A waterproof UV-cured coating and a preparation method thereof

Abstract

The application discloses a waterproof UV curing paint and a preparation method thereof, wherein trimethylolpropane triacrylate is used as an active diluent, 2-hydroxy-2-methyl-1-phenylpropanone is used as a photoinitiator, polyurethane acrylate and modified fillers are polymerized in a UV curing process of the paint, and a high-crosslinking waterproof UV curing coating is prepared. A perfluorocarbon chain structure and a hydrogen bond network are introduced into a polyurethane acrylate molecular chain, a molecular-level smooth super-hydrophobic layer is formed on the surface of the coating, and the molecular-level smooth super-hydrophobic layer can effectively block the penetration of water molecules. The modified fillers with microcrystalline wax as a core and silicon dioxide as a shell are added, the wear resistance and scratch resistance of the coating can be significantly improved, and meanwhile, the microcrystalline wax and the coating with low surface energy cooperatively construct a super-hydrophobic structure, so that the waterproof performance of the UV curing paint is improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of UV curing coating preparation, in particular to a waterproof UV curing coating and a preparation method thereof. BACKGROUND

[0002] UV coating has the advantages of energy saving, no volatile organic compounds, fast curing speed, bright color and the like, and is a research hotspot in the field of environment-friendly materials. The development history of UV coating can be traced back to the 1930s, when scientists first observed that ultraviolet light can initiate the polymerization of certain materials, laying the foundation for UV curing technology. With the rapid development of UV curing technology, UV curing coating has also developed rapidly and is gradually applied to the fields of wood, textiles, metal, paper, plastic and automobile spraying. Compared with the traditional thermal curing process, UV coating can realize second-level curing under ultraviolet irradiation, and only the radiation energy of the initiator is needed in the curing process, without the need to heat the substrate or evaporate the solvent, so that the energy consumption is low. The purpose of the application is to prepare a waterproof UV curing coating with high mechanical properties. SUMMARY

[0003] The application provides a waterproof UV curing coating and a preparation method thereof, and solves the problems of weak waterproof performance and poor mechanical properties of the UV curing coating at the present stage.

[0004] The purpose of the application can be achieved by the following technical scheme.

[0005] A preparation method of a waterproof UV curing coating, specifically comprising the following steps:

[0006] The polyurethane acrylate and the modified filler are uniformly mixed, trimethylolpropane triacrylate and 2-hydroxy-2-methyl-1-phenylpropanone are added under the condition that the rotating speed is 70-80 r / min, and after uniform stirring for 30 min, ultrasonic treatment is carried out under the condition that the temperature is 20-25 DEG C and the frequency is 30-40 kHz for 4 h, so that the waterproof UV curing coating is prepared.

[0007] Further, the weight ratio of the polyurethane acrylate, the modified filler, the trimethylolpropane triacrylate and the 2-hydroxy-2-methyl-1-phenylpropanone is 100-120:20-30:60-80:4-6.

[0008] Further, the polyurethane acrylate is prepared by the following steps:

[0009] Step A1: Mix 1H,1H,2H,2H-perfluorodecyl mercaptan, acrylonitrile, benzoin dimethyl ether and tetrahydrofuran evenly, and react for 1-2 minutes under ultraviolet irradiation at a speed of 110-130 r / min and a temperature of 20-25℃ to obtain intermediate 1. Mix dicyandiamide, intermediate 1, potassium hydroxide and dimethyl sulfoxide evenly, and react for 12-15 hours under nitrogen irradiation at a speed of 100-120 r / min and a temperature of 110-120℃. Filter, cool and crystallize to obtain intermediate 2.

[0010] Step A2: Mix itaconic acid, glycidyl methacrylate and N,N-dimethylformamide evenly, and stir with methylhydroquinone and triethylamine under nitrogen atmosphere at a speed of 120-130 r / min, a temperature of 90-110℃, and a stirring period of 6-8 h to obtain intermediate 3. Mix hexamethylene diisocyanate and N,N-dimethylformamide evenly, and stir with intermediate 2 and dibutyltin dilaurate under nitrogen atmosphere at a speed of 80-100 r / min, a temperature of 40-50℃, and a stirring period of 2-3 h. Raise the temperature to 60-70℃, add intermediate 3, and react for 4-6 h to obtain polyurethane primary polymer.

