Aqueous acrylic coating and method for its preparation and use

Abstract

The present application relates to the technical field of paint, in particular to water-based acrylic paint, its preparation method and application. The water-based acrylic paint provided by the present application is mainly applied to the finishing coating of metal frame; the coating can reduce the number of surface coating construction, and the coating belongs to a water-based system, and the biggest difference from an oily system is environmental protection; the coating can reduce the emission of VOCs gas to the largest extent during construction, reduce the central waste gas and dust collection treatment bearing capacity, and truly realize good environmental adaptability without affecting the performance of the coating, which is beneficial to the environment and the health of construction personnel. In addition, the coating formed by the water-based acrylic paint provided by the present application has high hardness, impact resistance, adhesion and corrosion resistance, and can adapt to the application requirements of various environments, and is especially suitable for metal frame coating and rapid coating repair.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to water-based acrylic coatings, their preparation methods, and applications. Background Technology

[0002] Industrial-grade corrosion protection has always been a major trend in coating development, as the coating industry is one of the main sources of volatile organic compound (VOC) emissions. Traditional solvent-based coatings generate high concentrations and large volumes of organic waste gas during production and application, which diffuses into the atmosphere, causing irreversible damage to the environment and human health. Furthermore, solvent-based coatings are generally two-component, containing a main component and a curing agent. Before use, the two components need to be mixed and stirred thoroughly, a cumbersome process that wastes considerable preparation time. During the drying process, due to the inherent properties of organic systems, solvents evaporate slowly, resulting in long drying times and a viscous coating film that is easily damaged during initial drying. In conclusion, developing an environmentally friendly, economically valuable, and easy-to-use water-based coating is a necessity for the development of the coating industry.

[0003] Waterborne acrylic coatings are a single-component type, using waterborne acrylic emulsions as their resin component. They are applied by spraying or brushing, offering simple operation and saving significant amounts of coating equipment compared to traditional electrophoretic coating and topcoat application methods, thus reducing investment costs. The coatings are water-based and environmentally friendly, with strong biocompatibility, and produce virtually no exhaust fumes before and after application, reducing investment in environmental protection facilities and optimizing the construction environment. Therefore, developing a waterborne coating that meets specific requirements is a necessary step in development. However, there are currently no good guidelines on how to modify this type of waterborne coating to better suit metal surfaces and various application scenarios, ensuring both corrosion resistance and high physical properties of the coating. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide water-based acrylic coatings, their preparation methods and applications. The water-based acrylic coatings provided by the present invention have good stability, and the construction process is not only simple but also green and energy-saving. The resulting coating has high hardness, impact resistance, adhesion and corrosion resistance, and can adapt to the application requirements of various environments, especially suitable for metal frame coating and rapid coating repair.

[0005] This invention provides an aqueous acrylic coating comprising, by weight percentage:

[0006] Water: 6%~12%;

[0007] Dispersant: 0.1%~1.0%; the dispersant is one or more of the following: Shengshi RD-9786, BASF4575, BYK-191, Shenzhu Chemical SN-1729, and HY-740W;

[0008] Polyether-modified silicone defoamer: 0.1%~0.5%;

[0009] Stabilizer: 0.5%~1.5%;

[0010] Thickener: 0.1%~1.5%, wherein the thickener is selected from one of hydrophilic fumed silica or polyurethane;

[0011] Pigment: 0.5%~2.0%,

[0012] Filler: 30%~45%,

[0013] Film-forming aids: 0%~3.0%;

[0014] The modified acrylic resin emulsion comprises 50% to 65%, wherein the modified acrylic resin has monomer units derived from propylene, monomer units derived from methyl methacrylate, monomer units derived from styrene, monomer units derived from ethyl acrylate, monomer units derived from butyl acrylate, and monomer units derived from hydroxyethyl acrylate.

[0015] The waterborne acrylic coating provided by this invention comprises an emulsion of modified acrylic resin, wherein the modified acrylic resin is polymerized by polymerizing monomers of propylene, methyl methacrylate (MMA), styrene (St), ethyl acrylate (EA), butyl acrylate (BA), and hydroxyethyl acrylate (HEV) in a specific ratio. MMA and St are hard monomers, EA and BA are soft monomers, and HEV is a functional monomer. Introducing carboxyl, benzene, and hydroxyl groups into the original system, through grafting and interpenetrating network polymerization with the original structure, effectively improves the hydrophilicity and polarity of the resin. Through covalent bonding, it improves the resin's adhesion. The high molecular weight polymerization helps improve the resin's hardness and durability, enhancing the coating's weather resistance. Preferably, the pH of the modified acrylic resin emulsion of this invention is 6-8.

[0016] Preferably, the modified acrylic resin of the present invention has monomer units derived from propylene, methyl methacrylate, styrene, ethyl acrylate, butyl acrylate and hydroxyethyl acrylate in a molar ratio of 30:(6~7):(4~6):(6~7):(4~6):(1~4).

