Acrylic acid composite emulsion coating and preparation method thereof

Abstract

The invention relates to the technical field of acrylic acid emulsion coating preparation, and discloses an acrylic acid composite emulsion coating and a preparation method thereof.The acrylic acid composite emulsion coating is prepared from a first finish paint component and a second finish paint component according to the mass ratio of (5-10): 1; the first finish paint component is prepared from the following components in percentage by mass: 30 to 50 percent of acrylic acid composite emulsion, and the acrylic acid composite emulsion is prepared from the following components in percentage by mass: 10 to 20 percent of acrylic acid monomer, 20 to 40 percent of butyl acrylate, 3 to 5 percent of aldehyde ketone resin, 4 to 6 percent of waterborne polyisocyanate, 0.5 to 1.5 percent of emulsifier, 0.05 to 0.15 percent of initiator and 0.2 to 0.4 percent of buffering agent; and the balance of deionized water. The acrylic acid composite emulsion coating provided by the invention has the following advantages: rapid drying can be realized at normal temperature, the construction period is shortened, and the construction efficiency is improved; the initial hardness after construction can be quickly established, and the requirement of quick use is met; the acrylic acid composite emulsion coating has excellent weather resistance in an outdoor environment, and the performance of a coating film can be kept for a long time.

Description

Technical Field

[0001] The invention belongs to the technical field of acrylic emulsion coatings, and particularly relates to an acrylic composite emulsion coating and a preparation method thereof. Background Art

[0002] Acrylic emulsion is a milky white or nearly transparent viscous liquid, which is widely used in a variety of coating formulations, especially in high-gloss and semi-gloss coatings. The resulting coatings have good water resistance, weather resistance, alkali resistance and stain resistance. However, in coating applications, acrylic emulsion also has certain disadvantages. Its environmental adaptability is relatively poor. Under low temperature conditions, acrylic emulsion may become brittle, affecting the mechanical properties of the coating; under high temperature conditions, it may become too viscous, affecting the construction performance of the coating. In addition, there are certain shortcomings in the drying speed, especially in low temperature or high humidity environments, which will lead to delays in construction progress.

[0003] Therefore, the prior art still needs to be improved and developed. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide an acrylic composite emulsion coating and a preparation method thereof, aiming to solve the problems that the existing acrylic emulsion coatings dry slowly in a high humidity environment, which seriously affects the construction efficiency and construction period. In addition, the initial hardness of the coating after construction is slow to build up, which limits the timely implementation of subsequent processes; in outdoor applications, the insufficient weather resistance and water resistance of the coating will lead to a decrease in coating film performance and affect the service life of the product.

[0005] The technical solution of the present invention is as follows:

[0006] An acrylic composite emulsion coating, wherein the acrylic composite emulsion coating comprises a first topcoat component and a second topcoat component in a mass ratio of 5-10:1; the first topcoat component comprises, by mass percentage, 30-50% of an acrylic composite emulsion, 8-12% of titanium dioxide, 10-15% of precipitated barium sulfate, and 12-16% of silicon micropowder or nano silicon dioxide; the second topcoat component comprises, by mass percentage, 15-25% of a polyester polyol compound, 1 0-30% of diisocyanate compounds, 5-15% of organosiloxane compounds, and 20-55% of organic solvents; wherein the acrylic composite emulsion comprises, by mass percentage, 10-20% of acrylic monomers, 20-40% of butyl acrylate, 3-5% of aldehyde-ketone resins, 4-6% of aqueous polyisocyanates, 0.5-1.5% of emulsifiers, 0.05-0.15% of initiators, 0.2-0.4% of buffers, and the balance is deionized water.

[0007] The acrylic composite emulsion coating, wherein in the acrylic composite emulsion, the emulsifier is sodium dodecyl sulfate or aromatic alcohol polyoxyethylene ether; the buffer is one or both of sodium bicarbonate and sodium tripolyphosphate; and the initiator is potassium persulfate.

[0008] The acrylic composite emulsion coating, wherein the first topcoat component further comprises, by mass percentage: 0.1-0.5% of an amine neutralizer, 0.2-0.8% of a substrate wetting agent, 0.1-0.5% of a defoamer, 0.2-0.8% of a leveling agent, 0.2-0.8% of a rheological additive, and the balance of deionized water.

[0009] The acrylic composite emulsion coating, wherein the amine neutralizer is dimethylethanolamine; the substrate wetting agent is polyoxyethylene alkylphenol ether; the defoamer is polydimethylsiloxane; the leveling agent is a polyacrylate compound; and the rheological additive is hydroxyethyl cellulose.

[0010] The acrylic composite emulsion coating, wherein the second topcoat component further comprises, by mass percentage, 0.02-0.5% of a curing catalyst and 0.5-1.5% of a neutralizer.

