PMMA (polymethyl methacrylate) microcapsule and preparation method thereof as well as dual self-repairing water-based paint and preparation method thereof
By incorporating PMMA microcapsules into the coating, combined with lightly branched hydroxysaturated polyester aqueous resin, a dual self-repaired water-based coating is formed, which solves the problem of shear force and difficulty in repairing traditional coatings during long-term use, and realizes the problem of shear force and difficulty in repairing. Intelligent repair and long-term self-repair performance.
Patent Information
- Application Number
- CN202311045874.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-08-18
- Publication Date
- 2025-02-21
AI Technical Summary
Traditional coatings are prone to shear forces caused by pores, cracks and internal residual stresses during long-term use, resulting in peeling of coatings and substrates, and traditional repair methods are difficult to fully restore small-depth defects and damage.
PMMA microcapsules are used, polymethyl methacrylate (PMMA) is used as the capsule wall, sodium dodecylbenzenesulfonate is coated to increase hydrophilicity, isofluron diisocyanate, etc. are used as the capsule core, and are stirred and emulsified. Microcapsules were prepared in the same steps and built into a lightly branched hydroxysaturated polyester aqueous resin to form a dual self-healing aqueous coating.
This coating can intelligently select repair solutions according to changes in external forces, and achieve dual self-healing through the cross-linking reaction between the capsule wall and the capsule core of the microcapsule, extend the service life of the coating, reduce VOC emissions, and is simple in process and low in cost, suitable for large-scale Production.
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Abstract
Description
Technical Field
[0001] The invention relates to the field of coatings, and in particular to a PMMA microcapsule and a preparation method thereof, and a dual self-repairing water-based coating and a preparation method thereof. Background Art
[0002] Paint is a chemical product made of resin or other materials, with or without pigment. When applied to the surface of an object, the paint can dry into a film, isolating the surface of the coated object from the surrounding medium, thus protecting and decorating the coated object.
[0003] Due to improper construction, wrong choice of coating or exposure to unexpected environment, the physical and mechanical integrity of the coating will be affected in the long-term use, such as temperature, ultraviolet radiation and mechanical action (scratches or cracks), resulting in pores and cracks. The residual stress inside the coating will also produce cracks, which may cause shear force and eventually lead to peeling of the coating and substrate. Traditional repair methods, such as welding and patching, cannot completely restore the losses caused by microcracks because it is difficult to detect very small deep defects and damage inside the coating. In this regard, reference can be made to DNA repair in organisms and macroscopic levels, such as wound and bone healing. Self-healing coatings, a new type of coating with automatic healing ability, have developed rapidly in recent years. In the past 20 years, self-healing materials have been a huge research field. The ability of materials to self-repair effectively extends the service life of materials, prevents further expansion of the scope of trauma, and especially in extreme cases, avoids major accidents such as leakage and collapse. The material can automatically repair the scratched, abraded or damaged surface in time, maintain its high decorative beauty and gloss, and extend the service life of the coating. For built-in self-healing materials, microencapsulation is the easiest way to achieve industrialization. Microcapsules are small particles in the micrometer range that encapsulate liquid healing agents (capsule cores) in different types of polymers (capsule walls). When the coating is damaged, it can sense the damage and respond to the damage by releasing the capsule core material. Therefore, we choose built-in microcapsules to prepare self-healing water-based coatings. Summary of the invention
[0004] In view of the shortcomings of the prior art, one of the purposes of the present invention is to provide a microcapsule that can spontaneously make a repair response according to the change of external force and a preparation method thereof. The second purpose of the present invention is to provide a dual self-repairing water-based coating and a preparation method thereof. The specific scheme is as follows: In a first aspect, the present invention provides a PMMA microcapsule, which consists of a capsule wall and a capsule core. The capsule wall is polymethyl methacrylate, and the polymethyl methacrylate is coated with sodium dodecylbenzene sulfonate and has hydrophilicity; the capsule core is aliphatic polyisocyanate.
