Low vocs acrylic resin water-based paint and preparation method thereof

Abstract

The application discloses a low VOCs acrylic resin water-based paint and a preparation method thereof, and belongs to the technical field of high polymer materials and chemical coating, and comprises the following raw materials in parts by weight: 40-80 parts of modified acrylic resin emulsion, 0-30 parts of pigment and filler, 1-5 parts of water-based additive, 10-30 parts of deionized water and 0.5-2 parts of post-added crosslinking agent; the modified acrylic resin emulsion is prepared through core-shell emulsion polymerization process of core layer monomer mixture and shell layer monomer mixture, wherein the shell layer monomer mixture comprises functionalized internal plasticizing monomer and self-crosslinking functional monomer; and the functionalized internal plasticizing monomer is introduced into the shell layer monomer mixture, the monomer is prepared by reacting long-chain fatty alcohol with diisocyanate to obtain an isocyanate-terminated prepolymer, and then the isocyanate-terminated prepolymer is grafted with a hydroxyl-containing acrylic monomer; the long-chain alkyl structure provided by the long-chain fatty alcohol plays a significant internal plasticizing effect on the surface of the latex particle, and effectively reduces the friction between the polymer chain segments.

Description

Technical Field

[0001] This invention relates to the field of polymer materials and chemical coatings, specifically to a low-VOCs acrylic resin waterborne coating and its preparation method. Background Technology

[0002] With increasingly stringent environmental regulations and the development of green coating projects, waterborne acrylic coatings exhibit significant constraints on film-forming properties and physical-mechanical properties in typical scenarios with low volatile organic compound emissions. Traditional formulation design methods, which rely on adding high amounts of film-forming aids or using external physical plasticizers to simply lower the glass transition temperature of the resin, are no longer suitable. This often results in coatings meeting environmental standards with little or no film-forming aids, but with excessively high minimum film-forming temperatures that prevent application, or, after forced film formation, risks such as slow hardening, poor water whitening resistance, and a significant decrease in anti-tack properties. These issues severely impact the practical application of waterborne coatings in high-performance protective and decorative applications.

[0003] The information disclosed in the background section above is only intended to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0004] The purpose of this invention is to provide a low-VOCs acrylic resin waterborne coating and its preparation method, so as to solve the problems mentioned in the background art.

[0005] The technical solution of the present invention comprises the following raw materials in parts by weight: 40-80 parts modified acrylic resin emulsion, 0-30 parts pigments and fillers, 1-5 parts water-based additives, 10-30 parts deionized water, and 0.5-2 parts post-addition crosslinking agent; the modified acrylic resin emulsion is obtained by core-shell emulsion polymerization of a core monomer mixture and a shell monomer mixture, wherein the shell monomer mixture contains functionalized internal plasticizers and self-crosslinking functional monomers; the functionalized internal plasticizer is obtained by reacting long-chain fatty alcohols with diisocyanates to obtain terminal isocyanate prepolymers, and then grafting the terminal isocyanate prepolymers with hydroxyl-containing acrylic monomers.

[0006] Preferably, the preparation process of the functionalized internal plasticizer monomer is as follows: a long-chain fatty alcohol is added to a reaction vessel, nitrogen gas is introduced for protection, the temperature is raised to 50-60°C, dibutyltin dilaurate is added in a catalyst amount of 0.01%-0.05% of the total monomer mass, and diisocyanate is slowly added dropwise. After the addition is completed, the temperature is raised to 75-85°C and the reaction is maintained for 2-3 hours to obtain a terminal isocyanate prepolymer; then the temperature is lowered to 40-50°C, a hydroxyl-containing acrylic monomer and a polymerization inhibitor, such as hydroquinone methyl ether or phenothiazine, are added, the temperature is raised to 65-75°C, and the reaction is maintained for 3-5 hours until the characteristic peak of the -NCO group disappears in the infrared spectrum, thus obtaining the functionalized internal plasticizer monomer.

[0007] Preferably, the long-chain fatty alcohol is selected from at least one of dodecanol, tetradecanol, hexadecyl alcohol, or polyethylene glycol monomethyl ether with a number average molecular weight of 400-1000; the diisocyanate is selected from isophorone diisocyanate or hexamethylene diisocyanate; the hydroxyl-containing acrylic monomer is selected from hydroxyethyl acrylate or hydroxyethyl methacrylate; and the molar ratio of the long-chain fatty alcohol, diisocyanate, and hydroxyl-containing acrylic monomer is 1:(1-1.1):(1-1.1).

[0008] Preferably, the preparation process of the modified acrylic resin emulsion includes a pre-emulsification operation, which is as follows: mixing the core layer monomer mixture with emulsifier and deionized water, and shearing it for 15-20 minutes using a high-speed disperser at 1000-1200 r / min to obtain a core layer pre-emulsion; mixing the shell layer monomer mixture with emulsifier and deionized water, and shearing it for 15-20 minutes at 1000-1200 r / min to obtain a shell layer pre-emulsion; in the shell layer monomer mixture, the mass of functionalized internal plasticizer accounts for 5-15% of the total mass of the shell layer monomers, and the mass of self-crosslinking functional monomer accounts for 2-6% of the total mass of the shell layer monomers.

[0009] Preferably, the core layer monomer mixture is selected from at least one of methyl methacrylate, styrene, and butyl acrylate, and the glass transition temperature (Tg) of the core layer copolymer is designed to be ≥30℃; the self-crosslinking functional monomer is selected from at least one of diacetone acrylamide and ethyl acetoacetate; and the post-added crosslinking agent is selected from adipate dihydrazide.

[0010] Preferably, the pigments and fillers are ground and dispersed before use. The treatment method is as follows: the pigments and fillers, wetting and dispersing agents and a portion of deionized water are mixed and added to a grinding kettle. The filling rate of the grinding media is controlled at 70-80%, the rotation speed is set at 800-1000 r / min, and the mixture is ground until the fineness is ≤20μm to obtain a pigment and filler slurry.

[0011] Preferably, the aqueous additives include defoamers, leveling agents, thickeners, and pH adjusters; the pH adjuster is selected from ammonia or 2-amino-2-methyl-1-propanol, used to adjust the pH value of the system to 8.0-9.0.

