Low voc waterborne acrylic modified zinc-molybdate intermediate paint and preparation method thereof

Abstract

The present application relates to the technical field of paint, in particular to low VOC water-based acrylic modified cloud iron intermediate paint and its preparation method, which solves the technical problems of high VOC, poor dispersion stability of cloud iron powder, insufficient film forming property of emulsion and unreasonable preparation process of existing water-based cloud iron intermediate paint. The intermediate paint is composed of multiple components such as microwave-assisted core-shell cross-linked modified water-based acrylic emulsion, plasma-coupling agent-nanoparticle composite pretreated cloud iron powder, etc. according to mass fraction. The preparation process is integrated with microwave-assisted core-shell cross-linking, plasma composite modification, ultrasonic-mechanical synergistic dispersion, etc. The product is obtained through emulsion preparation, cloud iron powder pretreatment, base preparation, mixing and grinding, and finished product adjustment. The product has VOC≤45g / L, adhesion 0-1 level, salt spray resistance≥1100h, water resistance≥260h, excellent corrosion resistance and environmental protection performance, simple and controllable preparation process, and is suitable for metal component corrosion-resistant coating and industrial large-scale production.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a low-VOC waterborne acrylic modified micaceous iron oxide intermediate paint and its preparation method. Background Technology

[0002] In metal component anti-corrosion coating systems, micaceous iron oxide intermediate paint, with its flaky micaceous iron oxide powder, can form a dense "labyrinth-like" shielding layer, effectively blocking the penetration of corrosive media. It has become a core coating material connecting the primer and topcoat, enhancing the overall anti-corrosion performance of the coating. With increasingly stringent global environmental regulations, traditional solvent-based micaceous iron oxide intermediate paints, due to their high VOC content and the release of large amounts of harmful volatile substances during application, which pose serious threats to human health and the environment, have been gradually replaced by water-based micaceous iron oxide intermediate paints, becoming the mainstream direction of industry development.

[0003] Currently, most existing waterborne micaceous iron oxide intermediate paints use ordinary waterborne acrylic emulsions as film-forming resins. However, they still face several insurmountable technical bottlenecks in practical applications: First, ordinary waterborne acrylic emulsions lack sufficient film density. To ensure adequate film formation, a large amount of high-VOC film-forming aids must be added, making it difficult to achieve a significant reduction in VOC content. Most products still have VOC contents exceeding 50g / L, failing to meet increasingly stringent environmental standards. Second, micaceous iron oxide powder, as a hydrophobic flake pigment, has poor compatibility with hydrophilic waterborne acrylic emulsions. Existing technologies often employ single silane coupling agents for surface modification, but the modification effect is limited and cannot fundamentally solve the problem of micaceous iron oxide powder... Agglomeration and sedimentation in water-based systems lead to a decrease in the shielding performance of the coating, affecting its corrosion resistance and durability. Thirdly, the existing modification methods for water-based acrylic emulsions are relatively simple, mostly using core-shell polymerization or simple copolymerization modification. The crosslinking density of the emulsion is insufficient, resulting in the need to further improve the water resistance, corrosion resistance, and adhesion of the prepared intermediate paint. Fourthly, in terms of preparation process, existing methods mostly use simple mechanical stirring and dispersion, resulting in poor mixing uniformity between micaceous iron powder and emulsion. Moreover, acrylic emulsion polymerization mostly uses traditional water bath heating methods, which result in low polymerization efficiency and uneven molecular weight distribution of the emulsion, leading to poor product performance stability and large performance fluctuations between different batches of products, making it difficult to meet the needs of large-scale industrial production.

[0004] To address the aforementioned issues, while some existing technologies attempt to reduce VOC content or improve dispersion performance, they all have significant limitations. For example, some solutions reduce VOC by decreasing the amount of film-forming aids, but this leads to insufficient emulsion film formation, resulting in defects such as cracking and peeling of the coating. Some solutions use novel coupling agents to improve the pretreatment effect of micaceous iron oxide powder, but without simultaneously optimizing the emulsion modification method, resulting in limited improvement in the overall coating performance. Other solutions employ complex modification processes to improve emulsion performance, but these processes are cumbersome and costly, hindering industrial-scale promotion. Furthermore, existing technologies have not yet combined plasma surface treatment, bio-based modifiers, and nanoparticles in the pretreatment of micaceous iron oxide powder, nor have they combined microwave-assisted polymerization with core-shell polymerization and crosslinking modification. They also lack the integrated application of ultrasonic-mechanical synergistic dispersion and segmented heating processes. These technologies, which are not commonly used in this field, could potentially achieve simultaneous breakthroughs in VOC content and overall performance if rationally integrated into the preparation of waterborne micaceous iron oxide intermediate coatings.

[0005] Meanwhile, with the development of the green chemical industry, bio-based materials, due to their environmental and renewable advantages, are gradually gaining attention in the coatings field. However, the application of bio-based film-forming aids in existing waterborne micaceous iron oxide intermediate paints is limited, and most are single bio-based components, resulting in poor film-forming effects and difficulty in achieving both low VOC and excellent film-forming performance. Furthermore, the selection of functional fillers is relatively traditional, without targeted modification treatment, failing to fully leverage the filler's role in enhancing the coating's shielding and mechanical properties. Therefore, developing a low-VOC waterborne acrylic-modified micaceous iron oxide intermediate paint and its preparation method that employs a novel modification approach and preparation process, integrates multiple innovative technologies, combines bio-based materials with uncommon techniques, and achieves significant VOC reduction, good dispersion stability, excellent corrosion resistance and durability, and a simple and controllable preparation process has become a crucial technical challenge urgently needing to be addressed in the coatings industry, possessing significant environmental and industrial application value. Summary of the Invention

[0006] The purpose of this invention is to overcome the technical defects of existing waterborne micaceous iron oxide intermediate paints, such as difficulty in achieving deep VOC reduction, poor dispersion stability of micaceous iron oxide powder, insufficient emulsion film-forming performance, and unreasonable preparation processes. This invention provides a low-VOC waterborne acrylic-modified micaceous iron oxide intermediate paint and its preparation method. It achieves a significant reduction in VOC content and a substantial improvement in overall performance of the intermediate paint, with a simple and controllable preparation process and moderate cost, meeting the needs of large-scale industrial production and practical applications.

