High-performance universal waterborne epoxy primer and preparation method thereof

Abstract

The invention discloses a high-performance universal waterborne epoxy primer and a preparation method thereof.The high-performance universal waterborne epoxy primer is composed of a component A and a component B. The weight ratio of the component A to the component B is (10-15): 1, the component A is prepared from, by weight, 15-20 parts of distilled water, 0.1-0.5 part of anti-settling auxiliary, 0.5-1 part of dispersing agent, 0.4-1 part of defoaming agent, 5-15 parts of tinting pigment, 30-45 parts of extender pigment, 3-8 parts of anti-rust pigment and 35-45 parts of high-performance epoxy emulsion, and the component B is prepared from, by weight, 20-30 parts of water. 1-2 parts of a coalescing agent, 0.2-0.5 part of a flatting agent, 0.5-1.5 parts of an adhesion promoter and 0.1-0.5 part of a thickening agent; and the component B comprises the following components in parts by weight: 10-20 parts of distilled water, 60-80 parts of water-soluble amine resin, 5-10 parts of a coalescing agent and 10-15 parts of an anti-flash-rust agent. According to the invention, excellent anti-corrosion and connection functions are provided on various metal substrates at the same time, the paint is especially suitable for construction operation in a complex substrate environment in the field of general industrial paint, the construction efficiency is greatly improved, and the paint has a wide application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of general industrial paint coatings, and specifically relates to a high-performance general-purpose waterborne epoxy primer and a preparation method thereof. Background Art

[0002] Epoxy primers used in the field of general industrial paint coatings usually include epoxy bonding paints and epoxy anti-corrosion paints. When it is necessary to construct a stable paint layer system on the surfaces of different materials, due to the different surface energies and roughnesses of different material surfaces, the epoxy bonding paint can closely adhere to various substrates by virtue of its excellent adhesion, effectively shortening the distance between the paint layer and the substrate, and providing a reliable adhesion basis for subsequent coatings. When facing complex and changeable industrial production environments such as humidity and salt spray, the epoxy anti-corrosion paint can form a dense and tough protective film on the metal surface, blocking the intrusion of external corrosive media, slowing down the rusting process of the metal, greatly extending the service life of the equipment, and reducing the high costs brought about by frequent equipment replacement due to corrosion. Due to different focuses, waterborne epoxy bonding paints and waterborne epoxy anti-corrosion paints use emulsions with different performance characteristics. The emulsion resin of the waterborne epoxy bonding paint focuses on improving flexibility and adhesion. The emulsion resin of the waterborne epoxy anti-corrosion paint focuses on increasing the crosslinking density and stronger hydrophobicity. Therefore, the waterborne epoxy bonding paint has relatively poor shielding performance against media, especially the shielding effect against water, and relatively insufficient anti-corrosion performance. And because the waterborne epoxy anti-corrosion paint emphasizes hydrophobicity and shielding performance, the selection of resin tends to result in the rigidity and brittleness of the final coating film, which has an adverse effect on the adhesion on light metals. However, in general industrial paint coatings, there are often painting interfaces where multiple metal materials coexist. For example, the structure of the rear trunk of a gas transport vehicle is of this type, which includes a vehicle body mainly made of hot-rolled sandblasted steel plates, a box body made of cold-rolled steel plates, stainless steel valves, and some aluminum structural parts. Facing this situation, using only epoxy bonding paint or epoxy anti-corrosion paint alone is not the best construction solution. A general-purpose epoxy primer that can both play a connecting role and an anti-corrosion role is needed to better handle such problems. Summary of the Invention

[0003] The purpose of the present invention is to provide a high-performance general-purpose waterborne epoxy primer and a preparation method thereof, so as to achieve the function of simultaneously playing a connecting and anti-corrosion role on multiple metal materials with only one kind of paint, which will greatly improve the on-site construction efficiency and has a wide application prospect in the general industrial paint market.

