An anti-fogging UV coating, an anti-fogging coating layer and a preparation method and application thereof

Abstract

This invention belongs to the field of UV coating technology, specifically relating to an anti-fog UV coating, an anti-fog coating layer, its preparation method, and its application. The anti-fog UV coating contains a polyurethane acrylate resin in a mass ratio of 1:(0.25~1.25):(0.25~1.25):(0.075~0.3):(0.05~0.4):(0.025~0.25):(0~1.5):(0~0.05), a monofunctional diluent, a polyfunctional diluent, a modified thiol polymer, nanoparticles, a photoinitiator, and optional solvents and additives; the modified thiol polymer is a thiol polymer with mercapto-terminated groups obtained by reacting a hydrophilic oligomeric diol and a polyisocyanate with a polythiol compound; the nanoparticles are nano-silica sol and / or mesoporous silica. The key to this invention lies in the introduction of modified thiol polymers and nanoparticles with specific molecular structures, which can improve the hardness, adhesion and other properties of the cured coating surface. At the same time, the UV coating also has good hydrophilicity and good anti-fogging effect.

Description

Technical Field

[0001] This invention belongs to the field of UV coating technology, specifically relating to an anti-fog UV coating, an anti-fog coating layer, its preparation method, and its application. Background Technology

[0002] UV curing technology refers to the process of using ultraviolet light irradiation to convert the photoinitiator in liquid UV materials into free radicals or cations, causing the polymer materials containing active functional groups to polymerize rapidly and achieve curing within seconds. It has the advantage of rapid curing and drying that water-based coatings do not have, which can effectively shorten the construction cycle and is widely used in various fields.

[0003] However, since most UV curing processes are carried out in the air, the oxygen in the air competes with monomers for free radicals, resulting in a significant inhibition of polymerization. This leads to poor curing on the coating surface, affecting the long-term stability of the coating and potentially impacting its hardness, gloss, and scratch resistance. Furthermore, most existing UV coating materials use polyurethane acrylate oligomer resins as the main component, resulting in a water contact angle generally exceeding 70°, which fails to provide anti-fogging effects. Therefore, current UV coatings have shortcomings in terms of curing performance and anti-fogging properties, exhibiting certain limitations. Summary of the Invention

[0004] Firstly, the purpose of this invention is to address the shortcomings of existing UV coating materials in terms of photocuring performance and anti-fogging performance, and to provide an anti-fogging UV coating that combines excellent photocuring performance and anti-fogging performance.

[0005] Specifically, the anti-fog UV coating contains polyurethane acrylate resin in a mass ratio of 1:(0.25~1.25):(0.25~1.25):(0.075~0.3):(0.05~0.4):(0.025~0.25):(0~1.5):(0~0.05), a monofunctional diluent, a polyfunctional diluent, a modified thiol polymer, nanoparticles, a photoinitiator, and optional solvents and additives; the modified thiol polymer is a thiol polymer with thiol-terminated groups obtained by reacting a hydrophilic oligomeric diol and a polyisocyanate with a polythiol compound; the modified thiol polymer has the structure shown in formula (1); the nanoparticles are inorganic nano silica sol and / or mesoporous silica;

[0006]

[0007] In formula (1), R1 is a group derived from a hydrophilic oligomeric diol and whose side chain includes at least one hydroxyl group, R2 is a group derived from a polyisocyanate, R3 is a group derived from a polythiol compound, and n is an integer from 1 to 7.

[0008] Secondly, the present invention provides a method for preparing the above-mentioned anti-fog UV coating, the method comprising stirring and mixing polyurethane acrylate resin, monofunctional diluent, polyfunctional diluent, modified thiol polymer, nanoparticles, photoinitiator, and optional solvents and additives to obtain the anti-fog UV coating.

[0009] Thirdly, the present invention provides an anti-fog coating, which is prepared by applying and curing the above-mentioned anti-fog UV coating.

[0010] Fourthly, the present invention also provides the application of the above-mentioned anti-fog UV coatings and / or anti-fog coatings in products with anti-fog requirements.

[0011] The key to this invention lies in preparing an anti-fogging UV coating by compounding a modified thiol polymer with a specific molecular structure, nanoparticles, polyurethane acrylate resin, monofunctional diluent, polyfunctional diluent, photoinitiator, and optional solvents and additives in a certain proportion. On the one hand, because the molecular chain of the modified thiol polymer contains thiol groups, it can effectively inhibit oxygen inhibition during coating curing, solve the problem of poor coating curing, and improve the hardness, adhesion, and other properties of the cured coating surface. On the other hand, due to the introduction of nanoparticles, a micro-nano structure is formed on the surface of the cured coating. The presence of the micro-nano structure allows water vapor to first penetrate and fill the micro-nano structure, and the remaining water vapor then spreads on the surface. At the same time, because the molecular chain of the modified thiol polymer contains a large number of hydrophilic groups such as hydroxyl and ester groups, the surface of the cured coating has a low water contact angle, which improves the hydrophilicity of the surface of the cured coating. This allows water vapor to spread on the coating surface to form a transparent water film, achieving an anti-fogging effect. Therefore, the anti-fog UV coating provided by this invention not only has good photocuring performance and good adhesion and hardness on the cured coating surface, but also has a good anti-fog effect. Moreover, the preparation process is simple and it can be widely used in products with anti-fog requirements. Detailed Implementation

