Aqueous UV Dual-Cure Dispersions for Aluminum Alloys, Their Preparation Methods and Applications

Abstract

This invention provides an aqueous UV dual-curing dispersion for aluminum alloys, its preparation method, and its application. The dispersion consists of 26-33% UV-curable prepolymer, 11-17% hydroxyl acrylic acid prepolymer, and 55-60% water. The UV-curable prepolymer comprises the following components in parts by weight: 2-4 parts UV-curable diluent monomer, 0.5-1.5 parts hydroxy acid monomer, 4-6 parts isocyanate, 3-5 parts polyol, 0.02-0.06 parts catalyst, 0.005-0.01 parts polymerization inhibitor, 6-9 parts solvent, 16-24 parts hydroxy acrylate, and 0.5-1 parts neutralizer; the hydroxy acrylic acid prepolymer comprises the following components in parts by weight: 1-5 parts acrylic monomer, 20-35 parts acrylate monomer, 10-30 parts vinyl monomer, 12-20 parts hydroxy acrylic monomer, 1-10 parts neutralizer, 0.1-0.4 parts initiator, 0.01-0.04 parts polymerization inhibitor, 0.03-0.12 parts antioxidant, and 15-35 parts solvent. This invention is already surface-dried and has certain properties before UV curing, allowing for the processing and casting of the substrate. After the parts are formed, UV curing is performed, resulting in not only good adhesion but also high hardness and excellent solvent resistance.

Description

Technical Field

[0001] This invention relates to the field of coating resin technology for automobiles, mobile phones, home appliances and other fields, and more specifically, to an aqueous UV dual-curing dispersion for aluminum alloys, its preparation method and application. Background Technology

[0002] Aluminum alloys, due to their lightweight characteristics, are gradually gaining attention. They also possess excellent strength, corrosion resistance, and high recyclability, leading to their widespread application in automobiles, mobile phones, and high-end home appliances. Furthermore, high-end mobile phones, in pursuit of superior appearance, feel, and performance, extensively utilize aluminum alloy frames and casings. Therefore, the use of aluminum alloys will continue to increase, and they will receive increasing attention.

[0003] However, due to the complex and demanding operating environments, aluminum alloy materials generally require a coating to cope with various conditions and extend their service life. Furthermore, the high density of aluminum alloy surfaces, coupled with the varying types and proportions of alloys used in different applications, makes it extremely difficult for various coatings to adhere. Additionally, maintaining the density and good metallic appearance of aluminum alloy surfaces typically avoids polishing, further complicating coating adhesion.

[0004] Currently, the process for using aluminum alloy materials in the automotive and other fields involves first machining the parts into shape, and then painting them. This process, due to the irregular structure of the parts, results in uneven paint film thickness, leading to inconsistent gloss and poor adhesion. Furthermore, in an effort to improve adhesion, the paint film hardness is generally low, and solvent resistance is poor, significantly limiting the material's usability. Summary of the Invention

[0005] In view of the above-mentioned shortcomings in the prior art, the purpose of this invention is to provide an aqueous UV dual-curing dispersion for aluminum alloys, its preparation method and application. The product is already surface-dried and has certain properties before UV curing, and can be used to process and cast the substrate. After the parts are formed, UV curing is performed. It not only has good adhesion to aluminum alloy materials, but also has high hardness and excellent solvent resistance. Moreover, it uses water as a solvent, which is environmentally friendly and pollution-free.

[0006] To achieve the above objectives, the present invention provides an aqueous UV dual-curing dispersion for aluminum alloys, wherein the dispersion comprises 26-33% UV-curable prepolymer, 11-17% hydroxyl acrylic acid prepolymer, and 55-60% water; wherein the UV-curable prepolymer comprises the following components in parts by weight: 2-4 parts UV-curable diluent monomer, 0.5-1.5 parts hydroxy acid monomer, 4-6 parts isocyanate, 3-5 parts polyol, 0.02-0.06 parts catalyst, and 0.005 parts polymerization inhibitor. -0.01 parts, solvent 6-9 parts, hydroxy acrylate 16-24 parts, neutralizer 0.5-1 parts; the hydroxy acrylic acid prepolymer includes the following components in parts by weight: acrylic monomer 1-5 parts, acrylate monomer 20-35 parts, vinyl monomer 10-30 parts, hydroxy acrylic monomer 12-20 parts, neutralizer 1-10 parts, initiator 0.1-0.4 parts, polymerization inhibitor 0.01-0.04 parts, antioxidant 0.03-0.12 parts, solvent 15-35 parts.

[0007] Optionally, the water content of the UV-curable diluent monomer, hydroxy acid monomer, isocyanate, polyol, catalyst, polymerization inhibitor, solvent, hydroxy acrylate, and neutralizer is all less than 500 ppm.

[0008] Optionally, the UV-curable diluent monomer is at least one selected from 1,6-hexanediol diacrylate (HDDA), dipropylene glycol diacrylate (DPGDA), tripropylene glycol diacrylate (TPGDA), and trimethylolpropane triacrylate (TMPTA).

[0009] Optionally, the hydroxy acid monomer is at least one of 2,2-dimethylolpropionic acid (DMPA), dimethylolbutyric acid (DMBA), and hydroxyethylsulfonic acid.

[0010] Optionally, the isocyanate is at least one selected from isoflurane diisocyanate (IPDI), hexamethylene diisocyanate (HDI), diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), hexamethylene diisocyanate trimer, and 4,4'-dicyclohexylmethane diisocyanate (HMDI); and the polyol is at least one selected from silicon-containing polyols, polyether polyols, polyester polyols, caprolactone polyols, and polycarbonate polyols.