[0007] The technical solution adopted by this invention to solve its technical problem is: a low-VOC waterborne acrylic modified micaceous iron oxide intermediate paint, comprising the following components in parts by mass: 42-58 parts of microwave-assisted core-shell crosslinking modified waterborne acrylic emulsion, 22-32 parts of plasma-coupling agent-nanoparticle composite pretreated micaceous iron oxide powder, 1.8-4.5 parts of compounded low-VOC film-forming aid, 0.6-1.6 parts of waterborne dispersant, 0.4-0.9 parts of organosilicon defoamer, 1.2-3.2 parts of composite rust inhibitor, 4.8-10.5 parts of functional modified filler, and 7.5-14.5 parts of deionized water; The emulsion is prepared using a microwave-assisted segmented heating core-shell polymerization process. The core monomer is a mixture of methyl methacrylate and butyl acrylate, and the shell monomer is a mixture of hydroxyethyl acrylate, γ-methacryloyloxypropyltrimethoxysilane, and maleic anhydride. An amino resin crosslinking agent is added, and the microwave power and segmented temperature are controlled during the polymerization process. The composite pretreated micaceous iron powder is first etched by plasma surface etching, and then modified by water-based silane coupling agent, nano-silica and carboxymethyl chitosan. The compounded low-VOC film-forming aid is a compound system of polyethylene glycol monomethyl ether, tributyl citrate and propylene glycol butyl ether, with a VOC content ≤45g / L; The functional modified filler is a compound of bentonite and diatomaceous earth modified with silane coupling agent.

[0008] Specifically, the mass ratio of the core layer to the shell layer monomers is 1:(0.6-0.8), the amount of maleic anhydride is 8-15% of the total mass of the shell layer monomers, and the amount of amino resin crosslinking agent is 3-7% of the total mass of the core and shell monomers.

[0009] Specifically, the plasma etching parameters are: power 80-120W, time 8-15min, atmosphere is air; waterborne silane coupling agent is KH560, the mass ratio of nano-silica to KH560 is 1:(2-3), carboxymethyl chitosan concentration is 1.5-3.0%, and composite modification time is 2-3h.

[0010] Specifically, in the compound film-forming aid, the mass ratio of polyethylene glycol monomethyl ether, tributyl citrate and propylene glycol butyl ether is 1:(0.8-1.2):(0.5-1.0), and the boiling point is ≥220℃.

[0011] Specifically, the composite rust inhibitor is a compound of aluminum tripolyphosphate, zinc phosphate and zinc molybdate in a mass ratio of 2:3:(1-2); the water-based dispersant is a polycarboxylate.

[0012] Specifically, in the functional modified filler, the mass ratio of bentonite to diatomaceous earth is 1:(1.2-2.0), and the amount of silane coupling agent is 2-4% of the total mass of the filler.

[0013] The preparation method of the low-VOC waterborne acrylic modified micaceous iron oxide intermediate paint includes the following steps: Step 1, Preparation of microwave-assisted core-shell crosslinking modified emulsion: Add deionized water and compound emulsifier to a reactor equipped with a microwave reactor, dissolve, and heat to 70-75℃. Add part of the core layer monomer and initiator, microwave power 180-220W, and maintain the temperature for 0.8-1.2h. Add the remaining core layer monomer dropwise, heat to 80-85℃, and maintain the temperature for 0.5-1h. Add the shell layer monomer and amino resin dropwise, microwave power 150-180W, heat to 85-90℃, and maintain the temperature for 1.0-1.5h. Cool down and adjust the pH to 7.0-7.8, then filter and discharge. Step 2, Preparation of composite pretreated micaceous iron powder: After plasma etching, micaceous iron powder is mixed with coupling agent, nano-silica and carboxymethyl chitosan solution, modified at 35-55℃ for 2-3 hours, dried, pulverized and sieved. Step 3, Preparation of base material: Add emulsion to dispersion vessel, turn on ultrasonic-mechanical synergistic dispersion, add dispersant, defoamer, film-forming aid and rust inhibitor, keep warm and stir for 0.4-0.9h; Step 4, Mixing and Grinding: Add pretreated micaceous iron powder and functional fillers, disperse synergistically for 1.0-1.4 hours, and grind in a sand mill until the fineness is ≤38μm; Step 5, Finished product preparation: Add the remaining deionized water, adjust the viscosity to 19-29s, and filter to obtain the finished product.

[0014] Specifically, in step 1, the compound emulsifier is a compound of fatty alcohol polyoxyethylene ether and alkyl glycoside in a mass ratio of 2:(1-1.5), and the amount used is 2.2-3.2% of the total mass of the core-shell monomers; the initiator is ammonium persulfate or potassium persulfate, and the amount used is 0.7-1.2% of the total mass of the monomers.

[0015] Specifically, in step 3, the ultrasonic power is 150-200W, the stirring speed is 600-850r / min, and the heat preservation temperature is 42-52℃.

[0016] Specifically, in step 4, the ultrasonic power is 220-280W, the stirring speed is 1400-1900r / min, the sand mill speed is 1900-2400r / min, and the grinding time is 0.9-1.8h.

[0017] The beneficial effects of this invention are: The prepared intermediate paint has a VOC content of ≤45g / L, achieving a significant reduction that is far below industry standards. There is no obvious release of harmful gases during construction, demonstrating excellent environmental performance. It also possesses excellent adhesion (0-1 grade), salt spray resistance (≥1100h), and water resistance (≥260h), outstanding shielding performance, effectively connecting the primer and topcoat, greatly improving the anti-corrosion durability of the coating system, and extending the service life of metal components. Microwave-assisted core-shell crosslinking modified emulsion balances the flexibility of the core-shell structure with the density of crosslinking modification. Microwave polymerization improves efficiency and stability, while organosilicon and the dual crosslinking system enhance water resistance and reduce the amount of film-forming aids. Composite pretreated micaceous iron powder, through the synergistic effect of plasma, coupling agents, nanoparticles and bio-based modifiers, completely solves the agglomeration problem, significantly improves dispersion stability and compatibility, and the synergy of both achieves a breakthrough in comprehensive performance. The compounded low-VOC film-forming aid combines bio-based and environmentally friendly ester components, taking into account both low VOC and film-forming performance, and avoiding the defects of single aids; the synergistic application of functional modified fillers and composite rust inhibitors further improves the coating's shielding and anti-corrosion performance, taking into account both performance and production cost. The preparation process integrates a variety of methods not commonly used in this technology, such as microwave-assisted segmented polymerization and ultrasonic-mechanical synergistic dispersion, to improve production efficiency and product stability. The steps are clear and the operation is simple, requiring no complex equipment, making it suitable for large-scale industrial production. It has significant environmental and industrial application value. Attached Figure Description

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0019] Figure 1 The flowchart illustrates the preparation method of the low-VOC waterborne acrylic modified micaceous iron oxide intermediate paint provided by this invention. Detailed Implementation

[0020] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0021] The low-VOC waterborne acrylic modified micaceous iron oxide intermediate paint of the present invention is composed of the following components by weight: 42-58 parts of microwave-assisted core-shell crosslinking modified waterborne acrylic emulsion, 22-32 parts of plasma-coupling agent-nanoparticle composite pretreated micaceous iron oxide powder, 1.8-4.5 parts of compounded low-VOC film-forming aid, 0.6-1.6 parts of waterborne dispersant, 0.4-0.9 parts of organosilicon defoamer, 1.2-3.2 parts of composite rust inhibitor, 4.8-10.5 parts of functional modified filler, and 7.5-14.5 parts of deionized water.