[0011] The acrylic composite emulsion coating, wherein in the second topcoat component, the polyester polyol compound is polytetramethylene furan ether; the diisocyanate compound is isophorone diisocyanate; the organosiloxane compound is α,ω-diaminopropyl polydimethylsiloxane; the curing catalyst is dibutyltin dilaurate; the neutralizer is triethylamine; and the organic solvent is dimethyl carbonate or diethylene glycol carbonate.

[0012] A method for preparing the acrylic composite emulsion coating according to the present invention, comprising the steps of:

[0013] First add acrylic composite emulsion into the dispersion tank, then add deionized water and amine neutralizer, and adjust to the appropriate pH value;

[0014] Continue to add titanium dioxide, precipitated barium sulfate, silicon powder, substrate wetting agent, defoamer, leveling agent, and rheological additive into the dispersion tank under stirring to obtain a first mixed solution;

[0015] Adding deionized water or a rheological additive to the first mixed solution to adjust the viscosity and rheological properties to obtain a first topcoat component;

[0016] In a stirring tank, a polyester polyol compound and a diisocyanate compound are mixed to obtain a second mixed solution;

[0017] Under stirring conditions, adding an organic siloxane compound, a curing catalyst, and a neutralizer to the second mixed liquid, and adjusting the viscosity with an organic solvent to obtain a second topcoat component;

[0018] The first topcoat component and the second topcoat component are mixed in a mass ratio of 5-10:1, the second topcoat component is slowly added into the first topcoat component, and after stirring evenly, the acrylic composite emulsion coating is obtained.

[0019] The preparation method of the acrylic composite emulsion coating, wherein the preparation of the acrylic composite emulsion comprises the steps of:

[0020] Evenly mixing acrylic acid monomer and butyl acrylate to obtain an acrylic acid mixed solution;

[0021] In a pre-emulsification tank, 8-10% of the total amount of the acrylic acid mixture is mixed with the aldehyde-ketone resin, and 20-30% of the total amount of the emulsifier is added for pre-emulsification to obtain a pre-emulsified liquid;

[0022] Adding an appropriate amount of initiator of 5-10% of the total amount to the pre-emulsion, and controlling the temperature to 60-85° C. for preliminary polymerization to form a seed emulsion;

[0023] In the reactor, add the remaining emulsifier, buffer and deionized water, stir evenly and control the temperature to 70-80° C., then gradually add the seed emulsion and maintain stable conditions in the reactor;

[0024] The remaining acrylic acid mixture and the remaining initiator solution are mixed evenly and then gradually added dropwise to the reactor to ensure that the polymerization reaction proceeds evenly. After the addition is completed, an aqueous polyisocyanate is added to promote the crosslinking of the emulsion to obtain an initial composite emulsion;

[0025] The temperature in the reactor is raised to 85-100°C, the initial composite emulsion is aged, then the temperature is lowered to 50-60°C, a buffer is added to adjust the pH, and after keeping the temperature for a predetermined time, the initial composite emulsion is cooled to room temperature, and finally filtered to remove particulate impurities to obtain the acrylic composite emulsion.

[0026] Beneficial effects: Compared with traditional acrylic emulsion coatings, the acrylic composite emulsion coating provided by the present application has the following advantages: it can achieve rapid drying at room temperature, shorten the construction period, and improve construction efficiency; it can quickly establish the initial hardness after construction, meeting the demand for rapid commissioning; the acrylic composite emulsion coating has excellent weather resistance in outdoor environments and can maintain the performance of the coating film for a long time. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The present invention is a flow chart of a method for preparing an acrylic composite emulsion coating. DETAILED DESCRIPTION

[0028] The present invention provides an acrylic composite emulsion coating and a preparation method thereof. To make the purpose, technical scheme and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0029] The terms "first", "second", "third", "fourth", etc. (if any) in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "including" or "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0030] The embodiment of the present invention provides an acrylic composite emulsion coating, which includes a first topcoat component and a second topcoat component in a mass ratio of 5-10:1; the first topcoat component includes, by mass percentage, 30-50% of an acrylic composite emulsion, 8-12% of titanium dioxide, 10-15% of precipitated barium sulfate, and 12-16% of silicon micropowder or nano silicon dioxide; the second topcoat component includes, by mass percentage, 15-25% of a polyester polyol compound, 10- 30% of diisocyanate compounds, 5-15% of organosiloxane compounds, and 20-55% of organic solvents; wherein the acrylic composite emulsion comprises, by mass percentage, 10-20% of acrylic monomers, 20-40% of butyl acrylate, 3-5% of aldehyde-ketone resins, 4-6% of aqueous polyisocyanates, 0.5-1.5% of emulsifiers, 0.05-0.15% of initiators, 0.2-0.4% of buffers, and the balance is deionized water.

[0031] In this embodiment, the acrylic composite emulsion contains only two kinds of acrylic acid, namely acrylic acid monomer and butyl acrylate, which helps to control the molecular weight and distribution of the polymer and obtain more consistent product performance, wherein 10%-20% of the acrylic acid monomer serves as a monomer for the polymerization reaction and is the basic unit for forming the polymer chain; 20%-40% of butyl acrylate serves as a co-monomer and can increase the flexibility and adhesion of the emulsion.

