A water-based color-changing paint and a method for preparing the same

Abstract

This invention discloses a water-based color-changing paint and its preparation method, relating to the field of coatings. The water-based color-changing paint and its preparation method comprise the following raw materials in parts by weight: 600-635 parts modified acrylic emulsion; 12-16 parts dispersant; 150-165 parts titanium dioxide; 9-13 parts abrasion-resistant filler; 21-24 parts dipropylene glycol methyl ether; 27-30 parts dodecyl alcohol ester; 30-33 parts anti-settling agent; 32-35 parts thickener; 10-14 parts functional additives; and 65-72 parts water. The modified acrylic emulsion is selected from modified nitrocellulose containing double bonds and acrylic monomers co-polymerized. The abrasion-resistant filler comprises 6-8 parts modified calcium fluoride nanocrystals and 3-5 parts hydroxylated boron nitride nanosheets loaded with nano-alumina. This application prepares an environmentally friendly and safe water-based color-changing paint with high gloss and texture, high hardness, and good abrasion and scratch resistance.

Description

Technical Field

[0001] This invention relates to the field of coatings, and in particular to a water-based color-changing paint and its preparation method. Background Technology

[0002] Color-changing paint is a coating used to change the color of an object's surface, widely used in car detailing, furniture refurbishment, construction, and industrial corrosion protection. In the car detailing industry, color-changing paint is applied to the car body surface, giving the car a completely new color and texture without altering the original paint structure, protecting the vehicle and enhancing its appearance. Compared to traditional full-car wrapping, car color-changing paint offers higher cost-effectiveness and repairability, and is gradually becoming an important part of the automotive aftermarket.

[0003] Car color-changing paint mainly consists of film-forming substances, pigments, solvents, and additives. The film-forming substances form the foundation of the paint film, determining its hardness and durability. Pigments provide color and hiding power, while solvents adjust viscosity for easier application. With increasing emphasis on environmental protection, water-based color-changing paints are gradually replacing conventional solvent-based paints.

[0004] Commercially available water-based color-changing paints mostly use pure acrylic emulsions as the base film-forming material. However, pure acrylic emulsions have the following drawbacks when used: In order to improve the hardness and scratch resistance of the paint film, it is usually necessary to introduce hard monomers with high glass transition temperatures. However, the introduction of hard monomers will cause the paint film to become brittle and reduce its toughness, making it impossible to present the gloss and quick-drying characteristics of automotive paint. In addition, automotive paint needs to be frequently subjected to high-pressure water gun washing, car wash sponge friction, and sand and dust scratches during long-term use, which puts strict requirements on the wear resistance and scratch resistance of the paint film. Existing filler systems are difficult to disperse in water-based emulsions and cannot achieve high hardness and low friction performance.

[0005] Based on the above problems, this application discloses a new water-based color-changing paint that is environmentally friendly and safe, has a high gloss and texture, high hardness, and good wear resistance and scratch resistance. Summary of the Invention

[0006] In order to prepare an environmentally friendly and safe water-based color-changing paint with high gloss and texture, high hardness and good wear and scratch resistance, this application provides a water-based color-changing paint and its preparation method.

[0007] The water-based color-changing paint and its preparation method provided in this application adopt the following technical solution: A water-based color-changing paint, comprising the following raw materials in parts by weight: Modified acrylic emulsion, 600-635 parts; 12-16 parts of dispersant; 150-165 parts titanium dioxide; 9-13 parts of wear-resistant filler; 21-24 parts of dipropylene glycol methyl ether; 27-30 parts of dodecyl alcohol ester; 30-33 parts anti-settling agent; Thickener 32-35 parts; 10-14 parts of functional additives; 65-72 parts water; The modified acrylate emulsion is made by copolymerizing modified nitrocellulose containing double bonds and acrylate monomers. The wear-resistant filler consists of 6-8 parts modified calcium fluoride nanocrystals and 3-5 parts hydroxylated boron nitride nanosheets loaded with nano-alumina.

[0008] By adopting the above technical solution, in this application, modified acrylate emulsion is selected as the film-forming substance, and nitrocellulose hard segments are chemically bonded to the acrylate molecular chain through free radical copolymerization. Nitrocellulose itself has extremely fast drying speed, extremely high hardness and excellent gloss. The copolymerized acrylate emulsion has the characteristics of fast drying, high gloss, high hardness and high toughness.

[0009] Calcium fluoride itself has the characteristics of low friction coefficient and high wear resistance. At the same time, it will not cause the paint film to lose gloss when mixed with emulsion. Through modification, the dispersibility of filler in water-based system and compatibility with resin are greatly improved. Hydroxylated boron nitride nanosheets loaded with nano-alumina have the characteristics of two-dimensional layer self-lubrication and high hardness. By introducing hydroxyl groups, the compatibility of acrylic emulsion can be neutralized. Loading nano-alumina can avoid the destruction of the layer structure and avoid the agglomeration of alumina itself. The synergistic effect can greatly improve the scratch resistance and wear resistance of the paint film.