[0005] Furthermore, the aliphatic polyisocyanate is one or more mixtures of isophorone diisocyanate, hexamethylene diisocyanate, hydrogenated diphenylmethane diisocyanate and derivatives thereof.
[0006] In a second aspect, the present invention provides a method for preparing the PMMA microcapsules described in the first aspect, characterized in that it comprises the following steps: (1) Add 40-60 parts by mass of aliphatic polyisocyanate to 40-60 parts by mass of an organic solvent, butyl acetate, and stir at a speed of 800-1000 r / min for 10-15 min to obtain an aliphatic polyisocyanate solution A; (2) Slowly adding 75 to 80 parts by weight of polymethyl methacrylate to 20 to 25 parts by weight of the solution A, stirring at 2000 to 2500 r / min for 12 to 24 hours in an environment of 70 to 80° C. to obtain a mixed solution B of aliphatic polyisocyanate and polymethyl methacrylate; ⑶ Add 15-18 parts by weight of the mixed solution B and 2-5 parts by weight of the emulsifier to 80 parts by weight of deionized water, stir at 1200-1500 r / min for 4-6 hours in an environment of 85° C., and obtain PMMA microcapsules by centrifugation, washing, and drying; Furthermore, the emulsifier is one or more mixed emulsifiers selected from OP-10, sodium dodecyl sulfate (SDS) and sodium dodecylbenzene sulfonate (DBS).
[0007] In a third aspect, the present invention provides a dual self-repairing water-based coating, characterized in that it comprises the following components in parts by mass: 15~35 parts of PMMA microcapsules, 60~80 parts of slightly branched hydroxyl saturated polyester water-based resin, 2~4 parts of leveling agent, 2~4 parts of thickener; The PMMA microcapsule is the PMMA microcapsule provided by the first aspect of the present invention or the PMMA microcapsule prepared by the second aspect; The slightly branched hydroxyl saturated polyester water-based resin is a polycondensate of a polyol and a polyacid, and is characterized in that the slightly branched hydroxyl saturated polyester water-based resin is prepared according to the following method: 41-44 parts by weight of dehydrated ricinoleic acid, 33-36 parts by weight of phthalic anhydride, 7.9-8.1 parts by weight of isophthalic acid, 28-28.2 parts by weight of trimethylolpropane, 13-15 parts by weight of dimethylolpropionic acid, 0.12-0.14 parts by weight of catalyst lithium hydroxide, 0.12-0.14 parts by weight of antioxidant 3,5-dibutyl-4-hydroxybenzoic acid, and 13-15 parts by weight of reflux xylene are added to a reaction bottle equipped with a stirrer, a thermometer, a water separator and a nitrogen conduit; heated to 140-150° C., stirred, set the speed to 600-800 r / min, and kept warm for about 0.5-1 hour; heated to 160-1 70℃, keep warm for about 1~2 hours; heat to 180~185℃, keep warm for about 1~2 hours; when the water output becomes slow, continue to heat to 200~210℃, measure the acid value after 1 hour; control the acid value to 50~55mgKOH / g (resin), evaporate the solvent, cool to 80℃, add 18~21 parts by weight of ethylene glycol monobutyl ether, set the speed to 600~800r / min, stir for 1 hour, continue to cool to 60℃, add 10~12 parts by weight of triethylamine for neutralization, set the speed to 700~800r / min, and continue to stir for 0.5~1 hour; add 85~90 parts by weight of distilled water, filter to obtain a slightly branched hydroxyl saturated polyester water-based resin.
[0008] In a fourth aspect, according to the dual self-repairing water-based coating of the third aspect, it is also characterized in that: ⑴ According to the standard GB∕T 1732-2020, the impact resistance is tested. The PMMA capsule wall is 40cm, the slightly branched hydroxyl saturated polyester water-based resin is 30cm, and the cross-linked reaction product of the PMMA microcapsule core and the water-based resin is 50cm; ⑵ According to the standard GB / T 6739-2006 test pencil hardness, PMMA capsule wall is H, slightly branched hydroxyl saturated polyester water-based resin is HB, PMMA microcapsule core and water-based resin cross-linking reaction product is 2H; The PMMA microcapsule wall has an impact resistance of 40 cm, which is slightly greater than the impact resistance of 30 cm of the slightly branched hydroxyl saturated polyester water-based resin, to ensure that external impact forces of different sizes cause different degrees of damage to the components of the coating, thereby playing a dual repair function; The capsule wall pencil hardness of the PMMA microcapsule is H, which needs to be slightly greater than the pencil hardness HB of the lightly branched hydroxyl saturated polyester water-based resin, to ensure that external scratches of different sizes cause different degrees of damage to the components of the coating, thereby playing a dual repair function.
