Preparation method of self-repairing coating based on dynamic ester bonds

Abstract

The invention discloses a preparation method of a self-repairing coating based on a dynamic ester bond, and belongs to the field of self-repairing coating materials, the dynamic ester bond is introduced into epoxy resin, self-repairing is realized through reversible reaction of the dynamic bond, waterborne epoxy resin and a curing agent methylhexahydrophthalic anhydride react, and the self-repairing coating is prepared. Epoxy resin containing dynamic reversible ester bonds can be prepared under the catalytic condition of polyethylene glycol. The prepared dynamic ester bond epoxy resin coating is simple in synthesis process and rapid in reaction; the required raw materials are easy to obtain, the curing time is very short, the self-repairing condition is easy to achieve, and only heating is needed. According to the self-repairing coating material, a common epoxy resin coating has self-repairing performance, the service life of the common coating is prolonged, and resource waste caused by waste, aging and damage of the epoxy resin material is reduced.

Description

Technical Field

[0001] The present invention belongs to the field of self - healing coating materials, and particularly relates to a preparation method of a self - healing coating based on dynamic ester bonds. Background Art

[0002] Epoxy resin, as a highly valuable polymer material, is globally recognized for its excellent mechanical properties, chemical stability, and corrosion resistance. Such materials are mainly composed of epoxy groups and need to react with a curing agent (also known as a hardener) to form a stable and firm three - dimensional network structure. Due to this unique network structure, epoxy resin has excellent heat resistance, chemical corrosion resistance, and strong mechanical strength. Epoxy resin is widely used in many industries such as coatings, adhesives, sealants, and composite materials, and is one of the important pillars in the industrial field. However, epoxy resin belongs to thermosetting polymer materials and cannot be processed again once it is formed. Its aging products, waste products, and damaged products not only cause waste of resources but also bring difficulties in treatment.

[0003] In recent years, due to the requirements of social sustainable development, the demand for environmentally friendly materials has increased, and the research of repairable materials has become a major focus. Currently, popular repairable materials are generally divided into two categories: reversible covalent bonds and non - reversible covalent bonds. Due to the reversibility of covalent bonds, reversible cross - linked polymers generally have excellent self - healing properties and processability. However, because covalent bonds are relatively weak, the mechanical properties of the materials are usually not very good. Therefore, improving the performance of self - healing materials has become a difficult point.

[0004] A dynamic ester bond refers to an ester bond formed between an oxygen atom on a carbon atom and a hydroxyl group (-OH) in another molecule. This chemical bond is reversible and can break or form in different chemical environments. In some special chemical environments, such as in the presence of a catalyst or specific temperature and pressure conditions, these ester bonds can be hydrolyzed or alcoholyzed, causing the compound to decompose into its original components. This reversible property makes dynamic reversible ester bonds have important applications in fields such as materials science, drug preparation, and biochemistry.

[0005] Based on the above problems and background, the present invention introduces dynamic reversible ester bonds into epoxy resin, relies on the reversible reaction of dynamic bonds to achieve self - healing, combines the excellent properties of the two materials, and prepares a self - healing coating based on dynamic ester bonds. Summary of the Invention

[0006] The object of the present invention is to propose a preparation method of a self-healing coating based on dynamic ester bonds, which relies on the reversible reaction of dynamic ester bonds under heating conditions to achieve the breaking and reformation of chemical bonds, thereby realizing the self-healing function of the coating material. By introducing dynamic reversible ester bonds into epoxy resin and combining the excellent properties of the two materials, a coating material with the heat resistance, corrosion resistance, excellent mechanical properties, chemical stability and other advantages of epoxy resin, and at the same time having self-healing properties is prepared.

[0007] In order to achieve the above technical object, the present invention adopts the following technical solutions to achieve: The present invention is a preparation method of a self-healing coating based on dynamic ester bonds, which is prepared by a base material of waterborne epoxy resin, an acid anhydride curing agent and a catalyst material under heating conditions to obtain a self-healing coating containing dynamic ester bonds; relying on the reversible reaction of dynamic ester bonds under heating conditions to achieve the breaking and reformation of chemical bonds, thereby realizing the self-healing function of the coating material.

[0008] A preparation method of a self-healing coating based on dynamic ester bonds includes the following steps: Step 1, first calculate the mass of the experimental raw materials required for each formula, and use an electronic balance to weigh the experimental raw materials respectively according to the calculated values: epoxy resin, methylhexahydrophthalic anhydride, polyethylene glycol (PEG).

