Photocurable silicone-modified waterborne acrylic coatings and their preparation methods

Abstract

This invention belongs to the field of acrylic coating technology, specifically relating to a photocurable silicone-modified waterborne acrylic coating and its preparation method. First, a silane-modified acrylic alcohol ester is prepared. Then, polyglycerol-2-dipolyhydroxystearate is reacted with siloxane, isocyanate, dimethylolbutyric acid, and a catalyst. After chain extension, a capping agent containing the modified acrylic alcohol ester is added dropwise at a lower temperature to seal the emulsion, resulting in a waterborne polyurethane emulsion. Propylene oxide block copolymer and butyl methacrylate are added to the emulsion, and the reaction yields a silicone-modified waterborne acrylic ester. After photocuring, a waterborne photocurable silicone-modified acrylic coating is obtained. The waterborne emulsion of this invention can effectively reduce VOC content. The prepared coating has advantages such as good adhesion, good chemical resistance, and fast UV curing. Furthermore, its resistance to photoaging and water resistance is greatly improved, and its storage life and service life are also better.

Description

Technical Field

[0001] This invention belongs to the field of acrylic coating technology, specifically relating to a photocurable silicone-modified waterborne acrylic coating and its preparation method. Background Technology

[0002] Acrylic water-based coatings are one of the main types of wood coatings, possessing advantages such as light color, high transparency, high gloss, high solids content, strong adhesion, good application performance, and safe use. Photocuring technology, as an eco-compatible technology, produces coatings with high hardness, high gloss, scratch resistance, and chemical resistance, thus having the potential to replace traditional coating manufacturing technologies. However, coatings prepared using photocuring technology also have significant drawbacks, such as high volatility and strong odor.

[0003] Water-soluble coatings are a type of highly efficient and environmentally friendly modern coating because they use water as a solvent, which greatly reduces the content of volatile organic compounds (VOCs). Considering that combining water-soluble technology with UV curing technology can effectively overcome the shortcomings of each other, a superior product with complementary advantages can be obtained.

[0004] While UV-cured waterborne acrylic coatings offer numerous advantages and applications across various fields, their use is limited by shortcomings in hardness, abrasion resistance, and mechanical properties. Mechanical properties, particularly tensile strength and toughness, remain insufficient. Furthermore, due to their UV-curing mechanism, these acrylic coatings exhibit significant issues with UV aging resistance, severely restricting their practical applications and thus greatly limiting their overall use.

[0005] The current method employs a polyurethane synthesis system, introducing acrylate groups through chain extension and end-capping, and combining this with organosilicon modification. This improves the mechanical properties and aging resistance of acrylate coatings, as well as their hydrophilicity and hydrophobicity. This modified structure further enhances the mechanical properties compared to traditional acrylate coatings. Simultaneously, the introduced large number of siloxane bonds significantly improves the material's aging resistance. Using nonionic emulsifiers and emulsion polymerization, the coating is synthesized, exhibiting characteristics of water-based coatings, readily soluble in water or solvents such as ethanol, and significantly reducing VOC content. The high acrylic acid content accelerates the coating's curing speed, achieving curing within 30 seconds, meeting application requirements. For example, Zhang Dinglun et al. prepared a vinylsiloxane-modified photocurable waterborne polyurethane-acrylate composite emulsion (WPUASi) using a self-emulsification method. The introduction of organosilicon improves the surface properties of the film, while the increased number of crosslinking points enhances the photocuring rate of the emulsion. Li Xinghui et al. synthesized an organosilicon polyurethane acrylate prepolymer using isoflurane diisocyanate, polycaprolactone diol, hydroxypropyl diacrylate, 2-hydroxyethyl acrylate, and tetrahydrofuran acrylate. A photocurable organosilicon polyurethane acrylate release film was prepared by irradiation with ultraviolet light for 60 seconds. With increasing polycaprolactone diol content, the peel force of the release film increased, while the tensile strength and elongation at break decreased. Liu Wei et al. synthesized a UV-curable acrylate resin (UV-WZF) using methyl methacrylate (MMA), butyl acrylate (n-BA), tripropylene glycol diacrylate (TPGDA), and γ-(methacryloyloxy)propyltrimethoxysilane (KH-570) as monomers, n-dodecyl mercaptan (NDM) as a chain transfer agent, and azobisisobutyronitrile (AIBN) as an initiator. When the amount of silane coupling agent KH-570 is 6%, the coating adhesion is good; when the amount of TPGDA is 26%, the curing time of the cured coating is the shortest.