[0011] Step A3: Mix 1,6-hexanediol, polyurethane primary polymer, methyl hydroquinone, tetrahydrofuran, and dibutyltin dilaurate evenly. React for 5-7 hours at a rotation speed of 100-120 r / min, a temperature of 60-70℃, and under nitrogen purging. Add polydipentaerythritol pentaacrylate and react for 2-3 hours to obtain polyurethane acrylate.

[0012] Furthermore, in step A1, the molar ratio of 1H,1H,2H,2H-perfluorodecyl mercaptan to acrylonitrile is 1.1:1, the amount of benzoin dimethyl ether used is 3-5% of the mass of 1H,1H,2H,2H-perfluorodecyl mercaptan, and the ratio of dicyandiamide, intermediate 1, potassium hydroxide and dimethyl sulfoxide used is 0.15mol:0.16mol:2.66g:120mL.

[0013] Further, in step A2, the molar ratio of itaconic acid and glycidyl methacrylate is 1:1, the amount of methyl hydroquinone is 3-5% of the mass of itaconic acid, the amount of triethylamine is 4-8% of the mass of itaconic acid, the molar ratio of hexamethylene diisocyanate, intermediate 2 and intermediate 3 is 1.2:0.4:0.5, and the amount of dibutyltin dilaurate is 2-4% of the mass of hexamethylene diisocyanate.

[0014] Further, the molar ratio of 1,6-hexanediol, polyurethane prepolymer and polydi-pentaerythritol five acrylate in step A3 is 1:1.4:0.1, the amount of methyl hydroquinone is 1-3% of the mass of the polyurethane prepolymer, and the amount of dibutyltin dilaurate is 3-5% of the mass of the polyurethane prepolymer.

[0015] Further, the modified filler is prepared by the following steps:

[0016] Step B1: uniformly mix N-cocoalkyl-1,3-propanediamine and deionized water, stir at a speed of 100-110 r / min and a temperature of 70-80℃ for 10-20 min, add melted microcrystalline wax, emulsify for 0.5-1 h, prepare a dispersion, and prepare a microcrystalline wax emulsion by high-pressure homogenization and rapid cooling;

[0017] Step B2: stir the microcrystalline wax emulsion at a speed of 90-110 r / min and a temperature of 40-60℃, add ammonia water to adjust the pH to 9-11, add tetraethyl orthosilicate and anhydrous ethanol, and react for 10-12 h, then centrifuge, wash and dry to obtain a pretreated filler;

[0018] Step B3: disperse the pretreated filler in tetrahydrofuran, stir at a speed of 100-120 r / min, a temperature of 60-80℃ and a pH of 4-5, and add vinyltrimethoxysilane to react for 8-10 h to obtain a modified filler.

[0019] Further, the amount of N-cocoalkyl-1,3-propanediamine in step B1 is 6-8% of the mass of the microcrystalline wax.

[0020] Further, the amount of tetraethyl orthosilicate in step B2 is 15-20% of the mass of the microcrystalline wax emulsion.

[0021] Further, the amount of vinyltrimethoxysilane in step B3 is 3-5% of the mass of the pretreated filler.

[0022] The beneficial effects of the present application: trimethylolpropane triacrylate as an active diluent can adjust the viscosity of the UV curing system and participate in the photocuring reaction, and 2-hydroxy-2-methyl-1-phenylpropanone as a photoinitiator. In the UV curing process of the coating, the photoinitiator generates free radicals after absorbing ultraviolet rays, which promotes the polymerization of polyurethane acrylate, trimethylolpropane triacrylate and modified filler, and then triggers crosslinking reaction, generating a three-dimensional crosslinked structure of waterproof UV cured coating.

