A waterborne automotive coating with strong adhesion and its preparation method

Abstract

The present invention discloses a waterborne coating with strong adhesion and a preparation method thereof, belonging to the technical field of waterborne coatings. The method comprises the following steps: catechol-modified acrylic acid with an amino group at the end, a flexible ester monomer, an aldehyde group olefin, and an organic solvent are mixed and dissolved, and then a radical initiator is added and heated for reaction to obtain a modified polyacrylic acid mixture; the modified polyacrylic acid mixture, an organosilicon leveling agent solution, a composite emulsifier, and deionized water are mixed and stirred for emulsification to obtain the waterborne coating with strong adhesion. According to the principle of bionics, the present invention first introduces catechol derivatives into acrylic monomers, and realizes strong adhesion to automotive substrates through the polymer network structure formed by the strong hydrogen bond crosslinking and metal coordination of catechol derivatives. Moreover, the amino group and aldehyde group on the modified polyacrylic acid polymer can crosslink to form a dynamic imine structure, improving the high-temperature resistance of the coating film formed after coating, and realizing the functions of self-repair and strong adhesion.

Description

Technical Field

[0001] The present invention belongs to the technical field of waterborne coatings, and particularly relates to a waterborne coating with strong adhesion and a preparation method thereof. Background Art

[0002] Automotive coatings refer to coatings sprayed on the surface of vehicle bodies or other components during the manufacturing process of motor vehicles, including cars, electric vehicles, railway transportation vehicles, etc. High comprehensive performance requirements are imposed on their coatings, high requirements are imposed on painting and construction, and their usage range is wide, the consumption is large, the varieties are numerous, and the uses are very diverse. There are many types of automotive coatings developed, including coatings made of various materials such as alkyd resins, acrylic resins, and urethane resins. New automotive coatings are constantly improving the application of automotive coatings in practice. With the increasingly serious global environmental problems, the environmental protection of automotive coatings has attracted more and more attention. In the use of automotive coatings, the content of volatile organic compounds in the air during the painting process increases. Under the action of ultraviolet light, certain types of photochemical reaction-type organic volatiles generate highly toxic substances, which also have a certain destructive effect on the ozone layer. With the gradual strengthening of people's environmental protection awareness and the increasing requirements for industrial environmental protection, especially in the fields of adhesives, inks, and coatings, countries around the world are formulating emission standards for the solvent volatile components (VOC) of film-forming substances. The solvent control directive introduced in Europe regarding the emission limit of volatile organic compounds during the automotive painting process strictly restricts that the emissions of organic volatiles from all coatings on the painting production line of household cars must be less than or equal to 45 g per square meter of the vehicle body painting area. Germany has even stricter requirements for the emission of volatile organic compounds, and the emission requirement is that the total amount of solvent volatiles in the vehicle body painting area shall not be higher than. It can be seen that the automotive coating industry has long had strict requirements for the emission of volatile organic compounds in the painting of coatings. In order to meet these strict requirements, a series of new coatings containing no or less volatile organic compounds, such as powder coatings, waterborne coatings, and high-solids coatings, have been developed and applied to industrial production.

[0003] The main types of environmentally friendly automotive coatings are high-solids coatings, powder coatings, and waterborne coatings. The performance of high-solids coatings is no different from that of general solvent-based coatings, except that they have a higher solids content at the application viscosity. The solids content of high-solids coatings can be as high as over 65% at the application viscosity, and the solids content of intermediate coats can be even higher. To reduce the content of organic solvents, in clear topcoats without pigments, the solids content of two-component coatings is higher than that of one-component coatings. In photocurable coatings, unsaturated olefin compounds not only act as solvents but also participate in the reaction to become components of the coating, so the emissions of volatile organic compounds from high-solids coatings are extremely low. Powder coatings were first used in the automotive industry for some anti-corrosion black paint parts with low decorative requirements, and later developed into primers and intermediate coats for automotive parts, such as coatings for vehicle bases and bearings. The distinct feature of waterborne coatings is that water is used as the dispersion medium, with water as the continuous phase and the resin generally existing in particulate form as the dispersed phase. Waterborne coatings are environmentally friendly coatings. As a renewable and non-toxic solvent, water avoids the risk of fire during the construction process, the coating tools are easy to clean, and resources are saved. The number of water-soluble coatings worldwide is increasing, and their application in the coating industry is also becoming more widespread. From the perspective of environmental protection, the development trend of automotive coatings is high solidification, solvent-free, and waterborne.

[0004] Although waterborne coatings have the above excellent properties, due to the large number of hydrophilic groups in waterborne coatings, they are prone to reducing the water resistance and anti-corrosion properties of the coating. Therefore, some improvements have been made in the prior art.

[0005] Patent CN109054612A discloses a waterborne environmentally friendly automotive paint containing ultramarine blue pigment and its preparation method. The invention uses acid-resistant ultramarine blue pigment, methyl ethylene glycol, nano-titanium dioxide, defoamer, dispersant, deionized water, aliphatic polyurethane dispersion, and polyurethane associative rheology modifier as raw materials, and obtains a waterborne environmentally friendly automotive paint with good adhesion and water resistance through mixing and grinding.

[0006] Patent CN111171659A discloses a waterborne environmentally friendly paint for the exterior of automobiles and its preparation method. The invention uses waterborne acrylic resin, tributyl phosphate, dioctyl phthalate, ethylene glycol, rubidium magnetic powder, carboxymethyl cellulose, oxidized polyethylene wax, water, and waterborne wax as raw materials, and obtains a paint layer with good adhesion, high temperature resistance, and humidity resistance through mixing and stirring.

