Waterborne epoxy coating not easy to crack and preparation method thereof

Abstract

The invention belongs to the technical field of epoxy coatings, and particularly relates to a waterborne epoxy coating not prone to cracking and a preparation method of the waterborne epoxy coating. Comprising a component A and a component B, the component A and the component B are mixed according to the mass part ratio of 4: 1-6: 1 and are subjected to cross-linking and curing to form the epoxy resin coating, the component A is a curing agent component, and the component B is an epoxy resin component; the anti-cracking performance of the coating is greatly improved through the synergistic effect of multiple components; the volume shrinkage can be compensated during curing of the expanded microspheres, and the internal stress is reduced; the wood fibers form a three-dimensional interwoven structure, so that the flexibility and the deformation resistance of the coating are enhanced; and the three components are matched to inhibit crack generation from multiple dimensions of stress relief, toughness improvement and strength support, so that the coating can still be kept complete under the working conditions of base material deformation, temperature fluctuation and the like, and the protection period is prolonged.

Description

Technical Field

[0001] This invention belongs to the field of epoxy coating technology, specifically relating to a method for preparing a water-based epoxy coating that is not prone to cracking. Background Technology

[0002] In the field of industrial coating and protection, water-based epoxy coatings are widely used due to their environmentally friendly properties, but existing products have obvious technical shortcomings.

[0003] Most waterborne epoxy coatings are prone to cracking after curing. The root cause is that the volume shrinkage during the curing process generates internal stress, and the coating is not flexible enough. When faced with substrate deformation or temperature changes, it is difficult to buffer stress, which leads to crack initiation. At the same time, the poor compatibility between the two components makes it easy to have uneven dispersion, which further aggravates the internal structural defects of the coating.

[0004] In addition, existing coatings mostly rely on the modification of a single raw material to improve crack resistance, making it difficult to balance strength, flexibility and stability. This makes them unable to meet the long-term crack resistance protection requirements of coatings in scenarios such as building and equipment corrosion protection, thus limiting their application scope. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing a water-based epoxy coating that is resistant to cracking.

[0006] A water-based epoxy coating that is not prone to cracking includes component A and component B, wherein component A and component B are mixed in a mass ratio of 4:1 to 6:1 and then crosslinked and cured. Component A is a curing agent component and component B is an epoxy resin component. The first component, by mass, comprises the following raw materials: 15-25 parts deionized water, 0.5-1.5 parts modified polymeric dispersant, 0.4-0.9 parts multifunctional additive, 0.1-0.3 parts nonionic compatibility promoter, HLB value of fatty alcohol polyoxyethylene ether of 8-12, 1-25 parts optional pigment (if present), 5-30 parts filler, 30-40 parts waterborne epoxy curing agent, 1-3 parts expanded microspheres, 0.2-1 parts wood fiber, 2-8 parts ceramic powder, 0.3-0.5 parts polyether defoamer, polyoxyethylene polyoxypropylene block copolymer, 0.5-1 parts wetting and leveling agent, and acrylate leveling agent with a molecular weight of 2000-5000, tested using gel permeation chromatography with polystyrene as a standard. The B component comprises the following raw materials by mass: 90-95 parts of low molecular weight epoxy resin and 5-10 parts of reactive diluent.

[0007] Preferably, the deionized water in component A is high-purity deionized water with a conductivity ≤5μS / cm at 25℃, and a mass fraction of 20-22 parts.

[0008] Preferably, the modified polymeric dispersant is a polyurethane-grafted acrylate copolymer dispersant, with a mass fraction of 1.0 to 1.2 parts and a number average molecular weight of 5,000 to 10,000. It is tested by gel permeation chromatography, with polystyrene as the standard and tetrahydrofuran as the mobile phase.