[0009] Furthermore, the catalyst is lithium hydroxide.
[0010] Furthermore, the antioxidant is 3,5-dibutyl-4-hydroxybenzoic acid.
[0011] Furthermore, the leveling agent is aralkyl modified polydimethylsiloxane.
[0012] Furthermore, the thickener is polyethylene wax.
[0013] In a fifth aspect, the present invention provides a method for preparing the dual self-repairing water-based coating according to the third aspect, characterized in that it comprises the following steps: 60-80 parts of lightly branched hydroxyl saturated polyester water-based resin and 2-4 parts of leveling agent were mixed at a speed of 700 r / min for 10 minutes, and then 2-4 parts of thickener were slowly added and dispersed at 1000 r / min for 20 minutes. Then, 15-35 parts of PMMA microcapsules were added and dispersed at 400-500 r / min for 5 minutes to obtain a double self-healing water-based coating.
[0014] Compared with the prior art, the present invention has the following advantages: 1. The prepared lightly branched hydroxyl saturated polyester water-based resin has certain self-drying properties and contains hydroxyl groups, which can continue to react with isocyanate to form a more compact paint film. The water-based resin has greater elasticity and good impact resistance and scratch resistance, and can withstand low-intensity external collisions, extrusions, and scratches. The paint film can rely on the resilience of the resin to absorb external stress in a short time, restore deformation and be repaired, and the capsule wall impact resistance and pencil hardness of PMMA microcapsules are higher than those of water-based resins. If the external force exceeds the bearing capacity of the water-based resin, the coating is severely damaged. At this time, the PMMA microcapsules are broken, and the aliphatic polyisocyanate in the capsule wall oozes out and cross-links with the water-based resin, just like the healing of cells, completing the second self-repair and maintaining the integrity of the coating, that is, the water-based resin and microcapsule wall provided by the present invention are innovatively designed to be impact-resistant and hardness-differentiated, so the dual self-repairing water-based coating provided by the present invention can be intelligently selected according to the different external destructive forces. The repair scheme allows the product to have a longer-lasting and lasting self-repairing performance.
[0015] 2. Using PMMA microcapsules as a two-component coating does not require mixing and dispersing the two components before use, making construction more convenient and extending the shelf life of the entire coating system.
[0016] 3. The prepared dual self-healing water-based coating uses water as a diluent, which can greatly reduce the VOC emissions of the coating and effectively reduce environmental pollution.
[0017] 4. Compared with existing products, the prepared dual self-healing water-based coating has the characteristics of low cost, simple process and excellent performance, meeting the needs of large-scale production and application. Implementation
[0018] In the above dual self-repairing water-based coating composition provided by the present invention, the function of the leveling agent is to enable the coating to wet the substrate and achieve rapid leveling. The leveling agent is preferably an aralkyl-modified polydimethylsiloxane, such as BYK-323, a product of German BYK Chemical Company.
[0019] The thickener is a rheological additive, and its functions are: adjusting the viscosity of the coating system, preventing sagging during construction, and giving the coating excellent mechanical properties and storage stability. The thickener of the present invention is preferably polyethylene wax, such as Hemmingsdeqian 201P.
[0020] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.
[0021] The following description describes optional embodiments of the present invention to teach those skilled in the art how to implement and reproduce the present invention. In order to teach the technical solution of the present invention, some conventional aspects have been simplified or omitted. It should be understood by those skilled in the art that variations or replacements derived from these embodiments will fall within the scope of protection of the present invention.