[0022] A microwave-assisted segmented heating core-shell polymerization process combined with synergistic crosslinking modification overcomes the limitations of traditional polymerization and modification methods. Microwave-assisted polymerization offers advantages such as uniform heating, high polymerization efficiency, and low energy consumption, promoting rapid monomer polymerization, effectively controlling polymer molecular weight distribution, and improving emulsion stability. The segmented heating core-shell polymerization process allows core and shell monomers to polymerize sequentially, forming a uniformly structured core-shell emulsion that balances both hardness and flexibility. Synergistic crosslinking modification, through the synergistic effect of organosilicon monomers, maleic anhydride, and amino resins, significantly increases the crosslinking density of the emulsion, enhances film density and water resistance, reduces the amount of film-forming aids, and provides support for VOC reduction.

[0023] The core monomer is a mixture of methyl methacrylate and butyl acrylate, with a carefully balanced mass ratio. Methyl methacrylate enhances the emulsion's hardness and abrasion resistance, while butyl acrylate improves its flexibility and film-forming properties. The shell monomer is a mixture of hydroxyethyl acrylate, γ-methacryloyloxypropyltrimethoxysilane (an organosilicon monomer), and maleic anhydride. Hydroxyethyl acrylate introduces hydroxyl groups, providing active sites for the crosslinking reaction. The organosilicon monomer reduces the emulsion's surface tension and improves its water and corrosion resistance. Maleic anhydride introduces carboxyl and anhydride groups, participating in the crosslinking reaction. The mass ratio of core to shell monomers is controlled at 1:(0.6-0.8) to ensure the integrity of the core-shell structure. The amount of maleic anhydride is 8-15% of the total mass of the shell monomers, and the amount of amino resin crosslinking agent is 3-7% of the total mass of the core and shell monomers. This avoids over-crosslinking, which can lead to brittle emulsion films and achieves a synergistic balance between flexibility and density. During polymerization, microwave power and segmented temperatures are controlled to ensure sufficient monomer polymerization and uniform crosslinking reaction.

[0024] The plasma-coupling agent-nanoparticle composite pretreatment of micaceous iron powder breaks through the limitations of traditional single modification. It combines plasma surface etching, water-based silane coupling agent modification, nanoparticle filling, and bio-based modifier to achieve a leapfrog improvement in the dispersion performance and compatibility of micaceous iron powder. Plasma surface etching can form micro-etching pits on the surface of micaceous iron powder, increasing the specific surface area and introducing active groups such as hydroxyl and carboxyl groups, providing sites for subsequent modification. The water-based silane coupling agent (KH560) can react with the active groups on the surface of micaceous iron powder and nano-silica to build connecting bridges. Nano-silica fills the pores on the surface of micaceous iron powder, improving the density of the modified layer. Carboxymethyl chitosan (bio-based modifier) ​​has the advantages of being environmentally friendly and having good compatibility. Its hydrophilic groups further enhance the hydrophilicity of micaceous iron powder. The four factors work synergistically to completely solve the problems of micaceous iron powder agglomeration and sedimentation.

[0025] The plasma etching parameters are controlled as follows: power 80-120W, time 8-15min, atmosphere is air, to ensure uniform surface etching and not damage the structure of micaceous iron powder; the mass ratio of water-based silane coupling agent KH560 to nano silica is 1:(2-3), the concentration of carboxymethyl chitosan is 1.5-3.0%, the composite modification time is 2-3h, and the temperature is 35-55℃, to ensure that each modified component fully adheres and reacts to form a uniform and stable modified surface layer. After pretreatment, the surface is dried, pulverized and sieved to further improve the dispersion uniformity.

[0026] To achieve a significant reduction in VOCs while maintaining film-forming performance, this invention employs a compound system of polyethylene glycol monomethyl ether (bio-based), tributyl citrate (bio-based), and propylene glycol butyl ether (environmentally friendly ester) to replace traditional high-VOC film-forming aids. The mass ratio of the three is 1:(0.8-1.2):(0.5-1.0). Polyethylene glycol monomethyl ether and tributyl citrate synergistically enhance film-forming solubility, lowering the film-forming temperature and improving coating flexibility. Propylene glycol butyl ether further improves film-forming efficiency. The compounded film-forming aid has a VOC content ≤45g / L and a boiling point ≥220℃. This system ensures sufficient film formation of the emulsion while reducing the amount of aid used, preventing coating cracking and peeling, and achieving a synergistic improvement in both low VOCs and excellent film-forming performance.

[0027] The aqueous dispersant uses polycarboxylate salts, which have high dispersion efficiency and good stability, further improving the dispersibility of micaceous iron powder and functional modified fillers after pretreatment and avoiding particle agglomeration. The organosilicon defoamer uses polyether-modified organosilicon, which has good defoaming effect and long foam suppression time, without affecting film formation performance and appearance, and eliminating bubble defects in the preparation process. The composite rust inhibitor combines the rust prevention advantages of the two schemes, using a compound of aluminum tripolyphosphate, zinc phosphate and zinc molybdate in a mass ratio of 2:3:(1-2). The three work synergistically to form a stable passivation film and improve corrosion resistance and durability. The functional modified filler uses a compound of bentonite and diatomaceous earth modified with silane coupling agent. Bentonite improves shielding performance and fills coating pores, while diatomaceous earth adsorbs corrosive media. The mass ratio of the two is 1:(1.2-2.0). The amount of silane coupling agent is 2-4% of the total mass of the filler, which improves the compatibility between the filler and the emulsion, enhances the interfacial bonding force, and balances performance and cost.

[0028] like Figure 1 As shown, this invention also provides a method for preparing the above-mentioned low-VOC waterborne acrylic modified micaceous iron oxide intermediate paint, which integrates microwave-assisted polymerization, ultrasonic-mechanical synergistic dispersion, segmented heating, and gradient dispersion processes. The steps are clear, highly repeatable, and ensure stable product performance. Specifically, it includes the following steps: Step 1: Preparation of microwave-assisted core-shell crosslinked modified aqueous acrylic emulsion: Deionized water and a compound emulsifier (a mixture of fatty alcohol polyoxyethylene ether and alkyl glycoside, mass ratio 2:(1-1.5)) are added to a reaction vessel equipped with a microwave reactor, stirring device, thermometer, and dropping funnel. The amount added is 2.2-3.2% of the total mass of the core-shell monomers. After stirring and dissolving, the temperature is slowly raised to 70-75℃. 30-35% of the core layer monomer and 40-45% of the initiator solution (ammonium persulfate or potassium persulfate dissolved in deionized water) are added. The amount of initiator is 0.7-1.2% of the total mass of the core-shell monomers. The microwave power is adjusted to 180-220W, and the reaction is maintained at this temperature for 0.8-1.2 hours. Seed emulsion was obtained; then, the remaining core monomer and 25-30% initiator solution were added dropwise at a uniform rate. After the addition was complete, the temperature was raised to 80-85℃ and the reaction was maintained for 0.5-1h to ensure that the core monomer was fully polymerized. Then, all shell monomers, amino resin crosslinking agent and the remaining initiator solution were added dropwise at a uniform rate. The microwave power was adjusted to 150-180W, the temperature was raised to 85-90℃, and the reaction was maintained for 1.0-1.5h to ensure that the crosslinking reaction was fully carried out. After the reaction was completed, the temperature was lowered to 45-55℃, the pH value was adjusted to 7.0-7.8 with diethanolamine or ammonia, and the material was filtered through a 200-mesh filter to remove unpolymerized monomers and impurities, resulting in a microwave-assisted core-shell crosslinked modified waterborne acrylic emulsion for later use.

