CH2O-, provides hydrophilicity; propylene oxide repeating unit (PO), i.e. -CH(CH3)CH2O-, provides lipophilicity.

[0045] Example 1 This embodiment provides a method for preparing an aqueous epoxy resin emulsifier, the specific steps of which are as follows: Epoxy resin was dissolved in propylene glycol methyl ether (PM), and the mixture was heated to 70°C and kept at a stable temperature. Polyether amine was then slowly added dropwise to the mixture. After the addition was complete, the temperature was raised to 110°C while maintaining a mechanical stirring rate of 400 r / min. The mixture was kept at this temperature for 4 h. After the reaction was completed, the mixture was cooled to room temperature and the solvent PM was removed by rotary evaporation at 85°C for 30 min to obtain the waterborne epoxy resin emulsifier (AE).

[0046] In this embodiment, the molar ratio of polyetheramine to epoxy resin is 1:4, and the amount of solvent PM added is 15 wt.% of the total mass of polyetheramine and epoxy resin; the epoxy resin used is epoxy resin E51; the polyetheramine used has a molecular weight of 3000, wherein the EO number is 58 and the PO number is 8.

[0047] In this embodiment, the system was lighter in color before the reaction and turned pale yellow after the reaction. This may be due to the oxidation of the amino groups in the polyetheramine (e.g., ...). Figure 1 (As shown).

[0048] Figure 2 The following are the Fourier Transform Infrared (FT-IR) spectra of the polyetheramine, epoxy resin, and waterborne epoxy resin emulsifier (AE) in Example 1. The AE curve of the synthesized product emulsifier is located at 914 cm⁻¹. -1 The absorption peak of the epoxy group becomes flat, indicating that the epoxy group has been consumed; 1182 cm⁻¹ -1 The presence of characteristic peaks at 3443 cm⁻¹ indicates that the synthesized emulsifier retains the hydrophilic ether bond structure. -1 The area of ​​the −OH absorption peak increased significantly, which also confirmed that the reaction yielded the target product.

[0049] Figure 3 The thermogravimetric (TGA) graphs of polyetheramine, epoxy resin, and waterborne epoxy resin emulsifier (AE) in Example 1 are shown. The emulsifier AE experienced a weight loss of 5.0% at 50-320 °C, which may be attributed to the solvent PM in the product. In the 320-600 °C range, AE experienced a weight loss of 91.6% at 50-320 °C, and its thermal decomposition temperature falls between that of the raw materials polyetheramine and epoxy resin, further indicating successful grafting and the yield of the corresponding emulsifier.

[0050] Example 2 This embodiment provides a method for preparing an aqueous epoxy resin emulsifier, the specific steps of which are as follows: Epoxy resin was dissolved in propylene glycol methyl ether (PM), and the mixture was heated to 70°C and kept at a stable temperature. Polyether amine was then slowly added dropwise to the mixture. After the addition was complete, the temperature was raised to 110°C while maintaining a mechanical stirring rate of 400 r / min. The mixture was kept at this temperature for 4 h. After the reaction was completed, the mixture was cooled to room temperature and the solvent PM was removed by rotary evaporation at 85°C for 30 min to obtain the waterborne epoxy resin emulsifier (AE).

[0051] In this embodiment, the molar ratio of polyetheramine to epoxy resin is 1:2, and the amount of solvent PM added is 15 wt.% of the total mass of polyetheramine and epoxy resin; the epoxy resin used is epoxy resin E51, and the polyetheramine used is terminal amine type with a molecular weight of 3000, wherein the EO number is 58 and the PO number is 8.

[0052] Example 3 This embodiment provides a method for preparing an aqueous epoxy resin emulsifier, the specific steps of which are as follows: Epoxy resin was dissolved in propylene glycol methyl ether (PM), and the mixture was heated to 70°C and kept at a stable temperature. Polyether amine was then slowly added dropwise to the mixture. After the addition was complete, the temperature was raised to 110°C while maintaining a mechanical stirring rate of 400 r / min. The mixture was kept at this temperature for 4 h. After the reaction was completed, the mixture was cooled to room temperature and the solvent PM was removed by rotary evaporation at 85°C for 30 min to obtain the waterborne epoxy resin emulsifier (AE).