[0023] Polyurethane acrylate: the mercapto group on 1H, 1H, 2H, 2H-perfluorodecyl mercaptan reacts with the carbon-carbon double bond on acrylonitrile under the action of initiator and ultraviolet light irradiation to prepare intermediate 1, the amino group on dicyandiamide is deprotonated under alkaline conditions to form a nucleophilic amide anion, which attacks the cyano carbon atom of intermediate 1 to form a new C-N bond to generate intermediate, which then undergoes intramolecular cyclization and eliminates one molecule of ammonia to form a triazine ring structure to prepare intermediate 2. The ring-opening reaction of the carboxyl group on itaconic acid with the epoxy group on glycidyl methacrylate generates an ester group and a hydroxyl group to prepare intermediate 3. The isocyanate group on hexamethylene diisocyanate reacts with the amino group on intermediate 2 under the action of a catalyst, and the remaining isocyanate group reacts with the hydroxyl group on intermediate 3 to prepare a polyurethane prepolymer. 1,6-hexanediol acts as a chain extender, and the hydroxyl groups at both ends of the chain react with the isocyanate groups on the polyurethane prepolymer. After the reaction is complete, the remaining isocyanate groups react with the hydroxyl groups on polydi-pentaerythritol pentacrylate to prepare a polyurethane acrylate.

[0024] Modified filler: N-cocoyl-1,3-propanediamine as a cationic surfactant, the long-chain hydrophobic cocoyl group in the molecular structure is embedded in the microcrystalline wax droplets, and the cationic amino functional group contained therein faces the water phase to form a dense protective film, preventing small droplets from aggregating to prepare a microcrystalline wax emulsion. In an alkaline environment, tetraethyl orthosilicate is added to the microcrystalline wax emulsion, and the silanol molecules generated by the hydrolysis of tetraethyl orthosilicate are attracted by the positively charged amino groups through electrostatic attraction and form hydrogen bonds, promoting the nucleation and growth of silicon dioxide on the surface of the microcrystalline wax particles to obtain a pretreated filler. The Sn-OH on the pretreated filler condenses with the Si-OH on mercaptopropyltriethoxysilane to prepare a modified filler.

[0025] The perfluorocarbon chain structure introduced in the material will spontaneously migrate to the interface between the coating and the air before and during the UV coating curing due to the extremely low surface energy, so that the outermost layer of the coating is covered by a dense fluorocarbon chain, forming a molecular-level smooth super-hydrophobic layer on the surface, effectively blocking the penetration of water molecules. By synthesizing polyurethane acrylate containing multiple unsaturated bonds, and selecting trimethylolpropane triacrylate as a diluent, the cross-linking degree is improved, a high-density cross-linked network is constructed, the hardness, wear resistance and water barrier ability of the coating are improved, the flexible segment 1, 6-hexanediol is used as a chain extender, the flexible segment can absorb and disperse energy through molecular chain rotation, stretching and sliding, and the toughness and impact resistance of the coating are improved. The amino group and the carbonyl group in the hard segment triazine ring form an interfacial hydrogen bond, which enhances the interaction between the polymer chains, thereby significantly improving the mechanical properties of the material. The nanofiller with core-shell structure formed by microcrystalline wax as core and silica as shell is added to the material, and the micro-rough structure and the low surface energy coating cooperatively construct the super-hydrophobic structure. The silica shell is used as the outer shell, which significantly improves the wear resistance and scratch resistance of the coating, and when the coating is worn or scratched, the silica shell is worn off, and the internal microcrystalline wax core is released, which "repairs" the scratched area under the action of friction and heat, and restores its hydrophobicity. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be described below. Obviously, the described embodiments are only a part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0027] Embodiment 1, a preparation method of a waterproof UV curing coating, specifically comprising the following steps:

[0028] The polyurethane acrylate and the modified filler are uniformly mixed, and trimethylolpropane triacrylate and 2-hydroxy-2-methyl-1-phenylpropanone are added under the condition of a rotation speed of 70 r / min. After uniform stirring for 30 min, ultrasonic treatment is carried out under the condition of a temperature of 20℃ and a frequency of 30 kHz for 4h, to obtain the waterproof UV curing coating.

[0029] The weight ratio of the polyurethane acrylate, the modified filler, the trimethylolpropane triacrylate and the 2-hydroxy-2-methyl-1-phenylpropanone is 100:20:60:4.

[0030] The polyurethane acrylate is prepared by the following steps:

[0031] Step Al: Intermediate 1 was prepared by mixing 1H, 1H, 2H, 2H-perfluorodecanethiol, acrylonitrile, benzoine dimethyl ether and tetrahydrofuran uniformly, and then reacting at a rotation speed of 110 r / min, a temperature of 20 °C and under UV irradiation for 1 min; and then mixing dicyandiamide, Intermediate 1, potassium hydroxide and dimethyl sulfoxide uniformly, and then reacting at a rotation speed of 100 r / min, a temperature of 110 °C and under nitrogen for 12 h, filtering, and cooling and crystallizing to obtain Intermediate 2.

