High-temperature-resistant self-repairing coating and preparation method thereof

Abstract

The invention discloses a high-temperature-resistant self-repairing coating and a preparation method thereof, and relates to the technical field of coatings. The high-temperature-resistant self-repairing coating prepared by the invention comprises modified polyurethane, modified carbon nanotubes, a defoaming agent, an auxiliary agent, a curing agent, a solvent and a flatting agent, and the modified polyurethane is obtained by reacting piperazinyl-terminated polysiloxane with isocyanate and then grafting alkenyl iodo-boron dipyrromethene; the modified carbon nano tube is obtained by grafting an acylating chlorination carbon nano tube with 2-tert-butyl-4-aminophenol, then reacting with DL-3, 4-dihydroxy mandelic acid, and finally reacting with 1, 4-phenylboronic acid. The high-temperature-resistant self-repairing coating prepared by the invention has good antibacterial, anti-aging and self-repairing properties.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and in particular to a high temperature resistant self-repairing coating and a preparation method thereof. Background Art

[0002] As a multifunctional material, coatings are widely used to protect and decorate various surfaces, including metal, wood, plastic, etc. It not only enhances the aesthetics of the coated object, but also provides important protective functions, such as preventing corrosion, wear and environmental erosion. With the development of technology, the application scenarios of coatings are constantly expanding, covering many fields such as construction, transportation, electronics, aerospace, and daily necessities. Especially in some extreme environments, such as high temperature, high pressure or highly corrosive environments, the requirements for coatings are more stringent.

[0003] In many application environments, coatings will crack or peel off when exposed to high temperatures for a long time, which will seriously affect their protective effect. Therefore, developing a coating that can withstand high temperature conditions and has self-healing properties has become an important research direction. In addition to high temperature resistance, modern coatings also need to have antibacterial and antioxidant capabilities to meet the growing health and environmental protection requirements. The antibacterial function helps inhibit the growth of microorganisms and reduce the risk of biological contamination; while the addition of antioxidant function can extend the service life of the material and reduce maintenance costs. Summary of the invention

[0004] The purpose of the present invention is to provide a high temperature resistant self-repairing coating and a preparation method thereof, so as to solve the problems existing in the prior art.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A method for preparing a high temperature resistant self-repairing coating comprises the following preparation steps:

[0007] (1) reacting piperazine and chloromethyldimethylethoxysilane to obtain piperazine silane; hydrolyzing piperazine silane to obtain piperazine double-end capping; reacting D4, tetramethylcyclotetrasiloxane, and piperazine double-end capping to obtain terminal piperazine polysiloxane;

[0008] (2) reacting 4-(4-pyridyl)benzaldehyde and 4-bromo-1-butene to obtain pyridinium quaternary ammonium salt; reacting pyridinium quaternary ammonium salt, 2,4-dimethyl-1H-pyrrole, and boron trifluoride ether to obtain alkenyl fluoroboron dipyrrole; reacting alkenyl fluoroboron dipyrrole and N-iodosuccinimide to obtain alkenyl iodofluoroboron dipyrrole;

[0009] (3) reacting terminal piperazine polysiloxane, 4,4'-dicyclohexylmethane diisocyanate, melamine, and caprolactam to obtain a pre-modified polyurethane;

[0010] (4) reacting the pre-modified polyurethane and vinyl iodinated fluoroborane dipyrrole to obtain a modified polyurethane;

[0011] (5) reacting acyl chloride carbon nanotubes and 2-tert-butyl-4-aminophenol to obtain pretreated carbon nanotubes;

[0012] (6) reacting the pretreated carbon nanotubes and DL-3,4-dihydroxymandelic acid to obtain pre-modified carbon nanotubes; reacting the pre-modified carbon nanotubes and 1,4-phenylenediboric acid to obtain modified carbon nanotubes;

[0013] (7) The following raw materials: modified polyurethane, modified carbon nanotubes, defoaming agent, additive, curing agent, solvent, and leveling agent are mixed to obtain a high temperature resistant self-healing coating.

[0014] As an optimization, the preparation method of the terminal piperazine polysiloxane in step (1) is as follows: piperazine and dioxane are weighed in a mass ratio of 1: (20-30), piperazine is dissolved in dioxane at 90° C. under nitrogen protection, the temperature is lowered to 80° C., chloromethyldimethylethoxysilane is added in an equal molar ratio to piperazine, the reaction is carried out for 2-3 hours, and piperazine silane is obtained by filtering and distilling under reduced pressure; piperazine silane, ethanol and pure water are mixed in a mass ratio of 1: (10-20): (10-20), the pH value is adjusted to 4 with hydrochloric acid, the reaction is carried out at 50° C. for 5 hours, and the mixture is distilled under reduced pressure. distill to obtain a piperazine double head; under nitrogen protection, mix D4, tetramethylcyclotetrasiloxane and tetramethylammonium hydroxide in a mass ratio of 1: (0.8-1.0): (0.01-0.02), heat to 90-100° C. and react for 5-6 hours, add a piperazine double head in an amount of 0.2-0.3 times the mass of D4, continue stirring for 2-3 hours, heat to 150° C. and react for 50-60 minutes, and distill under reduced pressure at 100° C. to obtain a terminal piperazine polysiloxane; the terminal piperazine polysiloxane has a molecular weight of 2000; and D4 is octamethylcyclotetrasiloxane.