[0032] In this embodiment, 3%-5% of aldehyde-ketone resin is mainly used to improve the gloss, hardness, anti-degradation and weather resistance of the coating. Too high an amount of aldehyde-ketone resin added will cause the coating film to become brittle and reduce flexibility, thereby affecting the overall performance of the coating film; too low an aldehyde-ketone resin will reduce the hardness and weather resistance of the coating.

[0033] In this embodiment, the emulsifier is sodium dodecyl sulfate (SDS) or fatty alcohol polyoxyethylene ether (AEO-9), which is mainly used to improve the stability of the emulsion; the initiator is potassium persulfate (KPS), which is mainly used to initiate polymerization and hardening; the buffer is one or both of sodium bicarbonate and sodium tripolyphosphate, which is mainly used to maintain the pH value and improve the stability of the emulsion.

[0034] In this embodiment, the water-based polyisocyanate mainly acts as a cross-linking agent, which can combine with the hydroxyl groups of the aldehyde-ketone resin in the emulsion to form a network structure, thereby providing sealing properties for the final product, thereby enhancing the stability, mechanical strength and chemical resistance of the emulsion.

[0035] In the first topcoat component of this embodiment, the acrylic composite emulsion is used as its base resin to provide the basic properties of the coating; the titanium dioxide mainly provides good hiding power and whiteness for the coating; the precipitated barium sulfate is mainly used to increase the density and wear resistance of the coating; the silicon micropowder or nano silicon dioxide is mainly used to improve the hardness and weather resistance of the coating. In this embodiment, the first topcoat component also includes, by mass percentage: 0.1-0.5% of amine neutralizer, 0.2-0.8% of substrate wetting agent, 0.1-0.5% of defoamer, 0.2-0.8% of leveling agent, 0.2-0.8% of rheological additive, and the balance of deionized water. The amine neutralizer is mainly used to adjust the pH value to ensure the stability and construction performance of the coating system. For example, the amine neutralizer is preferably dimethylethanolamine (DMEA), but not limited to this; the substrate wetting agent is mainly used to improve the wettability of the coating to the substrate and improve the adhesion. For example, the substrate wetting agent is preferably polyoxyethylene alkylphenol ether, but not limited to this; the defoamer is mainly used to reduce the bubbles generated during the production and construction of the coating. For example, the defoamer is polydimethylsiloxane, but not limited to this; the leveling agent is mainly used to improve the leveling of the coating film and reduce brush marks and orange peel phenomena. For example, the leveling agent is a polyacrylate compound, but not limited to this; the rheological additive is mainly used to adjust the rheological properties of the coating. For example, the rheological additive is preferably hydroxyethyl cellulose, but not limited to this; the deionized water is used as a solvent, mainly used to adjust the viscosity and solid content of the coating.

[0036] In the second topcoat component of this embodiment, the polyester polyol compound is used as the main soft segment raw material to provide the flexibility and adhesion of the coating film. For example, the polyester polyol compound is preferably polytetramethylene ether, but not limited to this; the diisocyanate compound is used as one of the hard segment raw materials to provide the strength and wear resistance of the coating film. For example, the diisocyanate compound is preferably isophorone diisocyanate, but not limited to this; the organosiloxane compound is used for modification to improve the weather resistance and water resistance of the coating film. For example, the organosiloxane compound is preferably α, ω-diaminopropyl polydimethylsiloxane, but not limited to this; the organic solvent is used to adjust the viscosity and dissolve the resin to improve the construction performance of the coating. For example, the organic solvent is preferably dimethyl carbonate DMC or diethylene glycol carbonate DEC, but not limited to this. In this embodiment, the second topcoat component also includes: 0.02-0.5% of a curing catalyst and 0.5-1.5% of a neutralizer by mass percentage. The curing catalyst is mainly used to promote the curing reaction of the coating. As an example, the curing catalyst is preferably dibutyltin dilaurate, but is not limited thereto. The neutralizer is used to neutralize the hydrochloric acid generated during the reaction and adjust the pH value of the coating. As an example, the neutralizer is preferably triethylamine.

[0037] The acrylic composite emulsion coating provided in this embodiment has the following advantages: it can achieve rapid drying at room temperature, shortening the construction period and improving construction efficiency; it can quickly establish the initial hardness after construction, meeting the demand for rapid commissioning; the acrylic composite emulsion coating has excellent weather resistance in outdoor environments and can maintain the performance of the coating film for a long time.

[0038] In some embodiments, a method for preparing an acrylic composite emulsion coating is also provided, such as Figure 1 As shown, it includes the steps of:

[0039] S10, first add acrylic composite emulsion into the dispersion tank, then add deionized water and amine neutralizer, and adjust to an appropriate pH value;

[0040] S20. Continue to add titanium dioxide, precipitated barium sulfate, silicon powder, substrate wetting agent, defoamer, leveling agent, and rheological additive into the dispersion tank under stirring to obtain a first mixed solution.