[0053] In this embodiment, the molar ratio of polyetheramine to epoxy resin is 1:4, and the amount of solvent PM added is 15 wt.% of the total mass of polyetheramine and epoxy resin; the epoxy resin used is epoxy resin E51, and the polyetheramine used is terminal amine type with a molecular weight of 1000, wherein the EO number is 19 and the PO number is 3.

[0054] Example 4 This embodiment provides a method for preparing an aqueous epoxy resin emulsifier, the specific steps of which are as follows: Epoxy resin was dissolved in propylene glycol methyl ether (PM), and the mixture was heated to 70°C and kept at a stable temperature. Polyether amine was then slowly added dropwise to the mixture. After the addition was complete, the temperature was raised to 130°C while maintaining a mechanical stirring rate of 400 r / min. The mixture was kept at this temperature for 4 h. After the reaction was completed, the mixture was cooled to room temperature and the solvent PM was removed by rotary evaporation at 85°C for 30 min to obtain the waterborne epoxy resin emulsifier (AE).

[0055] In this embodiment, the molar ratio of polyetheramine to epoxy resin is 1:4, and the amount of solvent PM added is 25 wt.% of the total mass of polyetheramine and epoxy resin; the epoxy resin used is epoxy resin E51, and the polyetheramine used is terminal amine type with a molecular weight of 2000, of which the EO number is 31 and the PO number is 10.

[0056] Comparative Example 1 This comparative example provides a method for preparing an aqueous epoxy resin emulsifier, the specific steps of which are as follows: Epoxy resin was dissolved in propylene glycol methyl ether (PM), and the mixture was heated to 70°C and kept at a stable temperature. Polyether amine was then slowly added dropwise to the mixture. After the addition was complete, the temperature was raised to 90°C while maintaining a mechanical stirring rate of 400 r / min. The mixture was kept at this temperature for 4 h. After the reaction was completed, the mixture was cooled to room temperature and the solvent PM was removed by rotary evaporation at 85°C for 30 min to obtain the waterborne epoxy resin emulsifier (AE).

[0057] In this embodiment, the molar ratio of polyetheramine to epoxy resin is 1:4, and the amount of solvent PM added is 15 wt.% of the total mass of polyetheramine and epoxy resin; the epoxy resin used is epoxy resin E51, and the polyetheramine used is terminal amine type with a molecular weight of 3000, wherein the EO number is 58 and the PO number is 8.

[0058] Comparative Example 2 This comparative example provides a method for preparing an aqueous epoxy resin emulsifier, the specific steps of which are as follows: Epoxy resin was dissolved in propylene glycol methyl ether (PM), and the mixture was heated to 70°C and kept at a stable temperature. Polyether amine was then slowly added dropwise to the mixture. After the addition was complete, the temperature was raised to 110°C while maintaining a mechanical stirring rate of 400 r / min. The mixture was kept at this temperature for 8 hours. After the reaction was completed, the mixture was cooled to room temperature and the solvent PM was removed by rotary evaporation at 85°C for 30 minutes to obtain the waterborne epoxy resin emulsifier (AE).

[0059] In this embodiment, the molar ratio of polyetheramine to epoxy resin is 1:4, and the amount of solvent PM added is 15 wt.% of the total mass of polyetheramine and epoxy resin; the epoxy resin used is epoxy resin E51, and the polyetheramine used is terminal amine type with a molecular weight of 3000, wherein the EO number is 58 and the PO number is 8.

[0060] Comparative Example 3 This comparative example provides a method for preparing an aqueous epoxy resin emulsifier, the specific steps of which are as follows: Epoxy resin was dissolved in propylene glycol methyl ether (PM) solvent, and the mixture was then heated to 100°C and kept at a stable temperature. Polyetheramine was then slowly added dropwise to the mixture. After the addition of polyetheramine was complete, the temperature of the mixture was raised to 110°C while maintaining a mechanical stirring rate of 400 r / min. The mixture was kept at this temperature for 4 hours. After the reaction was completed, the mixture was cooled to room temperature and the solvent PM was removed by rotary evaporation at 85°C for 30 minutes to obtain the waterborne epoxy resin emulsifier (AE).