[0017] More preferably, the modified acrylic resin of the present invention has monomer units derived from propylene, methyl methacrylate, styrene, ethyl acrylate, butyl acrylate and hydroxyethyl acrylate in a molar ratio of 30:(6~7):(4.5~5.5):(6~7):(4.5~5.5):(1~4).

[0018] The waterborne acrylic coating provided by this invention includes a variety of additives, which effectively improve the alternating properties of the coating during manufacturing, storage, transportation, and use. Among these, the waterborne acrylic coating provided by this invention includes a dispersant, which is one or more of the following: Shengshi RD-9786, BASF4575, BYK-191, Shenzhu Chemical SN-1729, and HY-740W. The dispersant of this invention, through its amphiphilic groups, adsorbs onto the surface of solid particles, reducing the friction and cohesion between powders, making the particles easier to surround and disperse by solvent water molecules, thus facilitating grinding and resin emulsion encapsulation.

[0019] The water-based acrylic coating provided by this invention includes a polyether-modified silicone defoamer. During the manufacturing process, the defoamer achieves its defoaming ability by reducing the surface tension between liquids and between liquids and solids. Preferably, the polyether-modified silicone defoamer is selected from one of Hengxin THIX-299, Nanhui CI-3125, Digo 825, Digo 3062, and BYK-019.

[0020] The waterborne acrylic coating provided by this invention includes a stabilizer, which effectively prevents the slurry from separating and agglomerating in the system by forming a stable complex. Preferably, the stabilizer is selected from one or more of hydroxypropyl methylcellulose, hydroxybenzoic acid, sorbitol polyoxyethylene ether, sodium carboxymethyl cellulose, and propylene glycol block polyether.

[0021] The waterborne acrylic coating provided by this invention includes a thickener. The thickener forms a three-dimensional network structure through strong stirring and shearing, enhancing the mutual adsorption and cross-linking between molecules. This dispersion effect can hinder the movement between particles, reduce the fluidity of the solution, and increase the viscosity of the coating. Preferably, the thickener is selected from one or more of hydrophilic fumed silica or polyurethane types.

[0022] The water-based acrylic coating provided by this invention further includes pigments and fillers. The addition of the fillers described in this invention can alter the physical properties of the coating film; preferably, the fillers are selected from one or more of talc, barium sulfate, mica powder, and calcium carbonate; the purity of the fillers is preferably 95% or higher, more preferably 98% or higher. The pigments described in this invention are inorganic or organic pigments; preferably, the pigments are selected from one or more of carbon black, iron oxide red, phthalocyanine blue, titanium dioxide, and chrome green.

[0023] The waterborne acrylic coating provided by this invention also includes an optional film-forming aid. The film-forming aid described in this invention can be selectively added or omitted. Adding a film-forming aid can significantly reduce the film-forming time of the coating and expand its usability in cold-climate environments. For outdoor construction in low-temperature scenarios, adding a film-forming aid can be considered to accelerate surface drying and hard drying. Preferably, the film-forming aid is selected from one of propylene glycol methyl ether acetate, dodecyl alcohol ester, and propylene glycol methyl ether acetate. If a film-forming aid is added, the waterborne acrylic coating of this invention preferably includes 0.1% to 0.3% of the film-forming aid.

[0024] The waterborne acrylic coating provided by this invention is a single-component waterborne acrylic coating. Through the synergistic effect of modified acrylic resin emulsion, additives and fillers, it can effectively improve the performance and strain of the coating film, making the resulting single-component waterborne acrylic coating more suitable for metal surfaces and ultimately replacing traditional oil-based coatings.

[0025] The present invention also provides a method for preparing any of the above-mentioned waterborne acrylic coatings, comprising the following steps: preparing a slurry with a particle size of 10 μm to 100 μm by mixing water, dispersant, polyether-modified silicone defoamer, stabilizer, thickener, pigment and filler; mixing the modified acrylic resin emulsion, optional film-forming aid and the slurry to obtain the waterborne acrylic coating.

[0026] This invention first prepares a homogenate with a particle size of 10 μm to 100 μm by mixing water, dispersant, polyether-modified silicone defoamer, stabilizer, thickener, pigment, and filler in a specific mass ratio. Specifically, the invention first mixes and stirs the water, dispersant, polyether-modified silicone defoamer, stabilizer, thickener, pigment, and filler in a uniform mass ratio to obtain a slurry. Then, the obtained slurry is subjected to cyclic milling to obtain a homogenate with a particle size of 10 μm to 100 μm. The stirring speed is 800 rpm to 1800 rpm, the stirring time is 1 h to 2 h, the stirring temperature is 30℃ to 40℃, the cyclic milling time is 1 h to 1.5 h, the cyclic milling speed is 800 rpm to 900 rpm, and the cyclic milling temperature is 30℃ to 40℃. More specifically, this invention involves mixing water, dispersant, polyether-modified silicone defoamer, stabilizer, thickener, pigment, and filler in a slurry mixing container. The slurry mixing container is a 1000L stainless steel tank with a water-cooled jacket. The mixing uses a single-shaft double-disc gear with a diameter of 40 mm to 50 mm, and the slurry temperature is controlled below 40°C during the mixing process. The circulating grinding equipment uses a 40L horizontal grinder with a water-cooled jacket, and the grinding media consists of zirconium beads with a purity of over 95% and diameters of 2 mm and 5 mm mixed in a 6:4 mass ratio. The grinding temperature is controlled below 40°C.