[0007] Patent CN117165169A discloses a corrosion-resistant waterborne coating for automobiles and its preparation process. In this invention, linolenic acid, pentaerythritol, 9-(3,5-dicarboxyphenyl)-3,6-carbazole dicarboxylic acid, phthalic anhydride, maleic anhydride, epoxy resin, and ethylene glycol monobutyl ether are mixed and reacted at high temperature to obtain modified alkyd polyol; the modified alkyd polyol is reacted with diisocyanate to obtain a waterborne resin; deionized water, the waterborne resin, and additives are stirred, mixed, and dispersed, and then mixed with titanium dioxide and curing agent to obtain a film layer with good adhesion and corrosion resistance.

[0008] The above improvements mainly focus on improving the adhesion of the waterborne coating to enhance properties such as waterproofing and corrosion resistance. However, for the coating film layer obtained on the automobile surface by spraying or dipping the waterborne coating, due to the influence of environmental factors, the coating film layer is prone to scratches and cracking, which affects the adhesion and leads to easy peeling of the coating film, thus affecting the service life of the coating film.

[0009] Patent CN108070318A discloses a preparation method and application of a self-healing waterborne automobile coating. This invention introduces non-toxic and pollution-free inorganic non-metallic nano-silica. Due to the three-dimensional silica structure of nano-silica, it shows strong activity on the surface and has abundant hydrogen bond forces. A nano-modified polyurethane aqueous dispersion for automobiles is prepared. At the same time, it is compounded with an aqueous acrylic dispersion and crosslinked and cured into a film through a hydrophilic modified polyisocyanate. A polyurethane network structure with a high crosslinking density has many hydrogen bonds. When the hard and flexible paint film is scratched externally, the main chain deforms but does not break, the hydrogen bonds open and are restored after the external force is removed and reorganized. Some scratches can be observed visually. Through external input of energy (such as sunlight), the main chain unfolds under stress, the hydrogen bonds also return to their original positions, and the scratches are weakened or disappear. Due to the many hydrogen bonds in the polyurethane network structure with a high crosslinking density, it can rely on hydrogen bonds for self-healing, improve the scratch resistance and other properties of the paint film, and thus improve the service life of the paint film; through nano-silica, the mechanical strength and interfacial interaction of the paint film are enhanced, and the adhesion between the coating and the substrate is improved. However, due to the large specific surface area and high surface energy of nano-silica, it is prone to agglomeration, and the agglomerated particles may cause uneven distribution of nano-silica in the coating, forming local concentration or deficiency, thus affecting the roughness of the coating, resulting in poor contact between the coating and the substrate, affecting the adhesion and further affecting the service life of the coating. Therefore, a dispersant that can effectively disperse nano-silica needs to be additionally introduced to improve the dispersion performance of nano-silica.

[0010] Therefore, developing a strong-adhesion waterborne automobile coating with self-healing performance without using nano materials is of great significance for improving the service life of the coating film formed by the coating adhering to the automobile. Summary of the Invention

[0011] In view of the deficiencies of the prior art, according to the dopa component that plays a major strong adsorption role on mussel adhesive protein, based on the principle of bionics, catechol derivatives are first introduced into acrylic monomers, and then amino groups and aldehyde groups are jointly introduced into the modified polyacrylic acid polymer. The strong adhesion to automotive substrates is achieved through the polymer network structure formed by the strong hydrogen bond cross-linking and metal coordination of catechol derivatives. Moreover, the amino groups and aldehyde groups on the modified polyacrylic acid polymer are prone to undergo condensation cross-linking to form dynamic imine structures at room temperature or slightly higher temperature environments, improving the high-temperature resistance of the coating film formed after coating and realizing the functions of self-repair and strong adhesion. Specifically, the technical solution of the present invention includes the following contents:

[0012] A preparation method of a waterborne coating with strong adhesion, the preparation method comprising the following steps:

[0013] Catechol-modified acrylic acid with an amino group at the end, flexible ester monomer, aldehyde group olefin, and organic solvent are mixed and dissolved in a mass ratio of 1:0.5 - 0.6:0.1 - 0.2:3 - 4, and then a radical initiator is added and heated to 70°C - 80°C for reaction for 3h - 4h to obtain a modified polyacrylic acid mixture;

[0014] The modified polyacrylic acid mixture, organosilicon leveling agent solution, composite emulsifier, and deionized water are mixed and stirred and emulsified in a weight ratio of 10 - 25:0.1 - 0.3:0.5 - 1:6 - 13 to obtain the waterborne coating with strong adhesion.

[0015] Furthermore, the preparation method of the catechol-modified acrylic acid with an amino group at the end includes the following steps:

[0016] Acrylic acid and carboxylic acid activator are mixed in a molar ratio of 1:2 - 2.5 and anhydrous dichloromethane is added and stirred for activation to obtain an activation solution. After the activation solution is mixed with catechol derivatives, it is reacted at a temperature of 20°C - 25°C for 15h - 20h to obtain catechol-modified acrylic acid;

[0017] The catechol-modified acrylic acid, N-Boc-alcohol amine, and anhydrous dichloromethane are mixed and stirred in a mass ratio of 1:1 - 1.5:3 - 5 to form a reaction solution. The reaction solution is mixed with concentrated sulfuric acid in a mass ratio of 1:0.07 - 0.1 and reacted at a temperature of 80°C - 110°C for 6h - 8h to obtain N-Boc-catechol-modified acrylic acid;

[0018] The N-Boc-catechol-modified acrylic acid, acid solution, and methanol are mixed and stirred in a mass ratio of 1:2 - 3:5 - 8 for 2h - 3h to obtain the catechol-modified acrylic acid with an amino group at the end.

[0019] Further, the carboxylic acid activator is prepared by mixing 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 1-hydroxybenzotriazole in a molar ratio of 1 to 1.5:1.

[0020] Further, the conditions for the stirring activation include a stirring speed of 100 r / min to 200 r / min, an activation temperature of 20 °C to 25 °C, and an activation time of 10 min to 20 min.

[0021] Further, the catechol derivative includes levodopa, and the molar ratio of the catechol derivative to acrylic acid is 1.5 to 2:1. The structure of the catechol derivative needs to have an amino group and a carboxyl group. The amino group is used to crosslink with the aldehyde group to form a dynamic high-temperature-resistant imine bond, and the carboxyl group is used to introduce the catechol structure and the amino group onto the acrylic acid monomer to achieve the modification of functional groups.

