A UV-curable coating and its preparation method

Abstract

This invention belongs to the field of UV-curable coatings, specifically relating to a UV-curable coating and its preparation method. The UV-curable coating provided by this invention contains a modified acrylate resin in a mass ratio of 1:(0.5~2):(0.3~1.5):(0.02~0.2):(0.002~0.08):(0~0.08), a monofunctional diluent, a polyfunctional diluent, a photoinitiator, an anti-hydrolysis agent, and optional additives; the mass ratio of the monofunctional diluent to the polyfunctional diluent is 1:(0.3~1.5); the modified acrylate resin has the structure shown in formula (1). The key to this invention is that the modified acrylate resin with a specific structure, the monofunctional diluent, the polyfunctional diluent, the photoinitiator, the anti-hydrolysis agent, and the additives are synergistically combined in a specific ratio to form a UV-curable coating, thereby obtaining a UV-curable coating with good adhesion, waterproof performance, and acid and alkali corrosion resistance.

Description

Technical Field

[0001] This invention belongs to the field of photocurable coatings, specifically relating to an ultraviolet light curable coating and its preparation method. Background Technology

[0002] UV-curable coatings are environmentally friendly and energy-saving coatings that cure under ultraviolet light. They not only cure quickly but also save energy compared to thermosetting coatings. UV-curable coatings are widely used on the surfaces of materials such as metals, leather, wood, and plastics, and have also been successfully applied in fields such as optical fibers, printed circuit boards, and electronic component packaging. However, most commercially available UV-curable coatings suffer from poor hydrolysis resistance, limiting their application range and scenarios. Furthermore, in practical applications, UV-curable coatings may need to be exposed to the environment for extended periods, making them susceptible to corrosion and peeling due to external environmental conditions. Therefore, good corrosion resistance is also required for UV-curable coatings. Summary of the Invention

[0003] One of the objectives of this invention is to address the shortcomings of existing UV-curable coatings on the market, which have poor water resistance and poor corrosion resistance, and to provide a UV-curable coating with good adhesion, high waterproof performance, and good resistance to acid and alkali corrosion.

[0004] Specifically, the UV-curable coating contains a modified acrylate resin in a mass ratio of 1:(0.5-2.5):(0.3-2):(0.02-0.25):(0.002-0.1):(0-0.1), a monofunctional diluent, a polyfunctional diluent, a photoinitiator, an anti-hydrolysis agent, and optional additives; the mass ratio of the monofunctional diluent to the polyfunctional diluent is 1:(0.3-1.5); the polyfunctional diluent is selected from at least one of ethoxylated bisphenol A diacrylate, ethoxylated bisphenol A dimethacrylate, and ethoxylated trimethylolpropane triacrylate; the modified acrylate resin has a structure as shown in formula (1).

[0005]

[0006] In formula (1), R1 is a group derived from diisocyanate, and R2 is a C1 to C2 group. 10 The alkylene group, R3 is a C1 to C4 alkylene group, R4 is H or methyl, and n is an integer from 1 to 10.

[0007] In a preferred embodiment, the modified acrylate resin contains 20-40 parts by weight, the monofunctional diluent contains 25-45 parts by weight, the polyfunctional diluent contains 15-35 parts by weight, the photoinitiator contains 1-5 parts by weight, the anti-hydrolysis agent contains 0.1-2 parts by weight, and the additives contain 0-2 parts by weight.

[0008] In a preferred embodiment, the modified acrylate resin is prepared by the following method:

[0009] S1. A mixture of diisocyanate and diamine is subjected to an addition reaction to obtain a polyurea prepolymer with isocyanate double-terminated ends;

[0010] S2. The polyurea prepolymer obtained in step S1 and the hydroxyl-terminated acrylate are subjected to a capping reaction in the presence of a polymerization inhibitor and an initiator to obtain a modified acrylate resin.

[0011] In a preferred embodiment, the molar ratio of the diisocyanate to the diamine is (1.1 to 1.3):1.

[0012] In a preferred embodiment, the hydroxyl-terminated acrylate is used to ensure that the NCO groups in the reaction system are substantially completely reacted.

[0013] In a preferred embodiment, the amount of the polymerization inhibitor added is 0.02 to 0.04 wt% of the total amount of the reactants.

[0014] In a preferred embodiment, the amount of the initiator added is 0.1 to 0.5 wt% of the total amount of the reaction raw materials.