[0010] In this system, titanium dioxide acts as a pigment, responsible for coloring and covering; dipropylene glycol methyl ether and dodecyl alcohol ester act as film-forming aids, ensuring that the paint film is intact at room temperature without pinholes or cracking; anti-settling agents and thickeners are adapted to the anti-settling and viscosity requirements of the color-changing paint, giving the color-changing paint long-term storage stability; and functional additives further optimize the application performance.

[0011] Optionally, the modified acrylate emulsion comprises the following raw materials in parts by weight: 45-50 parts of modified nitrocellulose containing double bonds; 42-46 parts of isobornyl methacrylate; 65-70 parts of methyl methacrylate; 90-94 parts of butyl acrylate; 8-12 parts of hydroxyethyl methacrylate phosphate; 6-10 parts acrylic acid; 4-7 parts of compound emulsifier; Initiator 0.8-1.2 parts; 330-350 parts water.

[0012] By adopting the above technical solution, in the modified acrylic emulsion, nitrocellulose grafted with double bonds contributes fast-drying and gloss properties as the hard segment core, while isoborneol methacrylate and methyl methacrylate act as hard monomers, jointly providing hardness. Furthermore, isoborneol methacrylate, being a high-Tg cyclic monomer, can prevent film embrittlement. Butyl acrylate, as a soft monomer, provides long-lasting toughness; hydroxyethyl methacrylate phosphate enhances adhesion, while acrylic acid provides crosslinking points and emulsion stability. The phosphate monomer and carboxyl monomer simultaneously improve emulsion stability, filler wetting, and film adhesion to the substrate. Therefore, the modified acrylic emulsion has advantages such as fast drying, high adhesion, high hardness, good weather resistance, and high gloss.

[0013] Optionally, the modified nitrocellulose containing double bonds comprises the following raw materials in parts by weight: 36-42 parts of nitrocellulose; 6-9 parts of isoethyl methacrylate; The solvent is 5-8 parts, and a mixture of propylene glycol methyl ether and butyl acetate in a mass ratio of 1:1 is selected. Catalyst 0.03-0.06 parts.

[0014] By adopting the above technical solution, ethyl isocyanate methacrylate is selected to modify nitrocellulose. The isocyanate group and hydroxyl group undergo a polyurethane addition reaction, thereby grafting polymerizable double bonds onto the nitrated molecular chain, which is beneficial for subsequent copolymerization with acrylate monomers and improves the compatibility with acrylate monomers.

[0015] Optionally, the modified calcium fluoride nanocrystals are prepared by synergistic modification with tridecafluorooctyltrimethoxysilane and monododecyl phosphate through the following steps: Calcium fluoride nanocrystals were vacuum dried to remove water, dispersed in anhydrous ethanol, and prepared into a dispersion with a solid content of 15%-20%. The dispersion was then ultrasonically dispersed for 20-30 minutes to deagglomerate the particles. Add 1.5%-1.8% of monododecyl phosphate and 1.0%-1.2% of tridecafluorooctyltrimethoxysilane by mass of calcium fluoride nanocrystals, adjust the pH of the system to 5.0-6.0 with glacial acetic acid, raise the temperature to 60-65℃, and keep the reaction at this temperature for 2.5-3 hours. Unreacted modifier was removed by centrifugation and washing, followed by vacuum drying to obtain modified calcium fluoride nanocrystals.

[0016] By adopting the above technical solution, the phosphate ester groups are strongly coordinated and anchored to the calcium ions on the surface of calcium fluoride. After hydrolysis, the fluorosilane is condensed and grafted with the hydroxyl groups on the surface of the filler. The dual modification can significantly improve the dispersibility of the filler in the water-based system and its compatibility with the resin, while reducing the surface friction coefficient of the paint film and improving scratch resistance.

[0017] Optionally, the hydroxylated boron nitride nanosheets loaded with nano-alumina are prepared by the following steps: Boron nitride nanosheets were placed in a 5-8 mol / L sodium hydroxide solution and stirred at 100-150℃ for 20-24 h. After stirring, the nanosheets were centrifuged, washed, and dried to obtain hydroxylated boron nitride. Hydroxylated boron nitride and nano-alumina were mixed at a mass ratio of (3.5-4):1. Zirconia grinding balls were used, and anhydrous ethanol accounting for 5-10% of the total mass of the powder was added as a grinding aid. The temperature was maintained at 0-5℃ for 1 hour. The grinding aid was removed by vacuum drying, and the nano-alumina was obtained by sieving.