[0061] In this comparative example, the molar ratio of polyetheramine to epoxy resin was 1:1, and the amount of solvent PM added was 15 wt.% of the total mass of polyetheramine and epoxy resin; the epoxy resin used was epoxy resin E51, and the polyetheramine used was terminal amine type with a molecular weight of 3000, of which the EO number was 58 and the PO number was 8.

[0062] Example 5 This embodiment provides an aqueous epoxy resin emulsion, and the preparation steps are as follows: The aqueous epoxy resin emulsifier (AE) prepared in Example 1 was mixed with epoxy resin, wherein the amount of aqueous epoxy resin emulsifier (AE) added was 30 wt.% of the epoxy resin; then the mixture was heated to 40 °C and kept constant, and stirred continuously at a mechanical stirring rate of 800 r / min, while deionized water (the mass of deionized water accounted for 50 wt.% of the total mass of the final aqueous epoxy resin emulsion) was slowly added dropwise to the system; after the addition was completed, the above temperature and stirring rate were maintained and emulsification was continued for 60 min, and a stable aqueous epoxy resin emulsion was obtained by reverse inversion process.

[0063] Example 6 This embodiment provides an aqueous epoxy resin emulsion, and the preparation steps are as follows: The aqueous epoxy resin emulsifier (AE) prepared in Example 1 was mixed with epoxy resin, wherein the amount of aqueous epoxy resin emulsifier (AE) added was 25 wt.% of the epoxy resin; then the mixture was heated to 35°C and kept constant, and stirred continuously at a mechanical stirring rate of 800 r / min, while deionized water (the mass of deionized water accounted for 45 wt.% of the total mass of the final aqueous epoxy resin emulsion) was slowly added dropwise to the system; after the addition was completed, the above temperature and stirring rate were maintained and emulsification was continued for 60 min, and a stable aqueous epoxy resin emulsion was obtained by reverse inversion process.

[0064] Example 7 This embodiment provides an aqueous epoxy resin emulsion, and the preparation steps are as follows: The aqueous epoxy resin emulsifier (AE) prepared in Example 1 was mixed with epoxy resin, wherein the amount of aqueous epoxy resin emulsifier (AE) added was 35 wt.% of the epoxy resin; then the mixture was heated to 45°C and kept constant, and stirred continuously at a mechanical stirring rate of 800 r / min, while deionized water (the mass of deionized water accounted for 50 wt.% of the total mass of the final aqueous epoxy resin emulsion) was slowly added dropwise to the system; after the addition was completed, the above temperature and stirring rate were maintained and emulsification was continued for 60 min, and a stable aqueous epoxy resin emulsion was obtained by reverse inversion process.

[0065] Example 8 This embodiment provides an aqueous epoxy resin emulsion, and the preparation steps are as follows: The aqueous epoxy resin emulsifiers (AE) of different molecular weights prepared in Examples 1, 3, and 4 were mixed with epoxy resin, wherein the amount of aqueous epoxy resin emulsifier (AE) added was 30 wt.% of the epoxy resin; then the mixture was heated to 40°C and kept constant, and stirred continuously at a mechanical stirring rate of 800 r / min, while deionized water (the mass of deionized water accounted for 50 wt.% of the total mass of the final aqueous epoxy resin emulsion) was slowly added dropwise to the system; after the addition was completed, the above temperature and stirring rate were maintained and emulsification was continued for 60 min, and a stable aqueous epoxy resin emulsion was obtained by reverse inversion process.