[0015] In a preferred embodiment, the diisocyanate is selected from at least one of toluene diisocyanate, norbornene diisocyanate, isophorone diisocyanate, isophenyl dimethyl diisocyanate, dicyclohexylmethane-4,4-diisocyanate, pentamethylene diisocyanate, and hexamethylene diisocyanate.

[0016] In a preferred embodiment, the diamine is selected from at least one of ethylenediamine, 1,2-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, and 1,10-decanediamine.

[0017] In a preferred embodiment, the hydroxyl-terminated acrylate is selected from at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate.

[0018] In a preferred embodiment, the modified acrylate resin has a viscosity of 1000–25000 cps at 25°C.

[0019] In a preferred embodiment, the monofunctional diluent is a monofunctional acrylate monomer.

[0020] In a preferred embodiment, the monofunctional diluent is selected from at least one of glycidyl acrylate, glycidyl methacrylate, 3,3,5-trimethylcyclohexyl acrylate (TMCHA), ethoxyethyl acrylate, isooctyl acrylate (2-EHA), 4-hydroxycyclohexyl methacrylate, tetrahydrofuran acrylate, and isobornyl acrylate (IBOA).

[0021] In a preferred embodiment, the anti-hydrolysis agent is a carbodiimide-based anti-hydrolysis agent.

[0022] The second objective of this invention is to provide a method for preparing the above-mentioned UV-curable coating, which includes: mixing and stirring a modified acrylate resin, a monofunctional diluent, a polyfunctional diluent, a photoinitiator, an anti-hydrolysis agent, and optional additives until uniform, and then discharging the material in the dark to obtain the UV-curable coating.

[0023] The key to this invention lies in the synergistic combination of modified acrylate resin, monofunctional diluent, polyfunctional diluent, photoinitiator, anti-hydrolysis agent, and additives in a specific ratio to form a UV-curable coating. The resulting UV-curable coating, on the one hand, possesses excellent waterproof performance through the synergistic effect of the modified acrylate resin, polyfunctional diluent, and anti-hydrolysis agent with specific structures; on the other hand, the presence of a polyurea structure in the modified acrylate resin enhances the coating system's resistance to acid and alkali corrosion. Furthermore, the combination of monofunctional and polyfunctional diluents not only improves the waterproof performance of the UV-curable coating but also increases the crosslinking density of the system, thereby enhancing the adhesion of the UV-curable coating. In summary, the UV-curable coating provided by this invention not only exhibits excellent adhesion and acid and alkali corrosion resistance but also maintains its appearance without deformation (deformation includes surface wrinkling and blistering) even after 1500 hours in a 95% RH environment. Detailed Implementation

[0024] The UV-curable coating provided by this invention contains a modified acrylic resin in a mass ratio of 1:(0.5~2.5):(0.3~2):(0.02~0.25):(0.002~0.1):(0~0.1), a monofunctional diluent, a polyfunctional diluent, a photoinitiator, an anti-hydrolysis agent, and optional additives. The modified acrylate resin and the monofunctional diluent have a mass ratio of 1:(0.5-2.5), such as 1:0.5, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:1.8, 1:2, 1:2.2, 1:2.5, or any value between them; the modified acrylate resin and the polyfunctional diluent have a mass ratio of 1:(0.3-2), such as 1:0.3, 1:0.5, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:1.8, 1:2, or any value between them; the modified acrylate resin and the photoinitiator have a mass ratio of 1:(0.02-0.25), such as 1:0.02, 1:0.05, 1:0.08, 1:0.1, 1:0.25, or any value between them. The mass ratio of the modified acrylate resin to the anti-hydrolysis agent is 1:(0.002-0.1), such as 1:0.002, 1:0.005, 1:0.008, 1:0.01, 1:0.02, 1:0.05, 1:0.08, 1:0.1, or any value between them; the mass ratio of the modified acrylate resin to the additive is 1:(0-0.1), such as 0, 1:0.002, 1:0.005, 1:0.008, 1:0.01, 1:0.02, 1:0.05, 1:0.08, 1:0.1, or any value between them.