[0027] After obtaining a homogenate, the present invention mixes a modified acrylic resin emulsion, an optional film-forming aid, and the homogenate to obtain a water-based acrylic coating. Specifically, the modified acrylic resin emulsion, the film-forming aid, and the homogenate are mixed and stirred evenly to obtain a water-based acrylic coating; the stirring speed is 400 rpm to 600 rpm, and the stirring time is 1 h to 2 h. More specifically, if no film-forming aid is added, the modified acrylic resin emulsion and the homogenate are mixed and stirred evenly at 400 rpm to 600 rpm for 1 h to 2 h to obtain a water-based acrylic coating; if a film-forming aid is added, the modified acrylic resin emulsion, the homogenate, and the film-forming aid are mixed and stirred evenly at 400 rpm to 600 rpm for 1 h to 2 h to obtain a water-based acrylic coating. The pH of the modified acrylic resin emulsion is pre-adjusted to 6 to 8, and the stirring speed is 200 rpm to 400 rpm to maintain defoaming and homogenization of the emulsion. The main production line preparation method in this invention involves uniformly mixing the modified acrylic resin emulsion with a homogenate. Specifically, this invention uses a 1500L stainless steel tank as the pre-mixing vessel for the modified acrylic resin emulsion. The stirring in this invention utilizes a single-shaft, double-disc gear with a diameter of 40 mm to 50 mm.

[0028] In some embodiments of the present invention, the method for preparing any of the above-described waterborne acrylic coatings includes the following steps:

[0029] Step S1: Water, dispersant, polyether-modified silicone defoamer, stabilizer, thickener, and pigment are sequentially added to a 1000L stainless steel tank with a cooling water jacket, and stirred using a single-axis serrated double-disc agitator; the stirring time is 0.5 h to 1 h, and the stirring speed is 700 rpm to 900 rpm; the tank temperature is controlled at 30℃ to 40℃; wherein, the single-axis serrated double-disc agitator is made of stainless steel, with a serrated shape, and a diameter of 40 mm to 50 mm;

[0030] Step S2: While stirring, add filler in batches to the tank from Step S1. The stirring speed is gradually increased to 1200 rpm to 1800 rpm, and high-speed stirring is maintained to disperse and mix the mixture to obtain a slurry. The stirring time is controlled to be 0.5 h. The tank temperature is controlled to be 30℃ to 40℃.

[0031] Step S3-1: The uniformly mixed slurry obtained in step S2 is fed into a 40L horizontal grinder through a pipeline. The grinding process is started, and the upward slurry is re-entered into the tank of step S1 for circulating grinding. The stirring speed in the tank of step S1 is reduced to 800 rpm~1000 rpm, the grinding speed is controlled at 800 rpm~900 rpm, and the temperature of the tank of step S1 and the horizontal grinder is controlled at 30℃~40℃. The circulating grinding time is 1 h~1.5 h, resulting in a homogeneous slurry with a particle size of 10 μm~100 μm. The grinding media of the horizontal grinder is a mixture of zirconium beads with a purity of 95% or higher, a mass ratio of 6:4, and diameters of 2 mm and 5 mm.

[0032] Step S3-2: Adjust the pH of the modified acrylic resin emulsion to 6-8 in a 1500 stainless steel dispersion tank, and stir at 200-400 rpm to maintain defoaming and homogenization of the emulsion.

[0033] Step S4: Transfer the homogenate to a 1500L stainless steel intermediate dispersion tank and cool it to below 30°C; add the modified acrylic resin emulsion described in step S3-2 to the intermediate dispersion tank one by one, and then add optional film-forming aids. Stir at 400 rpm to 600 rpm for 1 to 2 hours to obtain water-based acrylic coating.

[0034] In the waterborne acrylic coating preparation method provided by this invention, the water, dispersant, polyether-modified silicone defoamer, stabilizer, thickener, pigment, filler, modified acrylic resin emulsion, and film-forming aid are all the same as described above and will not be repeated. The preparation method of the waterborne acrylic coating provided by this invention has a simple process route, mainly involving mixing and stirring the pre-prepared slurry with the post-adjusted emulsion to obtain the finished product.