[0022] The sources of the components in the following examples are as follows: Dehydrated ricinoleic acid, phthalic anhydride, isophthalic acid, trimethylolpropane, dimethylolpropionic acid, catalyst, PMMA, emulsifier, antioxidant, triethylamine, and ethylene glycol monobutyl ether were purchased from Tianjin Jiangtian Chemical Technology Co., Ltd.
[0023] The leveling agents were purchased from BYK Chemicals of Germany with the product brand BYK-323.
[0024] The thickeners were purchased from Hemmings Specialty Additives Company of the United States, and the product brand was Deqian 201P.
[0025] Aliphatic polyisocyanate curing agents were purchased from Bayer AG, Germany. Example
[0026] 40 parts by weight of isophorone diisocyanate are added to 60 parts by weight of an organic solvent, butyl acetate, and stirred at a speed of 1000 r / min for 10 minutes to obtain an isophorone diisocyanate solution; 80 parts by weight of polymethyl methacrylate are slowly added to 20 parts by weight of the isophorone diisocyanate solution, and stirred at a speed of 2500 r / min for 12 hours in an environment of 70° C. to obtain a mixed solution of isophorone diisocyanate and polymethyl methacrylate; 18 parts by weight of the mixed solution and 2 parts by weight of an emulsifier are added to 80 parts by weight of deionized water, and stirred at a speed of 1500 r / min for 4 hours in an environment of 85° C., and PMMA microcapsules are obtained by centrifugation, washing, and drying; 44 parts by mass of dehydrated ricinoleic acid, 33 parts by mass of phthalic anhydride, 8.1 parts by mass of isophthalic acid, 28 parts by mass of trimethylolpropane, 13 parts by mass of dimethylolpropionic acid, 0.12 parts by mass of catalyst lithium hydroxide, 0.14 parts by mass of antioxidant 3,5-dibutyl-4-hydroxybenzoic acid, and 15 parts by mass of reflux xylene were added into a reaction bottle equipped with a stirrer, a thermometer, a water separator and a nitrogen conduit; heated to 150° C., stirred, set the speed to 800 r / min, and kept warm for about 0.5 hour; heated to 170° C., kept warm for about 1 hour; hours; raise the temperature to 185°C and keep it warm for about 1 to 2 hours; when the water output becomes slow, continue to raise the temperature to 210°C, and measure the acid value after 1 hour; control the acid value to 55mgKOH / g (resin), evaporate the solvent, cool to 80°C, add 18 parts by mass of ethylene glycol monobutyl ether, set the speed to 600-800r / min, stir for 1 hour, continue to cool to 60°C, add 10 parts by mass of triethylamine for neutralization, set the speed to 700r / min, and continue to stir for 0.5 hour; add 85 parts by mass of distilled water, filter to obtain a slightly branched hydroxyl saturated polyester water-based resin; 60 parts by mass of a lightly branched hydroxyl saturated polyester water-based resin and 2 parts by mass of a leveling agent were mixed at a speed of 700 r / min for 10 minutes, and then 3 parts by mass of a thickener were slowly added and dispersed at 1000 r / min for 20 minutes. Then, 35 parts by mass of PMMA microcapsules were added and dispersed at 500 r / min for 5 minutes to obtain a double self-healing water-based coating. Example
[0027] 60 parts by weight of hexamethylene diisocyanate are added to 40 parts by weight of an organic solvent, butyl acetate, and stirred at 900 r / min for 12 minutes to obtain a hexamethylene diisocyanate solution; 80 parts by weight of polymethyl methacrylate are slowly added to 20 parts by weight of the hexamethylene diisocyanate solution, and stirred at 2000 r / min for 24 hours in an environment of 80° C. to obtain a mixed solution of hexamethylene diisocyanate and polymethyl methacrylate; 15 parts by weight of the mixed solution and 5 parts by weight of an emulsifier are added to 80 parts by weight of deionized water, and stirred at 1500 r / min for 6 hours in an environment of 85° C., and PMMA microcapsules are obtained after centrifugation, washing, and drying. 