[0025] The mass ratio of the monofunctional diluent to the polyfunctional diluent is 1:(0.3–1.5), such as 1:0.3, 1:0.5, 1:0.8, 1:1, 1:1.2, 1:1.5, or any value between them. The polyfunctional diluent is selected from at least one of ethoxylated bisphenol A diacrylate, ethoxylated bisphenol A dimethacrylate, and ethoxylated trimethylolpropane triacrylate. The addition of the polyfunctional diluent not only helps improve the waterproof performance of the coating but also increases the crosslinking density of the coating, which is beneficial for enhancing the adhesion between the coating and the substrate.

[0026] The modified acrylate resin has the structure shown in formula (1);

[0027]

[0028] In formula (1), R1 is a group derived from diisocyanate, and R2 is a C1 to C2 group. 10The alkylene group, R3 is a C1-C4 alkylene group, R4 is H or methyl, and n is an integer from 1 to 10. Wherein, the C1-C4 alkylene group... 10 The alkylene group can be at least one selected from methylene, ethylene, n-propylene, isopropylene, n-butylene, secondary butylene, isobutylene, tert-butylene, n-pentylene, isopentylene, tert-pentylene, neopentylene, n-hexylene, n-heptylene, and n-octylene. The C1-C4 alkylene group can be at least one selected from methylene, ethylene, n-propylene, isopropylene, n-butylene, secondary butylene, isobutylene, and tert-butylene. n is an integer from 1 to 10, such as 1, 2, 3, 5, 7, 9, etc.

[0029] In this invention, the content of the modified acrylate resin is preferably 20-40 parts by weight, such as 20, 22, 25, 28, 30, 32, 35, 38, 40 parts by weight or any value between them. The content of the monofunctional diluent is preferably 25-45 parts by weight, such as 25, 28, 30, 32, 35, 38, 40, 42, 45 parts by weight or any value between them. The content of the polyfunctional diluent is preferably 15-35 parts by weight, such as 15, 18, 20, 22, 25, 28, 30, 32, 35 parts by weight or any value between them. The content of the photoinitiator is preferably 1-5 parts by weight, such as 1, 2, 3, 4, 5 parts by weight or any value between them. The content of the anti-hydrolysis agent is preferably 0.1 to 2 parts by weight, such as 0.1, 0.2, 0.5, 0.8, 1, 1.2, 1.5, 1.8, 2 parts by weight or any value between them. The content of the auxiliary agent is preferably 0 to 2 parts by weight, such as 0, 0.2, 0.5, 0.8, 1, 1.2, 1.5, 1.8, 2 parts by weight or any value between them.

[0030] In this invention, the viscosity of the modified acrylate resin at 25°C is preferably 1000 to 25000 cps, such as 1000 cps, 5000 cps, 10000 cps, 15000 cps, 20000 cps, 25000 cps or any value between them.

[0031] In this invention, the modified acrylate resin is preferably prepared by the following method:

[0032] S1. A mixture of diisocyanate and diamine is subjected to an addition reaction to obtain a polyurea prepolymer with isocyanate double-terminated ends;

[0033] S2. The polyurea prepolymer obtained in step S1 and the hydroxyl-terminated acrylate are subjected to a capping reaction in the presence of a polymerization inhibitor and an initiator to obtain a modified acrylate resin.

[0034] In the preparation process of the modified acrylate resin described above, in step S1, the addition reaction time is preferably 30-50°C, such as 30°C, 32°C, 35°C, 38°C, 40°C, 42°C, 45°C, 48°C, 50°C or any value between them; the addition reaction time is preferably 1-4h, such as 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h or any value between them.

[0035] In the preparation process of the modified acrylate resin described above, in step S2, the temperature of the end-capping reaction is preferably 70-95℃, such as 70℃, 75℃, 80℃, 85℃, 90℃, 95℃ or any value between them; the time of the end-capping reaction is preferably 2-8h, such as 2h, 3h, 4h, 5h, 6h, 7h, 8h or any value between them.

[0036] In the preparation of the modified acrylate resin, isocyanates are sensitive to moisture. Therefore, to ensure the smooth reaction of diisocyanate with diamine and hydroxyl-terminated acrylate, the reaction vessel and reactants need to be dehydrated before the reaction is started, and the reaction system needs to be placed under an inert atmosphere. Dehydration of the reaction vessel typically involves drying it at 130–150°C for 2–4 hours. Dehydration of the reactants typically involves methods such as heating and vacuuming, freeze-drying, molecular sieve dehydration, and glove box evacuation. Placing the reaction system under an inert atmosphere typically involves introducing a chemical inert gas into the reaction vessel, evacuating the vacuum, and then filling it with an inert gas to maintain the reaction system under an inert atmosphere. The chemical inert gas can be nitrogen or argon, preferably nitrogen.