[0011] Optionally, the catalyst is at least one of pentamethyldiethylenetriamine, dibutyltin dilaurate, organobismuth, solid amine, N-methylmorpholine, and N,N'-diethylpiperazine; the polymerization inhibitor is at least one of p-hydroxyanisole, hydroquinone, and 2,5-dimethylhydroquinone; the solvent is at least one of acetone, butanone, ethyl acetate, and butyl acetate; the hydroxyacrylate is at least one of pentaerythritol pentaacrylate, pentaerythritol triacrylate, butyl hydroxyacrylate, and ethyl hydroxyacrylate; and the neutralizing agent is at least one of triethylamine, N,N-dimethylethanolamine, ammonia, sodium hydroxide, and potassium hydroxide.

[0012] Optionally, the acrylic monomer is at least one of acrylic acid and methacrylic acid; the acrylate monomer is at least one of butyl acrylate, methyl methacrylate, and methyl acrylate; the vinyl monomer is at least one of styrene and epoxy acrylate; and the hydroxy acrylic monomer is at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, and hydroxyethyl methacrylate.

[0013] Optionally, the initiator is at least one of di-tert-butyl peroxide, di-tert-pentyl peroxide, benzoyl peroxide (BPO), azobisisobutyronitrile (AIBN), and azobisisoheptanenitrile; the antioxidant is at least one of phenothiazine, 2,6-di-tert-butyl-4-methylphenol, triphenyl phosphite, and hypophosphite.

[0014] The present invention also provides a method for preparing the aqueous UV dual-curing dispersion of aluminum alloy as described above, comprising the following steps: Step 1: Synthesizing UV-curable prepolymer, S1: Mixing 2-4 parts of UV-curable diluent monomer, 0.5-1.5 parts of hydroxy acid monomer, 4-6 parts of isocyanate, 3-5 parts of polyol, 0.01-0.03 parts of catalyst, 0.003-0.005 parts of polymerization inhibitor, and 4-6 parts of solvent evenly, and stirring the mixture at 60-80°C until the mass concentration of isocyanate ions reaches 2-6%, to obtain the first reaction solution;

[0015] S2: Add 16-24 parts hydroxy acrylate, 2-3 parts solvent, 0.01-0.03 parts catalyst, and 0.002-0.005 parts polymerization inhibitor to the first reaction solution, and stir the reaction at 60-80℃ until the mass concentration of isocyanate ions is less than 0.6%; S3: When the temperature of the S2 solution drops below 40℃, add 0.5-1 parts neutralizing agent, stir the reaction for 30-45 minutes, and stop stirring when the temperature begins to drop at a uniform rate to obtain the UV-curable prepolymer; Second step: Synthesize the hydroxy acrylate prepolymer, S 1. Mix 20-35 parts of acrylate monomer, 10-30 parts of vinyl monomer, 12-20 parts of hydroxyacrylate monomer, 10-30 parts of solvent, and 0.07-0.3 parts of initiator until homogeneous. Then, take 1 / 3 of the above mixture, add 0.01-0.04 parts of polymerization inhibitor and 0.03-0.12 parts of antioxidant, and pour into a reaction flask. React at 60-90℃ for 0.5 hours. S2. Keeping the temperature constant, add the remaining 2 / 3 of the above mixture dropwise to the reaction flask at a uniform rate over 1-1.5 hours. S3. Continue the dropwise addition from the previous step... After the addition is complete, keep the temperature constant, mix 1-5 parts of acrylic monomer, 5-25 parts of solvent and 0.03-0.33 parts of initiator evenly, and add it dropwise to the reaction flask at a uniform rate over 10-20 minutes. React at 60-90℃ for 2-3 hours; S4: When the temperature of the solution in S3 drops below 40℃, add 1-10 parts of neutralizing agent, stir the reaction for 30-45 minutes, and stop stirring when the temperature begins to drop uniformly to obtain the hydroxyl acrylic acid prepolymer; Third step: S1: Combine the UV-curable prepolymer synthesized in the first step with the prepolymer synthesized in the second step. The hydroxyl acrylic acid prepolymer was mixed at a solid component ratio of 1.5:1-2.5:1 and stirred for 30 minutes at a speed of 600-800 r / min and room temperature. S2: The speed was adjusted to 1000-1200 r / min, and 60% deionized water was added at once and dispersed for 30-50 minutes. S3: The dispersion obtained in S2 was poured into a rotary evaporator and evaporated at 40-60℃ and -0.1 MPa for 1-1.5 h. The solid content was adjusted to 40% with deionized water to obtain an aqueous UV dual-curing dispersion for aluminum alloy.

[0016] Optionally, in the third step, the UV-curable prepolymer synthesized in the first step and the hydroxyl acrylic acid prepolymer synthesized in the second step are mixed at a solid component ratio of 2:1.

[0017] The present invention also provides an application of the aqueous UV dual-curing dispersion of aluminum alloy as described above in automobiles, mobile phones and home appliances.

[0018] The beneficial effects of this invention are as follows:

[0019] This invention employs a novel synthesis process. First, a hydroxyacrylic acid prepolymer is synthesized separately, then mixed with a UV prepolymer, and finally dispersed and emulsified. This process introduces a high molecular weight hydroxyacrylic acid (hydroxypropyl) dispersion into the product, allowing the resin to form a film with certain properties before UV curing, even after the addition of the curing agent. Simultaneously, the introduction of the high molecular weight hydroxypropyl dispersion reduces the shrinkage rate of the paint film, thereby improving adhesion.