[0006] As can be seen from the above invention, the functionality of the prepared modified acrylic coatings has been improved, but the manufacturing process is complex and insufficient to address the current shortcomings, and the mechanical properties are not outstanding. Its resistance to light aging, water resistance, and service life still cannot meet the requirements of some environments. Summary of the Invention

[0007] This invention addresses the shortcomings of existing technologies by proposing a waterborne organosilicon-modified acrylic coating and its preparation method that simultaneously possesses excellent mechanical properties, aging resistance, and a hydrophobic surface, thus solving the performance requirements that most waterborne acrylic coatings cannot meet. Organosilicon modification improves the mechanical properties and aging resistance of the acrylic coating, and enhances its hydrophilicity and hydrophobicity. This modified structure further improves the mechanical properties compared to traditional acrylic coatings. Simultaneously, the designed structure, due to the introduction of numerous siloxane bonds, significantly enhances the material's aging resistance.

[0008] The preparation method of the photocurable silicone-modified waterborne acrylic coating of the present invention includes the following steps:

[0009] (1) Trimethylsilyl alcohol was placed in a flask, and under nitrogen protection, thionyl chloride dissolved in carbon tetrachloride was added and stirred until homogeneous. Concentrated hydrochloric acid was added to bring the pH of the reaction system to 2-3, and the mixture was heated to 100-120°C for 1 hour under acidic conditions. Then, polytetrahydrofuran (Mn=500) was added to silanize it, and the reaction was continued for 1 hour. The vacuum pump control system was turned on to remove low molecular weight substances under vacuum. The mixture was then transferred to a three-necked flask, stirred and refluxed at 65°C for 12 hours, the solvent was removed, glycidyl methacrylate was added, and the mixture was reacted at room temperature for 1 hour. The mixture was then washed with anhydrous ethanol until neutral to obtain silane-modified acrylate for later use.

[0010] The mass ratio of trimethylsilanol to thionyl chloride is 1:1; the molar ratio of polytetrahydrofuran to trimethylsilanol is 2:1; and the molar ratio of glycidyl methacrylate to polytetrahydrofuran is 1:2.

[0011] (2) Dehydrated polyglycerol-2-dihydroxystearate and dihydroxy-terminated polydimethylsiloxane were added to a four-necked flask equipped with a mechanical stirrer, thermometer, and reflux device. The temperature was raised to 80°C, and after N2 protection, isocyanate was added and the mixture was stirred for 1 hour. Dimethylolbutyric acid was then added and dibutyltin dilaurate catalyst was added dropwise, and the reaction was carried out for 2 hours. 1,4-Butanediol was added for chain extension reaction for 1 hour. The temperature was lowered to 70°C and a capping agent containing modified acrylate was added dropwise. The reaction was continued until all isocyanate groups in the system had reacted. The temperature was then lowered to 40°C and a trace amount of N,N-dimethylethanolamine and deionized water were added for neutralization for 1 hour to obtain an aqueous polyurethane emulsion.

[0012] The molar ratio of dihydroxy-terminated polydimethylsiloxane to polyglycerol-2-dihydroxystearate is 1:10, and the total number of hydroxyl groups in the two compounds is comparable to that in toluene diisocyanate. The amount of dimethylolbutyric acid used is 2-5% of the total mass of the raw materials in step (2), and the amount of dibutyltin dilaurate catalyst used is 0.1-0.5% of the total mass of the raw materials in step (2). The overall reaction environment pH is controlled at 3-5.

[0013] The isocyanate is one of toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), dicyclohexylmethane diisocyanate (HMDI), hexamethylene diisocyanate (HDI), and lysine diisocyanate (LDI).

[0014] The capping agent containing modified acrylate is a compound capping agent of modified acrylate or hydroxyethyl methacrylate and modified acrylate, and its total addition amount is 3 to 5% of the total mass of the raw materials in step (2).

[0015] (3) Take an appropriate amount of the emulsion obtained in the previous step and place it in a four-necked bottle. Add 2% emulsifier and an appropriate amount of butyl methacrylate. After swelling for 0.5 h, raise the temperature to 80 °C and adjust the pH of the solution. Continue the reaction for another 1 h to obtain the waterborne acrylic emulsion modified with organosilicon.

[0016] The emulsifier is one of polyoxyethylene ether, polyoxypropylene ether, ethylene oxide or propylene oxide block copolymer, polyol fatty acid ester, or polyvinyl alcohol; the amount of emulsifier is 2-5% of the total mass of the raw materials in step (3), the amount of butyl methacrylate is 5-10% of the total mass of the raw materials in step (3), and the amount of emulsion is 80-90% of the total mass of the raw materials in step (3).

[0017] (4) After adding 3.5% photoinitiator to the prepared emulsion, pour it into a polytetrafluoroethylene plate, place it at room temperature, dry it in a 60℃ oven for 4 hours, take it out and irradiate it under a 365nm ultraviolet lamp for 30 seconds to complete the curing, and obtain a water-based photocurable silicone-modified acrylic coating.