[0004] To achieve the above purpose, the present invention is realized through the following technical solutions: A high-performance general-purpose waterborne epoxy primer is composed of component A and component B with a weight ratio of (10 - 15):1. The specific compositions of component A and component B are as follows:

[0005] The component A, by weight, comprises: 15 - 20 parts of distilled water, 0.1 - 0.5 part of anti - settling agent, 0.5 - 1 part of dispersant, 0.4 - 1 part of defoamer, 5 - 15 parts of coloring pigment, 30 - 45 parts of extender pigment, 3 - 8 parts of anti - rust pigment, 35 - 45 parts of high - performance epoxy emulsion, 1 - 2 parts of film - forming aid, 0.2 - 0.5 part of leveling agent, 0.5 - 1.5 parts of adhesion promoter, 0.1 - 0.5 part of thickener;

[0006] The component B, by weight, comprises: 10 - 20 parts of distilled water, 60 - 80 parts of water - soluble amine resin, 5 - 10 parts of film - forming aid, 10 - 15 parts of anti - flash rust agent;

[0007] The high - performance epoxy emulsion is a new type of water - borne epoxy emulsion made by special modification of bisphenol A epoxy emulsion.

[0008] Among them, 0 - 5% of E12 resin and 5% - 20% of functional resins such as PPGDGE are used to modify ordinary E20 epoxy emulsion to synthesize a new type of high - performance epoxy emulsion;

[0009] Specifically as follows: The functional resin and E20 resin first carry out grafting reaction with non - ionic emulsifier. During this process, the addition of PPGDGE can balance the influence of E12 resin on the reaction kettle temperature; during the water titration to the phase - inversion process, relying on the epoxy groups and high - freedom characteristics it has, PPGDGE can also promote the stability of the emulsification process, making the emulsion form more firm;

[0010] The new emulsion improves the flexibility and adhesion of ordinary E20 epoxy emulsion and endows it with certain low - temperature film - forming property.

[0011] In addition, E12 endows E20 resin with better flexibility and hardening speed: Since E12 epoxy resin has a lower cross - linking density than E20 resin, the ability of the molecular chain to bend and stretch freely is stronger. When the resin is subjected to external force, it is easier to deform, showing lower brittleness and better flexibility; in addition, the epoxy groups in E12 epoxy resin have higher reactivity and can react quickly with the curing agent, shortening the time for the coating film to change from liquid state to solid state and improving the hardening speed; however, too much E12 resin will lead to insufficient cross - linking density of the whole coating film, even seriously affecting the shielding property and anti - corrosion property of the coating film. Therefore, the addition amount of E12 should not be too much.

[0012] PPGDGE is an excellent flexible group that can reduce the film-forming temperature of epoxy emulsion; the carbon-carbon bonds and carbon-oxygen bonds in the PPGDGE chain segment have a relatively high degree of internal rotation freedom, enabling the molecular chain to bend and stretch more flexibly. Its flexible chain segment can act as a "bridge" or "spacer" between the molecular chains of the material, reducing the intermolecular forces between the material molecular chains, increasing the movement ability of the molecular chains, and thus improving the flexibility of the material; the increase in flexibility will offset the growth of part of the internal stress during the drying process of the coating film, thereby improving the adhesion of the coating film; the addition of PPGDGE can also reduce the Tg of the epoxy emulsion, thereby reducing the minimum film-forming temperature of the coating, making it have better low-temperature film-forming performance; however, excessive addition of PPGDGE will also cause the film strength to decrease and the crosslinking density to decrease, affecting the anti-corrosion performance of the coating. Therefore, a reasonable addition amount can bring out the best effect of PPGDGE.

[0013] Preferably, the anti-settling agent is lithium-modified montmorillonite powder;

[0014] Usually, sodium-modified montmorillonite powder is further reacted with lithium salts (such as lithium chloride, lithium carbonate, etc.) to replace sodium ions with lithium ions, thereby obtaining lithium-modified montmorillonite powder. Lithium-modified montmorillonite powder has good suspension and dispersion properties, can prevent the precipitation of particles such as pigments, and ensure the uniformity and stability of the product. Sodium-modified montmorillonite powder is the raw material of lithium-modified montmorillonite powder. Through sodium modification, the hydrophilicity and swelling property of montmorillonite powder can be improved, and its dispersion performance in water can be improved. The main principle is to use sodium salts (such as sodium carbonate, sodium sulfate, etc.) as sodium agents to replace calcium, magnesium and other cations in montmorillonite powder with sodium ions.

[0015] Preferably, the dispersant is a polymer non-ionic wetting dispersant; the defoamer is a water-soluble silicone and non-silicone defoamer used alone or in combination.

[0016] Preferably, the coloring pigment is one or more of titanium dioxide, iron red, and carbon black. The titanium dioxide is rutile titanium dioxide produced by the hydrochloric acid method.

