A UV-cured waterborne polyurethane coating film with butyl acrylate and silicone side chains and its preparation method

Abstract

The present invention relates to a UV-curable waterborne polyurethane coating film with butyl acrylate and organosilicon side chains and a preparation method thereof, belonging to the technical field of polyurethane coating film preparation. A diol containing butyl acrylate groups and organosilicon is first synthesized and added as a chain extender to the resin preparation process. After a chain extension reaction, the diol containing butyl acrylate groups and siloxane is incorporated into the polyurethane backbone, thereby preparing a waterborne polyurethane, which is then UV-cured to form a film. The coating film prepared by the present invention exhibits good mechanical properties, enhanced hydrophobicity, and excellent thermal stability, showing promising application prospects in the coatings field.

Description

Technical Field

[0001] The invention relates to a UV-cured waterborne polyurethane coating film with butyl acrylate and organosilicon side chains and a preparation method thereof, belonging to the technical field of polyurethane coating film preparation. Background Art

[0002] UV-curable coatings cure in a very short time by inducing polymerization of reactive compositions through UV light exposure. Compared to traditional solvent-curing coatings, UV-curable coatings offer the advantage that all formulations directly or indirectly participate in the curing reaction, transforming into a solid film. This translates to zero volatile organic compound (VOC) emissions during the curing process. Furthermore, the curing speed is high and energy consumption is low. Consequently, UV-curable coatings are considered green coatings with the "5E" characteristics: high efficiency, environmental friendliness, energy conservation, economy, and enabling performance. Today, people around the world are increasingly prioritizing environmental protection, ecological balance, and sustainable development. Many countries have enacted laws to limit the emission of volatile organic compounds into the atmosphere. Against this backdrop, UV-curable coatings offer significant advantages and broader application potential compared to other traditional coatings.

[0003] Typically, most types of polyurethane systems contain large amounts of volatile organic compounds (VOCs) and, in some cases, a certain amount of free isocyanate. Due to the toxicity of organic solvents, there are concerns about environmental pollution. In the late 1960s, waterborne polyurethane dispersions were introduced. A waterborne polyurethane dispersion is a binary colloidal system in which polyurethane particles are dispersed in a continuous aqueous medium. The concept behind the production of waterborne polyurethanes is to produce polymers with a large number of hydrophilic groups to achieve water solubility. These environmentally friendly polymers are non-toxic, non-flammable, and do not pollute the air or generate wastewater. Since only water evaporates during the process, these systems are environmentally friendly. Waterborne polyurethanes are important in many industrial applications, such as coatings, adhesives, ink binders, fiberglass, paper pulp, synthetic leather, biomaterials, membranes and packaging films, and waterproof textiles.

[0004] Butyl acrylate, as a component of the active resin formulation, is added to lower the glass transition temperature and improve the coating's flexibility, creating conditions for producing fast-drying, high-hardness, and excellent weather-resistant coatings. Butyl acrylate is a frequently used, effective component in the coatings and paints industry for the production of high-quality, multi-functional products. For example, it is essential in the development of specialized paints for construction, automotive, and household appliances.

[0005] Silicones are a class of polymers with repeating Si-O bonds as their backbone, and organic groups directly attached to the Si atoms. This unique structure combines the properties of both inorganic and organic materials, with fundamental properties such as low surface tension, a low viscosity-temperature coefficient, high compressibility, and high gas permeability. Silicones also possess excellent properties such as high and low temperature resistance, electrical insulation, oxidation stability, weather resistance, flame retardancy, hydrophobicity, corrosion resistance, non-toxicity, odorlessness, and physiological inertness. They are widely used in aerospace, electronics, construction, transportation, chemicals, textiles, food, light industry, and healthcare. Summary of the Invention

[0006] The purpose of the present invention is to overcome the above-mentioned shortcomings and provide a UV-curable waterborne polyurethane coating film with butyl acrylate and silicone side chains and a preparation method thereof. The invention synthesizes a waterborne polyurethane containing butyl acrylate and silicone side chains. After modification, the excellent inherent properties of polyester polyurethane, such as adhesion, hardness, and curing rate, are not affected, while the flexibility and water resistance of the polyurethane coating film can be enhanced.