[0018] The photoinitiator is one of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, 1-hydroxycyclohexylphenyl ketone, and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone, and its amount is 3.5% of the total mass of the emulsion.

[0019] Beneficial effects:

[0020] This invention synthesizes a photocurable silicone-modified waterborne acrylic coating. This coating incorporates acrylate groups through chain extension and end-capping, and is combined with silicone modification, improving the mechanical properties, aging resistance, and hydrophilic / hydrophobic properties of the acrylic coating. Simultaneously, the designed structure, due to the introduction of numerous siloxane bonds, significantly enhances the material's aging resistance. Using a nonionic emulsifier, the coating is synthesized through swelling, giving it the characteristics of a waterborne coating, readily soluble in water or solvents such as ethanol, greatly reducing VOC content. The high acrylic acid content accelerates the coating's curing speed, achieving curing within 30 seconds, meeting application requirements. This environmentally friendly coating is poised to replace traditional solvent-based coatings, making the application prospects of photocurable silicone-modified waterborne acrylic coatings promising. Attached Figure Description

[0021] Figure 1 The infrared spectrum is shown for the silicone-modified waterborne photocurable silicone-modified acrylate coating synthesized in Example 1. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1

[0024] (1) Place 4.6 g of trimethylsilanol in a flask, add 4.6 g of thionyl chloride dissolved in carbon tetrachloride under nitrogen protection, stir until homogeneous, add 2 mol of concentrated hydrochloric acid (commercially available), and heat to 100 °C for 1 h in an acidic environment. Then add 50.5 g of polytetrahydrofuran with a molecular weight of 500 to silanize it, and continue the reaction for 1 h. Turn on the vacuum pump control system to remove low molecular weight substances under vacuum. Then transfer the mixture to a three-necked flask, stir and reflux at 65 °C for 12 h, remove the solvent, add 7.1 g of glycidyl methacrylate, react at room temperature for 1 h, and wash with anhydrous ethanol until neutral to obtain silane-modified acrylate for later use.

[0025] (2) Add 40.0 g of dehydrated polyglycerol-2-dihydroxystearate and 23.0 g of dihydroxy-terminated polydimethylsiloxane to a four-necked flask equipped with a mechanical stirrer, thermometer, and reflux device. Heat to 80°C, introduce N2 for protection, and then add 20 g of toluene diisocyanate. Stir and react for 1 h. Add 2 g of dimethylolbutyric acid and dropwise add 0.1 g of dibutyltin dilaurate catalyst and react for 2 h. Add 1.5 g of 1,4-butanediol for chain extension reaction, cool to 70°C, and dropwise add 1 g of end-capping agent hydroxyethyl methacrylate and 2 g of the modified acrylate obtained in the first step. React until all isocyanate groups in the system have reacted. Then cool to 40°C and add 5 ml of N,N-dimethylethanolamine and deionized water to neutralize for 1 h to obtain an aqueous polyurethane emulsion.

[0026] (3) Take 30g of the emulsion obtained in the previous step and place it in a four-necked bottle. Add 0.6633g of propylene oxide block copolymer and 2.5g of butyl methacrylate. After swelling for 0.5h, raise the temperature to 80℃ and adjust the pH of the solution to 4. Continue the reaction for 1h to obtain the waterborne photocurable silicone-modified acrylate emulsion modified with silicone.

[0027] (4) Take 30g of the prepared emulsion, add 1.0881g of photoinitiator 1-hydroxycyclohexylphenyl ketone, pour it into a polytetrafluoroethylene plate, place it at room temperature, dry it in a 60℃ oven for 4h, take it out and irradiate it under a 365nm ultraviolet lamp for 30s to complete the curing, and obtain a water-based photocurable organosilicon modified acrylic coating.

[0028] Test method: The tensile strength of acrylic coating film is determined by applying a gradually increasing tensile load along the length of a standard plastic specimen, causing it to deform until it breaks. The tensile stress required for the specimen to break is the tensile strength.

[0029] Elongation at break of acrylic coatings refers to the ratio of the maximum displacement to the initial length when the molded acrylic coating product is broken; in other words, how many times longer the product is when it breaks compared to its initial state. Elongation at break is expressed as a percentage (%).

[0030] UV aging resistance refers to the performance of a material exposed to a 300nm-400nm ultraviolet light field with a fluorescent lamp as the light source for 7 days at an irradiation intensity of 40W / m². 2 The tensile strength and elongation at break of the sample were tested again.

[0031] Water resistance test conditions: Under normal temperature and humidity, the coating is immersed in water for 15 days, and the tensile strength and elongation at break of the sample are tested again.

[0032] The hydrophobic properties of the material were verified by contact angle testing.

[0033] The hardness of the coating was tested using a Shore hardness tester.

[0034] The composition and structure of the synthesized compound were analyzed using Fourier transform infrared spectroscopy.