[0017] Preferably, the extender pigment is one or more of flaky pure talc powder (ash content ≈ 95%), precipitated barium sulfate, mica powder, and feldspar powder. For the selection of flaky fillers, on the one hand, consider its influence on the anti-corrosion performance; on the other hand, also consider its influence on the internal stress of the coating film.

[0018] First of all, flaky fillers have a unique flaky structure. During the film-forming process of the coating, they overlap and arrange with each other to form a multi-layer shielding structure. This structure can effectively block the penetration of external moisture, oxygen, and corrosive media, etc. to the substrate, extend the path of these substances to reach the substrate, and thus slow down the corrosion rate of the substrate.

[0019] Secondly, the flaky filler has a large aspect ratio. During the film-forming process of the coating, it can be oriented in a direction parallel to the substrate and overlap with each other like "scales" to form a series of barriers. This can prevent the concentration of internal stress generated by volume shrinkage during the drying and curing process of the coating, disperse the internal stress between each "scale", and thus reduce the overall internal stress.

[0020] Finally, the flaky filler can also play a role in deformation coordination within the coating film. When the coating is deformed due to external factors (such as temperature changes, substrate expansion and contraction, etc.), it can adapt to this deformation through small displacements and orientation changes, reducing the internal stress generated by inconsistent deformation.

[0021] Preferably, the rust-inhibiting pigment is a type of aluminum tripolyphosphate rust-inhibiting pigment; the film-forming aid is a propylene glycol ether solvent; the leveling agent is a water-soluble silicone and non-silicone leveling agent used alone or in combination.

[0022] Preferably, the adhesion promoter is an epoxy silane oligomer coupling agent.

[0023] The epoxy silane oligomer coupling agent is an important adhesion promoter. It contains two different types of groups inside. One end can chemically react with hydroxyl groups, epoxy groups, etc. in the epoxy resin molecule to form a chemical bond; the other end can react with groups such as hydroxyl groups on the substrate surface or be tightly bound to the substrate surface through physical adsorption. In this way, the epoxy resin and the substrate are firmly connected together, significantly improving the adhesion of the epoxy paint to various substrates, making the coating not easy to fall off, and thus extending the service life of the paint film.

[0024] Preferably, the thickener is a non-ionic polyurethane thickener; the anti-flooding and anti-rust aid is a complexing anti-flooding and anti-rust aid.

[0025] Preferably, the water-soluble resin is a hydrophilic amine resin adduct having one or more of phthalenediamine monomer, tetraethylenediamine monomer, and IPDA.

[0026] A preparation method of a high-performance general-purpose waterborne epoxy primer includes the following steps:

[0027] Step 1: Grinding and dispersion stage: Add distilled water and anti-settling agent into a stirrer, stir at high speed for 15 minutes to ensure the full activation of the anti-settling agent, then successively add dispersant, defoamer, coloring pigment, extender pigment, and anti-rust pigment, and grind them with a sand mill for 30 minutes, controlling the fineness below 35 μm; Blending and mixing stage: After filtration, add high-performance epoxy emulsion, mix the slurry and the emulsion evenly, adjust the stirring speed (500 - 1000 rpm), successively add film-forming aid, defoamer, leveling agent, and adhesion promoter. After all are added, stir for another 5 - 10 minutes to make them fully mixed. Add thickening aid, increase the stirring speed to 1000 - 1500 rpm, and continuously stir for 10 - 15 minutes. The temperature throughout the process does not exceed 60°C. Filter and package with a 150-mesh screen to obtain Component A;

[0028] Step 2: Add distilled water into a stirrer, start stirring, and successively add water-soluble amine resin, film-forming aid, and anti-flash rust agent, stir at low speed for 10 - 15 minutes until uniform to obtain Component B;

[0029] Step 3: Mix Component A and Component B according to the weight ratio, add water for dilution, stir evenly, and then it can be applied.

