High-weatherability water-based epoxy-modified polyacrylate coating and preparation method thereof

Abstract

The application discloses a high-weather-resistance water-based epoxy modified polyacrylate coating and a preparation method thereof. The coating is water-based and single-component, can be cured at room temperature, and is composed of a hydrogenated epoxy emulsion, a polyacrylate emulsion, sericite, titanium dioxide, modified silane, water and other water-based additives. The coating is convenient to operate, has low VOC emission during coating, and is a green and environment-friendly anticorrosive coating product.

Description

A high weather-resistant waterborne epoxy-modified polyacrylate coating and its preparation method Technical Field

[0001] This invention relates to the field of coating technology, specifically to a single-component, self-drying, waterborne epoxy-modified polyacrylate coating that is UV resistant, chemical resistant, corrosion resistant, has high hardness, is tack-resistant, and can adhere to multiple substrates, and its preparation method. Background Technology

[0002] Steel is the most widely used metallic material in modern society. The losses caused by steel corrosion are not only manifested in damage to the material's shape, color, and mechanical properties, but more importantly, they reduce the quality grade of products and projects, impair precision and sensitivity, affect their usability, and even render them unusable. In rare cases, it can even lead to major accidents resulting in the destruction of machinery and loss of life. The corrosion process of steel is very complex and can be divided into chemical corrosion and electrochemical corrosion based on its mechanism. Chemical corrosion occurs in non-electrolyte environments, and no current is generated during the corrosion process; electrochemical corrosion occurs in electrolyte environments (such as rainwater, surface water, seawater, and various acid, alkali, and salt solutions), and electron transfer occurs during the corrosion process. The mechanism of electrochemical corrosion also varies in different media environments. When steel is in an acidic liquid medium, hydrogen evolution corrosion occurs; when steel is in a neutral or alkaline liquid medium, oxygen absorption corrosion occurs. Blocking the chemical and electrochemical corrosion processes is an important means of achieving steel corrosion prevention. Among various corrosion blocking strategies, anti-corrosion coatings are the most widely used steel protection solution due to their low cost, ease of operation, and wide applicability. Commonly used anti-corrosion coatings include solvent-based alkyd coatings, solvent-based polyacrylate coatings, solvent-based polyurethane coatings, solvent-based epoxy coatings, and solvent-based chlorinated polyolefin coatings. These coatings require the use of large amounts of volatile organic solvents such as benzene, esters, alcohols, or ketones during their preparation and application, resulting in poor environmental friendliness.

[0003] However, with the introduction of the "Air Pollution Prevention and Control Action Plan," the national policy on limiting volatile organic compounds (VOCs) emissions has been rapidly tightened, and detailed management measures such as emission limits and consumption taxes on coatings have been quickly implemented. Reducing the use of volatile organic solvents has become an irreversible transformation direction for anti-corrosion coatings. To meet this challenge, it is imperative to use water instead of organic solvents as the dispersion medium for coatings and develop green and environmentally friendly water-based anti-corrosion coatings. Currently, the industry has made many attempts in the water-based field, and a large number of water-based anti-corrosion coating products have been launched. Among them, single-component self-drying water-based coatings have gained a high market share due to their advantages such as low cost, no pot life, convenient construction, and low curing energy consumption. Unfortunately, due to the chemical composition of the coating material (more hydrophilic units) and curing characteristics (lower coating density), the corrosion protection level of this type of product is relatively low, and it is mostly suitable for light anti-corrosion coating of steel.

[0004] Currently, the main problems that need to be improved in single-component self-drying water-based anti-corrosion coatings are:

[0005] (1) Thermoplastic waterborne polyacrylate coating: gloss and hardness are difficult to balance; poor pigment coverage and low shielding efficiency, making it impossible to prepare coatings with high pigment-to-binder ratio; hot-sticky and cold-brittle, easy to re-stick when stacked at high temperature, and easy to crack when applied at low temperature; general adhesion, requiring high treatment of substrate; not resistant to oil, not resistant to organic solvents, and not suitable for coating on rusty surfaces.

[0006] (2) Oxidative crosslinking waterborne alkyd and epoxy ester coatings: require the addition of more alcohol ether solvents and amine neutralizers, have higher odor and VOC; have a long hard drying cycle, are not suitable for thick coatings, and cannot be quickly packaged; have low early strength and are not resistant to stacking; have poor gloss retention and are prone to losing gloss after exposure to sunlight; have a high water absorption rate and are not resistant to acids or alkalis.