[0007] The technical solution of the present invention is a method for preparing a UV-curable waterborne polyurethane coating film with butyl acrylate and silicone side chains. First, a diol with butyl acrylate groups and silicone is synthesized and added as a chain extender during the resin preparation process. After a chain extension reaction, the diol with butyl acrylate groups and siloxane is connected to the polyurethane main chain, thereby preparing a waterborne polyurethane, which is then UV-cured to form a film.

[0008] Furthermore, the specific steps are:

[0009] (1) Synthesis of diol containing butyl acrylate and silicone: Add an organic solution containing an ester group and an unsaturated double bond in the molecule to a reaction vessel, mix and stir evenly in solvent 1, then add diol containing an amino group, stir and reflux at 60-80°C for 6-12 hours; then cool to room temperature, add silicone, react for 1-10 hours, and evaporate solvent 1 at 40-60°C to obtain diol containing butyl acrylate and silicone.

[0010] (2) Preparation of aqueous polyurethane emulsion with butyl acrylate and silicone side chains:

[0011] a. uniformly dissolving the diol containing butyl acrylate and organosilicon prepared in step (1) in solvent 2 to obtain a diol solution containing butyl acrylate and organosilicon;

[0012] b. Add a metered catalyst and diisocyanate to a reaction vessel, introduce inert gas protection, gradually raise the temperature to 45°C, add a metered polyester diol and a synthesized diol solution containing butyl acrylate and silicone to the system at a rate of 2-3 seconds per drop, adjust the system viscosity to 4000-6000 cps with solvent 2, and react for 2 hours;

[0013] c. Use di-n-butylamine method to titrate the free -NCO content in the system. When the -NCO content reaches the theoretical value, increase the temperature to 65°C and add the measured hydrophilic chain extender at a rate of 2-3 seconds / drop. React for 3 hours;

[0014] d. Titrate the free -NCO content in the system. When the -NCO content reaches the theoretical value, add the measured amount of double bond-containing end-capping agent 1 at a rate of 2-3 seconds / drop to semi-end-cap the polymer and react for 3 hours;

[0015] e. Titrate the free -NCO content in the system. When the -NCO content reaches the theoretical value, add the measured amount of active end-capping agent 2 at a rate of 2-3 seconds / drop to end-cap the polymer. React for 3 hours. During this process, use solvent 2 to adjust the system viscosity to 4000-6000 cps;

[0016] f. Use infrared spectroscopy to detect 2270cm -1 When the -NCO peak disappears completely, the reaction temperature is lowered to 20-25°C, a neutralizer is added, and the mixture is stirred and sheared for 1-2 hours. Deionized water is then added, and high-speed shearing emulsification is performed at 1000-1200 r / min for 1-2 hours. The solvent 2 is removed by vacuum rotary evaporation at 40-60°C and -0.1-0 MPa to obtain a UV-curable waterborne polyurethane emulsion modified with side chain butyl acrylate and silicone;

[0017] (3) Photocuring of the coating: first, take the aqueous polyurethane emulsion prepared in step (2), then add a photoinitiator and disperse it evenly under light-proof conditions; apply it on a carrier, place it at room temperature for 2-4 hours, and dry it in an oven at 60-80°C for 1-3 hours; finally, place the coating in a UV curing machine and cure it for 10-30 seconds to obtain a UV-cured aqueous polyurethane coating with butyl acrylate and silicone side chains.

[0018] Furthermore, the waterborne polyurethane coating has a thickness of 0.05-0.1 mm.

[0019] Furthermore, the organic solution containing an ester group and an unsaturated double bond in the molecule in step (1) is specifically methyl acrylate and / or butyl acrylate; and the amino-containing diol is specifically at least one of left-handed aminodiol, right-handed aminodiol, and 3-amino-1,2-propylene glycol.

[0020] Furthermore, the solvent 1 in step (1) is specifically at least one of acetonitrile, ethanol, chloroform and nitrobenzene.

[0021] Furthermore, the solvent 2 in step (2) is specifically at least one of anhydrous ether, methanol and acetone.

[0022] Furthermore, the catalyst is specifically dibutyltin dilaurate and / or stannous octoate.

[0023] Furthermore, the diisocyanate is specifically at least one of toluene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI) and dicyclohexylmethane diisocyanate (HMDI).