[0022] Further, the preparation method of the N-Boc-alcohol amine includes the following steps:

[0023] The alcohol amine and diethyl ether are mixed and cooled to 0 °C to 5 °C. Di-tert-butyl dicarbonate is added thereto at this temperature, and then the temperature is raised to 15 °C to 20 °C and reacted for 20 h to 22 h to obtain the N-Boc-alcohol amine.

[0024] Further, the alcohol amine includes ethanolamine or 3-aminopropanol.

[0025] Further, the molar ratio of the alcohol amine to di-tert-butyl dicarbonate is 1:1 to 2.

[0026] Further, the acid solution includes hydrochloric acid or trifluoroacetic acid.

[0027] Further, the flexible ester monomer includes methyl acrylate, ethyl acrylate, butyl acrylate, or vinyl acetate.

[0028] Further, the aldehyde group olefin includes acrolein or 2-methylacrolein.

[0029] Further, the organic solvent includes DMF or DMSO.

[0030] Further, the radical initiator includes 2,2'-azobis(2-methylpropionamidine)dihydrochloride or azobisisobutyramidine hydrochloride.

[0031] Further, the organosilicon leveling agent solution includes a polyether-modified polydimethylsiloxane solution, a polyester-modified polydimethylsiloxane solution, or a polyester-modified polymethylalkylsiloxane solution.

[0032] Further, the composite emulsifier is composed of an equal amount of a nonionic emulsifier and an anionic emulsifier.

[0033] Furthermore, the non-ionic emulsifier includes octylphenol polyoxyethylene ether OP-9, octylphenol polyoxyethylene ether OP-10, EL-10 or EL-12, and the anionic emulsifier includes sodium dicyclohexyl sulfosuccinate or sodium dioctyl sulfosuccinate.

[0034] A strongly adherent waterborne coating prepared by a preparation method of a strongly adherent waterborne coating.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] (1) The reason for the strong adhesion function of mussels in the natural environment lies in the dopa structure on mussel adhesive protein. Dopa has a functional structure of catechol, which can form a cross-linked structure of a polymer network through cross-linking actions such as hydrogen bond adsorption and metal coordination generated by catechol, thereby achieving a strong adhesion ability. Based on the adhesion function of the dopa structure and the principle of molecular bionics, the present invention allows a catechol derivative to undergo an amidation condensation reaction between the amino group in the structure and the carboxyl group on acrylic acid, and then introduces the catechol structure onto the acrylic acid monomer to obtain catechol-modified acrylic acid. The strong cross-linking action of catechol forms a polymer network cross-linked structure to achieve strong adhesion to the automotive substrate. The hydrogen bond adsorption cross-linked structure is reversible and dynamic. When it is damaged, it can be dynamically adjusted and reorganized under the stimulation of the external environment to restore the hydrogen bond cross-linked structure and achieve self-repair. Then, an amino structure is introduced into the catechol-modified acrylic acid to obtain catechol-modified acrylic acid with an amino group at the end. In the modified polyacrylic acid mixture obtained after polymerization, since the amino group and the aldehyde group can easily condense and cross-link to form a high-temperature-resistant dynamic cross-linked structure, an imine bond, the high-temperature resistance of the coating is improved. The improvement of high-temperature resistance reduces the adverse effects of environmental temperature on the cracking of the coating and then the peeling off of the coating.

[0037] (2) Based on the principle of molecular bionics, the present invention realizes the strong adhesion function of waterborne automotive coatings by introducing the strong adhesion functional group of catechol into acrylic acid. However, the six carbon atoms in the benzene ring structure of catechol are connected to each other by covalent bonds, forming a planar ring structure with a conjugated system. Each carbon atom has a hydrogen atom, and the π electrons in the ring form a delocalized electron cloud, making the benzene ring have a stable conjugated system. This conjugated system and planar structure make the benzene ring more difficult to bend or twist in space, thus enhancing the rigidity. The increase in rigidity easily leads to cracks or peeling of the coating under the action of external forces, which is not conducive to improving the adhesion and service life of the coating. Therefore, according to the structural characteristics of the present invention, a flexible monomer is introduced. Due to the long alkyl chain contained after polymerization, the flexible monomer can increase the inter-chain distance of the polymer and reduce the intermolecular interaction force. Therefore, it has a large free rotation space, thus endowing it with flexibility and reducing the possibility of easy cracking and peeling of the coating caused by excessive use of the rigid benzene ring structure in catechol, and assisting in improving the strong adhesion brought by the catechol structure. Detailed implementation mode

[0038] The technical solutions of the present invention will be clearly and completely described below through 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present invention.

[0039] Unless otherwise specified, the raw materials and reagents used in the present invention below are all commercially available products, or can be prepared by known methods.

[0040] The polyether-modified polydimethylsiloxane solution, polyester-modified polydimethylsiloxane solution, polyester-modified polymethylalkylsiloxane solution, octylphenol polyoxyethylene ether OP-9, octylphenol polyoxyethylene ether OP-10, EL-10 and EL-12 are all purchased from Shanghai Banggao Chemical Co., Ltd.;

[0041] Ethanolamine, 3-aminopropanol, di-tert-butyl dicarbonate, acrylic acid, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, 1-hydroxybenzotriazole, levodopa, dopamine hydrochloride, sodium dicyclohexyl sulfosuccinate and sodium dioctyl sulfosuccinate are all purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0042] Preparation example 1:

[0043] The preparation method of N-Boc-ethanolamine specifically includes the following process:

[0044] Add 1 mol of ethanolamine into a round-bottom flask, and then add 400 mL of diethyl ether and mix well by stirring. After cooling the temperature of the round-bottom flask to 0 °C, slowly add 1 mol of di-tert-butyl dicarbonate and mix well by stirring to form a reaction system. Heat the reaction system to 15 °C and keep it warm for reaction for 20 h. After the reaction is completed, wash the product with deionized water, then extract it with ethyl acetate, and obtain N-Boc-ethanolamine through drying and rotary evaporation.