[0020] Furthermore, since the paint film has already formed and surface-dried before UV curing, but has not yet undergone UV curing, it possesses good flexibility. Therefore, the substrate can be processed, stamped, or cast without damaging the paint film. After the part is fully formed, it is then cured using a UV machine. This simplifies the downstream spraying process, improves spraying efficiency and yield. In addition, painting before the part is formed results in a more uniform paint film thickness and better adhesion. The addition of high molecular weight hydroxypropyl dispersion reduces paint film shrinkage and improves adhesion. Finally, after UV curing, the cross-linking density of the paint film is further increased, thereby improving the hardness and solvent resistance of the paint film.

[0021] Meanwhile, because the mixing occurs during the prepolymer stage, followed by dispersion and emulsification, the product compatibility is improved, thus enhancing its stability. Furthermore, in the production of hydroxyl acrylic acid prepolymers, the acrylate monomers are polymerized first, and the acrylic monomers are added dropwise at the end. This ensures that the hydrophilic groups of the resin are on the outermost layer, encapsulating the lipophilic portion, further improving product stability.

[0022] Furthermore, since the paint film is finally UV cured, the small molecule monomers remaining in the hydroxy acrylic acid can undergo cross-linking reactions, which not only improves the density of the paint film, but also removes the small molecule monomers, thereby improving the paint film's solvent resistance, water resistance and other properties.

[0023] The product of this invention can be widely used in automobiles, mobile phones, and high-end home appliances. Detailed Implementation

[0024] The present invention will now be described in further detail with reference to specific embodiments. The embodiments of the present invention are given for the purpose of illustration and description, and are not intended to be exhaustive or to limit the invention to the disclosed forms. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described to better illustrate the principles and practical application of the invention, and to enable those skilled in the art to understand the invention and design various embodiments with various modifications suitable for a particular purpose.

[0025] The aqueous UV dual-curing dispersion for aluminum alloys according to the present invention comprises 26-33% UV-curing prepolymer, 11-17% hydroxy acrylic prepolymer and 55-60% water. The UV-curable prepolymer comprises the following components in parts by weight: 2-4 parts UV-curable diluent monomer, 0.5-1.5 parts hydroxy acid monomer, 4-6 parts isocyanate, 3-5 parts polyol, 0.02-0.06 parts catalyst, 0.005-0.01 parts polymerization inhibitor, 6-9 parts solvent, 16-24 parts hydroxy acrylate, and 0.5-1 parts neutralizer; the hydroxy acrylic acid prepolymer comprises the following components in parts by weight: 1-5 parts acrylic monomer, 20-35 parts acrylate monomer, 10-30 parts vinyl monomer, 12-20 parts hydroxy acrylic monomer, 1-10 parts neutralizer, 0.1-0.4 parts initiator, 0.01-0.04 parts polymerization inhibitor, 0.03-0.12 parts antioxidant, and 15-35 parts solvent.

[0026] In the aqueous UV dual-curing dispersion for aluminum alloys according to the present invention, the water content of the UV-curing diluent monomer, hydroxy acid monomer, isocyanate, polyol, catalyst, polymerization inhibitor, solvent, hydroxy acrylate, and neutralizer is all less than 500 ppm. The UV-curing diluent monomer may be at least one selected from 1,6-hexanediol diacrylate (HDDA), dipropylene glycol diacrylate (DPGDA), tripropylene glycol diacrylate (TPGDA), and trimethylolpropane triacrylate (TMPTA). The hydroxy acid monomer may be at least one selected from 2,2-dimethylolpropionic acid (DMPA), dimethylolbutyric acid (DMBA), and hydroxyethylsulfonic acid. The isocyanate may be at least one of isoflurane diisocyanate (IPDI), hexamethylene diisocyanate (HDI), diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), hexamethylene diisocyanate trimer, and 4,4'-dicyclohexylmethane diisocyanate (HMDI); the polyol may be at least one of silicon-containing polyol, polyether polyol, polyester polyol, caprolactone polyol, and polycarbonate polyol. The catalyst may be at least one of pentamethyldiethylenetriamine, dibutyltin dilaurate, organobismuth, solid amine, N-methylmorpholine, and N,N'-diethylpiperazine; the polymerization inhibitor may be at least one of p-hydroxyanisole, hydroquinone, and 2,5-dimethylhydroquinone; the solvent may be at least one of acetone, butanone, ethyl acetate, and butyl acetate; the hydroxyacrylate may be at least one of pentaerythritol pentaacrylate, pentaerythritol triacrylate, butyl hydroxyacrylate, and ethyl hydroxyacrylate; the neutralizing agent may be at least one of triethylamine, N,N-dimethylethanolamine, ammonia, sodium hydroxide, and potassium hydroxide. The acrylic monomer may be at least one of acrylic acid and methacrylic acid; the acrylate monomer may be at least one of butyl acrylate, methyl methacrylate, and methyl acrylate; the vinyl monomer may be at least one of styrene and epoxy acrylate; and the hydroxyacrylate monomer may be at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, and hydroxyethyl methacrylate. The initiator may be at least one of di-tert-butyl peroxide, di-tert-pentyl peroxide, benzoyl peroxide (BPO), azobisisobutyronitrile (AIBN), and azobisisoheptanenitrile; the antioxidant may be at least one of phenothiazine, 2,6-di-tert-butyl-4-methylphenol, triphenyl phosphite, and hypophosphite.

