Preparation method and application of high gloss waterborne epoxy primer that can be used for wet-on-wet

Abstract

This invention provides a method for preparing and applying a high-gloss waterborne epoxy primer suitable for wet-on-wet conditions. Belonging to the field of automotive paint technology, it solves the problem that current waterborne epoxy primers on the market cannot comprehensively meet various requirements, including gloss, flexibility, impact resistance, VOC content, and drying time. This invention proposes a novel preparation method and application scheme. The preparation method includes the following steps: S1 emulsification; S2 resin compounding; S3 mixing; S4 curing agent compounding; S5 preparation of the waterborne epoxy primer. The waterborne epoxy primer prepared by this invention has the following advantages: suitable for wet-on-wet conditions; high gloss, providing excellent visual effects; good flexibility and impact resistance, providing effective protection; short drying time, improving work efficiency; and low VOC content, meeting environmental protection requirements.

Description

Technical Field

[0001] The invention belongs to the technical field of automobile paints, in particular to a preparation method and application of a high-gloss waterborne epoxy primer that can be used for wet-on-wet coating. Background Art

[0002] In the field of modern automotive paint technology, environmental protection and performance are key indicators for measuring the success of new coating research and development. Although the water-based epoxy primers on the market have improved in environmental performance compared to traditional solvent-based primers, they still have several significant technical problems:

[0003] First, the current waterborne epoxy primer does not perform well in terms of gloss, which directly affects the appearance quality of the final coating of the car. A high-gloss primer can not only improve the appearance of the car, but also enhance consumers' overall impression of the vehicle's quality.

[0004] Secondly, flexibility and impact resistance are also shortcomings in the current waterborne epoxy primer technology. Under complex use environments, the primer needs to be flexible enough to adapt to the slight deformation of the metal surface, and also needs to have good impact resistance to resist external physical impact. However, existing waterborne epoxy primer products often fail to meet ideal performance standards in these two aspects, which limits their application in the field of high-end automotive coatings.

[0005] Furthermore, although waterborne epoxy primers have lower volatile organic compound (VOC) content than traditional solvent-based primers, thereby reducing the risk of flammability and explosion, current products still have the problem of high VOC content. High VOC content not only pollutes the environment, but also poses a safety hazard to production and use;

[0006] Finally, the drying time of waterborne epoxy primer is relatively long, which limits production efficiency. On a fast-paced production line, excessive drying time will seriously affect overall production efficiency and cost control, which is difficult for manufacturers to accept.

[0007] In summary, although the existing water-based epoxy primer technology has improved in environmental protection compared with traditional solvent-based products, there are still many problems in key performance indicators such as gloss, flexibility, impact resistance, VOC content and drying time. These problems limit its further application and promotion in the field of automotive coatings. Therefore, it is an urgent need for the industry to develop a water-based epoxy primer with high gloss, excellent flexibility and impact resistance, low VOC content and quick drying characteristics. Summary of the invention

[0008] The purpose of the present invention is to solve the above problems in the prior art and to provide a preparation method and application of a high-gloss waterborne epoxy primer that can be used for wet-on-wet coating.

[0009] The object of the present invention can be achieved by the following technical scheme: a method for preparing a high gloss waterborne epoxy primer that can be used for wet-on-wet, the preparation method comprising the following steps:

[0010] S1 emulsification: adding aqueous liquid E51 epoxy resin, polyethylene glycol 600 and pure water into a homogenizer, starting the homogenizer to perform emulsification, and obtaining an emulsified liquid after the emulsification operation is completed;

[0011] The specific parameter requirements of the water-based liquid E51 epoxy resin are as follows: at 25 degrees Celsius, the viscosity of the water-based liquid E51 epoxy resin is 5500-10000cps; the epoxy value of the water-based liquid E51 epoxy resin is 0.4-0.45Eq / 100g, and the epoxy equivalent of the water-based liquid E51 epoxy resin is 250-260; the chromaticity of the water-based liquid E51 epoxy resin measured by the Gardner method is ≤2;

[0012] The specific parameter requirements of polyethylene glycol 600 are as follows: the hydroxyl value of polyethylene glycol 600 is 170-208 mgKOH / g, the molecular weight of polyethylene glycol 600 is 540-660; the freezing point of polyethylene glycol 600 is 20-25°C; the water content of polyethylene glycol 600 is ≤1%; the pH value of polyethylene glycol 600 in 1% aqueous solution is 5.0-7.0;

[0013] Reasons for choosing water-based liquid E51 epoxy resin:

[0014] 1. Environmental protection: Compared with traditional solvent-based epoxy resins, it has less impact on the environment and extremely low emissions of volatile organic compounds (VOCs), which complies with current environmental regulations and trends.

[0015] 2. Good Adhesion: It has excellent adhesion and can adhere well to a variety of substrates, including metal, wood and some plastics, which makes it an ideal primer material.

[0016] 3. High curing performance: It has fast reaction speed and high fullness after curing, which is very important for improving production efficiency and ensuring coating quality.

[0017] 4. Wet-on-wet application: This resin is particularly suitable for wet-on-wet application. The top layer can be applied when the bottom layer is not completely dry, shortening the production cycle.

[0018] The reasons for the requirements on the parameters of water-based liquid E51 epoxy resin are:

[0019] Viscosity 5500-10000cps (at 25°C): Ensures that the resin has appropriate fluidity to facilitate coating operations and optimize coating uniformity, while ensuring that the resin is stably suspended in the aqueous medium and is not easy to precipitate.

[0020] Epoxy value 0.4-0.45Eq / 100g: reflects the content of epoxy groups in the resin. Epoxy values ​​in this range mean that the resin has good cross-linking density, ensuring the hardness and chemical resistance of the coating.

[0021] Epoxy equivalent weight 250-260: This indicates the number of moles of epoxy groups contained in each gram of resin, which is closely related to the epoxy value. Epoxy equivalent weight within this range helps to balance the curing speed and performance.

[0022] Chroma ≤ 2 (measured by the Gardner method): Low chroma means the resin itself is lighter in color, which helps produce a primer with high appearance quality, especially for applications that are sensitive to the final color.