[0015] As an optimization, the preparation method of the vinyl iodide fluoroboron dipyrrole described in step (2) is as follows: at 60 - 70 °C, mix 4-(4-pyridyl)benzaldehyde, 4-bromo-1-butene, and acetonitrile in a mass ratio of 1:(0.75 - 0.8):(20 - 30), stir for 12 - 14 h, and obtain the pyridinium quaternary salt through rotary evaporation under reduced pressure, washing, and drying; under argon protection, mix the pyridinium quaternary salt, 2,4-dimethyl-1H-pyrrole, trifluoroacetic acid, and dichloromethane, stir in the dark for 10 - 12 h, add 2,3-dichloro-5,6-dicyano-p-benzoquinone, continue to stir in the dark for 1 - 2 h, and finally add triethylamine and boron trifluoride diethyl ether complex, stir in the dark for 10 - 12 h, and obtain vinyl fluoroboron dipyrrole through rotary evaporation under reduced pressure, washing, and drying; the molar ratio of the pyridinium quaternary salt, 2,4-dimethyl-1H-pyrrole, 2,3-dichloro-5,6-dicyano-p-benzoquinone, and triethylamine is 1:(2.1 - 2.3):(1 - 1.2):(10 - 10.5); the volume ratio of 2,4-dimethyl-1H-pyrrole, dichloromethane, trifluoroacetic acid, and boron trifluoride diethyl ether complex is 1:(130 - 140):(1.7 - 1.9):(1 - 2); mix the vinyl fluoroboron dipyrrole and N-iodosuccinimide in a molar ratio of 1:(4.1 - 4.3) and dissolve them in dichloromethane with a mass 120 - 140 times that of the vinyl fluoroboron dipyrrole, stir at room temperature for 4 - 5 h, and obtain vinyl iodide fluoroboron dipyrrole through rotary evaporation under reduced pressure.

[0016] As an optimization, the preparation method of the pre-modified polyurethane described in step (3) is as follows: mix the terminal piperazinyl polysiloxane and N,N-dimethylformamide, after heating to 50 °C, add 4,4'-dicyclohexylmethane diisocyanate, dibutyltin dilaurate, and melamine, heat to 80 - 90 °C, continue to react for 4 - 5 h, add caprolactam, and continue to react at 70 °C for 3 h to obtain the pre-modified polyurethane; the mass ratio of the terminal piperazinyl polysiloxane, 4,4'-dicyclohexylmethane diisocyanate, melamine, dibutyltin dilaurate, N,N-dimethylformamide, and caprolactam is 1:(0.2 - 0.25):(0.02 - 0.03):(0.005 - 0.006):(5 - 6):(0.02 - 0.03).

[0017] As an optimization, the preparation method of the modified polyurethane described in step (4) is as follows: mix the pre-modified polyurethane, vinyl iodide fluoroboron dipyrrole, Karstedt's catalyst, and N,N-dimethylformamide in a mass ratio of 1:(0.2 - 0.3):(0.001 - 0.002):(20 - 30), heat to 85 °C, react for 4 - 5 h, and obtain the modified polyurethane through rotary evaporation under reduced pressure; Karstedt's catalyst is bis(1,3-divinyl-1,1,3,3-tetramethyldisiloxane)platinum.

[0018] As an optimization, the preparation method of the pretreated carbon nanotubes in step (5) is: carboxylated carbon nanotubes, thionyl chloride, and N,N-dimethylformamide are mixed in a mass ratio of 1:(150-170):(5-6), heated to 70°C and stirred for 20-24 hours, filtered, washed, and dried to obtain chlorinated carbon nanotubes; chlorinated carbon nanotubes, 2-tert-butyl-4-aminophenol, triethylamine, and trifluoroacetic acid are mixed in a mass ratio of 1:(0.3-0.4):(1.1-1.2):(5-6) for 1-2 hours, filtered, washed, and dried to obtain pretreated carbon nanotubes.

[0019] As an optimization, the preparation method of the modified carbon nanotubes in step (6) is as follows: pretreated carbon nanotubes, DL-3,4-dihydroxymandelic acid, and trifluoroacetic acid are mixed in a mass ratio of 1:(0.5-0.7):(3-4), heated to 95-100°C under nitrogen protection, and methanesulfonic acid with a mass of 0.01 times that of trifluoroacetic acid is added to react for 10-12 hours, and the pre-modified carbon nanotubes are obtained by filtering, washing, and drying; pre-modified carbon nanotubes, 1,4-phenylenediboric acid, and ethanol are mixed in a mass ratio of 1:(0.2-0.3):(30-40), heated to 40-50°C to react for 8-10 hours, and the modified carbon nanotubes are obtained by filtering, washing, and drying.

[0020] As an optimization, the amounts of the raw materials in step (7) are as follows: by mass, 100 parts of modified polyurethane, 3-5 parts of modified carbon nanotubes, 1-2 parts of defoaming agent, 3-5 parts of auxiliary agent, 15-20 parts of curing agent, 30-40 parts of solvent, and 1-2 parts of leveling agent; the defoaming agent model is BYK1758; the auxiliary agent is a mixture of tetrakistriphenylphosphine palladium and sodium carbonate in a mass ratio of 1:10; the curing agent model is XCT-802; the solvent is xylene; and the leveling agent model is BYK-333.

[0021] As an optimization, the carboxylated carbon nanotube model is CNT300.

[0022] The present invention also provides a high temperature resistant self-repairing coating prepared according to the preparation method of the high temperature resistant self-repairing coating.

[0023] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0024] When preparing the high-temperature resistant self-healing coating of the present invention, first, piperazine bis(trimethylsilyl) and cyclic siloxane are subjected to ring-opening polymerization to obtain piperazinyl-terminated polysiloxane. The piperazinyl-terminated polysiloxane and isocyanate are prepared into pre-modified polyurethane and then grafted with vinyl iodide fluoroboron dipyrrole to obtain modified polyurethane. Second, the carbon nanotubes acyl chloride and 2-tert-butyl-4-aminophenol are reacted, and then reacted with DL-3,4-dihydroxymandelic acid to obtain pre-modified carbon nanotubes; then reacted with 1,4-benzenediboronic acid to obtain modified carbon nanotubes. Finally, the modified polyurethane and the modified carbon nanotubes are mixed to obtain the high-temperature resistant self-healing coating.