[0012] A method for preparing a low-VOCs acrylic resin waterborne coating includes the following steps:

[0013] S1: Preparation of pre-emulsion: The core layer monomer mixture and the shell layer monomer mixture are pre-emulsified to obtain core layer pre-emulsion and shell layer pre-emulsion;

[0014] S2: Preparation of modified acrylic resin emulsion: Add some deionized water and some emulsifier to the reactor, heat to 80-82℃, add initiator solution, and start adding the core layer pre-emulsion dropwise by starvation method, with the dropwise addition time controlled at 1.5-2h; after the core layer is added, keep warm for 15-30min, then heat uniformly to 84-86℃ within 10-20min, start adding the shell layer pre-emulsion and the remaining initiator solution dropwise, with the dropwise addition time controlled at 1.5-2h; after the shell layer is added, heat to 90-92℃, keep the reaction at this temperature for 1h, then cool to 50-60℃, add redox initiator system for post-elimination treatment, stir for 30-45min, cool to below 40℃, adjust the pH value to 7.5-8.5 with ammonia water, and filter out the material;

[0015] S3: Coating preparation: Add the modified acrylic resin emulsion obtained in S2 to the paint mixing tank, set the stirring speed to 300-400 r / min, slowly add the prepared pigment and filler slurry, water-based additives and post-added crosslinking agent, mix evenly, adjust the speed to 800-1000 r / min and disperse for 15-20 min.

[0016] S4: Finished product packaging: Let the mixture obtained in S3 stand for 30-60 minutes to degas, then filter it through a 200-mesh filter to obtain a low-VOCs acrylic resin water-based coating.

[0017] This invention provides a low-VOCs acrylic resin waterborne coating, which has the following improvements and advantages compared with the prior art:

[0018] 1. This method introduces a functionalized internal plasticizer into the shell monomer mixture. This monomer is prepared by reacting a long-chain fatty alcohol with a diisocyanate to obtain a terminal isocyanate prepolymer, which is then grafted onto a hydroxyl-containing acrylic monomer. The long-chain alkyl structure provided by the long-chain fatty alcohol plays a significant internal plasticizing role on the surface of the latex particles, effectively reducing the frictional force between polymer chain segments. Specifically, based on the free volume theory, the long-chain alkyl introduced from the side chain acts as a molecular wedge, effectively increasing the free volume between polymer chain segments and significantly weakening the van der Waals forces between molecules, thereby reducing the shell polymer's... Glass transition temperature; During the film-forming process of coatings, as water evaporates, latex particles are subjected to capillary pressure. The modified shell layer with high chain segment mobility makes the particles easily undergo viscous deformation and fill the gaps between each other, promoting the diffusion and entanglement of polymer chain segments across particle boundaries. Thus, without the aid of highly volatile solvents to swell and soften the resin, continuous and dense film-forming at low temperatures is achieved by relying on the structural flexibility of the resin itself. This chemical modification method allows coatings to achieve extremely low minimum film-forming temperatures with little or no addition of highly volatile film-forming aids. Experimental data shows that when the VOC content is below 15 g / L or even reaches 6 g / L, the minimum film-forming temperature of the coating can be controlled below 4 degrees Celsius, or even reaches 0 degrees Celsius. Compared with existing technologies using alcohol ester film-forming aids, this significantly reduces environmental pollution and avoids the problem of coating cracking at low temperatures.

[0019] 2. This method introduces a self-crosslinking functional monomer into the shell layer of the modified acrylic resin emulsion, and adds a crosslinking agent. During the coating drying process, the ketone carbonyl group and the acyl hydrazine group undergo a crosslinking reaction to form a dense network chemical structure. This crosslinking network effectively locks in the flexibility defects that may be caused by the introduction of internal plasticizing groups, and compensates for the problem of decreased film hardness caused by internal plasticizing. Experimental results show that the pencil hardness of the coating prepared by this method can reach H to 2H, the water whitening resistance is no whitening or slight whitening, and the anti-tackness reaches the mark-free level. Compared with the control group without the addition of self-crosslinking monomers, this method solves the technical problems of softness, poor water resistance and easy adhesion of traditional low VOC coatings after film formation, and achieves the organic unity of soft monomer-assisted film formation and crosslinking network-assisted reinforcement.

[0020] 3. This solution grafts long-chain segments with internal plasticizing properties onto the acrylic resin backbone via chemical bonding. This structural design ensures that the plasticizing groups will not migrate or precipitate during long-term use of the coating, thus guaranteeing the long-term stability of the coating performance. Comparative experiments show that coatings with physically added plasticizers have extremely low hardness and poor anti-tack properties, while this solution avoids this defect through chemical grafting, ensuring that the coating maintains excellent surface hardness and anti-blocking properties while exhibiting flexibility. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0022] Example 1

[0023] This invention provides a low-VOCs acrylic resin waterborne coating, comprising the following raw materials in parts by weight: 40-80 parts modified acrylic resin emulsion, 0-30 parts pigments and fillers, 1-5 parts waterborne additives, 10-30 parts deionized water, and 0.5-2 parts post-addition crosslinking agent; the modified acrylic resin emulsion is obtained by core-shell emulsion polymerization of a core-layer monomer mixture and a shell-layer monomer mixture, wherein the shell-layer monomer mixture contains functionalized internal plasticizers and self-crosslinking functional monomers; the functionalized internal plasticizer is obtained by reacting long-chain fatty alcohols with diisocyanates to obtain terminal isocyanate-based prepolymers, and then grafting the terminal isocyanate-based prepolymers with hydroxyl-containing acrylic monomers.

[0024] In this embodiment, the preparation process of the functionalized internal plasticizer is as follows: diisocyanate is added to a reaction vessel, nitrogen gas is introduced for protection, the temperature is raised to 50-60°C, long-chain fatty alcohol is slowly added dropwise, and after the addition is completed, the temperature is raised to 75-85°C and the reaction is maintained for 2-3 hours to obtain a terminal isocyanate prepolymer; then the temperature is lowered to 40-50°C, hydroxyl-containing acrylic monomer and polymerization inhibitor, such as hydroquinone methyl ether or phenothiazine, are added, the temperature is raised to 65-75°C, and the reaction is maintained for 3-5 hours until the characteristic peak of the -NCO group disappears in the infrared spectrum, thus obtaining the functionalized internal plasticizer.

[0025] In this embodiment, the long-chain fatty alcohol is selected from at least one of dodecanol, tetradecyl alcohol, hexadecyl alcohol, or polyethylene glycol monomethyl ether with a number average molecular weight of 400-1000; the diisocyanate is selected from isophorone diisocyanate or hexamethylene diisocyanate; the hydroxyl-containing acrylic monomer is selected from hydroxyethyl acrylate or hydroxyethyl methacrylate; the molar ratio of the long-chain fatty alcohol, diisocyanate and hydroxyl-containing acrylic monomer is 1:(1-1.1):(1-1.1).

[0026] In this embodiment, the preparation process of the modified acrylic resin emulsion includes a pre-emulsification operation, which is as follows: the core layer monomer mixture is mixed with emulsifier and deionized water, and sheared at 1000-1200 r / min for 15-20 min using a high-speed disperser to obtain a core layer pre-emulsion; the shell layer monomer mixture is mixed with emulsifier and deionized water, and sheared at 1000-1200 r / min for 15-20 min to obtain a shell layer pre-emulsion; in the shell layer monomer mixture, the mass of functionalized internal plasticizer accounts for 5-15% of the total mass of the shell layer monomers, and the mass of self-crosslinking functional monomer accounts for 2-6% of the total mass of the shell layer monomers.