[0035] Infrared analysis showed at 3300cm -1 The nearby peak is a characteristic peak of -OH, at 1440 cm⁻¹. -1 and 2930cm -1 The left and right sides are characteristic peaks of -CH2, 1000-1130 cm⁻¹ -1 The strong absorption band that appears is a characteristic peak of Si-O-Si, at 890 cm⁻¹. -1 1060cm -1 and 1210cm -1 The left and right sides are characteristic peaks of Si-R, 1680 cm⁻¹ -1 The characteristic peak is -C=O. The appearance of the above characteristic peak indicates the successful synthesis of waterborne photocurable silicone-modified acrylate coating film.

[0036] The test results of waterborne photocurable silicone-modified acrylate coating films are shown in Table 1.

[0037] Example 2

[0038] The preparation of silane-modified acrylates is the same as in Example 1.

[0039] 40.0 g of dehydrated polyglycerol-2-dihydroxystearate and 23.0 g of dihydroxy-terminated polydimethylsiloxane were added to a four-necked flask equipped with a mechanical stirrer, thermometer, and reflux device. The mixture was heated to 80 °C, protected with N2, and then 20 g of toluene diisocyanate was added. The mixture was stirred and reacted for 1 h. Then, 2 g of dimethylolbutyric acid was added, and 0.1 g of dibutyltin dilaurate catalyst was added dropwise, reacting for 2 h. 1.5 g of 1,4-butanediol was added for chain extension, and the mixture was cooled to 70 °C. 3 g of the modified acrylate obtained in the first step was added dropwise, reacting until all isocyanate groups in the system had reacted. The mixture was then cooled to 40 °C, and 5 ml of N,N-dimethylethanolamine and deionized water were added for neutralization. The pH was adjusted to 7 for 1 h, yielding an aqueous polyurethane emulsion.

[0040] Take 30g of the emulsion obtained in the previous step and place it in a four-necked flask. Add 0.6633g of propylene oxide block copolymer and 2.5g of butyl methacrylate. After swelling for 0.5h, heat to 80℃ and adjust the pH of the solution to 4. Continue the reaction for another 1h to obtain a silicone-modified waterborne photocurable silicone-modified acrylic coating emulsion.

[0041] 30g of the prepared emulsion was added to 1.0881g of photoinitiator 1-hydroxycyclohexylphenyl ketone and poured into a polytetrafluoroethylene plate. The plate was placed at room temperature and dried in a 60℃ oven for 4 hours. The plate was then removed and irradiated under a 365nm UV lamp for 30 seconds to complete the curing process, thus obtaining a water-based photocurable silicone-modified acrylate coating.

[0042] The waterborne photocurable silicone-modified acrylate coating film was tested according to the test method in Example 1, and the results are shown in Table 1.

[0043] Example 3

[0044] The preparation of silane-modified acrylates is the same as in Example 1.

[0045] 30.0 g of dehydrated polyglycerol-2-dihydroxystearate and 17.23 g of dihydroxy-terminated polydimethylsiloxane were added to a four-necked flask equipped with a mechanical stirrer, thermometer, and reflux device. The mixture was heated to 80 °C, protected with N2, and then 20 g of toluene diisocyanate was added. The mixture was stirred and reacted for 1 h. Then, 1.0 g of dimethylolbutyric acid was added, and 0.05 g of dibutyltin dilaurate catalyst was added dropwise, and the reaction was carried out for 2 h. 1.5 g of 1,4-butanediol was added for chain extension. The mixture was cooled to 70 °C, and 1 g of the end-capping agent hydroxyethyl methacrylate and 1 g of the modified acrylate obtained in the first step were added dropwise. The reaction continued until all the isocyanate groups in the system had reacted. The mixture was then cooled to 40 °C, and 5 ml of N,N-dimethylethanolamine and deionized water were added for neutralization for 1 h, yielding an aqueous polyurethane emulsion.

[0046] Take 30g of the emulsion obtained in the previous step and place it in a four-necked flask. Add 0.6633g of emulsifier propylene oxide block copolymer and 2.5g of butyl methacrylate. After swelling for 0.5h, heat to 80℃ and adjust the pH of the solution to 4. Continue the reaction for another 1h to obtain a silicone-modified waterborne photocurable silicone-modified acrylic coating emulsion.

[0047] 30g of the prepared emulsion was added to 1.0881g of photoinitiator polyol fatty acid ester and poured into a polytetrafluoroethylene plate. The plate was placed at room temperature and dried in a 60℃ oven for 4 hours. The plate was then removed and irradiated under a 365nm ultraviolet lamp for 60 seconds to complete the curing process, thus obtaining a water-based photocurable silicone-modified acrylic coating.

[0048] The waterborne photocurable silicone-modified acrylate coating film was tested according to the test method, and the results are shown in Table 1.