[0018] By adopting the above technical solution, a large number of hydroxyl groups are introduced on the surface of boron nitride nanosheets through high-temperature hydrothermal treatment with sodium hydroxide, and nano-alumina is loaded with low-temperature spherical graphite. This can protect the layered structure of boron nitride while uniformly loading nano-alumina, so that the filler will not agglomerate. The compatibility in acrylic emulsion is improved, and the scratch resistance and wear resistance of the paint film are enhanced by "two-dimensional self-lubrication + zero-dimensional high hardness".

[0019] Optionally, the functional additives specifically include: 2-5 parts of preservative, 5-8 parts of defoamer, and 2-4 parts of leveling agent.

[0020] Optionally, the composite emulsifier is selected from two or more of sodium alkyl diphenyl ether disulfonate, sodium dodecyl sulfate, nonylphenol polyoxyethylene ether, and isomeric alcohol polyoxyethylene ether, and the initiator is selected from any one of ammonium persulfate, sodium persulfate, and potassium persulfate.

[0021] Optionally, the catalyst is dibutyltin dilaurate.

[0022] A method for preparing a water-based color-changing paint includes the following steps: Dispersant, 20-25 parts water and wear-resistant filler are ultrasonically dispersed to obtain a mixture. 300-350 parts modified acrylate emulsion, titanium dioxide and the mixture are added to a stirred tank and dispersed at high speed. The remaining modified acrylate emulsion is added and dispersed for 10-15 minutes. Dipropylene glycol methyl ether, dodecyl alcohol ester and 28-32 parts water are mixed evenly in advance and slowly added to the stirred tank and dispersed for 8-12 minutes. Then, anti-settling agent, thickener, functional additives and the remaining water are added in sequence and stirred evenly before discharge.

[0023] By adopting the above technical solution, the wear-resistant filler is dispersed in advance, and the film-forming aid and water are mixed in advance, which makes the dispersion of the whole system easier and the system more stable.

[0024] Optionally, the preparation of the modified acrylate emulsion includes the following steps: Dissolve the dried nitrocellulose in a solvent to prepare a nitrocellulose solution; heat to 60-65℃, add a catalyst, and slowly add isocyanate methacrylate dropwise over 30-40 minutes. After the reaction is complete, keep the temperature constant for 2-3 hours. After cooling to below 50°C, add 46-50 parts of butyl acrylate and 27-32 parts of methyl methacrylate, stir at high speed to obtain a clear oil phase liquid, evacuate to a vacuum degree of -0.095MPa to -0.098MPa, slowly heat to 90-95°C, remove the solvent by vacuum extraction, and then purge with nitrogen to restore normal pressure to obtain modified nitrocellulose-monomer liquid; Mix 280-300 parts of deionized water and composite emulsifier evenly to obtain an aqueous solution; disperse the remaining monomer and 40-45 parts of deionized water at high speed to obtain a pre-emulsion; mix part of the initiator and the remaining deionized water to obtain an initiator solution. Heat the aqueous solution to 80-83℃, add part of the pre-emulsion and part of the initiator solution, stir for 5-10 minutes to form a seed solution, add the modified nitrocellulose monomer solution and part of the initiator solution, and add the solution at a rate controlled at 1.5-2 hours. Continue to add the remaining pre-emulsion and initiator solution, and add the solution at a rate controlled at 2-2.5 hours. Keep the reaction at this temperature for 1-2 hours, then heat to 85-87℃, add the solid initiator and keep the temperature for 30-40 minutes. Cool the system to below 45°C, add neutralizing solution to adjust the pH to 7.5-8, and filter to obtain the modified acrylic emulsion.

[0025] By adopting the above technical solution, acrylate monomers are added in advance after the modified nitrocellulose is prepared, and the solvent is removed by vacuum extraction, thereby reducing the VOC value of the emulsion, which is in line with environmental protection and safety principles. The seed emulsion polymerization method allows for precise control of latex particle size and distribution, significantly reducing the polymerization gelation rate and ensuring the storage stability of the emulsion.

[0026] In summary, this application has the following beneficial effects: By selecting modified acrylate emulsion as the film-forming substance, the hard segments of nitrocellulose are chemically bonded to the acrylate molecular chain through free radical copolymerization. Nitrocellulose itself has extremely fast drying speed, extremely high hardness and excellent gloss. The copolymerized acrylate emulsion has the characteristics of fast drying, high gloss, high hardness and high toughness.

[0027] Calcium fluoride itself has the characteristics of low friction coefficient and high wear resistance. At the same time, it will not cause the paint film to lose gloss when mixed with emulsion. Through modification, the dispersibility of filler in water-based system and compatibility with resin are greatly improved. Hydroxylated boron nitride nanosheets loaded with nano-alumina have the characteristics of two-dimensional layer self-lubrication and high hardness. By introducing hydroxyl groups, the compatibility of acrylic emulsion can be neutralized. Loading nano-alumina can avoid the destruction of the layer structure and avoid the agglomeration of alumina itself. The synergistic effect can greatly improve the scratch resistance and wear resistance of the paint film.