[0027] In this invention, the emulsifier is a mixed emulsifier composed of anionic emulsifier sodium dodecyl sulfate and nonionic emulsifier alkylphenol polyoxyethylene ether in a mass ratio of 2:1, or sodium dodecylbenzene sulfonate.

[0028] In this embodiment, the core layer monomer mixture is selected from at least one of methyl methacrylate, styrene, and butyl acrylate, and the glass transition temperature design value Tg of the core layer copolymer is ≥30℃; the self-crosslinking functional monomer is selected from at least one of diacetone acrylamide and ethyl acetoacetate; and the added crosslinking agent is adipic acid dihydrazide.

[0029] In this embodiment, the pigments and fillers are ground and dispersed before use. The treatment method is as follows: the pigments and fillers, wetting and dispersing agents and some deionized water are mixed and added to the grinding kettle. The filling rate of the grinding media is controlled at 70-80%, the rotation speed is set at 800-1000 r / min, and the grinding is carried out until the fineness is ≤20μm to obtain the pigment and filler slurry.

[0030] In this embodiment, the aqueous additives include defoamers, leveling agents, thickeners, and pH adjusters; the pH adjuster is selected from ammonia or 2-amino-2-methyl-1-propanol, used to adjust the pH value of the system to 8.0-9.0.

[0031] This embodiment also provides a method for preparing a low-VOCs acrylic resin waterborne coating, including the following steps: S1: Pre-emulsion preparation: The core layer monomer mixture and the shell layer monomer mixture are pre-emulsified according to the above pre-emulsification operation to obtain a core layer pre-emulsion and a shell layer pre-emulsion; S2: Modified acrylic resin emulsion preparation: Part of deionized water and part of emulsifier are added to a reaction vessel, the temperature is raised to 80-82°C, an initiator solution is added, and the core layer pre-emulsion is added dropwise in a starved state, with the dropwise addition time controlled at 1.5-2 hours; After the core layer is added, the temperature is maintained for 15-30 minutes, and then the temperature is raised uniformly to 84-86°C within 10-20 minutes, and the shell layer pre-emulsion and the remaining initiator solution are added dropwise, with the dropwise addition time controlled at 1.5-2 hours; After the shell layer is added... Afterwards, the temperature is raised to 90-92℃ and kept at that temperature for 1 hour. Then, the temperature is lowered to 50-60℃, and a redox initiator system is added for post-elimination treatment. The mixture is stirred for 30-45 minutes, then cooled to below 40℃. The pH value is adjusted to 7.5-8.5 with ammonia water, and the mixture is filtered out. S3: Coating preparation: The modified acrylic resin emulsion obtained in S2 is added to the paint mixing tank. The stirring speed is set to 300-400 r / min. The pigment and filler slurry, water-based additives, and post-addition crosslinking agent prepared according to the above method are slowly added. After mixing evenly, the stirring speed is adjusted to 800-1000 r / min and dispersed for 15-20 minutes. S4: Finished product packaging: The mixture obtained in S3 is allowed to stand for degassing for 30-60 minutes and then filtered through a 200-mesh filter to obtain a low-VOCs acrylic resin water-based coating.

[0032] This embodiment provides a low-VOCs acrylic resin waterborne coating, comprising the following raw materials in parts by weight: 60 parts modified acrylic resin emulsion, 15 parts pigments and fillers, 3 parts waterborne additives, 21 parts deionized water, and 1 part post-addition crosslinking agent. The modified acrylic resin emulsion is obtained by core-shell emulsion polymerization of a core-layer monomer mixture and a shell-layer monomer mixture. The shell-layer monomer mixture contains functionalized internal plasticizers and self-crosslinking functional monomers. The functionalized internal plasticizer is obtained by reacting long-chain fatty alcohols with diisocyanates to obtain isocyanate-terminated prepolymers, which are then grafted with hydroxyl-containing acrylic monomers. The preparation process of the functionalized internal plasticizer monomer is as follows: Diisocyanate is added to a reaction vessel, nitrogen gas is introduced for protection, the temperature is raised to 55°C, and long-chain fatty alcohol is slowly added dropwise. After the addition is complete, the temperature is raised to 80°C and the reaction is maintained for 2.5 hours to obtain a terminal isocyanate prepolymer. Subsequently, the temperature is lowered to 45°C, and a hydroxyl-containing acrylic monomer and a polymerization inhibitor, such as hydroquinone methyl ether or phenothiazine, are added. The temperature is raised to 70°C and the reaction is maintained for another 4 hours until the characteristic peak of the -NCO group disappears in the infrared spectrum, thus obtaining the functionalized internal plasticizer monomer. The long-chain fatty alcohol is dodecyl alcohol; the diisocyanate is isophorone diisocyanate; the hydroxyl-containing acrylic monomer is hydroxyethyl acrylate; the molar ratio of long-chain fatty alcohol, diisocyanate and hydroxyl-containing acrylic monomer is 1:1.05:1.05. The preparation of modified acrylic resin emulsion includes a pre-emulsification process, which involves: mixing the core layer monomer mixture with emulsifier and deionized water, and shearing at 1100 r / min for 18 min using a high-speed disperser to obtain a core layer pre-emulsion; mixing the shell layer monomer mixture with emulsifier and deionized water, and shearing at 1100 r / min for 18 min to obtain a shell layer pre-emulsion; in the shell layer monomer mixture, the mass of functionalized internal plasticizer accounts for 10% of the total mass of the shell layer monomers, and the mass of self-crosslinking functional monomer accounts for 4% of the total mass of the shell layer monomers. The core layer monomer mixture is a mixture of methyl methacrylate, styrene, and butyl acrylate, with a designed glass transition temperature (Tg) of 45℃; the self-crosslinking functional monomer is diacetone acrylamide; and the crosslinking agent added later is adipic acid dihydrazide. Before use, the pigments and fillers are ground and dispersed. The treatment method is as follows: mix the pigments and fillers, titanium dioxide, wetting and dispersing agent, and part of deionized water, add them to a grinding kettle, control the filling rate of the grinding media to 75%, set the rotation speed to 900 r / min, and grind to a fineness of 15 μm to obtain the pigment and filler slurry. Water-based additives include defoamers, leveling agents, thickeners, and pH adjusters; the pH adjuster selected is 2-amino-2-methyl-1-propanol, used to adjust the pH value of the system to 8.5.A method for preparing a low-VOCs acrylic resin waterborne coating includes the following steps: S1: Pre-emulsion preparation: The core layer monomer mixture and the shell layer monomer mixture are pre-emulsified according to the above parameters to obtain a core layer pre-emulsion and a shell layer pre-emulsion; S2: Modified acrylic resin emulsion preparation: Part of deionized water and part of emulsifier are added to a reaction vessel, the temperature is raised to 81°C, an initiator solution is added, and the core layer pre-emulsion is added dropwise using a starved state method, with the dropwise addition time controlled at 1.8 h; after the core layer is added, the temperature is maintained for 20 min, and then the temperature is gradually increased to 85°C, and the shell layer pre-emulsion and the remaining initiator solution are added dropwise, with the dropwise addition time controlled at 1.8 h; after the shell layer is added, the temperature is raised to... The reaction was carried out at 91℃ for 1 hour, then cooled to 55℃. A redox initiator system was added for post-elimination treatment, and the mixture was stirred for 40 minutes. The temperature was then lowered to below 40℃, and the pH was adjusted to 8.5 with 2-amino-2-methyl-1-propanol. The mixture was then filtered out. S3: Coating preparation: The modified acrylic resin emulsion obtained in S2 was added to the paint mixing tank. The stirring speed was set to 350 r / min. The pigment and filler slurry, water-based additives, and post-addition crosslinking agent prepared as described above were slowly added. After mixing evenly, the stirring speed was adjusted to 900 r / min and dispersed for 18 minutes. S4: Finished product packaging: The mixture obtained in S3 was allowed to stand for 45 minutes to degas. It was then filtered through a 200-mesh filter to obtain a low-VOCs acrylic resin water-based coating.