[0012] The anti-fog UV coating provided by this invention contains polyurethane acrylate resin, a monofunctional diluent, a polyfunctional diluent, a modified thiol polymer, nanoparticles, a photoinitiator, and optional solvents and additives. The mass ratio of the polyurethane acrylate resin to the monofunctional diluent is 1:(0.25–1.25), such as 1:0.25, 1:0.5, 1:0.8, 1:1, 1:1.1, 1:1.25, or any value between them. The mass ratio of the polyurethane acrylate resin to the polyfunctional diluent is 1:(0.25–1.25), such as 1:0.25, 1:0.5, 1:0.8, 1:1, 1:1.1, 1:1.25, or any value between them. The mass ratio of the polyurethane acrylate resin to the modified thiol polymer is 1:(0.075–0.3), such as 1:0.075, 1:0.08, 1:0.1, 1:0.15, 1:0.2, 1:0.25, 1:0.3, or any value between them. The mass ratio of the polyurethane acrylate resin to the nanoparticles is 1:(0.05–0.4), such as 1:0.05, 1:0.08, 1:0.1, 1:0.2, 1:0.3, 1:0.4, or any value between them. The mass ratio of the polyurethane acrylate resin to the photoinitiator is 1:(0.025–0.25), such as 1:0.025, 1:0.05, 1:0.08, 1:0.1, 1:0.15, 1:0.2, 1:0.25, or any value between them. The mass ratio of the polyurethane acrylate resin to the solvent is 1:(0-1.5), such as 1:0, 1:0.2, 1:0.5, 1:0.8, 1:1, 1:1.2, 1:1.5, or any value between them. The mass ratio of the polyurethane acrylate resin to the additive is 1:(0-0.05), such as 1:0, 1:0.01, 1:0.02, 1:0.03, 1:0.04, 1:0.05, or any value between them.

[0013] The modified thiol polymer is a thiol polymer with thiol-terminated ends, obtained by reacting a hydrophilic oligomer diol and a polyisocyanate with a polythiol compound. The modified thiol polymer has the structure shown in formula (1);

[0014]

[0015] In formula (1), R1 is a group derived from a hydrophilic oligomeric diol with at least one hydroxyl group in its side chain, R2 is a group derived from a polyisocyanate, R3 is a group derived from a polythiol compound, and n is an integer from 1 to 7, such as 1, 2, 3, 4, 5, 6, 7, etc. The functionality of the polythiol compound is not limited to the trifunctionality shown in formula (1) and can be greater than trifunctionality. When the functionality of the polythiol compound is greater than trifunctionality, R3 contains a thiol group.

[0016] The nanoparticles are nano-silica sol and / or mesoporous silica. The average particle size of the nano-silica sol is preferably 1–100 nm, such as 1 nm, 4 nm, 10 nm, 20 nm, 42 nm, 50 nm, 80 nm, 100 nm, or any value between them. The term "nano-silica" refers to nanoparticles consisting solely of silica or core-shell structured nanoparticles having a silica core and a protective silica shell. The mesoporous silica is preferably spherical, with an average particle size preferably 50–150 nm, such as 50 nm, 75 nm, 100 nm, 120 nm, 150 nm, or any value between them.

[0017] In this invention, the content of the polyurethane acrylate resin is preferably 20-40 parts by weight, such as 20, 22, 25, 30, 32, 35, 38, 40 parts by weight or any value between them. The content of the monofunctional diluent is preferably 10-25 parts by weight, such as 10, 12, 15, 18, 20, 22, 25 parts by weight or any value between them. The content of the polyfunctional diluent is preferably 10-25 parts by weight, such as 10, 12, 15, 18, 20, 22, 25 parts by weight or any value between them. The content of the modified thiol polymer is preferably 3-6 parts by weight, such as 3, 4, 5, 6 parts by weight or any value between them. The content of the nanoparticles is preferably 2-8 parts by weight, such as 2, 3, 4, 5, 6, 7, 8 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 solvent content is preferably 0 to 30 parts by weight, such as 0, 5, 10, 12, 15, 18, 20, 22, 25, 28, 30 parts by weight or any value between them. The additive content is preferably 0 to 1 part by weight, such as 0, 0.1, 0.2, 0.5, 0.8, 1 part by weight or any value between them. Specifically, the additive preferably includes a leveling agent and a defoamer. The leveling agent content is preferably 0 to 0.5 parts by weight, such as 0, 0.1, 0.2, 0.3, 0.4, 0.5 parts by weight or any value between them. The defoamer content is preferably 0 to 0.5 parts by weight, such as 0, 0.1, 0.2, 0.3, 0.4, 0.5 parts by weight or any value between them.

[0018] In this invention, the polyurethane acrylate resin can be any existing polyurethane with acrylic groups, which can be commercially available or prepared using existing methods. In a preferred embodiment, the functionality of the polyurethane acrylate resin is not less than 2, such as 2, 3, 4, 5, 6, or any other integer greater than 2. The viscosity of the polyurethane acrylate resin at 25°C is preferably 2000–15000 cps, such as 2000 cps, 5000 cps, 8000 cps, 10000 cps, 12000 cps, 15000 cps, or any value between them. The polyurethane acrylate resin may be, for example, at least one of the following: EBECRYL 270, EBECRYL 271, EBECRYL 284, EBECRYL 8307, EBECRYL 8254, EBECRYL 8411 from Zhanxin Resin (China) Co., Ltd.; 7210B, 7220F, 7223F, 7224, 7233F, 7295 from Guangdong Hengzhiguang Environmental New Materials Co., Ltd.; and Trust 7116, Trust 7166, and Trust 7128 from Shenzhen Youyang Technology Co., Ltd.

[0019] In this invention, the monofunctional diluent is preferably selected from at least one of hydroxyethyl acrylate (EHA), hydroxyethyl methacrylate (HEMA), hydroxypropyl acrylate (HPA), hydroxypropyl methacrylate (HPMA), 3,3,5-trimethylcyclohexyl acrylate (TMCHA), ethoxyethyl acrylate, isooctyl acrylate (2-EHA), 4-hydroxycyclohexyl methacrylate, tetrahydrofuran acrylate, and isobornyl acrylate (IBOA).

[0020] In this invention, the functionality of the multifunctional diluent is preferably 2 to 6, such as 2, 3, 4, 5, 6, or any value between them. Specific examples of the multifunctional diluent include, but are not limited to, at least one of: dipropylene glycol diacrylate, tripropylene glycol diacrylate, neopentyl glycol diacrylate, propoxylated neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, 1,4-butanediol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, methyl etherified propoxylated pentaerythritol diacrylate, tricyclodecanediethanol diacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, propoxylated glycerol triacrylate, tri(2-hydroxyethyl)isocyanurate triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate.

