Aqueous polyurethane coating and method for its preparation

Abstract

The application discloses a kind of water-based polyurethane coating and preparation method thereof, it is related to paint technical field.The water-based polyurethane coating prepared in the application includes component A and component B, component A includes modified polyurethane dispersion, wetting agent, defoaming agent, thickening agent, stabilizer;Component B includes modified silica, dispersant, wetting agent;The modified polyurethane dispersion is prepared by isofuroxone diisocyanate, phosphorus-containing dihydric alcohol, propargyl alcohol, dimethylol butyric acid reaction;The modified silica is the silica that is wrapped by chitosan, after aldehyde group is formed, and functional monomer grafting, and the gamma-seleno butyrolactone obtained by reaction again.The water-based polyurethane coating prepared in the application has good flame-retardant, antibacterial, anti-aging and self-repairing performance.

Description

Technical Field

[0001] This invention relates to the field of coatings, specifically to a waterborne polyurethane coating and its preparation method. Background Technology

[0002] Waterborne polyurethane coatings use water as the dispersion medium and have advantages such as low VOC, non-flammability, non-toxicity, low odor, safe operation, strong adhesion after film formation, acid and alkali resistance, flexibility and wear resistance, and convenient construction. They have been widely used in automotive interior and exterior parts, wooden furniture, building interior and exterior walls, textile finishing, metal corrosion protection, UV laser engraving topcoat and other fields. However, its main chain contains a large number of flammable hydrocarbon structures with a low limiting oxygen index, and it ignites upon contact with fire, releasing a large amount of heat and smoke. Therefore, it must be endowed with high-efficiency flame-retardant properties in automotive, rail transportation, and high-rise building decoration. Its aromatic hard segments are easily broken by ultraviolet light and heat-oxidation, leading to coating chalking, loss of gloss, and a sharp drop in mechanical properties. When used outdoors, anti-aging properties must be improved simultaneously. The water-based system is rich in hydrophilic soft segments and surfactants. After film formation, there is microphase separation and microporous channels. After daily scratches and cracks, the medium can easily penetrate, causing corrosion and bacterial growth. Therefore, self-healing function is required to quickly seal cracks and extend life. The coating itself is rich in polyols and amine nutrient groups, which are prone to bacterial and mold growth in humid environments. In medical equipment, food packaging, and water purification components, it must be endowed with broad-spectrum and long-lasting antibacterial capabilities. Summary of the Invention

[0003] The purpose of this invention is to provide a waterborne polyurethane coating and its preparation method to solve the problems existing in the prior art.

[0004] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0005] A method for preparing a waterborne polyurethane coating includes the following preparation steps:

[0006] (1) Phosphorus oxychloride and 4-acetylenephenol were reacted to obtain a phosphorus-containing monomer; tartaric acid and the phosphorus-containing monomer were reacted to obtain a phosphorus-containing dicarboxylic acid; the phosphorus-containing dicarboxylic acid and neopentyl glycol were polymerized to obtain a phosphorus-containing diol;

[0007] (2) The modified polyurethane dispersion was obtained by polymerizing isoflurane diisocyanate, phosphorus-containing diol and dimethylolbutyric acid and then end-capping with propargyl alcohol.

[0008] (3) React 3-amino-1,2,4-triazole, p-nitrobenzaldehyde, and 1,3-cyclohexanedione to obtain a functional monomer precursor; reduce the functional monomer precursor to obtain the functional monomer;

[0009] (4) Chitosan-encapsulated silica was oxidized with sodium periodate to obtain pretreated silica;

[0010] (5) Pretreated silica and functional monomers are reacted to obtain pre-modified silica; pre-modified silica and γ-selenobutyrolactone are reacted to obtain modified silica;

[0011] (6) Weigh the following components: modified polyurethane dispersion, wetting agent, defoamer, thickener, and stabilizer, and mix them to obtain component A; weigh the following components: modified silica, dispersant, wetting agent, and pure water, and mix them to obtain component B; mix component A and component B to obtain waterborne polyurethane coating.

[0012] As an optimization, the preparation method of the phosphorus-containing diol in step (1) is as follows: tartaric acid and glacial acetic acid are mixed, heated to 105-115℃ and stirred for 10-20 min, then phosphorus-containing monomer is added, and the reaction is carried out for 10-12 h. After removing the solvent glacial acetic acid by rotary evaporation under reduced pressure, phosphorus-containing dicarboxylic acid is obtained; the mass ratio of tartaric acid to glacial acetic acid is 1:(30-40); the molar ratio of tartaric acid to phosphorus-containing monomer is 1:(2.1-2.2);

[0013] Under nitrogen protection, phosphorus-containing dicarboxylic acid, neopentyl glycol, and dibutyltin dilaurate are mixed and heated to 120-130℃ for 4-5 hours. Then, the mixture is cooled to 105℃ and the pressure is reduced to a vacuum of 0.08 MPa for 2-3 hours. After cooling to room temperature, phosphorus-containing diol is obtained. The mass ratio of phosphorus-containing dicarboxylic acid, neopentyl glycol, and dibutyltin dilaurate is 1:(0.5-0.6):(0.01-0.02).