[0033] In this invention, the initiator solution in step S2 is an aqueous solution of ammonium persulfate, potassium persulfate, or sodium persulfate, with a concentration of 2-5 wt%; the oxidant in the redox initiator system is selected from tert-butyl hydroperoxide, and the reducing agent is selected from sodium formaldehyde sulfoxylate or ascorbic acid.

[0034] In this embodiment, the functionalized internal plasticizer monomer, by introducing the long-chain alkyl structure of dodecyl alcohol, plays a significant internal plasticizing role in the film-forming process of the modified acrylic resin emulsion. This effectively reduces the friction between polymer chain segments, enabling the low-VOCs acrylic resin waterborne coating to achieve a lower minimum film-forming temperature without the addition of film-forming aids. Simultaneously, the self-crosslinking functional monomer introduced into the shell monomer mixture of the modified acrylic resin emulsion undergoes a ketone-hydrazine crosslinking reaction with the subsequently added crosslinking agent during the coating drying process. This chemical crosslinking network not only compensates for the potential decrease in film hardness caused by the introduction of internal plasticizer groups but also significantly improves the coating's water resistance and scrub resistance, thus solving the technical challenge of balancing film-forming properties and physical and mechanical properties in traditional low-VOC coatings.

[0035] Example 2

[0036] This embodiment provides a low-VOCs acrylic resin waterborne coating, comprising the following raw materials in parts by weight: 80 parts modified acrylic resin emulsion, 0 parts pigments and fillers as a clear varnish system, 5 parts waterborne additives, 13 parts deionized water, and 2 parts post-addition crosslinking agent. The modified acrylic resin emulsion is obtained by core-shell emulsion polymerization of a core monomer mixture and a shell monomer mixture. The shell monomer mixture contains functionalized internal plasticizers and self-crosslinking functional monomers. The functionalized internal plasticizer is obtained by reacting long-chain fatty alcohols with diisocyanates to obtain isocyanate-terminated prepolymers, and then grafting the isocyanate-terminated prepolymers with hydroxyl-containing acrylic monomers. The preparation process of the functionalized internal plasticizer monomer is as follows: Diisocyanate is added to a reaction vessel, nitrogen gas is introduced for protection, the temperature is raised to 60°C, and long-chain fatty alcohol is slowly added dropwise. After the addition is complete, the temperature is raised to 85°C and the reaction is maintained for 3 hours to obtain a terminal isocyanate prepolymer. Subsequently, the temperature is lowered to 50°C, and a hydroxyl-containing acrylic monomer and a polymerization inhibitor, such as hydroquinone methyl ether or phenothiazine, are added. The temperature is raised to 75°C and the reaction is maintained for another 5 hours until the characteristic peak of the -NCO group disappears in the infrared spectrum, thus obtaining the functionalized internal plasticizer monomer. The long-chain fatty alcohol is hexadecyl alcohol; the diisocyanate is hexamethylene diisocyanate; the hydroxyl-containing acrylic monomer is hydroxyethyl methacrylate; the molar ratio of long-chain fatty alcohol, diisocyanate and hydroxyl-containing acrylic monomer is 1:1.1:1.1. The preparation of modified acrylic resin emulsion includes a pre-emulsification process, which involves: mixing the core layer monomer mixture with emulsifier and deionized water, and shearing at 1200 rpm for 20 min using a high-speed disperser to obtain a core layer pre-emulsion; mixing the shell layer monomer mixture with emulsifier and deionized water, and shearing at 1200 rpm for 20 min to obtain a shell layer pre-emulsion; in the shell layer monomer mixture, the mass of the functionalized internal plasticizer accounts for 15% of the total mass of the shell layer monomers, and the mass of the self-crosslinking functional monomer accounts for 6% of the total mass of the shell layer monomers. The core layer monomer mixture is a mixture of methyl methacrylate and butyl acrylate, with a designed glass transition temperature (Tg) of 55℃; the self-crosslinking functional monomer is ethyl acetoacetate; and the added crosslinking agent is adipic acid dihydrazide. Aqueous additives include defoamers, leveling agents, thickeners, and pH adjusters; the pH adjuster is ammonia water, used to adjust the system pH to 9.0.A method for preparing a low-VOCs acrylic resin waterborne coating includes the following steps: S1: Pre-emulsion preparation: The core layer monomer mixture and the shell layer monomer mixture are pre-emulsified according to the above parameters to obtain a core layer pre-emulsion and a shell layer pre-emulsion; S2: Modified acrylic resin emulsion preparation: Part of deionized water and part of emulsifier are added to a reaction vessel, the temperature is raised to 82°C, an initiator solution is added, and the core layer pre-emulsion is added dropwise using a starved state method, with the dropwise addition time controlled at 2 hours; After the core layer is added, the temperature is maintained for 30 minutes, and then the temperature is gradually increased to 86°C, and the shell layer pre-emulsion and the remaining initiator solution are added dropwise, with the dropwise addition time controlled at 2 hours; After the addition is complete, the temperature is raised to 92℃ and kept at that temperature for 1 hour. Then the temperature is lowered to 60℃, and the redox initiator system is added for post-elimination treatment. The mixture is stirred for 45 minutes, then cooled to below 40℃. The pH value is adjusted to 9.0 with ammonia water, and the mixture is filtered out. S3: Coating preparation: The modified acrylic resin emulsion obtained in S2 is added to the paint mixing tank. The stirring speed is set to 400 r / min. The water-based additives and post-addition crosslinking agents are slowly added. After mixing evenly, the stirring speed is adjusted to 1000 r / min and dispersed for 20 minutes. S4: Finished product packaging: The mixture obtained in S3 is allowed to stand for 60 minutes to degas. It is then filtered through a 200-mesh filter to obtain a low-VOCs acrylic resin water-based coating.