[0037] In one specific embodiment, the preparation process of the modified acrylate resin can be as follows: Under a nitrogen atmosphere, dehydrated diisocyanate and diamine are added to a three-necked flask. The reaction temperature is controlled at 30–50°C, and the mixture is stirred for 1–4 hours to allow the diisocyanate and diamine to undergo an end-capping reaction, obtaining a polyurea prepolymer with isocyanate double-capped ends. Then, terminal hydroxyl acrylate, a polymerization inhibitor, and an initiator are added. The reaction temperature is controlled at 70–95°C, and the mixture is stirred for 2–8 hours. During the reaction, the content of NCO groups in the reaction system is monitored every 0.5–1.5 hours. The reaction is terminated when the mass percentage of NCO groups is ≤0.05%, indicating that the isocyanate groups at the molecular chain ends have basically completely reacted. The mixture is then cooled and discharged to obtain the modified acrylate resin. The amount of terminal hydroxyl acrylate used is the total mass required to ensure that the NCO groups in the reaction system are basically completely reacted. Preferably, the terminal hydroxyl acrylate can be added all at once or in stages.

[0038] In this invention, the molar ratio of the diisocyanate to the diamine is preferably (1.1–1.3):1, such as 1.1:1, 1.15:1, 1.2:1, 1.25:1, 1.3:1, or any value between them. The amount of the polymerization inhibitor added is preferably 0.02–0.04 wt% of the total reactants, such as 0.02 wt%, 0.025 wt%, 0.03 wt%, 0.035 wt%, 0.04 wt%, or any value between them. The amount of the initiator added is preferably 0.1–0.5 wt% of the total reactants, such as 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, or any value between them. The reactants include diisocyanate, diamine, and hydroxyl-terminated acrylate.

[0039] In this invention, the diisocyanate is preferably at least one selected from toluene diisocyanate, norbornene diisocyanate, isophorone diisocyanate, m-phenylenedimethyl diisocyanate, dicyclohexylmethane-4,4-diisocyanate, pentamethylene diisocyanate, and hexamethylene diisocyanate. More preferably, the diisocyanate may be pentamethylene diisocyanate and / or hexamethylene diisocyanate.

[0040] In this invention, the diamine is preferably at least one selected from ethylenediamine, 1,2-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, and 1,10-decanediamine; more preferably, the diamine may be ethylenediamine.

[0041] In this invention, the polymerization inhibitor is preferably at least one selected from hydroquinone, 4-methoxyphenol, p-hydroxyanisole, o-methylhydroquinone, and 2,6-di-tert-butyl-4-methylphenol.

[0042] In this invention, the initiator may be an organotin compound or an organobismuth compound. Specifically, the organotin compound is preferably selected from at least one of stannous acetate, trimethylstannous chloride, dibutyltin dilaurate, dibutyltin dichloride, and methyltin trichloride, and the organobismuth compound is selected from bismuth isooctanoate and / or bismuth carboxylate.

[0043] In this invention, the addition of the monofunctional diluent can, on the one hand, increase the reaction rate of the UV-curable coating, and on the other hand, reduce the viscosity of the coating system. Preferably, the monofunctional diluent is a monofunctional acrylate monomer, and specific examples include, but are not limited to, at least one of: glycidyl acrylate, glycidyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, 3,3,5-trimethylcyclohexyl acrylate, ethoxyethyl acrylate, isooctyl acrylate, 4-hydroxycyclohexyl methacrylate, tetrahydrofuran acrylate, and isobornyl acrylate.

[0044] In this invention, the anti-hydrolysis agent can react with the terminal carboxyl groups, terminal amine groups, and terminal hydroxyl groups generated during the hydrolysis of the UV-curable coating to generate stable and harmless products, effectively preventing further degradation and chain scission of the UV-curable coating, thereby improving the waterproofness of the UV-curable coating. The anti-hydrolysis agent is preferably a carbodiimide-based anti-hydrolysis agent, which can be a small molecule carbodiimide such as dicyclohexylcarbodiimide and / or diisopropylcarbodiimide, or a high molecular weight carbodiimide-based anti-hydrolysis agent such as Stabaxol P100 or Stabaxol P200.