[0028] In this system, titanium dioxide acts as a pigment, responsible for coloring and covering; dipropylene glycol methyl ether and dodecyl alcohol ester act as film-forming aids, ensuring that the paint film is intact at room temperature without pinholes or cracking; anti-settling agents and thickeners are adapted to the anti-settling and viscosity requirements of the color-changing paint, giving the color-changing paint long-term storage stability; and functional additives further optimize the application performance. Detailed Implementation

[0029] The present application will be further described in detail below with reference to Examples 1-3 and Comparative Examples 1-3. Preparation Example

[0030] Preparation Example 1 A modified acrylic emulsion, comprising the following raw materials: 45 kg of modified nitrocellulose containing double bonds 42 kg of isoborneol methacrylate, 65 kg of methyl methacrylate 90 kg of butyl acrylate, 8 kg of hydroxyethyl methacrylate phosphate Acrylic acid 6kg, initiator 0.8kg, ammonium persulfate selected. 4 kg of composite emulsifier, 2 kg of sodium alkyl diphenyl ether disulfonate and 2 kg of nonylphenol polyoxyethylene ether, and 330 kg of water were selected.

[0031] The modified nitrocellulose containing double bonds is prepared from the following raw materials: 36 kg of nitrocellulose, 6 kg of isocyanate methacrylate 5 kg of solvent, using 2.5 kg of propylene glycol methyl ether and 2.5 kg of butyl acetate. 0.03 kg of catalyst was selected, and dibutyltin dilaurate was chosen.

[0032] Modified acrylate emulsions are prepared by the following method: The dried nitrocellulose was dissolved in a solvent to prepare a nitrocellulose solution; the temperature was raised to 60°C, a catalyst was added, and ethyl isocyanate methacrylate was slowly added dropwise over 30 minutes. After the reaction was completed, the temperature was maintained for 2 hours. After cooling down to below 50°C, 46 kg of butyl acrylate and 27 kg of methyl methacrylate were added. The mixture was stirred at high speed to obtain a clear oil phase liquid. The vacuum was drawn to a vacuum degree of -0.095 MPa, and the temperature was slowly raised to 90°C. After vacuum extraction to remove the solvent, nitrogen gas was purged to restore the atmospheric pressure, and the modified nitrocellulose-monomer liquid was obtained. 280 kg of deionized water and composite emulsifier were mixed evenly to obtain an aqueous solution; the remaining monomers (including 44 kg of butyl acrylate and 38 kg of methyl methacrylate) and 40 kg of deionized water were dispersed at high speed to obtain a pre-emulsion; 0.6 kg of initiator and 10 kg of deionized water were mixed to obtain an initiator solution. The aqueous solution was heated to 80°C, and a portion of the pre-emulsion and initiator solution were added. The mixture was stirred for 5 minutes to form a seed solution. Modified nitrocellulose monomer solution and a portion of the initiator solution were then added to the seed solution. The dropping rate was controlled to be completed in 1.5 hours. The remaining pre-emulsion and initiator solution were then added dropwise, with the dropping time controlled to be completed in 2 hours. The reaction was kept at this temperature for 1 hour. The temperature was then raised to 85°C, and 0.2 kg of solid initiator was added and kept at this temperature for 30 minutes. Cool the system to below 45°C, add neutralizing solution to adjust the pH to 7.5-8, and filter to obtain the modified acrylic emulsion.

[0033] Preparation Example 2 A modified acrylic emulsion, comprising the following raw materials: 50 kg of modified nitrocellulose containing double bonds 46 kg of isobornyl methacrylate, 70 kg of methyl methacrylate 94 kg of butyl acrylate, 12 kg of hydroxyethyl methacrylate phosphate 10 kg of acrylic acid and 1.2 kg of initiator, using ammonium persulfate. 7 kg of composite emulsifier, 4 kg of sodium dodecyl sulfate, 3 kg of isomeric alcohol polyoxyethylene ether, and 350 kg of water were selected.

[0034] The modified nitrocellulose containing double bonds is prepared from the following raw materials: 42 kg of nitrocellulose, 9 kg of isocyanate methacrylate 8 kg of solvent, using 4 kg of propylene glycol methyl ether and 4 kg of butyl acetate. The catalyst is 0.06 kg, and dibutyltin dilaurate is selected.