[0014] As an optimization, the preparation method of the phosphorus-containing monomer is as follows: aluminum trichloride and phosphorus oxychloride are mixed, heated to 50-60℃ and stirred for 10 min to uniformly disperse the aluminum trichloride; then 4-acetylenephenol is pre-dissolved in dichloroethane and added dropwise to the reaction system at a rate of 0.5 mL / min, maintaining the temperature of the reaction system ≤70℃. After the addition is complete, the temperature is raised to 70-80℃, and the reaction is continued to be carried out under constant temperature stirring for 13-15 h; after the reaction is completed, the mixture is cooled in an ice-water bath. The reaction was quenched with pure water, and stirring was continued for 30 minutes. The solid was removed by filtration. The filtrate was dried with anhydrous sodium sulfate and then transferred to a distillation apparatus. The solvent and low-boiling substances were first removed by distillation under normal pressure. The fraction containing phosphorus was collected at 150-175℃ under reduced pressure of 3 mmHg. The molar ratio of 4-acetylenephenol to phosphorus oxychloride was (2-2.2):1. The mass ratio of 4-acetylenephenol, aluminum trichloride, and dichloroethane was 1:(0.025-0.035):(10-12).

[0015] As an optimization, the preparation method of the modified polyurethane dispersion in step (2) is as follows: isoflurane diisocyanate, phosphorus-containing diol and dibutyltin dilaurate are mixed, heated to 85-90℃ and reacted for 2-3 hours, dimethylolbutyric acid is added and cooled to 75-80℃ and reacted for 2-3 hours, then cooled to 60-65℃, propargyl alcohol is added to end-cap and reacted for 2-3 hours, triethylamine is added to adjust the pH to 7-7.5, acetone is added and stirred for 15 minutes to adjust the viscosity, then cooled to room temperature, pure water is added and stirred at high speed at 2000-2500 r / min for 30-40 minutes, and acetone is removed in a rotary evaporator to obtain the modified polyurethane dispersion.

[0016] As an optimization, the amounts of isophorone diisocyanate, phosphorus-containing diol, dibutyltin dilaurate, dimethylolbutyric acid, propargyl alcohol, acetone, triethylamine, and purified water are as follows (by mass): 10 parts isophorone diisocyanate, 18-25 parts phosphorus-containing diol, 0.05-0.1 parts dibutyltin dilaurate, 4-6 parts dimethylolbutyric acid, 1-1.2 parts propargyl alcohol, 25-35 parts acetone, 1-2 parts triethylamine, and 50-60 parts purified water.

[0017] As an optimization, the preparation method of the functional monomer in step (3) is as follows: 3-amino-1,2,4-triazole, p-nitrobenzaldehyde, 1,3-cyclohexanedione, cerium ammonium nitrate, and pure water are mixed in a molar ratio of 1:(1.02-1.05):(1.02-1.05):(1.5-1.6):(10-12) and placed in a microwave reactor. The mixture is irradiated at 60-70℃ for 2-5 minutes with a power of 150W to obtain the functional monomer precursor. The functional monomer precursor, ethyl acetate, and 5% platinum-carbon catalyst are mixed in a mass ratio of 1:(10-12):(0.1-0.2) and reacted at room temperature for 3-4 hours under a hydrogen atmosphere and a pressure of 0.3MPa to obtain the functional monomer.

[0018] As an optimization, the preparation method of the pretreated silica in step (4) is as follows: chitosan and 0.3wt% acetic acid solution are mixed at a mass ratio of 1:100 to obtain a chitosan solution; silica, chitosan solution and glutaraldehyde are mixed at a mass ratio of 1:(100-150):(20-30); the mixture is heated to 60-70℃ and stirred for 2-3 hours to obtain chitosan-coated silica; the chitosan-coated silica is dispersed in an acetate-sodium acetate buffer solution with a pH of 4.0, ultrasonically dispersed, sodium periodate is added under light-protected conditions, stirred at room temperature for 2-3 hours, and ethylene glycol is added to obtain pretreated silica; the mass ratio of chitosan-coated silica, acetate-sodium acetate buffer solution, sodium periodate and ethylene glycol is 1:(50-60):(1-1.2):(2-3);

[0019] As an optimization, the preparation method of the modified silica in step (5) is as follows: pretreated silica, functional monomer, and tetrahydrofuran are mixed at a mass ratio of 1:(0.2-0.3):(50-60) and reacted at 50-60℃ for 5-6h to obtain pre-modified silica; pre-modified silica, tetrahydrofuran, and γ-selenobutyrolactone are ultrasonically mixed at a mass ratio of 1:(30-40):(0.3-0.4) and reacted at room temperature under nitrogen protection and in the dark for 10-12h to obtain modified silica.

[0020] As an optimization, the preparation method of the waterborne polyurethane coating in step (6) is as follows: Weigh the following components: by mass parts, 100 parts of modified polyurethane dispersion, 0.5-1 parts of wetting agent, 0.4-0.8 parts of defoamer, 1-2 parts of thickener, and 0.2-0.4 parts of stabilizer, and mix them to obtain component A;

[0021] Weigh the following components: by mass, 5-10 parts of modified silica, 1-2 parts of dispersant, and 0.1-0.5 parts of wetting agent are mixed evenly, and the solid content is adjusted to 20%-30% with pure water to obtain component B; mix component A and component B evenly to obtain waterborne polyurethane coating.