[0045] In this invention, the photoinitiator is preferably at least one selected from Irgacure184, Irgacure369, Irgacure651, Irgacure754, Irgacure819, Irgacure907, Irgacure1173 and TPO.

[0046] In this invention, the additives are preferably leveling agents and / or defoamers. The leveling agent can be any substance known to those skilled in the art that can improve the leveling performance of coatings, and is preferably at least one of BYK307, BYK333, BYK358, BYK361, BYK366, EFKA3600, EFKA3883, and EFKA3886. The defoamer can be any substance known to those skilled in the art that can eliminate or reduce bubble formation in coatings, and is preferably at least one of BYK020, BKY054, BYK352, BYK354, BYK357, BKY1790, and BKY1794.

[0047] In this invention, the preparation method of the waterproof UV coating includes mixing and stirring a modified acrylic resin, a monofunctional diluent, a polyfunctional diluent, a photoinitiator, an anti-hydrolysis agent, and additives until homogeneous, and then discharging the mixture in the dark to obtain a UV-curable coating. In one specific embodiment, the method includes: sequentially adding the modified acrylic resin, monofunctional diluent, polyfunctional diluent, and anti-hydrolysis agent to a dual planetary hybrid reactor, stirring for 1-3 hours; then adding the photoinitiator and additives, stirring for 1-2 hours, followed by vacuum degassing, and then discharging and sealing in packaging to obtain the UV-curable coating. Furthermore, strict avoidance of white light is required throughout the entire preparation and stirring process.

[0048] The present invention will be described in detail below through specific embodiments.

[0049] In the following examples and comparative examples, the parts of raw materials refer to parts by weight.

[0050] Preparation Example 1: Preparation of Modified Acrylic Resin

[0051] Under a nitrogen atmosphere, 266.76 g (1.2 mol) of isophorone diisocyanate was added to a three-necked flask. Then, 60.10 g (1 mol) of ethylenediamine was weighed and added to the flask in two portions. The mixture was stirred at 35°C for 2 hours. Then, under a nitrogen atmosphere, 0.09 g of o-methylhydroquinone and 1.02 g of dibutyltin dichloride catalyst were added to the flask. The temperature was raised to 90°C, and 43.25 g (0.3 mol) of hydroxybutyl acrylate was gradually added dropwise in one batch. The mixture was stirred for 1 hour and then monitored. The content of NCO groups in the system was measured. The mass percentage of NCO was found to be greater than 0.05%. 14.42 g (0.1 mol) of hydroxybutyl acrylate was added dropwise. After stirring for 1 h, the content of NCO groups in the system was monitored. The above steps were repeated until the NCO content was ≤0.05%. Then the addition of hydroxybutyl acrylate was stopped and heating was stopped. At this time, the exposed isocyanate groups at the end of the molecular weight had basically reacted completely. The temperature was lowered to 40 °C and the material was discharged to obtain the modified acrylate resin, denoted as A1, with a viscosity of 7500 cps at 25 °C.

[0052] Preparation Example 2: Preparation of Modified Acrylic Resin

[0053] Under a nitrogen atmosphere, 185.00 g (1.1 mol) of hexamethylene diisocyanate was added to a three-necked flask. Then, 60.10 g (1 mol) of ethylenediamine was weighed and added to the flask in two portions. The mixture was stirred at 46 °C for 2.5 h. Then, under a nitrogen atmosphere, 0.08 g of hydroquinone and 0.78 g of trimethyltin chloride catalyst (dibutyltin dichloride) were added to the flask. The temperature was raised to 75 °C, and 39.04 g (0.3 mol) of hydroxyethyl methacrylate was gradually added dropwise in one batch. The mixture was stirred for 1 hour. After h, monitor the content of NCO groups in the system. If the mass percentage of NCO is greater than or equal to 0.05%, add 13.01 g (0.1 mol) of hydroxyethyl methacrylate dropwise. After stirring for 1 h, monitor the content of NCO groups in the system. Repeat the above steps until the NCO content is ≤0.05%. Then stop adding hydroxyethyl methacrylate and stop heating. This means that the exposed isocyanate groups at the molecular end have basically completely reacted. Cool down to 40 °C and discharge to obtain the modified acrylate resin, denoted as A2, with a viscosity of 13000 cps at 25 °C.

