Water-based automobile coating with strong adhesive force and preparation method of water-based automobile coating

Abstract

The invention discloses a high-adhesion water-based paint and a preparation method thereof, and belongs to the technical field of water-based paints. Comprising the following steps: mixing and dissolving catechol modified acrylic acid of which the end group is amino, a flexible ester monomer, aldehyde olefin and an organic solvent, adding a free radical initiator, and heating for reaction to obtain a modified polyacrylic acid mixture; mixing, stirring and emulsifying the modified polyacrylic acid mixture, an organic silicon flatting agent solution, a compound emulsifier and deionized water to obtain the water-based paint with strong adhesive force. According to the bionics principle, a catechol derivative is introduced into an acrylic monomer, and strong adhesion to an automobile base material is realized through a polymer net structure formed by strong hydrogen bond crosslinking, metal coordination and other actions of the catechol derivative; and amino groups and aldehyde groups on the modified polyacrylic acid polymer can be crosslinked to form a dynamic imine structure, so that the high-temperature resistance of a coating film formed after the coating is coated is improved, and the functions of self-repairing and strong adhesion are realized.

Description

Technical Field

[0001] The invention belongs to the technical field of water-based coatings, and in particular relates to a water-based coating with strong adhesion and a preparation method thereof. Background Art

[0002] Automotive coatings refer to the coatings sprayed on the body or other parts of motor vehicles, including automobiles, electric vehicles, and railway transportation vehicles, during the manufacturing process. The comprehensive performance of the coating is very high, and the requirements for coating and construction are high. It has a wide range of applications, large dosage, and many varieties and uses. There are many types of automotive coatings, including coatings made of various materials such as alkyd resins, acrylic resins, and urethane resins. New automotive coatings are also constantly improving the application of automotive coatings in practice. As global environmental problems become increasingly serious, the environmental protection of automotive coatings is also receiving more and more attention. In the use of automotive coatings, the content of volatile organic compounds in the air caused by the coating process increases. Certain types of photochemically reactive organic volatiles generate highly toxic substances under the action of ultraviolet rays, which also have a certain destructive effect on the ozone layer. As people's environmental awareness gradually increases, industrial environmental protection requirements are also getting higher and higher, especially in the fields of adhesives, inks, and coatings. Countries around the world are formulating emission standards for volatile solvent components (VOC) of film-forming materials. The solvent control directive issued by Europe has set strict limits on the emission of volatile organic compounds in the automobile painting process, which strictly limits the emission of volatile organic compounds from all coatings in the painting production line of family cars to less than or equal to 45g per square meter of the body painting area. Germany has even stricter requirements on the emission of volatile organic compounds, requiring that the total amount of solvent volatilization in the body painting area shall not be higher than 45g. It can be seen that the automotive coatings industry has long had strict requirements on the emission of volatile organic compounds in the coatings industry. In order to meet these strict requirements, a series of new coatings that do not contain volatile organic compounds or have a low content of volatile organic compounds, such as powder coatings, water-based coatings, high-solid coatings, etc., have been developed and applied to industrial production.

[0003] Environmentally friendly automotive coatings mainly include high-solid coatings, powder coatings and water-based coatings. The performance of high-solid coatings is no different from that of general solvent-based coatings, except that the solid content is higher at the construction viscosity. The solid content of high-solid coatings at the construction viscosity can be as high as 65% or more, and the solid content of mid-coat coatings can be even higher. In order to reduce the content of organic solvents, in pigment-free clear varnishes, the solid content of two-component coatings is higher than that of single-component coatings. In light-curing coatings, unsaturated olefin compounds act as solvents and participate in the reaction to become components of the coating, so the emission of volatile organic compounds in high-solid coatings is extremely small. 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 mid-coats for automotive parts, such as coatings for vehicle bases and vehicle bearings. The distinctive feature of water-based coatings is that water is used as the dispersion medium, water is the continuous phase, and resin generally exists in granular form as the dispersed phase. Water-based paint is an environmentally friendly paint. As a renewable and non-toxic solvent, water avoids the risk of fire during the construction process. The painting tools are easy to clean and save resources. There are more and more water-soluble paints in the world, and its application in the coating industry is becoming more and more extensive. From the perspective of environmental protection, the development trend of automotive coatings is high solid decomposition, solvent-free and water-based.