[0022] The present invention also provides an aqueous polyurethane coating prepared according to any of the preparation methods described herein.

[0023] As an optimization, the structure of the functional unit is shown in the figure below:

[0024] .

[0025] The waterborne polyurethane coating prepared by this invention comprises component A and component B. Component A includes a modified polyurethane dispersion, a wetting agent, a defoamer, a thickener, and a stabilizer; component B includes modified silica, a dispersant, and a wetting agent. The modified polyurethane dispersion is prepared by reacting isoflurane diisocyanate, a phosphorus-containing diol, propargyl alcohol, and dimethylolbutyric acid. The modified silica is obtained by aldehyde-encapsulating silica with chitosan, grafting it with functional monomers, and then reacting it with γ-selenobutyrolactone.

[0026] First, phosphorus oxychloride and 4-acetylenephenol are reacted to generate a phosphorus-containing monomer containing two acetylene phenyl groups by controlling the molar ratio. The phosphorus-containing monomer is then reacted with tartaric acid to generate a phosphorus-containing dicarboxylic acid. The phosphorus-containing dicarboxylic acid and neopentyl glycol are then transesterified to generate a polyester-type phosphorus-containing diol, which participates in the polymerization of polyurethane. The phosphorus-containing diol is covalently embedded in the polyurethane backbone. When heated, phosphorus preferentially decomposes to generate a glassy phosphate layer, which isolates the heat source and cuts off the combustion free radical chain, achieving long-lasting intrinsic flame retardancy and introducing acetylene groups. Using propargyl alcohol to end-cap polyurethane can further increase the acetylene content of the polyurethane.

[0027] Secondly, functional monomers containing triazole and quinazolinone rings were prepared simply and rapidly via microwave reaction and nitro reduction using 3-amino-1,2,4-triazole, p-nitrobenzaldehyde, and 1,3-cyclohexanedione. The triazole ring endowed the material with broad-spectrum antibacterial activity, while the electron-rich conjugated structure of the quinazolinone ring could capture and stabilize active free radicals, forming hydrogen atom transfer channels, thereby chemically terminating the oxidation chain reaction and providing long-lasting antioxidant protection.

[0028] Silica, as a common inorganic filler, can impart excellent wear resistance to polyurethane. When chitosan-encapsulated silica is dispersed in a polyurethane matrix, the hydroxyl groups on the chitosan shell become hydrogen-bonded with the polyurethane chain segments, instantly increasing the filler-matrix affinity and ensuring uniform suspension of silica particles without sedimentation. The aldehyde groups generated after chitosan oxidation with sodium periodate condense with the amino groups of functional monomers, firmly anchoring antibacterial and antioxidant functional groups to the particle surface, thus giving the coating durable antibacterial and free radical scavenging capabilities. Subsequently, γ-selenolactone is present on the residual amino and hydroxyl groups of chitosan... Under the co-catalysis of [unclear], ring-opening occurs, forming selenool side chains. These selenools undergo reversible nucleophilic addition with the abundant alkynyl groups in polyurethane, constructing a dynamic selenyl acetal network at room temperature. When scratches appear, the bonds break, and after interface slippage, they reform, automatically "stitching" the cracks and restoring transparency and barrier properties simultaneously. The film-forming properties of chitosan itself give the particles a flexible shell, buffering external impacts and preventing brittleness and powdering. Ultimately, the coating possesses multiple functions, including high transparency, high hardness, long-term anti-settling, and self-healing. Moreover, chitosan can still be biodegraded after its life cycle, reducing environmental impact. Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0030] The silica particle size used in the following examples and comparative examples is 200 nm.

[0031] Example 1: A waterborne polyurethane coating, comprising the following preparation steps:

[0032] (1) Under nitrogen protection, aluminum trichloride and phosphorus oxychloride were mixed, heated to 60°C in an oil bath and stirred for 10 min to disperse aluminum trichloride evenly; then 4-acetylenephenol was pre-dissolved in dichloroethane and added dropwise to the reaction system at a rate of 0.5 mL / min, maintaining the temperature of the reaction system ≤70°C. After the addition was completed, the temperature was raised to 80°C and the reaction was continued to be stirred at a constant temperature for 15 h; after the reaction was completed, pure water was added to quench the reaction under ice-water bath cooling, and stirring was continued for 30 min. The solid was removed by suction filtration, and the filtrate was dried with anhydrous sodium sulfate and transferred to a distillation apparatus. The solvent and low-boiling substances were first removed by atmospheric pressure, and the fraction containing phosphorus was collected at 150-175°C under reduced pressure of 3 mmHg to obtain phosphorus-containing monomer; the molar ratio of 4-acetylenephenol to phosphorus oxychloride was 2:1; the mass ratio of 4-acetylenephenol, anhydrous aluminum trichloride and dichloroethane was 1:0.025:10;

[0033] Tartaric acid and glacial acetic acid were mixed, heated to 115℃ and stirred for 20 min, then phosphorus-containing monomers were added and reacted for 12 h. After removing the solvent glacial acetic acid by rotary evaporation under reduced pressure, phosphorus-containing dicarboxylic acid was obtained. The mass ratio of tartaric acid to glacial acetic acid was 1:30, and the molar ratio of tartaric acid to phosphorus-containing monomers was 1:2.1.