[0037] In this embodiment, the functionalized internal plasticizers selected are hexadecyl alcohol with a longer carbon chain and HDI with better flexibility as raw materials. This long-chain structure endows the modified acrylic resin emulsion with superior flexibility and low-temperature film-forming ability. Since the amount of functionalized internal plasticizers in the shell monomer mixture reaches 15%, the film-forming resistance caused by the high Tg core layer is significantly reduced. Combined with a high content of self-crosslinking functional monomer, AAEM, 6%, the low-VOCs acrylic resin waterborne coating can form a dense crosslinked structure after film formation. Even in the clear varnish system, it can exhibit excellent anti-tack and high gloss, making it suitable for coating scenarios of wood or metal surfaces with high requirements for appearance and hardness.

[0038] Example 3

[0039] This embodiment provides a low-VOCs acrylic resin waterborne coating, comprising the following raw materials in parts by weight: 40 parts modified acrylic resin emulsion, 30 parts pigments and fillers, 1 part waterborne additives, 28.5 parts deionized water, and 0.5 parts post-addition crosslinking agent. The modified acrylic resin emulsion is obtained by core-shell emulsion polymerization of a core-layer monomer mixture and a shell-layer monomer mixture. The shell-layer monomer mixture contains functionalized internal plasticizers and self-crosslinking functional monomers. The functionalized internal plasticizer is obtained by reacting long-chain fatty alcohols with diisocyanates to obtain isocyanate-terminated prepolymers, which are then grafted with hydroxyl-containing acrylic monomers. The preparation process of the functionalized internal plasticizer monomer is as follows: Diisocyanate is added to a reaction vessel, nitrogen gas is introduced for protection, the temperature is raised to 50°C, and long-chain fatty alcohol is slowly added dropwise. After the addition is complete, the temperature is raised to 75°C and the reaction is maintained for 2 hours to obtain a terminal isocyanate prepolymer. Subsequently, the temperature is lowered to 40°C, and a hydroxyl-containing acrylic monomer and a polymerization inhibitor, such as hydroquinone methyl ether or phenothiazine, are added. The temperature is raised to 65°C and the reaction is maintained for another 3 hours until the characteristic peak of the -NCO group disappears in the infrared spectrum, thus obtaining the functionalized internal plasticizer monomer. The long-chain fatty alcohol is tetradecyl alcohol; the diisocyanate is isophorone diisocyanate; the hydroxyl-containing acrylic monomer is hydroxyethyl acrylate; the molar ratio of long-chain fatty alcohol, diisocyanate and hydroxyl-containing acrylic monomer is 1:1:1. The preparation process of the modified acrylic resin emulsion includes a pre-emulsification operation, which is as follows: the core layer monomer mixture is mixed with emulsifier and deionized water, and sheared at 1000 r / min for 15 min using a high-speed disperser to obtain a core layer pre-emulsion; the shell layer monomer mixture is mixed with emulsifier and deionized water, and sheared at 1000 r / min for 15 min to obtain a shell layer pre-emulsion; in the shell layer monomer mixture, the mass of functionalized internal plasticizer accounts for 5% of the total mass of the shell layer monomers, and the mass of self-crosslinking functional monomer accounts for 2% of the total mass of the shell layer monomers. The core layer monomer mixture is a mixture of methyl methacrylate and styrene, with a designed glass transition temperature (Tg) of 35℃. The self-crosslinking functional monomer is diacetone acrylamide. The added crosslinking agent is adipic acid dihydrazide. Before use, the pigments and fillers are ground and dispersed. The method is as follows: pigments and fillers, calcium carbonate and titanium dioxide compound, wetting and dispersing agent, and a portion of deionized water are mixed and added to a grinding tank. The grinding media filling rate is controlled at 70%, the rotation speed is set at 800 r / min, and grinding is carried out to a fineness of 20 μm to obtain the pigment and filler slurry. Water-based additives include defoamers, leveling agents, thickeners, and pH adjusters. The pH adjuster is 2-amino-2-methyl-1-propanol, used to adjust the system pH to 8.0.A method for preparing a low-VOCs acrylic resin waterborne coating includes the following steps: S1: Pre-emulsion preparation: The core layer monomer mixture and the shell layer monomer mixture are pre-emulsified according to the above parameters to obtain a core layer pre-emulsion and a shell layer pre-emulsion; S2: Modified acrylic resin emulsion preparation: Part of deionized water and part of emulsifier are added to a reaction vessel, the temperature is raised to 80°C, an initiator solution is added, and the core layer pre-emulsion is added dropwise using a starved state method, with the dropwise addition time controlled at 1.5 h; After the core layer is added, the temperature is maintained for 15 min, and then the temperature is gradually increased to 84°C, and the shell layer pre-emulsion and the remaining initiator solution are added dropwise, with the dropwise addition time controlled at 1.5 h; After the shell layer is added, the temperature is raised to... The reaction was carried out at 90℃ for 1 hour, then cooled to 50℃. A redox initiator system was added for post-elimination treatment, and the mixture was stirred for 30 minutes. The temperature was then lowered to below 40℃, and the pH was adjusted to 8.0 with 2-amino-2-methyl-1-propanol. The mixture was then filtered out. S3: Coating preparation: The modified acrylic resin emulsion obtained in S2 was added to the paint mixing tank. The stirring speed was set to 300 r / min. The pigment and filler slurry, water-based additives, and post-addition crosslinking agent prepared as described above were slowly added. After mixing evenly, the stirring speed was adjusted to 800 r / min and dispersed for 15 minutes. S4: Finished product packaging: The mixture obtained in S3 was allowed to stand for 30 minutes to degas. It was then filtered through a 200-mesh filter to obtain a low-VOCs acrylic resin water-based coating.

[0040] In this embodiment, the low-VOC acrylic waterborne coating uses a relatively high pigment and filler content of 30 parts, which typically increases the difficulty of film formation. However, by introducing 5% functionalized internal plasticizer into the shell monomer mixture, based on tetradecyl alcohol, the surface properties of the latex particles are effectively improved, promoting wetting and fusion between the particles and pigments and fillers. Although the amount of self-crosslinking functional monomer is low (2%), combined with a suitable Tg design in the core monomer mixture at 35°C, the coating achieves excellent cost-effectiveness while ensuring basic mechanical strength, making it particularly suitable for interior wall coating applications where cost is sensitive but environmental low-VOC requirements still need to be met.