[0025] First, piperazine bis(trimethylsilyl), octamethylcyclotetrasiloxane, and tetramethylcyclotetrasiloxane are subjected to ring-opening polymerization to obtain piperazinyl-terminated polysiloxane containing silicon-hydrogen bonds; the piperazinyl-terminated polysiloxane and isocyanate are prepared into polyurethane containing silicon-hydrogen bonds; polysiloxane takes the silicon-oxygen bond as the backbone. Due to the high dissociation energy and strong polarity of the silicon-oxygen bond, it has excellent thermal stability and can endow the material with good high-temperature resistance. In the present invention, a polyurethane molecular chain containing dynamic hindered urea bonds is constructed through the reaction of piperazine and isocyanate. The introduction of the steric group will reduce the dissociation energy of the carbon-nitrogen bond, thereby reducing the activation energy of the urea bond reaction and making the reaction rate constant faster under mild conditions. Under external force, the dynamic exchange property of the urea bond of the polymer endows the material with self-healing performance;

[0026] 4-(4-Pyridyl)benzaldehyde and 4-bromo-1-butene are reacted to generate a pyridyl quaternary ammonium salt containing an aldehyde group. Under the acidic condition of trifluoroacetic acid, the aldehyde group undergoes a condensation reaction with 2,4-dimethyl-1H-pyrrole, and one hydrogen on one of the pyrrole nitrogens is removed by the oxidizing property of 2,3-dichloro-5,6-dicyano-p-benzoquinone. Finally, under the basic condition of triethylamine, boron trifluoride undergoes a complexation reaction with dipyrrole to obtain vinyl fluoroboron dipyrrole, and then reacted with N-iodosuccinimide to obtain iodine-containing vinyl iodide fluoroboron dipyrrole;

[0027] The polyurethane containing silicon-hydrogen bonds can be grafted with vinyl iodide fluoroboron dipyrrole through hydrosilylation; the pyridyl quaternary ammonium salt carried on the vinyl iodide fluoroboron dipyrrole can endow the material with good antibacterial properties, and the fluoroboron dipyrrole containing iodine atoms is a class of photosensitive antibacterial agents, which can react with surrounding oxygen under light to generate reactive oxygen species, thereby eradicating bacteria. The introduction of vinyl iodide fluoroboron dipyrrole can endow the material with good antibacterial properties through dual effects;

[0028] Secondly, acyl chloride-functionalized carbon nanotubes are reacted with 2-tert-butyl-4-aminophenol, and then esterification and Friedel-Crafts alkylation reactions are carried out with DL-3,4-dihydroxymandelic acid to generate an arylbenzofuranone structure, which endows the material with good antioxidant properties by capturing carbon free radicals generated during the degradation of the polymer; 1,4-benzenediboronic acid and the two hydroxyl groups on DL-3,4-dihydroxymandelic acid form a dynamic borate ester structure and introduce a boronic acid functional group;

[0029] Finally, a coating is obtained by mixing a modified polyurethane emulsion, modified carbon nanotubes, an antifoaming agent, an auxiliary agent, and a curing agent; the boronic acid structure on the modified carbon nanotubes and the iodine on the modified polyurethane will undergo a Suzuki coupling reaction, thereby increasing the crosslinking sites between the modified polyurethane and the modified carbon nanotubes and enhancing the mechanical properties. Specific Embodiments

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0031] In the following examples and comparative examples, the carboxylated carbon nanotubes are of the CNT300 type, purchased from Zhongke Leiming Technology Co., Ltd.; the D4 is octamethylcyclotetrasiloxane; the Karstedt catalyst is bis(1,3-divinyl-1,1,3,3-tetramethyldisiloxane) platinum; the molecular weight of the terminal piperazinyl polysiloxane is 2000; the antifoaming agent is of the BYK1758 type; the auxiliary agent is obtained by mixing tetrakis(triphenylphosphine)palladium and sodium carbonate in a mass ratio of 1:10; the curing agent is of the XCT-802 type; the solvent is isomer-grade xylene, purchased from Jinan Xinjinshuo New Materials Co., Ltd.; the leveling agent is of the BYK-333 type; the hydrochloric acid is a 40 wt% hydrochloric acid solution.

[0032] Example 1:

[0033] A preparation method of a high-temperature resistant self-healing coating, the preparation method of the high-temperature resistant self-healing coating comprising the following preparation steps:

[0034] (1) Weigh piperazine and dioxane in a mass ratio of 1:20, dissolve piperazine in dioxane at 90° C. under nitrogen protection, cool to 80° C., add chloromethyldimethylethoxysilane in an equal molar ratio to piperazine, react for 3 h, filter and distill under reduced pressure to obtain piperazine silane; mix piperazine silane, ethanol and pure water in a mass ratio of 1:10:10, adjust the pH to 4 with hydrochloric acid, react at 50° C. for 5 h, and obtain piperazine double-end by rotary distillation under reduced pressure; under nitrogen protection, mix D4, tetramethylcyclotetrasiloxane and tetramethylammonium hydroxide in a mass ratio of 1:0.8:0.01, heat to 100° C. and react for 6 h, add 0.2 times the mass of D4 piperazine double-end and continue stirring for 3 h, heat to 150° C. and react for 60 min, and distill under reduced pressure at 100° C. to obtain terminal piperazine polysiloxane;

[0035] (2) At 70° C., 4-(4-pyridyl)benzaldehyde, 4-bromo-1-butene, and acetonitrile were mixed and stirred at a mass ratio of 1:0.75:20 for 14 hours, and then vacuum rotary evaporation, washing, and drying were performed to obtain pyridinium quaternary ammonium salt; under argon protection, pyridinium quaternary ammonium salt, 2,4-dimethyl-1H-pyrrole, trifluoroacetic acid, and dichloromethane were mixed, stirred in the dark for 12 hours, 2,3-dichloro-5,6-dicyano-p-benzoquinone was added, and stirring in the dark for 2 hours was continued, and finally triethylamine and boron trifluoride ether were added, stirred in the dark for 12 hours, and then vacuum rotary evaporation, washing, and drying were performed to obtain vinyl Fluoroboron dipyrrole; the molar ratio of pyridine quaternary ammonium salt, 2,4-dimethyl-1H-pyrrole, 2,3-dichloro-5,6-dicyano-p-benzoquinone, and triethylamine is 1:2.1:1:10; the volume ratio of 2,4-dimethyl-1H-pyrrole, dichloromethane, trifluoroacetic acid, and boron trifluoride ether is 1:130:1.7:1; vinylboron dipyrrole and N-iodosuccinimide are mixed in a molar ratio of 1:4.1 and dissolved in dichloromethane (120 times the mass of vinylboron dipyrrole), stirred at room temperature for 4 hours, and subjected to reduced pressure rotary evaporation to obtain vinyliodoboron dipyrrole;