[0027] This invention achieves a UV dual-curing system by mixing hydroxyl acrylic prepolymer in the UV prepolymer stage. Because both systems are dissolved in the same solvent during the prepolymer stage, the mixing is more homogeneous, forming a single phase, before dispersion and emulsification. This not only ensures good product stability but also gives the final paint film excellent hardness, adhesion, and solvent resistance. Furthermore, its unique surface-drying properties before UV curing allow aluminum alloy materials to be painted before processing, thus improving downstream production processes and protecting the substrate from damage during processing, resulting in a superior appearance for the final parts and expanding the application range of aluminum alloy materials.

[0028] The preparation method of the aqueous UV dual-curing dispersion of aluminum alloy according to the present invention includes the following steps: Step 1: Synthesizing a UV-curable prepolymer, S1: Mixing 2-4 parts of UV-curable diluent monomer, 0.5-1.5 parts of hydroxy acid monomer, 4-6 parts of isocyanate, 3-5 parts of polyol, 0.01-0.03 parts of catalyst, 0.003-0.005 parts of polymerization inhibitor, and 4-6 parts of solvent evenly, and stirring at 60-80°C until the mass concentration of isocyanate ions reaches 2-6%, to obtain the first reaction solution; S2: Adding 16-24 parts of hydroxy acrylate, 2-3 parts of solvent, and 0.0 Step 1: Add 1-0.03 parts catalyst and 0.002-0.005 parts polymerization inhibitor, and stir at 60-80℃ until the mass concentration of isocyanate ions is less than 0.6%; Step 2: When the temperature of the solution in Step 2 drops below 40℃, add 0.5-1 parts neutralizing agent, stir for 30-45 minutes, and stop stirring when the temperature begins to drop at a uniform rate to obtain the UV-curable prepolymer; Step 3: Synthesize the hydroxyacrylic acid prepolymer, Step 4: Add 20-35 parts acrylate monomer, 10-30 parts vinyl monomer, 12-20 parts hydroxyacrylic acid monomer, 10-30 parts solvent, and 0.07-0.3 parts initiator. Mix thoroughly, then take 1 / 3 of the above mixture, 0.01-0.04 parts of polymerization inhibitor, and 0.03-0.12 parts of antioxidant, and pour them into a reaction flask. React at 60-90℃ for 0.5 hours; S2: Keep the temperature unchanged from the previous step, then add the remaining 2 / 3 of the above mixture dropwise to the reaction flask at a uniform rate over 1-1.5 hours; S3: After the dropwise addition is completed in the previous step, keep the temperature unchanged, mix 1-5 parts of acrylic monomer, 5-25 parts of solvent, and 0.03-0.33 parts of initiator thoroughly, and then add them dropwise to the reaction flask at a uniform rate over 10-20 minutes. React at 60-90℃ for 2-3 hours; S4: When the solvent in S3... When the liquid temperature drops below 40℃, add 1-10 parts of neutralizing agent and stir for 30-45 minutes. When the temperature begins to drop at a uniform rate, stop stirring to obtain the hydroxy acrylic acid prepolymer. Step 3: S1: Mix the UV-curable prepolymer synthesized in step 1 and the hydroxy acrylic acid prepolymer synthesized in step 2 at a solid component ratio of 1.5:1-2.5:1 and stir for 30 minutes at room temperature with a speed of 600-800 r / min. S2: Adjust the speed to 1000-1200 r / min and add 60% deionized water (the mass of the mixed prepolymer accounts for 40%) at once, and disperse for 30-50 minutes.

[0029] S3: Pour the dispersion obtained in S2 into a rotary evaporator and evaporate it at 40-60℃ and -0.1Mpa for 1-1.5h. Adjust the solid content to 40% with deionized water to obtain an aqueous UV dual-curing dispersion for aluminum alloy.

[0030] In the third step, the UV-curable prepolymer synthesized in the first step and the hydroxyacrylic acid prepolymer synthesized in the second step are mixed at a solids ratio of 1.5:1 to 2.5:1, wherein the solids are components from which the solvent has been removed. In one embodiment, the UV-curable prepolymer synthesized in the first step and the hydroxyacrylic acid prepolymer synthesized in the second step are mixed at a solids ratio of 2:1.

[0031] The aqueous UV dual-curing dispersion of aluminum alloys according to the present invention can be applied to automobiles, mobile phones, and home appliances. The preparation method of the present invention consists of three reaction steps: In the first step, steps S1 and S2 are controlled by reaction time and temperature, and the reaction time and endpoint of this step are determined by detecting the mass concentration of isocyanate ions; step S3 is controlled by reaction time and temperature, and the endpoint of this step is reached when the temperature begins to decrease at a uniform rate. In the second step, steps S1, S2, and S3 are controlled by reaction time and temperature, and step S4 is also controlled by reaction time and temperature, with the endpoint of this step being reached when the temperature begins to decrease at a uniform rate. In the third step, steps S1 and S2 are controlled by reaction temperature, time, and dispersion speed; step S3 is controlled by reaction temperature, time, and solid content.

[0032] This invention controls the production process by adjusting the reaction temperature, reaction time, isocyanate ion concentration, and dispersion speed, thereby synthesizing an aqueous UV dual-curing dispersion for aluminum alloys. This dispersion not only has high hardness and gloss but also good adhesion and solvent resistance. Furthermore, since it is already surface-dried before UV curing, it can undergo a series of processing steps, which can greatly improve the manufacturing difficulty of downstream products, improve the production processes of downstream customers, and reduce production costs.

[0033] The following specific embodiments illustrate the aqueous UV dual-curing dispersion for aluminum alloys of the present invention, its preparation method, and its application.

[0034] Main raw materials and equipment used: Unless otherwise specified, the raw materials and equipment used in each embodiment and comparative example are the same; materials without specific models or types are sourced from common, same models purchased from the market, and no specific restrictions are imposed.