[0021] In this invention, the modified thiol polymer is preferably prepared by a method comprising the following steps:

[0022] S1. A hydrophilic oligomer diol and a polyisocyanate are subjected to an addition reaction to obtain a prepolymer with isocyanate double-terminated ends;

[0023] S2. The isocyanate-double-terminated prepolymer is subjected to a termination reaction with a polythiol compound in the presence of an initiator to obtain a modified thiol polymer.

[0024] In this invention, the molar ratio of the hydrophilic oligomeric diol to the polyisocyanate is preferably 1:(1.1-1.5), such as 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, or any value between them. The molar ratio of the polyisocyanate to the polythiol compound is preferably 1:(0.5-1.2), such as 1:0.5, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, or any value between them.

[0025] In this invention, the amount of initiator added is preferably 0.1 to 0.25 wt% of the total mass of the reaction raw materials, such as 0.1 wt%, 0.12 wt%, 0.15 wt%, 0.18 wt%, 0.20 wt%, 0.22 wt%, 0.25 wt%, or any value between them. The reaction raw materials include hydrophilic oligomeric diols, polyisocyanates, and polythiols.

[0026] In this invention, the thiol content of the modified thiol polymer is preferably 8-20 wt%, such as 8 wt%, 10 wt%, 12 wt%, 15 wt%, 18 wt%, 20 wt%, or any value between them. The thiol content can be determined according to the method provided in CN201711190623.X, which involves dissolving the sample in acetonitrile solvent, adding an iodine-ethanol solution containing the same mass as the sample, and a KI aqueous solution containing twice the mass of the sample to react with the thiol groups. Finally, the remaining iodine content is determined using a sodium thiosulfate standard solution, thereby calculating the thiol content.

[0027] In this invention, in step S1, the conditions for the addition reaction include a temperature preferably of 80–120°C, such as 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C or any value between them; and a time preferably of 1–5 h, such as 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h or any value between them.

[0028] In this invention, in step S2, the conditions for the end-capping reaction include a temperature preferably of 30 to 60°C, such as 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C or any value between them; and a time preferably of 2 to 10 hours, such as 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours or any value between them.

[0029] In the preparation of the modified thiol polymers described above, isocyanates are sensitive to moisture. Therefore, to ensure the smooth reaction of polyisocyanates with hydrophilic oligomer diols and polythiols, the reaction vessel and reactants need to be dehydrated before the reaction is started, and the reaction should be carried out under an inert atmosphere. Specifically, the reaction vessel can be dried at 130–150°C for 2–4 hours. The reactants can be dehydrated using methods such as heating and vacuuming, freeze-drying, molecular sieve dehydration, or glove box ventilation. The polymerization reaction is carried out under an inert atmosphere by introducing a chemical inert gas into the reaction vessel, evacuating the vessel, and then filling it with an inert gas to maintain the reaction system under this atmosphere. Specifically, the chemical inert gas can be nitrogen or argon, preferably nitrogen.

[0030] In one specific embodiment, the preparation method of the above-mentioned polythiol can be as follows: heating a hydrophilic oligomeric diol to 100-130°C and dehydrating it under vacuum for 0.5-2 hours, cooling it to 80-120°C, adding the dehydrated polyisocyanate, and stirring the reaction under an inert gas atmosphere for 1-5 hours to obtain a prepolymer with isocyanate double-terminated ends; continuing to add the dehydrated polythiol compound and initiator, stirring the reaction under 30-60°C for 2-10 hours, and terminating the reaction by controlling the thiol content at 8-20 wt%.

[0031] In this invention, the polyisocyanate can be a compound containing two or more isocyanate groups, and specific examples include, but are not limited to, at least one of toluene diisocyanate, norbornene diisocyanate, isophorone diisocyanate, m-phenylenedimethyl diisocyanate, 4,4-dicyclohexylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 4,4,4-triphenylmethane triisocyanate and L-lysine triisocyanate, more preferably pentamethylene diisocyanate and / or hexamethylene diisocyanate.

[0032] In this invention, the polythiol compound is preferably a trifunctional polythiol compound and / or a tetrafunctional polythiol compound, and specific examples include, but are not limited to, at least one of: trimethylolpropane tris(3-mercaptoacetic acid), trimethylolpropane tris(3-mercaptopropionate), trimethylolpropane tris(3-mercaptobutyrate), pentaerythritol tetra(mercaptoacetic acid), pentaerythritol tetra(3-mercaptopropionic acid), and pentaerythritol tetra(3-mercaptobutyrate).

[0033] In this invention, the initiator is a type of compound that catalyzes the reaction between hydroxyl groups and isocyanate groups, which is conventionally used in the prior art and is not particularly limited thereto. The initiator is preferably an organotin compound, and specific examples include, but are not limited to, at least one of: stannous isoate, trimethyltin chloride, dibutyltin dilaurate, dibutyltin dichloride, and methyltin trichloride, more preferably dibutyltin dilaurate and / or dibutyltin dichloride.

[0034] In this invention, the hydrophilic oligomeric diol is preferably obtained by dehydration condensation polymerization of a hydroxyl-substituted diacid with a diol. The hydroxyl value of the hydrophilic oligomeric diol is preferably 90–260 mg KOH / g, such as 90, 100, 120, 160, 200 mg, 230, 260 mg KOH / g or any value between these values. The number-average molecular weight of the hydrophilic oligomeric diol is preferably 500–3000 g / mol, such as 500 g / mol, 800 g / mol, 1000 g / mol, 1500 g / mol, 2000 g / mol, 2500 g / mol, 3000 g / mol or any value between these values.