[0023] Polyethylene glycol 600 was selected for the preparation of waterborne epoxy primer based on the following considerations:

[0024] 1. Solubility and compatibility: It has excellent water solubility and good compatibility with epoxy resin, which helps to form a stable emulsion system;

[0025] 2. Dispersibility: In the emulsification step, polyethylene glycol 600 can help water-based epoxy resin disperse into finer particles, improve the stability of the emulsion, and prevent particle aggregation;

[0026] 3. Adjust the open time: By adjusting the amount of polyethylene glycol 600, the open time of the coating can be effectively controlled. The operating time of the coating before curing is especially important for wet-on-wet applications.

[0027] 4. Improve coating performance: Introducing an appropriate amount of polyethylene glycol 600 helps to improve the flexibility and water resistance of the final coating.

[0028] The reasons for the requirements on polyethylene glycol 600 parameters are:

[0029] Hydroxyl value 170-208mgKOH / g: Hydroxyl value refers to the number of hydroxyl groups contained in each gram of polyethylene glycol. Within this range, good reactivity and crosslinking density between polyethylene glycol and epoxy resin are ensured, thus affecting the mechanical properties and chemical stability of the coating;

[0030] Freezing point 20-25℃: ensures that polyethylene glycol 600 remains liquid at room temperature, making it easy to mix and handle with other components while avoiding material handling problems caused by temperature changes;

[0031] Moisture content ≤ 1%: Controlling moisture content can reduce problems that may occur during preparation and curing, such as bubble formation or inconsistent coating properties;

[0032] pH 5.0-7.0 (in 1% aqueous solution): This pH range indicates that PEG 600 has moderate acidity and alkalinity in aqueous solution, which helps maintain the stability of the emulsion and prevent possible corrosion problems during the coating process.

[0033] Compounding of S2 resin: Add the emulsion and water-based epoxy emulsion into a mixer and mix them evenly to obtain a mixed liquid; the water-based epoxy emulsion is PZ3961-1 water-based epoxy emulsion;

[0034] The reasons for choosing PZ3961-1 water-based epoxy emulsion are:

[0035] 1. Environmental friendliness: As a water-based epoxy emulsion, PZ3961-1 meets environmental protection requirements and has the characteristics of low volatile organic compound (VOC) emissions, which is conducive to improving the working environment and reducing the impact on the environment.

[0036] 2. Compatibility and stability: PZ3961-1 has good compatibility with water-based liquid E51 epoxy resin and other formulation ingredients, and can form a stable emulsion system, which is beneficial to improving the quality and performance of the primer.

[0037] 3. Coating performance: PZ3961-1 can provide excellent adhesion, chemical resistance and water resistance, which are very important for primers and help improve the protective performance and durability of the coating.

[0038] 4. Application performance: PZ3961-1 has good leveling and construction properties. It can be applied by spraying, brushing and other methods. It has a moderate drying speed, which is conducive to the wet-on-wet construction process.

[0039] S3 mixing: adding the leveling agent and the surfactant to the mixed liquid, increasing the speed of the mixer to perform the mixing operation, and after the mixing operation is completed, obtaining the waterborne epoxy primer base material; taking out the waterborne epoxy primer base material for standby use;

[0040] The leveling agent used is BYK3481 leveling agent; the surfactant is a silicone twin structure surfactant, and the specific parameter requirements of the silicone twin structure surfactant are as follows: the flash point of the silicone twin structure surfactant is 140-145℃; at 25℃, the dynamic viscosity of the silicone twin structure surfactant is 640-643mPa.s; at 40℃, the dynamic viscosity of the silicone twin structure surfactant is 248-252mPa.s; the density of the silicone twin structure surfactant is 1.079-1.082g / cm³; the active matter content of the silicone twin structure surfactant is 100%.

[0041] The reasons for choosing BYK3481 leveling agent are:

[0042] 1. Improve leveling: BYK3481 can significantly improve the leveling of the coating, reduce brush marks and orange peel phenomena that may occur during the coating process, and make the coating film smoother and more uniform;

[0043] 2. Improve surface gloss: Good leveling performance helps to improve the gloss of the coating, which is especially important for high-gloss water-based epoxy primer;

[0044] 3. Compatibility: BYK3481 has good compatibility and will not affect the performance of other formula ingredients.

[0045] 4. Environmental protection: As a leveling agent for water-based systems, BYK3481 meets current environmental protection requirements and helps reduce the emission of harmful volatile substances.

[0046] The choice of silicone gemini surfactant in this formulation is based on the following advantages:

[0047] 1. Enhance surface properties: This surfactant can significantly improve the surface properties of coatings, including adhesion, wear resistance and chemical resistance.

[0048] 2. Stability: Silicone gemini surfactants help maintain the stability of other ingredients in the formula, especially during storage and application.

[0049] 3. Improve gloss and smoothness: This surfactant can improve the gloss and smoothness of the coating film, which is especially important for high-gloss primers.

[0050] The reason why there are requirements for the parameters of silicone twin structure surfactants is:

[0051] 1. Flash point 140-145℃: ensure safe use and avoid danger caused by excessive temperature during production or application;

[0052] 2. Dynamic viscosity 640-643mPa.s (25℃) / 248-252mPa.s (40℃): It indicates the fluidity of the surfactant and its stability at different temperatures, which is crucial to ensure the uniformity and workability of the coating;

[0053] 3. Density 1.079-1.082g / cm³: This parameter is important because it is related to the distribution and stability of the surfactant in the coating;

[0054] 4. Active matter content 100%: ensures the high efficiency and economy of the surfactant, and ensures that the performance of the coating will not be affected by fluctuations in the active agent content.