[0041] Example 4

[0042] This embodiment provides a low-VOCs acrylic resin waterborne coating, comprising the following raw materials in parts by weight: 50 parts modified acrylic resin emulsion, 20 parts pigments and fillers, 2 parts waterborne additives, 26.5 parts deionized water, and 1.5 parts post-addition crosslinking agent. The modified acrylic resin emulsion is obtained by core-shell emulsion polymerization of a core-layer monomer mixture and a shell-layer monomer mixture. The shell-layer monomer mixture contains functionalized internal plasticizers and self-crosslinking functional monomers. The functionalized internal plasticizer is obtained by reacting long-chain fatty alcohols with diisocyanates to obtain isocyanate-terminated prepolymers, which are then grafted with hydroxyl-containing acrylic monomers. The preparation process of the functionalized internal plasticizer monomer is as follows: Diisocyanate is added to a reaction vessel, nitrogen gas is introduced for protection, the temperature is raised to 52°C, and long-chain fatty alcohol is slowly added dropwise. After the addition is complete, the temperature is raised to 78°C and the reaction is maintained for 2.5 hours to obtain a terminal isocyanate prepolymer. Subsequently, the temperature is lowered to 42°C, and a hydroxyl-containing acrylic monomer and a polymerization inhibitor, such as hydroquinone methyl ether or phenothiazine, are added. The temperature is raised to 68°C and the reaction is maintained for another 3.5 hours until the characteristic peak of the -NCO group disappears in the infrared spectrum, thus obtaining the functionalized internal plasticizer monomer. The long-chain fatty alcohol is polyethylene glycol monomethyl ether with a molecular weight of 400; the diisocyanate is isophorone diisocyanate; and the hydroxyl-containing acrylic monomer is hydroxyethyl methacrylate. The molar ratio of the long-chain fatty alcohol, diisocyanate, and hydroxyl-containing acrylic monomer is 1:1.02:1.02. The preparation process of the modified acrylic resin emulsion includes a pre-emulsification operation, which is as follows: the core layer monomer mixture is mixed with emulsifier and deionized water, and sheared at 1050 r / min for 16 min using a high-speed disperser to obtain a core layer pre-emulsion; the shell layer monomer mixture is mixed with emulsifier and deionized water, and sheared at 1050 r / min for 16 min to obtain a shell layer pre-emulsion; in the shell layer monomer mixture, the mass of functionalized internal plasticizer accounts for 8% of the total mass of the shell layer monomers, and the mass of self-crosslinking functional monomer accounts for 5% of the total mass of the shell layer monomers. The core layer monomer mixture is a mixture of methyl methacrylate and butyl acrylate, with a designed glass transition temperature (Tg) of 40℃. The self-crosslinking functional monomer is diacetone acrylamide. The added crosslinking agent is adipic acid dihydrazide. Before use, the pigments and fillers are ground and dispersed. The method is as follows: the pigments and fillers, wetting and dispersing agents, and a portion of deionized water are mixed and added to a grinding tank. The filling rate of the grinding media is controlled at 72%, the rotation speed is set at 850 r / min, and grinding is carried out to a fineness of 18 μm to obtain the pigment and filler slurry. Water-based additives include defoamers, leveling agents, thickeners, and pH adjusters. The pH adjuster is 2-amino-2-methyl-1-propanol, used to adjust the system pH to 8.8.A method for preparing a low-VOCs acrylic resin waterborne coating includes the following steps: S1: Pre-emulsion preparation: The core layer monomer mixture and the shell layer monomer mixture are pre-emulsified according to the above parameters to obtain a core layer pre-emulsion and a shell layer pre-emulsion; S2: Modified acrylic resin emulsion preparation: Part of deionized water and part of emulsifier are added to a reaction vessel, the temperature is raised to 81°C, an initiator solution is added, and the core layer pre-emulsion is added dropwise using a starved state method, with the dropwise addition time controlled at 1.6 h; after the core layer is added, the temperature is maintained for 25 min, and then the temperature is gradually increased to 85°C, and the shell layer pre-emulsion and the remaining initiator solution are added dropwise, with the dropwise addition time controlled at 1.6 h; after the shell layer is added, the temperature is raised to... The reaction was carried out at 91℃ for 1 hour, then cooled to 55℃. A redox initiator system was added for post-elimination treatment, and the mixture was stirred for 35 minutes. The temperature was then lowered to below 40℃, and the pH was adjusted to 8.8 with 2-amino-2-methyl-1-propanol. The mixture was then filtered out. S3: Coating preparation: The modified acrylic resin emulsion obtained in S2 was added to the paint mixing tank. The stirring speed was set to 320 r / min. The pigment and filler slurry, water-based additives, and post-addition crosslinking agent prepared as described above were slowly added. After mixing evenly, the stirring speed was adjusted to 850 r / min and dispersed for 16 minutes. S4: Finished product packaging: The mixture obtained in S3 was allowed to stand for 40 minutes to degas. It was then filtered through a 200-mesh filter to obtain a low-VOCs acrylic resin water-based coating.

[0043] In this embodiment, polyethylene glycol monomethyl ether was selected as the long-chain alcohol raw material for the functionalized internal plasticizer. This polyether segment not only provides flexibility but also introduces hydrophilic segments, which helps improve the freeze-thaw stability of the modified acrylic resin emulsion. Although the introduction of hydrophilic segments usually reduces water resistance, in this embodiment, by setting the amount of the self-crosslinking functional monomer to 5% and adding a post-crosslinking agent, a network structure is formed after film formation using a ketone-hydrazine crosslinking reaction, effectively locking in the hydrophilic groups. This ensures low VOCs and good film-forming properties while maintaining a balance of various properties of the low-VOC acrylic resin waterborne coating, making it particularly suitable for applications with high requirements for storage stability.