[0041] S30, adding deionized water or a rheological additive to the first mixed solution to adjust the viscosity and rheological properties to obtain a first topcoat component;

[0042] S40, in a stirring tank, mixing the polyester polyol compound and the diisocyanate compound to obtain a second mixed solution;

[0043] S50, adding an organic siloxane compound, a curing catalyst, and a neutralizer to the second mixed liquid under stirring, and adjusting the viscosity with an organic solvent to obtain a second topcoat component;

[0044] S60, mixing the first topcoat component and the second topcoat component in a mass ratio of 5-10:1, slowly adding the second topcoat component into the first topcoat component, stirring evenly, to obtain the acrylic composite emulsion coating.

[0045] In this embodiment, the first topcoat component and the second topcoat component are stored in different containers before use. When they are needed, the first topcoat component and the second topcoat component are mixed in a mass ratio of 5-10:1, and the second topcoat component is slowly added to the first topcoat component; according to the construction requirements and the viscosity of the paint, 20%-30% of the total amount of deionized water is added for dilution, and the dilution process should be continuously stirred until the paint reaches a suitable construction viscosity; the mixed and diluted paint should be left for 20 to 30 minutes for maturation to promote the reaction between the components and help eliminate bubbles in the paint; before construction, check whether the viscosity and rheology of the paint meet the construction requirements. If necessary, fine-tune the amount of deionized water added or use a rheological additive for adjustment; finally, spray construction is carried out on the primer that has been applied and dried.

[0046] Traditional acrylic emulsion paints dry slowly in high humidity environments, while the modified paint of the present invention can achieve rapid drying at room temperature, shortening the construction period and improving construction efficiency; traditional paints take a long time to build up their initial hardness after construction, while the modified paint provided by the present invention can quickly build up its initial hardness, meeting the need for rapid commissioning; in outdoor applications, the insufficient weather resistance of traditional paints can lead to a decrease in coating film performance and affect the service life of the product, while the modified paint provided by the present invention has excellent weather resistance in outdoor environments and can maintain the performance of the coating film for a long time; the water-based paint provided by the present invention is more environmentally friendly than solvent-based paints, reduces pollution to the environment, and meets the current demand for green products; the modified paint provided by the present invention also has good construction adaptability, can obtain a uniform coating film on different environments and substrates, and improves the flexibility and convenience of construction.

[0047] In some embodiments, the preparation of the acrylic composite emulsion includes the following steps: uniformly mixing acrylic monomer and butyl acrylate to obtain an acrylic mixed solution; in a pre-emulsification tank, mixing 8-10% of the total amount of the acrylic mixed solution with an aldehyde-ketone resin, and adding 20-30% of the total amount of an emulsifier for pre-emulsification to obtain a pre-emulsified solution; adding an appropriate amount of 5-10% of the total amount of an initiator to the pre-emulsified solution, and controlling the temperature to 60-85° C. for preliminary polymerization to form a seed emulsion; in a reactor, adding the remaining emulsifier, a buffer and deionized water, stirring uniformly and controlling the temperature to 70-80° C., and then The seed emulsion is gradually added, and the stable conditions in the reactor are maintained; the remaining acrylic acid mixed solution and the remaining initiator solution are evenly mixed and gradually dripped into the reactor to ensure that the polymerization reaction is evenly carried out, and after the dripping is completed, an aqueous polyisocyanate is added to promote the cross-linking of the emulsion to obtain an initial composite emulsion; the temperature in the reactor is raised to 85-100° C., the initial composite emulsion is subjected to a aging treatment, and then the temperature is lowered to 50-60° C., and a buffer is added to adjust the pH, and after the initial composite emulsion is kept warm for a predetermined time, the initial composite emulsion is cooled to room temperature, and finally the particulate impurities are removed by filtering to obtain the acrylic composite emulsion.

[0048] In this embodiment, the mass proportion of the seed emulsion is usually controlled at 5%-10% of the total emulsion mass, and the mass ratio and stability of the seed emulsion are crucial to the performance of the final product. Because the use of seed emulsion helps to control the polymerization reaction, improve the stability of the emulsion and the coating performance, the lack of seed emulsion may lead to uneven distribution of emulsion particle size and reduced coating performance.