41 parts by mass of dehydrated ricinoleic acid, 36 parts by mass of phthalic anhydride, 7.9 parts by mass of isophthalic acid, 28 parts by mass of trimethylolpropane, 15 parts by mass of dimethylolpropionic acid, 0.14 parts by mass of catalyst lithium hydroxide, 0.12 parts by mass of antioxidant 3,5-dibutyl-4-hydroxybenzoic acid, and 13 parts by mass of reflux xylene are added to a reaction bottle equipped with a stirrer, a thermometer, a water separator and a nitrogen conduit; heated to 140°C, stirred, set the speed to 800r / min, and kept warm for about 0.5 hour; heated to 160°C, kept warm The mixture was heated to 180°C and kept warm for about 1 hour; when the water output slowed down, the temperature was continued to be raised to 200°C, and the acid value was measured after 1 hour; the acid value was controlled to be 50 mgKOH / g (resin), the solvent was evaporated, the temperature was lowered to 80°C, 21 parts by weight of ethylene glycol monobutyl ether was added, the speed was set to 600 r / min, stirring was continued for 1 hour, the temperature was continued to be lowered to 60°C, 10 parts by weight of triethylamine was added for neutralization, the speed was set to 700 r / min, and stirring was continued for 0.5 hour; 90 parts by weight of distilled water was added, and the mixture was filtered to obtain a slightly branched hydroxyl saturated polyester water-based resin.
[0028] 80 parts by mass of a lightly branched hydroxyl saturated polyester water-based resin and 3 parts by mass of a leveling agent were mixed at a speed of 700 r / min for 10 minutes, and then 2 parts by mass of a thickener were slowly added and dispersed at 1000 r / min for 20 minutes. Then, 15 parts by mass of PMMA microcapsules were added and dispersed at 500 r / min for 5 minutes to obtain a double self-healing water-based coating. Example
[0029] 50 parts by mass of hydrogenated diphenylmethane diisocyanate are added to 50 parts by mass of organic solvent butyl acetate, and stirred at a speed of 1000 r / min for 10 minutes to obtain a hydrogenated diphenylmethane diisocyanate solution; 80 parts by mass of polymethyl methacrylate are slowly added to 20 parts by mass of hydrogenated diphenylmethane diisocyanate solution, and stirred at a speed of 2200 r / min for 18 hours in an environment of 80°C to obtain a mixed solution of hydrogenated diphenylmethane diisocyanate and polymethyl methacrylate; 18 parts by mass of the mixed solution and 2 parts by mass of an emulsifier are added to 80 parts by mass of deionized water, and stirred at a speed of 1300 r / min for 5 hours in an environment of 85°C, and PMMA microcapsules are obtained after centrifugation, washing, and drying. 42 parts by mass of dehydrated ricinoleic acid, 35 parts by mass of phthalic anhydride, 8 parts by mass of isophthalic acid, 28.1 parts by mass of trimethylolpropane, 14 parts by mass of dimethylolpropionic acid, 0.13 parts by mass of catalyst lithium hydroxide, 0.13 parts by mass of antioxidant 3,5-dibutyl-4-hydroxybenzoic acid, and 14 parts by mass of reflux xylene were added to a reaction bottle equipped with a stirrer, a thermometer, a water separator and a nitrogen conduit; heated to 145°C, stirred, set the speed to 700r / min, and kept warm for about 1 hour; heated to 165°C, kept warm about 2 hours; raise the temperature to 180°C and keep warm for about 1 hour; when the water output becomes slow, continue to raise the temperature to 205°C, and measure the acid value after 1 hour; control the acid value to 55mgKOH / g (resin), evaporate the solvent, cool to 80°C, add 19 parts by mass of ethylene glycol monobutyl ether, set the speed to 700r / min, stir for 1 hour, continue to cool to 60°C, add 11 parts by mass of triethylamine for neutralization, set the speed to 800r / min, and continue to stir for 0.5 hour; add 88 parts by mass of distilled water, filter to obtain a lightly branched hydroxyl saturated polyester water-based resin.