[0055] In steps S1-S3, during the process of adding aqueous liquid E51 epoxy resin, aqueous epoxy emulsion, polyethylene glycol 600, leveling agent, surfactant and pure water, the weight ratio of aqueous liquid E51 epoxy resin: aqueous epoxy emulsion: polyethylene glycol 600: leveling agent: surfactant: pure water is 30-40:40-55:1-2:0.5-0.7:0.3-05:12-17;

[0056] In step S1, the proportion of aqueous liquid E51 epoxy resin, polyethylene glycol 600, and pure water is selected, mainly considering the following points:

[0057] 1. Water-based liquid E51 epoxy resin (30-40%): As the basis of the primer, the content of epoxy resin is directly related to the coverage, adhesion and chemical resistance of the primer. This ratio range ensures sufficient epoxy resin to form a solid primer layer, while avoiding the problem of too thick a coating or too long drying time due to too high a resin content;

[0058] 2. Polyethylene glycol 600 (1-2%): As an emulsifier and wetting agent, polyethylene glycol 600 not only helps to effectively disperse the epoxy resin, but also helps to control the leveling and open time of the coating. Its addition amount ensures the optimization of the emulsification effect, while too much or too little may affect the uniformity and stability of the coating;

[0059] 3. Pure water (12-17%): Pure water is used as a solvent, and its content affects the overall viscosity and fluidity of the emulsion. This ratio range is designed to achieve optimal viscosity control, ensuring that the emulsion can be applied smoothly while maintaining sufficient solid content to form a tough coating.

[0060] In step S2, water-based epoxy emulsion (40-55%): The water-based epoxy emulsion here is a key component in the formulation, and its proportion directly affects the final performance of the coating. This proportion range is selected to ensure that the primer has excellent adhesion and water resistance while ensuring the flexibility and durability of the coating.

[0061] In step S3, leveling agent (0.5-0.7%) and surfactant (0.3-0.5%): The addition of leveling agent and surfactant is to optimize the appearance and performance of the coating. The leveling agent helps to eliminate bubbles and brush marks that may be generated during the coating process and make the coating surface smoother. The surfactant promotes the wetting and adhesion of the coating to the substrate and helps prevent the formation of surface defects. The selection of these proportions is aimed at achieving the best balance between leveling and wettability to ensure that the coating has good appearance quality and adhesion.

[0062] Compounding of S4 curing agent: according to the weight ratio, 10-20 parts of pure water and 5-10 parts of propylene glycol methyl ether are added into a stirrer, and the stirrer is started to perform the first stirring operation. After the first stirring operation is completed, 45-55 parts of type A curing agent and 25-35 parts of type B curing agent are added, and the stirrer is started to perform the second stirring operation. After the second stirring operation is completed, a two-component epoxy cross-linking promoting liquid is obtained;

[0063] The A-type curing agent is QR polymers R-RIT 1071 curing agent, and the B-type curing agent is BECKOPOX™ VEH 2188w / 55WA curing agent;

[0064] Pure water (10-20 parts): Pure water is mainly used as a diluent here to adapt to the needs of the spraying process. Selecting a range of 10-20 parts allows the fluidity of the coating to be adjusted to achieve ideal coating performance and drying time. The flexibility of this range also allows manufacturers to fine-tune according to specific application requirements (such as the specific type of spraying equipment or ambient temperature and humidity conditions).

[0065] Propylene glycol methyl ether (5-10 parts): Propylene glycol methyl ether can improve the fluidity and adhesion of the coating, while regulating the drying speed. The proportion range of 5-10 parts allows the open time and drying behavior of the coating to be optimized without sacrificing the performance of the coating film, ensuring that the coating film can be formed quickly and has good adhesion under wet-on-wet construction conditions.

[0066] Class A curing agent (45-55 parts): QR polymers R-RIT 1071 is selected as the Class A curing agent. This curing agent has a fast reaction speed and good initial surface hardness. The ratio of 45-55 parts is carefully calculated based on achieving a fast curing reaction to ensure that a scratch-resistant and chemical-resistant primer layer is quickly formed in wet-on-wet construction. This ratio range also allows the curing speed to be adjusted to meet the construction requirements under different environmental conditions.

[0067] Type B curing agent (25-35 parts): Type B curing agent is BECKOPOX™ VEH 2188w / 55WA. The reaction speed of this curing agent is relatively slow, which can extend the open time of the system, so that the coating has more time to level during the curing process and reduce defects. The ratio range of 25-35 parts provides sufficient flexibility to balance the curing speed and the final performance of the coating, ensuring that while providing good protection performance, it can also obtain excellent appearance.

[0068] Preparation of S5 water-based epoxy primer: According to the weight ratio, 30-35 parts of water-based epoxy primer base material and 10 parts of two-component epoxy cross-linking promoter are mixed evenly, and then 3-5 parts of pure water are added for dilution to obtain a water-based epoxy primer.

[0069] Waterborne Epoxy Primer Binder (30-35 parts): This ratio is to ensure that there is enough solid content in the primer to provide good coverage and adhesion. The range of 30-35 parts allows for proper adjustment to suit different application conditions and substrate types, ensuring the uniformity and gloss of the coating. Too much or too little primer binder may affect the final properties of the coating, such as drying time, hardness and durability.

[0070] Two-component epoxy cross-linking accelerator (10-12 parts): The function of the two-component epoxy cross-linking accelerator is to promote the curing reaction of the primer and provide hardness and chemical resistance of the final coating. The proportion of 10-12 parts is selected based on the need to balance rapid curing and avoid too fast hardening (which may cause defects on the coating surface). This amount ensures that enough cross-linking agent participates in the reaction while avoiding excessive viscosity or excessively brittle coating caused by excessive addition.

[0071] Pure water (3-5 parts): The purpose of adding 3-5 parts of pure water is to adjust the viscosity of the final coating to make it suitable for spraying application and to ensure uniform distribution and good leveling of the coating. The adjustment space in this range can be fine-tuned according to the actual application requirements and the characteristics of the spraying equipment to obtain the ideal coating thickness and surface smoothness. Too much water may cause the coating to be too thin, reducing coverage and durability; too little water may cause the coating to be too thick, affecting the drying speed and the final gloss.

[0072] The proportions of the ingredients in step S5 are designed to ensure that the waterborne epoxy primer has excellent application properties, including appropriate drying time, good adhesion, excellent hardness, and satisfactory gloss. These proportions are determined taking into account the process requirements in actual applications and the performance indicators of the final coating, ensuring the quality and long-term durability of the coating. In actual production, these proportions may need to be fine-tuned according to specific application conditions, substrate types, and desired coating properties.

[0073] Preferably, in step S1, the operating speed of the homogenizer is 2500-3000 revolutions per minute; and the operating time of the homogenizer is 15-20 minutes.