[0035] Modified acrylate emulsions are prepared by the following method: The dried nitrocellulose was dissolved in a solvent to prepare a nitrocellulose solution; the temperature was raised to 65°C, a catalyst was added, and ethyl isocyanate methacrylate was slowly added dropwise over a period of 40 minutes. After the reaction was completed, the temperature was maintained for 3 hours. After cooling down to below 50°C, 50 kg of butyl acrylate and 32 kg of methyl methacrylate were added. The mixture was stirred at high speed to obtain a clear oil phase liquid. The vacuum was drawn to a vacuum degree of -0.098 MPa, and the temperature was slowly raised to 95°C. After vacuum extraction to remove the solvent, nitrogen gas was purged to restore the atmospheric pressure, and the modified nitrocellulose-monomer liquid was obtained. 300 kg of deionized water and composite emulsifier were mixed evenly to obtain an aqueous solution; the remaining monomer and 45 kg of deionized water were dispersed at high speed to obtain a pre-emulsion; 0.9 kg of initiator and 5 kg of deionized water were mixed to obtain an initiator solution. The aqueous solution was heated to 83°C, and a portion of the pre-emulsion and initiator solution were added. The mixture was stirred for 10 minutes to form a seed solution. Modified nitrocellulose monomer solution and a portion of the initiator solution were then added to the seed solution. The dropping rate was controlled to be completed in 2 hours. The remaining pre-emulsion and initiator solution were added dropwise, with the dropping time controlled to be completed in 2.5 hours. The reaction was kept at this temperature for 2 hours. The temperature was then raised to 87°C, and 0.3 kg of solid initiator was added and kept at this temperature for 40 minutes. Cool the system to below 45°C, add neutralizing solution to adjust the pH to 7.5-8, and filter to obtain the modified acrylic emulsion.

[0036] Preparation Example 3 A modified acrylic emulsion, comprising the following raw materials: 48 kg of modified nitrocellulose containing double bonds 43 kg of isoborneol methacrylate, 67 kg of methyl methacrylate 92 kg of butyl acrylate, 11 kg of hydroxyethyl methacrylate phosphate 8 kg of acrylic acid and 1 kg of initiator, using ammonium persulfate. 6 kg of composite emulsifier, 2 kg of sodium dodecyl sulfate and 4 kg of nonylphenol polyoxyethylene ether, and 340 kg of water were selected.

[0037] The modified nitrocellulose containing double bonds is prepared from the following raw materials: 39 kg of nitrocellulose, 7 kg of isocyanate methacrylate 6 kg of solvent, using 3 kg of propylene glycol methyl ether and 3 kg of butyl acetate. 0.05 kg of catalyst was selected, and dibutyltin dilaurate was chosen.

[0038] In this preparation example, the method for preparing the modified acrylate emulsion is the same as that in Preparation Example 1.

[0039] Preparation Example 4 A modified calcium fluoride nanocrystal is prepared by the following steps: 6 kg of calcium fluoride nanocrystals were vacuum dried to remove water and dispersed in 40 kg of anhydrous ethanol to prepare a dispersion with a solid content of 15%. The dispersion was ultrasonically dispersed for 20 min to deagglomerate the particles. 0.09 kg of monododecyl phosphate and 0.06 kg of tridecafluorooctyltrimethoxysilane were added to the dispersion. The pH of the system was adjusted to 5.0-6.0 with glacial acetic acid. The temperature was raised to 60 °C and kept at that temperature for 2.5 h. The unreacted modifier was removed by centrifugation and washing, and the mixture was vacuum dried to obtain modified calcium fluoride nanocrystals.

[0040] Preparation Example 5 A modified calcium fluoride nanocrystal is prepared by the following steps: 6 kg of calcium fluoride nanocrystals were vacuum dried to remove water and dispersed in 30 kg of anhydrous ethanol to prepare a dispersion with a solid content of 20%. The dispersion was ultrasonically dispersed for 30 min to deagglomerate the particles. 0.108 kg of monododecyl phosphate and 0.072 kg of tridecafluorooctyltrimethoxysilane were added to the dispersion. The pH of the system was adjusted to 5.0-6.0 with glacial acetic acid. The temperature was raised to 65 °C and kept at that temperature for 3 h. The unreacted modifier was removed by centrifugation and washing, and the mixture was vacuum dried to obtain modified calcium fluoride nanocrystals.

[0041] Preparation Example 6 A hydroxylated boron nitride nanosheet loaded with nano-alumina is prepared by the following steps: Boron nitride nanosheets were placed in a 5 mol / L sodium hydroxide solution and stirred at 100 °C for 20 h. After stirring, the nanosheets were centrifuged, washed, and dried to obtain hydroxylated boron nitride. 3.5 kg of hydroxylated boron nitride and 1 kg of nano-alumina were mixed, and 0.225 kg of anhydrous ethanol was added as a grinding aid using zirconia grinding balls. The mixture was kept at 0 °C for 1 hour, and the grinding aid was removed by vacuum drying. After sieving, hydroxylated boron nitride nanosheets loaded with nano-alumina were obtained.