[0036] (3) Mix the piperazine-terminated polysiloxane and N,N-dimethylformamide, heat to 50°C, add 4,4'-dicyclohexylmethane diisocyanate, dibutyltin dilaurate, and melamine, heat to 90°C, continue to react for 5 hours, add caprolactam, and continue to react at 70°C for 3 hours to obtain a pre-modified polyurethane; the mass ratio of piperazine-terminated polysiloxane, 4,4'-dicyclohexylmethane diisocyanate, melamine, dibutyltin dilaurate, N,N-dimethylformamide, and caprolactam is 1:0.2:0.02:0.005:5:0.02;

[0037] (4) Pre-modified polyurethane, vinyl iodide fluoroborane dipyrrole, Custer catalyst, and N,N-dimethylformamide were mixed in a mass ratio of 1:0.2:0.001:20, heated to 85° C., reacted for 5 h, and subjected to reduced pressure rotary evaporation to obtain modified polyurethane;

[0038] (5) Carboxylated carbon nanotubes, thionyl chloride, and N,N-dimethylformamide were mixed in a mass ratio of 1:150:5, heated to 70°C and stirred for 24 hours, filtered, washed, and dried to obtain chlorinated carbon nanotubes; chlorinated carbon nanotubes, 2-tert-butyl-4-aminophenol, triethylamine, and trifluoroacetic acid were mixed in a mass ratio of 1:0.3:1.1:5 for 2 hours, filtered, washed, and dried to obtain pretreated carbon nanotubes;

[0039] (6) Pretreated carbon nanotubes, DL-3,4-dihydroxymandelic acid, and trifluoroacetic acid were mixed in a mass ratio of 1:0.5:3, heated to 100°C under nitrogen protection, and methanesulfonic acid (0.01 times the mass of trifluoroacetic acid) was added to react for 12 hours, and the pre-modified carbon nanotubes were obtained by filtering, washing, and drying; pre-modified carbon nanotubes, 1,4-phenylenediboric acid, and ethanol were mixed in a mass ratio of 1:0.2:30, heated to 50°C, reacted for 10 hours, and filtered, washed, and dried to obtain modified carbon nanotubes;

[0040] (7) Weigh the following raw materials, calculated by mass: 100 parts of modified polyurethane, 3 parts of modified carbon nanotubes, 1 part of defoaming agent, 3 parts of auxiliary agent, 15 parts of curing agent, 30 parts of solvent, and 1 part of leveling agent, and mix the above raw materials to obtain a high temperature resistant self-healing coating.

[0041] Embodiment 2:

[0042] A method for preparing a high temperature resistant self-repairing coating, the method for preparing the high temperature resistant self-repairing coating comprising the following preparation steps:

[0043] (1) Weigh piperazine and dioxane in a mass ratio of 1:25, dissolve piperazine in dioxane at 90° C. under nitrogen protection, cool to 80° C., add chloromethyldimethylethoxysilane in an equal molar ratio to piperazine, react for 2.5 hours, filter and distill under reduced pressure to obtain piperazine silane; mix piperazine silane, ethanol and pure water in a mass ratio of 1:15:17, adjust the pH to 4 with hydrochloric acid, react at 50° C. for 5 hours, and obtain piperazine double-end by rotary distillation under reduced pressure; under nitrogen protection, mix D4, tetramethylcyclotetrasiloxane and tetramethylammonium hydroxide in a mass ratio of 1:0.9:0.01, heat to 95° C. for reaction for 5.5 hours, add piperazine double-end in an amount 0.25 times the mass of D4, continue stirring for 2.5 hours, heat to 150° C. for reaction for 55 minutes, and distill under reduced pressure at 100° C. to obtain terminal piperazine polysiloxane;

[0044] (2) At 65 °C, 4-(4-pyridyl)benzaldehyde, 4-bromo-1-butene, and acetonitrile were mixed and stirred at a mass ratio of 1:0.77:25 for 13 h. After rotary evaporation under reduced pressure and washing and drying, a pyridinium quaternary salt was obtained. Under argon protection, the pyridinium quaternary salt, 2,4-dimethyl-1H-pyrrole, trifluoroacetic acid, and dichloromethane were mixed and stirred in the dark for 11 h. 2,3-Dichloro-5,6-dicyano-p-benzoquinone was added, and stirring in the dark was continued for 1.5 h. Finally, triethylamine and boron trifluoride diethyl ether were added, and stirring in the dark was continued for 11 h. After rotary evaporation under reduced pressure and washing and drying, vinyl fluoroboron dipyrrole was obtained. The molar ratio of the pyridinium quaternary salt, 2,4-dimethyl-1H-pyrrole, 2,3-dichloro-5,6-dicyano-p-benzoquinone, and triethylamine was 1:2.2:1.1:10.3; the volume ratio of 2,4-dimethyl-1H-pyrrole, dichloromethane, trifluoroacetic acid, and boron trifluoride diethyl ether was 1:135:1.8:1.5; the vinyl fluoroboron dipyrrole and N-iodosuccinimide were mixed at a molar ratio of 1:4.2 and dissolved in dichloromethane 130 times the mass of the vinyl fluoroboron dipyrrole, and stirred at room temperature for 4.5 h. After rotary evaporation under reduced pressure, vinyl iodide fluoroboron dipyrrole was obtained.