[0074] Homogenizer operating speed (2500-3000 revolutions per minute): Efficient emulsification: This speed range can effectively mix water-based liquid E51 epoxy resin, polyethylene glycol 600 and pure water into a uniform emulsion. The shear force generated by high-speed rotation is sufficient to break the interfacial tension between the raw materials, so that the water-based epoxy resin is dispersed into tiny particles, and polyethylene glycol 600 acts as an emulsifier to help stabilize these particles and prevent them from aggregating; Avoid excessive processing: Although higher speeds can further improve the uniformity of emulsification, excessive shear force can cause overheating or decomposition of the material. Therefore, 2500-3000 revolutions per minute is a balance point that can achieve good emulsification effects while avoiding possible negative effects.

[0075] Homogenizer running time (15-20 minutes): Full emulsification: This period of time is enough for the homogenizer to fully mix all ingredients at the above speed to ensure that the mixture achieves the required homogeneity and stability. If the time is too short, the entire emulsification process may not be completed, resulting in component separation or unstable emulsion, affecting the quality of the final product; Efficiency and energy consumption considerations: At the same time, this time range also takes into account production efficiency and energy consumption. Excessive running time not only reduces production efficiency, but also increases energy consumption and equipment wear. 15-20 minutes is the optimal choice between achieving good emulsification effect and controlling production costs.

[0076] The operating speed and time of the homogenizer in step S1 are selected to achieve the best emulsification effect, ensure that the prepared waterborne epoxy primer has good performance and stability, and take into account production efficiency and cost control.

[0077] Preferably, in step S2, the operating speed of the mixer is 500-550 revolutions per minute, and the operating stirring time of the mixer is 15-20 minutes.

[0078] Mixer operating speed (500-550 revolutions per minute): Effective mixing: This speed range provides sufficient power to mix the emulsion and water-based epoxy emulsion to ensure that the two are fully combined. This speed helps to form a uniform mixture and avoid excessive shear force caused by too high a speed, which will destroy the microstructure of the water-based epoxy emulsion and affect the final performance of the primer; Avoid air incorporation: Mixing at a lower speed helps reduce the possibility of air being introduced into the mixture. The incorporation of air can cause bubbles or holes in the primer, affecting the appearance and adhesion of the coating.

[0079] Mixer working stirring time (15-20 minutes): Giving 15-20 minutes of stirring time can ensure that the emulsion and water-based epoxy emulsion are fully mixed to form a stable emulsified system. This period of time is enough for all ingredients to be evenly distributed throughout the system, thereby ensuring that the primer has consistent quality.

[0080] The mixer parameters in step S2 are set to ensure that the emulsion and the water-based epoxy emulsion can be fully and evenly mixed while avoiding the introduction of too much air or unnecessary physical damage to the mixture, thereby laying a good foundation for preparing a high-gloss water-based epoxy primer.

[0081] Preferably, in step S3, the operating speed of the mixer is 800-1000 revolutions per minute, and the working stirring time of the mixer is 15-20 minutes.

[0082] Leveling agents and surfactants can only be fully dispersed under sufficient shear force and time to play their due role. Too low a rotation speed cannot form sufficient shear force in the base liquid, while too high a rotation speed may cause too many bubbles in the liquid, reduce the effect of the leveling agent and surfactant, and cause the liquid temperature to rise too quickly, affecting the performance of the product; therefore, in step S3, according to the properties of the leveling agent and surfactant, and the required performance of the water-based epoxy primer, a stirring speed of 800-1000 revolutions per minute and a stirring time of 15-20 minutes are determined.

[0083] Preferably, in step S4, in the first stirring operation, the operating speed of the mixer is 200-300 revolutions per minute, and the working time of the mixer is 5-10 minutes; in the second stirring operation, the operating speed of the mixer is 400-500 revolutions per minute, and the working time of the mixer is 20-25 minutes.

[0084] In the first stirring operation, add 10-20 parts of pure water and 5-10 parts of propylene glycol methyl ether into the mixer. At this time, the goal is to fully mix the two substances to achieve a uniform liquid state. Pure water and propylene glycol methyl ether are two polar substances that are easy to mix with each other. Therefore, the stirring speed does not need to be very high at this time. 200-300 revolutions per minute are enough to achieve a good mixing effect. At the same time, since the two substances are easy to mix, the stirring time does not need to be very long, and 5-10 minutes can achieve full mixing.

[0085] In the second mixing operation, 45-55 parts of Class A curing agent and 25-35 parts of Class B curing agent were added to the mixer. At this time, a more complex liquid system is faced. Among Class A curing agent and Class B curing agent, especially Class B curing agent, due to its slower reaction speed, a stronger stirring force is required to evenly disperse it in the liquid to ensure an effective chemical reaction. Therefore, the stirring speed at this time is increased to 400-500 revolutions per minute.

[0086] At the same time, since the curing agent needs to chemically react with the previous mixed liquid to generate the corresponding polymer in this step, this process requires a certain reaction time, so the stirring time of this step is set to 20-25 minutes to ensure the full reaction.

[0087] The setting of stirring speed and time should take into account the mixing needs of materials on the one hand and the needs of chemical reactions on the other hand. Only when both are met can a waterborne epoxy primer with excellent performance be prepared.

[0088] An application of a high-gloss waterborne epoxy primer that can be used for wet-on-wet, the application is applied to the high-gloss waterborne epoxy primer that can be used for wet-on-wet prepared as above, and the application process of the waterborne epoxy primer is as follows:

[0089] A1 spraying: spray water-based epoxy primer on the surface of the board;

[0090] A2 Drying: The waterborne epoxy primer sprayed on the surface of the board is treated by flash drying or baking. After the treatment, the operation of the waterborne epoxy primer on the surface of the board is completed.

[0091] In the flash-drying method for treating the waterborne epoxy primer sprayed on the surface of the board, the requirements are as follows: flash-dry at 70°C for 15-17 minutes or at 80°C for 10-12 minutes;

[0092] In the treatment of the waterborne epoxy primer sprayed on the surface of the board by the baking method, the requirements are as follows: baking at 70°C for 45-47 minutes or baking at 80°C for 30-33 minutes.