[0049] The present invention will be further explained below by means of specific embodiments:

[0050] Example 1

[0051] An acrylic composite emulsion comprises, by mass percentage, 15% of acrylic monomer, 30% of butyl acrylate, 3% of aldehyde-ketone resin, 5% of aqueous polyisocyanate, 1% of emulsifier (SDS), 0.1% of initiator (KPS), 0.3% of buffer (NaHCO3), and the balance is deionized water; the preparation steps of the acrylic composite emulsion include:

[0052] Raw material preparation: Calculate the weight of raw materials required based on the final preparation of 50 kg of emulsion, and mix acrylic acid monomer and butyl acrylate evenly to obtain an acrylic acid mixed solution;

[0053] In a pre-emulsification tank, 10% of the total amount of the acrylic acid mixture is mixed with the aldehyde-ketone resin, and 25% of the total amount of the emulsifier is added for pre-emulsification to obtain a pre-emulsified liquid, ensuring good stirring and temperature control during the pre-emulsification process, wherein the stirring is performed for 20 minutes and the temperature is controlled at 20°C;

[0054] Adding an appropriate amount of initiator (8%) to the pre-emulsion, and controlling the temperature to 70° C. to perform preliminary polymerization to form a seed emulsion;

[0055] In the reactor, add the remaining emulsifier, buffer and deionized water, stir evenly and control the temperature to 80°C, then gradually add the seed emulsion and maintain the stable conditions in the reactor. The seed emulsion is added for 25 minutes;

[0056] The remaining acrylic acid mixture and the remaining initiator solution are mixed evenly and then gradually added dropwise to the reactor to ensure that the polymerization reaction proceeds evenly. The dropping time is 2 hours. After the dropping is completed, aqueous polyisocyanate is added to promote the crosslinking of the emulsion to obtain an initial composite emulsion;

[0057] The temperature in the reactor was raised to 85°C, and the initial composite emulsion was aged for 30 minutes. The temperature was then lowered to 55°C, and a buffer was added to adjust the pH to 8. After the initial composite emulsion was kept warm for a predetermined time, it was cooled to room temperature, and finally filtered to remove particulate impurities to obtain the acrylic composite emulsion.

[0058] Example 2

[0059] An acrylic composite emulsion comprises, by mass percentage, 20% of acrylic acid monomer, 25% of butyl acrylate, 4% of aldehyde-ketone resin, 5% of aqueous polyisocyanate, 1% of emulsifier (AEO-9), 0.1% of initiator (KPS), 0.3% of buffer (sodium tripolyphosphate), and the balance is deionized water; the preparation steps of the acrylic composite emulsion include:

[0060] Raw material preparation: Calculate the weight of raw materials required based on the final preparation of 50 kg of emulsion, and mix acrylic acid monomer and butyl acrylate evenly to obtain an acrylic acid mixed solution;

[0061] In a pre-emulsification tank, 8% of the total amount of the acrylic acid mixture is mixed with the aldehyde-ketone resin, and 30% of the total amount of the emulsifier is added for pre-emulsification to obtain a pre-emulsified liquid, ensuring good stirring and temperature control during the pre-emulsification process, wherein the stirring is performed for 15 minutes and the temperature is controlled at 18°C;

[0062] Adding an appropriate amount of initiator (8% of the total amount) to the pre-emulsion and controlling the temperature to 75° C. to perform preliminary polymerization to form a seed emulsion;

[0063] In the reactor, add the remaining emulsifier, buffer and deionized water, stir evenly and control the temperature to 80°C, then gradually add the seed emulsion and maintain the stable conditions in the reactor. The seed emulsion is added for 10 minutes;

[0064] The remaining acrylic acid mixture and the remaining initiator solution were mixed evenly and then gradually added dropwise to the reactor to ensure that the polymerization reaction proceeded evenly. The dropping time was 1.5 hours. After the dropping was completed, aqueous polyisocyanate was added to promote the crosslinking of the emulsion to obtain an initial composite emulsion;

[0065] The temperature in the reactor was raised to 85°C, and the initial composite emulsion was aged for 25 minutes. The temperature was then lowered to 55°C, and a buffer was added to adjust the pH to 7.5. After the initial composite emulsion was kept warm for a predetermined time, it was cooled to room temperature, and finally filtered to remove particulate impurities to obtain the acrylic composite emulsion.

[0066] Example 3

[0067] An acrylic composite emulsion comprises, by mass percentage, 10% of acrylic monomer, 40% of butyl acrylate, 5% of aldehyde-ketone resin, 5% of aqueous polyisocyanate, 1% of emulsifier (mixed SDS and AEO-9), 0.1% of initiator (KPS), 0.3% of buffer (mixed NaHCO3 and sodium tripolyphosphate), and the balance is deionized water; the preparation steps of the acrylic composite emulsion include:

[0068] Raw material preparation: Calculate the weight of raw materials required based on the final preparation of 50 kg of emulsion, and mix acrylic acid monomer and butyl acrylate evenly to obtain an acrylic acid mixed solution;

[0069] In a pre-emulsification tank, 8% of the total amount of the acrylic acid mixture is mixed with the aldehyde-ketone resin, and 30% of the total amount of the emulsifier is added for pre-emulsification to obtain a pre-emulsified liquid, ensuring good stirring and temperature control during the pre-emulsification process, wherein the stirring is performed for 15 minutes and the temperature is controlled at 18°C;

[0070] Adding an appropriate amount of initiator (8% of the total amount) to the pre-emulsion and controlling the temperature to 75° C. to perform preliminary polymerization to form a seed emulsion;