[0009] Preferably, the expanded microspheres are core-shell structured thermally expanded microspheres, with isobutane as the core material and cross-linked acrylic resin as the shell material, in a mass fraction of 2.0 to 2.5 parts, an initial D50 particle size of 20 to 30 μm, and an expansion ratio of 3 to 5 times at 80 to 120°C as measured by a laser particle size analyzer. The expansion ratio is the ratio of the expanded particle size to the initial particle size.

[0010] Preferably, the wood fiber is coniferous wood fiber modified with γ-glycidoxypropyltrimethoxysilane, with a modification amount of 1-3% of the fiber mass, a fiber length of 100-300 μm, a diameter of 10-30 μm, and a mass fraction of 0.5-0.8 parts by microscopy.

[0011] Preferably, the ceramic powder is micron-sized alumina ceramic powder with a purity ≥99%, tested by X-ray fluorescence spectroscopy, and a D50 particle size of 1-3 μm, tested by a laser particle size analyzer. It is surface-treated with γ-aminopropyltriethoxysilane at a rate of 2-4% of the ceramic powder mass, or 5-6 parts by mass.

[0012] Preferably, the low molecular weight epoxy resin in component B is bisphenol A type epoxy resin E-51, the reactive diluent is butyl glycidyl ether, the epoxy value is 0.4-0.6 eq / 100g, and the mass fraction is 7-8 parts.

[0013] Preferably, the filler is a composite filler composed of talc powder and barite powder in a mass ratio of 1:1, wherein the D50 particle size of the talc powder is 5-10 μm, the D50 particle size of the barite powder is 20-30 μm, both measured by a laser particle size analyzer, and the total mass fraction is 15-20 parts.

[0014] A method for preparing a water-based epoxy coating that is not prone to cracking includes the following steps: (1) Preparation of material A: Deionized water, modified polymeric dispersant, multifunctional additive and nonionic compatibility promoter are added to a container according to the mass fraction, and stirred at 1000 r / min for 15 min at 25-30℃ to obtain material A; (2) Preparation of material B: Mix material A with pigments and fillers, stir at 1200 r / min for 10 min and maintain the temperature at 25℃, then disperse at 2800 r / min for 45 min. Control the viscosity of the material at 25℃ to be 800-1000 mPa·s. Use an NDJ-1 type rotational viscometer with a rotor speed of 60 r / min to obtain material B. (3) Preparation of Material C: Mix Material B with water-based epoxy curing agent, expanded microspheres, wood fiber, ceramic powder and polyether defoamer, stir at 1200 r / min for 10 min until the bubble volume fraction is ≤0.1%, test by image analysis method, take the average value of 3 parallel samples, add wetting and leveling agent, stir at 1000 r / min for 15 min at 20-25℃ to obtain Material C: (4) Preparation of component A: Filter material C through a 120-mesh nylon filter cloth that has been boiled and dried in deionized water at 80℃, and collect the filtrate: (5) Preparation of component B: Low molecular weight epoxy resin and reactive diluent are stirred at 600 r / min for 20 min at 30℃. The viscosity of the system at 25℃ is controlled to be 500-600 mPa·s. NDJ-1 type rotational viscometer is used with a rotor speed of 60 r / min to obtain component B. (6) Mixed finished product: Mix component A and component B in a mass ratio of 4:1 to 6:1 and stir at 900 r / min for 8 min to obtain waterborne epoxy coating.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention significantly improves the crack resistance of the coating through the synergistic effect of multiple components: the expansion microspheres can compensate for volume shrinkage during curing and reduce internal stress; the wood fibers form a three-dimensional interwoven structure, which enhances the flexibility and deformation resistance of the coating; the ceramic powder filler enhances the structural strength. The three components work together to suppress crack generation from multiple dimensions such as stress relief, toughness improvement and strength support, so that the coating can remain intact under conditions such as substrate deformation and temperature fluctuation, and extend the protection period.