[0049] Example 4

[0050] The preparation of silane-modified acrylates is the same as in Example 1.

[0051] 40.0 g of dehydrated polyglycerol-2-dihydroxystearate and 20.0 g of dihydroxy-terminated polydimethylsiloxane were added to a four-necked flask equipped with a mechanical stirrer, thermometer, and reflux device. The mixture was heated to 80 °C, protected with N2, and then 25 g of isophorone diisocyanate was added. The mixture was stirred and reacted for 1 h. Then, 2 g of dimethylolbutyric acid was added, and 0.1 g of dibutyltin dilaurate catalyst was added dropwise, reacting for 2 h. 2.0 g of 1,4-butanediol was added for chain extension. The mixture was cooled to 70 °C, and 1 g of hydroxyethyl methacrylate and 2 g of the modified acrylate obtained in the first step were added dropwise. The reaction continued until all isocyanate groups in the system had reacted. The mixture was then cooled to 40 °C, and a trace amount of N,N-dimethylethanolamine and deionized water were added for neutralization, resulting in an aqueous polyurethane emulsion.

[0052] Take 30g of the emulsion obtained in the previous step and place it in a four-necked flask. Add 0.6633g of emulsifier propylene oxide block copolymer and 2.5g of butyl methacrylate. After swelling for 0.5h, raise the temperature to 80℃ and adjust the pH of the solution to 4. Continue the reaction for another 1h to obtain a silicone-modified waterborne photocurable silicone-modified acrylic coating emulsion.

[0053] 30g of the prepared emulsion was added to 1.0881g of photoinitiator 1-hydroxycyclohexylphenyl ketone and poured into a polytetrafluoroethylene plate. The plate was placed at room temperature and dried in a 60℃ oven for 4 hours. The plate was then removed and irradiated under a 365nm UV lamp for 40 seconds to complete the curing process, thus obtaining a water-based photocurable silicone-modified acrylate coating.

[0054] The waterborne photocurable silicone-modified acrylate coating film was tested according to the test method, and the results are shown in Table 1.

[0055] Example 5

[0056] The preparation of silane-modified acrylates is the same as in Example 1.

[0057] 40.0 g of dehydrated polyglycerol-2-dihydroxystearate and 23.0 g of dihydroxy-terminated polydimethylsiloxane were added to a four-necked flask equipped with a mechanical stirrer, thermometer, and reflux device. The mixture was heated to 80 °C, protected with N2, and then 20 g of toluene diisocyanate was added. The mixture was stirred and reacted for 1 h. Then, 3 g of dimethylolbutyric acid was added, and 0.1 g of dibutyltin dilaurate catalyst was added dropwise, and the reaction was carried out for 2 h. The temperature was lowered to 70 °C, and 1 g of hydroxyethyl methacrylate and 2 g of the modified acrylate obtained in the first step were added dropwise. The reaction was continued until all the isocyanate groups in the system had reacted. The temperature was then lowered to 40 °C, and 5 ml of N,N-dimethylethanolamine and deionized water were added for neutralization for 1 h, yielding an aqueous polyurethane emulsion.

[0058] Take 30g of the emulsion obtained in the previous step and place it in a four-necked flask. Add 1.5789g of emulsifier propylene oxide block copolymer and 2.5g of butyl methacrylate. After swelling for 0.5h, raise the temperature to 80℃ and adjust the pH of the solution to 4. Continue the reaction for another 1h to obtain a silicone-modified waterborne photocurable silicone-modified acrylic coating emulsion.

[0059] 30g of the prepared emulsion was added to 1.0881g of photoinitiator (2,4,6-trimethylbenzoyl) diphenylphosphine oxide and poured into a polytetrafluoroethylene plate. The plate was placed at room temperature and dried in a 60℃ oven for 4 hours. After drying, the plate was irradiated under a 365nm UV lamp for 50 seconds to complete the curing process, thus obtaining a water-based photocurable silicone-modified acrylate coating.

[0060] The waterborne photocurable silicone-modified acrylate coating film was tested according to the test method, and the results are shown in Table 1.

[0061] Example 6

[0062] The preparation of silane-modified acrylates is the same as in Example 1.

[0063] 40.0 g of dehydrated polyglycerol-2-dihydroxystearate and 30.0 g of dihydroxy-terminated polydimethylsiloxane were added to a four-necked flask equipped with a mechanical stirrer, thermometer, and reflux device. The mixture was heated to 80 °C, protected with N2, and then 25 g of toluene diisocyanate was added. The mixture was stirred and reacted for 1 h. 2,5-dimethylolbutyric acid was then added, followed by the dropwise addition of 0.15 g of dibutyltin dilaurate catalyst, and the reaction was continued for 2 h. 1.5 g of 1,4-butanediol was added for chain extension. The mixture was cooled to 70 °C, and 1 g of hydroxyethyl methacrylate and 2 g of the modified acrylate obtained in the first step were added dropwise. The reaction continued until all isocyanate groups in the system had reacted. The mixture was then cooled to 40 °C, and 5 ml of N,N-dimethylethanolamine and deionized water were added for neutralization, resulting in an aqueous polyurethane emulsion.