[0035] The modified acrylic resin emulsion of the present invention is prepared by the following steps:

[0036] Step S1: Emulsify propylene, methyl methacrylate, styrene, ethyl acrylate, butyl acrylate and hydroxyethyl acrylate to obtain a pre-emulsion;

[0037] Step S2: Under a protective gas atmosphere, the pre-emulsion obtained in step S1 is subjected to polymerization reaction at 70℃~85℃ for 3 h~6 h with the help of buffer and initiator;

[0038] Step S3: Heat the material obtained in step S2 to 80℃~90℃ and keep it at that temperature for 1 h~2 h, then cool it down to 40℃~50℃ and adjust the pH of the system to 6~7 to obtain the modified acrylic resin emulsion.

[0039] This invention first emulsifies propylene, methyl methacrylate, styrene, ethyl acrylate, butyl acrylate, and hydroxyethyl acrylate to obtain a pre-emulsion. Specifically, under a protective gas atmosphere, propylene, methyl methacrylate, styrene, ethyl acrylate, butyl acrylate, hydroxyethyl acrylate, and an emulsifier are stirred in a pure water solvent to emulsify and obtain a pre-emulsion; the emulsification time is 30 min to 50 min. This invention uses pure water as a solvent to avoid the influence of general impurity ions on the system; the amount of pure water solvent added is 20% to 40% of the total weight of the reaction system. The mass ratio of propylene, methyl methacrylate, styrene, ethyl acrylate, butyl acrylate, and hydroxyethyl acrylate added in this invention is 30:(6~7):(4~6):(6~7):(4~6):(1~4). The emulsifier used in this invention is sodium dodecyl sulfate, and its addition amount is 0.5% to 2.5% of the total weight of the polymerization reaction system.

[0040] After obtaining the pre-emulsion, the present invention further describes the polymerization reaction of the pre-emulsion obtained in step S1 at 70°C to 85°C for 3 to 6 hours under a protective gas atmosphere, with the aid of a buffer and an initiator. Specifically, under a protective gas atmosphere, the pre-emulsion obtained in step S1 is first subjected to polymerization at 70°C to 85°C for 20 to 35 minutes under the aid of a first buffer and a first initiator, and then a second buffer and a second initiator are added to continue the reaction for 3 to 5 hours. The mass ratio of the first and second buffers is (7 to 9):(1 to 3); the mass ratio of the first and second initiators is (7 to 9):(1 to 3). The buffer used in this invention is triethanolamine, and its addition amount is 0.1% to 6.0% of the total weight of the polymerization reaction system. The initiator used in this invention is potassium persulfate, and its addition amount is 0.3% to 0.7% of the total weight of the polymerization reaction system. The pH adjuster described in this invention is ammonia water, and its addition amount is 0.05% to 0.6% of the total weight of the polymerization reaction system.

[0041] In this invention, after the polymerization reaction, the obtained material is heated to 80℃~90℃ and held for 1 h~2 h, then cooled to 40℃~50℃, and the pH of the system is adjusted to 6~7 to obtain a modified acrylic resin emulsion. Specifically, the obtained material is heated to 80℃~90℃ and held for 1 h~2 h, then naturally cooled to 40℃~50℃, and a pH adjuster is added to adjust the pH of the system to 6~7 to obtain a modified waterborne acrylic emulsion.

[0042] In some embodiments of the present invention, the modified acrylic resin emulsion of the present invention is prepared by the following steps:

[0043] Step S1: Inert gas is introduced into the reaction vessel, pure water is added as a solvent, and propylene, methyl methacrylate, styrene, ethyl acrylate, butyl acrylate, hydroxyethyl acrylate and emulsifier are added in a certain molar ratio and mixed. The mixture is stirred quickly and evenly, and emulsified for 30 min to 50 min to obtain a suspended, non-stratified pre-emulsion.

[0044] Step S2: Transfer the pre-emulsion obtained in step S1 to a polymerization reactor filled with inert gas, add the appropriate amount of buffer, heat to 70℃~85℃, add initiator to initiate the reaction for 20min~35min, then slowly add about 10% of the remaining emulsifier and initiator to the polymerization emulsion one by one while stirring slowly for about 3h~5h.

[0045] Step S3: After completing step S2, raise the temperature in the polymerization reactor to 80℃~90℃, keep it at that temperature for 1 h~2 h, and then let it cool naturally by 40℃~50℃. Add a pH adjuster to adjust the pH of the system to between 6 and 7, thus obtaining the modified waterborne acrylic emulsion.

[0046] The present invention also provides a coating method comprising the following steps: applying any of the above-described water-based acrylic coatings to the surface of a substrate with a single-coat thickness of 20 μm to 120 μm; preferably, the substrate is selected from metal substrates; more preferably, the substrate is selected from metal substrates treated by sandblasting or shot peening.