[0009] Step 2, stir and mix the waterborne epoxy resin and the acid anhydride curing agent evenly.

[0010] Step 3, add the catalyst polyethylene glycol (PEG), stir evenly and then add the defoaming agent, and place it on a magnetic stirrer to stir and heat.

[0011] Step 4, wait until the solution gradually becomes transparent, continue to heat until the solution becomes viscous, adjust the temperature, stop heating but do not stop stirring when the solution cools to 60 °C, and wait for the bubbles to disappear to obtain the prepared coating material solution.

[0012] Step 5, coat the tinplate sample on an automatic film coater, and cure it in an electrothermal blast drying oven to obtain a tinplate sample coated with a self-healing coating; finally, conduct a series of characterization and analysis on the sample material.

[0013] The present invention comprehensively considers the excellent properties of epoxy resin and dynamic reversible ester bonds, and obtains a preparation method of a self-healing coating based on dynamic ester bonds by introducing dynamic reversible ester bonds into epoxy resin.

[0014] Specifically, in Step 1, the content of the waterborne epoxy resin is 25 g, and the content of the methylhexahydrophthalic anhydride is 10 g.

[0015] Specifically, the amount of polyethylene glycol added in step 3 is 1 g, and an antifoaming agent is added to reduce the bubbles in the solution. The magnetic stirrer is set at a rotation speed of 300 RPM. After reaching the preset temperature of 120 °C, it is heated for 30 minutes.

[0016] Specifically, the coating speed in step 5 is set at 1 cm / min, the curing temperature in the electrothermal blast drying oven is 130 °C, and the curing time is 6 h.

[0017] Specifically, the performance characterizations carried out in step 5 mainly include infrared spectrum analysis and differential scanning calorimetry (DSC); and electrochemical corrosion detection and self-healing performance comparison experiments are conducted.

[0018] The present invention has the following beneficial effects: The present invention is a preparation method of a self-healing coating based on dynamic ester bonds. The prepared coating material has good self-healing properties and good corrosion resistance. The synthesis process of the prepared dynamic ester bond epoxy resin coating is simple and the reaction is rapid; the required raw materials are easily obtained, the curing time is very short, and the self-healing conditions are relatively easy to achieve, only heating is required.

[0019] The present invention provides a preparation method of a self-healing coating based on dynamic ester bonds. This method obtains a self-healing coating based on dynamic ester bonds, which helps to enhance the service life of epoxy resin coating materials, reduces the waste of resources caused by the waste, aging and damage of epoxy resin materials, and meets the requirements of sustainable development and environmental protection. The self-healing coating material of the present invention can be applied to most occasions where epoxy resin coatings are used, providing a longer service life for the materials. The present invention provides a preparation method for studying self-healing coatings. Its synthesis process is simple, the reaction is rapid, the required raw materials are easily obtained, the curing time is very short, and the self-healing conditions (heating) are relatively easy to achieve. Description of the Drawings

[0020] Figure 1 It is an infrared spectrum diagram of an epoxy resin coating containing dynamic reversible ester bonds and waterborne epoxy resin.

[0021] Figure 2 It is a differential scanning calorimetry (DSC) diagram of a self-healing coating containing dynamic reversible ester bonds and waterborne epoxy resin.

[0022] Figure 3 It is a salt water treatment impedance diagram of the self-healing coating containing dynamic reversible ester bonds of the present invention.

[0023] Figure 4 It is a comparison diagram of the experimental effects before and after coating a self-healing coating and an epoxy resin coating on tinplate. Detailed Embodiments

[0024] The technical solutions of the present invention are described below through specific embodiments. It should be understood that one or more steps mentioned in the present invention do not exclude the existence of other methods and steps before and after the combined steps, or other methods and steps can be inserted between these explicitly mentioned steps. It should also be understood that these examples are only used to illustrate the present invention and not to limit the scope of the present invention. Unless otherwise specified, the numbers of the method steps are only for the purpose of identifying each method step, rather than limiting the arrangement order of each method or defining the scope of implementation of the present invention. The change or adjustment of their relative relationship can also be regarded as the scope in which the present invention can be implemented under the condition of no substantial change in technical content.