[0035] In this invention, the molar ratio of the hydroxylated dicarboxylic acid to the diol is preferably 1:(1.5 to 2.5), such as 1:1.5, 1:1.8, 1:1.9, 1:2, 1:2.2, 1:2.5 or any value between them.

[0036] In this invention, the hydroxylated dicarboxylic acid preferably has the structure shown in formula (2). The hydroxylated dicarboxylic acid is preferably at least one selected from tartaric acid, tartaric acid, 2-hydroxysuccinic acid, 3-hydroxyglutaric acid, 2-hydroxyadipic acid, tetrahydroxyadipic acid, and 3-hydroxyoctanoic acid.

[0037]

[0038] In formula (2), R4 is a C1-C6 hydroxyl-substituted alkylene group, such as at least one of -CHOH-, -CH2CHOH-, -(CHOH)2-, -(CH2)2CHOH-, -(CH2)3CHOH-, -(CHOH)4-, and -(CH2)5CHOH-, wherein the substituted hydroxyl group can be at any position of the alkylene group, but is limited to the position shown in the example. Considering the availability of starting materials and the ease of reaction, the hydroxyl-substituted dicarboxylic acid is more preferably tartaric acid.

[0039] In this invention, the diol is preferably at least one selected from ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, diethylene glycol, 1,5-pentanediol, neopentanediol, 3-methyl-1,5-pentanediol, and 1,6-hexanediol.

[0040] In the preparation of the above-mentioned hydrophilic oligomeric diol, the dehydration polycondensation reaction is more preferably carried out in the presence of a catalyst. The amount of catalyst added is preferably 0.2–1 wt% of the total mass of the hydroxylated diacid and the diol, such as 0.2 wt%, 0.5 wt%, 0.8 wt%, 1 wt%, or any value between therewith. The catalyst is preferably at least one selected from sodium bisulfate, p-toluenesulfonic acid, concentrated sulfuric acid, and concentrated hydrochloric acid.

[0041] In one specific embodiment, the preparation method of the hydrophilic oligomeric diol can be as follows: A hydroxyl-substituted diacid, diol I, and a catalyst are heated to 60–80°C under inert gas protection and stirred for 1–5 hours. During the heating process, the temperature of the top of the condenser is controlled to be below 100°C. During this period, the reaction system is evacuated for approximately 5–10 minutes every 0.5 hours to remove small molecule byproducts, allowing the reaction to reach equilibrium until the weight of the reaction system shows no significant change (the mass of the extracted small molecules essentially no longer increases). Diol II is added and stirring continues for 0.5–2 hours. Then, the temperature is raised to 130–180°C and evacuated to a vacuum degree of not less than 0.095 MPa. The reaction continues for 0.5–1 hour, and the hydroxyl value is tested to reach 90–260 mg KOH / g, thus obtaining the hydrophilic oligomeric diol. The molar ratio of the hydroxylated diacid to diol I can be 1:(1.2 to 1.8), such as 1:1.2, 1:1.4, 1:1.6, 1:1.8 or any value between them; the molar ratio of the hydroxylated diacid to diol II can be 1:(0.3 to 0.6), such as 1:0.3, 1:0.4, 1:0.5, 1:0.6 or any value between them.

[0042] The present invention does not specifically limit the type of photoinitiator, and can be any existing compound that can generate free radicals under visible or ultraviolet light irradiation to initiate monomer polymerization. From the perspective of raw material availability, the photoinitiator is preferably at least one selected from Irgacure 184 (1-hydroxycyclohexylphenyl ketone), Irgacure 369 (2-dimethylamino-2-benzyl-1-[4-(4-morpholinyl)phenyl]-1-butanone), Irgacure 907 (2-methyl-2-(4-morpholinyl)-1-[4-(methylthio)phenyl]-1-propanone), Irgacure 1173 (2-hydroxy-2-methyl-1-phenylpropanone), Irgacure 2959 (2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone), TPO (2,4,6-trimethylbenzoyl-diphenylphosphine oxide) and TPO-L (ethyl 2,4,6-trimethylbenzoylphenylphosphonate).

[0043] This invention does not specifically limit the type of solvent. The solvent in this invention primarily functions as an inert liquid medium, ensuring a more uniform mixing of the various raw materials added during the preparation of photocurable coatings containing hydrophilic structures. The solvent can be exemplary selected from at least one of the following: ethanol, isopropanol, n-butanol, propylene glycol methyl ether acetate, tetrahydrofuran, toluene, propylene glycol monoalkyl ether, propylene glycol alkyl ether acetate, cyclopentanone, butyl acetate, methyl isobutyl ketone, n-butanone, 4-methyl-2-pentanone, cyclohexanone, 2-heptanone, γ-butyrolactone, ethylene glycol monoethyl ether acetate, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, butyrolactone, dimethylformamide, and dimethylacetamide.

[0044] In this invention, the leveling agent can be any known substance capable of improving the leveling performance of coatings, and can be selected, for example, from at least one of BYK307, BYK333, BYK358, BYK361, BYK366 from BYK Corporation, and EFKA3600, EFKA3883, and EFKA3886 from Efka Corporation of the Netherlands.

[0045] In this invention, the defoamer can be any known substance capable of eliminating or reducing bubbles in coatings, and can be exemplary selected from at least one of BYK 020, BKY054, BYK352, BYK354, BYK357, BKY1790 and BKY1794 from BYK Corporation.

[0046] The method for preparing the anti-fog UV coating provided by the present invention includes stirring and mixing polyurethane acrylate resin, monofunctional diluent, polyfunctional diluent, modified thiol polymer, nanoparticles, photoinitiator, and optional solvents and additives to obtain the anti-fog UV coating.

[0047] In a preferred embodiment, the preparation method includes: weighing polyurethane acrylate resin, monofunctional diluent, polyfunctional diluent, and modified thiol polymer and adding them to a dual planetary hybrid reactor, stirring for 1-3 hours; then adding a photoinitiator and optionally a solvent and additives to the reactor, stirring for 1-2 hours, followed by vacuum degassing, and finally discharging and sealing the product. Furthermore, white light must be strictly avoided throughout the entire stirring process.