[0004] Although water-based paint has the above excellent properties, due to the presence of a large number of hydrophilic groups in water-based paint, it is easy to reduce the water resistance and corrosion resistance of the coating. For this reason, some improvements have been made in the prior art.

[0005] Patent CN109054612A discloses a water-based environmentally friendly automobile paint containing ultramarine blue pigment and a preparation method thereof. The invention uses acid-resistant ultramarine blue pigment, methyl glycol, nano titanium dioxide, defoamer, dispersant, deionized water, aliphatic polyurethane dispersion and polyurethane associative rheological agent as raw materials, and obtains a water-based environmentally friendly automobile paint with good adhesion and water resistance through mixed grinding.

[0006] Patent CN111171659A discloses a water-based environmentally friendly paint for automobile exterior and a preparation method thereof. The invention uses: water-based acrylic resin, tributyl phosphate, dioctyl phthalate, ethylene glycol, nephelochromic magnetic powder, carboxymethyl cellulose, oxidized polyethylene wax, water and water-based wax as raw materials, and obtains a paint layer that is resistant to high temperature and moisture and has good adhesion by mixing and stirring.

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

[0008] The above improvements are mainly focused on improving the adhesion of water-based paint to improve waterproof and anti-corrosion properties. However, the coating layer obtained on the surface of the car by spraying or dipping the water-based paint is easily scratched and cracked due to the influence of environmental factors, which affects the adhesion, causes the coating to fall off easily, and affects the service life of the coating.

[0009] Patent CN108070318A discloses a preparation method and application of a self-repairing water-based automotive coating. The invention introduces non-toxic, non-polluting inorganic non-metallic nano-silicon dioxide. Since nano-silicon dioxide has a three-dimensional silica structure, the surface shows strong activity and gathers abundant hydrogen bonding forces to prepare a nano-modified polyurethane aqueous dispersion for automobiles. At the same time, it is compounded with an aqueous acrylic dispersion and cross-linked and cured to form a film through hydrophilic modified polyisocyanate to form a polyurethane network structure with a high cross-linking density and more hydrogen bonds. The hard and flexible paint film is deformed but not broken under the action of external scratches. The hydrogen bonds are opened and restored after the external force is eliminated, and then reorganized. Some scratches can be found from the appearance. Through external energy input (such as sunlight), the main chain stretches under stress, and the hydrogen bonds return to their original positions, and the scratches are weakened or disappear. The high cross-linking density of the polyurethane network structure has more hydrogen bonds, which can rely on hydrogen bonds for self-repair, improve the scratch resistance of the paint film, and thus increase the service life of the paint film; nano-silicon dioxide is used to enhance the mechanical strength and interface interaction of the paint film, and improve the adhesion between the coating and the substrate. However, due to the large specific surface area and high surface energy of nano-silicon dioxide, it is easy to agglomerate, and the agglomerated particles may cause uneven distribution of nano-silicon dioxide in the coating, forming local concentration or deficiency, thereby affecting the roughness of the coating, resulting in poor contact between the coating and the substrate, affecting the adhesion and thus affecting the service life of the coating. For this reason, it is necessary to introduce additional dispersants that can effectively disperse nano-silicon dioxide to improve the dispersion properties of nano-silicon dioxide.