[0024] Furthermore, the polyester diol is at least one of polycarbonate diol, polycaprolactone diol and adipic acid polyester diol.

[0025] Furthermore, the hydrophilic chain extender is at least one of 1,4-butanediol, 1,6-hexanediol and dimethylolpropionic acid.

[0026] Furthermore, the end-capping agent 1 is at least one of hydroxyethyl acrylate (HEA), hydroxyethyl methacrylate (HEMA), hydroxypropyl acrylate (HPA), hydroxypropyl methacrylate (HPMA) and pentaerythritol triacrylate (PETA).

[0027] Furthermore, the end-capping agent 2 is at least one of hydroxyethyl acrylate (HEA), hydroxyethyl methacrylate (HEMA), hydroxypropyl acrylate (HPA), trimethylolpropane (TMP), hydroxypropyl methacrylate (HPMA) and pentaerythritol triacrylate (PETA).

[0028] Furthermore, the neutralizing agent is at least one of ethylenediamine, diethylamine and triethylamine.

[0029] Furthermore, in step (1), 1-3 g of an organic solution containing an ester group and an unsaturated double bond in the molecule is dissolved in 5-10 mL of solvent 1; and 0.5-1.5 g of an amino-containing diol and 2-3 g of organosilicon are added.

[0030] Furthermore, in step (2):

[0031] a. Dissolve 0.4-0.6 g of diol containing butyl acrylate and silicone in 5-10 mL of solvent 2;

[0032] b. Add 0.01-0.05g catalyst, 4-6g diisocyanate, and 4-10g polyester diol;

[0033] c. Add 0.5-0.8g hydrophilic chain extender;

[0034] d. Add 1.5-2g of double bond-containing capping agent 1;

[0035] e. Add 0.2-0.4g active capping agent 2;

[0036] f. Add 0.5-1 mL of neutralizer and 30-50 mL of deionized water.

[0037] Furthermore, in step (3), 4-6 g of aqueous polyurethane emulsion is taken and 0.2-0.3 g of photoinitiator is added.

[0038] The method prepares a UV-cured waterborne polyurethane coating film with butyl acrylate and silicone side chains.

[0039] Furthermore, the waterborne polyurethane coating film has good mechanical properties and thermal stability.

[0040] The present invention has the following beneficial effects: A diol containing butyl acrylate and organosilicon is synthesized and added as a chain extender during the resin synthesis process to produce a UV-curable waterborne polyurethane coating modified with side-chain butyl acrylate and organosilicon. During film formation, the butyl acrylate and organosilicon segments on the side chains tend to aggregate and orient on the surface, while the polyurethane segments face the inner layer. The resulting coating exhibits excellent mechanical properties, enhanced hydrophobicity, and excellent thermal stability, demonstrating promising application prospects in the coatings industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 These are photos of the water contact angles of the waterborne polyurethane coatings prepared in Examples and Comparative Examples.

[0042] Figure 2 These are photos of stress-strain curves of waterborne polyurethane coatings prepared in Examples and Comparative Examples. DETAILED DESCRIPTION

[0043] Example 1

[0044] (1) Synthesis of diol containing butyl acrylate and organosilicon: 1.282 g of butyl acrylate was added to a three-necked flask, mixed evenly in 5 mL of ethanol, stirred evenly, and then 0.911 g of 3-amino-1,2-propylene glycol was added, stirred and refluxed, the temperature was maintained at 70 °C, and the reaction was carried out for 8 h, then cooled to room temperature, 2.474 g of 3-isocyanatepropyltriethoxysilane was added, and the reaction was carried out for 2 h. After removing the ethanol by rotary evaporation at 40 °C, a diol containing butyl acrylate and organosilicon was obtained.

[0045] (2) Preparation of side chain butyl acrylate and silicone modified aqueous polyurethane emulsion:

[0046] a. Dissolve the diol containing butyl acrylate and organosilicon prepared in step (1) in 8 mL of acetone;

[0047] b. In a four-necked flask equipped with a condenser, a nitrogen conduit, a stirring rod and a thermometer, 3 drops of dibutyltin dilaurate and 4.446 g of isophorone diisocyanate were added, and N2 protection was introduced. The temperature was gradually raised to 45°C. 4.6 g of polycarbonate diol (500 molecular weight) and the diol containing butyl acrylate and organosilicon synthesized in step (1) (uniformly dissolved in acetone) were added to the system at a rate of 2-3 seconds / drop using a separatory funnel. The viscosity of the system was adjusted to 4000-6000 cps with acetone and the reaction was continued for 2 h.