[0093] Compared with the prior art, the preparation method and application of the high gloss waterborne epoxy primer for wet-on-wet coating have the following beneficial effects:

[0094] 1. Improve glossiness: The present invention effectively improves the glossiness of the primer by optimizing the ratio of water-based epoxy resin and curing agent, and introducing specific leveling agents and surfactants. This high-gloss primer can significantly improve the aesthetics of the car surface and enhance consumers' overall impression of the quality of car painting.

[0095] 2. Enhanced flexibility and impact resistance: The present invention significantly enhances the flexibility and impact resistance of the primer by precisely controlling the addition ratio of each component, especially the polyethylene glycol and silicone twin structure surfactant added in the emulsification and mixing steps, thus meeting the needs of automobiles in complex use environments.

[0096] 3. Reduce VOC content: The present invention effectively reduces the VOC content of the primer by using water-based epoxy resin and emulsion, and optimizing the type and amount of organic solvents. This not only reduces environmental pollution, but also improves safety during production and use, and complies with current environmental regulations and market trends.

[0097] 4. Shorten the drying time: The present invention takes into account the optimization of the drying time during the preparation process, especially in the compounding step. By adjusting the type and proportion of the curing agent and reasonably controlling the amount of added water and organic solvent, the primer can be dried in a relatively short time, thereby improving production efficiency.

[0098] 5. Wet-on-wet application: During the preparation process, specific materials and proportions are selected, such as E51 epoxy resin, polyethylene glycol 600, PZ3961-1 water-based epoxy emulsion, BYK3481 leveling agent and silicone twin structure surfactant. These ingredients are carefully selected and proportioned to provide good emulsification properties, stirring uniformity and final coating performance, especially the combination of water-based epoxy resin and water-based epoxy emulsion, which ensures the stability of the primer in the water-based system and good adhesion, which is very critical for wet-on-wet application. DETAILED DESCRIPTION

[0099] The following are specific embodiments of the present invention, which further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments. Specific embodiment one:

[0101] A method for preparing a high-gloss waterborne epoxy primer that can be used for wet-on-wet coating, the method comprising the following steps:

[0102] S1 emulsification: add aqueous liquid E51 epoxy resin, polyethylene glycol 600 and pure water into the homogenizer, start the homogenizer for emulsification, and obtain an emulsified liquid after the emulsification operation is completed; the operating speed of the homogenizer is 2500-3000 revolutions per minute; the operating time of the homogenizer is 15-20 minutes.

[0103] The specific parameters of the water-based liquid E51 epoxy resin are as follows: at 25 degrees Celsius, the viscosity of the water-based liquid E51 epoxy resin is 5500-10000cps; the epoxy value of the water-based liquid E51 epoxy resin is 0.4Eq / 100g, and the epoxy equivalent of the water-based liquid E51 epoxy resin is 250; the chromaticity of the water-based liquid E51 epoxy resin measured by the Gardner method is ≤2;

[0104] The specific parameters of polyethylene glycol 600 are as follows: the hydroxyl value of polyethylene glycol 600 is 170-208 mgKOH / g; the freezing point of polyethylene glycol 600 is 25°C; the water content of polyethylene glycol 600 is ≤1%; the pH value of polyethylene glycol 600 in a 1% aqueous solution is 5.0-7.0;

[0105] Compounding of S2 resin: add the emulsion and water-based epoxy emulsion into a mixer and mix them. After mixing evenly, a mixed liquid is obtained. The water-based epoxy emulsion is PZ3961-1 water-based epoxy emulsion. The working speed of the mixer is 500-550 revolutions per minute, and the working stirring time of the mixer is 15-20 minutes.

[0106] S3 mixing: adding the leveling agent and the surfactant into the mixed liquid, increasing the speed of the mixer to carry out the mixing operation, after the mixing operation is completed, the waterborne epoxy primer base material is obtained; taking out the waterborne epoxy primer base material for standby use; the working speed of the mixer is 800-1000 revolutions per minute, and the working mixing time of the mixer is 15-20 minutes.

[0107] The leveling agent is BYK3481 type leveling agent; the surfactant is a silicone twin structure surfactant, and the specific parameters of the silicone twin structure surfactant are as follows: the flash point of the silicone twin structure surfactant is 144°C; at 25°C, the dynamic viscosity of the silicone twin structure surfactant is 641mPa.s; at 40°C, the dynamic viscosity of the silicone twin structure surfactant is 251mPa.s; the density of the silicone twin structure surfactant is 1.081g / cm³; the active matter content of the silicone twin structure surfactant is 100%;

[0108] In steps S1-S3, during the process of adding aqueous liquid E51 epoxy resin, aqueous epoxy emulsion, polyethylene glycol 600, leveling agent, surfactant and pure water, the weight ratio of aqueous liquid E51 epoxy resin: aqueous epoxy emulsion: polyethylene glycol 600: leveling agent: surfactant: pure water is 35:48:1:0.6:0.4-:15;

[0109] Compounding of S4 curing agent: according to the weight ratio, 15 parts of pure water and 5 parts of propylene glycol methyl ether are added into a stirrer, and the stirrer is started to perform the first stirring operation. After the first stirring operation is completed, 45 parts of type A curing agent and 35 parts of type B curing agent are added, and the stirrer is started to perform the second stirring operation. After the second stirring operation is completed, a two-component epoxy cross-linking promoting liquid is obtained;

[0110] The A-type curing agent is QR polymers R-RIT 1071 curing agent, and the B-type curing agent is BECKOPOX™ VEH 2188w / 55WA curing agent;

[0111] In the first mixing operation, the mixer operates at a speed of 200-300 revolutions per minute, and the mixer operates for 5-10 minutes;

[0112] In the second mixing operation, the operating speed of the mixer is 400-500 revolutions per minute, and the working time of the mixer is 20-25 minutes.