[0010] Therefore, developing a water-based automotive coating with strong adhesion and self-repairing properties without using nanomaterials is of great significance for improving the service life of the coating film formed by the coating attached to the car. Summary of the invention

[0011] In view of the deficiencies of the prior art, the present invention, based on the dopa component that plays a major role in strong adsorption on mussel mucin, first introduces catechol derivatives into acrylic monomers according to the principle of bionics, and then introduces amino structures and aldehyde structures into modified polyacrylic acid polymers. The polymer network structure formed by the strong hydrogen bond crosslinking and metal coordination of catechol derivatives achieves strong adhesion to the automotive substrate, and the amino and aldehyde groups on the modified polyacrylic acid polymer are easily condensed and crosslinked at room temperature or slightly higher temperature environments to form a dynamic imine structure, which improves the high temperature resistance of the coating film formed after coating, and realizes the functions of self-repair and strong adhesion. Specifically, the technical solution of the present invention includes the following contents:

[0012] A method for preparing a water-based coating with strong adhesion, the method comprising the following steps:

[0013] 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;

[0014] The modified polyacrylic acid mixture, the organic silicon leveling agent solution, the composite emulsifier and the deionized water are mixed, stirred and emulsified 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.

[0015] Furthermore, the preparation method of catechol-modified acrylic acid having an amino terminal group comprises the following steps:

[0016] 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;

[0017] 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;

[0018] The N-Boc-catechol-modified acrylic acid, acid solution and 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 with amino terminal groups.

[0019] Furthermore, 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] Furthermore, the stirring activation conditions 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] Furthermore, 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 cross-link 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 into the acrylic acid monomer to achieve the modification of the functional group.

[0022] Furthermore, the preparation method of the N-Boc-alcoholamine comprises the following steps:

[0023] 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.

[0024] Furthermore, the alcoholamine includes ethanolamine or 3-aminopropanol.

[0025] Furthermore, the molar ratio of the alcoholamine to di-tert-butyl dicarbonate is 1:1-2.

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

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

[0028] Furthermore, the aldehyde-based olefin includes acrolein or 2-methylacrolein.

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

[0030] Furthermore, the free radical initiator includes 2,2'-azobisisobutylamidine dihydrochloride or azobisisobutylimidazoline hydrochloride.

[0031] Furthermore, the organic silicon leveling agent solution includes a polyether-modified polydimethylsiloxane solution, a polyester-modified polydimethylsiloxane solution or a polyester-modified polymethylalkylsiloxane solution.

[0032] Furthermore, the composite emulsifier is composed of a nonionic emulsifier and an anionic emulsifier mixed in equal amounts.

[0033] Furthermore, the nonionic 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 method for preparing a water-based paint with strong adhesion prepares a water-based paint with strong adhesion.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) The reason why mussels have strong adhesion function in the natural environment is that the DOPA structure on the mussel mucin has the functional structure of catechol, and can form a high molecular network cross-linking structure through cross-linking effects such as hydrogen bond adsorption and metal coordination generated by catechol, thereby achieving strong adhesion ability. According to the adhesion function of the DOPA structure, based on the principle of molecular bionics, the catechol derivative undergoes an amidation condensation reaction with the carboxyl group on acrylic acid through the amino group on the structure, and then the catechol structure is introduced into the acrylic acid monomer to obtain catechol-modified acrylic acid. The high molecular network cross-linking structure formed by the strong cross-linking effect of catechol achieves strong adhesion to the automobile substrate. The hydrogen bond adsorption cross-linking structure is reversible and dynamic. When it is destroyed, it can be dynamically adjusted and reorganized under the stimulation of the external environment to restore the hydrogen bond cross-linking 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 terminal group. In the modified polyacrylic acid mixture obtained after polymerization, the amino group and the aldehyde group can easily condense and cross-link to form a high-temperature resistant dynamic cross-linking structure imine bond, thereby improving the high-temperature resistance of the coating. The improvement of high-temperature resistance reduces the adverse effects of cracking of the coating caused by ambient temperature and then causing the coating to fall off.