[0034] Under nitrogen protection, phosphorus-containing diacid, neopentyl glycol, and dibutyltin dilaurate were mixed, heated to 130°C, and reacted for 5 hours. Then, the temperature was lowered to 105°C and the pressure was reduced to a vacuum of 0.08 MPa, and the reaction was carried out for 3 hours. After cooling to room temperature, phosphorus-containing diol was obtained. The mass ratio of phosphorus-containing diacid, neopentyl glycol, and dibutyltin dilaurate was 1:0.5:0.01.

[0035] (2) Mix isoflurane diisocyanate, phosphorus-containing diol and dibutyltin dilaurate, heat to 90°C and react for 3 hours, add dimethylolbutyric acid and cool to 80°C and react for 3 hours, cool to 65°C, add propargyl alcohol to end-cap and react for 3 hours, add triethylamine to adjust pH to 7.5, add acetone and stir for 15 minutes to adjust viscosity, cool to room temperature, add pure water and stir at high speed at 2500 r / min for 40 minutes, remove acetone in a rotary evaporator to obtain modified polyurethane dispersion;

[0036] The amounts of isoflurane diisocyanate, phosphorus-containing diol, dibutyltin dilaurate, dimethylolbutyric acid, propargyl alcohol, acetone, triethylamine, and purified water are calculated by mass parts as follows: 10 parts isoflurane diisocyanate, 18 parts phosphorus-containing diol, 0.05 parts dibutyltin dilaurate, 4 parts dimethylolbutyric acid, 1 part propargyl alcohol, 25 parts acetone, 1 part triethylamine, and 50 parts purified water.

[0037] (3) 3-amino-1,2,4-triazole, p-nitrobenzaldehyde, 1,3-cyclohexanedione, cerium ammonium nitrate, and pure water were mixed in a molar ratio of 1:1.02:1.02:1.5:10 and placed in a microwave reactor. The mixture was irradiated at 70°C for 5 min with a power of 150 W. After washing with pure water and vacuum drying, the functional monomer precursor was obtained. The functional monomer precursor, ethyl acetate, and 5% platinum-carbon catalyst were mixed in a mass ratio of 1:10:0.1 and reacted at room temperature for 4 h under a hydrogen atmosphere and a pressure of 0.3 MPa. After the reaction was completed, the mixture was filtered, washed, and dried to obtain the functional monomer.

[0038] (4) Chitosan and 0.3wt% acetic acid solution were mixed at a mass ratio of 1:100 to obtain chitosan solution. Silica, chitosan solution and glutaraldehyde were mixed at a mass ratio of 1:100:20. The mixture was heated to 70℃ and stirred for 3h. After the reaction was completed, the mixture was filtered and washed successively with petroleum ether, ethanol and pure water. The mixture was then vacuum dried at 50℃ to obtain chitosan-coated silica. Chitosan-coated silica was dispersed in an acetate-sodium acetate buffer solution with a pH of 4.0 and ultrasonically dispersed. Sodium periodate was added under light-protected conditions and stirred at room temperature for 3h. Ethylene glycol was added and the mixture was filtered, washed and dried to obtain pretreated silica. The mass ratio of chitosan-coated silica, acetate-sodium acetate buffer solution, sodium periodate and ethylene glycol was 1:50:1:2.

[0039] (5) Pretreated silica, functional monomers and tetrahydrofuran were mixed at a mass ratio of 1:0.2:50 and reacted at 60°C for 6 hours. After filtration, washing and drying, pre-modified silica was obtained. Pre-modified silica, tetrahydrofuran and γ-selenobutyrolactone were ultrasonically mixed at a mass ratio of 1:30:0.3 and reacted at room temperature under nitrogen protection and in the dark for 12 hours. After filtration, washing and drying, modified silica was obtained.

[0040] (6) Weigh the following components: by mass parts, 100 parts of modified polyurethane dispersion, 0.5 parts of wetting agent BYK-346, 0.4 parts of defoamer TEGO Foamex 810, 1 part of thickener RM-2020 NPR, and 0.2 parts of stabilizer AMP-95, and mix them to obtain component A;

[0041] Weigh the following components: by mass, 5 parts modified silica, 1 part dispersant Disperbyk-190, and 0.1 parts wetting agent BYK-346 are mixed and the solid content is adjusted to 20% with pure water to obtain component B; mix component A and component B to obtain waterborne polyurethane coating.