[0032] Step A2: Intermediate 3 was prepared by mixing itaconic acid, glycidyl methacrylate and N,N-dimethylformamide uniformly, and then stirring and adding methyl hydroquinone and triethylamine under nitrogen at a rotation speed of 120 r / min and a temperature of 90 °C for 6 h; and then mixing hexamethylene diisocyanate and N,N-dimethylformamide uniformly, and then stirring and adding Intermediate 2 and dibutyltin dilaurate under nitrogen at a rotation speed of 80 r / min and a temperature of 40 °C for 2 h, and then adding Intermediate 3 and reacting at a temperature of 60 °C for 4 h to obtain a polyurethane prepolymer;

[0033] Step A3: The polyurethane acrylate was prepared by mixing 1,6-hexanediol, the polyurethane prepolymer, methyl hydroquinone, tetrahydrofuran and dibutyltin dilaurate uniformly, and then reacting at a rotation speed of 100 r / min and a temperature of 60 °C under nitrogen for 5 h, and then adding poly-pentaerythritol five acrylate and reacting for 2 h.

[0034] The molar ratio of 1H, 1H, 2H, 2H-perfluorodecanethiol to acrylonitrile in Step Al was 1.1:1, and the amount of benzoine dimethyl ether was 3% of the mass of 1H, 1H, 2H, 2H-perfluorodecanethiol, and the amounts of dicyandiamide, Intermediate 1, potassium hydroxide and dimethyl sulfoxide were 0.15 mol:0.16 mol:2.66 g:120 mL.

[0035] The molar ratio of itaconic acid to glycidyl methacrylate in Step A2 was 1:1, the amount of methyl hydroquinone was 3% of the mass of itaconic acid, the amount of triethylamine was 4% of the mass of itaconic acid, the molar ratio of hexamethylene diisocyanate, Intermediate 2 and Intermediate 3 was 1.2:0.4:0.5, the amount of hexamethylene diisocyanate was 1 mol, and the amount of dibutyltin dilaurate was 2% of the mass of hexamethylene diisocyanate.

[0036] The molar ratio of 1,6-hexanediol, the polyurethane prepolymer and poly-pentaerythritol five acrylate in Step A3 was 1:1.4:0.1, the amount of 1,6-hexanediol was 1 mol, the amount of methyl hydroquinone was 1% of the mass of the polyurethane prepolymer, and the amount of dibutyltin dilaurate was 3% of the mass of the polyurethane prepolymer.

[0037] The modified filler is prepared by the following steps:

[0038] Step B1: uniformly mix N-cocoyl-1,3-propanediamine and deionized water, stir at a speed of 100 r / min and a temperature of 70℃ for 10 min, add melted microcrystalline wax, emulsify for 0.5 h, and prepare a dispersion liquid, then high-pressure homogenize the dispersion liquid and quickly cool to prepare a microcrystalline wax emulsion;

[0039] Step B2: stir the microcrystalline wax emulsion at a speed of 90 r / min and a temperature of 40℃, add ammonia water to adjust the pH to 9, add tetraethyl orthosilicate and anhydrous ethanol, and react for 10 h, then centrifuge, wash and dry to obtain a pretreated filler;

[0040] Step B3: disperse the pretreated filler in tetrahydrofuran, stir at a speed of 100 r / min, a temperature of 60℃ and a pH of 4, and add vinyltrimethoxysilane to react for 8 h to prepare a modified filler.

[0041] The amount of N-cocoyl-1,3-propanediamine in step B1 is 6% of the mass of the microcrystalline wax.

[0042] The amount of tetraethyl orthosilicate in step B2 is 15% of the mass of the microcrystalline wax emulsion.

[0043] The amount of vinyltrimethoxysilane in step B3 is 3% of the mass of the pretreated filler.

[0044] Example 2, a preparation method of a waterproof UV-cured coating, specifically comprising the following steps:

[0045] Uniformly mix the polyurethane acrylate and the modified filler, stir at a speed of 75 r / min, add trimethylolpropane triacrylate and 2-hydroxy-2-methyl-1-phenylpropanone, uniformly stir for 30 min, then ultrasonically treat at a temperature of 22℃ and a frequency of 35 kHz for 4 h to prepare a waterproof UV-cured coating.