[0030] Advantages of the present invention: By using high-performance waterborne epoxy emulsion and preferably using flaky talc powder as the main filler, the present invention combines the technical characteristics of epoxy connecting paint and epoxy anti-corrosion paint, realizes the functions of good connectivity and anti-corrosion on various metal materials, and meets the construction requirements under low-temperature conditions. It significantly improves the construction efficiency and has a wide application prospect in the field of general industrial paints. Description of the Drawings

[0031] The present invention will be described in detail below in conjunction with the drawings and specific embodiments;

[0032] Figure 1 It is a schematic diagram of the stress change during the drying process of the coating film;

[0033] Figure 2 It is a tensile curve showing the influence of resin type on flexibility;

[0034] Figure 3 It is the test result of the influence of resin type on mechanical properties;

[0035] Figure 4 It is the test result of the influence of resin type on the minimum film-forming temperature;

[0036] Figure 5 It is the test result of the influence of resin and filler on the shrinkage stress of the coating film;

[0037] Figure 6 It is the single-coat salt spray test result of ordinary waterborne epoxy primer and general-purpose waterborne epoxy primer;

[0038] Figure 7 Salt spray test results of the supporting coating of ordinary waterborne epoxy primer and general-purpose waterborne epoxy primer acrylic

[0039] Figure 8 Salt spray test results of the supporting coating of ordinary waterborne epoxy primer and general-purpose waterborne epoxy primer polyurethane Detailed implementation manners

[0040] To make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the present invention will be further described below in conjunction with specific implementation manners

[0041] In view of the problems involved in the background technology, this solution develops a waterborne epoxy primer applicable to various metal substrates, which can not only provide good anti-corrosion performance but also maintain excellent adhesion, and can greatly improve the construction efficiency during use, and has broad application prospects in the field of general industrial paints

[0042] There are two technical solutions to achieve a high-performance general-purpose waterborne epoxy primer

[0043] Solution 1. Based on ordinary E20 epoxy emulsion, use some functional resins for modification to prepare a high-performance epoxy emulsion with good flexibility, adhesion and low-temperature film-forming properties. Select E12 and PPGDGE as the main functional resins. E12 endows the E20 resin with better flexibility and hardening speed; PPGDGE is an excellent flexible group and can reduce the film-forming temperature of the epoxy emulsion. The increase in resin flexibility will offset the growth of some internal stresses during the drying process of the paint film, thereby improving the adhesion of the paint film

[0044] Solution 2. Use a high-performance epoxy emulsion and select appropriate fillers to develop a general-purpose waterborne epoxy primer with low shrinkage stress and high adhesion, and at the same time have the ability to be constructed and cured in a low-temperature environment. Flaky fillers are key components in anti-corrosion coatings. During the drying process of the paint film, the flaky fillers overlap and are arranged in an orderly manner to form a complex channel, which plays a role in delaying the passage of water through the paint film. Different fillers generate different internal stresses during the drying process of the paint film, which affect the adhesion between the paint film and the substrate, as Figure 1 shown

[0045] Combining the implementation of Solution 1 and Solution 2 can enable the high-performance general-purpose waterborne epoxy primer to have good anti-corrosion performance and at the same time maintain excellent adhesion on various metal substrates for a long time

[0046] The specific embodiments are as follows

[0047] Example 1: A high-performance general-purpose waterborne epoxy primer consists of component A and component B with a weight ratio of 12:1. The specific compositions of component A and component B are as follows:

[0048] Component A, by weight, includes: 16 parts of distilled water, 0.2 parts of anti-settling agent, 0.8 parts of dispersant, 0.9 parts of defoamer, 10 parts of coloring pigment, extender pigment 1: 20 parts of feldspar powder, extender pigment 2: 5 parts of precipitated barium sulfate, 5 parts of anti-rust pigment, 39 parts of high-performance epoxy emulsion, 1.5 parts of film-forming aid, 0.3 parts of leveling agent, 1 part of adhesion promoter, and 0.3 parts of thickener.

[0049] Component B, by weight, includes: 15 parts of distilled water, 65 parts of water-soluble amine resin, 10 parts of film-forming aid, and 10 parts of anti-floating rust agent.