[0042] Example 2: A waterborne polyurethane coating, comprising the following preparation steps:

[0043] (1) Under nitrogen protection, aluminum trichloride and phosphorus oxychloride were mixed, heated to 55°C in an oil bath and stirred for 10 min to disperse aluminum trichloride evenly; then 4-acetylenephenol was pre-dissolved in dichloroethane and added dropwise to the reaction system at a rate of 0.5 mL / min, maintaining the temperature of the reaction system ≤70°C. After the addition was completed, the temperature was raised to 75°C and the reaction was continued to be stirred at a constant temperature for 14 h; after the reaction was completed, pure water was added to quench the reaction under ice-water bath cooling, and stirring was continued for 30 min. The solid was removed by suction filtration, and the filtrate was dried with anhydrous sodium sulfate and transferred to a distillation apparatus. The solvent and low-boiling substances were first removed by atmospheric pressure, and the fraction containing phosphorus was collected at 150-175°C under reduced pressure of 3 mmHg to obtain phosphorus-containing monomer; the molar ratio of 4-acetylenephenol and phosphorus oxychloride was 2.1:1; the mass ratio of 4-acetylenephenol, anhydrous aluminum trichloride and dichloroethane was 1:0.03:11;

[0044] Tartaric acid and glacial acetic acid were mixed, heated to 110℃ and stirred for 15 min, then phosphorus-containing monomers were added and reacted for 11 h. After removing the solvent glacial acetic acid by rotary evaporation under reduced pressure, phosphorus-containing dicarboxylic acid was obtained. The mass ratio of tartaric acid to glacial acetic acid was 1:35, and the molar ratio of tartaric acid to phosphorus-containing monomers was 1:2.15.

[0045] Under nitrogen protection, phosphorus-containing diacid, neopentyl glycol, and dibutyltin dilaurate were mixed, heated to 125°C, and reacted for 4.5 h. Then, the temperature was lowered to 105°C and the pressure was reduced to a vacuum of 0.08 MPa, and the reaction was carried out for 2.5 h. After cooling to room temperature, phosphorus-containing diol was obtained. The mass ratio of phosphorus-containing diacid, neopentyl glycol, and dibutyltin dilaurate was 1:0.55:0.01.

[0046] (2) Mix isoflurane diisocyanate, phosphorus-containing diol and dibutyltin dilaurate, heat to 87°C and react for 2.5 h, add dimethylolbutyric acid and cool to 77°C and react for 2.5 h, cool to 63°C, add propargyl alcohol to end-cap and react for 2.5 h, add triethylamine to adjust pH to 7.3, add acetone and stir for 15 min to adjust viscosity, cool to room temperature, add pure water and stir at high speed at 2300 r / min for 35 min, remove acetone in a rotary evaporator to obtain modified polyurethane dispersion;

[0047] The amounts of isoflurane diisocyanate, phosphorus-containing diol, dibutyltin dilaurate, dimethylolbutyric acid, propargyl alcohol, acetone, triethylamine, and purified water are as follows (by mass parts): 10 parts isoflurane diisocyanate, 20 parts phosphorus-containing diol, 0.07 parts dibutyltin dilaurate, 5 parts dimethylolbutyric acid, 1.1 parts propargyl alcohol, 30 parts acetone, 1.5 parts triethylamine, and 55 parts purified water.

[0048] (3) 3-amino-1,2,4-triazole, p-nitrobenzaldehyde, 1,3-cyclohexanedione, cerium ammonium nitrate, and pure water were mixed in a molar ratio of 1:1.03:1.04:1.55:11 and placed in a microwave reactor. The mixture was irradiated at 65°C for 3 min with a power of 150 W. After washing with pure water and vacuum drying, the functional monomer precursor was obtained. The functional monomer precursor, ethyl acetate, and 5% platinum-carbon catalyst were mixed in a mass ratio of 1:11:0.15 and reacted at room temperature for 3.5 h under a hydrogen atmosphere and a pressure of 0.3 MPa. After the reaction was completed, the mixture was filtered, washed, and dried to obtain the functional monomer.

[0049] (4) Chitosan and 0.3wt% acetic acid solution were mixed at a mass ratio of 1:100 to obtain a chitosan solution. Silica, chitosan solution and glutaraldehyde were mixed at a mass ratio of 1:120:25. The mixture was heated to 65℃ and stirred for 2.5h. After the reaction was completed, the mixture was filtered and washed successively with petroleum ether, ethanol and pure water. The mixture was then vacuum dried at 50℃ to obtain chitosan-coated silica. Chitosan-coated silica was dispersed in an acetate-sodium acetate buffer solution with a pH of 4.0 and ultrasonically dispersed. Sodium periodate was added under light-protected conditions and stirred at room temperature for 2.5h. Ethylene glycol was added, and the mixture was filtered, washed and dried to obtain pretreated silica. The mass ratio of chitosan-coated silica, acetate-sodium acetate buffer solution, sodium periodate and ethylene glycol was 1:55:1.1:2.5.

[0050] (5) Pretreated silica, functional monomers and tetrahydrofuran were mixed at a mass ratio of 1:0.25:55 and reacted at 55°C for 5.5 h. After filtration, washing and drying, pre-modified silica was obtained. Pre-modified silica, tetrahydrofuran and γ-selenobutyrolactone were ultrasonically mixed at a mass ratio of 1:35:0.35 and reacted at room temperature under nitrogen protection and in the dark for 11 h. After filtration, washing and drying, modified silica was obtained.