[0048] c. Titrate the free -NCO content in the system with di-n-butylamine. When the -NCO content reaches the theoretical value, raise the temperature to 65°C and add 0.650g of dimethylolpropionic acid at a rate of 2-3 seconds / drop using a separatory funnel. React for 3 hours.

[0049] d. Titrate the free -NCO content in the system. When the -NCO content reaches the theoretical value, add 1.525 g of pentaerythritol triacrylate at a rate of 2-3 seconds / drop using a separatory funnel to semi-end-cap the polymer and react for 3 hours;

[0050] e. Titrate the free -NCO content in the system. When the -NCO content reaches the theoretical value, add 0.225 g of trimethylolpropane at a rate of 2-3 seconds / drop using a separatory funnel to cap the polymer. React for 3 hours. During this process, use acetone to adjust the viscosity of the system.

[0051] f. Use infrared spectroscopy to detect 2270cm -1 When the -NCO peak completely disappeared, the reaction temperature was lowered to 25°C, 0.695 mL of triethylamine was added, stirred and sheared for 1 hour, and then 30 mL of deionized water was added. High-speed shear emulsification was carried out at 1000 r / min for 1 hour. Acetone was removed by vacuum rotary evaporation at 50°C and -0.1 MPa to obtain a side chain butyl acrylate and silicone-modified UV-curable water-based polyurethane emulsion.

[0052] (3) Photocuring of coating: First, take 5 g of the aqueous polyurethane emulsion prepared in step (2), then add 0.25 g of photoinitiator 1173, disperse evenly under light-proof conditions, and then coat it on a glass slide or a polytetrafluoroethylene tank, leave it at room temperature for 3 h, and dry it in a 60°C oven for 2 h. Finally, place the coating film in a UV curing machine and cure it for 20 seconds to obtain a UV-cured aqueous polyurethane coating modified with side chain butyl acrylate and silicone.

[0053] Example 2

[0054] (1) Synthesis of diol containing butyl acrylate and organosilicon: 1.282 g of butyl acrylate was added to a three-necked flask, mixed in ethanol, and stirred evenly. Then 0.911 g of 3-amino-1,2-propylene glycol was added, stirred and refluxed, the temperature was maintained at 70°C, and the reaction was carried out for 8 hours. Then the temperature was lowered to room temperature, 2.474 g of 3-isocyanatepropyltriethoxysilane was added, and the reaction was carried out for 2 hours. After removing the ethanol by rotary evaporation, the diol containing butyl acrylate and organosilicon was obtained.

[0055] (2) Preparation of side chain butyl acrylate and silicone modified aqueous polyurethane emulsion:

[0056] a. Dissolve the diol containing butyl acrylate and organosilicon prepared in step (1) in 8 mL of acetone;

[0057] b. In a four-necked flask equipped with a condenser, a nitrogen conduit, a stirring rod and a thermometer, 3 drops of dibutyltin dilaurate and 4.446 g of isophorone diisocyanate were added, and N2 protection was introduced. The temperature was gradually raised to 45°C. 9.2 g of polycarbonate diol (1000 molecular weight) and the diol containing butyl acrylate and organosilicon synthesized in step (1) (uniformly dissolved in acetone) were added to the system at a rate of 2-3 seconds / drop using a separatory funnel. The viscosity of the system was adjusted to 4000-6000 cps with acetone and the reaction was continued for 2 h.

[0058] c. Titrate the free -NCO content in the system with di-n-butylamine. When the -NCO content reaches the theoretical value, raise the temperature to 65°C and add 0.650g of dimethylolpropionic acid at a rate of 2-3 seconds / drop using a separatory funnel. React for 3 hours.