[0029] Step 2, Preparation of plasma-coupling agent-nanoparticle composite pretreated micaceous iron powder: Place the micaceous iron powder in a plasma treatment instrument and perform surface etching treatment according to the set parameters (power 80-120W, time 8-15min, atmosphere air). Remove and cool to room temperature. Add the cooled micaceous iron powder to the prepared mixed modification solution (water-based silane coupling agent KH560, nano-silica and carboxymethyl chitosan solution), adjust the temperature to 35-55℃, and stir at a constant temperature for 2-3 hours. During this period, increase the stirring speed by 200r / min every 30 minutes for 5-10 minutes to ensure uniform adhesion and reaction of the modified components. After modification, filter out the micaceous iron powder, place it in an 85-95℃ oven to dry for 2-3 hours, pulverize after drying, and pass it through a 1000-mesh sieve to remove coarse particles, obtaining composite pretreated micaceous iron powder for later use.

[0030] Step 3, Preparation of intermediate paint base material: Add the modified emulsion prepared in Step 1 to a dispersion vessel equipped with an ultrasonic dispersion device and a mechanical stirring device. Turn on the ultrasonic and mechanical stirring device, adjust the ultrasonic power to 150-200W, and the stirring speed to 600-850r / min. Under low-speed stirring, add the aqueous dispersant, organosilicon defoamer, compound low-VOC film-forming aid, and composite rust inhibitor in sequence. After each component is added, continue ultrasonic stirring for 15-20min to ensure that each component is fully dissolved and mixed. After all components have been added, adjust the temperature to 42-52℃ and keep it at this temperature while stirring for 0.4-0.9h to promote the full compatibility of the additives and the emulsion and improve the stability of the base material, thus obtaining the intermediate paint base material for later use.

[0031] Step 4, Mixing and Grinding: Slowly add the pretreated micaceous iron powder and functional modified filler prepared in Step 2 to the base material obtained in Step 3. Adjust the ultrasonic power to 220-280W and the stirring speed to 1400-1900r / min. Perform ultrasonic-mechanical synergistic dispersion for 1.0-1.4h, stopping the machine every 30min to check the dispersion effect to ensure that there are no obvious agglomerated particles. Then, send the material into a horizontal sand mill, adjust the grinding speed to 1900-2400r / min, and grind for 0.9-1.8h until the fineness of the material is ≤38μm. Stop grinding to obtain the ground material for later use.

[0032] Step 5, Finished Product Preparation: The ground material obtained in Step 4 is fed into a dispersion vessel, the remaining deionized water is added, the ultrasonic power is adjusted to 150-200W, the stirring speed is 600-850r / min, and the mixture is stirred at low speed for 15-20min. The viscosity is tested using a Forte 4 cup (25℃) and adjusted to 19-29s, which meets the construction requirements. Then, the mixture is filtered through a 200-mesh filter to remove impurities and undispersed particles, resulting in a low-VOC waterborne acrylic modified micaceous iron oxide intermediate paint. The finished product is placed in a sealed container and stored in a cool, dry place.

[0033] Example 1: This embodiment provides a low-VOC waterborne acrylic modified micaceous iron oxide intermediate paint and its preparation method. By mass, the intermediate paint is composed of the following components: 48 parts of microwave-assisted core-shell crosslinking modified waterborne acrylic emulsion, 26 parts of plasma-coupling agent-nanoparticle composite pretreated micaceous iron oxide powder, 3.2 parts of compounded low-VOC film-forming aid, 1.1 parts of waterborne dispersant, 0.6 parts of organosilicon defoamer, 2.1 parts of composite rust inhibitor, 7.8 parts of functional modified filler, and 11.2 parts of deionized water.

[0034] The microwave-assisted core-shell crosslinking modified emulsion comprises a core layer monomer of methyl methacrylate and butyl acrylate in a mass ratio of 1:1; a shell layer monomer of hydroxyethyl acrylate, γ-methacryloyloxypropyltrimethoxysilane, and maleic anhydride in a mass ratio of 5:2:1.5; a core-shell monomer mass ratio of 1:0.7; maleic anhydride accounting for 11% of the total mass of the shell layer monomers; an amino resin crosslinking agent (melamine-formaldehyde resin) accounting for 5% of the total mass of the core-shell monomers; a compound emulsifier of fatty alcohol polyoxyethylene ether (AEO-9) and alkyl glycoside (APG-1214) in a mass ratio of 2:1.2, accounting for 2.7% of the total mass of the core-shell monomers; and an initiator of ammonium persulfate with a solution concentration of 10%, accounting for 0.9% of the total mass of the core-shell monomers.

[0035] Plasma etching parameters for composite pretreated micaceous iron powder: power 100W, time 12min, atmosphere air; mass ratio of waterborne silane coupling agent KH560 to nano silica 1:2.5; carboxymethyl chitosan concentration 2.2%, composite modification time 2.5h, temperature 45℃; micaceous iron powder of 325 mesh flakes was selected. The compound film-forming aid consists of polyethylene glycol monomethyl ether (MPEG-400), tributyl citrate, and propylene glycol butyl ether in a mass ratio of 1:1:0.7; the water-based dispersant is a polycarboxylate (BYK-P104); the organosilicon defoamer is polyether-modified organosilicon (BYK-028); the composite rust inhibitor consists of aluminum tripolyphosphate, zinc phosphate, and zinc molybdate in a mass ratio of 2:3:1.5; the functional modified filler consists of bentonite and diatomaceous earth modified with silane coupling agent (KH550) in a mass ratio of 1:1.6, with KH550 accounting for 3% of the total filler mass and having a particle size of 1200 mesh.