[0007] (3) Waterborne silicate coating: The coating has high porosity, low gloss and poor decorative properties; it has strict requirements for substrate treatment, and improper treatment can easily cause cracking and peeling; the coating has high rigidity and is not impact resistant; the coating has poor stability and short shelf life.

[0008] In summary, only by starting with the design of film-forming resins and fundamentally improving the film-forming properties and physicochemical characteristics of water-based single-component self-drying coatings can their corrosive medium shielding efficiency and mechanical strength be significantly improved, thereby achieving the goals of extending the coating's protective lifespan, broadening product applications, and enhancing product competitiveness. Summary of the Invention

[0009] The purpose of this invention is to provide a single-component, self-drying, waterborne epoxy-modified polyacrylate coating that is UV resistant, chemical resistant, corrosion resistant, has high hardness, is tack-resistant, and can adhere to multiple substrates, as well as its preparation method.

[0010] The objective of this invention can be achieved through the following technical solutions:

[0011] A high weather-resistant waterborne epoxy-modified polyacrylate coating, comprising the following components:

[0012]

[0013]

[0014] In some specific technical solutions, the coating is composed of the following components:

[0015]

[0016] In the technical solution of this invention, the hydrogenated epoxy emulsion is prepared through the following steps:

[0017] S1: Mix bisphenol A type epoxy resin, hydrogenated bisphenol A type epoxy resin and propylene glycol methyl ether, heat to dissolve and stir evenly, cool to 30-40℃, slowly add 4,4'-diaminodicyclohexylmethane solution, after the addition is complete, heat to 70-80℃ and react for 1-3 hours.

[0018] S2: After the reaction is complete, cool down to 30-40℃, add polyethylene glycol diglycidyl ether and stir well, then slowly add ethylenediamine solution, and after the addition is complete, heat up to 70-80℃ and continue the reaction for 3-5 hours.

[0019] S3: After the reaction is complete, add some water at a temperature of 70-80℃ and under stirring and disperse evenly. Then add the remaining water and continue stirring. After the addition is complete, cool and filter to obtain hydrogenated epoxy emulsion.

[0020] Preferably, the solvent used in the 4,4'-diaminodicyclohexylmethane solution and the ethylenediamine solution is propylene glycol methyl ether, and the concentrations of the 4,4'-diaminodicyclohexylmethane solution and the ethylenediamine solution are both 15-25 wt%.

[0021] In some more preferred technical solutions, the mass ratio of bisphenol A epoxy resin to water is 5-8:45-49, and the amount of water added in the first step is 40-80% of the total components.

[0022] In the above method for preparing hydrogenated epoxy emulsion, the components are as follows:

[0023]

[0024]

[0025] In the above method for preparing hydrogenated epoxy emulsion, the bisphenol A type epoxy resin is E-14 bisphenol A type epoxy resin; the hydrogenated bisphenol A type epoxy resin is TaiLuck-ST 3000 epoxy resin from Dongdu Chemical; and the molecular weight of the polyethylene glycol diglycidyl ether is 450-700.

[0026] In the technical solution of this invention, the polyacrylate emulsion is Lubrizol Carboset CR-3090 acrylic emulsion.

[0027] In the technical solution of this invention, the sericite is Gree GA-6 wet-process sericite with an average particle size of 15±1.5μm.

[0028] In the technical solution of this invention, the wetting and dispersing agent is Dispers 755W; the defoamer is Foamex 810; the substrate wetting agent is Wet KL 245; the anti-flash rust additive is NALZIN FA179; the modified wax emulsion is AQUATIX 8421; the modified silane is Coatosil MP200; and the thickener is RHEOLATE 299.

[0029] A method for preparing the above-mentioned high weather-resistant waterborne epoxy-modified polyacrylate coating, the method comprising the following steps:

[0030] S1: Add hydrogenated epoxy emulsion, water, and wetting and dispersing agent to the paint mixing tank and stir evenly; add titanium dioxide, sericite, and defoamer, disperse evenly at high speed, and then transfer to a sand mill to grind until the slurry fineness is less than 25μm;

[0031] S2: Add the obtained slurry to the polyacrylate emulsion and stir evenly; add dipropylene glycol butyl ether, substrate wetting agent, anti-flash rust additive, modified wax emulsion, and modified silane, and continue stirring; add thickener, adjust the system viscosity to 80-100 KU, filter, and you can get a high weather-resistant waterborne epoxy modified polyacrylate coating.