[0051] (6) Weigh the following components: by mass parts, 100 parts of modified polyurethane dispersion, 0.8 parts of wetting agent BYK-346, 0.6 parts of defoamer TEGO Foamex 810, 1.5 parts of thickener RM-2020 NPR, and 0.3 parts of stabilizer AMP-95, and mix them to obtain component A;

[0052] Weigh the following components: by mass, 7 parts modified silica, 1.5 parts dispersant Disperbyk-190, and 0.4 parts wetting agent BYK-346 are mixed and the solid content is adjusted to 25% with pure water to obtain component B; mix component A and component B to obtain waterborne polyurethane coating.

[0053] Example 3: A waterborne polyurethane coating, comprising the following preparation steps:

[0054] (1) Under nitrogen protection, aluminum trichloride and phosphorus oxychloride were mixed, heated to 50°C in an oil bath and stirred for 10 min to disperse aluminum trichloride evenly; then 4-acetylenephenol was pre-dissolved in dichloroethane and added dropwise to the reaction system at a rate of 0.5 mL / min, maintaining the temperature of the reaction system ≤70°C. After the addition was completed, the temperature was raised to 75°C and the reaction was continued to be stirred at a constant temperature for 14 h; after the reaction was completed, pure water was added to quench the reaction under ice-water bath cooling, and stirring was continued for 30 min. The solid was removed by suction filtration, and the filtrate was dried with anhydrous sodium sulfate and transferred to a distillation apparatus. The solvent and low-boiling substances were first removed by atmospheric pressure, and the fraction containing phosphorus was collected at 150-175°C under reduced pressure of 3 mmHg to obtain phosphorus-containing monomer; the molar ratio of 4-acetylenephenol to phosphorus oxychloride was 2.2:1; the mass ratio of 4-acetylenephenol, anhydrous aluminum trichloride and dichloroethane was 1:0.035:12;

[0055] Tartaric acid and glacial acetic acid were mixed, heated to 105℃ and stirred for 10 min, then phosphorus-containing monomers were added and reacted for 10 h. After removing the solvent glacial acetic acid by rotary evaporation under reduced pressure, phosphorus-containing dicarboxylic acid was obtained. The mass ratio of tartaric acid to glacial acetic acid was 1:40, and the molar ratio of tartaric acid to phosphorus-containing monomers was 1:2.2.

[0056] Under nitrogen protection, phosphorus-containing diacid, neopentyl glycol, and dibutyltin dilaurate were mixed, heated to 120°C, and reacted for 4 hours. Then, the temperature was lowered to 105°C and the pressure was reduced to a vacuum of 0.08 MPa, and the reaction was carried out for 2 hours. After cooling to room temperature, phosphorus-containing diol was obtained. The mass ratio of phosphorus-containing diacid, neopentyl glycol, and dibutyltin dilaurate was 1:0.6:0.02.

[0057] (2) Mix isoflurane diisocyanate, phosphorus-containing diol and dibutyltin dilaurate, heat to 85°C and react for 2 hours, add dimethylolbutyric acid and cool to 75°C and react for 2 hours, cool to 60°C, add propargyl alcohol to end-cap and react for 2 hours, add triethylamine to adjust pH to 7, add acetone and stir for 15 minutes to adjust viscosity, cool to room temperature, add pure water and stir at 2000 r / min for 30 minutes, remove acetone in a rotary evaporator to obtain modified polyurethane dispersion;

[0058] The amounts of isoflurane diisocyanate, phosphorus-containing diol, dibutyltin dilaurate, dimethylolbutyric acid, propargyl alcohol, acetone, triethylamine, and purified water are calculated by mass parts as follows: 10 parts isoflurane diisocyanate, 25 parts phosphorus-containing diol, 0.1 parts dibutyltin dilaurate, 6 parts dimethylolbutyric acid, 1.2 parts propargyl alcohol, 35 parts acetone, 2 parts triethylamine, and 60 parts purified water.

[0059] (3) 3-amino-1,2,4-triazole, p-nitrobenzaldehyde, 1,3-cyclohexanedione, cerium ammonium nitrate, and pure water were mixed in a molar ratio of 1:1.05:1.05:1.6:12 and placed in a microwave reactor. The mixture was irradiated at 60°C for 2 min with a power of 150 W. After washing with pure water and vacuum drying, the functional monomer precursor was obtained. The functional monomer precursor, ethyl acetate, and 5% platinum-carbon catalyst were mixed in a mass ratio of 1:12:0.2 and reacted at room temperature for 3 h under a hydrogen atmosphere and a pressure of 0.3 MPa. After the reaction was completed, the mixture was filtered, washed, and dried to obtain the functional monomer.

[0060] (4) Chitosan and 0.3wt% acetic acid solution were mixed at a mass ratio of 1:100 to obtain chitosan solution. Silica, chitosan solution and glutaraldehyde were mixed at a mass ratio of 1:150:30. The mixture was heated to 60℃ and stirred for 2 hours. After the reaction was completed, the mixture was filtered and washed successively with petroleum ether, ethanol and pure water. The mixture was then vacuum dried at 50℃ to obtain chitosan-coated silica. Chitosan-coated silica was dispersed in an acetate-sodium acetate buffer solution with a pH of 4.0 and ultrasonically dispersed. Sodium periodate was added under light-protected conditions and stirred at room temperature for 2 hours. Ethylene glycol was added and the mixture was filtered, washed and dried to obtain pretreated silica. The mass ratio of chitosan-coated silica, acetate-sodium acetate buffer solution, sodium periodate and ethylene glycol was 1:60:1.2:3.