[0016] (2) In this invention, the compatibility and stability of the two-component system are improved by using a non-ionic compatibility promoter in combination with a modified polymeric dispersant to improve the mixing and dispersion effect of the curing agent component and the epoxy resin component, and avoid local stress concentration and structural defects caused by uneven component distribution. At the same time, the reasonable raw material ratio and preparation process ensure the stable performance of the coating during storage and construction, and it is not easy to have problems such as layering and sedimentation, thereby improving the ease of construction and the consistency of coating quality.

[0017] (3) This invention takes into account both environmental protection and practicality. It is based on a water-based system and uses deionized water as the dispersion medium to avoid the volatilization of harmful solvents in traditional solvent-based coatings, which meets environmental protection requirements. Moreover, the selection and combination of fillers, additives and other components in the coating formulation enable it to be compatible with a variety of common substrates such as concrete and metal. It can play a good role in many fields such as building exterior wall protection and equipment corrosion prevention, and has both environmental protection value and a wide range of application scenarios. Detailed Implementation

[0018] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0019] The raw materials used in both the examples and comparative examples are commercially available. Example 1: This example provides a method for preparing a water-based epoxy coating that is not prone to cracking, comprising the following steps: Step 1: Raw Material Preparation Component A raw material: 20 parts of deionized water. The deionized water is high-purity deionized water with a conductivity of ≤5μS / cm at 25℃.

[0020] 1.0 part of modified polymeric dispersant, the dispersant is a polyurethane-grafted acrylate copolymer dispersant with a number average molecular weight of 5000-10000. The test is performed by gel permeation chromatography, with polystyrene as the standard and tetrahydrofuran as the mobile phase.

[0021] 0.6 parts of multifunctional additive, 0.2 parts of nonionic compatibility promoter, and fatty alcohol polyoxyethylene ether with an HLB value of 8-12.

[0022] 15 parts of pigment, the pigment being titanium dioxide.

[0023] 20 parts of filler were used. The filler was a composite filler made of talc powder and barite powder mixed in a mass ratio of 1:1. The D50 particle size of the talc powder was 5-10 μm and the D50 particle size of the barite powder was 20-30 μm. The particle size of both was measured by a laser particle size analyzer.

[0024] 35 parts of water-based epoxy curing agent; 2.0 parts of expanded microspheres. The expanded microspheres are core-shell structured thermally expanded microspheres with isobutane as the core material and cross-linked acrylic resin as the shell material. The initial D50 particle size is 20-30μm. The expansion ratio is 3-5 times under conditions of 80-120℃, and the expansion ratio is calculated as the ratio of the expanded particle size to the initial particle size.

[0025] 0.6 parts of wood fiber, which is coniferous wood fiber modified with γ-glycidoxypropyltrimethoxysilane, with a modification amount of 2% of the fiber mass, fiber length of 100-300μm and diameter of 10-30μm, were tested by microscopy.

[0026] Four parts of ceramic powder, which is micron-sized alumina ceramic powder with a purity of ≥99%, were tested by X-ray fluorescence spectroscopy. The D50 particle size is 1-3μm, which was tested by laser particle size analyzer. The powder was surface treated with γ-aminopropyltriethoxysilane at a rate of 3% of the ceramic powder mass.

[0027] 0.4 parts of polyether-based defoamer, which is a polyoxyethylene-polyoxypropylene block copolymer.

[0028] 0.8 parts of wetting and leveling agent, which is an acrylate leveling agent with a molecular weight of 2000-5000, were tested using gel permeation chromatography with polystyrene as a standard.

[0029] Step 2: Preparation S1: Preparation of Material A: According to the mass proportions of the above-mentioned component A raw materials, deionized water, modified polymeric dispersant, multifunctional additive, and nonionic compatibility promoter are added sequentially to the mixing container. The temperature inside the mixing container is controlled at 25-30℃, the stirring speed is adjusted to 1000 r / min, and stirring is continued for 15 min. After the materials are mixed evenly, material A is obtained.