[0032] The beneficial effects of this invention are:

[0033] This invention employs a novel "polyacrylate emulsion / hydrogenated epoxy emulsion" film-forming system. The CR-3090 polyacrylate emulsion has a low particle size and excellent film-forming properties, and can be cured to obtain a thermoplastic coating with high shielding characteristics. The self-synthesized hydrogenated epoxy emulsion has high hardness, good toughness, and strong adhesion. The two have excellent compatibility. When combined, the hydrogenated epoxy significantly increases the softening point temperature of the thermoplastic polyacrylate coating, improves the mechanical strength and adhesion of the coating, and does not affect the flexibility of the coating. Furthermore, this hydrogenated epoxy emulsion also possesses excellent mechanical stability (shear resistance) and pigment encapsulation properties, can participate in pigment grinding, and can reduce the number of hydrophilic units in the coating system by reducing the amount of wetting and dispersing agents, thus improving the chemical resistance of the coating. Because a hydrogenated epoxy system is selected, epoxy doping does not affect the coating's UV aging resistance, meeting the requirements for high-durability outdoor protection.

[0034] The present invention also preferentially uses GA-6 wet-process sericite (average particle size 15μm) with a unique aspect ratio and lamellar structure as a shielding filler. On the one hand, it can effectively extend the erosion path of corrosive media within the coating and enhance the corrosion protection effect; on the other hand, it can block ultraviolet rays, reduce coating aging, and at the same time, it does not affect the gloss and appearance of the coating.

[0035] The high weather-resistant waterborne epoxy-modified polyacrylate coating disclosed in this invention has the characteristics of UV resistance, chemical resistance, corrosion resistance, high hardness, and adhesion to multiple substrates. It is a novel single-component self-drying waterborne anti-corrosion coating solution. Detailed Implementation

[0036] The present invention will be further described below with reference to embodiments, but the scope of protection of the present invention is not limited thereto:

[0037] The sources of some of the raw materials in this embodiment of the invention are as follows:

[0038] Dongdu Chemical TaiLuck-ST 3000 epoxy resin

[0039] https: / / tailuck.cn.china.cn / supply / 3985070514.html

[0040] Lubrizol Carboset CR-3090 Acrylic Emulsion

[0041] https: / / cn.lubrizol.com / Coatings / Products / Carboset-CR-3090#

[0042] Gree GA-6 Wet Processed Sericite

[0043] http: / / www.chinagrea.com / p_display.php?id=1

[0044] Dispers 755W Wetting and Dispersing Agent

[0045] https: / / fsss168.com / product / 1754.html

[0046] Dego Foamex 810 defoamer

[0047] https: / / b2b.baidu.com / land?id=1d39ae52ec3087958732fbd760d4a74c10TEGOWet KL 245 Substrate Wetting Agent

[0048] https: / / b2b.baidu.com / land?id=e385b1bff812d60be157d893996b82b610

[0049] Haiming Sideqian NALZIN FA 179 Anti-Flash Rust Agent

[0050] https: / / www.4006787252.com / article_read_6408.html

[0051] BYK AQUATIX 8421

[0052] https: / / detail.1688.com / offer / 688076518614.html

[0053] Momentive Coatosil MP200

[0054] https: / / b2b.baidu.com / land?id=815aac343551a7c1858e8ad7fd96f0d910

[0055] RHEOLATE 299 Thickener

[0056] https: / / www.china.cn / fangchenji / 5016459926.html

[0057] The preparation steps of the high weather-resistant waterborne epoxy-modified polyacrylate coatings in Examples 1-3 (material ratios are shown in Table 1) and Comparative Examples 1-5 are as follows (test results are shown in Tables 2 and 3):

[0058] (1) Preparation of hydrogenated epoxy emulsion:

[0059] First, add E-14 bisphenol A epoxy resin, TaiLuck-ST 3000 hydrogenated bisphenol A epoxy resin, and propylene glycol methyl ether to the reactor. Heat to 85°C to completely melt the solids and stir until homogeneous. Cool to 35°C and slowly add a propylene glycol methyl ether solution of 4,4'-diaminodicyclohexylmethane (15% by mass) over 0.5 hours. Increase the temperature to 75°C and stir for 2 hours. Cool to 35°C and add polyethylene glycol diglycidyl ether (number average molecular weight approximately 570), stirring until homogeneous. Slowly add a propylene glycol methyl ether solution of ethylenediamine (15% by mass) over 1 hour. Increase the temperature to 75°C and stir for 4 hours. Maintain 75°C and slowly add 3 / 5 of the water at a stirring speed of 1500 rpm over 1 hour. Increase the stirring speed to 2200 rpm and disperse at high speed for 2 hours. Reduce the stirring speed to 600 rpm, add the remaining water, and stir for 30 minutes. Cool and filter to obtain the hydrogenated epoxy emulsion.

[0060] (2) Preparation of waterborne epoxy-modified polyacrylate coatings:

[0061] Hydrogenated epoxy emulsion, water, and Dispers 755W wetting and dispersing agent were added to a paint mixing tank and stirred until homogeneous. Titanium dioxide, GA-6 wet-process sericite, and Foamex 810 defoamer were added and dispersed at high speed until homogeneous, free of lumps and agglomerates. The mixture was then transferred to a sand mill and ground until the slurry fineness was less than 25 μm. The obtained slurry was added to Carboset CR-3090 polyacrylate emulsion and stirred until homogeneous. Dipropylene glycol butyl ether, Wet KL 245 substrate wetting agent, FA 179 anti-flash rust additive, AQUATIX 8421 modified wax emulsion, and Coatosil MP200 modified silane were added and stirring continued. RHEOLATE 299 thickener was added to adjust the viscosity of the system to 80-100 KU. The mixture was then filtered to obtain a waterborne epoxy-modified polyacrylate coating.

[0062] Material proportions for comparative examples 1-5:

[0063] Comparative Example 1: Replace “30 parts by weight of Carboset CR-3090 acrylic emulsion and 25 parts by weight of hydrogenated epoxy emulsion” in Example 1 with “55 parts by weight of Carboset CR-3090 acrylic emulsion”, and keep the other material ratios the same as in Example 1.

[0064] Comparative Example 2: The “27 parts by weight of TaiLuck-ST 3000 epoxy resin” in Example 1 was replaced with “27 parts by weight of E-44 bisphenol A type epoxy resin” (the epoxy equivalent is similar to that of TaiLuck-ST 3000), and the proportions of the remaining materials were the same as in Example 1.

[0065] Comparative Example 3: The "5.5 parts by weight of 4,4'-diaminodicyclohexylmethane" in Example 1 was replaced with "1.57 parts by weight of ethylenediamine", and the proportions of the remaining materials were the same as in Example 1.

[0066] Comparative Example 4: Replace “30 parts by weight of Carboset CR-3090 acrylic emulsion” in Example 1 with “30 parts by weight of Carboset CR-728 acrylic emulsion”, and keep the other material ratios the same as in Example 1.

[0067] Comparative Example 5: Replace “0.5 parts by weight of Coatosil MP200 modified silane” in Example 1 with “0.5 parts by weight of γ-glycidyl etheroxypropyltrimethoxysilane”, and keep the other material ratios the same as in Example 1.

[0068] Table 1. Material addition amounts (parts by mass) for Examples 1-3

[0069]

[0070] Table 2 Main technical indicators of waterborne epoxy-modified polyacrylate coatings in Examples 1-3

[0071]

[0072]

[0073] Note: The test panel is a single-coat plate with a dry film thickness of 80±5μm.

[0074] Table 3. Main technical indicators of waterborne epoxy-modified polyacrylate coatings (Comparative Examples 1-5) (The performance indicators were tested using the same methods as above).

[0075]

[0076]

[0077] Test results (Table 2) show that Examples 1-3 all yielded waterborne epoxy-modified polyacrylate coatings that are room temperature self-drying, chemical resistant, corrosion resistant, have high hardness, are resistant to tackiness, have excellent adhesion, and are resistant to UV aging.