[0061] (5) Pretreated silica, functional monomers and tetrahydrofuran were mixed at a mass ratio of 1:0.3:60 and reacted at 50°C for 5 h. After filtration, washing and drying, pre-modified silica was obtained. Pre-modified silica, tetrahydrofuran and γ-selenobutyrolactone were ultrasonically mixed at a mass ratio of 1:40:0.4 and reacted at room temperature under nitrogen protection and in the dark for 10 h. After filtration, washing and drying, modified silica was obtained.

[0062] (6) Weigh the following components: by mass parts, 100 parts of modified polyurethane dispersion, 1 part of wetting agent BYK-346, 0.8 parts of defoamer TEGO Foamex 810, 2 parts of thickener RM-2020 NPR, and 0.4 parts of stabilizer AMP-95, and mix them to obtain component A;

[0063] Weigh the following components: by mass, 10 parts of modified silica, 2 parts of dispersant Disperbyk-190, and 0.5 parts of wetting agent BYK-346 are mixed and the solid content is adjusted to 30% with pure water to obtain component B; mix component A and component B to obtain waterborne polyurethane coating.

[0064] Comparative Example 1:

[0065] The difference between the preparation method of the waterborne polyurethane coating of Comparative Example 1 and Example 2 is that the phosphorus-containing diol is replaced with polycarbonate diol with a molecular weight of 2000. Specifically, step (1) is omitted, and step (2) is modified as follows: isoflurane diisocyanate, polycarbonate diol and dibutyltin dilaurate are mixed, heated to 87°C and reacted for 2.5 h, dimethylolbutyric acid is added and cooled to 77°C and reacted for 2.5 h, cooled to 63°C, propargyl alcohol is added to end-cap and reacted for 2.5 h, triethylamine is added to adjust the pH to 7.3, acetone is added and stirred for 15 min to adjust the viscosity, cooled to room temperature, pure water is added and stirred at high speed at 2300 r / min for 35 min, and acetone is removed in a rotary evaporator to obtain the modified polyurethane dispersion;

[0066] The amounts of isophorone diisocyanate, polycarbonate diol, dibutyltin dilaurate, dimethylolbutyric acid, propargyl alcohol, acetone, triethylamine, and purified water are as follows (by mass): 10 parts isophorone diisocyanate, 20 parts polycarbonate diol, 0.07 parts dibutyltin dilaurate, 5 parts dimethylolbutyric acid, 1.1 parts propargyl alcohol, 30 parts acetone, 1.5 parts triethylamine, and 55 parts purified water. The rest is the same as in step (2).

[0067] Comparative Example 2:

[0068] The difference between the preparation method of the waterborne polyurethane coating of Comparative Example 2 and Example 2 is that it does not contain functional monomers, specifically step (3) is not included. Step (5) is modified as follows: pretreated silica, tetrahydrofuran and γ-selenobutyrolactone are ultrasonically mixed at a mass ratio of 1:35:0.35 and reacted at room temperature under nitrogen protection and in the dark for 11 hours. Modified silica is obtained by filtration, washing and drying.

[0069] Comparative Example 3:

[0070] The difference between the preparation method of the waterborne polyurethane coating of Comparative Example 3 and Example 2 is that it does not react with γ-selenobutyrolactone. Specifically, step (5) is modified as follows: pretreated silica, functional monomer and tetrahydrofuran are mixed in a mass ratio of 1:0.25:55, reacted at 55°C for 5.5 h, and then filtered, washed and dried to obtain modified silica.

[0071] Test Example 1:

[0072] Anti-aging performance testing:

[0073] Test method: The coatings prepared in the examples and comparative examples were poured into polytetrafluoroethylene molds and dried at 50°C to form a film. After curing, the films were demolded and cut into dumbbell-shaped samples with a thickness of 1 mm. Tensile testing was performed on the samples at room temperature using a mechanical tensile testing machine at a tensile rate of 10 mm / min. The samples were then placed in a UV aging chamber for 15 days, and then removed and subjected to tensile testing again. The temperature in the UV aging chamber was 50°C, the wavelength of the UV light was 340 nm, the lamp power was 40 W, and the distance between the film and the light source was 50 mm. The tensile strength retention rate was calculated. The results are shown in Table 1.

[0074] Self-healing performance test:

[0075] Test method: The coatings prepared in the examples and comparative examples were poured into polytetrafluoroethylene molds and dried at 50°C to form a film. After curing, the films were demolded and cut into dumbbell-shaped samples with a thickness of 1 mm. Tensile tests were performed on the samples at room temperature using a mechanical tensile testing machine at a tensile rate of 10 mm / min. A 0.5 mm scratch was made in the middle of the sample with a blade. After heating at 50°C for 1.5 hours, the tensile test was performed again, and the tensile strength retention rate was calculated. The results are shown in Table 1.