[0071] In the reactor, add the remaining emulsifier, buffer and deionized water, stir evenly and control the temperature to 80°C, then gradually add the seed emulsion and maintain the stable conditions in the reactor. The seed emulsion is added for 10 minutes;

[0072] The remaining acrylic acid mixture and the remaining initiator solution were mixed evenly and then gradually added dropwise to the reactor to ensure that the polymerization reaction proceeded evenly. The dropping time was 1.5 hours. After the dropping was completed, aqueous polyisocyanate was added to promote the crosslinking of the emulsion to obtain an initial composite emulsion;

[0073] The temperature in the reactor was raised to 85°C, and the initial composite emulsion was aged for 25 minutes. The temperature was then lowered to 55°C, and a buffer was added to adjust the pH to 7.5. After the initial composite emulsion was kept warm for a predetermined time, it was cooled to room temperature, and finally filtered to remove particulate impurities to obtain the acrylic composite emulsion.

[0074] Comparative Example 1

[0075] An acrylic composite emulsion, compared with Example 1, the difference is that the mass ratio of aldehyde-ketone resin is increased by 8%, the proportion of deionized water is correspondingly reduced, other raw material components and proportions remain unchanged, and the preparation process is the same as that of Example 1.

[0076] Comparative Example 2

[0077] An acrylic composite emulsion, whose raw material composition and proportion are consistent with those in Example 1, except that the preparation method is different. The preparation process in this comparative example 2 does not adopt the seed emulsion scheme, and directly performs polymerization reaction. Other process parameters are consistent with those in Example 1.

[0078] The following performance parameter experiments were conducted on the acrylic composite emulsion formulas prepared in Examples 1-3 and Comparative Examples 1-2:

[0079] Particle size: Use dynamic light scattering (DLS) or nanoparticle size analyzer to measure the size of particles in emulsions or dispersions. You can also observe the coating section under a microscope to measure the diameter of the particles;

[0080] Gel rate: after the polymerization reaction is completed, the emulsion is filtered through a filter, the gel portion on the filter is collected and dried to constant weight, and the gel rate is calculated according to the formula: Gel rate = (gel mass / total monomer mass) × 100%;

[0081] The coating film grinding time, after the coating film is dry, use standard grinding equipment or sandpaper to grind the coating film, and record the time required to completely remove the coating film. The applicant selects a glass plate, takes the same mass of the emulsions prepared in different embodiments / comparative examples, applies the same mass to the same area, and then stands for a period of time under the same environment, and then uses an electric grinding equipment to select sandpaper of the same mesh for grinding;

[0082] The coating appearance is visually inspected for uniformity, gloss, and defects such as pinholes or bubbles, and a score of 1-5 is set, with 5 indicating the best appearance (no defects, high gloss, and uniform color) and 1 indicating the worst appearance (obvious defects, low gloss, and uneven color).

[0083] The measured results are shown in Table 1:

[0084] Table 1 Emulsion performance parameters

[0085] Example / Comparative Example No. Particle size / nm Gel rate / % Coating polishing time / min Coating appearance Example 1 125 0.06 12 5 Example 2 105 0.12 15 4 Example 3 130 0.15 10 5 Comparative Example 1 160 1 8 4 Comparative Example 2 175 0.5 10 3

[0086] It can be seen from the data in Table 1 that the particle size and gel fraction of the acrylic composite emulsion prepared according to the embodiment of the present invention are smaller than those of the comparative example, and the coating polishing time is longer than that of the comparative example, indicating that the acrylic composite emulsion of this embodiment has a higher hardness after forming a coating, and the coating of this embodiment has a more uniform appearance, high gloss, and no defects such as pinholes or bubbles.

[0087] It can also be seen from the data in Table 1 that the amount of aldehyde-ketone resin added in Comparative Example 1 is too high: the amount of aldehyde-ketone resin added is 8%, which is higher than the range of 3%-5% in the embodiment. The excessive amount of aldehyde-ketone resin added causes the coating to become brittle and the flexibility to decrease, thereby affecting the overall performance of the coating. Comparative Example 2 does not adopt the seed emulsion solution, but directly conducts the polymerization reaction. The lack of seed emulsion in Comparative Example 2 leads to uneven distribution of emulsion particle size and decreased coating performance. The use of seed emulsion in this embodiment helps to control the polymerization reaction and improve the stability of the emulsion and coating performance.

[0088] Example 4

[0089] An acrylic composite emulsion coating comprises a first topcoat component and a second topcoat component in a mass ratio of 8:1, wherein the first topcoat component comprises, by mass percentage, 40% of the acrylic composite emulsion prepared in Example 1, 10% of titanium dioxide, 12% of precipitated barium sulfate, 15% of silicon micropowder, 0.3% of an amine neutralizer (DMEA), 0.5% of a substrate wetting agent, 0.3% of a defoamer, 0.5% of a leveling agent, 0.5% of a rheological aid (hydroxyethyl cellulose), and the balance of deionized water; the second topcoat component comprises, by mass percentage, 20% of a polyester polyol, 20% of a diisocyanate (IPDI), 10% of an organosiloxane, 0.1% of dibutyltin dilaurate, 1% of triethylamine, and the balance of an organic solvent (DMC); and the preparation method comprises the following steps:

[0090] First add acrylic composite emulsion into the dispersion tank, then add deionized water and amine neutralizer, and adjust to the appropriate pH value;

[0091] Titanium dioxide, precipitated barium sulfate, silicon micropowder, substrate wetting agent, defoamer, leveling agent and rheological additive are continuously added into the dispersion tank under stirring to obtain a first mixed solution.