[0030] S2: Preparation of Material B: Add Material A, pigments, and fillers to a mixing container. First, adjust the stirring speed to 1200 r / min and stir continuously for 10 minutes, maintaining a stable temperature of 25℃ inside the container during stirring. Then, increase the stirring speed to 2800 r / min for high-speed dispersion, with a dispersion time of 45 minutes. During dispersion, use an NDJ-1 rotational viscometer to test the material viscosity, controlling the rotor speed at 60 r / min to ensure the material viscosity remains between 800-1000 mPa·s at 25℃. Material B is obtained after dispersion.

[0031] S3: Preparation of Material C: Add water-based epoxy curing agent, expanded microspheres, wood fiber, ceramic powder and polyether defoamer sequentially to the mixing container containing Material B. Adjust the stirring speed to 1200 r / min and continue stirring for 10 min. Use image analysis to test the volume fraction of bubbles in the material and take the average of the test results of 3 parallel samples to ensure that the volume fraction of bubbles is ≤0.1%. Add wetting and leveling agent, control the temperature in the mixing container at 20-25℃, adjust the stirring speed to 1000 r / min and continue stirring for 15 min to obtain Material C.

[0032] S4: Preparation of component A: Prepare 120-mesh nylon filter cloth, boil and wash the filter cloth with deionized water at 80℃ and then dry it. Use the treated filter cloth to filter material C and collect the filtrate, which is component A.

[0033] S5: Preparation of Component B: Add low molecular weight epoxy resin and reactive diluent to a stirring container, control the temperature inside the container at 30℃, adjust the stirring speed to 600r / min, and continue stirring for 20min. Use an NDJ-1 type rotational viscometer to test the viscosity of the system, control the rotor speed at 60r / min, and ensure that the viscosity of the system is maintained at 500-600mPa・s at 25℃. After stirring evenly, Component B is obtained.

[0034] S6: Mixed finished product: Add component A and component B to the mixing container in a mass ratio of 5:1, adjust the speed of the mixing equipment to 900 r / min, and continue mixing for 8 minutes. After the materials are completely mixed and uniform, a water-based epoxy coating that is not easy to crack is obtained.

[0035] Example 2, Step 1: Raw material preparation Component A raw material: 22 parts of deionized water. The deionized water is high-purity deionized water with a conductivity of ≤5μS / cm at 25℃.

[0036] 1.2 parts of modified polymeric dispersant, the dispersant being a polyurethane-grafted acrylate copolymer dispersant with a number average molecular weight of 5000-10000, were tested using gel permeation chromatography with polystyrene as the standard and tetrahydrofuran as the mobile phase.

[0037] 0.9 parts of multifunctional additive; 0.3 parts of nonionic compatibility promoter; fatty alcohol polyoxyethylene ether with an HLB value of 8-12.

[0038] 25 parts pigment, carbon black was selected as the pigment.

[0039] 25 parts of filler were used. The filler was a composite filler made of talc powder and barite powder mixed in a mass ratio of 1:1. The D50 particle size of the talc powder was 5-10 μm and the D50 particle size of the barite powder was 20-30 μm. The particle size of both was measured by a laser particle size analyzer.

[0040] 40 parts of water-based epoxy curing agent; 2.5 parts of expanded microspheres. The expanded microspheres are core-shell structured thermally expanded microspheres with isobutane as the core material and cross-linked acrylic resin as the shell material. The initial D50 particle size is 20-30μm. The expansion ratio is 3-5 times under conditions of 80-120℃, and the expansion ratio is calculated as the ratio of the expanded particle size to the initial particle size.

[0041] 0.8 parts of wood fiber, which is coniferous wood fiber modified with γ-glycidoxypropyltrimethoxysilane, with a modification amount of 3% of the fiber mass, fiber length of 100-300μm and diameter of 10-30μm, were tested by microscopy.