[0048] The present invention also provides an anti-fog coating, which is prepared by applying and curing the above-mentioned anti-fog UV coating. The thickness of the anti-fog coating is preferably 5 to 35 μm, such as 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm or any value between them.

[0049] In this invention, the method for preparing the anti-fog coating is as follows: applying an anti-fog UV coating to the surface of a substrate, pre-baking the coated substrate, and then UV curing it to obtain the anti-fog coating. The pre-baking temperature is preferably 60–100°C, such as 60°C, 70°C, 80°C, 90°C, 100°C, or any value between them; the pre-baking time is preferably 5–20 min, such as 5 min, 8 min, 10 min, 12 min, 15 min, 18 min, 20 min, or any value between them.

[0050] The present invention will be described in detail below through specific embodiments.

[0051] The raw materials used in the following examples and comparative examples are as follows: polyurethane acrylate resin, purchased from Shenzhen Youyang Technology Co., Ltd., brand name Trust 7128, functionality = 2, color = 2, viscosity at 25°C 15000cps; polyurethane acrylate resin, purchased from Zhanxin Resin (China) Co., Ltd., brand name EBECREL 8411, functionality = 2, color = 1, viscosity at 25°C 4000cps; aliphatic polyurethane acrylate resin, purchased from Guangdong Hengzhiguang Environmental Protection New Materials Co., Ltd., brand name 7224, functionality = 2, color = 0.6, viscosity at 25°C 8250cps;

[0052] Nano-sized silica sol, purchased from Nalco Chemical Company, USA, grade NALCO1115, with an average particle size of 4 nm; spherical mesoporous silica, purchased from Nanjing Xianfeng Nanomaterials Technology Co., Ltd., grade 104855, with an average particle size of 150 nm; spherical mesoporous silica, purchased from Nanjing Xianfeng Nanomaterials Technology Co., Ltd., grade 104435, with an average particle size of 75 nm; spherical mesoporous silica, purchased from Nanjing Xianfeng Nanomaterials Technology Co., Ltd., grade 104333, with an average particle size of 50 nm.

[0053] Preparation Example 1: Preparation of Modified Thiol Polymers

[0054] (1) A four-necked flask equipped with a magnetic stirrer, thermometer, N2 inlet pipe, and air-cooled condenser was placed in a covered resistance heater. 150.00 g (1 mol) tartaric acid, 114.00 g (1.5 mol) 1,3-propanediol, and 0.80 g (0.27 wt%) concentrated sulfuric acid were added and stirred for 2 h under nitrogen protection. The flask temperature was controlled at 70 °C for dehydration polycondensation reaction. During the heating process, the top temperature of the condenser was controlled to be below 100 °C. During this period, the reaction system was evacuated for about 5 min every 0.5 h to remove small molecule byproducts and to make the reaction reach equilibrium until the weight of the reaction system no longer changed significantly. 30.40 g (0.3 mol) neopentyl glycol was added and the reaction was continued for 1 h. Then, the temperature was gradually increased to 150 °C and the vacuum degree was ≥0.095 MPa. The reaction was continued until the hydroxyl value reached 142 mg. A hydrophilic oligomer diol with a molecular weight of 800 g / mol was prepared by using KOH / g, and it is designated as I.

[0055] (2) 160.00 g (0.2 mol) of hydrophilic oligomer diol I was added to a three-necked flask equipped with a stirrer, heated to 120 °C and dehydrated under vacuum for 1 h, cooled to 90 °C, and 50.40 g (0.3 mol) of hexamethylene diisocyanate was added in two portions and stirred for 2 h under an inert gas atmosphere; then 79.70 g (0.2 mol) of trimethylolpropane tris(3-mercaptopropionate) and 0.35 g (0.12 wt%) of dibutyltin dichloride catalyst were added and reacted at 40 °C for 3.5 h. The mercapto content was detected to be about 16 wt%, and the reaction was terminated to obtain a viscous liquid. This viscous liquid is the modified thiol polymer, denoted as A-1.

[0056] Preparation Example 2: Preparation of Modified Thiol Polymers

[0057] This preparation example prepares a modified thiol polymer according to the method provided in Preparation Example 1. The difference is that the raw materials, ingredients, and reaction conditions used in step (2) are different. Specifically, 192.00 g (0.24 mol) of diol I is added to a three-necked flask equipped with a stirrer, heated to 130°C and dehydrated under vacuum for 0.6 h, cooled to 110°C, and 78.60 g (0.3 mol) of dicyclohexylmethane-4,4-diisocyanate is added. The mixture is stirred for 3 h under an inert gas atmosphere. Then, 73.40 g (0.15 mol) of pentaerythritol tetrakis(3-mercaptopropionic acid) and 0.55 g (0.16 wt%) of dibutyltin dichloride catalyst are added. The mixture is reacted at 50°C for 4 h. The thiol content is detected to be around 19 wt%, and the reaction is terminated to obtain a viscous liquid. This viscous liquid is the modified thiol polymer, denoted as A-2.

[0058] Preparation Example 3: Preparation of Modified Thiol Polymers

[0059] This preparation example prepares a modified thiol polymer according to the method provided in Preparation Example 1. The difference is that the raw materials, ingredients, and reaction conditions used in step (2) are different. Specifically, 192.00 g (0.24 mol) of diol I is added to a three-necked flask equipped with a stirrer, heated to 120°C and dehydrated under vacuum for 1 h, cooled to 100°C, and 71.14 g (0.32 mol) of isophorone diisocyanate is added. The mixture is stirred for 3.5 h under an inert gas atmosphere. Then, 79.70 g (0.2 mol) of trimethylolpropane tris(3-mercaptopropionate) and 0.85 g (0.25 wt%) of dibutyltin dilaurate catalyst are added. The mixture is reacted at 45°C for 4 h. The thiol content is detected to be around 13 wt%. The reaction is then terminated to obtain a viscous liquid, which is polythiol, denoted as A-3.