[0066] Example 9 This embodiment provides a method for preparing an aqueous epoxy resin coating, and the preparation steps are as follows: Take 10 g of the waterborne epoxy resin emulsion prepared in Example 5, add 2 g of waterborne epoxy curing agent and mix thoroughly. After ultrasonic treatment for 30 min, apply it to the surface of Q235 carbon steel plate substrate and dry it in an oven at 50℃ for 6 h to obtain the waterborne epoxy resin coating.

[0067] Comparative Example 4 This comparative example provides an aqueous epoxy resin emulsion, and the preparation steps are as follows: The aqueous epoxy resin emulsifier (AE) prepared in Example 1 was mixed with epoxy resin, wherein the amount of aqueous epoxy resin emulsifier (AE) added was 8 wt.% of the epoxy resin; then the mixture was heated to 40°C and kept constant, and stirred continuously at a mechanical stirring rate of 800 r / min, while deionized water (the mass of deionized water accounted for 50 wt.% of the total mass of the final aqueous epoxy resin emulsion) was slowly added dropwise to the system; after the addition was completed, the above temperature and stirring rate were maintained and emulsification was continued for 60 min, and a stable aqueous epoxy resin emulsion was obtained by reverse inversion process.

[0068] Comparative Example 5 This comparative example provides an aqueous epoxy resin emulsion, and the preparation steps are as follows: The aqueous epoxy resin emulsifier (AE) prepared in Example 1 was mixed with epoxy resin, wherein the amount of aqueous epoxy resin emulsifier (AE) added was 30 wt.% of the epoxy resin; then the mixture was heated to 70°C and kept constant, and stirred continuously at a mechanical stirring rate of 800 r / min, while deionized water (the mass of deionized water accounted for 50 wt.% of the total mass of the final aqueous epoxy resin emulsion) was slowly added dropwise to the system; after the addition was completed, the above temperature and stirring rate were maintained and emulsification was continued for 60 min, and a stable aqueous epoxy resin emulsion was obtained by reverse inversion process.

[0069] Comparative Example 6 This comparative example provides an aqueous epoxy resin emulsion, and the preparation steps are as follows: The aqueous epoxy resin emulsifier (AE) prepared in Example 1 was mixed with epoxy resin, wherein the amount of aqueous epoxy resin emulsifier (AE) added was 30 wt.% of the epoxy resin; then the mixture was heated to 40°C and kept constant, and stirred continuously at a mechanical stirring rate of 800 r / min, while deionized water (the mass of deionized water accounted for 70 wt.% of the total mass of the final aqueous epoxy resin emulsion) was slowly added dropwise to the system; after the addition was completed, the above temperature and stirring rate were maintained and emulsification was continued for 60 min, and a stable aqueous epoxy resin emulsion was obtained by reverse inversion process.

[0070] Figure 4 The figure shows the centrifugal stability of waterborne epoxy resin emulsions prepared by polyetheramines with different molecular weights in Example 8. As can be seen from the figure, with the increase of the molecular weight of polyetheramine, the emulsion prepared by adding 30% of the emulsifier when the molecular weight of polyetheramine is 3000 has excellent centrifugal stability and static stability, showing good emulsifying performance.

[0071] Figure 5 The centrifugal stability of the aqueous epoxy resin emulsion prepared in Example 5 is shown in Figure 5. Centrifugal stability refers to the percentage of the total volume that does not separate after centrifugation at 3000 r / min for 30 min. Figure (a) shows the relationship between the centrifugal stability of the emulsion and emulsification temperature; Figure (b) shows the relationship between the centrifugal stability of the emulsion and the molar ratio of the emulsifier and the amount of emulsifier added; Figure (c) compares the appearance of the prepared aqueous epoxy emulsion after centrifugation under different molar ratios of polyetheramine and epoxy resin in the emulsifier. As can be seen from the figures, when the molar ratio of emulsifier (AE) is 1:4, the amount of emulsifier added is 30 wt.%, and the emulsification temperature is 40 °C, the prepared emulsion exhibits excellent centrifugal stability, remaining unseparated after centrifugation at 3000 r / min for 30 min, demonstrating good emulsification performance.