[0036] The preparation method includes the following steps: Step 1, Preparation of microwave-assisted core-shell crosslinking modified emulsion: Deionized water and a compound emulsifier were added to a 500 mL reactor equipped with a microwave reactor, stirring device, thermometer, and dropping funnel. Stirring was started at 650 r / min for 15 min until the emulsifier was completely dissolved. The temperature was slowly raised to 72℃, and 32% of the core layer monomer and 42% of the initiator solution (ammonium persulfate dissolved in deionized water, concentration 10%) were added. The microwave power was adjusted to 200 W, and the reaction was maintained at this temperature for 1.0 h to obtain a homogeneous seed emulsion. Subsequently, the remaining core layer monomer and 28% of the initiator solution were added dropwise at a rate of 0.9 mL / min. After the addition was complete, the temperature was raised to... The reaction was carried out at 82℃ for 0.8 hours to ensure sufficient core-layer polymerization. Then, all shell monomers, melamine-formaldehyde resin crosslinking agent, and the remaining 30% of initiator solution were added dropwise at a rate of 0.9 mL / min. The microwave power was adjusted to 165 W, the temperature was raised to 87℃, and the reaction was carried out at this temperature for 1.2 hours. During this period, the stirring speed was increased to 800 r / min every 20 minutes for 5 minutes to ensure uniform crosslinking. After the reaction was completed, the temperature was lowered to 50℃, the pH was adjusted to 7.4 with diethanolamine, and the mixture was filtered through a 200-mesh filter to obtain a transparent and uniform modified emulsion for later use. The solid content of the emulsion was 48%, and the viscosity was 250 mPa·s (25℃).

[0037] Step 2, Preparation of composite pretreated micaceous iron oxide powder: 325-mesh flaky micaceous iron oxide powder was placed in a plasma treatment instrument, with a power of 100W, a time of 12 minutes, and an air atmosphere for surface etching. After removal, it was cooled to room temperature. A mixed modification solution (KH560, nano-silica, and carboxymethyl chitosan solution) was prepared. The cooled micaceous iron oxide powder was added to the mixed modification solution, and the temperature was adjusted to 45℃. The mixture was stirred at a constant temperature for 2.5 hours. During this period, the stirring speed was increased from 1000 r / min to 1200 r / min every 30 minutes for 8 minutes, and then returned to 1000 r / min. After modification, the micaceous iron oxide powder was removed by vacuum filtration, placed in a 90℃ oven for drying for 2.5 hours, pulverized after drying, and passed through a 1000-mesh sieve to obtain pretreated micaceous iron oxide powder for later use. Its water contact angle was measured to be 63°, indicating a significant improvement in hydrophilicity and dispersibility.

[0038] Step 3, Preparation of intermediate paint base material: Add the modified emulsion prepared in Step 1 to a 1000mL dispersion vessel equipped with an ultrasonic and mechanical stirring device. Turn on the ultrasonic and stirring, with an ultrasonic power of 180W and a stirring speed of 750r / min. Under low-speed stirring, add the water-based dispersant, organosilicon defoamer, compound film-forming aid, and composite rust inhibitor in sequence. After each component is added, continue ultrasonic stirring for 18min to ensure full dissolution and mixing. After all components are added, adjust the temperature to 48℃ and keep stirring at this temperature for 0.7h to obtain a uniform and transparent base material for later use. The viscosity of the base material is measured to be 320mPa·s (25℃).

[0039] Step 4, Mixing and Grinding: Slowly add pretreated micaceous iron powder and functional modified filler to the base material, adjust the ultrasonic power to 250W, the stirring speed to 1700r / min, and perform ultrasonic-mechanical synergistic dispersion for 1.2h, stopping the machine every 30min during this period and using a scraper fineness gauge to check the dispersion effect to ensure that there are no agglomerated particles; then send the material into a horizontal sand mill, grind at 2200r / min for 1.5h, taking samples every 30min to check the fineness until the fineness reaches 32μm (≤38μm), then stop grinding and set aside for later use.

[0040] Step 5, Finished Product Preparation: The ground material is fed into a dispersion vessel, the remaining deionized water is added, the ultrasonic power is adjusted to 180W, the stirring speed is 750r / min, and the mixture is stirred at low speed for 18min. The viscosity is tested with a Forte 4 cup (25℃) and adjusted to 24s, which meets the construction requirements. The mixture is then filtered through a 200-mesh filter to remove impurities, resulting in a uniform, fine, bubble-free, low-VOC waterborne acrylic modified micaceous iron oxide intermediate paint. The paint is then packaged into a sealed plastic bucket and stored in a cool, dry place.

[0041] Performance testing: VOC content 36g / L, adhesion grade 0, salt spray resistance 1250h (no bubbling, no rust), water resistance 280h (no abnormalities), fineness 32μm, viscosity 24s, good storage stability (no delamination at 50℃ for 7 days). All performance characteristics are superior to existing technologies, with outstanding environmental protection and anti-corrosion performance, suitable for corrosion protection of metal components such as ships and bridges.

[0042] Example 2: This embodiment provides a low-VOC waterborne acrylic modified micaceous iron oxide intermediate paint and its preparation method. By mass, the intermediate paint is composed of the following components: 42 parts of microwave-assisted core-shell crosslinking modified waterborne acrylic emulsion, 22 parts of plasma-coupling agent-nanoparticle composite pretreated micaceous iron oxide powder, 1.8 parts of compounded low-VOC film-forming aid, 0.6 parts of waterborne dispersant, 0.4 parts of organosilicon defoamer, 1.2 parts of composite rust inhibitor, 4.8 parts of functional modified filler, and 7.5 parts of deionized water.

[0043] The microwave-assisted core-shell crosslinking modified emulsion comprises a core monomer of methyl methacrylate and butyl acrylate in a mass ratio of 1.2:1; a shell monomer of hydroxyethyl acrylate, γ-methacryloyloxypropyltrimethoxysilane, and maleic anhydride in a mass ratio of 4:1:1; a core-to-shell monomer mass ratio of 1:0.6; maleic anhydride accounting for 8% of the total mass of the shell monomers; an amino resin crosslinking agent (urea-formaldehyde resin) accounting for 3% of the total mass of the core-shell monomers; a compound emulsifier of fatty alcohol polyoxyethylene ether (AEO-7) and alkyl glycoside (APG-10) in a mass ratio of 2:1, accounting for 2.2% of the total mass of the core-shell monomers; and potassium persulfate as the initiator, with an initiator solution concentration of 8%, accounting for 0.7% of the total mass of the core-shell monomers.

[0044] Plasma etching parameters for composite pretreated micaceous iron powder: power 80W, time 8min, atmosphere air; mass ratio of aqueous silane coupling agent KH560 to nano silica 1:2; carboxymethyl chitosan concentration 1.5%, composite modification time 2h, temperature 35℃; micaceous iron powder of 325 mesh flakes was selected. The compound film-forming aid consists of polyethylene glycol monomethyl ether (MPEG-300), tributyl citrate, and propylene glycol butyl ether in a mass ratio of 1:0.8:0.5; the water-based dispersant is a polycarboxylate (BYK-P104); the organosilicon defoamer is polyether-modified organosilicon (BYK-028); the composite rust inhibitor consists of aluminum tripolyphosphate, zinc phosphate, and zinc molybdate in a mass ratio of 2:3:1; the functional modified filler consists of bentonite and diatomaceous earth modified with silane coupling agent (KH550) in a mass ratio of 1:1.2, with KH550 accounting for 2% of the total filler mass and having a particle size of 1000 mesh.