[0046] The weight ratio of the polyurethane acrylate, the modified filler, the trimethylolpropane triacrylate and the 2-hydroxy-2-methyl-1-phenylpropanone is 110:25:70:5.

[0047] The polyurethane acrylate is prepared by the following steps:

[0048] Step A1: 1H,1H,2H,2H-perfluorodecylthiols, acrylonitrile, benzoin dimethyl ether and tetrahydrofuran are mixed evenly and reacted for 1 min at a speed of 120 r / min, a temperature of 22℃ and ultraviolet irradiation to obtain intermediate 1. Dicyandiamide, intermediate 1, potassium hydroxide and dimethyl sulfoxide are mixed evenly and reacted for 13 h at a speed of 114 r / min, a temperature of 115℃ and nitrogen purging. After filtration and cooling crystallization, intermediate 2 is obtained.

[0049] Step A2: Itaconic acid, glycidyl methacrylate, and N,N-dimethylformamide are mixed evenly. Under the conditions of 125 r / min, 100℃, and nitrogen purging, methyl hydroquinone and triethylamine are added and stirred for 7 h to obtain intermediate 3. Hexamethylene diisocyanate and N,N-dimethylformamide are mixed evenly. Under the conditions of 90 r / min, 45℃, and nitrogen purging, intermediate 2 and dibutyltin dilaurate are added and stirred for 2 h. The temperature is raised to 65℃, intermediate 3 is added, and the reaction is carried out for 5 h to obtain polyurethane primary polymer.

[0050] Step A3: Mix 1,6-hexanediol, polyurethane primary polymer, methyl hydroquinone, tetrahydrofuran and dibutyltin dilaurate evenly, and react for 6 hours at a speed of 110 r / min, a temperature of 65℃ and a nitrogen atmosphere. Add polydipentaerythritol pentaacrylate and react for 2 hours to obtain polyurethane acrylate.

[0051] In step A1, the molar ratio of 1H,1H,2H,2H-perfluorodecyl mercaptan to acrylonitrile is 1.1:1, the amount of benzoin dimethyl ether used is 4% of the mass of 1H,1H,2H,2H-perfluorodecyl mercaptan, and the ratio of dicyandiamide, intermediate 1, potassium hydroxide and dimethyl sulfoxide used is 0.15mol:0.16mol:2.66g:120mL.

[0052] In step A2, the molar ratio of itaconic acid and glycidyl methacrylate is 1:1, the amount of methyl hydroquinone is 4% of the mass of itaconic acid, the amount of triethylamine is 5% of the mass of itaconic acid, the molar ratio of hexamethylene diisocyanate, intermediate 2 and intermediate 3 is 1.2:0.4:0.5, the amount of hexamethylene diisocyanate is 1.1 mol, and the amount of dibutyltin dilaurate is 3% of the mass of hexamethylene diisocyanate.

[0053] In step A3, the molar ratio of 1,6-hexanediol, polyurethane primary polymer, and polydipentaerythritol pentaacrylate is 1:1.4:0.1, the amount of 1,6-hexanediol is 1.1 mol, the amount of methyl hydroquinone is 2% of the mass of the polyurethane primary polymer, and the amount of dibutyltin dilaurate is 4% of the mass of the polyurethane primary polymer.

[0054] The modified filler is prepared by the following steps:

[0055] Step B1: uniformly mix N-cocoyl-1,3-propanediamine and deionized water, stir at a speed of 105 r / min and a temperature of 75℃ for 15 min, add melted microcrystalline wax, emulsify for 0.5 h, and prepare a dispersion liquid, then high-pressure homogenize the dispersion liquid and quickly cool to prepare a microcrystalline wax emulsion;

[0056] Step B2: stir the microcrystalline wax emulsion at a speed of 100 r / min and a temperature of 50℃, add ammonia water to adjust the pH to 10, add tetraethyl orthosilicate and anhydrous ethanol, and react for 11 h, then centrifuge, wash and dry to obtain a pretreated filler;

[0057] Step B3: disperse the pretreated filler in tetrahydrofuran, stir at a speed of 110 r / min, a temperature of 70℃ and a pH of 4, and add vinyltrimethoxysilane to react for 9 h to prepare a modified filler.