[0045] Preparation Example 2:

[0046] A preparation method of N-Boc-ethanolamine specifically includes the following process:

[0047] Add 1 mol of ethanolamine into a round-bottom flask, and then add 400 mL of diethyl ether and mix well by stirring. After cooling the temperature of the round-bottom flask to 2 °C, slowly add 1.5 mol of di-tert-butyl dicarbonate and mix well by stirring to form a reaction system. Heat the reaction system to 20 °C and keep it warm for reaction for 21 h. After the reaction is completed, wash the product with deionized water, then extract it with ethyl acetate, and obtain N-Boc-ethanolamine through drying and rotary evaporation.

[0048] Preparation Example 3:

[0049] A preparation method of N-Boc-3-aminopropanol specifically includes the following process:

[0050] Add 1 mol of 3-aminopropanol into a round-bottom flask, and then add 400 mL of diethyl ether and mix well by stirring. After cooling the temperature of the round-bottom flask to 5 °C, slowly add 2 mol of di-tert-butyl dicarbonate and mix well by stirring to form a reaction system. Heat the reaction system to 20 °C and keep it warm for reaction for 22 h. After the reaction is completed, wash the product with deionized water, then extract it with ethyl acetate, and obtain N-Boc-3-aminopropanol through drying and rotary evaporation.

[0051] Preparation Example 4:

[0052] A preparation method of levodopa-modified acrylic acid with an amino group at the end specifically includes the following process:

[0053] Weigh 1 mol of acrylic acid, 1 mol of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, and 1 mol of 1-hydroxybenzotriazole, mix them and place them in a flask. Then add 1 L of anhydrous dichloromethane to form a reaction system. Control the temperature of the reaction system at 20 °C and stir at a speed of 100 r / min for 10 min to obtain an activation solution. After the activation is completed, add 1.5 mol of levodopa to the activation solution and mix. Stir and react in a temperature environment of 20 °C for 15 h. After the reaction is completed, remove the solvent by a rotary evaporator, then add ethyl acetate for extraction to obtain an organic phase. The organic phase is rinsed with deionized water and dried with anhydrous sodium sulfate, and then the ethyl acetate is removed by a rotary evaporator to obtain levodopa-modified acrylic acid.

[0054] Take 100 g of levodopa-modified acrylic acid, 100 g of N-Boc-ethanolamine obtained in Preparation Example 1, and 300 g of anhydrous dichloromethane, mix and stir to form a reaction solution. Then carefully add 35 g of concentrated sulfuric acid and heat to 80 °C, and react for 6 h. After the reaction is completed, perform vacuum distillation to obtain N-Boc-levodopa-modified acrylic acid.

[0055] Take 100 g of N-Boc-levodopa-modified propene and mix it evenly with 500 g of methanol solution. Slowly add 200 g of hydrochloric acid solution with a molar concentration of 1 mol / L to the methanol solution of N-Boc-levodopa-modified propene and stir for 2 h. After the stirring is completed, neutralize the hydrochloric acid solution, and then perform vacuum distillation to remove methanol to obtain levodopa-modified acrylic acid with an amino group at the end group.

[0056] Preparation Example 5:

[0057] A preparation method of levodopa-modified acrylic acid with an amino group at the end group, specifically including the following process:

[0058] Weigh 1 mol of acrylic acid, 1.1 mol of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, and 1 mol of 1-hydroxybenzotriazole, mix them and place them in a flask. Then add 1 L of anhydrous dichloromethane to form a reaction system. Control the temperature of the reaction system at 20 °C and stir at a speed of 120 r / min for 12 min to obtain an activation solution. After the activation is completed, add 1.6 mol of levodopa to the activation solution and mix. Stir and react in a temperature environment of 20 °C for 16 h. After the reaction is completed, remove the solvent by a rotary evaporator, then add ethyl acetate for extraction to obtain an organic phase. The organic phase is rinsed with deionized water and dried with anhydrous sodium sulfate, and then the ethyl acetate is removed by a rotary evaporator to obtain levodopa-modified acrylic acid.

[0059] Take 100 g of levodopa-modified acrylic acid, 110 g of N-Boc-ethanolamine obtained in Preparation Example 1, and 300 g of anhydrous dichloromethane, mix and stir to form a reaction solution. Then carefully add 35.7 g of concentrated sulfuric acid and heat to 80 °C, and react for 6 h. After the reaction, perform reduced pressure distillation to obtain N-Boc-levodopa-modified acrylic acid.

[0060] Take 100 g of N-Boc-levodopa-modified propylene and 600 g of methanol solution, mix and stir evenly. Slowly add 200 g of hydrochloric acid solution with a molar concentration of 1 mol / L to the methanol solution of N-Boc-levodopa-modified propylene and stir for 2 h. After stirring, neutralize the hydrochloric acid solution, and then perform reduced pressure distillation to remove methanol to obtain levodopa-modified acrylic acid with an amino group at the end.

[0061] Preparation Example 6:

[0062] A preparation method of levodopa-modified acrylic acid with an amino group at the end, specifically including the following process:

[0063] Weigh 1 mol of acrylic acid, 1.2 mol of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, and 1 mol of 1-hydroxybenzotriazole, mix and place them in a flask, then add 1 L of anhydrous dichloromethane to form a reaction system. Control the temperature of the reaction system at 22 °C, stir and activate at a speed of 140 r / min for 14 min to obtain an activated solution. After activation, add 1.7 mol of levodopa to the activated solution and mix, and stir and react in a temperature environment of 22 °C for 17 h. After the reaction, remove the solvent with a rotary evaporator, then add ethyl acetate for extraction to obtain an organic phase. The organic phase is rinsed with deionized water and dried with anhydrous sodium sulfate, and then the ethyl acetate is removed with a rotary evaporator to obtain levodopa-modified acrylic acid.