[0078] The doping of hydrogenated epoxy resin is crucial to the coating performance. Without epoxy doping (Comparative Example 1), the coating's hardness and anti-tack properties will significantly decrease, failing to meet the requirements of rapid packaging on assembly lines and unable to withstand various chemicals at 50°C. Furthermore, problems such as decreased adhesion and salt spray resistance will also occur.

[0079] Secondly, the structural design of the epoxy emulsion is also crucial. The types and ratios of epoxy resin and amine must be strictly controlled to obtain modified products with specific molecular weights and softening points. If "conventional bisphenol A epoxy resin" (Comparative Example 2) is used instead of "hydrogenated bisphenol A epoxy resin," the rigidity of the epoxy component will increase, reducing the coating's impact resistance. Simultaneously, high rigidity affects epoxy resin emulsification, leading to increased emulsion particle size, reduced coating density, and consequently decreased coating gloss, acid resistance, and salt spray resistance. Furthermore, excessive use of bisphenol A epoxy resin will severely impact the coating's UV aging resistance. After QUV testing, the coating will exhibit severe gloss loss and chalking. If "ethylenediamine" (Comparative Example 3) is used instead of "4,4'-diaminodicyclohexylmethane," the hardness of the epoxy component will decrease. This will affect the coating's softening point temperature, resulting in slower hardness build-up, heat-induced tackiness, and inability to withstand acid and alkali corrosion at 50°C. In addition, the ratio of epoxy resin to diamine also needs to be strictly controlled, otherwise it may result in the product having too high a molecular weight and being unable to emulsify properly, or the product having too low a molecular weight and lacking coating reinforcement function.

[0080] Third, the selection of the polyacrylate emulsion is also crucial. Carboset CR-3090 acrylic emulsion has the best compatibility with hydrogenated epoxy emulsion, and the mixture of the two can produce a uniform, dense, and full-bodied waterborne coating. If it is replaced with a conventional polyacrylate emulsion (Comparative Example 2), the coating density will be significantly reduced, and the gloss, water resistance, acid resistance, and salt spray resistance (see Table 3) will also decrease. At the same time, it will also affect the adhesion of the coating to the metal surface.

[0081] Fourth, modified silanes are used to further improve the bonding strength between the coating resin and the metal and filler, and their selection requires careful consideration. On the one hand, the selected silane needs to have suitable stability in the aqueous phase to ensure that the hydrolysis process of the silane occurs during the film-forming stage. On the other hand, the selected silane needs to have good compatibility with the coating resin to ensure a strong bond with the resin without affecting the coating gloss. Coatosil MP200 modified silane has high stability and adhesion-promoting function. If "Coatosil MP200 modified silane" is replaced with a traditional epoxy silane, such as γ-glycidoxypropyltrimethoxysilane (Comparative Example 5), this silane will not be stable in the aqueous phase for a long time, failing to improve the adhesion of the substrate and introducing new defects into the coating. Test results show that the adhesion, gloss, and protective performance of the coating are all reduced after using γ-glycidoxypropyltrimethoxysilane.

[0082] Finally, the other materials disclosed in this invention were also selected through extensive experimentation, and arbitrary substitution would affect the overall performance of the coating. For example, the preferred GA-6 wet-process sericite flake filler has strong compatibility with the film-forming system of this invention. The type, particle size, and ratio of the filler have been strictly screened and cannot be easily replaced. If the GA-6 wet-process sericite (15±1.5μm) is replaced in equal amounts with large-particle-size Gree GM-2 mica powder (particle size ≤24μm), the shielding efficiency of the coating will decrease, and the acid and alkali resistance and salt spray resistance will also decline.