[0060] Preparation Example 4: Preparation of Modified Thiol Polymers

[0061] (1) A four-necked flask equipped with a magnetic stirrer, thermometer, N2 inlet pipe, and air-cooled condenser was placed in a covered resistance heater. 148.11 g (1 mol) of 3-hydroxyglutaric acid, 93.11 g (1.5 mol) of ethylene glycol, and 0.80 g (0.27 wt%) of concentrated hydrochloric acid were added and stirred for 2 h under nitrogen protection. The temperature of the flask was controlled at 70 °C for dehydration polycondensation reaction. During the heating process, the temperature of the top of the condenser was controlled to be below 100 °C. During this period, the reaction system was evacuated for about 5 min every 0.5 h to remove small molecule byproducts and to make the reaction reach equilibrium until there was no significant change in the weight of the reaction system. 30.40 g (0.3 mol) of neopentyl glycol was added and the reaction was continued for 1 h. Then the temperature was gradually increased to 150 °C and the vacuum degree was ≥0.095 MPa. The reaction was continued until the hydroxyl value reached 92 mg. A hydrophilic oligomer diol with a molecular weight of 1100 g / mol was prepared by using KOH / g, and it is designated as II.

[0062] (2) 160.00 g (0.2 mol) of hydrophilic oligomer diol II was added to a three-necked flask equipped with a stirrer, heated to 120 °C and dehydrated under vacuum for 1 h, cooled to 90 °C, and 50.40 g (0.3 mol) of hexamethylene diisocyanate was added in two portions and stirred for 2 h under an inert gas atmosphere; then 79.70 g (0.2 mol) of trimethylolpropane tris(3-mercaptopropionate) and 0.35 g (0.12 wt%) of dibutyltin dichloride catalyst were added, and the reaction was carried out at 40 °C for 3.5 h. The mercapto content was detected to be about 16 wt%, and the reaction was terminated to obtain a viscous liquid. This viscous liquid is the modified thiol polymer, denoted as A-4.

[0063] Preparation Example 5: Preparation of Modified Thiol Polymers

[0064] (1) A four-necked flask equipped with a magnetic stirrer, thermometer, N2 inlet pipe, and air-cooled condenser was placed in a covered resistance heater. 210.00 g (1 mol) of tetrahydroxyadipic acid, 114.00 g (1.5 mol) of 1,3-propanediol, and 0.80 g (0.27 wt%) of p-toluenesulfonic acid were added and stirred for 2 h under nitrogen protection. The temperature of the flask was controlled at 70 °C for the dehydration condensation reaction. During the heating process, the temperature of the top of the condenser was controlled to be below 100 °C. During this period, the reaction system was evacuated for about 5 min every 0.5 h to remove small molecule byproducts. The reaction was brought to equilibrium until there was no significant change in the weight of the reaction system. 30.40 g (0.3 mol) of neopentyl glycol was added and the reaction was continued for 1 h. Then the temperature was gradually increased to 150 °C and the vacuum degree was ≥0.095 MPa. The reaction was continued until the hydroxyl value reached 250 mg. KOH / g was used to prepare a hydrophilic oligomer diol with a molecular weight of 1500 g / mol, denoted as III;

[0065] (2) 160.00 g (0.2 mol) of hydrophilic oligomer diol III was added to a three-necked flask equipped with a stirrer, heated to 120 °C and dehydrated under vacuum for 1 h, cooled to 90 °C, and 46.26 g (0.3 mol) of pentamethylene diisocyanate was added in two portions and stirred for 2 h under an inert gas atmosphere; then 73.40 g (0.15 mol) of pentaerythritol tetrakis(3-mercaptopropionic acid) and 0.35 g (0.12 wt%) of dibutyltin dichloride catalyst were added and reacted at 40 °C for 3.5 h. The mercapto content was detected to be about 16 wt%, and the reaction was terminated to obtain a viscous liquid. This viscous liquid is the modified thiol polymer, denoted as A-5.

[0066] Example 1: Preparation of Anti-fog UV Coating

[0067] 20 parts of polyurethane acrylate resin (Trust 7128), 25 parts of tetrahydrofuran acrylate, 10 parts of pentaerythritol triacrylate, and 3 parts of modified thiol polymer A-1 were sequentially added to a dual planetary hybrid reactor and stirred for 2 hours. Then, 30 parts of propylene glycol monoalkyl ether, 7.5 parts of nano silica sol (NALCO1115), 2.5 parts of Irgacure 907, 1.5 parts 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 anti-fog UV coating was obtained.

[0068] Example 2: Preparation of Anti-fog UV Coating

[0069] 40 parts of polyurethane acrylate resin (EBECRYL 8411), 10 parts of hydroxypropyl acrylate, 25 parts of neopentyl glycol diacrylate, and 6 parts of modified thiol polymer A-2 were sequentially added to a dual planetary hybrid reactor and stirred for 2 hours. Then, 10 parts of cyclopentanone, 4.5 parts of spherical mesoporous silica (104855), 1.2 parts of Irgacure 1173, 3 parts of TPO, 0.2 parts of EFKA3883, and 0.1 parts of BKY1790 were added to the reactor and stirred for 1.5 hours. After vacuum degassing, the anti-fog UV coating was obtained.

[0070] Example 3: Preparation of Anti-fog UV Coating

[0071] 33 parts of polyurethane acrylate resin (7224), 20 parts of isobornyl acrylate, 10 parts of pentaerythritol tetraacrylate, and 4.5 parts of modified thiol polymer A-3 were sequentially added to a double planetary hybrid reactor and stirred for 2 hours. Then, 15 parts of n-butyl ketone, 10 parts of butyl acetate, 3 parts of spherical mesoporous silica (104435), 3 parts of Irgacure 369, 1.2 parts of TPO, 0.1 parts of BYK361, and 0.2 parts of BKY054 were added to the reactor and stirred for 1.5 hours. After vacuum degassing, the anti-fog UV coating was obtained.