[0076] Table 1:

[0077] ;

[0078] A comparison of the experimental data of Examples 1-3 and Comparative Examples 1-3 in Table 1 reveals that the waterborne polyurethane coating prepared by the present invention has good anti-aging properties and self-healing properties.

[0079] By comparison, the anti-aging and self-repair properties of Examples 1-3 are superior to those of the comparative example, indicating that the functional monomers containing triazole and quinazolinone rings can be prepared simply and rapidly by using 3-amino-1,2,4-triazole, p-nitrobenzaldehyde, and 1,3-cyclohexanedione through microwave reaction and nitro reduction. The electron-rich conjugated structure of the quinazolinone ring can capture and stabilize active free radicals, forming hydrogen atom transfer channels, thereby chemically terminating the oxidation chain reaction and providing long-lasting antioxidant protection.

[0080] The aldehyde groups generated by the oxidation of chitosan with sodium periodate condense with the amino groups of the functional monomers, firmly anchoring the antioxidant functional groups on the particle surface, thus giving the coating a long-lasting free radical scavenging ability. Subsequently, γ-selenobutyrolactone undergoes ring-opening under the co-catalysis of the residual amino and hydroxyl groups of chitosan to form selenool side chains. These selenools undergo reversible nucleophilic addition with the abundant alkynyl groups in polyurethane, which can construct a dynamic selenyl acetal network at room temperature. The presence of selenium can also endow the material with certain antioxidant properties.

[0081] Test Example 2:

[0082] Antibacterial performance testing:

[0083] Test method: The antibacterial rate of the waterborne polyurethane coatings prepared in the examples and comparative examples was tested according to the standard GB / T 21866–2008 "Determination of antibacterial properties and antibacterial effects of antibacterial coatings (films)". The results are shown in Table 2.

[0084] Table 2:

[0085] ;

[0086] A comparison of the experimental data of Examples 1-3 and Comparative Examples 1-3 in Table 2 shows that the waterborne polyurethane coating prepared by the present invention has good antibacterial properties.

[0087] By comparison, the antibacterial rates of Examples 1-3 were greater than those of Comparative Examples 1-2, indicating that functional monomers containing triazole and quinazolinone rings can be prepared simply and rapidly by using 3-amino-1,2,4-triazole, p-nitrobenzaldehyde, and 1,3-cyclohexanedione through microwave reaction and nitro reduction. The triazole ring endows the material with broad-spectrum antibacterial activity.

[0088] Test Example 3:

[0089] Flame retardant performance test: Using GB / T2406 standard, the coatings prepared in the examples and comparative examples were poured into polytetrafluoroethylene molds and dried at room temperature to form a film. After curing, the films were demolded and cut into Type I samples of 100mm*10mm*4mm. The oxygen index of the samples was tested at room temperature; the results are shown in Table 3.

[0090] Table 3:

[0091] ;

[0092] A comparison of the experimental data of Examples 1-3 and Comparative Examples 1-3 in Table 3 shows that the waterborne polyurethane coating prepared by the present invention has good flame retardant properties.

[0093] By comparison, the flame retardant performance of Examples 1-3 is better than that of the comparative example. This indicates that by reacting phosphorus oxychloride and 4-acetylenephenol and controlling the molar ratio, a phosphorus-containing monomer containing two acetylene phenyl groups is generated. The phosphorus-containing monomer is then reacted with tartaric acid to generate a phosphorus-containing dicarboxylic acid. The phosphorus-containing dicarboxylic acid and neopentyl glycol are then transesterified to generate a polyester-type phosphorus-containing diol, which participates in the polymerization of polyurethane. The phosphorus-containing diol is covalently embedded in the polyurethane backbone. When heated, the phosphorus element preferentially decomposes to generate a glassy phosphate layer, which isolates the heat source and cuts off the combustion free radical chain, thus achieving long-lasting intrinsic flame retardancy.

[0094] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a waterborne polyurethane coating, characterized in that, The preparation steps include the following: (1) A modified polyurethane dispersion with propargyl alcohol end capping was prepared using a phosphorus-containing diol; the preparation method of the phosphorus-containing diol was as follows: tartaric acid was reacted with a phosphorus-containing monomer to obtain a phosphorus-containing dicarboxylic acid, which was then polymerized with a diol to obtain a phosphorus-containing diol; the phosphorus-containing monomer was obtained by reacting 4-acetylenol with phosphorus oxychloride. (2) 3-amino-1,2,4-triazole, p-nitrobenzaldehyde, and 1,3-cyclohexanedione were reacted to obtain a functional monomer precursor; the functional monomer precursor was reduced to obtain the functional monomer. (3) Pretreated silica and functional monomers are reacted to obtain pre-modified silica; pre-modified silica and γ-selenobutyrolactone are reacted to obtain modified silica; the preparation method of the functional monomer is: 3-amino-1,2,4-triazole, p-nitrobenzaldehyde and 1,3-cyclohexanedione are reacted to obtain a precursor, and then reduced to obtain the functional monomer; the preparation method of the pretreated silica is: silica encapsulated in chitosan is oxidized with sodium periodate. (4) The modified polyurethane dispersion is mixed with modified silica to obtain a waterborne polyurethane coating.

2. A waterborne polyurethane coating prepared by the method according to claim 1.