[0064] Take 30g of the emulsion obtained in the previous step and place it in a four-necked flask. Add 0.6633g of emulsifier propylene oxide block copolymer and 2.5g of butyl methacrylate. After swelling for 0.5h, raise the temperature to 80℃ and adjust the pH of the solution to 4. Continue the reaction for another 1h to obtain a silicone-modified waterborne photocurable silicone-modified acrylic coating emulsion.

[0065] 30g of the prepared emulsion was added to 1.0881g of photoinitiator 1-hydroxycyclohexylphenyl ketone and poured into a polytetrafluoroethylene plate. The plate was placed at room temperature and dried in a 60℃ oven for 4 hours. The plate was then removed and irradiated under a 365nm UV lamp for 30 seconds to complete the curing process, thus obtaining a water-based photocurable silicone-modified acrylate coating.

[0066] The waterborne photocurable silicone-modified acrylate coating film was tested according to the test method, and the results are shown in Table 1.

[0067] Example 7

[0068] The preparation of silane-modified acrylates is the same as in Example 1.

[0069] 40.0 g of dehydrated polyglycerol-2-dihydroxystearate and 23.0 g of dihydroxy-terminated polydimethylsiloxane were added to a four-necked flask equipped with a mechanical stirrer, thermometer, and reflux device. The mixture was heated to 80 °C, protected with N2, and then 25 g of toluene diisocyanate was added. The mixture was stirred for 1 h. Then, 3 g of dimethylolbutyric acid was added, followed by the dropwise addition of 0.15 g of dibutyltin dilaurate catalyst, and the reaction was carried out for 2 h. 1.5 g of 1,4-butanediol was added for chain extension, and the mixture was cooled to 70 °C. 6 g of the modified acrylate obtained in the first step was added dropwise, and the reaction continued until all isocyanate groups in the system had reacted. The mixture was then cooled to 40 °C, and a trace amount of 5 ml of N,N-dimethylethanolamine and deionized water was added for neutralization for 1 h to obtain an aqueous polyurethane emulsion.

[0070] Take 30g of the emulsion obtained in the previous step and place it in a four-necked flask. Add 0.6633g of emulsifier propylene oxide block copolymer and 2.5g of butyl methacrylate. After swelling for 0.5h, raise the temperature to 80℃ and adjust the pH of the solution to 4. Continue the reaction for another 1h to obtain a silicone-modified waterborne photocurable silicone-modified acrylic coating emulsion.

[0071] 30g of the prepared emulsion was added to 1.0881g of photoinitiator 1-hydroxycyclohexylphenyl ketone and poured into a polytetrafluoroethylene plate. The plate was placed at room temperature and dried in a 60℃ oven for 4 hours. The plate was then removed and irradiated under a 365nm UV lamp for 30 seconds to complete the curing process, thus obtaining a water-based photocurable silicone-modified acrylate coating.

[0072] The waterborne photocurable silicone-modified acrylate coating film was tested according to the test method, and the results are shown in Table 1.

[0073] Compare with Example 1

[0074] 40.0 g of dehydrated polyglycerol-2-dihydroxystearate was added to a four-necked flask equipped with a mechanical stirrer, thermometer, and reflux device. The mixture was heated to 80 °C, protected with N2, and then 18 g of toluene diisocyanate was added. The mixture was stirred for 1 h. Then, 1.5 g of dimethylolbutyric acid was added, followed by the dropwise addition of 0.06 g of dibutyltin dilaurate catalyst, and the reaction was carried out for 2 h. 1.5 g of 1,4-butanediol was added for chain extension, and the mixture was cooled to 70 °C. 1 g of hydroxyethyl methacrylate end-capping agent was added dropwise, and the reaction continued until all isocyanate groups in the system had reacted. The mixture was then cooled to 40 °C, and a trace amount of N,N-dimethylethanolamine and deionized water were added for neutralization for 1 h to obtain an aqueous polyurethane emulsion.

[0075] Take 30g of the emulsion obtained in the previous step and place it in a four-necked flask. Add 0.6633g of emulsifier propylene oxide block copolymer and 2.5g of butyl methacrylate. After swelling for 0.5h, heat to 80℃ and adjust the pH of the solution to 4. Continue the reaction for another 1h to obtain a water-based photocurable acrylic coating emulsion without organosilicon modification.