[0045] The preparation method includes the following steps: Step 1: Preparation of microwave-assisted core-shell crosslinking modified emulsion: Deionized water and compound emulsifier were added to a 500 mL reactor equipped with a microwave reactor, stirring device, thermometer, and dropping funnel. Stirring was started at 600 r / min for 15 min until the emulsifier was completely dissolved. The temperature was slowly raised to 70℃, and 30% of the core layer monomer and 40% of the initiator solution (potassium persulfate dissolved in deionized water, concentration 8%) were added. The microwave power was adjusted to 180 W, and the reaction was maintained at this temperature for 0.8 h to obtain a homogeneous seed emulsion. Subsequently, the remaining core layer monomer and 30% of the initiator solution were added dropwise at a rate of 0.8 mL / min. After the addition was complete, the temperature was raised... The temperature was raised to 80℃ and maintained for 0.5 h to ensure sufficient core-layer polymerization. Then, all shell monomers, urea-formaldehyde resin crosslinking agent, and the remaining 30% of initiator solution were added dropwise at a rate of 0.8 mL / min. The microwave power was adjusted to 150 W, and the temperature was raised to 85℃ and maintained for 1.0 h. During this period, the stirring speed was increased to 750 r / min every 20 min for 5 min to ensure uniform crosslinking. After the reaction was completed, the temperature was lowered to 45℃, and the pH was adjusted to 7.0 with diethanolamine. The mixture was filtered through a 200-mesh filter to obtain a transparent and uniform modified emulsion for later use. The solid content of the emulsion was 45%, and the viscosity was 220 mPa·s (25℃).

[0046] Step 2, Preparation of composite pretreated micaceous iron oxide powder: 325-mesh flaky micaceous iron oxide powder was placed in a plasma treatment instrument, with a power of 80W, a time of 8min, and an air atmosphere for surface etching. After removal, it was cooled to room temperature. A mixed modification solution (KH560, nano-silica, and carboxymethyl chitosan solution) was prepared. The cooled micaceous iron oxide powder was added to the mixed modification solution, and the temperature was adjusted to 35℃. The mixture was stirred at a constant temperature for 2h. During this period, the stirring speed was increased from 800r / min to 1000r / min every 30min for 5min, and then returned to 800r / min. After modification, the micaceous iron oxide powder was removed by vacuum filtration, placed in an 85℃ oven for drying for 2h, pulverized after drying, and passed through a 1000-mesh sieve to obtain pretreated micaceous iron oxide powder for later use. Its water contact angle was measured to be 68°, indicating a significant improvement in hydrophilicity and dispersibility.

[0047] Step 3, Preparation of intermediate paint base material: Add the modified emulsion prepared in Step 1 to a 1000mL dispersion vessel equipped with an ultrasonic and mechanical stirring device. Turn on the ultrasonic and stirring, with an ultrasonic power of 150W and a stirring speed of 600r / min. Under low-speed stirring, add the water-based dispersant, organosilicon defoamer, compound film-forming aid, and composite rust inhibitor in sequence. After each component is added, continue ultrasonic stirring for 15min to ensure full dissolution and mixing. After all components are added, adjust the temperature to 42℃ and keep stirring at this temperature for 0.4h to obtain a uniform and transparent base material for later use. The viscosity of the base material is measured to be 290mPa·s (25℃).

[0048] Step 4, Mixing and Grinding: Slowly add pretreated micaceous iron powder and functional modified filler to the base material, adjust the ultrasonic power to 220W, the stirring speed to 1400r / min, and perform ultrasonic-mechanical synergistic dispersion for 1.0h. During this period, stop the machine every 30min and use a scraper fineness gauge to check the dispersion effect to ensure that there are no agglomerated particles. Then, send the material into a horizontal sand mill, grind at 1900r / min, grind for 0.9h, and take samples every 30min to check the fineness until the fineness is 36μm (≤38μm), then stop grinding and set aside for later use.

[0049] Step 5, Finished Product Preparation: The ground material is fed into a dispersion vessel, the remaining deionized water is added, the ultrasonic power is adjusted to 150W, the stirring speed is 600r / min, and the mixture is stirred at low speed for 15min. The viscosity is tested with a Forte 4 cup (25℃) and adjusted to 19s, which meets the construction requirements. The mixture is then filtered through a 200-mesh filter to remove impurities, resulting in a uniform, fine, bubble-free, low-VOC waterborne acrylic modified micaceous iron oxide intermediate paint. The paint is then packaged into a sealed plastic bucket and stored in a cool, dry place.

[0050] Performance testing: VOC content 42g / L, adhesion grade 1, salt spray resistance 1100h (no bubbling, no rust), water resistance 260h (no abnormalities), fineness 36μm, viscosity 19s, good storage stability (no delamination at 50℃ for 7 days), all performances meet industry standards, environmentally friendly and convenient, suitable for corrosion protection of ordinary steel structures.

[0051] Example 3: This embodiment provides a low-VOC waterborne acrylic modified micaceous iron oxide intermediate paint and its preparation method. By mass, the intermediate paint is composed of the following components: 58 parts of microwave-assisted core-shell crosslinking modified waterborne acrylic emulsion, 32 parts of plasma-coupling agent-nanoparticle composite pretreated micaceous iron oxide powder, 4.5 parts of compounded low-VOC film-forming aid, 1.6 parts of waterborne dispersant, 0.9 parts of organosilicon defoamer, 3.2 parts of composite rust inhibitor, 10.5 parts of functional modified filler, and 14.5 parts of deionized water.

[0052] The microwave-assisted core-shell crosslinking modified emulsion comprises a core monomer of methyl methacrylate and butyl acrylate in a mass ratio of 0.8:1; a shell monomer of hydroxyethyl acrylate, γ-methacryloyloxypropyltrimethoxysilane, and maleic anhydride in a mass ratio of 6:2:2; a core-to-shell monomer mass ratio of 1:0.8; maleic anhydride accounting for 15% of the total mass of the shell monomers; an amino resin crosslinking agent (melamine-formaldehyde resin) accounting for 7% of the total mass of the core-shell monomers; a compound emulsifier of fatty alcohol polyoxyethylene ether (AEO-10) and alkyl glycoside (APG-1618) in a mass ratio of 2:1.5, accounting for 3.2% of the total mass of the core-shell monomers; and an initiator of ammonium persulfate with a solution concentration of 12%, accounting for 1.2% of the total mass of the core-shell monomers.