[0047] The coating method described in this invention can be achieved using high-pressure airless or air-assisted spraying, with the coating delivered to the spray gun assembly via a pump plunger or Venturi effect and applied to the substrate. The spray gun nozzle can be fan-shaped or circular. The coating method can also be achieved through brushing and / or touch-up brushing, using a fine wool brush or a roller brush. After coating is completed, in low-temperature environments, a thermal drying oven can be used for auxiliary drying; in high-temperature environments, it can be air-dried naturally.

[0048] The water-based acrylic coating of this invention is preferably suitable for sandblasted metal frame surfaces. It can be applied by spraying or brushing, with a single coat thickness of 20 μm to 120 μm. The surface drying time is less than 5 minutes, preferably less than 5 minutes, and the complete drying time is less than 20 minutes, preferably less than 20 minutes. The spraying environment has VOCs < 10 g / L, the released VOCs concentration is low, and the upward escaping dust amount remains at 0 mg / m³. 3 In some embodiments of the present invention, a paint film with a thickness of 80 μm to 160 μm is coated on the surface of the substrate.

[0049] The water-based acrylic coating of this invention can be applied directly to the surface of a sandblasted substrate, reducing the need for primer spraying; the coating dries quickly, with a 40 μm thick coating drying in only 10 to 15 minutes, which helps shorten the drying process; the coating can be applied by high-pressure airless spraying or brushing, which is simple, convenient and easy to operate; the resulting coating has strong adhesion and high hardness to metal surfaces.

[0050] The present invention also provides a coating product comprising: a substrate; and a coating disposed on the surface of the substrate, the coating being obtained from any of the above-described waterborne acrylic coatings. Specifically, the coating is obtained from any of the above-described waterborne acrylic coatings according to any of the above-described coating methods. The substrate of the present invention is the same as described above and will not be repeated here.

[0051] This invention provides a water-based acrylic coating, its preparation method, and its applications. The water-based acrylic coating provided by this invention is primarily used for the final coating of metal frames. This type of coating reduces the number of topcoat coats required. Furthermore, as a water-based system, its biggest difference from oil-based systems lies in its environmental friendliness. During application, it minimizes VOC emissions, reducing the burden on central exhaust gas and dust collection and treatment systems, achieving excellent environmental adaptability without affecting the coating's performance, thus benefiting the environment and the health of construction workers. In addition, the coating formed by the water-based acrylic coating provided by this invention exhibits high hardness, impact resistance, adhesion, and corrosion resistance, making it suitable for various environmental applications, especially for metal frame coating and rapid coating repair.

[0052] Compared with the prior art, the technical improvement of the water-based acrylic coating provided by the present invention is as follows:

[0053] 1. Modified acrylic acid is synthesized by combining soft and hard monomers with special functional monomers in a specific ratio, which improves the adhesion, hardness, scratch resistance, acid and alkali resistance, salt spray resistance and other physicochemical properties of emulsion coatings, and expands the application requirements of waterborne coatings in a variety of environments;

[0054] 2. No special waste gas is generated during the application of water-based coatings; the solvent evaporates into water vapor, which can be directly discharged; excess single-color coating can be recycled and treated; the application method is simple and the operating space is large; the equipment used in the process is simple and conforms to the new direction of energy conservation in the factory.

[0055] 3. This type of coating is a single-component coating with short preparation time; the raw materials are readily available, the process steps are simple, and the manufacturing process is easy; the viscosity can be changed by adding water as needed, making it suitable for subsequent touch-up painting operations; the coating cost is low, which can effectively control application costs. Detailed Implementation

[0056] This invention discloses waterborne acrylic coatings, their preparation methods, and applications. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the desired results. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments, and those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0057] The present invention will be further described below with reference to the embodiments:

[0058] Example 1

[0059] This embodiment provides a single-component modified acrylic waterborne coating suitable for metal frame coating, comprising the following raw materials in parts by weight: water 6%, modified waterborne acrylic emulsion 55.88%, dispersant 0.12%, defoamer 0.1%, stabilizer 1%, thickener 0.5%, pigment 1.4%, and filler 35%. Specifically, the dispersant is Shenzhu Chemical SN-1729, the defoamer is Digo 825, the stabilizer is hydroxypropyl methylcellulose, the thickener is hydrophilic fumed silica, the pigment is hydrophilic, and the filler is 95% pure barium sulfate and talc in a 4:1 ratio.

[0060] The preparation method of modified waterborne acrylic emulsion includes the following steps:

[0061] Step S1: Nitrogen gas is introduced into the reactor, and 30% of the system weight of pure water is added as a solvent. The raw materials propylene, hard monomers methyl methacrylate (MMA), hard monomers styrene (St), soft monomers ethyl acrylate (EA), soft monomers butyl acrylate (BA), and functional monomers hydroxyethyl acrylate (HEV) are added to the reactor in a molar ratio of 30:6.5:5:6.5:5:2. Sodium dodecyl sulfate emulsifier is added to the reactor and mixed. The mixture is stirred rapidly and uniformly. The pre-emulsification time is 45 min to obtain a suspension without stratification.