[0037] (2) The present invention is based on the principle of molecular bionics, and realizes the strong adhesion function of water-based automotive coatings by introducing the strong adhesion functional group of catechol into acrylic acid. However, the six carbon atoms of the benzene ring structure in catechol are interconnected by covalent bonds to form 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, so that the benzene ring has a stable conjugated system. This conjugated system and planar structure make the benzene ring more difficult to bend or twist in space, thereby enhancing rigidity. The increase in rigidity easily causes the coating to crack or peel under the action of external force, 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. Since the flexible monomer contains a longer alkyl chain after polymerization, it can increase the interchain distance of the polymer and reduce the interaction force between molecules, so it has a larger free rotation space, thereby giving it flexibility, reducing the possibility of the coating being easily broken and peeled due to the excessive use of the rigid benzene ring structure in catechol, and assisting in improving the strong adhesion brought by the catechol structure. DETAILED DESCRIPTION

[0038] The technical solution of the present invention will be clearly and completely described below through the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

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

[0040] 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 were all purchased from Shanghai Bangao 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 were all purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0042] Preparation Example 1:

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

[0044] Add 1 mol of ethanolamine to a round-bottom flask, then add 400 mL of ether and mix and stir evenly. After the temperature of the round-bottom flask is cooled to 0°C, slowly add 1 mol of di-tert-butyl dicarbonate and mix and stir to form a reaction system. Heat the reaction system to 15°C and keep it warm for 20 hours. After the reaction is completed, wash the product with deionized water, then extract it with ethyl acetate, dry it and rotary evaporate it to obtain N-Boc-ethanolamine.

[0045] Preparation Example 2:

[0046] The preparation method of N-Boc-ethanolamine specifically comprises the following process:

[0047] Add 1 mol of ethanolamine to a round-bottom flask, then add 400 mL of ether and mix and stir evenly. After the temperature of the round-bottom flask is cooled to 2°C, slowly add 1.5 mol of di-tert-butyl dicarbonate and mix and stir to form a reaction system. Heat the reaction system to 20°C and keep it warm for 21 hours. After the reaction is completed, wash the product with deionized water, then extract it with ethyl acetate, and dry and rotary evaporate to obtain N-Boc-ethanolamine.

[0048] Preparation Example 3:

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

[0050] Add 1 mol of 3-aminopropanol to a round-bottom flask, then add 400 mL of ether and mix and stir evenly. After the temperature of the round-bottom flask is cooled to 5°C, slowly add 2 mol of di-tert-butyl dicarbonate and mix and stir to form a reaction system. Heat the reaction system to 20°C and keep it warm for 22 hours. After the reaction is completed, wash the product with deionized water, then extract it with ethyl acetate, dry it and rotary evaporate it to obtain N-Boc-3-aminopropanol.

[0051] Preparation Example 4:

[0052] The preparation method of levodopa-modified acrylic acid with amino terminal groups specifically comprises the following steps:

[0053] Weigh 1 mol of acrylic acid, 1 mol of 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride and 1 mol of 1-hydroxybenzotriazole, mix and place in a flask, then add 1L of anhydrous dichloromethane to form a reaction system, control the temperature of the reaction system at 20°C, and stir at a speed of 100r / min for 10 minutes to obtain an activation solution. After the activation is completed, add 1.5 mol of levodopa to the activation solution and stir for 15 hours at a temperature of 20°C. After the reaction is completed, remove the solvent by rotary evaporator, add ethyl acetate to extract to obtain an organic phase, rinse the organic phase with deionized water, dry it with anhydrous sodium sulfate, and then remove ethyl acetate by rotary evaporator to obtain levodopa-modified acrylic acid.

[0054] 100 g of levodopa-modified acrylic acid, 100 g of N-Boc-ethanolamine obtained in Preparation Example 1 and 300 g of anhydrous dichloromethane were mixed and stirred to form a reaction solution, and then 35 g of concentrated sulfuric acid was carefully added and heated to 80° C. and reacted for 6 hours. After the reaction was completed, N-Boc-levodopa-modified acrylic acid was obtained by vacuum distillation.

[0055] 100 g of N-Boc-levodopa modified propylene and 500 g of methanol solution were mixed and stirred evenly, and 200 g of hydrochloric acid solution with a molar concentration of 1 mol / L was slowly added to the methanol solution of N-Boc-levodopa modified propylene and stirred for 2 hours. After stirring, the hydrochloric acid solution was neutralized, and then the methanol was removed by reduced pressure distillation to obtain levodopa modified acrylic acid with an amino terminal group.