[0045] (3) The terminal piperazinyl polysiloxane and N,N-dimethylformamide were mixed. After heating to 50 °C, 4,4'-dicyclohexylmethane diisocyanate, dibutyltin dilaurate, and melamine were added. The temperature was raised to 85 °C, and the reaction was continued for 4.5 h. Caprolactam was added, and the reaction was continued at 70 °C for 3 h to obtain a pre-modified polyurethane. The mass ratio of the terminal piperazinyl polysiloxane, 4,4'-dicyclohexylmethane diisocyanate, melamine, dibutyltin dilaurate, N,N-dimethylformamide, and caprolactam was 1:0.23:0.02:0.005:5.5:0.02;

[0046] (4) The pre-modified polyurethane, vinyl iodide fluoroboron dipyrrole, Cast catalyst, and N,N-dimethylformamide were mixed at a mass ratio of 1:0.25:0.001:25. The temperature was raised to 85 °C, and the reaction was carried out for 4.5 h. After rotary evaporation under reduced pressure, a modified polyurethane was obtained. The modified polyurethane and acetone were mixed at a mass ratio of 1:0.25 at 35 °C, pure water was added, and emulsification was carried out using a disperser at a disperser speed of 2500 r / min. Then the temperature was raised to 52 °C and kept warm for 3 h to obtain a modified polyurethane emulsion; the solid content of the modified polyurethane emulsion was 45%;

[0047] (5) The carboxylated carbon nanotubes, thionyl chloride, and N,N-dimethylformamide were mixed at a mass ratio of 1:160:5.5. The temperature was raised to 70 °C and stirred for 22 h. After filtration, washing, and drying, acyl chloride carbon nanotubes were obtained. The acyl chloride carbon nanotubes, 2-tert-butyl-4-aminophenol, triethylamine, and trifluoroacetic acid were mixed at a mass ratio of 1:0.35:1.1:5.5 for 1.2 h. After filtration and washing and drying, pretreated carbon nanotubes were obtained.

[0048] (6) Pretreated carbon nanotubes, DL-3,4-dihydroxymandelic acid, and trifluoroacetic acid were mixed in a mass ratio of 1:0.6:3.5, heated to 97°C under nitrogen protection, and methanesulfonic acid (0.01 times the mass of trifluoroacetic acid) was added to react for 11 hours, and the pre-modified carbon nanotubes were obtained by filtering, washing, and drying; pre-modified carbon nanotubes, 1,4-phenylenediboric acid, and ethanol were mixed in a mass ratio of 1:0.25:35, heated to 45°C, reacted for 9 hours, and filtered, washed, and dried to obtain modified carbon nanotubes;

[0049] (7) Weigh the following raw materials, calculated by mass: 100 parts of modified polyurethane, 4 parts of modified carbon nanotubes, 1.5 parts of defoaming agent, 4 parts of auxiliary agent, 17 parts of curing agent, 35 parts of solvent, and 1.5 parts of leveling agent, and mix the above raw materials to obtain a high-temperature resistant self-healing coating.

[0050] Embodiment 3:

[0051] A method for preparing a high temperature resistant self-repairing coating, the method for preparing the high temperature resistant self-repairing coating comprising the following preparation steps:

[0052] (1) Weigh piperazine and dioxane in a mass ratio of 1:30, dissolve piperazine in dioxane at 90° C. under nitrogen protection, cool to 80° C., add chloromethyldimethylethoxysilane in an equal molar ratio to piperazine, react for 2 h, filter and distill under reduced pressure to obtain piperazine silane; mix piperazine silane, ethanol and pure water in a mass ratio of 1:20:20, adjust the pH to 4 with hydrochloric acid, react at 50° C. for 5 h, and obtain piperazine double-end by rotary distillation under reduced pressure; under nitrogen protection, mix D4, tetramethylcyclotetrasiloxane and tetramethylammonium hydroxide in a mass ratio of 1:1.0:0.02, heat to 90° C. for reaction for 5 h, add 0.3 times the mass of D4 piperazine double-end and continue stirring for 3 h, heat to 150° C. for reaction for 50 min, and distill under reduced pressure at 100° C. to obtain terminal piperazine polysiloxane;

[0053] (2) At 60 °C, 4-(4-pyridyl)benzaldehyde, 4-bromo-1-butene, and acetonitrile were mixed and stirred for 12 h in a mass ratio of 1:0.8:30. After rotary evaporation under reduced pressure and washing and drying, a pyridinium quaternary salt was obtained. Under argon protection, the pyridinium quaternary salt, 2,4-dimethyl-1H-pyrrole, trifluoroacetic acid, and dichloromethane were mixed and stirred in the dark for 10 h. 2,3-Dichloro-5,6-dicyano-p-benzoquinone was added, and stirring was continued in the dark for 1 h. Finally, triethylamine and boron trifluoride diethyl ether were added, and stirring was continued in the dark for 10 h. After rotary evaporation under reduced pressure and washing and drying, vinyl fluoroboron dipyrrole was obtained. The molar ratio of the pyridinium quaternary salt, 2,4-dimethyl-1H-pyrrole, 2,3-dichloro-5,6-dicyano-p-benzoquinone, and triethylamine was 1:2.3:1.2:10.5; the volume ratio of 2,4-dimethyl-1H-pyrrole, dichloromethane, trifluoroacetic acid, and boron trifluoride diethyl ether was 1:140:1.9:2; the vinyl fluoroboron dipyrrole and N-iodosuccinimide were mixed in a molar ratio of 1:4.3 and dissolved in dichloromethane 140 times the mass of the vinyl fluoroboron dipyrrole, and stirred at room temperature for 4 h. After rotary evaporation under reduced pressure, vinyl iodofluoro boron dipyrrole was obtained.

[0054] (3) The terminal piperazinyl polysiloxane and N,N-dimethylformamide were mixed. After heating to 50 °C, 4,4'-dicyclohexylmethane diisocyanate, dibutyltin dilaurate, and melamine were added. The temperature was raised to 90 °C, and the reaction was continued for 5 h. Caprolactam was added, and the reaction was continued at 70 °C for 3 h to obtain a pre-modified polyurethane. The mass ratio of the terminal piperazinyl polysiloxane, 4,4'-dicyclohexylmethane diisocyanate, melamine, dibutyltin dilaurate, N,N-dimethylformamide, and caprolactam was 1:0.25:0.03:0.006:6:0.03;

[0055] (4) The pre-modified polyurethane, vinyl iodofluoro boron dipyrrole, Cast catalyst, and N,N-dimethylformamide were mixed in a mass ratio of 1:0.3:0.002:30. The temperature was raised to 85 °C, and the reaction was carried out for 4 h. After rotary evaporation under reduced pressure, a modified polyurethane was obtained.