[0076] The prepared emulsion was added to 1.0881g of photoinitiator 1-hydroxycyclohexylphenyl ketone and poured into a polytetrafluoroethylene plate. It was placed at room temperature and dried in a 60℃ oven for 4 hours. After being removed, it was irradiated under a 365nm ultraviolet lamp for 60 seconds to complete the curing, thus obtaining a water-based photocurable acrylic coating without organosilicon modification.

[0077] Waterborne UV-curable acrylic coatings without silicone modification were tested according to the test method.

[0078] Compare with Example 2

[0079] The preparation of silane-modified acrylates is the same as in Example 1.

[0080] 35g of dehydrated polyglycerol-2 dihydroxystearate was added to a four-necked flask equipped with a mechanical stirrer, thermometer, and reflux device. The mixture was heated to 80°C, protected with N2, and then 18g of toluene diisocyanate was added. The mixture was stirred for 1 hour. Then, 1.5g of dimethylolbutyric acid was added, followed by the dropwise addition of 0.05g of dibutyltin dilaurate catalyst, and the reaction was carried out for 2 hours. The temperature was lowered to 70°C, and 1g of hydroxyethyl methacrylate end-capping agent and 2g of the modified acrylate obtained in the first step were added dropwise. The reaction continued until all isocyanate groups in the system had reacted. The temperature was then lowered to 40°C, and 5ml of N,N-dimethylethanolamine and deionized water were added for neutralization for 1 hour, yielding an aqueous polyurethane emulsion.

[0081] Take 30g of the emulsion obtained in the previous step and place it in a four-necked flask. Add 0.6633g of emulsifier propylene oxide block copolymer. After swelling for 0.5h, raise the temperature to 80℃ and adjust the pH of the solution to 4. Continue the reaction for another 1h to obtain a waterborne photocurable silicone-modified acrylate coating.

[0082] 30g of the prepared emulsion was added to 1.0881g of photoinitiator 1-hydroxycyclohexylphenyl ketone and poured into a polytetrafluoroethylene plate. The plate was placed at room temperature and dried in a 60℃ oven for 4 hours. After drying, the plate was irradiated under a 365nm UV lamp for 60 seconds to complete the curing process, resulting in a low-silane modified waterborne photocurable silicone modified acrylate coating.

[0083] Low-silane modified waterborne photocurable silicone-modified acrylate coating films were tested according to the test method.

[0084] Compare with Example 3

[0085] 40.0 g of dehydrated polyglycerol-2-dihydroxystearate and 23.0 g of dihydroxy-terminated polydimethylsiloxane were added to a four-necked flask equipped with a mechanical stirrer, thermometer, and reflux device. The mixture was heated to 80 °C, protected with N2, and then 21 g of toluene diisocyanate was added. The mixture was stirred and reacted for 1 h. Then, 2 g of dimethylolbutyric acid was added, and 0.1 g of dibutyltin dilaurate catalyst was added dropwise, reacting for 2 h. 1.5 g of 1,4-butanediol was added for chain extension, and the mixture was cooled to 70 °C, with 1 g of hydroxyethyl methacrylate as a terminator added dropwise. The reaction continued until all isocyanate groups in the system had reacted. The mixture was then cooled to 40 °C, and a trace amount of 5 ml of N,N-dimethylethanolamine and deionized water was added for neutralization, followed by 1 h of reaction to obtain an aqueous polyurethane emulsion.

[0086] Take 30g of the emulsion obtained in the previous step and place it in a four-necked flask. Add 0.6633g of emulsifier propylene oxide block copolymer and 2.5g of butyl methacrylate. After swelling for 0.5h, raise the temperature to 80℃ and adjust the pH of the solution to 4. Continue the reaction for another 1h to obtain a waterborne silicone-modified acrylate coating.

[0087] 30g of the prepared emulsion was added to 1.0881g of photoinitiator 1-hydroxycyclohexylphenyl ketone and poured into a polytetrafluoroethylene plate. The plate was placed at room temperature and dried in a 60℃ oven for 4 hours. After drying, the plate was irradiated under a 365nm UV lamp for 60 seconds to complete the curing process, resulting in a low-silane modified waterborne photocurable silicone modified acrylate coating.

[0088] Waterborne UV-curable silicone-modified acrylate coating films were tested according to the test methods.

[0089] Table 1 summarizes and compares the performance of each embodiment and the control example.