[0025] The experimental steps recorded in the present invention include: preparing an epoxy resin self-healing coating containing dynamic ester bonds by adding methylhexahydrophthalic anhydride and a catalyst polyethylene glycol to waterborne epoxy resin. First, weigh a certain amount of waterborne epoxy resin and the curing agent methylhexahydrophthalic anhydride. First add the waterborne epoxy resin to a beaker, and then add methylhexahydrophthalic anhydride, stir it evenly, then add an appropriate amount of the catalyst polyethylene glycol to the solution, stir it evenly and let it react, and then add a small amount of defoamer. Subsequently, place the solution on a magnetic stirrer and stir for 30 minutes at a rotation speed of 300 RPM, with a preset temperature of 120 °C. During this process, the solution gradually becomes transparent. Then, continue heating until the solution becomes viscous, adjust the set temperature to 60 °C, stop heating but do not stop stirring when the solution cools to this temperature, and wait for the bubbles in the solution to disappear to obtain the prepared self-healing coating material solution. Use an automatic film coating machine to evenly coat it on the surface of tinplate to obtain a tinplate sample with a self-healing coating. Finally, perform a series of characterization analyses. Example

[0026] This example provides a self-healing coating based on dynamic ester bonds, which is made by the following preparation method: A) Prepare the chemical supplies required for preparing the coating and configure the solution according to a certain ratio. Among them, the mass of the waterborne epoxy resin is 25 g, the mass of methylhexahydrophthalic anhydride is about 10 g, and the mass of polyethylene glycol is 1 g. Add them in sequence and stir to make a uniformly mixed solution, and then add 1 - 2 drops of defoamer to remove the bubbles in the solution.

[0027] B) Then place it on a magnetic stirrer and stir for 30 minutes at a rotation speed of 300 RPM, set the temperature to 120 °C, wait until the solution becomes transparent and continue heating until it becomes viscous, and then cool the solution to 60 °C, and stop stirring after the bubbles in the solution disappear.

[0028] C) Coat the prepared uniform solution on the surface of tinplate with an automatic film coating machine, set the coating speed to 1 cm / min, and then place the tinplate in an electrothermal blast drying oven and cure it at 130 °C for 6 h, and take it out after cooling to room temperature.

[0029] D) Finally, a series of characterization analyses were carried out on the coating material of the tinplate sample. Example

[0030] The specific steps for preparing an epoxy resin coating without dynamic ester bonds provided in this example are as follows: A) Prepare the chemical supplies required for preparing the coating and configure the solution according to a certain ratio. Among them, the mass of the waterborne epoxy resin is 25 g, the mass of polyethylene glycol is 1 g, and methylhexahydrophthalic anhydride is not added. Add them in sequence and stir to make a uniformly mixed solution, and then add 1 - 2 drops of defoamer to remove the bubbles in the solution.

[0031] B) Then place it on a magnetic stirrer and stir for 30 minutes at a rotation speed of 300 RPM. Set the temperature to 120 °C. Wait until the solution becomes transparent and continue heating until it becomes viscous. Then cool the solution to 60 °C and stop stirring after the bubbles in the solution disappear.

[0032] C) Coat the prepared uniform solution on the surface of the tinplate with an automatic film coater. Set the film coating speed to 1 cm / min. Then place the tinplate in an electrothermal blast drying oven and cure it at 130 °C for 6 h. Take it out after cooling to room temperature.

[0033] D) Finally, a series of characterization analyses were carried out on the coating material of the tinplate sample.

[0034] Characterization analysis Infrared spectroscopy analysis: Infrared spectroscopy analysis was carried out on the epoxy resin coating containing dynamic reversible ester bonds and the general epoxy resin coating. From Figure 1 the infrared spectrum, it can be seen that the peak of the waterborne epoxy resin at 1700 cm-1 is very small and almost non-existent. More are the peaks belonging to -OH and the C-H bonds on the benzene ring. However, in the modified epoxy resin after the reaction, a peak at 1700 cm-1 belonging to C=O appears and has a relatively large content. It can be known that the ester bond was successfully synthesized in this reaction. It shows that this formulation is feasible and can achieve good results. The dynamic ester bond was successfully introduced into the epoxy resin, and an epoxy resin self-healing coating containing dynamic ester bonds was synthesized.

[0035] Differential scanning calorimetry analysis: The epoxy resin coating containing dynamic reversible ester bonds and the general epoxy resin coating obtained were subjected to differential scanning calorimetry analysis to deeply evaluate their thermal properties through differential scanning calorimetry, such as Figure 2As shown, there is no obvious phase change in the waterborne epoxy resin during the heating process. However, for the prepared epoxy resin containing dynamic ester bonds, it can be clearly seen that there is an obvious morphological change at 120 °C, indicating that the dynamic reversible ester bonds undergo a reversible reaction at this temperature. From this, we can infer that the best reaction temperature should be 120 °C, at which the synthesis of ester bonds is relatively fast.