[0042] Six parts of ceramic powder, which is micron-sized alumina ceramic powder with a purity ≥99%, tested by X-ray fluorescence spectroscopy, and a D50 particle size of 1-3μm, tested by laser particle size analyzer, and surface treated with γ-aminopropyltriethoxysilane at a rate of 4% of the ceramic powder mass; 0.5 parts of polyether defoamer, which is a polyoxyethylene-polyoxypropylene block copolymer.

[0043] 1.0 part of wetting and leveling agent. This leveling agent is an acrylate leveling agent with a molecular weight of 2000-5000. The test is performed by gel permeation chromatography with polystyrene as the standard.

[0044] Component B raw material: 95 parts of low molecular weight epoxy resin, the epoxy resin is bisphenol A type epoxy resin E-51; Five parts of reactive diluent, the diluent being butyl glycidyl ether, with an epoxy value of 0.4-0.6 eq / 100g.

[0045] Step 2: Preparation S1: Preparation of Material A: According to the mass proportions of the above-mentioned component A raw materials, deionized water, modified polymeric dispersant, multifunctional additive, and nonionic compatibility promoter are added sequentially to the mixing container. The temperature inside the mixing container is controlled at 25-30℃, the stirring speed is adjusted to 1000 r / min, and stirring is continued for 15 min. After the materials are mixed evenly, material A is obtained.

[0046] S2: Preparation of Material B: Add Material A, pigments, and fillers to a mixing container. First, adjust the stirring speed to 1200 r / min and stir continuously for 10 minutes, maintaining a stable temperature of 25°C inside the container during stirring. Then, increase the stirring speed to 2800 r / min for high-speed dispersion, with a dispersion time of 45 minutes. During dispersion, use an NDJ-1 rotational viscometer to test the material viscosity, controlling the rotor speed at 60 r / min to ensure the material viscosity remains between 800-1000 mPa·s at 25°C. Material B is obtained after dispersion.

[0047] S3: Preparation of Material C: Add water-based epoxy curing agent, expanded microspheres, wood fiber, ceramic powder, and polyether defoamer sequentially to the mixing container containing Material B. Adjust the stirring speed to 1200 r / min and continue stirring for 10 min. Use image analysis to test the bubble volume fraction in the material, and take the average of the test results of 3 parallel samples to ensure that the bubble volume fraction is ≤0.1%. Then add a wetting and leveling agent, control the temperature inside the mixing container at 20-25℃, adjust the stirring speed to 1000 r / min, and continue stirring for 15 min to obtain Material C.

[0048] S4: Preparation of component A: Prepare 120-mesh nylon filter cloth, boil and wash the filter cloth with deionized water at 80℃ and then dry it. Use the treated filter cloth to filter material C and collect the filtrate, which is component A.

[0049] S5: Preparation of Component B: Add low molecular weight epoxy resin and reactive diluent to a stirring container, control the temperature inside the container at 30℃, adjust the stirring speed to 600r / min, and continue stirring for 20min. Use an NDJ-1 type rotational viscometer to test the viscosity of the system, control the rotor speed at 60r / min, and ensure that the viscosity of the system is maintained at 500-600mPa・s at 25℃. After stirring evenly, Component B is obtained.

[0050] S6: Mixed finished product: Add component A and component B to the mixing container in a mass ratio of 6:1, adjust the speed of the mixing equipment to 900 r / min, and continue mixing for 8 minutes. After the materials are completely mixed and uniform, a water-based epoxy coating that is not easy to crack is obtained.

[0051] Example 3, Step 1: Raw material preparation Component A raw material: 18 parts of deionized water. This deionized water is high-purity deionized water with a conductivity ≤5μS / cm at 25℃.

[0052] 0.8 parts of modified polymeric dispersant were used. The dispersant was a polyurethane-grafted acrylate copolymer dispersant with a number average molecular weight of 5000-10000. The test was performed using gel permeation chromatography with polystyrene as the standard and tetrahydrofuran as the mobile phase.