[0062] Step S2: Transfer the pre-emulsion to a nitrogen-filled polymerization reactor, add 2.5% of the system weight of the buffer triethanolamine, heat to 70°C, add 0.36% of the system weight of the initiator potassium persulfate to initiate the reaction for 30 min, then slowly add about 10% of the remaining emulsifier and initiator to the polymerization emulsion one by one while stirring slowly for 4.5 h;

[0063] Step S3: After completing steps S1 and S2, raise the temperature in the polymerization reactor to 85°C, keep it at that temperature for 1.5 h, and then let it cool naturally to 40°C. Add 0.2% ammonia water (pH adjuster) to adjust the pH value of the system to between 6 and 7, thus obtaining the modified waterborne acrylic emulsion.

[0064] The preparation method of the single-component modified acrylic waterborne coating in this embodiment includes the following steps:

[0065] Step S1: Add water, stabilizer, dispersant, defoamer, thickener and pigment sequentially to a 1000 L stainless steel tank with a cooling water jacket. Stir for 1 hour using a single-axis serrated double turntable (stainless steel material, serrated, diameter 40~50 mm) at a stirring speed of 800 rpm and control the tank temperature at 35℃.

[0066] Step S2: While stirring, add the filler in batches to the tank from Step S1, gradually increasing the stirring speed to 1450 rpm; maintain high-speed stirring to disperse the slurry, control the stirring time to 0.5 h, and keep the tank temperature at 40℃.

[0067] Step S3-1: The uniformly mixed slurry is fed into a 40L horizontal grinder through a pipeline. The grinding media consists of zirconium beads with a purity of 95% or higher, a mass ratio of 6:4, and diameters of 2 mm and 5 mm. The grinding process is started, and the upward slurry is re-entered into the S1 dispersion tank. The slurry is circulated and ground. The stirring speed in the dispersion tank is reduced to 800 rpm, the grinding speed is controlled at 900 rpm, and the temperature of the dispersion tank and the horizontal grinder is controlled at 40℃. The circulation grinding time is 1.5 h.

[0068] Step S3-2: Prepare the modified acrylic resin emulsion and put it into a 1500 stainless steel dispersion tank. Keep the pH at 6.0 and stir at 250 rpm to maintain the emulsion's defoaming and homogenization.

[0069] Step S4: Grind and homogenize the slurry, transfer it to a 1500 L stainless steel intermediate dispersion tank, and cool it to below 30°C; add the emulsion prepared in step S3-2 to the intermediate dispersion tank one by one, and stir at a speed of 400 rpm for 2 hours to obtain the modified acrylic waterborne coating.

[0070] Example 2

[0071] The method for preparing the single-component modified acrylic waterborne coating provided in this embodiment differs from that in Example 1 only in that the modified waterborne acrylic emulsion is prepared by using propylene and hard monomers methyl methacrylate (MMA), styrene (St), ethyl acrylate (EA), butyl acrylate (BA), and hydroxyethyl acrylate (HEV) in a molar ratio of 30:6.5:5:6.5:5:3.5. That is, the amount of hydroxyethyl acrylate (HEV) is increased compared to Example 1.

[0072] Example 3

[0073] The method for preparing the single-component modified acrylic waterborne coating provided in this embodiment differs from that in Example 1 only in that the modified waterborne acrylic emulsion is prepared by using propylene and hard monomers methyl methacrylate (MMA), styrene (St), ethyl acrylate (EA), butyl acrylate (BA), and hydroxyethyl acrylate (HEV) in a molar ratio of 30:6.5:5:7.8:6:2. That is, the molar proportion of soft monomers is increased compared to Example 1.

[0074] Comparative Example 1

[0075] This comparative example provides an existing oil-based asphalt coating of the same color as a comparison of construction results.

[0076] Comparative Example 2

[0077] This comparative example provides a method for preparing a one-component acrylic waterborne coating, which differs from Example 1 only in that an equal amount of unmodified acrylic emulsion is used instead of modified waterborne acrylic emulsion.

[0078] Comparative Example 3

[0079] This comparative example provides a method for preparing another emulsion-type waterborne coating, which differs from Example 1 only in that an equal amount of waterborne alkyd emulsion is used instead of modified waterborne acrylic emulsion.

[0080] Comparative Example 4

[0081] The method for preparing the single-component modified acrylic waterborne coating provided in this embodiment differs from that in Example 1 only in that the modified waterborne acrylic emulsion is prepared using propylene vinylidene and hard monomers methyl methacrylate (MMA), styrene (St), ethyl acrylate (EA), and butyl acrylate (BA) in a molar ratio of 30:6.5:5:6.5:5. The weight proportions of the component raw materials remain constant in the coating system.