[0036] Electrochemical corrosion detection and analysis: By measuring the corresponding current and potential changes on the metal surface, the corrosion condition of the metal is evaluated. The research method is the electrochemical impedance method. Figure 3 As can be seen, the impedance is relatively small on the first and fifth days of salt water immersion, indicating that the film is not corroded, which shows that the anti-corrosion effect of the film is relatively good. However, it is observed that when the salt water immersion lasts for seven days, it can be seen that the impedance of the material increases significantly, indicating that the film has been corroded and the performance of the material has changed. Therefore, the epoxy resin coating containing dynamic reversible ester bonds has a good anti-corrosion effect.

[0037] Experimental comparison and analysis of self-healing performance: Two tinplates are selected, one coated with a self-healing coating containing dynamic ester bonds and the other coated with an epoxy resin coating. Simple scratch treatment is carried out on their surfaces under the same conditions, such as Figure 4 (a) and Figure 4 (c) show the surface conditions of the two coatings after scratch treatment (the former is a sample of the self-healing coating containing dynamic ester bonds, and the latter is a sample of the epoxy resin coating), and a control experiment is carried out under heat treatment. The film containing scratches can generate self-healing when heated at a specific temperature. After DSC test and analysis, we know that the optimal temperature for transesterification is 120 °C. Therefore, the two coated samples containing scratches are taken out after being heated and cured at 120 °C for 30 min in a blast dryer. The self-healing effect of the treated coatings is as shown in Figure 4 (b) and Figure 4 (d). From Figure 4 (a) to Figure 4 (b), it can be clearly seen that after 30 min of heating and re-curing at 120 °C, the scratches on the film all disappear, indicating that the self-healing performance of this coating is good and the reaction is rapid. However, the scratches on the surface of the general epoxy resin coating are still relatively clear after treatment, indicating that this coating has no self-healing performance. In summary, the self-healing coating containing dynamic ester bonds has good self-healing performance and can quickly react to repair the material under heating conditions.

[0038] The above description of the specific exemplary embodiments of the present invention is for the purpose of illustration and exemplification. The present invention is not limited to the above embodiments. Without departing from the essence of the present invention, any obvious improvements, substitutions or variations that those skilled in the art can make all belong to the protection scope of the present invention. The scope of the present invention is intended to be defined by the claims and their equivalents.

Claims

1. A self-healing coating based on dynamic ester bonds, characterized in that: It is prepared from base water-based epoxy resin, anhydride curing agent and catalyst material under heating conditions; it relies on the reversible reaction of dynamic ester bonds under heating conditions (120°C) to achieve the breaking and reforming of chemical bonds, thereby realizing the self-healing function of the coating material.

2. The self-healing coating material based on dynamic ester bonds according to claim 1, characterized in that: The acid anhydride curing agent is methylhexahydrophthalic anhydride, and the catalyst is polyethylene glycol.

3. A method for preparing a dynamic ester bond self-repairing coating according to claim 1, characterized in that: The following steps are involved: Step 1, stirring and mixing the waterborne epoxy resin and the acid anhydride curing agent; Step 2, adding the catalyst polyethylene glycol, stirring evenly and then adding the defoamer, placing it on a magnetic stirrer for stirring and heating; Step 3, when the solution gradually becomes transparent, continue heating until the solution becomes viscous, adjust the temperature, stop heating but do not stop stirring when the solution cools to 60°C, and wait until the bubbles disappear to obtain the prepared coating material solution; Step 4, coating the tinplate on an automatic coating machine, and putting it into an electric hot air drying furnace for curing, and finally obtaining a tinplate sample coated with a self-repairing coating.

4. The method for preparing a self-repairing coating based on a dynamic ester bond according to claim 3, characterized in that: The content of the waterborne epoxy resin in step 1 is 25 g, and the anhydride curing agent is methylhexahydrophthalic anhydride, and its content is 10 g.

5. The method for preparing a self-repairing coating based on a dynamic ester bond according to claim 3, characterized in that: In step 2, the amount of polyethylene glycol added was 1 g, and a defoamer was added to reduce bubbles in the solution. The magnetic stirrer was set to a speed of 300 RPM, and after reaching a preset temperature of 120° C., heating was performed for 30 minutes.

6. The method for preparing a self-repairing coating based on a dynamic ester bond according to claim 3, characterized in that: The curing temperature in step 4 is 130° C. and the curing time is 6 h.

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