[0044] Example 5

[0045] This embodiment provides a low-VOCs acrylic resin waterborne coating, comprising the following raw materials in parts by weight: 70 parts modified acrylic resin emulsion, 10 parts pigments and fillers, 4 parts waterborne additives, 14.8 parts deionized water, and 1.2 parts post-addition crosslinking agent. The modified acrylic resin emulsion is obtained by core-shell emulsion polymerization of a core-layer monomer mixture and a shell-layer monomer mixture. The shell-layer monomer mixture contains functionalized internal plasticizers and self-crosslinking functional monomers. The functionalized internal plasticizer is obtained by reacting long-chain fatty alcohols with diisocyanates to obtain isocyanate-terminated prepolymers, which are then grafted with hydroxyl-containing acrylic monomers. The preparation process of the functionalized internal plasticizer monomer is as follows: Diisocyanate is added to a reaction vessel, nitrogen gas is introduced for protection, the temperature is raised to 58°C, and long-chain fatty alcohol is slowly added dropwise. After the addition is complete, the temperature is raised to 82°C and the reaction is maintained for 2.8 hours to obtain a terminal isocyanate prepolymer. Subsequently, the temperature is lowered to 48°C, and a hydroxyl-containing acrylic monomer and a polymerization inhibitor, such as hydroquinone methyl ether or phenothiazine, are added. The temperature is raised to 72°C and the reaction is maintained for another 4.5 hours until the characteristic peak of the -NCO group disappears in the infrared spectrum, thus obtaining the functionalized internal plasticizer monomer. The long-chain fatty alcohol is selected as dodecanol; the diisocyanate is selected as hexamethylene diisocyanate; the hydroxyl-containing acrylic monomer is selected as hydroxyethyl acrylate; the molar ratio of long-chain fatty alcohol, diisocyanate and hydroxyl-containing acrylic monomer is 1:1.08:1.08. The preparation of the modified acrylic resin emulsion includes a pre-emulsification process, which involves: mixing the core monomer mixture with emulsifier and deionized water, and shearing it for 19 minutes using a high-speed disperser at 1150 r / min to obtain a core pre-emulsion; mixing the shell monomer mixture with emulsifier and deionized water, and shearing it for 19 minutes at 1150 r / min to obtain a shell pre-emulsion; in the shell monomer mixture, the mass of the functionalized internal plasticizer accounts for 12% of the total mass of the shell monomers, and the mass of the self-crosslinking functional monomer accounts for 3% of the total mass of the shell monomers. The core monomer mixture is a mixture of methyl methacrylate, styrene, and butyl acrylate, with a designed glass transition temperature (Tg) of 50℃; the self-crosslinking functional monomer is diacetone acrylamide; and the crosslinking agent added later is adipic acid dihydrazide. Before use, the pigments and fillers undergo grinding and dispersion treatment. The treatment method is as follows: mix the pigments and fillers, wetting and dispersing agents, and a portion of deionized water, add them to a grinding kettle, control the filling rate of the grinding media to 78%, set the rotation speed to 950 r / min, and grind to a fineness of 16 μm to obtain a pigment and filler slurry. Water-based additives include defoamers, leveling agents, thickeners, and pH adjusters; ammonia water is used as the pH adjuster to adjust the pH value of the system to 8.6.A method for preparing a low-VOCs acrylic resin waterborne coating includes the following steps: S1: Pre-emulsion preparation: The core layer monomer mixture and the shell layer monomer mixture are pre-emulsified according to the above parameters to obtain a core layer pre-emulsion and a shell layer pre-emulsion; S2: Modified acrylic resin emulsion preparation: Part of deionized water and part of emulsifier are added to a reaction vessel, the temperature is raised to 82°C, an initiator solution is added, and the core layer pre-emulsion is added dropwise using a starved state method, with the dropwise addition time controlled at 1.7 h; After the core layer is added, the temperature is maintained for 25 min, and then the temperature is gradually increased to 86°C, and the shell layer pre-emulsion and the remaining initiator solution are added dropwise, with the dropwise addition time controlled at 1.7 h; After the shell layer is added... Afterwards, the temperature was raised to 92℃ and kept at that temperature for 1 hour. Then, the temperature was lowered to 58℃, and a redox initiator system was added for post-elimination treatment. The mixture was stirred for 42 minutes, then cooled to below 40℃. The pH value was adjusted to 8.6 with ammonia water, and the mixture was filtered out. S3: Coating preparation: The modified acrylic resin emulsion obtained in S2 was added to the paint mixing tank. The stirring speed was set to 380 r / min. The pigment and filler slurry, water-based additives, and post-addition crosslinking agent prepared as described above were slowly added. After mixing evenly, the stirring speed was adjusted to 950 r / min and dispersed for 19 minutes. S4: Finished product packaging: The mixture obtained in S3 was allowed to stand for 50 minutes to degas. It was then filtered through a 200-mesh filter to obtain a low-VOCs acrylic resin water-based coating.

[0046] In this embodiment, by optimizing the functionalized internal plasticizer, based on the ratio of dodecanol and HDI in the shell monomer mixture (12%), and by precisely controlling the gradient heating and dropping time during the preparation of the modified acrylic resin emulsion, the perfect formation of the core-shell structure was ensured. This structural design enriches the particle surface of the low-VOCs acrylic resin waterborne coating with flexible segments, thus exhibiting good fusion at low temperatures, while retaining a high Tg core layer inside the particles (50°C), providing rigid support for the coating. Combined with the synergistic effect of the self-crosslinking functional monomer and the post-added crosslinking agent, the final coating exhibits excellent comprehensive performance in terms of drying speed, hardness establishment, and chemical resistance, making it suitable for industrial light corrosion protection or high-end building exterior wall coatings.

[0047] Comparative Example 1

[0048] This comparative example provides a water-based coating whose preparation process is basically the same as that of Example 1, except that: in the preparation of the shell monomer mixture, no functionalized internal plasticizer monomer is added, but instead, an equal mass of butyl acrylate is used. In order to achieve similar film-forming properties, an additional film-forming aid, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, accounting for 8% of the emulsion mass, is added during the paint formulation stage.

[0049] Comparative Example 2

[0050] This comparative example provides a water-based coating whose preparation process is basically the same as that of Example 1, except that: when preparing the shell monomer mixture, no self-crosslinking functional monomer is added, and an equal mass of methyl methacrylate is used instead; and no post-crosslinking agent is added during the paint mixing stage.

[0051] Comparative Example 3

[0052] This comparative example provides a water-based coating whose preparation process is basically the same as that of Example 1, except that: when preparing the shell monomer mixture, no functionalized internal plasticizer is added, but an equal mass of non-reactive plasticizer, dibutyl phthalate, is physically mixed into the shell monomer during the pre-emulsification stage.

[0053] Effect verification

[0054] To verify the performance of the low-VOCs acrylic resin waterborne coating of the present invention, performance tests were conducted on the coatings prepared in Examples 1-5 and Comparative Examples 1-3. The test results are shown in the table below:

[0055] Test Standards: 1. VOC Content: Tested according to GB18582-2020 "Limits of Hazardous Substances in Building Wall Coatings". 2. Minimum Film-Forming Temperature: Tested according to GB / T9267-2008. 3. Pencil Hardness: Tested according to GB / T6739-2006, with film formed on a glass plate and dried for 7 days. 4. Water Whitening Resistance: Film formed on a black glass plate, dried for 7 days, then immersed in water for 24 hours, observing the whitening of the film: no whitening > slight whitening > obvious whitening. 5. Anti-Adhesion: Fold the film in half, apply 500g of pressure, place at 50℃ for 4 hours, and observe the adhesion: no marks > slight marks > adhesion.