[0053] Plasma etching parameters for composite pretreated micaceous iron powder: power 120W, time 15min, atmosphere air; mass ratio of waterborne silane coupling agent KH560 to nano silica 1:3; carboxymethyl chitosan concentration 3.0%, composite modification time 3h, temperature 55℃; micaceous iron powder of 325 mesh flakes was selected. The compound film-forming aid consists of polyethylene glycol monomethyl ether (MPEG-500), tributyl citrate, and propylene glycol butyl ether in a mass ratio of 1:1.2:1.0; the water-based dispersant is a polycarboxylate (BYK-P104); the organosilicon defoamer is polyether-modified organosilicon (BYK-028); the composite rust inhibitor consists of aluminum tripolyphosphate, zinc phosphate, and zinc molybdate in a mass ratio of 2:3:2; and the functional modified filler consists of bentonite and diatomaceous earth modified with silane coupling agent (KH550) in a mass ratio of 1:2.0, with KH550 accounting for 4% of the total filler mass and having a particle size of 1500 mesh.

[0054] The preparation method includes the following steps: Step 1: Preparation of microwave-assisted core-shell crosslinking modified emulsion: Deionized water and compound emulsifier were added to a 500 mL reactor equipped with a microwave reactor, stirring device, thermometer, and dropping funnel. Stirring was started at 700 r / min for 15 min until the emulsifier was completely dissolved. The temperature was slowly raised to 75℃, and 35% of the core layer monomer and 45% of the initiator solution (ammonium persulfate dissolved in deionized water, concentration 12%) were added. The microwave power was adjusted to 220 W, and the reaction was maintained at this temperature for 1.2 h to obtain a homogeneous seed emulsion. Subsequently, the remaining core layer monomer and 25% of the initiator solution were added dropwise at a rate of 1.1 mL / min. After the addition was complete, the temperature was raised to... The reaction was carried out at 85℃ for 1.0 h to ensure sufficient core-layer polymerization. Then, all shell monomers, melamine-formaldehyde resin crosslinking agent, and the remaining 30% of initiator solution were added dropwise at a rate of 1.1 mL / min. The microwave power was adjusted to 180 W, the temperature was raised to 90℃, and the reaction was carried out at this temperature for 1.5 h. During this period, the stirring speed was increased to 850 r / min every 20 min for 5 min to ensure uniform crosslinking. After the reaction was completed, the temperature was lowered to 55℃, the pH was adjusted to 7.8 with diethanolamine, and the mixture was filtered through a 200-mesh filter to obtain a transparent and uniform modified emulsion for later use. The solid content of the emulsion was 52%, and the viscosity was 280 mPa·s (25℃).

[0055] Step 2, Preparation of composite pretreated micaceous iron oxide powder: 325-mesh flaky micaceous iron oxide powder was placed in a plasma treatment instrument, with a power of 120W, a time of 15 minutes, and an air atmosphere for surface etching. After removal, it was cooled to room temperature. A mixed modification solution (KH560, nano-silica, and carboxymethyl chitosan solution) was prepared. The cooled micaceous iron oxide powder was added to the mixed modification solution, and the temperature was adjusted to 55℃. The mixture was stirred at a constant temperature for 3 hours. During this period, the stirring speed was increased from 1200 r / min to 1400 r / min every 30 minutes for 10 minutes, and then returned to 1200 r / min. After modification, the micaceous iron oxide powder was removed by vacuum filtration, placed in a 95℃ oven for drying for 3 hours, pulverized after drying, and passed through a 1000-mesh sieve to obtain pretreated micaceous iron oxide powder for later use. Its water contact angle was measured to be 61°, indicating excellent hydrophilicity and dispersibility.

[0056] Step 3, Preparation of intermediate paint base material: Add the modified emulsion prepared in Step 1 to a 1000mL dispersion vessel equipped with an ultrasonic and mechanical stirring device. Turn on the ultrasonic and stirring, with an ultrasonic power of 200W and a stirring speed of 850r / min. Under low-speed stirring, add the water-based dispersant, organosilicon defoamer, compound film-forming aid, and composite rust inhibitor in sequence. After each component is added, continue ultrasonic stirring for 20min to ensure full dissolution and mixing. After all components are added, adjust the temperature to 52℃ and keep stirring at this temperature for 0.9h to obtain a uniform and transparent base material for later use. The viscosity of the base material is measured to be 350mPa·s (25℃).

[0057] Step 4, Mixing and Grinding: Slowly add pretreated micaceous iron powder and functional modified filler to the base material, adjust the ultrasonic power to 280W, the stirring speed to 1900r / min, and perform ultrasonic-mechanical synergistic dispersion for 1.4h, stopping the machine every 30min during this period and using a scraper fineness gauge to check the dispersion effect to ensure that there are no agglomerated particles; then send the material into a horizontal sand mill, grind at 2400r / min for 1.8h, taking samples every 30min to check the fineness until the fineness reaches 30μm (≤38μm), then stop grinding and set aside for later use.

[0058] Step 5, Finished Product Preparation: The ground material is fed into a dispersion vessel, the remaining deionized water is added, the ultrasonic power is adjusted to 200W, the stirring speed is 850r / min, and the mixture is stirred at low speed for 20min. The viscosity is tested with a Forte 4 cup (25℃) and adjusted to 29s, which meets the construction requirements. The mixture is then filtered through a 200-mesh filter to remove impurities, resulting in a uniform, fine, bubble-free, low-VOC waterborne acrylic modified micaceous iron oxide intermediate paint. The paint is then packaged into a sealed plastic bucket and stored in a cool, dry place.

[0059] Performance testing: VOC content 44g / L, adhesion grade 0, salt spray resistance 1300h (no bubbling, no rust), water resistance 290h (no abnormalities), fineness 30μm, viscosity 29s, good storage stability (no delamination at 50℃ for 7 days), optimal performance in all aspects, suitable for corrosion protection of metal components in highly corrosive environments.

[0060] Compare with Example 1 (existing conventional water-based micaceous iron oxide intermediate paint) This comparative example provides a conventional water-based micaceous iron oxide intermediate paint, comprising, by weight, 48 parts of ordinary water-based acrylic emulsion, 26 parts of untreated micaceous iron oxide powder, 6 parts of traditional film-forming aid (ethylene glycol butyl ether), 1.1 parts of dispersant, 0.6 parts of defoamer, 2.1 parts of rust inhibitor, 7.8 parts of ordinary filler, and 11.2 parts of deionized water. The preparation method is conventional mechanical stirring dispersion and water bath heating polymerization, without modification treatment; the rest is the same as in Example 1.

[0061] Performance testing: VOC content 125g / L, adhesion level 2, salt spray resistance 500h (bubbling, rusting), water resistance 120h (bubbling, discoloration), fineness 48μm, viscosity 24s. All performance characteristics are far inferior to those of this invention, and environmental protection and anti-corrosion performance do not meet the standards.

[0062] Comparative Example 2 (single emulsion modification plus single micaceous iron powder modification) The components of this comparative example are the same as those of Example 1, but the emulsion is modified only by core-shell polymerization (without microwave assistance and crosslinking), and the micaceous iron powder is modified only by a single silane coupling agent (without plasma, nanoparticles and bio-based materials). The preparation process does not include ultrasonic synergistic dispersion.