[0082] Comparative Example 5

[0083] The method for preparing the single-component modified acrylic waterborne coating provided in this embodiment differs from that in Example 1 only in that the modified waterborne acrylic emulsion is prepared by using propylene and hard monomers methyl methacrylate (MMA), styrene (St), ethyl acrylate (EA), butyl acrylate (BA), and hydroxyethyl acrylate (HEV) in a molar ratio of 30:5.2:4:6.5:5:2. That is, the molar proportion of hard monomers is reduced compared to Example 1.

[0084] Comparative Example 6

[0085] The method for preparing the single-component modified acrylic waterborne coating provided in this embodiment differs from that in Example 1 only in that the modified waterborne acrylic emulsion is prepared by using propylene and hard monomers methyl methacrylate (MMA), styrene (St), ethyl acrylate (EA), butyl acrylate (BA), and hydroxyethyl acrylate (HEV) in a molar ratio of 30:7.8:6:6.5:5:2. That is, the molar proportion of hard monomers is increased compared to Example 1.

[0086] Comparative Example 7

[0087] The method for preparing the single-component modified acrylic waterborne coating provided in this embodiment differs from that in Example 1 only in that the modified waterborne acrylic emulsion is prepared by using propylene and hard monomers methyl methacrylate (MMA), styrene (St), ethyl acrylate (EA), butyl acrylate (BA), and hydroxyethyl acrylate (HEV) in a molar ratio of 30:6.5:5:5.2:4:2. That is, the molar proportion of soft monomers is reduced compared to Example 1.

[0088] Comparative Example 8

[0089] The method for preparing the single-component modified acrylic waterborne coating provided in this embodiment differs from that in Example 1 only in that the thickener in the coating system is replaced with bentonite.

[0090] Comparative Example 9

[0091] The method for preparing the single-component modified acrylic waterborne coating provided in this embodiment differs from that in Example 1 only in that the use of stabilizer is removed from the coating system.

[0092] Comparative Example 10

[0093] The method for preparing the single-component modified acrylic waterborne coating provided in this embodiment differs from that in Example 1 only in that the dispersant is removed from the coating system, while the weight proportions of other components remain unchanged.

[0094] Comparative Example 11

[0095] The method for preparing the single-component modified acrylic waterborne coating provided in this embodiment differs from that in Example 1 only in that the type of dispersant in the coating system is changed to another non-polyelectrolyte dispersant, model Shengshi RD-9615, while the weight percentage of the component raw materials in the coating system remains unchanged.

[0096] Comparative Example 12

[0097] The method for preparing the single-component modified acrylic waterborne coating provided in this embodiment differs from that in Example 1 only in that the use of defoamer is removed from the coating system, while the weight proportions of other components remain unchanged.

[0098] Comparative Example 13

[0099] The method for preparing the single-component modified acrylic waterborne coating provided in this example differs from that in Example 1 only in that the type of defoamer in the coating system is changed to DIG 810 polyether siloxane copolymer, while the weight percentage of the component raw materials in the coating system remains unchanged.

[0100] The sample coatings in the above embodiments and comparative examples were tested for coating and coating performance. The water-based coatings described in the embodiments and comparative examples were sprayed onto tinplate with a specification of 75*150*2mm using an air spraying method. The number of application coats was 3C3B (that is, 3 paint applications followed by 3 drying operations). After each coat was leveled, the coating was placed in a drying oven for curing at 45℃ for 10 minutes. The final film thickness was controlled between 150 μm and 200 μm.

[0101] The test tinplate was pretreated according to the standard GB / T 8923.1-2011 Surface treatment of steel before coating.

[0102] The gas pressure for the spraying process is set to 2 MPa to 5 MPa based on the properties of the coating.

[0103] The testing standards for coatings and paints are as follows:

[0104] Coating stability test: The evaluation is conducted in accordance with the national standard GB / 18581-2009 "Test methods for storage stability of coatings and varnishes".

[0105] Determination of volatile organic compounds in coatings: The test was conducted in accordance with the national standard GB / T 37884-2019 "Determination of the release of volatile organic compounds in coatings".

[0106] Coating hardness test: The test was conducted according to the national standard GB / T 6739-2022 "Determination of hardness of paint film by pencil method for paints and varnishes".

[0107] Impact resistance test of coating: The test was conducted in accordance with the national standard GB / T 1732-2020 "Determination of impact resistance of coating".

[0108] Coating adhesion test: The test was conducted according to the national standard GB / T 5210-2006 "Paints and Varnishes - Pull-off Adhesion Test".

[0109] The corrosion resistance of the coating was tested according to the national standards GB / T 1771-2007 "Determination of resistance to neutral salt spray of paints and varnishes", GB / T 1763-2014 "Acid resistance test of coatings and varnishes" and GB / T 13531-2008 "Alkali resistance test of coatings and varnishes".