[0058] The amount of N-cocoyl-1,3-propanediamine in step B1 is 7% of the mass of the microcrystalline wax.

[0059] The amount of tetraethyl orthosilicate in step B2 is 18% of the mass of the microcrystalline wax emulsion.

[0060] The amount of vinyltrimethoxysilane in step B3 is 4% of the mass of the pretreated filler.

[0061] Example 3, a preparation method of a waterproof UV-cured coating, specifically comprising the following steps:

[0062] Uniformly mix the polyurethane acrylate and the modified filler, stir at a speed of 80 r / min, add trimethylolpropane triacrylate and 2-hydroxy-2-methyl-1-phenylpropanone, uniformly stir for 30 min, then ultrasonically treat at a temperature of 25℃ and a frequency of 40 kHz for 4 h to prepare a waterproof UV-cured coating.

[0063] The weight ratio of the polyurethane acrylate, the modified filler, the trimethylolpropane triacrylate and the 2-hydroxy-2-methyl-1-phenylpropanone is 120:30:80:6.

[0064] The polyurethane acrylate is prepared by the following steps:

[0065] Step Al: 1H, 1H, 2H, 2H-perfluorodecanethiol, acrylonitrile, benzoine dimethyl ether and tetrahydrofuran were mixed uniformly, and reacted for 2 min under the conditions of 130 r / min rotation speed, 25°C temperature and UV irradiation to prepare intermediate 1. Dicyandiamide, intermediate 1, potassium hydroxide and dimethyl sulfoxide were mixed uniformly, and reacted for 15 h under the conditions of 120 r / min rotation speed, 120°C temperature and nitrogen flow. Filtration and cooling crystallization were performed to prepare intermediate 2.

[0066] Step A2: Itaconic acid, glycidyl methacrylate and N,N-dimethylformamide were mixed uniformly, and stirred and methylhydroquinone and triethylamine were added and reacted for 8 h under the conditions of 130 r / min rotation speed, 110°C temperature and nitrogen flow. Hexamethylene diisocyanate and N,N-dimethylformamide were mixed uniformly, and stirred and intermediate 2 and dibutyltin dilaurate were added and reacted for 3 h under the conditions of 100 r / min rotation speed, 50°C temperature and nitrogen flow. The temperature was increased to 70°C, and intermediate 3 was added and reacted for 6 h to prepare a polyurethane prepolymer.

[0067] Step A3: 1,6-hexanediol, the polyurethane prepolymer, methylhydroquinone, tetrahydrofuran and dibutyltin dilaurate were mixed uniformly, and reacted for 7 h under the conditions of 120 r / min rotation speed, 70°C temperature and nitrogen flow. Polydi-pentaerythritol five acrylate was added and reacted for 3 h to prepare a polyurethane acrylate.

[0068] The molar ratio of 1H, 1H, 2H, 2H-perfluorodecanethiol to acrylonitrile in Step Al was 1.1:1, and the amount of benzoine dimethyl ether was 5% of the mass of 1H, 1H, 2H, 2H-perfluorodecanethiol. The amounts of dicyandiamide, intermediate 1, potassium hydroxide and dimethyl sulfoxide were 0.15 mol, 0.16 mol, 2.66 g and 120 mL, respectively.

[0069] The molar ratio of itaconic acid to glycidyl methacrylate in Step A2 was 1:1, and the amount of methylhydroquinone was 5% of the mass of itaconic acid. The amount of triethylamine was 8% of the mass of itaconic acid. The molar ratio of hexamethylene diisocyanate to intermediate 2 to intermediate 3 was 1.2:0.4:0.5, and the amount of hexamethylene diisocyanate was 1.3 mol. The amount of dibutyltin dilaurate was 4% of the mass of hexamethylene diisocyanate.

[0070] The molar ratio of 1,6-hexanediol, polyurethane oligomer and polydi-pentaerythritol five acrylate in step A3 is 1:1.4:0.1, the amount of 1,6-hexanediol is 1.3 mol, the amount of methyl hydroquinone is 3% of the mass of the polyurethane oligomer, and the amount of dibutyltin dilaurate is 5% of the mass of the polyurethane oligomer.