[0035] Example 1

[0036] The method for preparing water-based UV dual-curing dispersions for aluminum alloys provided in this embodiment includes the following steps:

[0037] Step 1: S1: Add 3 parts HDDA, 1 part DMPA, 5 parts HMDI, 2 parts silicon-containing polyol, 2 parts polyether polyol, 0.02 parts organic bismuth, 0.004 parts hydroquinone, and 5 parts methyl ethyl ketone to a four-necked flask. Stir at 75°C for 3 hours until the mass concentration of isocyanate ions reaches 4.46%, obtaining the first reaction solution; S2: Add 20 parts pentaerythritol triacrylate, 2 parts methyl ethyl ketone, 0.025 parts organic bismuth, and 0.003 parts hydroquinone to the first reaction solution. Stir at 75°C for 4 hours until the mass concentration of isocyanate ions is less than 0.6%; S3: When the temperature of the S2 solution drops below 40°C, add 0.83 parts triethylamine. Stir for 30 minutes. When the temperature begins to decrease uniformly, stop stirring to obtain the UV-curable prepolymer; the solid content of the obtained UV-curable prepolymer is 82.88%. Solid content refers to the proportion of solid components.

[0038] Step 2: S1: Mix 10 parts butyl acrylate, 15 parts methyl methacrylate, 5 parts methyl acrylate, 15 parts styrene, 12 parts hydroxyethyl acrylate, 20 parts butanone, and 0.1 parts AIBN thoroughly. Then, pour 1 / 3 of the mixture into a four-necked flask. Next, add 0.02 parts hydroquinone and 0.07 parts triphenyl phosphite to the four-necked flask and react at 65°C for 0.5 hours. S2: Keeping the temperature constant, add the remaining 2 / 3 of the mixture dropwise to the reaction flask over 1 hour at a uniform rate. S3: After the dropwise addition is complete, keeping the temperature constant, mix 3 parts acrylic acid, 5 parts butanone, and 0.05 parts AIBN thoroughly and add the mixture dropwise to the reaction flask over 15 minutes at a uniform rate. React at 65°C for 3 hours. S4: When the temperature of the S3 solution drops below 40°C, add 4.6 parts of triethylamine, stir and react for 30 minutes. When the temperature begins to drop at a uniform rate, stop stirring and react to obtain the hydroxyacrylic acid prepolymer. The solid content of the obtained hydroxyacrylic acid prepolymer is 72.17%.

[0039] Step 3: S1: Mix 2.4 parts of the first-step UV-cured prepolymer (containing approximately 2 parts of solids) and 1.37 parts of the second-step hydroxyl acrylic prepolymer (containing approximately 1 part of solids) in a dispersion tank and stir for 30 minutes at 600 rpm and room temperature (25°C). S2: Adjust the stirring speed to 1200 rpm and add 5.655 parts of deionized water all at once, then disperse for 45 minutes. S3: Pour the dispersion obtained in S2 into a rotary evaporator and evaporate for 1 hour at 55°C and -0.1 MPa. Adjust the solid content to 40% with deionized water to obtain an aqueous UV dual-curing dispersion for aluminum alloy.

[0040] Example 2

[0041] The method for preparing water-based UV dual-curing dispersions for aluminum alloys provided in this embodiment includes the following steps:

[0042] Step 1: S1: Add 3 parts TMPTA, 1 part DMPA, 4.23 parts IPDI, 2 parts silicon-containing polyol, 2 parts polycarbonate polyol, 0.02 parts dibutyltin dilaurate, 0.004 parts p-hydroxyanisole, and 5 parts butanone to a four-necked flask. Stir and react at 75°C for 3 hours until the mass concentration of isocyanate ions reaches 4.5%, obtaining the first reaction solution; S2: Add 6 parts pentaerythritol triacrylate and 18 parts dipentaerythritol pentaacrylate to the first reaction solution. Acrylic ester, 4 parts methyl ethyl ketone, 0.025 parts dibutyltin dilaurate, and 0.003 parts p-hydroxyanisole were stirred at 75°C for 5 hours until the mass concentration of isocyanate ions was less than 0.6%; S3: When the temperature of the S2 solution dropped below 40°C, 0.83 parts triethylamine were added, and the mixture was stirred for 30 minutes. When the temperature began to decrease at a uniform rate, the stirring reaction was stopped to obtain a UV-curable prepolymer; the solid content of the obtained UV-curable prepolymer was 80.48%.

[0043] Step 2: S1: Mix 15 parts butyl acrylate, 15 parts methyl methacrylate, 10 parts styrene, 5 parts epoxy acrylate, 13 parts hydroxypropyl acrylate, 20 parts methyl ethyl ketone (MEK), and 0.1 parts AIBN thoroughly. Then, pour 1 / 3 of the mixture into a four-necked flask. Next, add 0.02 parts p-hydroxyanisole and 0.07 parts triphenyl phosphite to the four-necked flask. React at 65°C for 0.5 hours. S2: Keeping the temperature constant, add the remaining 2 / 3 of the mixture dropwise to the reaction flask over 1.2 hours at a uniform rate. S3: After the dropwise addition is complete, keeping the temperature constant, mix 3 parts acrylic acid, 5 parts MEK, and 0.05 parts AIBN thoroughly. Add this mixture dropwise to the reaction flask over 20 minutes at a uniform rate. React at 65°C for 3 hours. S4: When the temperature of the S3 solution drops below 40°C, add 4.6 parts of triethylamine, stir and react for 30 minutes. When the temperature begins to drop at a uniform rate, stop stirring and react to obtain the hydroxyacrylic acid prepolymer. The solid content of the obtained hydroxyacrylic acid prepolymer is 72.48%.