[0050] Its preparation method is as follows:

[0051] Ⅰ. Grinding and dispersion stage: Add distilled water and anti-settling agent to a stirrer, stir at high speed for 15 minutes to ensure full activation of the anti-settling agent, then sequentially add dispersant, defoamer, coloring pigment, extender pigment, and anti-rust pigment, and grind through sanding for 30 minutes, with the fineness controlled below 35um; Blending and mixing stage: After filtration, add high-performance epoxy emulsion, mix the slurry and the emulsion evenly, adjust the stirring speed (500 - 1000 rpm), sequentially add film-forming aid, defoamer, leveling agent, and adhesion promoter, stir for another 5 - 10 minutes after all are added to make it fully mixed, add thickening aid, increase the stirring speed to 1000 - 1500 rpm, and continue stirring for 10 - 15 minutes. The temperature throughout the process does not exceed 60°C. Filter and package with a 150-mesh screen to obtain component A;

[0052] Ⅱ. Add distilled water to a stirrer, start stirring, sequentially add water-soluble amine resin, film-forming aid, and anti-floating rust agent, and stir at low speed for 10 - 15 minutes until uniform to obtain component B;

[0053] Ⅲ. Mix component A and component B in the weight ratio, add water for dilution, and stir evenly to be ready for construction.

[0054] Example 2: A high-performance general-purpose waterborne epoxy primer consists of component A and component B with a weight ratio of 10:1. The specific compositions of component A and component B are as follows:

[0055] Component A, by weight, includes: 16 parts of distilled water, 0.2 parts of anti-settling agent, 0.8 parts of dispersant, 0.9 parts of defoamer, 10 parts of coloring pigment, extender pigment 1: 15 parts of feldspar powder, extender pigment 2: 5 parts of precipitated barium sulfate, 5 parts of anti-rust pigment, 44 parts of high-performance epoxy emulsion, 1.5 parts of film-forming aid, 0.3 parts of leveling agent, 1 part of adhesion promoter, and 0.3 parts of thickener;

[0056] Component B, by weight, includes: 15 parts of distilled water, 65 parts of water-soluble amine resin, 10 parts of film-forming aid, and 10 parts of anti-flash rust aid.

[0057] Its preparation method refers to Example 1.

[0058] Example 3: A high-performance general-purpose waterborne epoxy primer is composed of Component A and Component B with a weight ratio of 12:1. The specific compositions of Component A and Component B are as follows:

[0059] Component A, by weight, includes: 16 parts of distilled water, 0.2 part of anti-settling aid, 0.8 part of dispersant, 0.9 part of defoamer, 10 parts of coloring pigment, Extender Pigment 1: 20 parts of talc powder, Extender Pigment 2: 5 parts of precipitated barium sulfate, 5 parts of anti-rust pigment, 39 parts of high-performance epoxy emulsion, 1.5 parts of film-forming aid, 0.3 part of leveling agent, 1 part of adhesion promoter, and 0.3 part of thickener;

[0060] Component B, by weight, includes: 15 parts of distilled water, 65 parts of water-soluble amine resin, 10 parts of film-forming aid, and 10 parts of anti-flash rust aid.

[0061] Its preparation method refers to Example 1.

[0062] Comparative Example 1: Ordinary waterborne epoxy primer

[0063] A. Influence of high-performance epoxy emulsion on film properties

[0064] Influence on tensile properties: After the coatings of Example 1 and Comparative Example 1 were made, tensile property tests were carried out, as Figure 2 shown. From the results in Table 1, it can be seen that compared with the coating prepared in Comparative Example 1, the flexibility of the coating in Example 1 was significantly improved, the elongation rate increased from 35.97% to 113.76%, and at the same time, the film hardness decreased, and the maximum tensile force decreased from 42.5 Pa to 33.7 Pa. It shows that the elasticity of the film in Example 1 increased, and the rigidity and brittleness decreased.

[0065] Table 1 Comparison of tensile properties

[0066]

[0067] Influence on low-temperature adhesion: After the coatings of Example 1 and Comparative Example 1 were made, low-temperature adhesion tests were carried out. Epoxy coatings with a dry film thickness of 50 - 60 μm were air-sprayed on cold-rolled steel plates, baked at 55°C and 80°C for 20 minutes respectively, taken out of the oven, left at room temperature for 2 - 3 hours, and then transferred to an environment of -5°C - 0°C for 16 hours, and the cross-cut adhesion was tested. The results are as Figure 3As shown, obvious peeling occurred in the cross-cut adhesion of Comparative Example 1, and the cross-cut adhesion result of Example 1 was basically intact, at the 0-1 level. From the impact results, obvious cracking and peeling occurred in Comparative Example 1, and the film surface of Example 1 was normal and intact after impact. The adhesion of Example 1 under low-temperature and high-temperature drying conditions was significantly better than that of Comparative Example 1.