[0056]

[0057] As shown in the table above, the low-VOCs acrylic resin waterborne coatings prepared in Examples 1-5 of this invention successfully achieved low-temperature film formation at extremely low VOC content (<15g / L), with MFFT ≤ 4℃, by introducing functionalized internal plasticizers. Compared with Comparative Example 1, these examples achieved the same film-forming temperature without relying on a large amount of external film-forming aids, significantly reducing VOC emissions. Compared with Comparative Example 2, these examples, through the combination of self-crosslinking functional monomers and post-added crosslinking agents, significantly improved hardness after film formation, reaching H-2H and water resistance, solving the problems of soft film and poor water resistance caused by internal plasticizers. Compared with Comparative Example 3, this invention introduces internal plasticizer groups through chemical grafting, avoiding the problems of poor anti-tack and continuous decrease in hardness caused by the migration of physical plasticizers, ensuring the long-term stability of coating performance. In summary, this invention effectively balances the hardness, water resistance, and anti-tack properties of the coating while achieving the environmental goal of low VOCs.

[0058] Unless otherwise stated, all raw materials, reagents, and instruments used in the embodiments and comparative examples of this invention are commercially available products. Experimental methods not specifically described in the embodiments are generally performed under conventional conditions or as recommended by the manufacturer.

[0059] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A low VOCs acrylic resin water-based paint, characterized by: The product comprises the following raw materials in parts by weight: 40-80 parts modified acrylic resin emulsion, 0-30 parts pigments and fillers, 1-5 parts water-based additives, 10-30 parts deionized water, and 0.5-2 parts post-addition crosslinking agent; the modified acrylic resin emulsion is obtained by core-shell emulsion polymerization of a core-layer monomer mixture and a shell-layer monomer mixture, wherein the shell-layer monomer mixture contains functionalized internal plasticizers and self-crosslinking functional monomers; the functionalized internal plasticizer is obtained by reacting long-chain fatty alcohols with diisocyanates to obtain isocyanate-terminated prepolymers, and then grafting the isocyanate-terminated prepolymers with hydroxyl-containing acrylic monomers; The long-chain fatty alcohol is selected from at least one of dodecanol, tetradecanol, or hexadecylol; the diisocyanate is selected from isophorone diisocyanate or hexamethylene diisocyanate; the hydroxyl-containing acrylic monomer is selected from hydroxyethyl acrylate or hydroxyethyl methacrylate; the molar ratio of the long-chain fatty alcohol, diisocyanate, and hydroxyl-containing acrylic monomer is 1:(1-1.1):(1-1.1); The preparation process of the modified acrylic resin emulsion includes a pre-emulsification operation, which is as follows: A core layer monomer mixture is mixed with an emulsifier and deionized water, and sheared at 1000–1200 r / min for 15–20 min using a high-speed disperser to obtain a core layer pre-emulsion; a shell layer monomer mixture is mixed with an emulsifier and deionized water, and sheared at 1000–1200 r / min for 15–20 min to obtain a shell layer pre-emulsion; in the shell layer monomer mixture, the mass of the functionalized internal plasticizer accounts for 5–15% of the total mass of the shell layer monomers, and the mass of the self-crosslinking functional monomer accounts for 2–6% of the total mass of the shell layer monomers. The core layer monomer mixture is selected from at least two of methyl methacrylate, styrene, and butyl acrylate, and the glass transition temperature (Tg) of the core layer copolymer is designed to be ≥30℃; the self-crosslinking functional monomer is selected from at least one of diacetone acrylamide and ethyl acetoacetate; the post-added crosslinking agent is adipic acid dihydrazide.

2. The low VOCs acrylic resin water-based paint according to claim 1, characterized by, The preparation process of the functionalized internal plasticizer monomer is as follows: long-chain fatty alcohol is added to a reaction vessel, nitrogen gas is introduced for protection, the temperature is raised to 50-60°C, dibutyltin dilaurate (0.01%-0.05% of the total monomer mass) is added, and diisocyanate is slowly added dropwise. After the addition is complete, the temperature is raised to 75-85°C and the reaction is maintained for 2-3 hours to obtain a terminal isocyanate prepolymer. Then the temperature is lowered to 40-50°C, hydroxyl-containing acrylic monomer and polymerization inhibitor (hydroquinone methyl ether or phenothiazine) are added, the temperature is raised to 65-75°C, and the reaction is maintained for 3-5 hours until the characteristic peak of the -NCO group disappears in the infrared spectrum, thus obtaining the functionalized internal plasticizer monomer.

3. The low-VOCs acrylic resin waterborne coating according to claim 1, characterized in that, Before use, the pigments and fillers are ground and dispersed. The treatment method is as follows: the pigments and fillers, wetting and dispersing agents and some deionized water are mixed and added to the grinding kettle. The filling rate of the grinding medium is controlled at 70-80%, the rotation speed is set at 800-1000 r / min, and the grinding is carried out until the fineness is ≤20μm to obtain the pigment and filler slurry.

4. The low-VOCs acrylic resin waterborne coating according to claim 1, characterized in that, The aqueous additives include defoamers, leveling agents, thickeners, and pH adjusters; the pH adjuster is selected from ammonia or 2-amino-2-methyl-1-propanol, used to adjust the pH value of the system to 8.0-9.

0.

5. A method for preparing a low-VOCs acrylic resin waterborne coating according to claim 1, characterized in that, Includes the following steps: S1: Preparation of pre-emulsion: The core layer monomer mixture and the shell layer monomer mixture are pre-emulsified to obtain core layer pre-emulsion and shell layer pre-emulsion; S2: Preparation of modified acrylic resin emulsion: Add some deionized water and some emulsifier to the reactor, heat to 80-82℃, add initiator solution, and start adding the core layer pre-emulsion dropwise by starvation method, with the dropwise addition time controlled at 1.5-2h; after the core layer is added, keep warm for 15-30min, then heat uniformly to 84-86℃ within 10-20min, start adding the shell layer pre-emulsion and the remaining initiator solution dropwise, with the dropwise addition time controlled at 1.5-2h; after the shell layer is added, heat to 90-92℃, keep the reaction at this temperature for 1h, then cool to 50-60℃, add redox initiator system for post-elimination treatment, stir for 30-45min, cool to below 40℃, adjust the pH value to 7.5-8.5 with ammonia water, and filter out the material; S3: Coating preparation: Add the modified acrylic resin emulsion obtained in S2 to the paint mixing tank, set the stirring speed to 300-400 r / min, slowly add pigment and filler slurry, water-based additives and post-addition crosslinking agent, mix evenly, adjust the speed to 800-1000 r / min and disperse for 15-20 min. S4: Finished product packaging: Let the mixture obtained in S3 stand for 30-60 minutes to degas, then filter it through a 200-mesh filter to obtain a low-VOCs acrylic resin water-based coating.

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