[0044] Step 3: S1: Mix 2.49 parts of the first-step UV-cured prepolymer (containing approximately 2 parts of solids) and 1.38 parts of the second-step hydroxyl acrylic prepolymer (containing approximately 1 part of solids) in a dispersion tank and stir for 30 minutes at 600 rpm and room temperature (25°C). S2: Adjust the stirring speed to 1200 rpm and add 5.685 parts of deionized water all at once, then disperse for 45 minutes. S3: Pour the dispersion obtained in S2 into a rotary evaporator and evaporate for 1 hour at 55°C and -0.1 MPa. Adjust the solid content to 40% with deionized water to obtain an aqueous UV dual-curing dispersion for aluminum alloy.

[0045] Example 3

[0046] The method for preparing water-based UV dual-curing dispersions for aluminum alloys provided in this embodiment includes the following steps:

[0047] Step 1: S1: Add 3 parts TPGDA, 1.5 parts DMBA, 5 parts HMDI, 3 parts silicon-containing polyol, 2 parts polyester polyol, 0.02 parts dibutyltin dilaurate, 0.004 parts 2,5-dimethylhydroquinone, and 5 parts butyl acetate to a four-necked flask. Stir and react at 80°C for 2 hours until the mass concentration of isocyanate ions reaches 2.8%, obtaining the first reaction solution; S2: Add 18 parts pentaerythritol triacrylate, 2 0.025 parts of butyl acetate, 0.003 parts of dibutyltin dilaurate, and 0.003 parts of 2,5-dimethylhydroquinone were stirred and reacted at 80°C for 4 hours until the mass concentration of isocyanate ions was less than 0.6%; S3: When the temperature of the solution in S2 dropped below 40°C, 1 part of triethylamine was added, and the mixture was stirred and reacted for 30 minutes. When the temperature began to drop at a uniform rate, the stirring reaction was stopped to obtain the UV-curable prepolymer; the solid content of the obtained UV-curable prepolymer was 82.74%.

[0048] Step 2: S1: Mix 15 parts butyl acrylate, 5 parts methyl methacrylate, 10 parts methyl acrylate, 5 parts styrene, 10 parts epoxy acrylate, 7 parts hydroxypropyl acrylate, 6 parts hydroxyethyl acrylate, 25 parts butyl acetate, and 0.12 parts BPO thoroughly. Then, pour 1 / 3 of the mixture into a four-necked flask. Next, add 0.02 parts 2,5-dimethylhydroquinone and 0.07 parts phenothiazine to the four-necked flask. React at 85°C for 0.5 hours. S2: Keeping the temperature constant, add the remaining 2 / 3 of the mixture dropwise to the reaction flask over 1.5 hours at a uniform rate. S3: After the addition is complete, keeping the temperature constant, mix 2 parts methacrylic acid, 5 parts butyl acetate, and 0.04 parts BPO thoroughly. Add this mixture dropwise to the reaction flask over 20 minutes at a uniform rate. React at 85°C for 2.5 hours. S4: When the temperature of the S3 solution drops below 40°C, add 2.59 parts of triethylamine, stir and react for 30 minutes. When the temperature begins to drop at a uniform rate, stop stirring and react to obtain the hydroxyacrylic acid prepolymer. The solid content of the obtained hydroxyacrylic acid prepolymer is 67.69%.

[0049] Step 3: S1: Mix 2.42 parts of the first step UV-cured prepolymer (containing approximately 2 parts solids) and 1.5 parts of the second step hydroxyl acrylic acid prepolymer (containing approximately 1 part solids) and pour them into a dispersion tank. Stir for 30 minutes at 700 rpm and room temperature (25°C). S2: Adjust the speed to 1200 rpm and add 5.88 parts of deionized water all at once. Disperse for 45 minutes. S3: Pour the dispersion obtained in S2 into a rotary evaporator and evaporate for 1 hour at 60°C and -0.1 MPa. Adjust the solid content to 40% with deionized water to obtain an aqueous UV dual-curing dispersion for aluminum alloy.

[0050] Example 4

[0051] The method for preparing water-based UV dual-curing dispersions for aluminum alloys provided in this embodiment includes the following steps:

[0052] Step 1: S1: Add 2.5 parts TPGDA, 1.5 parts DMBA, 4 parts HDI, 3 parts silicon-containing polyol, 2 parts caprolactone polyol, 0.03 parts organic bismuth, 0.004 parts hydroquinone, and 6 parts ethyl acetate to a four-necked flask. Stir at 70°C for 3 hours until the mass concentration of isocyanate ions reaches 4.94%, obtaining the first reaction solution; S2: Add 10 parts pentaerythritol triacrylate, 10 parts dipentaerythritol pentaacrylate, 2 parts ethyl acetate, 0.03 parts organic bismuth, and 0.003 parts hydroquinone to the first reaction solution. Stir at 70°C for 5 hours until the mass concentration of isocyanate ions is less than 0.6%; S3: When the temperature of the S2 solution drops below 40°C, add 0.96 parts N,N-dimethylethanolamine. Stir for 40 minutes. When the temperature begins to decrease uniformly, stop stirring to obtain the UV-curable prepolymer; the solid content of the obtained UV-curable prepolymer is 80.96%.