[0068] Effect on low-temperature film-forming performance: After the coatings of Example 1 and Comparative Example 1 were prepared, the minimum film-forming temperature was tested, as Figure 4 shown. The film-forming temperature of Example 1 decreased significantly compared with that of Comparative Example 1, from 9.5 °C to 3.4 °C, which was more conducive to crosslinking and curing at low temperatures and extended the curable time in low-temperature environments.

[0069] Table 2 Comparison of minimum film-forming temperature

[0070] Minimum Film Formation Temperature (MFT) Comparative Example 1 9.5℃ Example 1 3.4℃

[0071] Based on the above experimental results, the epoxy emulsion in Example 1 was modified by a functional resin, which improved the flexibility and adhesion and had certain low-temperature film-forming performance. Compared with the ordinary epoxy emulsion in Comparative Example 1, the high-performance epoxy emulsion in Example 1 could provide better mechanical properties and film-forming properties.

[0072] B. Influence of resin and filler on the shrinkage stress of the paint film:

[0073] After the coatings of Example 1, Example 2, Example 3, and Comparative Example 1 were prepared, the shrinkage stress was tested, as Figure 5 shown.

[0074] Take an OPH thin plate, and evenly scrape a paint film on it with a film applicator, and control the dry film thickness to be 50-100 μm. Bake at 60 °C for 10 minutes or dry naturally until the paint film reaches at least semi-hard dryness. Cut the OPH thin plate into 2-3 strips of 20×120 mm with a paper cutter. Place it horizontally in an environment with a temperature of 40 °C and a humidity of <10% for 30 days, and measure the height of the two ends of the OPH thin plate that warps up with a vernier caliper. The higher the warping height, the greater the shrinkage stress.

[0075] It can be seen from the results in Table 3 that the resin type, PVC, and filler type will all affect the shrinkage stress of the paint film.

[0076] Influence of resin type: On the basis of maintaining the same PVC and filler types, the shrinkage stress of the high-performance epoxy emulsion paint film (Example 1) produced a bending height of 30.47 mm; the shrinkage stress of the ordinary epoxy emulsion paint film (Comparative Example 1) produced a bending height of 35.72 mm. Due to the improvement of the flexibility of the high-performance epoxy emulsion, part of the shrinkage stress generated during the drying process of the paint film was offset, so the shrinkage stress of the paint film in Example 1 was significantly reduced.

[0077] Influence of PVC: On the basis of using the same emulsion and filler, the ratio of resin to filler in the formula was adjusted to obtain paint films with different PVC results. The shrinkage stress of the low-PVC paint film (Example 2) was 28.90 mm bending height, and the shrinkage stress of the high-PVC paint film (Example 1) was 30.47 mm bending height. The shrinkage stress of the low-PVC paint film was lower than that of the high-PVC paint film. The reason is that the increase in resin content improved the flexibility of the paint film, thereby offsetting part of the shrinkage stress generated during the drying process.

[0078] Influence of filler type: On the basis of maintaining the same emulsion and PVC, the shrinkage stress generated by the flaky talc paint film (Example 3) was 27.15 mm bending height, and the shrinkage stress generated by the flaky feldspar powder paint film (Example 1) was 30.47 mm bending height. The shrinkage stress generated by the flaky talc was significantly lower than that of the flaky feldspar powder. The reason may be related to the hardness and aspect ratio of the filler.

[0079] Table 3 Comparison of shrinkage stress

[0080]

[0081] Based on the above experimental results, among the influencing factors of shrinkage stress, resin is the main factor, the secondary factor is the type of filler, and PVC (resin content) also has a certain influence.

[0082] As a general-purpose waterborne epoxy primer, the selection of filler should consider its influence on adhesion and anti-corrosion performance at the same time. From the above experimental results, it can be seen that flaky talc is the best choice because it not only has low shrinkage stress but also has good physical shielding effect, which can meet all the requirements of the general-purpose waterborne epoxy primer.

[0083] C. Salt spray test results of ordinary waterborne epoxy primer and general-purpose waterborne epoxy primer:

[0084] For Example 3 and Comparative Example 1, after preparing the coating films as required, salt spray tests were carried out. They were respectively coated on different substrates, including: hot-rolled steel plate, cold-rolled steel plate, stainless iron plate, stainless steel plate, galvanized steel plate, and aluminum plate. According to the usage requirements under normal circumstances, the long-term anti-corrosion performance and adhesion changes of the single coating of waterborne epoxy primer, the matching coating of waterborne epoxy primer + waterborne acrylic topcoat, and the matching coating of waterborne epoxy primer + waterborne polyurethane topcoat were respectively tested.