[0072] Example 4: Preparation of Anti-fog UV Coating

[0073] 30 parts of polyurethane acrylate resin (Trust 7128), 15 parts of tetrahydrofuran acrylate, 18 parts of pentaerythritol triacrylate, and 5 parts of modified thiol polymer A-4 were sequentially added to a double planetary hybrid reactor and stirred for 2 hours. Then, 20 parts of propylene glycol monoalkyl ether, 7.5 parts of nano silica sol (NALCO1115), 2.5 parts of Irgacure 907, 1.5 parts 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 anti-fog UV coating was obtained.

[0074] Example 5: Preparation of Anti-fog UV Coating

[0075] 25 parts of polyurethane acrylate resin (Trust 7128), 20 parts of tetrahydrofuran acrylate, 10 parts of pentaerythritol triacrylate, and 3 parts of modified thiol polymer A-5 were sequentially added to a dual planetary hybrid reactor and stirred for 2 hours. Then, 30 parts of propylene glycol monoalkyl ether, 7.5 parts of spherical mesoporous silica 104333, 2.5 parts of Irgacure 907, 1.5 parts 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 anti-fog UV coating was obtained.

[0076] Comparative Example 1: Preparation of Reference Anti-fog UV Coating

[0077] The reference anti-fog UV coating was prepared according to the method of Example 1, except that the modified thiol polymer A-1 was replaced with the same amount of trimethylolpropane tris(3-mercaptopropionate) by weight, and the other conditions were the same as in Example 1, to obtain the reference anti-fog UV coating.

[0078] Comparative Example 2: Preparation of Reference Anti-fog UV Coating

[0079] The reference anti-fog UV coating was prepared according to the method of Example 2, except that the spherical mesoporous silica (104855) was replaced with the same amount of cyclopentanone by weight, and the other conditions were the same as in Example 2, to obtain the reference anti-fog UV coating.

[0080] Preparation of the reference anti-fog UV coating in Comparative Example 3

[0081] A reference anti-fog UV coating was prepared according to the method of Example 3, except that modified thiol polymer A-3 and spherical mesoporous silica 104435 were not added, while the other conditions were the same as in Example 3, and the reference anti-fog UV coating was obtained.

[0082] Test case

[0083] The anti-fog UV coatings prepared in the above examples and comparative examples were used to prepare a coating as follows: The anti-fog UV coatings prepared above were coated on the surface of a glass substrate, pre-baked at 90°C for 10 minutes, and then photocured with a mercury lamp with a wavelength of 405 nm, with the radiation intensity controlled at 5000 mJ / cm². 2 A transparent coating with a thickness of 10 μm was obtained. The hydrophilicity, light transmittance, hardness, haze, and adhesion of the prepared transparent coating were tested according to the following methods, and the results are shown in Table 1.

[0084] (1) Hydrophilicity test (water contact angle test)

[0085] The water contact angle of the coating was tested using a water contact angle tester.

[0086] (2) Transmittance test

[0087] The transmittance of the coating was tested using a benchtop spectrophotometer YS6002-M.

[0088] (3) Hardness test

[0089] The test was conducted according to the standard GB / 6739T method: Under a force of 1 kg, a Japanese Mitsubishi pencil of different hardness was used to push and scratch the coating on the substrate surface three times. If the coating surface was undamaged, it was recorded as OK; if there was a slight scratch in one of the three times, it was recorded as NO. The hardness of the pencil at this time was recorded as the coating hardness.

[0090] B = BLACK (darkness), H = HARD (hardness). The higher the B value, the darker and softer the pencil; the higher the H value, the harder the pencil and the lighter the color. Pencils are classified as 10B, 9B, 8B, 7B, 6B, 5B, 4B, 3B, 2B, B, HB, F, H, 2H, 3H, 4H, 5H, 6H, 7H, 8H, 9H, and 10H. 10B is the softest and has the darkest ink, H is relatively hard and has a lighter ink, and 10H is the hardest and has the lightest ink.

[0091] (4) Haze test

[0092] Steam generated by boiling water is sprayed onto the coating surface. After the coating surface cools to room temperature, the haze value before and after coating is measured using a haze meter (haze = diffused transmitted light / transmitted light).

[0093] (5) Adhesion test

[0094] Adhesion test using the cross-cut adhesion test: Use a sharp knife to cut 6×6 1mm×1mm squares on the surface of the sample to be tested. Apply adhesive tape to the center of the formed squares, then gently peel it off and observe the paint peeling phenomenon. Judge the adhesion according to the following standards:

[0095] 5B - The cut edges are completely smooth, with no peeling at the grid edges and intersections;

[0096] 4B - Small pieces peel off at the intersection of the cuts, and the actual damage within the gridded area does not exceed 5%;

[0097] 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%.

[0098] 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%;

[0099] 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%.

[0100] 0 - Some squares have partially or completely peeled off, and the actual damage within the grid area is greater than 65%.

[0101] Table 1

[0102]

[0103] As shown in Example 1 and Comparative Example 1, compared to Comparative Example 1 which used common polythiol compounds as one of the raw materials, Example 1 added a modified thiol polymer with a specific structure, which significantly reduced the water contact angle of the UV coating and improved its anti-fogging performance. As shown in Example 2 and Comparative Example 2, the addition of nanoparticles improved the hydrophilicity of the UV coating, reduced its water contact angle and haze in a water-vapor environment, resulting in good anti-fogging capabilities during application. As shown in Example 3 and Comparative Example 3, the modified thiol polymer with a specific structure not only improved the anti-fogging performance of the UV coating but also increased the hardness and adhesion of the cured coating, i.e., improved the curing performance of the UV coating. In summary, the UV coating provided by this invention, by introducing a modified thiol polymer with a specific molecular structure and nanoparticles, can improve the surface hardness and adhesion of the cured coating, while also exhibiting good hydrophilicity and anti-fogging effects.