[0053] 0.4 parts of multifunctional additive; 0.1 parts of nonionic compatibility promoter; fatty alcohol polyoxyethylene ether with an HLB value of 8-12.

[0054] Five parts pigment, using iron oxide red as the pigment.

[0055] 15 parts of filler were used. The filler was a composite filler made of talc powder and barite powder mixed in a mass ratio of 1:1. The D50 particle size of the talc powder was 5-10 μm and the D50 particle size of the barite powder was 20-30 μm. The particle size of both was measured by a laser particle size analyzer.

[0056] 30 parts of water-based epoxy curing agent; 1.5 parts of expanded microspheres. The expanded microspheres are core-shell structured thermally expanded microspheres with isobutane as the core material and cross-linked acrylic resin as the shell material. The initial D50 particle size is 20-30μm. The expansion ratio is 3-5 times under conditions of 80-120℃, and the expansion ratio is calculated as the ratio of the expanded particle size to the initial particle size.

[0057] 0.5 parts of wood fiber, which is coniferous wood fiber modified with γ-glycidoxypropyltrimethoxysilane, with a modification amount of 1% of the fiber mass, fiber length of 100-300 μm and diameter of 10-30 μm, were tested by microscopy.

[0058] Two portions of ceramic powder, which are micron-sized alumina ceramic powders with a purity ≥99%, were tested using X-ray fluorescence spectroscopy. The D50 particle size is 1-3 μm, which was tested using a laser particle size analyzer. The powders were surface-treated with γ-aminopropyltriethoxysilane at a rate of 2% of the ceramic powder mass.

[0059] 0.3 parts of polyether defoamer, which is a polyoxyethylene-polyoxypropylene block copolymer; 0.5 parts of wetting and leveling agent, which is an acrylate leveling agent with a molecular weight of 2000-5000. The test was performed using gel permeation chromatography with polystyrene as the standard.

[0060] Component B raw material: 90 parts of low molecular weight epoxy resin, the epoxy resin is bisphenol A type epoxy resin E-51.

[0061] Ten parts of reactive diluent, the diluent being butyl glycidyl ether, with an epoxy value of 0.4-0.6 eq / 100g.

[0062] Step 2: Preparation S1: Preparation of Material A: According to the mass proportions of the above-mentioned component A raw materials, deionized water, modified polymeric dispersant, multifunctional additive, and nonionic compatibility promoter are added sequentially to the mixing container. The temperature inside the mixing container is controlled at 25-30℃, the stirring speed is adjusted to 1000 r / min, and stirring is continued for 15 min. After the materials are mixed evenly, material A is obtained.

[0063] S2: Preparation of Material B: Add Material A, pigments, and fillers to a mixing container. First, adjust the stirring speed to 1200 r / min and stir continuously for 10 minutes, maintaining a stable temperature of 25°C inside the container during stirring. Then, increase the stirring speed to 2800 r / min for high-speed dispersion, with a dispersion time of 45 minutes. During dispersion, use an NDJ-1 rotational viscometer to test the material viscosity, controlling the rotor speed at 60 r / min to ensure the material viscosity remains between 800-1000 mPa·s at 25°C. Material B is obtained after dispersion.

[0064] S3: Preparation of Material C: Add water-based epoxy curing agent, expanded microspheres, wood fiber, ceramic powder, and polyether defoamer sequentially to the mixing container containing Material B. Adjust the stirring speed to 1200 r / min and continue stirring for 10 min. Use image analysis to test the bubble volume fraction in the material, and take the average of the test results of 3 parallel samples to ensure that the bubble volume fraction is ≤0.1%. Then add a wetting and leveling agent, control the temperature inside the mixing container at 20-25℃, adjust the stirring speed to 1000 r / min, and continue stirring for 15 min to obtain Material C.

[0065] S4: Preparation of component A: Prepare 120-mesh nylon filter cloth, boil and wash the filter cloth with deionized water at 80℃ and then dry it. Use the treated filter cloth to filter material C and collect the filtrate, which is component A.