[0090]

[0091]

Claims

1. A method for preparing a photocurable silicone-modified waterborne acrylic coating, characterized in that: The preparation method steps are as follows: (1) Trimethylsilyl alcohol was placed in a flask, and under nitrogen protection, thionyl chloride dissolved in carbon tetrachloride was added and stirred evenly. Concentrated hydrochloric acid was added and heated in an acidic environment to carry out chlorination. Polytetrahydrofuran was then added to silanize it and the reaction continued for 1 hour. The vacuum pump control system was turned on to remove low molecular weight substances under vacuum. The mixture was transferred to a three-necked flask and stirred and refluxed at 65°C for 12 hours. The solvent was removed, and glycidyl methacrylate was added and reacted at room temperature for 1 hour. The mixture was washed with anhydrous ethanol until neutral to obtain silane-modified acrylate. (2) Add dehydrated polyglycerol-2 dihydroxy stearate and dihydroxy-terminated polydimethylsiloxane to a four-necked flask equipped with a mechanical stirrer, thermometer and reflux device. Heat to 80°C, introduce N2 for protection and then add isocyanate. Stir and react for 1 h. Add dimethylolbutyric acid and add dibutyltin dilaurate catalyst dropwise and react for 2 h. Add 1,4-butanediol for chain extension reaction for 1 h. Cool to 70°C and add end-capping agent containing modified acrylate dropwise. React until all isocyanate groups in the system have reacted. Cool to 40°C and add N,N-dimethylethanolamine and deionized water to neutralize for 1 h to obtain waterborne polyurethane emulsion. The molar ratio of the dihydroxy-terminated polydimethylsiloxane to polyglycerol-2 dihydroxystearate is 1:10, and the total amount of hydroxyl groups in the dihydroxy-terminated polydimethylsiloxane and polyglycerol-2 dihydroxystearate is comparable to that in isocyanate. The end-capping agent containing the modified acrylate is a silane-modified acrylate or a compound end-capping agent of hydroxyethyl methacrylate and silane-modified acrylate. (3) Place the emulsion obtained in step (2) into a four-necked flask, add emulsifier and butyl methacrylate, swell and heat to 80°C and adjust the pH of the solution to 7, and continue the reaction for 1 hour to obtain an organosilicon modified waterborne acrylate emulsion. (4) After adding the photoinitiator to the prepared emulsion, pour it into a polytetrafluoroethylene plate, place it at room temperature, dry it in a 60°C oven for 4 hours, take it out and irradiate it under a 365nm ultraviolet lamp for 30 seconds to complete the curing, and obtain a water-based photocurable silicone-modified acrylic coating.

2. The method for preparing the photocurable silicone-modified waterborne acrylic coating as described in claim 1, characterized in that: In step (1), concentrated hydrochloric acid is added to adjust the pH to 2-4, and the temperature for the chlorination reaction is 100-120℃ for 1 hour; the mass ratio of trimethylsilanol to thionyl chloride is 1:

1.

3. The method for preparing the photocurable silicone-modified waterborne acrylic coating as described in claim 1, characterized in that: In step (1), the molar ratio of polytetrahydrofuran to trimethylsilyl alcohol is 2:1, and the molar ratio of glycidyl methacrylate to polytetrahydrofuran is 1:

2.

4. The method for preparing the photocurable silicone-modified waterborne acrylic coating as described in claim 1, characterized in that: The polyglycerol-2 dihydroxy stearate in step (2) has a molecular weight of 700-1000, and the dihydroxy-terminated polydimethylsiloxane has a molecular weight of 4000-5000.

5. The method for preparing the photocurable silicone-modified waterborne acrylic coating as described in claim 1, characterized in that: The amount of dimethylolbutyric acid used in step (2) is 2-5% of the total mass of the raw materials in step (2), and the amount of dibutyltin dilaurate catalyst used is 0.1-0.5% of the total mass of the raw materials in step (2).

6. The method for preparing the photocurable silicone-modified waterborne acrylic coating as described in claim 1, characterized in that: The isocyanate mentioned in step (2) is one of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and lysine diisocyanate.

7. The method for preparing the photocurable silicone-modified waterborne acrylic coating as described in claim 1, characterized in that: The amount of the capping agent containing modified acrylate in step (2) is 3-5% of the total mass of the raw materials in step (2); the overall reaction environment pH in step (2) is controlled at 3-5.

8. The method for preparing the photocurable silicone-modified waterborne acrylic coating as described in claim 1, characterized in that: The emulsifier in step (3) is one of polyoxyethylene ether, polyoxypropylene ether, polyol fatty acid ester, and polyvinyl alcohol; the amount of emulsifier is 2-5% of the total mass of the raw materials in step (3), the amount of butyl methacrylate is 5-10% of the total mass of the raw materials in step (3), and the amount of emulsion is 80-90% of the total mass of the raw materials in step (3).

9. The method for preparing the photocurable silicone-modified waterborne acrylic coating as described in claim 1, characterized in that: The photoinitiator in step (4) is one of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, 1-hydroxycyclohexylphenyl ketone, and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone, and its amount is 3.5% of the emulsion mass.

10. A photocurable silicone-modified waterborne acrylic coating prepared by the method according to any one of claims 1-9.

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