[0113] Preparation of S5 water-based epoxy primer: According to the weight ratio, 30 parts of water-based epoxy primer base material and 10 parts of two-component epoxy cross-linking promoter are mixed evenly, and then 4 parts of pure water are added for dilution to obtain a water-based epoxy primer. Specific embodiment 2:

[0115] A method for preparing a high-gloss waterborne epoxy primer that can be used for wet-on-wet coating, the method comprising the following steps:

[0116] S1 emulsification: add aqueous liquid E51 epoxy resin, polyethylene glycol 600 and pure water into the homogenizer, start the homogenizer for emulsification, and obtain an emulsified liquid after the emulsification operation is completed; the operating speed of the homogenizer is 2500-3000 revolutions per minute; the operating time of the homogenizer is 15-20 minutes.

[0117] The specific parameters of the water-based liquid E51 epoxy resin are as follows: at 25 degrees Celsius, the viscosity of the water-based liquid E51 epoxy resin is 5500-10000cps; the epoxy value of the water-based liquid E51 epoxy resin is 0.4Eq / 100g, and the epoxy equivalent of the water-based liquid E51 epoxy resin is 250; the chromaticity of the water-based liquid E51 epoxy resin measured by the Gardner method is ≤2;

[0118] The specific parameters of polyethylene glycol 600 are as follows: the hydroxyl value of polyethylene glycol 600 is 170-208 mgKOH / g; the freezing point of polyethylene glycol 600 is 25°C; the water content of polyethylene glycol 600 is ≤1%; the pH value of polyethylene glycol 600 in a 1% aqueous solution is 5.0-7.0;

[0119] Compounding of S2 resin: add the emulsion and water-based epoxy emulsion into a mixer and mix them. After mixing evenly, a mixed liquid is obtained. The water-based epoxy emulsion is PZ3961-1 water-based epoxy emulsion. The working speed of the mixer is 500-550 revolutions per minute, and the working stirring time of the mixer is 15-20 minutes.

[0120] S3 mixing: adding the leveling agent and the surfactant into the mixed liquid, increasing the speed of the mixer to carry out the mixing operation, after the mixing operation is completed, the waterborne epoxy primer base material is obtained; taking out the waterborne epoxy primer base material for standby use; the working speed of the mixer is 800-1000 revolutions per minute, and the working mixing time of the mixer is 15-20 minutes.

[0121] The leveling agent is BYK3481 type leveling agent; the surfactant is a silicone twin structure surfactant, and the specific parameters of the silicone twin structure surfactant are as follows: the flash point of the silicone twin structure surfactant is 144°C; at 25°C, the dynamic viscosity of the silicone twin structure surfactant is 641mPa.s; at 40°C, the dynamic viscosity of the silicone twin structure surfactant is 251mPa.s; the density of the silicone twin structure surfactant is 1.081g / cm³; the active matter content of the silicone twin structure surfactant is 100%;

[0122] In steps S1-S3, during the process of adding aqueous liquid E51 epoxy resin, aqueous epoxy emulsion, polyethylene glycol 600, leveling agent, surfactant and pure water, the weight ratio of aqueous liquid E51 epoxy resin: aqueous epoxy emulsion: polyethylene glycol 600: leveling agent: surfactant: pure water is 31.5:53:1:0.7:0.3-:13.5;

[0123] Compounding of S4 curing agent: according to the weight ratio, 10 parts of pure water and 10 parts of propylene glycol methyl ether are added into a stirrer, and the stirrer is started to perform the first stirring operation. After the first stirring operation is completed, 50 parts of type A curing agent and 30 parts of type B curing agent are added, and the stirrer is started to perform the second stirring operation. After the second stirring operation is completed, a two-component epoxy cross-linking promoting liquid is obtained;

[0124] The A-type curing agent is QR polymers R-RIT 1071 curing agent, and the B-type curing agent is BECKOPOX™ VEH 2188w / 55WA curing agent;

[0125] In the first mixing operation, the mixer operates at a speed of 200-300 revolutions per minute, and the mixer operates for 5-10 minutes;

[0126] In the second mixing operation, the operating speed of the mixer is 400-500 revolutions per minute, and the working time of the mixer is 20-25 minutes.

[0127] Preparation of S5 water-based epoxy primer: According to the weight ratio, 30 parts of water-based epoxy primer base material and 10 parts of two-component epoxy cross-linking promoter are mixed evenly, and then 3 parts of pure water are added for dilution to obtain a water-based epoxy primer. Specific embodiment three:

[0129] A method for preparing a high-gloss waterborne epoxy primer that can be used for wet-on-wet coating, the method comprising the following steps:

[0130] S1 emulsification: add aqueous liquid E51 epoxy resin, polyethylene glycol 600 and pure water into the homogenizer, start the homogenizer for emulsification, and obtain an emulsified liquid after the emulsification operation is completed; the operating speed of the homogenizer is 2500-3000 revolutions per minute; the operating time of the homogenizer is 15-20 minutes.

[0131] The specific parameters of the water-based liquid E51 epoxy resin are as follows: at 25 degrees Celsius, the viscosity of the water-based liquid E51 epoxy resin is 5500-10000cps; the epoxy value of the water-based liquid E51 epoxy resin is 0.4Eq / 100g, and the epoxy equivalent of the water-based liquid E51 epoxy resin is 250; the chromaticity of the water-based liquid E51 epoxy resin measured by the Gardner method is ≤2;

[0132] The specific parameters of polyethylene glycol 600 are as follows: the hydroxyl value of polyethylene glycol 600 is 170-208 mgKOH / g; the freezing point of polyethylene glycol 600 is 25°C; the water content of polyethylene glycol 600 is ≤1%; the pH value of polyethylene glycol 600 in a 1% aqueous solution is 5.0-7.0;

[0133] Compounding of S2 resin: add the emulsion and water-based epoxy emulsion into a mixer and mix them. After mixing evenly, a mixed liquid is obtained. The water-based epoxy emulsion is PZ3961-1 water-based epoxy emulsion. The working speed of the mixer is 500-550 revolutions per minute, and the working stirring time of the mixer is 15-20 minutes.

[0134] S3 mixing: adding the leveling agent and the surfactant into the mixed liquid, increasing the speed of the mixer to carry out the mixing operation, after the mixing operation is completed, the waterborne epoxy primer base material is obtained; taking out the waterborne epoxy primer base material for standby use; the working speed of the mixer is 800-1000 revolutions per minute, and the working mixing time of the mixer is 15-20 minutes.