[0054] Preparation Example 3: Preparation of Modified Acrylic Resin

[0055] Under a nitrogen atmosphere, 341.00 g (1.2 mol) of dicyclohexylmethane-4,4-diisocyanate was added to a three-necked flask. Then, 60.10 g (1 mol) of ethylenediamine was weighed and added to the flask in two portions. The mixture was stirred at 38 °C for 3 h. Then, under a nitrogen atmosphere, 0.10 g of hydroquinone and 1.08 g of dibutyltin dichloride catalyst were added to the flask. The temperature was raised to 80 °C, and 43.25 g (0.3 mol) of hydroxypropyl methacrylate was gradually added dropwise in one batch. The mixture was stirred for 1 h. The content of NCO groups in the monitoring system was measured. If the mass percentage of NCO was greater than or equal to 0.05%, 14.42 g (0.1 mol) of hydroxypropyl methacrylate was added dropwise. After stirring for 1 hour, the content of NCO groups in the system was monitored. The above steps were repeated until the NCO content was ≤0.05%. Then, the addition of hydroxypropyl methacrylate was stopped and heating was stopped, indicating that the exposed isocyanate groups at the molecular end were basically completely reacted. The mixture was cooled to 40°C and discharged to obtain the modified acrylate resin, denoted as A3, with a viscosity of 10,000 cps at 25°C.

[0056] Example 1: Preparation of UV-curable coating

[0057] 40 parts of modified acrylate resin A1, 30 parts of hydroxypropyl acrylate, 8 parts of ethoxylated bisphenol A dimethicone, 15 parts of ethoxylated trimethylolpropane triacrylate, and 2 parts of anti-hydrolysis agent Stabaxol P100 were sequentially added to a dual planetary hybrid reactor and stirred for 2 hours. Then, 3.5 parts of Irgacure 369, 1 part of TPO, 0.3 parts of BYK361, and 0.2 parts of BKY054 were added to the reactor and stirred for 1.5 hours. After vacuum degassing, the material was discharged to obtain the UV-curable coating, denoted as B1.

[0058] Example 2: Preparation of UV-curable coating

[0059] 25 parts of modified acrylate resin A2, 40 parts of hydroxyethyl acrylate, 30 parts of ethoxylated bisphenol A diacrylate, and 0.5 parts of dicyclohexylcarbodiimide (anti-hydrolysis agent) were sequentially added to a double planetary hybrid reactor and stirred for 2 hours. Then, 2 parts of Irgacure 651, 2 parts of TPO, 0.4 parts of BYK361, and 0.1 parts of BKY054 were added to the reactor and stirred for 1 hour. After vacuum degassing, the material was discharged to obtain the UV-curable coating, denoted as B2.

[0060] Example 3: Preparation of UV-curable coating

[0061] 35 parts of modified acrylate resin A3, 38 parts of isobornyl acrylate, 21 parts of ethoxylated trimethylolpropane triacrylate, and 1 part of diisopropylcarbodiimide (anti-hydrolysis agent) were sequentially added to a double planetary hybrid reactor and stirred for 2 hours. Then, 1 part of Irgacure 184, 3 parts of TPO, 0.4 parts of BYK333, and 0.6 parts of BKY1790 were added to the reactor and stirred for 1 hour. After vacuum degassing, the material was discharged to obtain the UV-curable coating, denoted as B3.

[0062] Example 4: Preparation of UV-curable coating

[0063] 40 parts of modified acrylate resin A1, 38 parts of ethoxyethyl acrylate, 15 parts of ethoxylated bisphenol A dimethacrylate, and 0.5 parts of anti-hydrolysis agent Stabaxol P100 were sequentially added to a dual planetary hybrid reactor and stirred for 2 hours. Then, 4 parts of Irgacure 754, 1 part of TPO, 0.3 parts of BYK307, and 0.2 parts of BKY020 were added to the reactor and stirred for 1.5 hours. After vacuum degassing, the material was discharged to obtain the UV-curable coating, denoted as B4.

[0064] Example 5: Preparation of UV-curable coating

[0065] 20 parts of modified acrylate resin A1, 41 parts of tetrahydrofuran acrylate, 35 parts of ethoxylated trimethylolpropane triacrylate, and 2 parts of anti-hydrolysis agent Stabaxol P200 were sequentially added to a double planetary hybrid reactor and stirred for 2 hours. Then, 1 part of Irgacure 907, 0.5 parts of TPO, 0.3 parts of BYK358, and 0.2 parts of BKY354 were added to the reactor and stirred for 1.5 hours. After vacuum degassing, the material was discharged to obtain the UV-curable coating, denoted as B5.