[0066] S5: Preparation of Component B: Low molecular weight epoxy resin and reactive diluent are added to a mixing container. The temperature inside the container is controlled at 30℃, and the stirring speed is adjusted to 600 r / min. Stirring is continued for 20 min. The viscosity of the system is tested using an NDJ-1 rotational viscometer, with the rotor speed controlled at 60 r / min to ensure that the viscosity of the system is maintained at 500-600 mPa·s at 25℃. After thorough stirring, component B is obtained.

[0067] S6: Mixed finished product: Add component A and component B to the mixing container in a mass ratio of 4:1, adjust the speed of the mixing equipment to 900 r / min, and continue mixing for 8 minutes. After the materials are completely mixed evenly, a water-based epoxy coating that is not easy to crack is obtained.

[0068] Comparative Example 1 lacks the expanded microspheres compared to Example 1.

[0069] Comparative Example 2: The wood fibers were not modified compared to Example 2.

[0070] Comparative Example 3 shows a deviation in the two-component allocation ratio compared to Example 3.

[0071] The test data above are shown in Tables 1 and 2.

[0072] Table 1 – Test results of Examples 1–3 and Comparative Examples 1–3

[0073] Table 2 – Test Results of Examples 1-3 and Comparative Examples 1-3

[0074] As can be seen from the above, the waterborne epoxy coatings in the examples exhibit superior performance compared to the comparative examples in terms of crack resistance, tensile strength, elongation at break, compatibility, storage stability, and adhesion. Particularly in terms of crack resistance, no cracks were observed in the examples, while the comparative examples all showed varying degrees of cracking. This indicates that the waterborne epoxy coatings prepared with a suitable two-component ratio have superior overall performance, are less prone to cracking, and exhibit better storage stability and adhesion.

[0075] In summary, the first crucial step in preparing this type of waterborne epoxy coating, which is resistant to cracking and boasts excellent overall performance, is raw material preparation. Careful selection of various raw materials that meet performance requirements is essential, including high-quality epoxy resin, curing agent, solvent, and various additives. Ensuring that the purchased raw materials are of stable quality, meet purity standards, and exhibit good compatibility among themselves lays a solid foundation for the subsequent preparation of a high-performance waterborne epoxy coating.

Claims

1. A water-based epoxy coating that is resistant to cracking, characterized in that, It includes component A and component B, which are mixed in a mass ratio of 4:1 to 6:1 and then cross-linked and cured. Component A is a curing agent component and component B is an epoxy resin component. The first component, by mass, comprises the following raw materials: 15-25 parts deionized water, 0.5-1.5 parts modified polymeric dispersant, 0.4-0.9 parts multifunctional additive, 0.1-0.3 parts nonionic compatibility promoter, HLB value of fatty alcohol polyoxyethylene ether of 8-12, 1-25 parts optional pigment (if present), 5-30 parts filler, 30-40 parts waterborne epoxy curing agent, 1-3 parts expanded microspheres, 0.2-1 parts wood fiber, 2-8 parts ceramic powder, 0.3-0.5 parts polyether defoamer, polyoxyethylene polyoxypropylene block copolymer, 0.5-1 parts wetting and leveling agent, and acrylate leveling agent with a molecular weight of 2000-5000, tested using gel permeation chromatography with polystyrene as a standard. The B component comprises the following raw materials by mass: 90-95 parts of low molecular weight epoxy resin and 5-10 parts of reactive diluent.

2. The water-based epoxy coating that is not prone to cracking according to claim 1, characterized in that, The deionized water in component A is high-purity deionized water with a conductivity of ≤5μS / cm at 25℃, and the mass fraction is 20-22 parts.

3. The water-based epoxy coating that is not prone to cracking according to claim 1, characterized in that, The modified polymeric dispersant is a polyurethane-grafted acrylate copolymer dispersant, with a mass fraction of 1.0 to 1.2 parts and a number average molecular weight of 5,000 to 10,000. It is tested by gel permeation chromatography, with polystyrene as the standard and tetrahydrofuran as the mobile phase.