[0059] d. Titrate the free -NCO content in the system. When the -NCO content reaches the theoretical value, add 1.525 g of pentaerythritol triacrylate at a rate of 2-3 seconds / drop using a separatory funnel to semi-end-cap the polymer and react for 3 hours;

[0060] e. Titrate the free -NCO content in the system. When the -NCO content reaches the theoretical value, add 0.225 g of trimethylolpropane at a rate of 2-3 seconds / drop using a separatory funnel to cap the polymer. React for 3 hours. During this process, use acetone to adjust the viscosity of the system.

[0061] f. Use infrared spectroscopy to detect 2270cm -1 When the -NCO peak completely disappeared, the reaction temperature was lowered to 25°C, 0.695 mL of triethylamine was added, stirred and sheared for 1 hour, and then 50 mL of deionized water was added. High-speed shear emulsification was carried out for 1 hour, and acetone was removed by vacuum rotary evaporation at 50°C and -0.1 MPa to obtain a side chain butyl acrylate and silicone-modified UV-curable water-based polyurethane emulsion.

[0062] (3) Photocuring of coating: First, take 5 g of the aqueous polyurethane emulsion prepared in step (2), then add 0.25 g of photoinitiator 1173, disperse evenly under light-proof conditions, and then coat it on a glass slide or a polytetrafluoroethylene tank, leave it at room temperature for 3 h, and dry it in a 60°C oven for 2 h. Finally, place the coating film in a UV curing machine and cure it for 20 seconds to obtain a UV-cured aqueous polyurethane coating modified with side chain butyl acrylate and silicone.

[0063] Comparative Example 1

[0064] (1) Preparation of waterborne polyurethane emulsion:

[0065] a. In a four-necked flask equipped with a condenser, nitrogen conduit, stirring rod and thermometer, add 3 drops of dibutyltin dilaurate and 4.446g of isophorone diisocyanate, introduce N2 protection, gradually raise the temperature to 45°C, use a separatory funnel to add 10g of polycarbonate diol (1000 molecular weight, uniformly dissolved in acetone) to the system at a rate of 2-3 seconds / drop, adjust the viscosity of the system with acetone, and react for 2h;

[0066] b. Titrate the free -NCO content in the system with di-n-butylamine method. When the -NCO content reaches the theoretical value, increase the temperature to 65°C and add 0.650g of dimethylolpropionic acid at a rate of 2-3 seconds / drop using a separatory funnel. React for 3 hours.

[0067] c. Titrate the free -NCO content in the system. When the -NCO content reaches the theoretical value, add 1.525 g of pentaerythritol triacrylate at a rate of 2-3 seconds / drop using a separatory funnel to semi-end-cap the polymer and react for 3 hours;

[0068] d. Titrate the free -NCO content in the system. When the -NCO content reaches the theoretical value, add 0.225 g of trimethylolpropane at a rate of 2-3 seconds / drop using a separatory funnel to cap the polymer. React for 3 hours. During this process, use acetone to adjust the viscosity of the system.

[0069] e. Use infrared spectroscopy to detect 2270cm -1 When the -NCO peak completely disappears, the reaction temperature is lowered to 25°C, 0.695 ml of triethylamine is added, stirred and sheared for 1 hour, deionized water is added, high-speed shear emulsification is performed for 1 hour, and acetone is removed by vacuum rotary evaporation to obtain a side chain butyl acrylate and silicone-modified UV-curable water-based polyurethane emulsion.

[0070] (2) Photocuring of coating: First, take 5 g of the aqueous polyurethane emulsion prepared in step (2), then add 0.25 g of photoinitiator 1173, disperse evenly under light-proof conditions, and then coat it on a glass slide or a polytetrafluoroethylene tank, leave it at room temperature for 3 h, and dry it in a 60°C oven for 2 h. Finally, place the coating film in a UV curing machine and cure it for 20 s to obtain a UV-cured aqueous polyurethane coating.

[0071] Application Example 1

[0072] Contact angle experiments were conducted using the waterborne polyurethane coating films prepared in Comparative Example 1 and Examples 1-2.

[0073] 0.5 mL of each of the aqueous polyurethane emulsions prepared in Examples 1-2 and Comparative Example 1 was evenly applied to a clean, transparent glass sheet, each measuring 3 cm by 2.5 cm. The sheet was then left at room temperature for 3 hours, oven-dried at 60°C for 2 hours, and cured in a UV curing machine for 20 seconds to obtain a waterborne polyurethane coating. The water contact angle of the coating was measured using an optical contact angle meter (OCA40, Dataphysics, Germany) using the hanging drop method. Five random points on the coating surface were measured, and the average result was calculated.