[0056] (5) The carboxylated carbon nanotubes, thionyl chloride, and N,N-dimethylformamide were mixed in a mass ratio of 1:170:6. The temperature was raised to 70 °C and stirred for 20 h. After filtration, washing, and drying, acyl chloride-functionalized carbon nanotubes were obtained. The acyl chloride-functionalized carbon nanotubes, 2-tert-butyl-4-aminophenol, triethylamine, and trifluoroacetic acid were mixed in a mass ratio of 1:0.4:1.2:6 for 1 h. After filtration, washing, and drying, pretreated carbon nanotubes were obtained.

[0057] (6) Mix the pretreated carbon nanotubes, DL-3,4-dihydroxymandelic acid, and trifluoroacetic acid in a mass ratio of 1:0.7:4. Under nitrogen protection, heat the mixture to 95 °C, add methanesulfonic acid in an amount 0.01 times the mass of trifluoroacetic acid, and react for 10 h. After filtration, washing, and drying, obtain the pre-modified carbon nanotubes. Mix the pre-modified carbon nanotubes, 1,4-benzenediboronic acid, and ethanol in a mass ratio of 1:0.3:40, heat the mixture to 40 °C, and react for 8 h. After filtration, washing, and drying, obtain the modified carbon nanotubes;

[0058] (7) Weigh the following raw materials. By mass fraction, 100 parts of modified polyurethane, 5 parts of modified carbon nanotubes, 2 parts of defoamer, 5 parts of auxiliary agent, 20 parts of curing agent, 40 parts of solvent, and 2 parts of leveling agent. Mix the above raw materials to obtain the high-temperature self-healing coating.

[0059] Comparative Example 1:

[0060] The preparation method of the high-temperature self-healing coating in Comparative Example 1 is different from that in Example 2 in that it does not contain vinyl iodide fluoroboron dipyrrole. Specifically, it does not contain step (2), and step (7) is modified as follows: Weigh the following raw materials. By mass fraction, 100 parts of pre-modified polyurethane, 4 parts of modified carbon nanotubes, 1.5 parts of defoamer, 4 parts of auxiliary agent, 17 parts of curing agent, 35 parts of solvent, and 1.5 parts of leveling agent. Mix the above raw materials to obtain the high-temperature self-healing coating. The remaining steps are the same as those in Example 2.

[0061] Comparative Example 2:

[0062] The preparation method of the high-temperature self-healing coating in Comparative Example 2 is different from that in Example 2 in that it does not modify the carboxylated carbon nanotubes. Specifically, it does not contain steps (5) - (6), and step (7) is modified as follows: Weigh the following raw materials. By mass fraction, 100 parts of modified polyurethane, 4 parts of carboxylated carbon nanotubes, 1.5 parts of defoamer, 17 parts of curing agent, 35 parts of solvent, and 1.5 parts of leveling agent. Mix the above raw materials to obtain the high-temperature self-healing coating. The remaining steps are the same as those in Example 2.

[0063] Comparative Example 3:

[0064] The preparation method of the high-temperature self-healing coating in Comparative Example 3 is different from that in Example 2 in that it does not introduce a benzeneboronic acid structure onto the carbon nanotubes. Specifically, step (6) is modified as follows: Mix the pretreated carbon nanotubes, DL-3,4-dihydroxymandelic acid, and trifluoroacetic acid in a mass ratio of 1:0.6:3.5. Under nitrogen protection, heat the mixture to 97 °C, add methanesulfonic acid in an amount 0.01 times the mass of trifluoroacetic acid, and react for 11 h. After filtration, washing, and drying, obtain the modified carbon nanotubes;

[0065] Modify step (7) as follows: Weigh the following raw materials by mass parts: 100 parts of modified polyurethane, 4 parts of modified carbon nanotubes, 1.5 parts of defoamer, 17 parts of curing agent, 35 parts of solvent, and 1.5 parts of leveling agent. Mix the above raw materials to obtain a high-temperature self-healing coating. The remaining steps are the same as in Example 2.

[0066] Test Example 1:

[0067] Pour the coatings prepared in the examples and comparative examples into a polytetrafluoroethylene mold and place it in a forced-air drying oven at 100 °C. After curing and demolding, obtain samples. According to the standard QB / T 2591-2003, then under the irradiation of a green LED lamp (18 mW / cm -2 ) conduct an antibacterial rate test on the samples, and the results are shown in Table 1.

[0068] Table 1

[0069] Antibacterial rate (%) Antibacterial rate (%) Example 1 98.57 Comparative Example 1 26.47 Example 2 98.66 Comparative Example 2 97.57 Example 3 98.99 Comparative Example 3 97.63

[0070] From the comparison of the experimental data of Examples 1-3 and Comparative Examples 1-3 in Table 1, it can be found that the coatings prepared by the present invention have good antibacterial properties.

[0071] In Comparative Example 1, the polyurethane was not antibacterial modified. The antibacterial properties of Examples 1-3 are better than those of Comparative Example 1, indicating that the polyurethane containing a silicon-hydrogen bond can be grafted with vinyl iodide fluoroboron dipyrrole through hydrosilylation; and the pyridinium quaternary salt carried on the vinyl iodide fluoroboron dipyrrole can endow the material with good antibacterial properties, and the fluoroboron dipyrrole containing an iodine atom is a class of photosensitive antibacterial agents that can react with surrounding oxygen under light irradiation to generate reactive oxygen species, thereby eradicating bacteria. The introduction of vinyl iodide fluoroboron dipyrrole can endow the material with good antibacterial properties through dual effects.

[0072] Test Example 2:

[0073] Test of mechanical properties:

[0074] Test method: Pour the coatings prepared in the examples and comparative examples into a polytetrafluoroethylene mold and place it in a forced-air drying oven at 100 °C. After curing and demolding, cut the samples into 30 mm × 5 mm, with a thickness of 0.3 mm; use a mechanical tensile testing machine to conduct a tensile test on the specimens at room temperature, and the tensile rate is 10 mm / min. The results are shown in Table 2.

[0075] Test of anti-aging performance:

[0076] Test method: Place the samples in a thermal oxygen aging oven for aging, with an aging time of 480 h, an aging temperature of 60 °C, and a relative humidity of 55%. Test the aged samples according to the test method of mechanical properties. And calculate the retention rate of tensile strength before and after aging; the results are shown in Table 2.