[0063] Performance testing: VOC content 68g / L, adhesion grade 1-2, salt spray resistance 750h (slight bubbling), water resistance 180h (slight discoloration), fineness 42μm, viscosity 24s. The performance is better than existing conventional products, but far inferior to the present invention, indicating that the synergistic advantages of the present invention integrating multiple creative technologies are significant.

[0064] Comparative Example 3 (without crosslinking modification and without bio-based film-forming aids) The components of this comparative example are the same as those of Example 1, but the emulsion is not crosslinked with maleic anhydride and amino resin, and the only film-forming aid used is propylene glycol butyl ether (without bio-based components). The rest are the same as in Example 1.

[0065] Performance testing: VOC content 55g / L, adhesion grade 1, salt spray resistance 850h (slight bubbling), water resistance 200h (slight discoloration), fineness 35μm, viscosity 24s. The performance is better than control example 2, but still worse than the present invention, indicating that the integration of crosslinking modification and bio-based film-forming aid is crucial for performance improvement.

[0066] As can be seen from the comparison between the examples and the control examples, the present invention effectively solves the technical defects of existing water-based micaceous iron oxide intermediate paints, achieves simultaneous reduction of VOC depth and improvement of comprehensive performance, has stable product performance, and the preparation process is suitable for industrial promotion.

[0067] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A low-VOC waterborne acrylic-modified micaceous iron oxide intermediate paint, characterized in that, The product comprises the following components by weight: 42-58 parts of microwave-assisted core-shell crosslinking modified waterborne acrylic emulsion, 22-32 parts of plasma-coupling agent-nanoparticle composite pretreated micaceous iron powder, 1.8-4.5 parts of compounded low-VOC film-forming aid, 0.6-1.6 parts of waterborne dispersant, 0.4-0.9 parts of organosilicon defoamer, 1.2-3.2 parts of composite rust inhibitor, 4.8-10.5 parts of functional modified filler, and 7.5-14.5 parts of deionized water; The emulsion is prepared using a microwave-assisted segmented heating core-shell polymerization process. The core monomer is a mixture of methyl methacrylate and butyl acrylate, and the shell monomer is a mixture of hydroxyethyl acrylate, γ-methacryloyloxypropyltrimethoxysilane, and maleic anhydride. An amino resin crosslinking agent is added, and the microwave power and segmented temperature are controlled during the polymerization process. The composite pretreated micaceous iron powder is first etched by plasma surface etching, and then modified by water-based silane coupling agent, nano-silica and carboxymethyl chitosan. The compounded low-VOC film-forming aid is a compound system of polyethylene glycol monomethyl ether, tributyl citrate and propylene glycol butyl ether, with a VOC content ≤45g / L; The functional modified filler is a compound of bentonite and diatomaceous earth modified with silane coupling agent.

2. The low-VOC waterborne acrylic-modified micaceous iron oxide intermediate paint according to claim 1, characterized in that: The mass ratio of the core layer to the shell layer monomers is 1:(0.6-0.8), the amount of maleic anhydride is 8-15% of the total mass of the shell layer monomers, and the amount of amino resin crosslinking agent is 3-7% of the total mass of the core and shell monomers.

3. The low-VOC waterborne acrylic-modified micaceous iron oxide intermediate paint according to claim 1, characterized in that: The plasma etching parameters are as follows: power 80-120W, time 8-15min, atmosphere is air; waterborne silane coupling agent is KH560, the mass ratio of nano-silica to KH560 is 1:(2-3), carboxymethyl chitosan concentration is 1.5-3.0%, and composite modification time is 2-3h.

4. The low-VOC waterborne acrylic-modified micaceous iron oxide intermediate paint according to claim 1, characterized in that: In the compounded film-forming aid, the mass ratio of polyethylene glycol monomethyl ether, tributyl citrate and propylene glycol butyl ether is 1:(0.8-1.2):(0.5-1.0), and the boiling point is ≥220℃.

5. The low-VOC waterborne acrylic-modified micaceous iron oxide intermediate paint according to claim 1, characterized in that: The composite rust inhibitor is a compound of aluminum tripolyphosphate, zinc phosphate and zinc molybdate in a mass ratio of 2:3:(1-2); the water-based dispersant is a polycarboxylate.

6. The low-VOC waterborne acrylic-modified micaceous iron oxide intermediate paint according to claim 1, characterized in that: In the functional modified filler, the mass ratio of bentonite to diatomite is 1:(1.2-2.0), and the amount of silane coupling agent is 2-4% of the total mass of the filler.

7. A method for preparing a low-VOC waterborne acrylic-modified micaceous iron oxide intermediate varnish as described in any one of claims 1-6, characterized in that, Includes the following steps: Step 1, Preparation of microwave-assisted core-shell crosslinking modified emulsion: Add deionized water and compound emulsifier to a reactor equipped with a microwave reactor, dissolve, and heat to 70-75℃. Add part of the core layer monomer and initiator, microwave power 180-220W, and maintain the temperature for 0.8-1.2h. Add the remaining core layer monomer dropwise, heat to 80-85℃, and maintain the temperature for 0.5-1h. Add the shell layer monomer and amino resin dropwise, microwave power 150-180W, heat to 85-90℃, and maintain the temperature for 1.0-1.5h. Cool down and adjust the pH to 7.0-7.8, then filter and discharge. Step 2, Preparation of composite pretreated micaceous iron powder: After plasma etching, micaceous iron powder is mixed with coupling agent, nano-silica and carboxymethyl chitosan solution, modified at 35-55℃ for 2-3 hours, dried, pulverized and sieved. Step 3, Preparation of base material: Add emulsion to dispersion vessel, turn on ultrasonic-mechanical synergistic dispersion, add dispersant, defoamer, film-forming aid and rust inhibitor, keep warm and stir for 0.4-0.9h; Step 4, Mixing and Grinding: Add pretreated micaceous iron powder and functional fillers, disperse synergistically for 1.0-1.4 hours, and grind in a sand mill until the fineness is ≤38μm; Step 5, Finished product preparation: Add the remaining deionized water, adjust the viscosity to 19-29s, and filter to obtain the finished product.

8. The preparation method according to claim 7, characterized in that: In step 1, the compound emulsifier is a compound of fatty alcohol polyoxyethylene ether and alkyl glycoside in a mass ratio of 2:(1-1.5), and the amount used is 2.2-3.2% of the total mass of the core-shell monomers; the initiator is ammonium persulfate or potassium persulfate, and the amount used is 0.7-1.2% of the total mass of the monomers.

9. The preparation method according to claim 7, characterized in that: In step 3, the ultrasonic power is 150-200W, the stirring speed is 600-850r / min, and the heat preservation temperature is 42-52℃.

10. The preparation method according to claim 7, characterized in that: In step 4, the ultrasonic power is 220-280W, the stirring speed is 1400-1900r / min, the sand mill speed is 1900-2400r / min, and the grinding time is 0.9-1.8h.

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