[0074] Specific results such as Figure 1 Wherein 500 and 1000 represent the molecular weight of the polycarbonate diol used, the ones without + represent the unmodified waterborne polyurethane coating (Comparative Example 1), and the ones with + represent the side chain butyl acrylate and silicone modified waterborne polyurethane coating (Examples 1-2).

[0075] from Figure 1 It can be seen that the water contact angle of the waterborne polyurethane coating modified with side chain butyl acrylate and silicone is significantly improved compared with the unmodified waterborne polyurethane coating, and the water contact angle when the molecular weight of the polycarbonate diol is 1000 is slightly larger than that when the molecular weight is 500, indicating that the siloxane is successfully integrated into the side chain of the polyurethane and the hydrophobicity of the coating is improved, which expands the application range and application scenarios of the coating material.

[0076] Application Example 2

[0077] The stress-strain test experiment was carried out using the waterborne polyurethane coating films prepared in Comparative Example 1 and Examples 1-2.

[0078] The waterborne polyurethane emulsions prepared in Examples 1-2 and Comparative Example 1 were evenly spread and coated on a polytetrafluoroethylene dumbbell-shaped groove mold. The outer diameter of the dumbbell-shaped spline was 5 cm*8 mm, and the neck was 2 cm*4 mm. The mold was placed at room temperature for 3 hours and then dried in a 60°C oven for 2 hours. Finally, the polytetrafluoroethylene dumbbell-shaped groove mold was placed in a UV curing machine and cured for 20 seconds. After curing, the waterborne polyurethane dumbbell-shaped spline was removed to obtain a waterborne polyurethane dumbbell-shaped spline. The dumbbell-shaped spline was tensile tested using a dual-column benchtop test system (5976X, ITW, USA) at a tensile rate of 20 mm / min. Three samples were prepared for each of Examples 1-2 and Comparative Example 1, and the final results were averaged.

[0079] Specific results such as Figure 2 Wherein 500 and 1000 represent the molecular weight of the polycarbonate diol used, the ones without + represent the unmodified waterborne polyurethane coating (Comparative Example 1), and the ones with + represent the side chain butyl acrylate and silicone modified waterborne polyurethane coating (Examples 1-2).

[0080] from Figure 2 It can be seen that the stress-strain curve of the waterborne polyurethane coating modified with side chain butyl acrylate and silicone is significantly higher than that of the control group, and the stress-strain curve when the molecular weight of the polycarbonate diol is 1000 is higher than the stress-strain curve when the molecular weight is 500, indicating that butyl acrylate is successfully integrated into the side chain of the polyurethane, thereby improving the mechanical properties of the coating.