[0053] Step 2: S1: Mix 10 parts butyl acrylate, 10 parts methyl methacrylate, 10 parts methyl acrylate, 9 parts styrene, 6 parts epoxy acrylate, 13 parts hydroxyethyl methacrylate, 25 parts ethyl acetate, and 0.11 parts AIBN thoroughly. Then, pour 1 / 3 of the mixture into a four-necked flask. Add 0.02 parts hydroquinone and 0.1 parts phenothiazine to the four-necked flask and react at 70°C for 0.5 hours. S2: Keeping the temperature constant, add the remaining 2 / 3 of the mixture dropwise to the reaction flask over 1.5 hours at a uniform rate. S3: After the dropwise addition is complete, keeping the temperature constant, mix 1.5 parts methacrylic acid, 1.5 parts acrylic acid, 6 parts butyl acetate, and 0.09 parts AIBN thoroughly and add the mixture dropwise to the reaction flask over 15 minutes at a uniform rate. React at 70°C for 2 hours. S4: When the temperature of the solution in S3 drops below 40°C, add 3.62 parts of N,N-dimethylethanolamine and stir for 40 minutes. When the temperature begins to drop at a uniform rate, stop stirring to obtain the hydroxyacrylic acid prepolymer. The solid content of the obtained hydroxyacrylic acid prepolymer is 67.69%.

[0054] Step 3: S1: Mix 2.48 parts of the first-step UV-cured prepolymer (containing approximately 2 parts of solids) and 1.49 parts of the second-step hydroxyl acrylic prepolymer (containing approximately 1 part of solids) and pour them into a dispersion tank. Stir for 30 minutes at 800 rpm and room temperature (25°C). S2: Adjust the speed to 1200 rpm and add 5.955 parts of deionized water all at once. Disperse for 45 minutes. S3: Pour the dispersion obtained in S2 into a rotary evaporator and evaporate for 1.2 hours at 55°C and -0.1 MPa. Adjust the solid content to 40% with deionized water to obtain an aqueous UV dual-cured dispersion for aluminum alloy.

[0055] Performance testing

[0056] The coatings obtained in the above embodiments were subjected to performance tests in accordance with relevant national and industry standards. The test formulations are shown in the table below:

[0057]

[0058] After preparing the paint according to the above formula, take an aluminum alloy plate and spray it directly without sanding. After spraying, bake at 70℃ for 30 minutes. Then, divide all the baked plates into two parts. One part is directly subjected to impact, toughness, and surface dryness tests; the other part is passed through a UV machine with an energy of 800-1000 mJ / cm². 2 Then, a series of tests were conducted.

[0059] The impact test method is as follows: the test shall be conducted in accordance with GB / T 1732-2020.

[0060] The toughness test method is as follows: bend the aluminum alloy sheet 90 degrees. ° Then rinse the bent part with hot water at 90-100℃ for 1 minute and check if there are any cracks at the bend.

[0061] The surface dryness test method is as follows: Take a board that has been baked but has not been UV tested, apply a layer of blue PET film to the surface of the paint film, press a 1KG weight on the film, and then put the board and the weight into a 70℃ oven and bake for 2 hours. Take out the board, remove the weight, remove the PET film, and observe whether there is any change in the paint film.

[0062] The performance test results of the uncured samples after baking are shown in Table 1. The performance test results of the UV-cured samples are shown in Table 2.

[0063] Table 1 Performance test results of uncured samples

[0064] Test Project Impact (kg.cm) surface dry toughness Example 1 50 No change in paint film No cracks Example 2 50 No change in paint film No cracks Example 3 50 No change in paint film No cracks Example 4 50 No change in paint film No cracks

[0065] Table 2 Performance test results of UV-cured samples

[0066]

[0067] The test results in Table 1 show that the paint film passed impact and bending tests after baking with the curing agent. Because this invention incorporates high-molecular-weight hydroxy acrylic acid, the paint film surface is already dry and possesses certain properties after baking with the curing agent. The fact that the paint film passed impact and bending tests indicates that it has good toughness and can undergo a series of processing steps without damage. Furthermore, the paint film showed no change after being laminated with a PET film, pressurized, and baked at a certain temperature. This characteristic allows for the application of a protective film to the paint film during subsequent substrate processing, preventing damage and improving the final appearance of the parts, thus increasing the yield rate.

[0068] The test results in Table 2 show that after UV curing, the paint film exhibits good adhesion, hardness, gloss, solvent resistance, water resistance, immersion resistance, and acid and alkali resistance. The introduction of hydroxyl groups into the paint film reduces curing shrinkage; the introduction of organosilicon groups also increases the surface polarity of the paint film, resulting in excellent adhesion after UV curing. Furthermore, the presence of numerous double bonds in the paint film leads to a high cross-linking density after curing, resulting in high hardness and gloss, good solvent and acid / alkali resistance, and excellent resistance to boiling water and long-term immersion due to the film's high density and toughness.

[0069] Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art and related fields based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described and explained in the present invention, unless otherwise specified or limited, shall be implemented according to conventional means in the art.