[0085] For the case of the single coating of waterborne epoxy primer: As Figure 6 shown in the results, after 600 hours of salt spray test for the single coating of waterborne epoxy primer, obvious blistering and rusting phenomena appeared on the surface of the hot-rolled steel plate in Comparative Example 1; obvious blistering phenomena occurred at the accelerated line positions of the cold-rolled steel plate and the galvanized steel plate; the secondary adhesion of the galvanized steel plate had peeling, and with the extension of the salt spray time, the adhesion showed a downward trend. The surface coatings of various substrates in Example 3 were in good condition, without blistering and rusting, and the secondary adhesion was 0-1 level; obvious blistering phenomena occurred at the accelerated line positions of the galvanized steel plate (the electrochemical properties of cold galvanizing are active and it is easy to oxidize into loose zinc oxide in the salt spray environment, and the epoxy primer loses adhesion on the soft substrate, resulting in blistering phenomena, and there is an expanding trend with the extension of the salt spray time).

[0086] For the case of the matching coating of waterborne epoxy primer + waterborne acrylic topcoat: As Figure 7 shown in the results, after 1500 hours of salt spray test, obvious blistering phenomena occurred at the accelerated line positions of the cold-rolled steel plate in Comparative Example 1; the secondary adhesion of the matching coating of the galvanized steel plate seriously peeled off, and the blistering at the accelerated line extended significantly. The surface coatings of various substrates in Example 3 were in good condition, without blistering and rusting, and the secondary adhesion was 0-1 level; obvious blistering phenomena occurred at the accelerated line positions of the galvanized steel plate.

[0087] For the case of the matching coating of waterborne epoxy primer + waterborne polyurethane topcoat: As Figure 8 shown in the results, after 1500 hours of salt spray test, obvious blistering phenomena occurred at the accelerated line positions of the cold-rolled steel plate and the stainless iron plate in Comparative Example 1; the secondary adhesion of the matching coating of the galvanized steel plate seriously peeled off, and the adhesion loss occurred at the initial stage of the test, and the blistering at the accelerated line extended significantly. There were blistering phenomena at the accelerated lines of the stainless iron plate and the galvanized steel plate in Example 3; the secondary adhesion of all substrate plates was 0-1 level.

[0088] The phenomena such as blistering on the plate surface, rusting, blistering at the accelerated line, and adhesion peeling off in the above test results are mainly caused by two reasons:

[0089] 1. The shielding property of the coating film itself is not strong, and the moisture in the environment penetrates through the coating film, resulting in a decrease in adhesion and the occurrence of phenomena such as rusting and blistering on the plate surface.

[0090] 2. Large shrinkage stress of the coating leads to decreased adhesion and blistering. The shrinkage stress of the coating comes from the superposition of shrinkage stress generated by each paint film in the coating, including primer and topcoat. Since polyurethane topcoat is a two-component thermosetting coating and acrylic topcoat is a one-component thermoplastic coating, the shrinkage stress generated by polyurethane topcoat is greater than that of acrylic topcoat, and the impact on the adhesion of the matching coating is also greater.

[0091] Waterborne epoxy primer plays a connecting role in the supporting coating. On the one hand, it must have strong adhesion and low shrinkage stress, and be able to establish a strong bond with a variety of substrates. On the other hand, it must also have a certain degree of flexibility to absorb the downward transmission of shrinkage stress of the upper layer of the topcoat and minimize the impact of the shrinkage stress of the upper layer on adhesion.

[0092] Comprehensive analysis of the salt spray results of the above three coatings shows that the adhesion and anti-corrosion performance of Comparative Example 1 on different plates are not ideal, and cannot be used as a general-purpose epoxy primer; Example 3 has excellent adhesion and anti-corrosion performance on different plates. Under normal construction conditions, it can maintain good adhesion and anti-corrosion performance on a variety of metal substrates for a long time, and can be used as a general-purpose epoxy primer.

[0093] D. Conclusion:

[0094] This study developed a high-performance universal waterborne epoxy primer by using a high-performance waterborne epoxy emulsion with enhanced flexibility and adhesion, combined with flaky talc as the main filler. It has the characteristics of low shrinkage stress, excellent adhesion and shielding properties, and can play a good role in corrosion protection and connection on a variety of metal substrates. It is particularly suitable for construction operations in complex substrate environments in the general industrial paint field, and greatly improves construction efficiency while providing good performance.