[0092] Adding deionized water or a rheological additive to the first mixed solution to adjust the viscosity and rheological properties to obtain a first topcoat component;

[0093] In a stirring tank, a polyester polyol compound and a diisocyanate compound are mixed to obtain a second mixed solution;

[0094] Under stirring conditions, adding an organic siloxane compound, a curing catalyst, and a neutralizer to the second mixed liquid, and adjusting the viscosity with an organic solvent to obtain a second topcoat component;

[0095] The first topcoat component and the second topcoat component are mixed in a mass ratio of 8:1, the second topcoat component is slowly added into the first topcoat component, and after stirring evenly, the acrylic composite emulsion coating is obtained.

[0096] Example 5

[0097] An acrylic composite emulsion coating comprises a first topcoat component and a second topcoat component in a mass ratio of 5:1, wherein the first topcoat component comprises, by mass percentage, 45% of the acrylic composite emulsion prepared in Example 1, 10% of titanium dioxide, 13% of precipitated barium sulfate, 15% of silicon micropowder, 0.4% of an amine neutralizer (DMEA), 0.6% of a substrate wetting agent, 0.4% of a defoamer, 0.6% of a leveling agent, 0.6% of a rheological aid (hydroxyethyl cellulose), and the balance of deionized water; the second topcoat component comprises, by mass percentage, 18% of a polyester polyol, 25% of a diisocyanate (IPDI), 12% of an organosiloxane, 0.2% of dibutyltin dilaurate, 0.8% of triethylamine, and the balance of an organic solvent (DEC); and the preparation method comprises the following steps:

[0098] First add acrylic composite emulsion into the dispersion tank, then add deionized water and amine neutralizer, and adjust to the appropriate pH value;

[0099] Titanium dioxide, precipitated barium sulfate, silicon micropowder, substrate wetting agent, defoamer, leveling agent and rheological additive are continuously added into the dispersion tank under stirring to obtain a first mixed solution.

[0100] Adding deionized water or a rheological additive to the first mixed solution to adjust the viscosity and rheological properties to obtain a first topcoat component;

[0101] In a stirring tank, a polyester polyol compound and a diisocyanate compound are mixed to obtain a second mixed solution;

[0102] Under stirring conditions, adding an organic siloxane compound, a curing catalyst, and a neutralizer to the second mixed liquid, and adjusting the viscosity with an organic solvent to obtain a second topcoat component;

[0103] The first topcoat component and the second topcoat component are mixed in a mass ratio of 10:1, the second topcoat component is slowly added into the first topcoat component, and the mixture is stirred evenly to obtain the acrylic composite emulsion coating.

[0104] Comparative Example 3

[0105] An acrylic emulsion paint, which differs from that in Example 4 in that the acrylic composite emulsion is replaced by a common acrylic emulsion, and other raw material components and proportions are the same as those in Example 4, and the preparation process is also the same as that in Example 4.

[0106] The acrylic emulsion coatings prepared in Examples 4-5 and Comparative Example 3 were tested for performance parameters, wherein the index measurement method is as follows:

[0107] Drying speed: measures the time from coating application until the surface is dry and no longer sticks to fingers;

[0108] Initial hardness: After the coating has dried for 24 hours, use a set of pencils ranging from soft to hard to make a visible scratch on the coating, then use the next harder pencil until the lowest hardness pencil that can scratch the coating is found;

[0109] Weather resistance: Expose the coating sample in an aging test chamber to simulate long-term outdoor exposure. Use a colorimeter to measure the color change of the coating before and after aging, and calculate the color difference value (ΔE);

[0110] Environmental performance: Volatile compounds of paint samples were collected according to standard methods, and VOC content was analyzed using gas chromatography.

[0111] The measured results are shown in Table 2:

[0112] Table 2 Coating performance parameters

[0113]

[0114] It can be seen from the data in Table 2 that the performance parameters measured by the acrylic emulsion coating in Comparative Example 3 are worse than those in the embodiments, mainly because Comparative Example 3 uses a standard acrylic emulsion, which has a slower drying speed, lower initial hardness, poorer weather resistance, and worse environmental performance than the embodiments.