[0135] The leveling agent is BYK3481 type leveling agent; the surfactant is a silicone twin structure surfactant, and the specific parameters of the silicone twin structure surfactant are as follows: the flash point of the silicone twin structure surfactant is 144°C; at 25°C, the dynamic viscosity of the silicone twin structure surfactant is 641mPa.s; at 40°C, the dynamic viscosity of the silicone twin structure surfactant is 251mPa.s; the density of the silicone twin structure surfactant is 1.081g / cm³; the active matter content of the silicone twin structure surfactant is 100%;

[0136] In steps S1-S3, during the process of adding aqueous liquid E51 epoxy resin, aqueous epoxy emulsion, polyethylene glycol 600, leveling agent, surfactant and pure water, the weight ratio of aqueous liquid E51 epoxy resin: aqueous epoxy emulsion: polyethylene glycol 600: leveling agent: surfactant: pure water is 38.5:42:2:0.5:0.5:16.5;

[0137] Compounding of S4 curing agent: according to the weight ratio, 12 parts of pure water and 8 parts of propylene glycol methyl ether are added into a stirrer, and the stirrer is started to perform the first stirring operation. After the first stirring operation is completed, 55 parts of type A curing agent and 25 parts of type B curing agent are added, and the stirrer is started to perform the second stirring operation. After the second stirring operation is completed, a two-component epoxy cross-linking promoting liquid is obtained;

[0138] The A-type curing agent is QR polymers R-RIT 1071 curing agent, and the B-type curing agent is BECKOPOX™ VEH 2188w / 55WA curing agent;

[0139] In the first mixing operation, the mixer operates at a speed of 200-300 revolutions per minute, and the mixer operates for 5-10 minutes;

[0140] In the second mixing operation, the operating speed of the mixer is 400-500 revolutions per minute, and the working time of the mixer is 20-25 minutes.

[0141] Preparation of S5 water-based epoxy primer: According to the weight ratio, 35 parts of water-based epoxy primer base material and 10 parts of two-component epoxy cross-linking promoter are mixed evenly, and then 5 parts of pure water are added for dilution to obtain a water-based epoxy primer.

[0142] The proportions of the added materials in the specific embodiments 1, 2 and 3 are as follows:

[0143] The mixing ratios are:

[0144] Example 1: Waterborne epoxy primer base material: two-component epoxy cross-linking promoter: pure water = 3:1:0.4,

[0145] Example 2: Waterborne epoxy primer base material: two-component epoxy cross-linking promoter: pure water = 3:1:0.3,

[0146] Example 3: Water-based epoxy primer base material: two-component epoxy cross-linking promoter liquid: pure water = 3.5:1:0.5. Specific embodiment four:

[0148] The waterborne epoxy primers prepared in Specific Embodiment 1, Specific Embodiment 2 and Specific Embodiment 3 are respectively applied, and the specific steps are as follows:

[0149] A1 spraying: spray water-based epoxy primer on the surface of the board;

[0150] A2 Drying: The waterborne epoxy primer sprayed on the surface of the board is treated by flash drying or baking. After the treatment, the waterborne epoxy primer is applied on the surface of the board.

[0151] When the waterborne epoxy primer sprayed on the surface of the board is treated by flash drying method; after flash drying at 70℃ for 15 minutes or at 80℃ for 10 minutes;

[0152] When the waterborne epoxy primer sprayed on the surface of the plate is treated by a baking method, the plate is baked at 70° C. for 45 minutes or at 80° C. for 30 minutes.

[0153] After the waterborne epoxy primer prepared in Specific Embodiment 1, Specific Embodiment 2 and Specific Embodiment 3 was applied to the surface of the plate, glossiness detection and performance test were performed respectively, and the specific results are as follows:

[0154] Gloss meter test:

[0155] The performance test results are as follows:

[0156] Test conclusion:

[0157] The invention discloses a method for preparing a high-gloss waterborne epoxy primer that can be used for wet-on-wet coating. Compared with the conventional primer technology, the primer produced by the method has not only high gloss and strong adhesion, but also good hardness, strong flexibility and impact resistance. At the same time, due to the use of waterborne epoxy resin, the emission of harmful volatiles can be effectively avoided, thereby achieving a dual improvement in environmental protection and product performance.

[0158] From a technical perspective, the innovation lies in adjusting and controlling the proportion of each raw material added, as well as optimizing the production process. First, by strictly controlling the quality parameters of the raw materials, including the properties of various raw materials such as water-based liquid E51 epoxy resin, polyethylene glycol 600, PZ3961-1 water-based epoxy emulsion, BYK3481 leveling agent and silicone twin structure surfactant, in addition, by selecting suitable curing agents, such as QR polymers R-RIT 1071 curing agent and BECKOPOX™ VEH2188w / 55WA curing agent, the hardness and flexibility of the primer are effectively improved. In the process of adding each raw material, it is added according to the preset proportion, which ensures the performance while controlling the production cost and improving the market competitiveness of the product.

[0159] In terms of product performance, the primer has an excellent surface gloss of 95-97; according to the 2mm cross-cut test results of GB / T 9286-1998, the adhesion reached level 0; the hardness reached level H in accordance with the target GB / T 6739-2006 standard, indicating that the primer has good wear resistance; according to the GB / T 1731-1993 standard, the flexibility test showed no damage such as reticulation, cracks and peeling, indicating that the primer can well cooperate with the shape changes of the material and resist the stress changes of the material; in the impact resistance test, the paint film is good without cracks or wrinkles.

[0160] In general, the present invention gives full play to the performance of raw materials and successfully develops an environmentally friendly primer with excellent performance through sophisticated process flow and control means. This has great practical significance and market value for optimizing product quality, improving product competitiveness, and promoting the transformation of harmful chemical products into environmentally friendly products.