[0066] Comparative Example 1: Preparation of Reference UV-Curable Coating

[0067] A reference UV-curable coating was prepared according to the method of Example 1, except that the modified acrylate resin A1 was replaced by the same weight of difunctional polyurethane acrylate resin Trust 7116 (viscosity of 8500 cps at 25°C), and all other conditions were the same as in Example 1, denoted as DB1.

[0068] Comparative Example 2: Preparation of Reference UV-Curable Coating

[0069] A reference UV-curable coating was prepared according to the method of Example 2, except that ethoxylated bisphenol A diacrylate was replaced with the same amount of dipropylene glycol diacrylate (a common difunctional acrylate monomer) by weight. All other conditions were the same as in Example 2, and this coating was designated as DB2.

[0070] Preparation of reference UV-curable coating in Comparative Example 3

[0071] A reference UV-curable coating was prepared according to the method of Example 3, except that diisopropylcarbodiimide was not added, and all other conditions were the same as in Example 3. This coating is denoted as DB3.

[0072] Test case

[0073] The UV-curable coatings obtained in the above examples and comparative examples were cured using a 395nm wavelength mercury lamp, with a radiation intensity of 3000mJ / cm². 2 After curing, the performance was tested according to the following method, and the results are shown in Table 1.

[0074] (1) Adhesion test: The UV-curable coating was applied to a stainless steel substrate with a thickness of 30±5μm. After curing under the above conditions, the adhesion was tested using the cross-cut adhesion test: 6×6 1mm×1mm squares were drawn on the surface of the sample with a sharp knife, and tape was attached to the center of the formed squares. Then, the tape was gently pulled off, and the phenomenon of coating peeling was observed. The following criteria were used to determine the adhesion:

[0075] 5B - The cut edges are completely smooth, with no peeling at the grid edges and intersections;

[0076] 4B - Small pieces peel off at the intersection of the cuts, and the actual damage within the gridded area does not exceed 5%;

[0077] 3B - Small pieces of material peel off at the edges and intersections of the cuts; the actual damage within the gridded area is 5% (excluding endpoint values) to 15%.

[0078] 2B - There is extensive peeling at the edges and intersections of the cuts, and the actual damage within the gridded area is 15% (excluding endpoint values) to 35%;

[0079] 1B - Large areas of peeling are observed at the edges and intersections of the cuts, with actual damage within the gridded area ranging from 35% (excluding endpoint values) to 65%.

[0080] 0 - Some squares have partially or completely peeled off, and the actual damage within the grid area is greater than 65%.

[0081] (2) Water contact angle test: The UV-curable coating was applied to a stainless steel substrate with a thickness of 30±5μm. After curing under the above conditions, the water contact angle of the coating was tested using a water contact angle tester.

[0082] (3) Water vapor transmission rate: According to GB / T1037-88 "Test method for water vapor permeability of plastic films and sheets - cup method", the coating cured under the above conditions was made into a disc corresponding to the cup ring. The water vapor transmission rate (g / m³) was tested over 24 hours at a temperature of 23±0.6℃ and a relative humidity of 90±2%. 2 • 24h) and record the data.

[0083] (4) Acid resistance test: The UV-curable coating is applied to a stainless steel substrate with a thickness of 30±5μm. After curing under the above conditions, it is immersed in 0.1N sulfuric acid at room temperature for 48h. Then, observe whether the coating surface deforms, bubbles or peels off.

[0084] (5) Alkali resistance test: The UV-curable coating is applied to a stainless steel substrate with a thickness of 30±5μm. After curing under the above conditions, it is immersed in 0.1N potassium hydroxide at room temperature for 48h. The coating surface is observed to see if it is deformed (deformation includes surface wrinkling and unevenness and blistering). At the same time, its adhesion is tested.

[0085] (6) Waterproof performance test: The UV-curable coating was applied to a stainless steel substrate with a thickness of 30±5μm. After curing under the above conditions, it was placed in the ESPEC constant temperature and humidity chamber. The temperature and humidity were set at 25℃@95%RH. After 500h, 750h, 1000h, 1250h and 1500h respectively, the samples were taken out and the coating surface was observed to see if deformation occurred (deformation includes surface wrinkling and unevenness and blistering on the coating surface. As long as the coating surface morphology shows the above situation, regardless of the severity of the situation, it indicates that the coating surface has been deformed). At the same time, its adhesion was tested.