[0056] Preparation Example 5:

[0057] The preparation method of levodopa-modified acrylic acid with amino terminal groups specifically comprises the following steps:

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

[0059] 100 g of levodopa-modified acrylic acid, 110 g of N-Boc-ethanolamine obtained in Preparation Example 1 and 300 g of anhydrous dichloromethane were mixed and stirred to form a reaction solution, and then 35.7 g of concentrated sulfuric acid was carefully added and heated to 80° C. and reacted for 6 hours. After the reaction was completed, N-Boc-levodopa-modified acrylic acid was obtained by vacuum distillation.

[0060] 100 g of N-Boc-levodopa modified propylene and 600 g of methanol solution were mixed and stirred evenly, and 200 g of hydrochloric acid solution with a molar concentration of 1 mol / L was slowly added to the methanol solution of N-Boc-levodopa modified propylene and stirred for 2 hours. After the stirring was completed, the hydrochloric acid solution was neutralized, and then the methanol was removed by reduced pressure distillation to obtain levodopa modified acrylic acid with an amino terminal group.

[0061] Preparation Example 6:

[0062] The preparation method of levodopa-modified acrylic acid with amino terminal groups specifically comprises the following steps:

[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 in a flask, then add 1L of anhydrous dichloromethane to form a reaction system, control the temperature of the reaction system at 22°C, and stir at a speed of 140r / min for 14 minutes to obtain an activation solution. After the activation is completed, add 1.7 mol of levodopa to the activation solution and stir for 17 hours at a temperature of 22°C. After the reaction is completed, remove the solvent by rotary evaporator, add ethyl acetate to extract to obtain an organic phase, rinse the organic phase with deionized water, dry it with anhydrous sodium sulfate, and then remove ethyl acetate by rotary evaporator to obtain levodopa-modified acrylic acid.

[0064] 100 g of levodopa-modified acrylic acid, 120 g of N-Boc-ethanolamine obtained in Preparation Example 2 and 400 g of anhydrous dichloromethane were mixed and stirred to form a reaction solution, and then 49.6 g of concentrated sulfuric acid was carefully added and heated to 90° C. and reacted for 7 hours. After the reaction was completed, N-Boc-levodopa-modified acrylic acid was obtained by vacuum distillation.

[0065] 100 g of N-Boc-levodopa modified propylene and 600 g of methanol solution were mixed and stirred evenly, and 250 g of hydrochloric acid solution with a molar concentration of 1 mol / L was slowly added to the methanol solution of N-Boc-levodopa modified propylene and stirred for 2.5 hours. After stirring, the hydrochloric acid solution was neutralized, and then the methanol was removed by reduced pressure distillation to obtain levodopa modified acrylic acid with an amino terminal group.

[0066] Preparation Example 7:

[0067] The preparation method of levodopa-modified acrylic acid with amino terminal groups specifically comprises the following steps:

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

[0069] 100 g of levodopa-modified acrylic acid, 130 g of N-Boc-ethanolamine obtained in Preparation Example 2 and 400 g of anhydrous dichloromethane were mixed and stirred to form a reaction solution, and then 56.7 g of concentrated sulfuric acid was carefully added and heated to 100° C. for 7 hours. After the reaction was completed, N-Boc-levodopa-modified acrylic acid was obtained by vacuum distillation.

[0070] 100 g of N-Boc-levodopa modified propylene and 700 g of methanol solution were mixed and stirred evenly, and 250 g of trifluoroacetic acid solution with a molar concentration of 1 mol / L was slowly added to the methanol solution of N-Boc-levodopa modified propylene and stirred for 2.5 hours. After stirring, the hydrochloric acid solution was neutralized, and then the methanol was removed by reduced pressure distillation to obtain levodopa modified acrylic acid with an amino terminal group.