Claims

1. A method for preparing a waterborne UV dual-cure dispersion for aluminum alloys, characterized in that, Comprising the following steps: First step: synthesis of UV curing prepolymer: S1, 2-4 parts of UV curing diluent monomer, 0.5-1.5 parts of hydroxyl acid monomer, 4-6 parts of isocyanate, 3-5 parts of polyol, 0.01-0.03 parts of catalyst, 0.003-0.005 parts of polymerization inhibitor, 4-6 parts of solvent are mixed uniformly, and stirred at 60-80℃ until the mass concentration of isocyanate ion reaches 2-6%, to obtain a first reaction solution; S2, 16-24 parts of hydroxy acrylate, 2-3 parts of solvent, 0.01-0.03 parts of catalyst, 0.002-0.005 parts of polymerization inhibitor are added to the first reaction solution, and stirred at 60-80℃ until the mass concentration of isocyanate ion is less than 0.6%; S3: when the solution temperature of S2 drops below 40℃, 0.5-1 parts of neutralizing agent are added, and stirred for 30-45 minutes, when the temperature starts to drop uniformly, stop stirring, to obtain a UV curing prepolymer; Second step: synthesis of hydroxyl acrylate prepolymer: S1, 20-35 parts of acrylate monomer, 10-30 parts of vinyl monomer, 12-20 parts of hydroxyl acrylate monomer, 10-30 parts of solvent, 0.07-0.3 parts of initiator are mixed uniformly, then 1 / 3 of the above mixture, 0.01-0.04 parts of polymerization inhibitor, 0.03-0.12 parts of antioxidant are taken, poured into a reaction bottle, and reacted at 60-90℃ for 0.5 hours; S2, keep the temperature unchanged, then add the remaining 2 / 3 of the above mixture into the reaction bottle at a uniform speed within 1-1.5 hours; S3: after the completion of the above step, the temperature is kept unchanged, 1-5 parts of acrylate monomer, 5-25 parts of solvent and 0.03-0.33 parts of initiator are mixed uniformly, and then added into the reaction bottle at a uniform speed within 10-20 minutes, and reacted at 60-90℃ for 2-3 hours; S4: when the solution temperature of S3 drops below 40℃, 1-10 parts of neutralizing agent are added, and stirred for 30-45 minutes, when the temperature starts to drop uniformly, stop stirring, to obtain a hydroxyl acrylate prepolymer; Third step: S1, the UV curing prepolymer synthesized in the first step and the hydroxyl acrylate prepolymer synthesized in the second step are mixed at a solid component ratio of 1.5:1-2.5:1, stirred at a rotation speed of 600-800r / min at room temperature for 30 minutes; S2, adjust the rotation speed to 1000-1200r / min, add 60% deionized water at one time, and disperse for 30-50 minutes; S3, pour the dispersion obtained in S2 into a rotary evaporator, and evaporate at 40-60℃ and -0.1Mpa for 1-1.5h, and adjust the solid content to 40% with deionized water to obtain a water-based UV double-curing dispersion for aluminum alloy; The UV curing diluent monomer is at least one of 1,6-hexanediol diacrylate (HDDA), dipropylene glycol diacrylate (DPGDA), tripropylene glycol diacrylate (TPGDA), and trimethylolpropane triacrylate (TMPTA); The hydroxy acrylate is at least one of dipentaerythritol pentaacrylate, pentaerythritol triacrylate, hydroxy butyl acrylate, hydroxy ethyl acrylate; The hydroxy acrylate is at least one of dipentaerythritol pentaacrylate, pentaerythritol triacrylate, hydroxy butyl acrylate, hydroxy ethyl acrylate; The polyol is at least one of a silicon-containing polyol and a polyether polyol, a polyester polyol, a caprolactone polyol, a polycarbon polyol.

2. The method of making a waterborne UV dual-cure dispersion for aluminum alloys according to claim 1, characterized in that, The UV curing diluent monomer, the hydroxy acid monomer, the isocyanate, the polyol, the catalyst, the polymerization inhibitor, the solvent, the hydroxy acrylate, and the neutralizing agent each have a water content of less than 500 ppm.

3. The method of making a waterborne UV dual-cure dispersion for aluminum alloys according to claim 1, characterized in that, The hydroxy acid monomer is at least one of 2,2-dimethylol propionic acid (DMPA), dimethylol butanoic acid (DMBA), and isethionic acid.

4. The method of making a waterborne UV dual-cure dispersion for aluminum alloys according to claim 1, characterized in that, The isocyanate is at least one of isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), hexamethylene diisocyanate trimer, and 4,4'-dicyclohexylmethane diisocyanate (HMDI).

5. The method of making a waterborne UV dual-cure dispersion for aluminum alloys according to claim 1, wherein, The catalyst is at least one of pentamethyldiethylenetriamine, dibutyltin dilaurate, organic bismuth, stannanol, N-methylmorpholine, and N,N'-diethylpiperazine; the polymerization inhibitor is at least one of p-hydroxyanisole, hydroquinone, and 2,5-dimethylhydroquinone; the solvent is at least one of acetone, butanone, ethyl acetate, and butyl acetate; and the neutralizing agent is at least one of triethylamine, N,N-dimethylethanolamine, aqueous ammonia, sodium hydroxide, and potassium hydroxide.

6. The method of making a waterborne UV dual-cure dispersion for aluminum alloys according to claim 1, wherein, The acrylic acid monomer is at least one of acrylic acid and methacrylic acid; the acrylic ester monomer is at least one of butyl acrylate, methyl methacrylate, and methyl acrylate; and the vinyl monomer is at least one of styrene and epoxy acrylate.

7. The method of making a waterborne UV dual-cure dispersion for aluminum alloys according to claim 1, wherein, The initiator is at least one of di-t-butyl peroxide, di-t-amyl peroxide, benzoyl peroxide (BPO), azobisisobutyronitrile (AIBN), and azobisisoheptanitrile; and the antioxidant is at least one of phenothiazine, 2,6-di-t-butyl-4-methylphenol, triphenyl phosphite, and hypophosphorous acid.

8. The water-based UV double-curing dispersion for aluminum alloys obtained by the preparation method according to any one of claims 1-7.

9. The water-based UV double-curing dispersion for aluminum alloys according to claim 8 in the application of automobiles, mobile phones, and home appliances.

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