[0086] Table 1

[0087]

[0088] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A UV-curable coating, characterized in that, The UV-curable coating is composed of a modified acrylate resin in a mass ratio of 1:(0.5~2.5):(0.3~2):(0.02~0.25):(0.002~0.1):(0~0.1), a monofunctional diluent, a polyfunctional diluent, a photoinitiator, a carbodiimide anti-hydrolysis agent, and optional additives; the mass ratio of the monofunctional diluent to the polyfunctional diluent is 1:(0.3~1.5); the polyfunctional diluent is selected from at least one of ethoxylated bisphenol A diacrylate, ethoxylated bisphenol A dimethacrylate, and ethoxylated trimethylolpropane triacrylate; the monofunctional diluent is a monofunctional acrylate monomer; the modified acrylate resin has a viscosity of 1000~25000 cps at 25°C; the modified acrylate resin has a structure as shown in formula (1). Equation (1) In formula (1), R1is a group derived from a diisocyanate, R2is a C1-C4 alkylene group, R3is a C1-C4 alkylene group, R4is H or a methyl group, and n is an integer from 1 to 10. 10 In formula (1), R1is a group derived from a diisocyanate, R2is a C1-C4 alkylene group, R3is a C1-C4 alkylene group, R4is H or a methyl group, and n is an integer from 1 to 10.

2. The UV-curable coating according to claim 1, characterized in that, The modified acrylate resin has a content of 20-40 parts by weight, the monofunctional diluent has a content of 25-45 parts by weight, the polyfunctional diluent has a content of 15-35 parts by weight, the photoinitiator has a content of 1-5 parts by weight, the carbodiimide anti-hydrolysis agent has a content of 0.1-2 parts by weight, and the additives have a content of 0-2 parts by weight.

3. The UV-curable coating according to claim 1 or 2, characterized in that, The modified acrylate resin was prepared by the following method: S1. A mixture of diisocyanate and diamine is subjected to an addition reaction to obtain a polyurea prepolymer with isocyanate double-terminated ends; S2. The polyurea prepolymer obtained in step S1 and the hydroxyl-terminated acrylate are subjected to a capping reaction in the presence of a polymerization inhibitor and an initiator to obtain a modified acrylate resin.

4. The UV-curable coating according to claim 3, characterized in that, The molar ratio of the diisocyanate to the diamine is (1.1~1.3):

1.

5. The UV-curable coating according to claim 3, characterized in that, The amount of the terminal hydroxyl acrylate used should be such that the NCO groups in the reaction system are substantially completely reacted.

6. The UV-curable coating according to claim 3, characterized in that, The amount of the polymerization inhibitor added is 0.02~0.04 wt% of the total amount of the reaction raw materials.

7. The UV-curable coating according to claim 3, characterized in that, The amount of the initiator added is 0.1 to 0.5 wt% of the total amount of the reaction raw materials.

8. The UV-curable coating according to claim 3, characterized in that, The diisocyanate is selected from at least one of toluene diisocyanate, norbornene diisocyanate, isophorone diisocyanate, isophenyl diisocyanate, dicyclohexylmethane-4,4-diisocyanate, pentamethylene diisocyanate, and hexamethylene diisocyanate.

9. The UV-curable coating according to claim 3, characterized in that, The diamine is selected from at least one of ethylenediamine, 1,2-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, and 1,10-decanediamine.

10. The UV-curable coating according to claim 3, characterized in that, The hydroxyl-terminated acrylate is selected from at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate.

11. The UV-curable coating according to claim 1, characterized in that, The monofunctional acrylate monomer is selected from at least one of glycidyl acrylate, glycidyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, 3,3,5-trimethylcyclohexyl acrylate, ethoxyethyl acrylate, isooctyl acrylate, 4-hydroxycyclohexyl methacrylate, tetrahydrofuran acrylate, and isobornyl acrylate.

12. The method for preparing the ultraviolet-curable coating according to any one of claims 1 to 11, characterized in that, The preparation method includes: mixing and stirring modified acrylate resin, monofunctional diluent, polyfunctional diluent, photoinitiator, carbodiimide anti-hydrolysis agent and optional additives evenly, and then discharging the material in the dark to obtain a UV-curable coating.

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