[0115] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. An acrylic composite emulsion coating, characterized in that: The acrylic composite emulsion coating comprises a first topcoat component and a second topcoat component in a mass ratio of 5-10:1; the first topcoat component comprises, by mass percentage, 30-50% of acrylic composite emulsion, 8-12% of titanium dioxide, 10-15% of precipitated barium sulfate, and 12-16% of silicon micropowder or nano silicon dioxide; the second topcoat component comprises, by mass percentage, 15-25% of polyester polyol compounds, 10-30% of diisocyanate compounds, 5-15% of organosiloxane compounds, and 20-55% of organic solvents; wherein the acrylic composite emulsion comprises, by mass percentage, 10-20% of acrylic monomer, 20-40% of butyl acrylate, 3-5% of aldehyde-ketone resin, 4-6% of water-based polyisocyanate, 0.5-1.5% of emulsifier, 0.05-0.15% of initiator, 0.2-0.4% of buffer, and the balance is deionized water.

2. The acrylic composite emulsion coating according to claim 1, characterized in that: In the acrylic composite emulsion, the emulsifier is sodium dodecyl sulfate or aromatic alcohol polyoxyethylene ether; the buffer is one or both of sodium bicarbonate and sodium tripolyphosphate; and the initiator is potassium persulfate.

3. The acrylic composite emulsion coating according to claim 1, characterized in that: The first topcoat component further comprises, by mass percentage: 0.1-0.5% of an amine neutralizer, 0.2-0.8% of a substrate wetting agent, 0.1-0.5% of a defoamer, 0.2-0.8% of a leveling agent, 0.2-0.8% of a rheological additive, and the balance of deionized water.

4. The acrylic composite emulsion coating according to claim 3, characterized in that: The amine neutralizer is dimethylethanolamine; the substrate wetting agent is polyoxyethylene alkylphenol ether; the defoaming agent is polydimethylsiloxane; the leveling agent is a polyacrylate compound; and the rheological additive is hydroxyethyl cellulose.

5. The acrylic composite emulsion coating according to claim 1, characterized in that: The second topcoat component further comprises, by mass percentage: 0.02-0.5% of a curing catalyst and 0.5-1.5% of a neutralizer.

6. The acrylic composite emulsion coating according to claim 5, characterized in that: In the second topcoat component, the polyester polyol compound is polytetramethylene oxide; the diisocyanate compound is isophorone diisocyanate; the organosiloxane compound is α,ω-diaminopropyl polydimethylsiloxane; the curing catalyst is dibutyltin dilaurate; the neutralizer is triethylamine; and the organic solvent is dimethyl carbonate or diethylene glycol carbonate.

7. A method for preparing an acrylic composite emulsion coating as claimed in any one of claims 1 to 6, characterized in that: Includes steps: First add acrylic composite emulsion into the dispersion tank, then add deionized water and amine neutralizer, and adjust to the appropriate pH value; Titanium dioxide, precipitated barium sulfate, silicon micropowder, substrate wetting agent, defoamer, leveling agent and rheological additive are continuously added into the dispersion tank under stirring to obtain a first mixed solution. Adding deionized water or a rheological additive to the first mixed solution to adjust the viscosity and rheological properties to obtain a first topcoat component; In a stirring tank, a polyester polyol compound and a diisocyanate compound are mixed to obtain a second mixed solution; Under stirring conditions, adding an organic siloxane compound, a curing catalyst, and a neutralizer to the second mixed liquid, and adjusting the viscosity with an organic solvent to obtain a second topcoat component; The first topcoat component and the second topcoat component are mixed in a mass ratio of 5-10:1, the second topcoat component is slowly added into the first topcoat component, and after stirring evenly, the acrylic composite emulsion coating is obtained.

8. The method for preparing the acrylic composite emulsion coating according to claim 7, characterized in that: The preparation of the acrylic composite emulsion comprises the steps of: Evenly mixing acrylic acid monomer and butyl acrylate to obtain an acrylic acid mixed solution; In a pre-emulsification tank, 8-10% of the total amount of the acrylic acid mixture is mixed with the aldehyde-ketone resin, and 20-30% of the total amount of the emulsifier is added for pre-emulsification to obtain a pre-emulsified liquid; Adding an appropriate amount of initiator of 5-10% of the total amount to the pre-emulsion, and controlling the temperature to 60-85° C. for preliminary polymerization to form a seed emulsion; In the reactor, add the remaining emulsifier, buffer and deionized water, stir evenly and control the temperature to 70-80° C., then gradually add the seed emulsion and maintain stable conditions in the reactor; The remaining acrylic acid mixture and the remaining initiator solution are mixed evenly and then gradually added dropwise to the reactor to ensure that the polymerization reaction proceeds evenly. After the addition is completed, an aqueous polyisocyanate is added to promote the crosslinking of the emulsion to obtain an initial composite emulsion; The temperature in the reactor is raised to 85-100°C, the initial composite emulsion is aged, then the temperature is lowered to 50-60°C, a buffer is added to adjust the pH, and after keeping the temperature for a predetermined time, the initial composite emulsion is cooled to room temperature, and finally filtered to remove particulate impurities to obtain the acrylic composite emulsion.

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