[0042] Preparation Example 7 A hydroxylated boron nitride nanosheet loaded with nano-alumina is prepared by the following steps: Boron nitride nanosheets were placed in an 8 mol / L sodium hydroxide solution and stirred at 150 °C for 24 h. After stirring, the nanosheets were centrifuged, washed, and dried to obtain hydroxylated boron nitride. 4 kg of hydroxylated boron nitride and 1 kg of nano-alumina were mixed, and 0.5 kg of anhydrous ethanol was added as a grinding aid using zirconia grinding balls. The mixture was kept at 5°C for 1 hour, and then vacuum dried to remove the grinding aid. After sieving, hydroxylated boron nitride nanosheets loaded with nano-alumina were obtained. Example

[0043] Example 1 This embodiment discloses a water-based color-changing paint, comprising the following raw materials: 600 kg of modified acrylate emulsion, sourced from Preparation Example 1; 12kg of dispersant, model Yujin DY2076w dispersant; 150kg of titanium dioxide, type R369; 9 kg of wear-resistant filler was used, and 6 kg of modified calcium fluoride nanocrystals prepared in Example 4 and 3 kg of hydroxylated boron nitride nanosheets loaded with nano-alumina prepared in Example 6 were selected. 21 kg of dipropylene glycol methyl ether; 27 kg of dodecyl alcohol ester; 30 kg of anti-settling agent, using 20 kg of organic bentonite and 10 kg of polyamide wax; Thickener 32kg, model HY210, Haoyi New Materials; 10 kg of functional additives, including 3 kg of preservative, 5 kg of defoamer and 2 kg of leveling agent; Water 65kg.

[0044] The preparation method of water-based color-changing paint includes the following steps: Dispersant, 20kg water and wear-resistant filler are ultrasonically dispersed to obtain a mixture. 300kg of modified acrylate emulsion, titanium dioxide and the mixture are added to a stirred tank and dispersed at high speed. The remaining (300kg) modified acrylate emulsion is added and dispersed for 10min. Dipropylene glycol methyl ether, dodecyl alcohol ester and 28kg water are mixed evenly in advance and slowly added to the stirred tank and dispersed for 8min. Then, anti-settling agent, thickener, functional additive and the remaining (17kg) water are added in sequence and stirred evenly before discharge.

[0045] Example 2 This embodiment discloses a water-based color-changing paint, comprising the following raw materials: 635 kg of modified acrylate emulsion, sourced from Preparation Example 2; 16kg of dispersant, model Yujin DY2076w dispersant; 165kg of titanium dioxide, type R369; 13 kg of wear-resistant filler was used, consisting of 8 kg of modified calcium fluoride nanocrystals prepared in Example 5 and 5 kg of hydroxylated boron nitride nanosheets loaded with nano-alumina prepared in Example 7. 24 kg of dipropylene glycol methyl ether; 30 kg of dodecanol ester; 33 kg of anti-settling agent, using 20 kg of organic bentonite and 13 kg of polyamide wax; Thickener 35kg, model HY210, Haoyi New Materials; 14 kg of functional additives, including 3 kg of preservative, 8 kg of defoamer and 3 kg of leveling agent; 72kg of water.

[0046] The preparation method of water-based color-changing paint includes the following steps: Dispersant, 25 kg of water and wear-resistant filler are ultrasonically dispersed to obtain a mixture. 350 kg of modified acrylate emulsion, titanium dioxide and the mixture are added to a stirred tank and dispersed at high speed. 285 kg of modified acrylate emulsion is added and dispersed for 15 min. Dipropylene glycol methyl ether, dodecyl alcohol ester and 32 kg of water are mixed evenly in advance and slowly added to the stirred tank and dispersed for 12 min. Then, anti-settling agent, thickener, functional additive and 15 kg of water are added in sequence and stirred evenly before discharge.

[0047] Example 3 This embodiment discloses a water-based color-changing paint, comprising the following raw materials: 615 kg of modified acrylate emulsion, sourced from Preparation Example 3; 14 kg of dispersant, model Yujin DY2076w dispersant; 158 kg of titanium dioxide, type R369; 11 kg of wear-resistant filler was used, consisting of 7 kg of modified calcium fluoride nanocrystals prepared in Example 4 and 4 kg of hydroxylated boron nitride nanosheets loaded with nano-alumina prepared in Example 7. 22 kg of dipropylene glycol methyl ether; 29 kg of dodecyl alcohol ester; 31 kg of anti-settling agent, made of organic bentonite; Thickener 34kg, model HY210, Haoyi New Materials; 12 kg of functional additives, including 2 kg of preservative, 6 kg of defoamer and 4 kg of leveling agent; Water 69kg.

[0048] The preparation method of the water-based color-changing paint is the same as that in Example 1. Comparative Example

[0049] Comparative Example 1 The difference between this comparative example and Example 1 is that the modified acrylic emulsion in the color-changing paint raw material is different.

[0050] In this comparative example, an equal amount of acrylate emulsion was used instead of the modified acrylate emulsion in Preparation Example 1. The waterborne acrylate emulsion was Neocryl® XK-160, manufactured by Haoyi New Materials.