[0064] Take 100 g of levodopa-modified acrylic acid, 120 g of N-Boc-ethanolamine obtained in Preparation Example 2, and 400 g of anhydrous dichloromethane, mix and stir to form a reaction solution. Then carefully add 49.6 g of concentrated sulfuric acid and heat to 90 °C, and react for 7 h. After the reaction, perform reduced pressure distillation to obtain N-Boc-levodopa-modified acrylic acid.

[0065] Take 100 g of N-Boc-levodopa-modified propylene and 600 g of methanol solution, mix and stir evenly. Slowly add 250 g of hydrochloric acid solution with a molar concentration of 1 mol / L to the methanol solution of N-Boc-levodopa-modified propylene and stir for 2.5 h. After stirring, neutralize the hydrochloric acid solution, and then perform reduced pressure distillation to remove methanol to obtain levodopa-modified acrylic acid with an amino group at the end.

[0066] Preparation Example 7:

[0067] A preparation method of levodopa-modified acrylic acid with an amino group at the end, specifically including the following process:

[0068] Weigh 1 mol of acrylic acid, 1.3 mol of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, and 1 mol of 1-hydroxybenzotriazole, mix them and place them in a flask. Then add 1 L of anhydrous dichloromethane to form a reaction system. Control the temperature of the reaction system at 22 °C, stir and activate it at a rotation speed of 160 r / min for 16 min to obtain an activation solution. After the activation is completed, add 1.8 mol of levodopa to the activation solution and mix. Stir and react in a temperature environment of 22 °C for 18 h. After the reaction is completed, remove the solvent by a rotary evaporator, then add ethyl acetate for extraction to obtain an organic phase. The organic phase is washed with deionized water and dried with anhydrous sodium sulfate, and then the ethyl acetate is removed by a rotary evaporator to obtain levodopa-modified acrylic acid.

[0069] Take 100 g of levodopa-modified acrylic acid, 130 g of N-Boc-ethanolamine obtained in Preparation Example 2, and 400 g of anhydrous dichloromethane, mix and stir to form a reaction solution. Then carefully add 56.7 g of concentrated sulfuric acid and heat to 100 °C, and react for 7 h. After the reaction is completed, perform vacuum distillation to obtain N-Boc-levodopa-modified acrylic acid.

[0070] Take 100 g of N-Boc-levodopa-modified propene and 700 g of methanol solution, mix and stir evenly. Slowly add 250 g of trifluoroacetic acid solution with a molar concentration of 1 mol / L to the methanol solution of N-Boc-levodopa-modified propene and stir for 2.5 h. After the stirring is completed, neutralize the hydrochloric acid solution, and then perform vacuum distillation to remove methanol to obtain levodopa-modified acrylic acid with an amino group at the end group.

[0071] Preparation Example 8:

[0072] A preparation method of levodopa-modified acrylic acid with an amino group at the end group, specifically including the following process:

[0073] Weigh 1 mol of acrylic acid, 1.4 mol of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, and 1 mol of 1-hydroxybenzotriazole, mix them and place them in a flask. Then add 1 L of anhydrous dichloromethane to form a reaction system. Control the temperature of the reaction system at 25 °C, stir and activate it at a rotation speed of 180 r / min for 18 min to obtain an activation solution. After the activation is completed, add 1.9 mol of levodopa to the activation solution and mix. Stir and react in a temperature environment of 25 °C for 19 h. After the reaction is completed, remove the solvent by a rotary evaporator, then add ethyl acetate for extraction to obtain an organic phase. The organic phase is washed with deionized water and dried with anhydrous sodium sulfate, and then the ethyl acetate is removed by a rotary evaporator to obtain levodopa-modified acrylic acid.

[0074] Take 100 g of levodopa-modified acrylic acid, 140 g of N-Boc-3-aminopropanol obtained in Preparation Example 3, and 500 g of anhydrous dichloromethane, mix and stir to form a reaction solution. Then carefully add 66.6 g of concentrated sulfuric acid and heat to 100 °C, and react for 8 h. After the reaction, distill under reduced pressure to obtain N-Boc-levodopa-modified acrylic acid.

[0075] Take 100 g of N-Boc-levodopa-modified propene and 700 g of methanol solution, mix and stir evenly. Slowly add 300 g of trifluoroacetic acid solution with a molar concentration of 1 mol / L to the methanol solution of N-Boc-levodopa-modified propene and stir for 3 h. After stirring, neutralize the hydrochloric acid solution, and then distill under reduced pressure to remove methanol to obtain levodopa-modified acrylic acid with an amino group at the end.

[0076] Preparation Example 9:

[0077] A preparation method of levodopa-modified acrylic acid with an amino group at the end, specifically including the following process:

[0078] Weigh 1 mol of acrylic acid, 1.5 mol of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, and 1 mol of 1-hydroxybenzotriazole, mix and place them in a flask, then add 1 L of anhydrous dichloromethane to form a reaction system. Control the temperature of the reaction system at 25 °C, and stir and activate for 20 min at a rotation speed of 200 r / min to obtain an activation solution. After activation, add 2 mol of levodopa to the activation solution and mix, and stir and react at a temperature of 25 °C for 20 h. After the reaction, remove the solvent by a rotary evaporator, then add ethyl acetate for extraction to obtain an organic phase. The organic phase is washed with deionized water and dried with anhydrous sodium sulfate, and then the ethyl acetate is removed by a rotary evaporator to obtain levodopa-modified acrylic acid.

[0079] Take 100 g of levodopa-modified acrylic acid, 150 g of N-Boc-3-aminopropanol obtained in Preparation Example 3, and 500 g of anhydrous dichloromethane, mix and stir to form a reaction solution. Then carefully add 75 g of concentrated sulfuric acid and heat to 110 °C, and react for 8 h. After the reaction, distill under reduced pressure to obtain N-Boc-levodopa-modified acrylic acid.