[0110] The test performance results of the products obtained in the above embodiments and comparative examples are shown in Table 1:

[0111] Table 1

[0112]

[0113] As can be seen from the performance test results in Table 1, the single-component modified acrylic waterborne coating provided by this invention exhibits excellent long-term storage stability, with a self-volatile VOC concentration value far below the defined environmental protection requirement value. No significant waste gas is emitted during coating application, the spraying is uniform, and the misting is excellent. The modified acrylic coating of Example 1 demonstrates the best performance, exhibiting strong impact resistance and a high surface hardness reaching HB level. The polymerization of functional monomers effectively improves the adhesion requirements of acrylic film formation, allowing the coating to withstand greater tear strength. Simultaneously, a suitable ratio of soft and hard monomers synergistically increases the coating's flexibility. Furthermore, it was found that the modified acrylic film exhibits excellent corrosion resistance, directly affecting the coating's performance on metal surfaces and improving the adaptability and resistance of metal materials in various environments.

[0114] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A water-based acrylic coating, characterized in that, By weight percentage, it includes the following components: Water: 6%~12%; Dispersant: 0.1%~1.0%; the dispersant is one or more of the following: Shengshi RD-9786, BASF4575, BYK-191, Shenzhu Chemical SN-1729, and HY-740W; Polyether-modified silicone defoamer: 0.1%~0.5%; Stabilizer: 0.5%~1.5%; Thickener: 0.1%~1.5%, wherein the thickener is selected from one of hydrophilic fumed silica or polyurethane; Pigment: 0.5%~2.0%, Filler: 30%~45%, Film-forming aids: 0%~3.0%; The modified acrylic resin emulsion comprises 50% to 65%, wherein the modified acrylic resin has monomer units derived from propylene, monomer units derived from methyl methacrylate, monomer units derived from styrene, monomer units derived from ethyl acrylate, monomer units derived from butyl acrylate, and monomer units derived from hydroxyethyl acrylate.

2. The water-based acrylic coating according to claim 1, characterized in that, The modified acrylic resin has monomer units derived from propylene, methyl methacrylate, styrene, ethyl acrylate, butyl acrylate and hydroxyethyl acrylate in a molar ratio of 30:(6~7):(4~6):(6~7):(4~6):(1~4).

3. The water-based acrylic coating according to claim 1, characterized in that, The pH of the modified acrylic resin emulsion is 6-8.

4. The water-based acrylic coating according to claim 1, characterized in that, The film-forming aid is 0.10% to 3.0%.

5. The water-based acrylic coating according to claim 1, characterized in that, The polyether-modified silicone defoamer is selected from one of Hengxin THIX-299, Nanhui CI-3125, Digo 825, Digo 3062, and BYK-019.

6. The waterborne acrylic coating according to claim 1, characterized in that, The stabilizer is selected from one or more of hydroxypropyl methylcellulose, hydroxybenzoic acid, sorbitol polyoxyethylene ether, sodium carboxymethyl cellulose, and propylene glycol block polyether; The pigment is selected from one or more of carbon black, iron oxide red, phthalocyanine blue, titanium dioxide, and chrome green; The filler is selected from one or more of talc, barium sulfate, mica powder, and calcium carbonate; The film-forming aid is selected from one of propylene glycol methyl ether acetate, alcohol ester dodecyl, and propylene glycol methyl ether acetate.

7. The method for preparing waterborne acrylic coatings according to any one of claims 1 to 6, characterized in that, Includes the following steps: A slurry with a particle size of 10 μm to 100 μm is prepared by mixing water, dispersant, polyether-modified silicone defoamer, stabilizer, thickener, pigment and filler. The modified acrylic resin emulsion, optional film-forming aid and the slurry are then mixed to obtain a water-based acrylic coating.

8. The method for preparing waterborne acrylic coating according to claim 7, characterized in that, The modified acrylic resin emulsion is prepared by the following steps: Step S1: Emulsify propylene, methyl methacrylate, styrene, ethyl acrylate, butyl acrylate and hydroxyethyl acrylate to obtain a pre-emulsion; Step S2: Under a protective gas atmosphere, the pre-emulsion obtained in step S1 is subjected to polymerization reaction at 70℃~85℃ for 3 h~6 h with the help of buffer and initiator; Step S3: Heat the material obtained in step S2 to 80℃~90℃ and keep it at that temperature for 1 h~2 h, then cool it down to 40℃~50℃ and adjust the pH of the system to 6~7 to obtain the modified acrylic resin emulsion.

9. A coating method, characterized in that, Includes the following steps: The water-based acrylic coating described in any one of claims 1 to 6 is applied to the substrate surface in a single application with a coating thickness of 20 μm to 120 μm.

10. A coated product, characterized in that, include: Substrate; A coating disposed on the surface of the substrate, the coating being obtained from the water-based acrylic coating as described in any one of claims 1 to 6.

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