[0077] Test of self-healing performance:

[0078] Test method: Cut the sample in half, closely fit the fracture surface, press it with fingers for 1 min, then put it into an oven at 80 °C for 12 h for repair, and conduct tests according to the test method of mechanical properties, and calculate the self-healing efficiency. The results are shown in Table 2.

[0079] Table 2

[0080] Tensile strength (MPa) Tensile strength retention rate (%) Self-healing efficiency (%) Example 1 12.86 86.73 95.64 Example 2 12.91 87.02 96.21 Example 3 12.95 87.14 96.34 Comparative Example 1 8.43 85.33 95.61 Comparative Example 2 8.22 52.31 88.34 Comparative Example 3 9.28 86.36 88.27

[0081] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 3 in Table 1, it can be found that the coatings prepared by the present invention have good mechanical properties, anti-aging properties, and self-healing properties.

[0082] In Comparative Example 1, the vinyl iodide fluoroboron dipyrrole structure was not grafted. In Comparative Example 2, the carboxylated carbon nanotubes were not modified. In Comparative Example 3, the phenylboronic acid structure was not introduced. The mechanical properties of Examples 1 to 3 are better than those of Comparative Example 3, and the anti-aging properties of Examples 1 to 3 are better than those of Comparative Example 2; it shows that the boric acid structure on the modified carbon nanotubes and iodine on the modified polyurethane will undergo Suzuki coupling reaction, thereby increasing the cross-linking sites between the modified polyurethane and the modified carbon nanotubes, thereby enhancing the mechanical properties; reacting acyl chloride carbon nanotubes with 2-tert-butyl-4-aminophenol, and then carrying out esterification reaction and Friedel-Crafts alkylation reaction with DL-3,4-dihydroxy mandelic acid to generate an aryl benzofuranone structure, which endows the material with good antioxidant performance by capturing the carbon free radicals generated during the degradation of the polymer;

[0083] Both the examples and the comparative examples have relatively high self-healing efficiency, indicating that the material has good self-healing performance. The invention constructs a polyurethane molecular chain containing dynamic hindered urea bonds through the reaction of piperazine and isocyanate. The introduction of the steric group will reduce the dissociation energy of the carbon-nitrogen bond, thereby reducing the activation energy of the urea bond reaction and making the reaction rate constant faster under mild conditions. Under the action of external force, the dynamic exchange property of the urea bond of the polymer endows the material with self-healing performance; the relatively low self-healing efficiency of Comparative Example 2 and Comparative Example 3 is due to the fact that neither Comparative Example 2 nor Comparative Example 3 has the dynamic borate ester structure formed by the two hydroxyl groups on 1,4-benzenediboronic acid and DL-3,4-dihydroxy mandelic acid. The dynamic borate ester structure is also a kind of functional group with self-healing performance, and the self-healing performance of the coating prepared by the present invention is obtained by the combined action of dynamic hindered urea bonds and dynamic borate ester structures.

[0084] It is obvious to those skilled in the art that the present invention is not limited to the details of the above-mentioned exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claimed invention.

Claims

1. A method for preparing a high temperature resistant self-repairing coating, characterized in that: The method comprises the following preparation steps: (1) reacting piperazine and chloromethyldimethylethoxysilane to obtain piperazine silane; hydrolyzing piperazine silane to obtain piperazine double-end capping; reacting D4, tetramethylcyclotetrasiloxane, and piperazine double-end capping to obtain terminal piperazine polysiloxane; (2) reacting 4-(4-pyridyl)benzaldehyde and 4-bromo-1-butene to obtain pyridinium quaternary ammonium salt; reacting pyridinium quaternary ammonium salt, 2,4-dimethyl-1H-pyrrole, and boron trifluoride ether to obtain alkenyl fluoroboron dipyrrole; reacting alkenyl fluoroboron dipyrrole and N-iodosuccinimide to obtain alkenyl iodofluoroboron dipyrrole; (3) reacting terminal piperazine polysiloxane, 4,4'-dicyclohexylmethane diisocyanate, melamine, and caprolactam to obtain a pre-modified polyurethane; (4) reacting the pre-modified polyurethane and vinyl iodinated fluoroborane dipyrrole to obtain a modified polyurethane; (5) reacting acyl chloride carbon nanotubes and 2-tert-butyl-4-aminophenol to obtain pretreated carbon nanotubes; (6) reacting the pretreated carbon nanotubes and DL-3,4-dihydroxymandelic acid to obtain pre-modified carbon nanotubes; reacting the pre-modified carbon nanotubes and 1,4-phenylenediboric acid to obtain modified carbon nanotubes; (7) The following raw materials: modified polyurethane, modified carbon nanotubes, defoaming agent, additive, curing agent, solvent, and leveling agent are mixed to obtain a high temperature resistant self-healing coating.

2. The method for preparing a high temperature resistant self-repairing coating according to claim 1, characterized in that: The preparation method of the terminal piperazine polysiloxane in step (1) is as follows: piperazine and dioxane are weighed in a mass ratio of 1: (20-30), piperazine is dissolved in dioxane at 90° C. under nitrogen protection, the temperature is lowered to 80° C., chloromethyldimethylethoxysilane is added in an equal molar ratio to piperazine, the reaction is carried out for 2-3 hours, and piperazine silane is obtained by filtering and vacuum distillation; piperazine silane, ethanol and pure water are mixed in a mass ratio of 1: (10-20): (10-20), the pH value is adjusted to 4 with hydrochloric acid, the reaction is carried out at 50° C. for 5 hours, and vacuum rotary distillation is carried out to obtain to a piperazine double head; under nitrogen protection, D4, tetramethylcyclotetrasiloxane and tetramethylammonium hydroxide are mixed in a mass ratio of 1: (0.8-1.0): (0.01-0.02), the temperature is raised to 90-100°C and the reaction is carried out for 5-6 hours, 0.2-0.3 times the mass of D4 is added to the piperazine double head and stirring is continued for 2-3 hours, the temperature is raised to 150°C and the reaction is carried out for 50-60 minutes, and a terminal piperazine polysiloxane is obtained by reduced pressure distillation at 100°C; the terminal piperazine polysiloxane has a molecular weight of 2000; the D4 is octamethylcyclotetrasiloxane.