[0161] The specific embodiments described herein are merely examples of the spirit of the present invention. A person skilled in the art of the present invention may make various modifications or supplements to the specific embodiments described or replace them in a similar manner, but will not deviate from the spirit of the present invention or exceed the defined scope. Although the present invention is described and described in detail in the foregoing description, such descriptions and descriptions are considered to be illustrative or exemplary rather than restrictive. It should be understood that within the scope of the following claims, changes and modifications may be made by a person of ordinary skill. Specifically, the present invention encompasses additional embodiments having any combination of features from the above-mentioned different embodiments. With respect to the use of the expression "generally" or "substantially", this patent application should be understood to disclose that these features and values ​​are also fully satisfied, i.e., there is no aforementioned characterization as "generally" or "substantially".

Claims

1. A method for preparing a high gloss waterborne epoxy primer that can be used for wet-on-wet applications. It is characterized in that The preparation method comprises the following steps S1 to S5: Step S1: emulsification: adding aqueous liquid E51 epoxy resin, polyethylene glycol 600 and pure water into a homogenizer, starting the homogenizer to perform emulsification, and obtaining an emulsified liquid after the emulsification operation is completed; The specific parameter requirements of the water-based liquid E51 epoxy resin are as follows: at 25 degrees Celsius, the viscosity of the water-based liquid E51 epoxy resin is 5500-10000cps; the epoxy value of the water-based liquid E51 epoxy resin is 0.4-0.45Eq / 100g, and the epoxy equivalent of the water-based liquid E51 epoxy resin is 250-260; the chromaticity of the water-based liquid E51 epoxy resin measured by the Gardner method is ≤2; The specific parameter requirements of polyethylene glycol 600 are as follows: the hydroxyl value of polyethylene glycol 600 is 170-208 mgKOH / g; the freezing point of polyethylene glycol 600 is 20-25°C; the moisture content of polyethylene glycol 600 is ≤1%; the pH value of polyethylene glycol 600 in 1% aqueous solution is 5.0-7.0; Step S2: Compounding of resin: adding the emulsion and the water-based epoxy emulsion into a mixer, mixing them evenly to obtain a mixed liquid; the water-based epoxy emulsion is PZ3961-1 water-based epoxy emulsion; Step S3: Mixing: adding the leveling agent and the surfactant to the mixed liquid, increasing the speed of the stirrer to perform a stirring operation, and after the stirring operation is completed, a waterborne epoxy primer base material is obtained; taking out the waterborne epoxy primer base material for standby use; The leveling agent is BYK3481 type leveling agent; the surfactant is a silicone twin structure surfactant, and the specific parameter requirements of the silicone twin structure surfactant are as follows: the flash point of the silicone twin structure surfactant is 140-145℃; at 25℃, the dynamic viscosity of the silicone twin structure surfactant is 640-643mPa.s; at 40℃, the dynamic viscosity of the silicone twin structure surfactant is 248-252mPa.s; the density of the silicone twin structure surfactant is 1.079-1.082g / cm³; the active matter content of the silicone twin structure surfactant is 100%; In step S1 to step S3, in the process of adding aqueous liquid E51 epoxy resin, aqueous epoxy emulsion, polyethylene glycol 600, leveling agent, surfactant and pure water, the weight ratio of aqueous liquid E51 epoxy resin: aqueous epoxy emulsion: polyethylene glycol 600: leveling agent: surfactant: pure water is 30-40:40-55:1-2:0.5-0.7:0.3-05:12-17; Step S4: Compounding of curing agent: according to the weight ratio, 10-20 parts of pure water and 5-10 parts of propylene glycol methyl ether are added into a stirrer, and the stirrer is started to perform the first stirring operation. After the first stirring operation is completed, 45-55 parts of Class A curing agent and 25-35 parts of Class B curing agent are added, and the stirrer is started to perform the second stirring operation. After the second stirring operation is completed, a two-component epoxy cross-linking promoting liquid is obtained; The A-type curing agent is QR polymers R-RIT 1071 curing agent, and the B-type curing agent is BECKOPOX™ VEH2188w / 55WA curing agent; Step S5: Preparation of waterborne epoxy primer: According to the weight ratio, 30-35 parts of waterborne epoxy primer base material and 10-12 parts of two-component epoxy cross-linking promoter are mixed evenly, and then 3-5 parts of pure water are added for dilution to obtain a waterborne epoxy primer.

2. The method for preparing a high gloss waterborne epoxy primer that can be used for wet-on-wet coating as claimed in claim 1, It is characterized in that In step S1, the operating speed of the homogenizer is 2500-3000 revolutions per minute; the operating time of the homogenizer is 15-20 minutes.

3. The method for preparing a high gloss waterborne epoxy primer that can be used for wet-on-wet coating as claimed in claim 1, It is characterized in that In step S2, the operating speed of the mixer is 500-550 revolutions per minute, and the operating mixing time of the mixer is 15-20 minutes.

4. The method for preparing a high gloss waterborne epoxy primer that can be used for wet-on-wet coating as claimed in claim 1, It is characterized in that In step S3, the operating speed of the mixer is 800-1000 revolutions per minute, and the operating mixing time of the mixer is 15-20 minutes.

5. The method for preparing a high gloss waterborne epoxy primer that can be used for wet-on-wet coating as claimed in claim 1, It is characterized in that In step S4, in the first stirring operation, the stirring machine operates at a speed of 200-300 revolutions per minute, and the stirring machine operates for 5-10 minutes; In the second mixing operation, the operating speed of the mixer is 400-500 revolutions per minute, and the working time of the mixer is 20-25 minutes.

6. An application of a high-gloss waterborne epoxy primer that can be used for wet-on-wet, the application being the high-gloss waterborne epoxy primer that can be used for wet-on-wet prepared by the preparation method according to any one of claims 1 to 5, It is characterized in that The application process of waterborne epoxy primer is as follows: Spraying: Spray water-based epoxy primer on the surface of the board; Drying: The waterborne epoxy primer sprayed on the surface of the board is treated by flash drying or baking. After the treatment, the waterborne epoxy primer is applied on the surface of the board; In the flash-drying method for treating the waterborne epoxy primer sprayed on the surface of the board, the requirements are as follows: flash-dry at 70°C for 15-17 minutes or at 80°C for 10-12 minutes; In the treatment of the waterborne epoxy primer sprayed on the surface of the board by the baking method, the requirements are as follows: baking at 70°C for 40-45 minutes or baking at 80°C for 25-30 minutes.

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