[0080] Take 100 g of N-Boc-levodopa-modified propene and 800 g of methanol solution, mix and stir evenly. Slowly add 300 g of trifluoroacetic acid solution with a molar concentration of 1 mol / L to the methanol solution of N-Boc-levodopa-modified propene and stir for 3 h. After stirring, neutralize the hydrochloric acid solution, and then distill under reduced pressure to remove methanol to obtain levodopa-modified acrylic acid with an amino group at the end.

[0081] Preparation Example 10:

[0082] Preparation method of dopamine-modified acrylic acid with amino group at the end, specifically including the following process:

[0083] Replace L-dopa in Preparation Example 9 with dopamine hydrochloride, and keep the other conditions the same as those in Preparation Example 9.

[0084] Preparation Example 11:

[0085] Preparation method of L-dopa-modified acrylic acid with amino group at the end, specifically including the following process:

[0086] Replace trifluoroacetic acid in Preparation Example 9 with acetic acid, and keep the other conditions the same as those in Preparation Example 9.

[0087] Example 1:

[0088] Preparation method of a strong adhesion waterborne coating, specifically including the following process:

[0089] Take 50 g of L-dopa-modified acrylic acid with amino group at the end obtained in Preparation Example 4, 25 g of methyl acrylate, 5 g of 2-methylacrolein, and 150 g of DMF (N,N-dimethylformamide), mix and stir them together, then add 0.4 g of 2,2'-azobis(2-methylpropionamidine) dihydrochloride and mix and stir evenly, and then raise the temperature to 70 °C and start timing the reaction for 3 h to obtain a modified polyacrylic acid mixture.

[0090] Take 10 parts by weight of the modified polyacrylic acid mixture, 0.1 part by weight of a polyether-modified polydimethylsiloxane solution, 0.5 part by weight of a composite emulsifier (composed of 0.25 part by weight of octylphenol polyoxyethylene ether OP-9 and 0.25 part by weight of sodium dicyclohexyl sulfosuccinate), and 6 parts by weight of deionized water, mix them, and stir and emulsify at a stirring speed of 500 r / min for 20 min to obtain a strong adhesion waterborne coating.

[0091] Example 2:

[0092] Preparation method of a strong adhesion waterborne coating, specifically including the following process:

[0093] Take 50 g of L-dopa-modified acrylic acid with amino group at the end obtained in Preparation Example 5, 26 g of methyl acrylate, 6 g of 2-methylacrolein, and 160 g of DMF (N,N-dimethylformamide), mix and stir them together, then add 0.57 g of 2,2'-azobis(2-methylpropionamidine) dihydrochloride and mix and stir evenly, and then raise the temperature to 72 °C and start timing the reaction for 3 h to obtain a modified polyacrylic acid mixture.

[0094] Take 13 parts by weight of the modified polyacrylic acid mixture, 0.1 part by weight of the polyether-modified polydimethylsiloxane solution, 0.6 part by weight of the composite emulsifier (a mixture of 0.3 part by weight of octylphenol polyoxyethylene ether OP-10 and 0.3 part by weight of sodium dicyclohexyl sulfosuccinate), and 7 parts by weight of deionized water, mix them, and stir and emulsify at a stirring speed of 500 r / min for 20 min to obtain a waterborne coating with strong adhesion.

[0095] Example 3:

[0096] A preparation method of a waterborne coating with strong adhesion specifically includes the following process:

[0097] Take 50 g of the L-dopa-modified acrylic acid with an amino group at the end obtained in Preparation Example 6, 27 g of ethyl acrylate, 7 g of 2-methylacrolein, and 170 g of DMF (N,N-dimethylformamide), mix and stir them together, then add 0.67 g of 2,2'-azobis(isobutyramidine) dihydrochloride and mix and stir evenly, and then raise the temperature to 74 °C and start timing the reaction for 3.5 h to obtain the modified polyacrylic acid mixture.

[0098] Take 16 parts by weight of the modified polyacrylic acid mixture, 0.2 part by weight of the polyester-modified polydimethylsiloxane solution, 0.7 part by weight of the composite emulsifier (a mixture of 0.35 part by weight of octylphenol polyoxyethylene ether OP-10 and 0.3 part by weight of sodium dioctyl sulfosuccinate), and 9 parts by weight of deionized water, mix them, and stir and emulsify at a stirring speed of 500 r / min for 20 min to obtain a waterborne coating with strong adhesion.

[0099] Example 4:

[0100] A preparation method of a waterborne coating with strong adhesion specifically includes the following process:

[0101] Take 50 g of the L-dopa-modified acrylic acid with an amino group at the end obtained in Preparation Example 7, 28 g of butyl acrylate, 8 g of acrolein, and 180 g of DMSO (dimethyl sulfoxide), mix and stir them together, then add 0.69 g of azobisisobutyramidine hydrochloride and mix and stir evenly, and then raise the temperature to 76 °C and start timing the reaction for 3.5 h to obtain the modified polyacrylic acid mixture.

[0102] Take 19 parts by weight of the modified polyacrylic acid mixture, 0.2 part by weight of the polyester-modified polydimethylsiloxane solution, 0.8 part by weight of the composite emulsifier (a mixture of 0.4 part by weight of EL-10 and 0.4 part by weight of sodium dicyclohexyl sulfosuccinate), and 10 parts by weight of deionized water, mix them, and stir and emulsify at a stirring speed of 500 r / min for 30 min to obtain a waterborne coating with strong adhesion.

[0103] Example 5:

[0104] A preparation method of a waterborne coating with strong adhesion specifically includes the following process:

[0105] Take 50 g of the L - dopa - modified acrylic acid with an amino - terminal group obtained in Preparation Example 8, 29 g of vinyl acetate, 9 g of acrolein, and 190 g of DMSO (dimethyl sulfoxide), mix and stir them together. Then add 0.88 g of 2,2'-azobis(2 - methylpropionamidine) dihydrochloride and mix and stir evenly. Then raise the temperature to 78 °C and start timing the reaction for 4 h to obtain a modified polyacrylic acid mixture.