Claims

1. A high weather-resistant waterborne epoxy-modified polyacrylate coating, characterized in that... The coating is composed of the following components: 15-35 parts hydrogenated epoxy emulsion, 20-50 parts polyacrylate emulsion, 1-8 parts sericite, 10-35 parts titanium dioxide, 0.2-1.5 parts wetting and dispersing agent, 0.1-0.5 parts defoamer, 2-8 parts dipropylene glycol butyl ether, 0.1-0.5 parts substrate wetting agent, 0.3-1.5 parts anti-flash rust additive, 1-6 parts modified wax emulsion, 0.1-3 parts modified silane, 0.1-3 parts thickener, and 5-18 parts water. The hydrogenated epoxy emulsion is prepared by the following steps: S1: Bisphenol A type epoxy resin, hydrogenated bisphenol A type epoxy resin, and propylene glycol methyl ether are mixed, heated to dissolve, and stirred evenly. The mixture is then cooled to 30-40 °C, and 4,4'-diaminodicyclohexylmethane solution is slowly added. After the addition is complete, the temperature is raised to 70-80 °C and reacted for 1-3 h; S2: After the reaction is completed, the temperature is lowered to 30-40 °C. At ℃, polyethylene glycol diglycidyl ether is added and stirred until homogeneous. Then, ethylenediamine solution is slowly added. After the addition is complete, the temperature is raised to 70~80 ℃ and the reaction continues for 3~5 h. S3: After the reaction is complete, water is added and dispersed evenly at 70~80 ℃ with stirring. Then, water is added again and stirred until homogeneous. After the addition is complete, the mixture is cooled and filtered to obtain hydrogenated epoxy emulsion. The polyacrylate emulsion is Lubrizol Carboset CR-3090 acrylic emulsion. The sericite is Gree GA-6 wet sericite with an average particle size of 15±1.5 μm. The modified silane is Momentive Coatosil MP200.

2. The high weather-resistant waterborne epoxy-modified polyacrylate coating according to claim 1, characterized in that... The coating is composed of the following components: 20-30 parts hydrogenated epoxy emulsion, 20-40 parts polyacrylate emulsion, 1-5 parts sericite, 15-30 parts titanium dioxide, 0.3-0.8 parts wetting and dispersing agent, 0.1-0.3 parts defoamer, 3-6 parts dipropylene glycol butyl ether, 0.1-0.3 parts substrate wetting agent, 0.3-1 parts anti-flash rust additive, 1-5 parts modified wax emulsion, 0.1-2 parts modified silane, 0.1-2 parts thickener, and 5-15 parts water.

3. The high weather-resistant waterborne epoxy-modified polyacrylate coating according to claim 1, characterized in that... The solvent used in the 4,4'-diaminodicyclohexylmethane solution and the ethylenediamine solution in the hydrogenated epoxy emulsion is propylene glycol methyl ether, and the concentrations of the 4,4'-diaminodicyclohexylmethane solution and the ethylenediamine solution are both 15~25 wt%.

4. The high weather-resistant waterborne epoxy-modified polyacrylate coating according to claim 3, characterized in that: Bisphenol A type epoxy resin 5-8 parts, hydrogenated bisphenol A type epoxy resin 25-30 parts, propylene glycol methyl ether 6-10 parts, 4,4'-diaminodicyclohexylmethane 4-7 parts, polyethylene glycol diglycidyl ether 4-8 parts, ethylenediamine 0.2-0.9 parts, water 45-49 parts.

5. The high weather-resistant waterborne epoxy-modified polyacrylate coating according to claim 3, characterized in that... The bisphenol A type epoxy resin is E-14 bisphenol A type epoxy resin, the hydrogenated bisphenol A type epoxy resin is TaiLuck-ST3000 epoxy resin from Dongdu Chemical, and the molecular weight of the polyethylene glycol diglycidyl ether is 450~700.

6. The high weather-resistant waterborne epoxy-modified polyacrylate coating according to claim 1, characterized in that... The wetting and dispersing agent is Dispers 755W; the defoamer is Foamex 810; the substrate wetting agent is WetKL 245; the anti-flash rust additive is NALZIN FA 179; the modified wax emulsion is AQUATIX 8421; and the thickener is RHEOLATE 299.

7. A method for preparing a high weather-resistant waterborne epoxy-modified polyacrylate coating as described in claim 1, characterized in that: The method includes the following steps: S1: Add hydrogenated epoxy emulsion, water, and wetting and dispersing agent to a paint mixing tank and stir evenly; add titanium dioxide, sericite, and defoamer, disperse evenly at high speed, and then transfer to a sand mill to grind until the slurry fineness is less than 25 μm; S2: Add the obtained slurry to polyacrylate emulsion and stir evenly; add dipropylene glycol butyl ether, substrate wetting agent, anti-flash rust additive, modified wax emulsion, and modified silane, and continue stirring; add thickener, adjust the system viscosity to 80~100 KU, filter, and a high weather-resistant waterborne epoxy modified polyacrylate coating can be obtained.

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