[0030] 70 parts by mass of a lightly branched hydroxyl saturated polyester water-based resin and 4 parts by mass of a leveling agent were mixed at a speed of 700 r / min for 10 minutes, and then 4 parts by mass of a thickener were slowly added and dispersed at 1000 r / min for 20 minutes. Then, 22 parts by mass of PMMA microcapsules were added and dispersed at 500 r / min for 5 minutes to obtain a double self-healing water-based coating.
[0031] Comparative Example 42 parts by mass of dehydrated ricinoleic acid, 35 parts by mass of phthalic anhydride, 8 parts by mass of isophthalic acid, 28.1 parts by mass of trimethylolpropane, 14 parts by mass of dimethylolpropionic acid, 0.13 parts by mass of catalyst lithium hydroxide, 0.13 parts by mass of antioxidant 3,5-dibutyl-4-hydroxybenzoic acid, and 14 parts by mass of reflux xylene were added to a reaction bottle equipped with a stirrer, a thermometer, a water separator and a nitrogen conduit; heated to 145°C, stirred, set the speed to 700r / min, and kept warm for about 1 hour; heated to 165°C, kept warm about 2 hours; raise the temperature to 180°C and keep warm for about 1 hour; when the water output becomes slow, continue to raise the temperature to 205°C, and measure the acid value after 1 hour; control the acid value to 55mgKOH / g (resin), evaporate the solvent, cool to 80°C, add 19 parts by mass of ethylene glycol monobutyl ether, set the speed to 700r / min, stir for 1 hour, continue to cool to 60°C, add 11 parts by mass of triethylamine for neutralization, set the speed to 800r / min, and continue to stir for 0.5 hour; add 88 parts by mass of distilled water, filter to obtain a lightly branched hydroxyl saturated polyester water-based resin.
[0032] 92 parts by mass of a lightly branched hydroxyl saturated polyester water-based resin and 4 parts by mass of a leveling agent were mixed at a rotation speed of 700 r / min for 10 minutes, and then 4 parts by mass of a thickener were slowly added and dispersed at 1000 r / min for 20 minutes and at 500 r / min for 5 minutes to obtain a self-repairing water-based coating.
[0033] The difference between the comparative example and Examples 1 to 3 is that the comparative example does not contain PMMA microcapsules.
[0034] The mechanical properties, corrosion resistance and self-repairing function of the double self-repairing coatings prepared in Examples 1 to 3 were compared with those of the comparative example after curing. The test results are listed in Table 1 and Table 2.
[0035] Table 1 Mechanical properties and corrosion resistance test results
[0036] Table 2 Dual self-repair function verification
[0037] From the above results, it can be seen that the paint film formed after curing of the dual self-repairing water-based coating provided by the present invention has high adhesion, hardness, impact strength, flexibility and strong elasticity. At the same time, it also has excellent dual self-repairing performance.
[0038] The above embodiments are only used to help understand the method and core idea of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.
[0039] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A method for preparing PMMA microcapsules, characterized in that: The following steps are involved: (1) Add 40-60 parts by mass of aliphatic polyisocyanate to 40-60 parts by mass of an organic solvent, butyl acetate, and stir at a speed of 800-1000 r / min for 10-15 min to obtain an aliphatic polyisocyanate solution A; (2) Slowly adding 75 to 80 parts by weight of polymethyl methacrylate to 20 to 25 parts by weight of the solution A, stirring at 2000 to 2500 r / min for 12 to 24 hours in an environment of 70 to 80° C. to obtain a mixed solution B of aliphatic polyisocyanate and polymethyl methacrylate; ⑶ Add 15-18 parts by weight of the mixed solution B and 2-5 parts by weight of the emulsifier to 80 parts by weight of deionized water, stir at 1200-1500 r / min for 4-6 hours in an environment of 85° C., and obtain PMMA microcapsules by centrifugation, washing, and drying; The PMMA microcapsule consists of a capsule wall and a capsule core. The capsule wall is polymethyl methacrylate, which is coated with sodium dodecylbenzene sulfonate and has hydrophilicity. The capsule core is aliphatic polyisocyanate.