[0071] The modified filler is prepared by the following steps:

[0072] Step B1: uniformly mix N-cocoalkyl-1,3-propanediamine and deionized water, stir at a speed of 110 r / min and a temperature of 80℃ for 20 min, add melted microcrystalline wax, emulsify for 1 h, prepare a dispersion, and prepare a microcrystalline wax emulsion by high-pressure homogenization and rapid cooling;

[0073] Step B2: stir the microcrystalline wax emulsion at a speed of 110 r / min and a temperature of 60℃, add ammonia water to adjust the pH to 11, add tetraethyl orthosilicate and anhydrous ethanol, and react for 12 h, then centrifuge, wash and dry to obtain a pretreated filler;

[0074] Step B3: disperse the pretreated filler in tetrahydrofuran, stir at a speed of 120 r / min, a temperature of 80℃ and a pH of 5, and add vinyltrimethoxysilane to react for 10 h to obtain a modified filler.

[0075] The amount of N-cocoalkyl-1,3-propanediamine in step B1 is 8% of the mass of the microcrystalline wax.

[0076] The amount of tetraethyl orthosilicate in step B2 is 20% of the mass of the microcrystalline wax emulsion.

[0077] The amount of vinyltrimethoxysilane in step B3 is 5% of the mass of the pretreated filler.

[0078] Comparative Example 1: This comparative example is the same as Example 1 except that no intermediate 2 is added in step A2.

[0079] Comparative Example 2: This comparative example is the same as Example 1 except that nano-silicon dioxide is used instead of the modified filler, and the remaining steps are the same.

[0080] Comparative Example 3: This comparative example is the same as Example 1 except that no intermediate 3 is added in step A2, and the remaining steps are the same.

[0081] Comparative Example 4: This comparative example is the same as Example 1 except that n-propyl mercaptan is used instead of 1H,1H,2H,2H-perfluorodecyl mercaptan, and the remaining steps are the same.

[0082] The waterproof UV-cured coatings prepared from Examples 1-3 and Comparative Examples 1-4 were coated on the surface of a wood board and a tin sheet, and after UV curing for 20 s, a cured coating layer with a thickness of 20 mm was obtained. The pencil hardness and flexibility of the coating layer were tested on the wood board, and the waterproof performance was tested on the tin sheet.

[0083] The hardness of the cured coating layer was tested by a trolley-type pencil hardness tester according to the standard GB / T6739-2006 "Determination of Film Hardness by Pencil Method for Pigment and Varnish Coatings". The test results are shown in Table 1. The pencil hardness grade ranges from 6B to 6H from the lowest to the highest. The pencil was fixed at an angle of 45° on the surface of the coating layer to test three parallel scratches. When a certain hardness grade (such as 3H) appeared twice or more times, the coating layer was determined to have a pencil hardness of the previous grade (2H).

[0084] The flexibility of the coating layer was tested according to the standard GB / T1731-2020 "Determination of Film Flexibility". The test results are shown in Table 1. The sample was bent around the shaft rod of the flexibility tester at an angle of 90°. The shaft rod diameters included 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm and 7 mm, which were tested from large to small. The smallest shaft rod diameter at which the coating layer did not crack or fall off was taken as the flexibility value of the coating layer.

[0085] The sample was placed in a 60°C oven for 12 h, then cut into regular blocks, wrapped with aluminum foil at the edge cutting or broken edge, and weighed. Then it was immersed in deionized water at room temperature for 48 h. After taking it out, the surface free water was wiped off with filter paper, and the coating surface morphology was observed and the mass was immediately measured to calculate the water absorption rate of the coating layer. The test results are shown in Table 1.

[0086] Table 1

[0087]

[0088] As shown in Table 1, the UV-cured coating layer prepared from Examples 1-3 has a pencil hardness of 5H, a flexibility value of 2 mm, and a water absorption rate of 0.69-0.82% after immersion in deionized water for 48 h. The surface of the coating layer has no cracks and bubbles.

[0089] The above content is only an example and explanation of the concept of the present application. Those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace them, as long as they do not deviate from the concept of the present application or exceed the scope defined by the present claims.