3. The method for preparing a high temperature resistant self-repairing coating according to claim 1, characterized in that: The preparation method of the vinyl iodide fluoroboron dipyrrole in step (2) is as follows: at 60-70° C., 4-(4-pyridyl)benzaldehyde, 4-bromo-1-butene, and acetonitrile are mixed and stirred in a mass ratio of 1:(0.75-0.8):(20-30) for 12-14 hours, and pyridine quaternary ammonium salt is obtained by rotary evaporation under reduced pressure, washing, and drying; under argon protection, pyridine quaternary ammonium salt, 2,4-dimethyl-1H-pyrrole, trifluoroacetic acid, and dichloromethane are mixed, stirred in dark for 10-12 hours, 2,3-dichloro-5,6-dicyano-p-benzoquinone is added, stirring in dark for 1-2 hours, and finally triethylamine and boron trifluoride ether are added, stirred in dark for 10-12 hours, and vinyl fluoride is obtained by rotary evaporation under reduced pressure, washing, and drying. Boron dipyrrole; the molar ratio of pyridine quaternary ammonium salt, 2,4-dimethyl-1H-pyrrole, 2,3-dichloro-5,6-dicyano-p-benzoquinone, and triethylamine is 1:(2.1-2.3):(1-1.2):(10-10.5); the volume ratio of 2,4-dimethyl-1H-pyrrole, dichloromethane, trifluoroacetic acid, and boron trifluoride ether is 1:(130-140):(1.7-1.9):(1-2); vinyl fluoroboron dipyrrole and N-iodosuccinimide are mixed and dissolved in dichloromethane (120-140 times the mass of vinyl fluoroboron dipyrrole) in a molar ratio of 1:(4.1-4.3), stirred at room temperature for 4-5 hours, and evaporated under reduced pressure to obtain vinyl iodo fluoroboron dipyrrole.

4. The method for preparing a high temperature resistant self-repairing coating according to claim 1, characterized in that: The preparation method of the pre-modified polyurethane in step (3) is as follows: piperazine-terminated polysiloxane and N,N-dimethylformamide are mixed, the temperature is raised to 50°C, 4,4'-dicyclohexylmethane diisocyanate, dibutyltin dilaurate and melamine are added, the temperature is raised to 80-90°C, the reaction is continued for 4-5 hours, caprolactam is added, and the reaction is continued at 70°C for 3 hours to obtain the pre-modified polyurethane; the mass ratio of piperazine-terminated polysiloxane, 4,4'-dicyclohexylmethane diisocyanate, melamine, dibutyltin dilaurate, N,N-dimethylformamide and caprolactam is 1:(0.2-0.25):(0.02-0.03):(0.005-0.006):(5-6):(0.02-0.03).

5. The method for preparing a high temperature resistant self-repairing coating according to claim 1, characterized in that: The preparation method of the modified polyurethane in step (4) is as follows: pre-modified polyurethane, vinyl iodinated fluoroborane dipyrrole, Custer catalyst, and N,N-dimethylformamide are mixed in a mass ratio of 1:(0.2-0.3):(0.001-0.002):(20-30), heated to 85°C, reacted for 4-5h, and subjected to reduced pressure rotary evaporation to obtain the modified polyurethane; the Custer catalyst is di(1,3-divinyl-1,1,3,3-tetramethyldisiloxane) platinum.

6. The method for preparing a high temperature resistant self-repairing coating according to claim 1, characterized in that: The preparation method of the pretreated carbon nanotubes in step (5) is as follows: carboxylated carbon nanotubes, thionyl chloride, and N,N-dimethylformamide are mixed in a mass ratio of 1:(150-170):(5-6), heated to 70°C and stirred for 20-24 hours, and filtered, washed, and dried to obtain chlorinated carbon nanotubes; chlorinated carbon nanotubes, 2-tert-butyl-4-aminophenol, triethylamine, and trifluoroacetic acid are mixed in a mass ratio of 1:(0.3-0.4):(1.1-1.2):(5-6) for 1-2 hours, and filtered, washed, and dried to obtain pretreated carbon nanotubes.

7. The method for preparing a high temperature resistant self-repairing coating according to claim 1, characterized in that: The preparation method of the modified carbon nanotubes in step (6) is as follows: pretreated carbon nanotubes, DL-3,4-dihydroxymandelic acid and trifluoroacetic acid are mixed in a mass ratio of 1:(0.5-0.7):(3-4), heated to 95-100°C under nitrogen protection, and methanesulfonic acid with a mass of 0.01 times that of trifluoroacetic acid is added to react for 10-12 hours, and the pre-modified carbon nanotubes are obtained by filtering, washing and drying; pre-modified carbon nanotubes, 1,4-phenylenediboric acid and ethanol are mixed in a mass ratio of 1:(0.2-0.3):(30-40), heated to 40-50°C to react for 8-10 hours, and the modified carbon nanotubes are obtained by filtering, washing and drying.

8. The method for preparing a high temperature resistant self-repairing coating according to claim 1, characterized in that: The amounts of the raw materials used in step (7) are as follows: by mass, 100 parts of modified polyurethane, 3-5 parts of modified carbon nanotubes, 1-2 parts of defoaming agent, 3-5 parts of auxiliary agent, 15-20 parts of curing agent, 30-40 parts of solvent, and 1-2 parts of leveling agent; the defoaming agent model is BYK1758; the auxiliary agent is a mixture of tetrakistriphenylphosphine palladium and sodium carbonate in a mass ratio of 1:10; the curing agent model is XCT-802; the solvent is xylene; and the leveling agent model is BYK-333.

9. The method for preparing a high temperature resistant self-repairing coating according to claim 6, characterized in that: The model of the carboxylated carbon nanotube is CNT300.

10. A high temperature resistant self-repairing coating prepared according to the preparation method of the high temperature resistant self-repairing coating according to any one of claims 1 to 9.