[0071] Preparation Example 8:

[0072] The preparation method of levodopa-modified acrylic acid with amino terminal groups specifically comprises the following steps:

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

[0074] 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 were mixed and stirred to form a reaction solution, and then 66.6 g of concentrated sulfuric acid was carefully added and heated to 100° C. for 8 hours. After the reaction was completed, N-Boc-levodopa-modified acrylic acid was obtained by vacuum distillation.

[0075] 100 g of N-Boc-levodopa-modified propylene and 700 g of methanol solution were mixed and stirred evenly, and 300 g of trifluoroacetic acid solution with a molar concentration of 1 mol / L was slowly added to the methanol solution of N-Boc-levodopa-modified propylene and stirred for 3 hours. After stirring, the hydrochloric acid solution was neutralized, and then the methanol was removed by reduced pressure distillation to obtain levodopa-modified acrylic acid with an amino terminal group.

[0076] Preparation Example 9:

[0077] The preparation method of levodopa-modified acrylic acid with amino terminal groups specifically comprises the following steps:

[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 in a flask, then add 1L of anhydrous dichloromethane to form a reaction system, control the temperature of the reaction system at 25°C, and stir and activate at a speed of 200r / min for 20 minutes to obtain an activation solution. After the activation is completed, add 2 mol of levodopa to the activation solution and stir and react at a temperature of 25°C for 20 hours. After the reaction is completed, remove the solvent by rotary evaporator, add ethyl acetate to extract to obtain an organic phase, rinse the organic phase with deionized water, dry it with anhydrous sodium sulfate, and then remove ethyl acetate by rotary evaporator to obtain levodopa-modified acrylic acid.

[0079] 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 were mixed and stirred to form a reaction solution, and then 75 g of concentrated sulfuric acid was carefully added and heated to 110° C. and reacted for 8 hours. After the reaction was completed, N-Boc-levodopa-modified acrylic acid was obtained by vacuum distillation.

[0080] 100 g of N-Boc-levodopa modified propylene and 800 g of methanol solution were mixed and stirred evenly, and 300 g of trifluoroacetic acid solution with a molar concentration of 1 mol / L was slowly added to the methanol solution of N-Boc-levodopa modified propylene and stirred for 3 hours. After stirring, the hydrochloric acid solution was neutralized, and then the methanol was removed by reduced pressure distillation to obtain levodopa modified acrylic acid with an amino terminal group.

[0081] Preparation Example 10:

[0082] The preparation method of dopamine-modified acrylic acid with amino terminal groups specifically comprises the following steps:

[0083] The levodopa in Preparation Example 9 was replaced by dopamine hydrochloride, and the other conditions were the same as those in Preparation Example 9.

[0084] Preparation Example 11:

[0085] The preparation method of levodopa-modified acrylic acid with amino terminal groups specifically comprises the following steps:

[0086] The trifluoroacetic acid in Preparation Example 9 was replaced by acetic acid, and the other conditions were the same as those in Preparation Example 9.

[0087] Embodiment 1:

[0088] A method for preparing a water-based coating with strong adhesion specifically comprises the following steps:

[0089] Take 50g of the amino-terminated levodopa-modified acrylic acid obtained in Preparation Example 4, 25g of methyl acrylate, 5g of 2-methylacrolein and 150g of DMF (N,N-dimethylformamide), mix and stir together, then add 0.4g of 2,2'-azobisisobutylamidine dihydrochloride and mix and stir evenly, then heat to 70°C and react for 3h to obtain a modified polyacrylic acid mixture.

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

[0091] Embodiment 2:

[0092] A method for preparing a water-based coating with strong adhesion specifically comprises the following steps:

[0093] Take 50g of the amino-terminated levodopa-modified acrylic acid obtained in Preparation Example 5, 26g of methyl acrylate, 6g of 2-methylacrolein and 160g of DMF (N,N-dimethylformamide), mix and stir together, then add 0.57g of 2,2'-azobisisobutylamidine dihydrochloride and mix and stir evenly, then heat to 72°C and react for 3h to obtain a modified polyacrylic acid mixture.