Claims

1. A process for the preparation of a water repellent UV-cured coating, characterized in that: Specifically comprising the following steps: The polyurethane acrylate and the modified filler are mixed and stirred, trimethylolpropane triacrylate and 2-hydroxy-2-methyl-1-phenylpropanone are added, after uniform stirring, ultrasonic treatment is performed, and the waterproof UV curing coating is prepared; The weight ratio of the polyurethane acrylate, the modified filler, trimethylolpropane triacrylate and 2-hydroxy-2-methyl-1-phenylpropanone is 100-120:20-30:60-80:4-6; The polyurethane acrylate is prepared by the following steps: Step A1: 1H, 1H, 2H, 2H-perfluorodecyl mercaptan, acrylonitrile, benzoin dimethyl ether and tetrahydrofuran are uniformly mixed and reacted to prepare intermediate 1, dicyandiamide, intermediate 1, potassium hydroxide and dimethyl sulfoxide are uniformly mixed and reacted, filtered, and cooled and crystallized to prepare intermediate 2; Step A2: Itaconic acid, glycidyl methacrylate and N,N-dimethylformamide are mixed and stirred, and methylhydroquinone and triethylamine are added and reacted to prepare intermediate 3, hexamethylene diisocyanate and N,N-dimethylformamide are mixed and stirred, and intermediate 2 and dibutyltin dilaurate are added and reacted, heated, and intermediate 3 is added and reacted to prepare a polyurethane prepolymer; Step A3: 1,6-hexanediol, polyurethane prepolymer, methylhydroquinone, tetrahydrofuran and dibutyltin dilaurate are uniformly mixed and reacted, and polydi-pentaerythritol five acrylate is added and reacted to prepare the polyurethane acrylate; The modified filler is prepared by the following steps: Step B1: N-cocoyl-1,3-propanediamine and deionized water are uniformly mixed and stirred, and the molten microcrystalline wax is emulsified to prepare a dispersion, and the dispersion is high-pressure homogenized and quickly cooled to prepare a microcrystalline wax emulsion; Step B2: The microcrystalline wax emulsion is stirred and ammonia is added to adjust the pH, tetraethyl orthosilicate and anhydrous ethanol are added and reacted, centrifuged, washed and dried to obtain a pretreated filler; Step B3: The pretreated filler is dispersed in tetrahydrofuran, stirred and vinyltrimethoxysilane is added and reacted to prepare the modified filler.

2. A process for the preparation of a water repellent UV-cured coating according to claim 1, characterized in that: The molar ratio of 1H, 1H, 2H, 2H-perfluorodecyl mercaptan to acrylonitrile in step A1 is 1.1:1, and the amount of benzoin dimethyl ether is 3-5% of the mass of 1H, 1H, 2H, 2H-perfluorodecyl mercaptan, and the amount ratio of dicyandiamide, intermediate 1, potassium hydroxide and dimethyl sulfoxide is 0.15 mol:0.16 mol:2.66 g:120 mL.

3. The method for preparing a waterproof UV-curable coating according to claim 1, characterized in that: The molar ratio of itaconic acid to glycidyl methacrylate in step A2 is 1:1, the amount of methylhydroquinone is 3-5% of the mass of itaconic acid, the amount of triethylamine is 4-8% of the mass of itaconic acid, the molar ratio of hexamethylene diisocyanate, intermediate 2 and intermediate 3 is 1.2:0.4:0.5, and the amount of dibutyltin dilaurate is 2-4% of the mass of hexamethylene diisocyanate.

4. The method for preparing a waterproof UV-curable coating according to claim 1, characterized in that: The molar ratio of 1,6-hexanediol, polyurethane oligomer and polydi-pentaerythritol-pentaacrylate in step A3 is 1:1.4:0.1, the dosage of methylhydroquinone is 1-3% of the mass of the polyurethane oligomer, and the dosage of dibutyltin dilaurate is 3-5% of the mass of the polyurethane oligomer.

5. The method for preparing a waterproof UV-curable coating according to claim 1, characterized in that: The dosage of N-cocoalkyl-1,3-propanediamine in step B1 is 6-8% of the mass of the microcrystalline wax.

6. The method for preparing a waterproof UV-curable coating according to claim 1, characterized in that: The dosage of tetraethyl orthosilicate in step B2 is 15-20% of the mass of the microcrystalline wax emulsion.

7. The method for preparing a waterproof UV-curable coating according to claim 1, characterized in that: The dosage of vinyltrimethoxysilane in step B3 is 3-5% of the mass of the pretreated filler.

8. A water repellent UV-cured coating characterized by: Prepared according to the preparation method in any one of claims 1-7.

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