2. A dual self-repairing water-based coating, characterized in that: The composition includes the following components in parts by weight: 15~35 parts of PMMA microcapsules, 60~80 parts of slightly branched hydroxyl saturated polyester water-based resin, 2~4 parts of leveling agent, 2~4 parts of thickener; The PMMA microcapsules are PMMA microcapsules provided by the preparation method according to claim 1; The slightly branched hydroxyl saturated polyester water-based resin is a polycondensate of a polyol and a polyacid, and is characterized in that the slightly branched hydroxyl saturated polyester water-based resin is prepared according to the following method: 41-44 parts by weight of dehydrated ricinoleic acid, 33-36 parts by weight of phthalic anhydride, 7.9-8.1 parts by weight of isophthalic acid, 28-28.2 parts by weight of trimethylolpropane, 13-15 parts by weight of dimethylolpropionic acid, 0.12-0.14 parts by weight of catalyst lithium hydroxide, 0.12-0.14 parts by weight of antioxidant 3,5-dibutyl-4-hydroxybenzoic acid, and 13-15 parts by weight of reflux xylene are added to a reaction bottle equipped with a stirrer, a thermometer, a water separator and a nitrogen conduit; heated to 140-150° C., stirred, set the speed to 600-800 r / min, and kept warm for about 0.5-1 hour; heated to 160-1 70℃, keep warm for about 1~2 hours; heat to 180~185℃, keep warm for about 1~2 hours; when the water output becomes slow, continue to heat to 200~210℃, measure the acid value after 1 hour; control the acid value to 50~55mgKOH / g (resin), evaporate the solvent, cool to 80℃, add 18~21 parts by weight of ethylene glycol monobutyl ether, set the speed to 600~800r / min, stir for 1 hour, continue to cool to 60℃, add 10~12 parts by weight of triethylamine for neutralization, set the speed to 700~800r / min, and continue to stir for 0.5~1 hour; add 85~90 parts by weight of distilled water, filter to obtain a slightly branched hydroxyl saturated polyester water-based resin.
3. The dual self-repairing water-based coating according to claim 2, characterized in that: ⑴ According to the standard GB∕T 1732-2020, the impact resistance is tested. The PMMA capsule wall is 40cm, the slightly branched hydroxyl saturated polyester water-based resin is 30cm, and the cross-linked reaction product of the PMMA microcapsule core and the water-based resin is 50cm; ⑵ According to the standard GB / T 6739-2006 test pencil hardness, PMMA capsule wall is H, slightly branched hydroxyl saturated polyester water-based resin is HB, PMMA microcapsule core and water-based resin cross-linking reaction product is 2H; The PMMA microcapsule wall has an impact resistance of 40 cm, which is slightly greater than the impact resistance of 30 cm of the slightly branched hydroxyl saturated polyester water-based resin, to ensure that external impact forces of different sizes cause different degrees of damage to the components of the coating, thereby playing a dual repair function; The capsule wall pencil hardness of the PMMA microcapsule is H, which needs to be slightly greater than the pencil hardness HB of the lightly branched hydroxyl saturated polyester water-based resin, to ensure that external scratches of different sizes cause different degrees of damage to the components of the coating, thereby playing a dual repair function.
4. The dual self-repairing water-based coating according to claim 2, characterized in that: The leveling agent is aralkyl modified polydimethylsiloxane.
5. The dual self-repairing water-based coating according to claim 2, characterized in that: The thickener is polyethylene wax.
6. The method for preparing the dual self-repairing water-based coating according to claim 2, characterized in that: The following steps are involved: 60-80 parts of lightly branched hydroxyl saturated polyester water-based resin and 2-4 parts of leveling agent were mixed at a speed of 700 r / min for 10 minutes, and then 2-4 parts of thickener were slowly added and dispersed at 1000 r / min for 20 minutes. Then, 15-35 parts of PMMA microcapsules were added and dispersed at 400-500 r / min for 5 minutes to obtain a double self-healing water-based coating.