[0051] Comparative Example 2 The difference between this comparative example and Example 1 is that the wear-resistant filler in the color-changing paint raw material is different.

[0052] In this comparative example, an equal amount of wear-resistant filler was used to replace the modified calcium fluoride nanocrystals of Preparation Example 4 and the hydroxylated boron nitride nanosheets loaded with nano-alumina of Preparation Example 6. The wear-resistant filler was HY823, a wear-resistant agent from Haoyi New Materials, and its main component was modified nano-alumina.

[0053] Comparative Example 3 The difference between this comparative example and Example 1 is that the modified acrylic emulsion in the color-changing paint raw material is different.

[0054] In this comparative example, no modified nitrocellulose containing double bonds was added to the raw materials of the modified acrylate emulsion.

[0055] Performance testing The following performance tests were conducted on the water-based color-changing paints prepared in Examples 1-3 and Comparative Examples 1-3, and the test results are shown in Table 1.

[0056] Hardness: The test was conducted according to the method of GB / T 6739-2022 "Determination of Hardness of Paint Film by Pencil Method", and the results were recorded.

[0057] VOC content: The test was conducted according to the method of GB / T 23986-2009 "Determination of Volatile Organic Compounds (VOCs) in Paints and Varnishes by Gas Chromatography", and the results were recorded.

[0058] Surface drying time: Tested according to the method of GB / T 1728-2020 "Determination of drying time of paint film and putty film", and the results were recorded.

[0059] Gloss: The 60° specular gloss was tested according to the method in GB / T 9594-2007 "Determination of 20°, 60˚ and 85˚ specular gloss of paint films without metallic pigments".

[0060] Table 1 sample hardness VOC content (g / L) Drying time (min) Gloss (60°, %) Example 1 2H 110 33 96 Example 2 2H 110 35 95 Example 3 2H 100 32 95 Comparative Example 1 H 80 61 83 Comparative Example 2 H 100 38 86 Comparative Example 3 H 90 56 90 Based on the data in Table 1, it can be seen that the water-based color-changing paint of this application is produced by adding nitrocellulose containing double bonds modified with isocyanate methacrylate to the acrylic emulsion for co-polymerization, which gives the acrylic emulsion the fast-drying and gloss properties of nitrocellulose. Furthermore, by adding modified calcium fluoride nanocrystals and hydroxylated silicon nitride nanosheets loaded with nano-alumina as composite wear-resistant fillers, the wear resistance, hardness, and scratch resistance of the color-changing paint system are improved, thus making it more suitable for the use of automotive color-changing paint.

[0061] Comparative Examples 1 and 3 modified the acrylic emulsions, demonstrating that the acrylic emulsions without the introduction of nitrocellulose, due to the addition of hard monomers with high Tg, resulted in decreased film toughness, prolonged surface drying time, and decreased gloss.

[0062] Comparative Example 2 modified the wear-resistant filler, demonstrating that traditional fillers have poor compatibility when added to acrylic emulsion systems, and adversely affect the gloss and hardness of the system.

[0063] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this specific embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A water-based color-changing paint, characterized in that: Including the following parts by weight of raw materials: Modified acrylic emulsion, 600-635 parts; 12-16 parts of dispersant; 150-165 parts titanium dioxide; 9-13 parts of wear-resistant filler; 21-24 parts of dipropylene glycol methyl ether; 27-30 parts of dodecyl alcohol ester; 30-33 parts anti-settling agent; Thickener 32-35 parts; 10-14 parts of functional additives; 65-72 parts water; The modified acrylate emulsion is made by copolymerizing modified nitrocellulose containing double bonds and acrylate monomers. The wear-resistant filler consists of 6-8 parts modified calcium fluoride nanocrystals and 3-5 parts hydroxylated boron nitride nanosheets loaded with nano-alumina.

2. The water-based color-changing paint according to claim 1, characterized in that: The modified acrylic emulsion comprises the following raw materials in parts by weight: 45-50 parts of modified nitrocellulose containing double bonds; 42-46 parts of isobornyl methacrylate; 65-70 parts of methyl methacrylate; 90-94 parts of butyl acrylate; 8-12 parts of hydroxyethyl methacrylate phosphate; 6-10 parts acrylic acid; 4-7 parts of compound emulsifier; Initiator 0.8-1.2 parts; 330-350 parts water.

3. The water-based color-changing paint according to claim 2, characterized in that: The modified nitrocellulose containing double bonds comprises the following raw materials in parts by weight: 36-42 parts of nitrocellulose; 6-9 parts of isoethyl methacrylate; The solvent is 5-8 parts, and a mixture of propylene glycol methyl ether and butyl acetate in a mass ratio of 1:1 is selected. Catalyst 0.03-0.06 parts.