[0095] The test results of Example 3 meet the product design requirements and can maintain good adhesion and anti-corrosion performance on a variety of metal substrates for a long time. The application of high-performance universal waterborne epoxy primer reduces the difficulty of operation in complex substrate environments, provides simplified response measures, significantly improves work efficiency, and has broad application prospects in the field of general industrial paints.

[0096] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A high-performance general-purpose waterborne epoxy primer, characterized in that: It is composed of component A and component B with a weight ratio of (10 - 15):

1. The specific compositions of component A and component B are as follows: Component A includes, by weight parts: 15 - 20 parts of distilled water, 0.1 - 0.5 parts of anti-settling agent, 0.5 - 1 part of dispersant, 0.4 - 1 part of defoamer, 5 - 15 parts of coloring pigment, 30 - 45 parts of extender pigment, 3 - 8 parts of anti-rust pigment, 35 - 45 parts of high-performance epoxy emulsion, 1 - 2 parts of film-forming aid, 0.2 - 0.5 part of leveling agent, 0.5 - 1.5 parts of adhesion promoter, 0.1 - 0.5 part of thickener; Component B includes, by weight parts: 10 - 20 parts of distilled water, 60 - 80 parts of water-soluble amine resin, 5 - 10 parts of film-forming aid, 10 - 15 parts of anti-flash rust agent; The high-performance epoxy emulsion is a bisphenol A epoxy emulsion, which is a new type of waterborne epoxy emulsion made by modification.

2. The high-performance general-purpose waterborne epoxy primer according to claim 1, characterized in that: The anti-settling agent is lithium-based modified montmorillonite powder; The sodium-based modified montmorillonite powder is further reacted with lithium salt to replace sodium ions with lithium ions, thereby obtaining lithium-based modified montmorillonite powder.

3. The high-performance general-purpose waterborne epoxy primer according to claim 1, characterized in that: The dispersant is a polymer non-ionic wetting dispersant; the defoamer is used alone or in combination of water-soluble silicone and non-silicone defoamers; the coloring pigment is one or more of titanium dioxide, iron red, carbon black; the extender pigment is one or more of flaky pure talc powder, precipitated barium sulfate, mica powder, feldspar powder; the anti-rust pigment is a type of aluminum tripolyphosphate anti-rust pigment; the film-forming aid is a propylene glycol ether solvent; the leveling agent is used alone or in combination of water-soluble silicone and non-silicone leveling agents; the adhesion promoter is an epoxy silane oligomer coupling agent; the thickener is a non-ionic polyurethane thickener; the anti-flash rust agent is a complex anti-flash rust agent.

4. The high-performance general-purpose waterborne epoxy primer according to claim 1, characterized in that: The water-soluble amine resin is a hydrophilic amine resin adduct having one or more of o-phenylenediamine monomer, tetraethylenediamine monomer, IPDA.

5. The preparation method of a high-performance general-purpose waterborne epoxy primer according to claims 1-4, characterized in that: The preparation method includes the following steps: Step 1: Grinding and dispersion stage: Add distilled water and anti-settling agent to a stirrer, stir at high speed for 15 min to ensure full activation of the anti-settling agent, then sequentially add dispersant, defoamer, coloring pigment, extender pigment, and anti-rust pigment, and grind for 30 min through sand grinding, with the fineness controlled below 35 um; Blending and mixing stage: After filtration, add high-performance epoxy emulsion, mix the slurry and the emulsion evenly, adjust the stirring speed (500 - 1000 rpm), sequentially add film-forming aid, defoamer, leveling agent, and adhesion promoter, and stir for another 5 - 10 minutes after all are added to make it fully mixed. Add thickening agent, increase the stirring speed to 1000 - 1500 rpm, and continuously stir for 10 - 15 minutes. The whole process temperature does not exceed 60 °C, and filter and package with a 150-mesh screen to obtain component A; Step 2: Add distilled water to a stirrer, start stirring, and sequentially add water-soluble amine resin, film-forming aid, and anti-flash rust agent, and stir at low speed for 10 - 15 minutes until uniform to obtain component B; Step 3: Mix component A and component B according to the weight ratio, dilute with water, stir evenly, and then it can be applied.

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