[0106] Take 22 parts by weight of the modified polyacrylic acid mixture, 0.3 part by weight of a polyester - modified polymethylalkylsiloxane solution, 0.9 part by weight of a composite emulsifier (composed of 0.45 part by weight of EL - 10 and 0.45 part by weight of sodium dioctyl sulfosuccinate), and 12 parts by weight of deionized water, mix them, and stir - emulsify at a stirring speed of 500 r / min for 30 min to obtain a water - based coating with strong adhesion.

[0107] Example 6:

[0108] A preparation method of a water - based coating with strong adhesion, specifically including the following process:

[0109] Take 50 g of the L - dopa - modified acrylic acid with an amino - terminal group obtained in Preparation Example 9, 30 g of vinyl acetate, 30 g of acrolein, and 2000 g of DMSO (dimethyl sulfoxide), mix and stir them together. Then add 1.08 g of 2,2'-azobis(2 - methylpropionamidine) dihydrochloride and mix and stir evenly. Then raise the temperature to 80 °C and start timing the reaction for 4 h to obtain a modified polyacrylic acid mixture.

[0110] Take 25 parts by weight of the modified polyacrylic acid mixture, 0.3 part by weight of a polyester - modified polymethylalkylsiloxane solution, 1 part by weight of a composite emulsifier (composed of 0.5 part by weight of EL - 12 and 0.5 part by weight of sodium dioctyl sulfosuccinate), and 13 parts by weight of deionized water, mix them, and stir - emulsify at a stirring speed of 500 r / min for 30 min to obtain a water - based coating with strong adhesion.

[0111] Comparative Example 1:

[0112] A preparation method of a water - based coating with strong adhesion, specifically including the following process:

[0113] Replace the L - dopa - modified acrylic acid with an amino - terminal group in Example 6 with the dopamine - modified acrylic acid with an amino - terminal group obtained in Preparation Example 10, and keep the other conditions the same as those in Example 6.

[0114] Comparative Example 2:

[0115] A preparation method of a water - based coating with strong adhesion, specifically including the following process:

[0116] The L-DOPA-modified acrylic acid with an amino terminal group in Example 6 was replaced with the L-DOPA-modified acrylic acid with an amino terminal group obtained in Preparation Example 11, and the other conditions remained the same as in Example 6.

[0117] Comparative Example 3:

[0118] A method for preparing a water-based coating with strong adhesion specifically comprises the following steps:

[0119] The vinyl acetate in Example 6 was replaced by methyl methacrylate, and the other conditions remained the same as in Example 6.

[0120] Comparative Example 4:

[0121] A method for preparing a water-based coating with strong adhesion specifically comprises the following steps:

[0122] The vinyl acetate in Example 6 was replaced by ethyl methacrylate, and the other conditions remained the same as in Example 6.

[0123] Comparative Example 5:

[0124] A method for preparing a water-based coating with strong adhesion specifically comprises the following steps:

[0125] The azobisisobutylimidazoline hydrochloride in Example 6 was replaced by ammonium persulfate, and the other conditions remained the same as in Example 6.

[0126] Comparative Example 6:

[0127] A method for preparing a water-based coating with strong adhesion specifically comprises the following steps:

[0128] The azobisisobutylimidazoline hydrochloride in Example 6 was replaced by benzoyl peroxide, and the other conditions were kept the same as in Example 6.

[0129] The surface of the tinplate was polished with water sandpaper, and then the impurities on the polished surface were wiped with acetone, and then dried with nitrogen. The strong adhesion water-based coatings obtained in Examples 1 to 6 and Comparative Examples 1 to 6 were applied on the tinplate to form a coating film. Then, according to "GB / T 5210-2006 Paint and Varnish Pull-off Adhesion Test", the tensile strength of the coating film when it was destroyed after drying for 10 days was recorded. The results are shown in Table 1:

[0130] Table 1

[0131]

[0132]

[0133] Sand the surface of the tinplate with water sandpaper, then wipe the impurities on the sanded surface with acetone, and then blow dry with nitrogen. Apply the strongly adherent waterborne coatings obtained in Examples 1-6 and Comparative Examples 1-6 on the tinplate to prepare a coating film, and then place it at a high temperature of 200 °C for 4 h. After the high-temperature treatment, cool it to room temperature and observe whether there are phenomena such as cracking and peeling of the coating film. Then, test its adhesion grade according to "GB / T 9286-2021 Paints and varnishes - Cross-cut test", and the results are shown in Table 2 below:

[0134] Table 2

[0135] Material source Condition of surface coating film Adhesion grade Example 1 A few cracks appear and a little peeling off occurs Grade 1 Example 2 The surface is intact without damage or peeling off Grade 0 Example 3 The surface is intact without damage or peeling off Grade 0 Example 4 The surface is intact without damage or peeling off Grade 0 Example 5 The surface is intact without damage or peeling off Grade 0 Example 6 The surface is intact without damage or peeling off Grade 0 Comparative example 1 The surface blisters and cracks, and a large amount of exfoliates are produced Grade 4 Comparative example 2 The surface blisters and cracks, and a little exfoliates are produced Grade 3 Comparative example 3 The surface blisters and cracks, and a large amount of exfoliates are produced Grade 4 Comparative example 4 The surface blisters and cracks, and a large amount of exfoliates are produced Grade 4 Comparative example 5 The surface blisters and cracks, and a little exfoliates are produced Grade 3 Comparative example 6 The surface blisters and cracks, and a little exfoliates are produced Grade 3

[0136] Sand the surface of the tinplate with water sandpaper, then wipe the impurities on the sanded surface with acetone, and then blow dry with nitrogen. Apply the strongly adherent waterborne coatings obtained in Examples 1-6 and Comparative Examples 1-6 on the tinplate to prepare a coating film, and then scratch the surface of the coating film with a pencil. Place them in a hot air environment at room temperature (25 °C) and 50 °C respectively, and record the scratch repair time. The results are shown in Table 3 below:

[0137] Table 3

[0138]

[0139] It can be seen from the experimental results in Tables 1-3 above that:

[0140] (1) In the present invention, levodopa with catechol is introduced into acrylic monomers, and then an amino structure and an aldehyde structure are jointly introduced into the modified polyacrylic acid polymer. The strong hydrogen bond cross-linking and metal coordination of catechol derivatives are used to form a polymer network structure to achieve strong adhesion to automotive substrates. Moreover, the amino and aldehyde groups on the modified polyacrylic acid polymer are prone to condensation cross-linking to form a dynamic imine structure at room temperature or slightly higher temperature environments, improving the high-temperature resistance of the coating formed after coating, realizing the functions of self-repair and strong adhesion, and the increase in temperature has a promoting effect on the self-repair performance.

[0141] (2) It can be seen from Comparative Example 1 that although dopamine also has an active structure of catechol, due to the lack of an amino structure that can form a dynamic imine bond cross-linking with the aldehyde group, the high-temperature resistance is poor, which is not conducive to the adhesion of the coating film.

[0142] (3) It can be seen from Comparative Example 2 that since the acidity of acetic acid is much lower than that of trifluoroacetic acid, the acidic condition is not sufficient to completely remove the Boc protecting group, so fewer amino functional groups are released, and thus the number of formed dynamic imine bonds is relatively low, resulting in poor high-temperature resistance and being not conducive to the adhesion of the coating film.

[0143] (4) It can be seen from Comparative Examples 3 and 4 that due to the presence of methyl groups on the double bonds of methyl methacrylate and ethyl methacrylate, the rotation of the molecular chains is restricted, resulting in a more compact and regular chain conformation. This reduces the free movement between chains and increases the rigidity. When the coating film is damaged by external forces, it is prone to brittle fracture, which is not conducive to the adhesion of the coating.

[0144] (5) It can be seen from Comparative Examples 5 and 6 that although ammonium persulfate and benzoyl peroxide can also initiate the polymerization of carbon-carbon double bonds, due to their strong oxidizing properties, they easily cause the catechol structure to be oxidized in advance and lose the active structure of catechol. Therefore, it is difficult to achieve self-repair after being scratched by external forces.

[0145] The above-described embodiments have detailed the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements fall within the scope of the present invention claimed.

Claims

1. A method for preparing a water-based coating with strong adhesion, characterized in that: The preparation method comprises the following steps: The catechol-modified acrylic acid with an amino terminal, a flexible ester monomer, an aldehyde olefin and an organic solvent are mixed and dissolved in a mass ratio of 1:0.5-0.6:0.1-0.2:3-4, and a free radical initiator is added, heated to 70°C-80°C and reacted for 3h-4h to obtain a modified polyacrylic acid mixture; The modified polyacrylic acid mixture, the organic silicon leveling agent solution, the composite emulsifier and the deionized water are mixed and stirred in a weight ratio of 10 to 25: 0.1 to 0.3: 0.5 to 1: 6 to 13 to obtain the water-based coating with strong adhesion; The preparation method of catechol-modified acrylic acid with amino terminal groups comprises the following steps: Acrylic acid and a carboxylic acid activator are mixed in a molar ratio of 1:2 to 2.5, and anhydrous dichloromethane is added and stirred to obtain an activation solution, and the activation solution is mixed with a catechol derivative and then reacted in a temperature environment of 20° C. to 25° C. for 15 h to 20 h to obtain catechol-modified acrylic acid; The catechol-modified acrylic acid, N-Boc-alcoholamine and anhydrous dichloromethane are mixed and stirred in a mass ratio of 1:1 to 1.5:3 to 5 to form a reaction solution, and the reaction solution is mixed with concentrated sulfuric acid in a mass ratio of 1:0.07 to 0.1 and reacted in a temperature environment of 80° C. to 110° C. for 6 h to 8 h to obtain N-Boc-catechol-modified acrylic acid; The N-Boc-catechol-modified acrylic acid, the acid solution and the methanol are mixed and stirred at a mass ratio of 1:2-3:5-8 for 2h-3h to obtain the catechol-modified acrylic acid having an amino terminal group; The catechol derivative is levodopa, and the molar ratio of the catechol derivative to acrylic acid is 1.5-2:

1.

2. The method for preparing a water-based coating with strong adhesion according to claim 1, characterized in that: The carboxylic acid activator is prepared by mixing 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride and 1-hydroxybenzotriazole in a molar ratio of 1 to 1.5:

1.

3. The method for preparing a strong adhesion water-based coating according to claim 1, characterized in that: The preparation method of the N-Boc-alcoholamine comprises the following steps: After the alcohol amine and ether are mixed, the temperature is lowered to 0°C to 5°C, di-tert-butyl dicarbonate is added and mixed at this temperature, and then the temperature is raised to 15°C to 20°C and reacted for 20h to 22h to obtain the N-Boc-alcohol amine.

4. The method for preparing a water-based coating with strong adhesion according to claim 1, characterized in that: The flexible ester monomer includes methyl acrylate, ethyl acrylate, butyl acrylate or vinyl acetate.

5. The method for preparing a strong adhesion water-based coating according to claim 1, characterized in that: The aldehyde-based olefin includes acrolein or 2-methylacrolein.

6. The method for preparing a water-based coating with strong adhesion according to claim 1, characterized in that: The free radical initiator includes 2,2'-azobisisobutylamidine dihydrochloride or azobisisobutylimidazoline hydrochloride.

7. The method for preparing a water-based coating with strong adhesion according to claim 1, characterized in that: The composite emulsifier is composed of a nonionic emulsifier and an anionic emulsifier mixed in equal amounts.

8. A water-based coating with strong adhesion prepared by the method for preparing a water-based coating with strong adhesion according to any one of claims 1 to 7.

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