Claims

1. A method for preparing a UV-curable waterborne polyurethane coating film with butyl acrylate and silicone side chains, characterized in that Here are the steps: (1) Synthesis of diol containing butyl acrylate and organosilicon: Butyl acrylate and solvent 1 are added to a reaction vessel, mixed and stirred evenly, and then 0.5-1.5 g of diol containing amino group is added. The mixture is stirred and refluxed at 60-80°C for 6-12 h. The mixture is then cooled to room temperature, 2-3 g of organosilicon is added, and the mixture is reacted for 1-10 h. The solvent 1 is then removed by rotary evaporation at 40-60°C to obtain a diol containing butyl acrylate and organosilicon. The amino-containing diol is specifically at least one of left-handed aminodiol, right-handed aminodiol, and 3-amino-1,2-propylene glycol; the organosilicon is 3-isocyanatepropyltriethoxysilane; (2) Preparation of waterborne polyurethane emulsion with butyl acrylate and silicone side chains: a. Dissolve 0.4-0.6 g of the diol containing butyl acrylate and organosilicon prepared in step (1) in 5-10 mL of solvent 2 to obtain a diol solution containing butyl acrylate and organosilicon; b. Add 0.01-0.05g of a metered catalyst and 4-6g of a diisocyanate to a reaction vessel, introduce inert gas protection, gradually raise the temperature to 45°C, add the metered polyester diol and 4-10g of a synthesized diol solution containing butyl acrylate and silicone to the system at a rate of 2-3 seconds / drop, adjust the system viscosity to 4000-6000cps with solvent 2, and react for 2h; c. Use di-n-butylamine method to titrate the free -NCO content in the system. When the -NCO content reaches the theoretical value, increase the temperature to 65°C and add 0.5-0.8g of hydrophilic chain extender at a rate of 2-3 seconds / drop. React for 3 hours. d. Titrate the free -NCO content in the system. When the -NCO content reaches the theoretical value, add 1.5-2g of double bond-containing end-capping agent 1 at a rate of 2-3 seconds / drop to semi-end-cap the polymer and react for 3 hours; e. Titrate the free -NCO content in the system. When the -NCO content reaches the theoretical value, add 0.2-0.4 g of active end-capping agent 2 at a rate of 2-3 seconds / drop to end-cap the polymer. React for 3 hours. During this process, use solvent 2 to adjust the system viscosity to 4000-6000 cps. f. Detect by infrared spectroscopy that the -NCO peak at 2270 cm-1 completely disappears, lower the reaction temperature to 20-25°C, add 0.5-1 mL of a neutralizer, stir and shear for 1-2 hours, then add 30-50 mL of deionized water, emulsify at a high shear rate of 1000-1200 r / min for 1-2 hours, and remove solvent 2 by vacuum rotary evaporation at 40-60°C and -0.1~0 MPa to obtain a side chain butyl acrylate and silicone modified UV-curable waterborne polyurethane emulsion; (3) Photocuring of the coating: First, take 4-6 g of the aqueous polyurethane emulsion prepared in step (2), then add 0.2-0.3 g of photoinitiator and disperse evenly in the dark; apply it on a carrier, leave it at room temperature for 2-4 h, and dry it in an oven at 60-80 ° C for 1-3 h; finally, place the coating in a UV curing machine and cure it for 10-30 seconds to obtain a UV-cured aqueous polyurethane coating with butyl acrylate and silicone side chains.

2. The method for preparing a UV-curable waterborne polyurethane coating film with butyl acrylate and silicone side chains according to claim 1, wherein: The solvent 1 in step (1) is specifically at least one of acetonitrile, ethanol, chloroform and nitrobenzene.

3. The method for preparing a UV-curable waterborne polyurethane coating film with butyl acrylate and silicone side chains as claimed in claim 2, characterized in that: The solvent 2 in step (2) is specifically at least one of anhydrous ether, methanol and acetone.

4. The method for preparing a UV-curable waterborne polyurethane coating film with butyl acrylate and silicone side chains as claimed in claim 2, characterized in that: The catalyst is specifically dibutyltin dilaurate and / or stannous octoate; The hydrophilic chain extender is at least one of 1,4-butanediol, 1,6-hexanediol and dimethylolpropionic acid; The end-capping agent 1 is at least one of hydroxyethyl acrylate HEA, hydroxyethyl methacrylate HEMA, hydroxypropyl acrylate HPA, hydroxypropyl methacrylate HPMA and pentaerythritol triacrylate PETA; The end-capping agent 2 is at least one of hydroxyethyl acrylate HEA, hydroxyethyl methacrylate HEMA, hydroxypropyl acrylate HPA, trimethylolpropane TMP, hydroxypropyl methacrylate HPMA and pentaerythritol triacrylate PETA; The neutralizing agent is at least one of ethylenediamine, diethylamine and triethylamine.

5. The method for preparing a UV-curable waterborne polyurethane coating film with butyl acrylate and silicone side chains as claimed in claim 2, characterized in that: The diisocyanate is specifically at least one of toluene diisocyanate TDI, 4,4'-diphenylmethane diisocyanate MDI, isophorone diisocyanate IPDI, 1,6-hexamethylene diisocyanate HDI and dicyclohexylmethane diisocyanate HMDI; The polyester diol is at least one of polycarbonate diol, polycaprolactone diol and adipic acid polyester diol.

6. A UV-cured waterborne polyurethane coating film with butyl acrylate and silicone side chains prepared by the method of any one of claims 1 to 5.

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