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

[0095] Embodiment 3:

[0096] A method for preparing a water-based coating with strong adhesion specifically comprises the following steps:

[0097] Take 50g of the amino-terminal levodopa-modified acrylic acid obtained in Preparation Example 6, 27g of ethyl acrylate, 7g of 2-methylacrolein and 170g of DMF (N,N-dimethylformamide), mix and stir together, then add 0.67g of 2,2'-azobisisobutylamidine dihydrochloride and mix and stir evenly, then heat to 74°C and react for 3.5h to obtain a modified polyacrylic acid mixture.

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

[0099] Embodiment 4:

[0100] A method for preparing a water-based coating with strong adhesion specifically comprises the following steps:

[0101] Take 50g of the amino-terminal levodopa-modified acrylic acid obtained in Preparation Example 7, 28g of butyl acrylate, 8g of acrolein and 180g of DMSO (dimethyl sulfoxide), mix and stir together, then add 0.69g of azobisisobutylimidazoline hydrochloride and mix and stir evenly, then heat to 76°C and react for 3.5h to obtain a modified polyacrylic acid mixture.

[0102] 19 parts by weight of a modified polyacrylic acid mixture, 0.2 parts by weight of a polyester modified polydimethylsiloxane solution, 0.8 parts by weight of a composite emulsifier (a mixture of 0.4 parts by weight of EL-10 and 0.4 parts by weight of sodium dicyclohexyl sulfosuccinate) and 10 parts by weight of deionized water were mixed, and stirred and emulsified at a stirring speed of 500 r / min for 30 minutes to obtain a water-based coating with strong adhesion.

[0103] Embodiment 5:

[0104] A method for preparing a water-based coating with strong adhesion specifically comprises the following steps:

[0105] Take 50g of the amino-terminated levodopa-modified acrylic acid obtained in Preparation Example 8, 29g of vinyl acetate, 9g of acrolein and 190g of DMSO (dimethyl sulfoxide), mix and stir together, then add 0.88g of azobisisobutylimidazoline hydrochloride and mix and stir evenly, then heat to 78°C and react for 4h to obtain a modified polyacrylic acid mixture.

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

[0107] Embodiment 6:

[0108] A method for preparing a water-based coating with strong adhesion specifically comprises the following steps:

[0109] Take 50g of the L-DOPA-modified acrylic acid with an amino terminal obtained in Preparation Example 9, 30g of vinyl acetate, 30g of acrolein and 2000g of DMSO (dimethyl sulfoxide), mix and stir together, then add 1.08g of azobisisobutylimidazoline hydrochloride and mix and stir evenly, then heat to 80°C and react for 4h to obtain a modified polyacrylic acid mixture.

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

[0111] Comparative Example 1:

[0112] A method for preparing a water-based coating with strong adhesion specifically comprises the following steps:

[0113] The levodopa-modified acrylic acid with an amino terminal in Example 6 was replaced with the dopamine-modified acrylic acid with an amino terminal obtained in Preparation Example 10, and the other conditions remained the same as in Example 6.

[0114] Comparative Example 2:

[0115] A method for preparing a water-based coating with strong adhesion specifically comprises the following steps:

[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] The tinplate surface 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 coating obtained in Examples 1 to 6 and Comparative Examples 1 to 6 was applied to the tinplate to form a coating film, and then placed at a high temperature of 200°C for 4 hours. After the high-temperature treatment, it was cooled to room temperature and the coating film was observed for cracking and shedding. Then, the adhesion grade was tested according to the "GB / T 9286-2021 Paint and Varnish Cross-cut Test", and the results are shown in Table 2 below:

[0134] Table 2

[0135] Sources Surface coating film Adhesion grade Example 1 A few cracks and a little falling off Level 1 Example 2 The surface is intact, without damage or shedding Level 0 Example 3 The surface is intact, without damage or shedding Level 0 Example 4 The surface is intact, without damage or shedding Level 0 Example 5 The surface is intact, without damage or shedding Level 0 Example 6 The surface is intact, without damage or shedding Level 0 Comparative Example 1 The surface is bubbling and cracking, with a lot of falling off Level 4 Comparative Example 2 The surface is bubbling and cracking, with a little shedding Level 3 Comparative Example 3 The surface is bubbling and cracking, with a lot of falling off Level 4 Comparative Example 4 The surface is bubbling and cracking, with a lot of falling off Level 4 Comparative Example 5 The surface is bubbling and cracking, with a little shedding Level 3 Comparative Example 6 The surface is bubbling and cracking, with a little shedding Level 3

[0136] The tinplate surface 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 to the tinplate to form a coating film, and then scratches were made on the surface of the coating film with a pencil. The coating film was placed in a hot air environment at room temperature (25° C.) and 50° C., respectively, and the scratch repair time was recorded. The results are shown in Table 3:

[0137] Table 3

[0138]

[0139] From the experimental results in Tables 1 to 3 above, we can see that:

[0140] (1) The present invention introduces levodopa with catechol into an acrylic acid monomer, and then introduces an amino structure and an aldehyde structure into a modified polyacrylic acid polymer. The polymer network structure formed by the strong hydrogen bond crosslinking and metal coordination of the catechol derivatives can achieve strong adhesion to the automobile substrate. The amino and aldehyde groups on the modified polyacrylic acid polymer are easily condensed and crosslinked at room temperature or a slightly higher temperature environment to form a dynamic imine structure, thereby improving the high temperature resistance of the coating formed after the coating is applied, achieving the functions of self-repairing and strong adhesion, and the increase in temperature has a promoting effect on the self-repairing performance.

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

[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 conditions are not sufficient to completely remove the Boc protecting group, so the amino functional group is released less, and the number of dynamic imine bonds formed is low, resulting in poor high temperature resistance, which is 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 chain is restricted, and the formed chain conformation is more compact and regular, which reduces the free movement between the chains and increases the rigidity. When damaged by external forces, the coating film is prone to brittle cracking, 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 induce carbon-carbon double bond polymerization, due to their strong oxidizing properties, the catechol structure is easily oxidized prematurely and loses the active structure of catechol. Therefore, it is difficult to achieve self-repair after being scratched by external force.

[0145] The above-described embodiments provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected.

Claims

1. A method for preparing a water-based coating with strong adhesion, characterized in that: The preparation method comprises the following steps: After the catechol-modified acrylic acid with amino terminal group, flexible ester monomer, aldehyde olefin and organic solvent are mixed and dissolved in a mass ratio of 1:0.5-0.6:0.1-0.2:3-4, 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, stirred and emulsified in a weight ratio of 10-25:0.1-0.3:0.5-1:6-13 to obtain the water-based coating with strong adhesion.

2. The method for preparing a water-based coating with strong adhesion according to claim 1, characterized in that: 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 1:2-2.5, and anhydrous dichloromethane is added and stirred to activate 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.-25° C. for 15 h-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 1:1-1.5:3-5 to form a reaction solution, and the reaction solution is mixed with concentrated sulfuric acid in a mass ratio of 1:0.07-0.1 and reacted in a temperature environment of 80°C-110°C for 6h-8h to obtain N-Boc-catechol-modified acrylic acid; The N-Boc-catechol-modified acrylic acid, acid solution and 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 with amino terminal groups.

3. The method for preparing a strong adhesion water-based coating according to claim 2, 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 1-1.5:

1.

4. The method for preparing a strong adhesion water-based coating according to claim 2, characterized in that: The catechol derivative includes levodopa, and the molar ratio of the catechol derivative to acrylic acid is 1.5-2:

1.

5. The method for preparing a water-based coating with strong adhesion according to claim 2, 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.

6. 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.

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

8. 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.

9. 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.

10. A strong adhesion water-based coating prepared by the method for preparing a strong adhesion water-based coating according to any one of claims 1 to 9.

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