[0104] 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. An anti-fog UV coating, characterized in that, The anti-fog UV coating contains polyurethane acrylate resin in a mass ratio of 1:(0.25~1.25):(0.25~1.25):(0.075~0.3):(0.05~0.4):(0.025~0.25):(0~1.5):(0~0.05), a monofunctional diluent, a polyfunctional diluent, a modified thiol polymer, nanoparticles, a photoinitiator, and optional solvents and additives; the modified thiol polymer is a thiol polymer with thiol-terminated groups obtained by reacting a hydrophilic oligomeric diol and a polyisocyanate with a polythiol compound; the modified thiol polymer has the structure shown in formula (1); the nanoparticles are nano-silica sol and / or mesoporous silica; Equation (1), In formula (1), R1 is a group derived from a hydrophilic oligomeric diol and whose side chain includes at least one hydroxyl group, R2 is a group derived from a polyisocyanate, R3 is a group derived from a polythiol compound, and n is an integer from 1 to 7.

2. The anti-fog UV coating according to claim 1, characterized in that, The polyurethane acrylate resin content is 20-40 parts by weight, the monofunctional diluent content is 10-25 parts by weight, the polyfunctional diluent content is 10-25 parts by weight, the modified thiol polymer content is 3-6 parts by weight, the nanoparticle content is 2-8 parts by weight, the photoinitiator content is 1-5 parts by weight, the solvent content is 0-30 parts by weight, and the additive content is 0-1 parts by weight.

3. The anti-fog UV coating according to claim 1, characterized in that, The polyurethane acrylate resin has a functionality of not less than 2 and a viscosity of 2000~15000 cps at 25°C.

4. The anti-fog UV coating according to claim 1, characterized in that, The functionality of the multifunctional diluent is 2 to 6.

5. The anti-fog UV coating according to claim 1, characterized in that, The average particle size of the nano-silica sol is 1~100nm.

6. The anti-fog UV coating according to claim 1, characterized in that, The average particle size of the mesoporous silica is 50~150 nm.

7. The anti-fog UV coating according to claim 1, characterized in that, The modified thiol polymer was prepared using a method comprising the following steps: S1. A hydrophilic oligomer diol and a polyisocyanate are subjected to an addition reaction to obtain a prepolymer with isocyanate double-terminated ends; S2. The isocyanate-double-terminated prepolymer is subjected to a termination reaction with a polythiol compound in the presence of an initiator to obtain a modified thiol polymer.

8. The anti-fog UV coating according to claim 7, characterized in that, The molar ratio of the hydrophilic oligomer diol to the polyisocyanate is 1:(1.1~1.5).

9. The anti-fog UV coating according to claim 7, characterized in that, The molar ratio of the polyisocyanate to the polythiol compound is 1:(0.5~1.2).

10. The anti-fog UV coating according to claim 7, characterized in that, The amount of the initiator added is 0.1 to 0.25 wt% of the total mass of the reaction raw materials.

11. The anti-fog UV coating according to claim 7, characterized in that, The modified thiol polymer has a thiol content of 8-20 wt%.

12. The anti-fog UV coating according to claim 7, characterized in that, The conditions for the addition reaction include a temperature of 80~120℃ and a time of 1~5h.

13. The anti-fog UV coating according to claim 7, characterized in that, The conditions for the end-capping reaction include a temperature of 30~60℃ and a time of 2~10h.

14. The anti-fog UV coating according to claim 7, characterized in that, The hydrophilic oligomeric diol is obtained by dehydration condensation polymerization of a hydroxyl-substituted diacid with a diol. The hydroxyl-substituted dicarboxylic acid has the structure shown in formula (2); Equation (2), In formula (2), R4 is a C1~C6 hydroxyl-substituted alkylene group.

15. The anti-fog UV coating according to claim 7, characterized in that, The hydrophilic oligomer diol has a hydroxyl value of 90~260 mg KOH / g.

16. The anti-fog UV coating according to claim 7, characterized in that, The number average molecular weight of the hydrophilic oligomer diol is 500~3000 g / mol.

17. The anti-fog UV coating according to claim 14, characterized in that, The molar ratio of the hydroxylated dicarboxylic acid to the diol is 1:(1.5~2.5).

18. The anti-fog UV coating according to claim 14, characterized in that, The hydroxylated dicarboxylic acid is selected from at least one of tartaric acid, tartaric acid, 2-hydroxysuccinic acid, 3-hydroxyglutaric acid, 2-hydroxyadipic acid, tetrahydroxyadipic acid, and 3-hydroxyoctanoic acid.

19. The anti-fog UV coating according to claim 14, characterized in that, The diol is selected from at least one of ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, diethylene glycol, 1,5-pentanediol, neopentanediol, 3-methyl-1,5-pentanediol, and 1,6-hexanediol.

20. The anti-fog UV coating according to claim 14, characterized in that, The dehydration polycondensation reaction is carried out in the presence of a catalyst.

21. The anti-fog UV coating according to claim 20, characterized in that, The catalyst is added in an amount of 0.2 to 1 wt% of the total mass of the hydroxylated dicarboxylic acid and diol.

22. The anti-fog UV coating according to claim 20, characterized in that, The catalyst is selected from at least one of sodium bisulfate, p-toluenesulfonic acid, concentrated sulfuric acid, and concentrated hydrochloric acid.

23. The method for preparing the anti-fog UV coating according to any one of claims 1 to 22, characterized in that, The preparation method involves mixing polyurethane acrylate resin, monofunctional diluent, polyfunctional diluent, modified thiol polymer, nanoparticles, photoinitiator, and optional solvents and additives to obtain an anti-fog UV coating.

24. An anti-fog coating, characterized in that, The anti-fog coating is prepared by applying and curing the anti-fog UV coating as described in any one of claims 1 to 22.

25. The application of the anti-fog UV coating according to any one of claims 1 to 22 and / or the anti-fog coating according to claim 24 in products with anti-fog requirements.

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