[0072] Figure 6 The static stability of the aqueous epoxy resin emulsion prepared in Example 5 is shown in Figure (a). Figure (a) shows the relationship between the static stability of the emulsion after 90 days under different molar ratios of polyetheramine (AE) in the emulsifier and epoxy resin; Figure (b) shows a comparison of the appearance of the corresponding emulsions after 90 days of static standing. As can be seen from the figures, under the conditions of an emulsifier (AE) molar ratio of 1:4, an emulsifier addition of 30 wt.%, and an emulsification temperature of 40 °C, the prepared emulsion did not exhibit stratification after standing for 90 days in an environment of 15-30 °C, demonstrating good static stability.

[0073] Figure 7 The figure shows the particle size distribution of aqueous epoxy resin emulsions prepared with different molar ratios of polyetheramine and epoxy resin in the emulsifier in Example 5. (a) represents a polyetheramine to epoxy resin molar ratio of 1:1 (labeled as 1:1-30%); (b) represents a polyetheramine to epoxy resin molar ratio of 1:4 (labeled as 1:4-30%). As can be seen from the figure, when the emulsifier (AE) molar ratio is 1:1, the emulsifier addition is 30 wt.%, and the emulsification temperature is 40 ℃, the average particle size distribution of the prepared emulsion is around 1100 nm, indicating poor emulsification. When the emulsifier (AE) molar ratio is 1:4, the emulsifier addition is 30 wt.%, and the emulsification temperature is 40 ℃, the average particle size distribution of the prepared emulsion is around 1.5 nm, indicating better emulsification. This result is consistent with the conclusions of the centrifugal stability and static stability tests mentioned above.

[0074] In summary, the waterborne epoxy emulsifier and emulsion prepared by the catalyst-free modification of polyetheramines with a specific molecular weight have excellent performance and are environmentally friendly and safe, and have important industrial application value in the field of environmentally friendly coatings.

[0075] Figure 8 shows the electrochemical impedance spectroscopy (EIS) of the aqueous epoxy resin coating (labeled as 1:4-30%) in Example 9 after immersion in 3.5% NaCl solution for 10 h; where (a) is the Nyquist plot and (b) is the Bode plot. As can be seen from the figure, under the above immersion conditions, the impedance modulus |Z| at 0.01 Hz in the low-frequency region is... 0.01Hz Reaching 1.6×10 6 Ω·cm 2 This indicates that it has excellent resistance to salt corrosion.

[0076] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing an aqueous epoxy resin emulsifier, characterized in that, Includes the following steps: The aqueous epoxy resin emulsifier is obtained by mixing and reacting epoxy resin and amine-terminated polyetheramine in a solvent. The molecular weight of the terminal amine polyetheramine is 1000-5000; The mixing reaction is carried out at a temperature of 100-135℃ for 3-6 hours. The molar ratio of the terminal amine polyetheramine to the epoxy resin is 1:1 to 1:

5.

2. The preparation method according to claim 1, characterized in that, The epoxy resin includes E51, E44, or E20.

3. The preparation method according to claim 1, characterized in that, The solvent is propylene glycol methyl ether.

4. The waterborne epoxy resin emulsifier prepared by the preparation method according to any one of claims 1-3.

5. A method for preparing an aqueous epoxy resin emulsion, characterized in that, Includes the following steps: The aqueous epoxy resin emulsifier of claim 4 is mixed with epoxy resin, then water is added to the system, the mixture is stirred and reacted, and the aqueous epoxy resin emulsion is obtained by phase inversion.

6. The preparation method according to claim 5, characterized in that, The system temperature when water is added is 35-55 ℃; the stirring reaction time is 30-90 min.

7. The preparation method according to claim 5, characterized in that, The waterborne epoxy resin emulsifier has a mass of 10-50 wt. of the epoxy resin.

8. The preparation method according to claim 5, characterized in that, The mass of water is 10-50 wt% of the aqueous epoxy resin emulsion.

9. The aqueous epoxy resin emulsion prepared by the preparation method according to any one of claims 5-8.

10. The application of the waterborne epoxy resin emulsion as described in claim 9 in the field of coatings.

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