4. The water-based color-changing paint according to claim 1, characterized in that: The modified calcium fluoride nanocrystals are prepared by synergistic modification with tridecafluorooctyltrimethoxysilane and monododecyl phosphate through the following steps: Calcium fluoride nanocrystals were vacuum dried to remove water, dispersed in anhydrous ethanol, and prepared into a dispersion with a solid content of 15%-20%. The dispersion was then ultrasonically dispersed for 20-30 minutes to deagglomerate the particles. Add 1.5%-1.8% of monododecyl phosphate and 1.0%-1.2% of tridecafluorooctyltrimethoxysilane by mass of calcium fluoride nanocrystals, adjust the pH of the system to 5.0-6.0 with glacial acetic acid, raise the temperature to 60-65℃, and keep the reaction at this temperature for 2.5-3 hours. Unreacted modifier was removed by centrifugation and washing, followed by vacuum drying to obtain modified calcium fluoride nanocrystals.

5. The water-based color-changing paint according to claim 1, characterized in that: The hydroxylated boron nitride nanosheets loaded with nano-alumina were prepared by the following steps: Boron nitride nanosheets were placed in a 5-8 mol / L sodium hydroxide solution and stirred at 100-150℃ for 20-24 h. After stirring, the nanosheets were centrifuged, washed, and dried to obtain hydroxylated boron nitride. Hydroxylated boron nitride and nano-alumina were mixed at a mass ratio of (3.5-4):

1. Zirconia grinding balls were used, and anhydrous ethanol accounting for 5-10% of the total mass of the powder was added as a grinding aid. The temperature was maintained at 0-5℃ for 1 hour. The grinding aid was removed by vacuum drying, and the nano-alumina was obtained by sieving.

6. The water-based color-changing paint according to claim 1, characterized in that: The functional additives specifically include: 2-5 parts of preservative, 5-8 parts of defoamer, and 2-4 parts of leveling agent.

7. The water-based color-changing paint according to claim 2, characterized in that: The composite emulsifier is selected from two or more of sodium alkyl diphenyl ether disulfonate, sodium dodecyl sulfate, nonylphenol polyoxyethylene ether, and isomeric alcohol polyoxyethylene ether, and the initiator is selected from any one of ammonium persulfate, sodium persulfate, and potassium persulfate.

8. The water-based color-changing paint according to claim 3, characterized in that: The catalyst used is dibutyltin dilaurate.

9. A method for preparing a water-based color-changing paint according to any one of claims 1-8, characterized in that, Includes the following steps: Dispersant, 20-25 parts water and wear-resistant filler are ultrasonically dispersed to obtain a mixture. 300-350 parts modified acrylate emulsion, titanium dioxide and the mixture are added to a stirred tank and dispersed at high speed. The remaining modified acrylate emulsion is added and dispersed for 10-15 minutes. Dipropylene glycol methyl ether, dodecyl alcohol ester and 28-32 parts water are mixed evenly in advance and slowly added to the stirred tank and dispersed for 8-12 minutes. Then, anti-settling agent, thickener, functional additives and the remaining water are added in sequence and stirred evenly before discharge.

10. The method for preparing a water-based color-changing paint according to claim 9, characterized in that, The preparation of the modified acrylate emulsion includes the following steps: Dissolve the dried nitrocellulose in a solvent to prepare a nitrocellulose solution; heat to 60-65℃, add a catalyst, and slowly add isocyanate methacrylate dropwise over 30-40 minutes. After the reaction is complete, keep the temperature constant for 2-3 hours. After cooling to below 50°C, add 46-50 parts of butyl acrylate and 27-32 parts of methyl methacrylate, stir at high speed to obtain a clear oil phase liquid, evacuate to a vacuum degree of -0.095MPa to -0.098MPa, slowly heat to 90-95°C, remove the solvent by vacuum extraction, and then purge with nitrogen to restore normal pressure to obtain modified nitrocellulose-monomer liquid; Mix 280-300 parts of deionized water and composite emulsifier evenly to obtain an aqueous solution; disperse the remaining monomer and 40-45 parts of deionized water at high speed to obtain a pre-emulsion; mix part of the initiator and the remaining deionized water to obtain an initiator solution. Heat the aqueous solution to 80-83℃, add part of the pre-emulsion and part of the initiator solution, stir for 5-10 minutes to form a seed solution, add the modified nitrocellulose monomer solution and part of the initiator solution, and add the solution at a rate controlled at 1.5-2 hours. Continue to add the remaining pre-emulsion and initiator solution, and add the solution at a rate controlled at 2-2.5 hours. Keep the reaction at this temperature for 1-2 hours, then heat to 85-87℃, add the solid initiator and keep the temperature for 30-40 minutes. Cool the system to below 45°C, add neutralizing solution to adjust the pH to 7.5-8, and filter to obtain the modified acrylic emulsion.