4. The water-based epoxy coating that is not prone to cracking according to claim 1, characterized in that, The expanded microspheres are core-shell structured thermally expanded microspheres, with isobutane as the core material and cross-linked acrylic resin as the shell material, in a mass fraction of 2.0–2.5 parts. The initial D50 particle size is 20–30 μm. The expansion ratio at 80–120 °C, measured by a laser particle size analyzer, is 3–5 times. The expansion ratio is the ratio of the expanded particle size to the initial particle size.

5. The water-based epoxy coating that is not prone to cracking according to claim 1, characterized in that, The wood fiber is a coniferous wood fiber modified with γ-glycidoxypropyltrimethoxysilane, with a modification amount of 1-3% of the fiber mass, a fiber length of 100-300 μm, a diameter of 10-30 μm, and a mass fraction of 0.5-0.8 parts by microscopy.

6. The water-based epoxy coating that is not prone to cracking according to claim 1, characterized in that, The ceramic powder is micron-sized alumina ceramic powder with a purity ≥99%, as determined by X-ray fluorescence spectroscopy. The D50 particle size is 1–3 μm, as determined by a laser particle size analyzer. The powder is surface-treated with γ-aminopropyltriethoxysilane at a rate of 2–4% of the ceramic powder mass, or 5–6 parts by mass.

7. The water-based epoxy coating that is not prone to cracking according to claim 1, characterized in that, The low molecular weight epoxy resin in component B is bisphenol A type epoxy resin E-51, the reactive diluent is butyl glycidyl ether, the epoxy value is 0.4-0.6 eq / 100g, and the mass fraction is 7-8 parts.

8. The water-based epoxy coating that is not prone to cracking according to claim 1, characterized in that, The filler is a composite filler composed of talc powder and barite powder in a mass ratio of 1:1, wherein the D50 particle size of talc powder is 5-10 μm and the D50 particle size of barite powder is 20-30 μm, both measured by a laser particle size analyzer, and the total mass fraction is 15-20 parts.

9. A method for preparing a crack-resistant waterborne epoxy coating according to any one of claims 1 to 8, characterized in that, Includes the following steps: (1) Preparation of material A: Deionized water, modified polymeric dispersant, multifunctional additive and nonionic compatibility promoter are added to a container according to the mass fraction, and stirred at 1000 r / min for 15 min at 25-30℃ to obtain material A; (2) Preparation of material B: Mix material A with pigments and fillers, stir at 1200 r / min for 10 min and maintain the temperature at 25℃, then disperse at 2800 r / min for 45 min. Control the viscosity of the material at 25℃ to be 800-1000 mPa·s. Use an NDJ-1 type rotational viscometer with a rotor speed of 60 r / min to obtain material B. (3) Preparation of Material C: Mix Material B with water-based epoxy curing agent, expanded microspheres, wood fiber, ceramic powder and polyether defoamer, stir at 1200 r / min for 10 min until the bubble volume fraction is ≤0.1%, test by image analysis method, take the average value of 3 parallel samples, add wetting and leveling agent, stir at 1000 r / min for 15 min at 20-25℃ to obtain Material C: (4) Preparation of component A: Filter material C through a 120-mesh nylon filter cloth that has been boiled and dried in deionized water at 80℃, and collect the filtrate: (5) Preparation of component B: Low molecular weight epoxy resin and reactive diluent are stirred at 600 r / min for 20 min at 30℃. The viscosity of the system at 25℃ is controlled to be 500-600 mPa·s. NDJ-1 type rotational viscometer is used with a rotor speed of 60 r / min to obtain component B. (6) Mixed finished product: Mix component A and component B in a mass ratio of 4:1 to 6:1 and stir at 900 r / min for 8 min to obtain waterborne epoxy coating.

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