An aqueous self-healing epoxy ester resin dispersion and a method of making the same

Abstract

The application discloses a kind of water-based self-repairing epoxy ester resin dispersions and preparation method thereof, the dispersion is composed of epoxy resin, dry fatty acid, polybasic acid anhydride, dihydric alcohol, (methyl) acrylate functional monomer containing o-diol group, organic boron compound, neutralizing agent and deionized water;Its preparation method adopts stepwise gradient temperature control process, first synthesizes epoxy ester prepolymer, then introduces o-diol active site to side group, then forms controllable borate ester pre-crosslinking structure with organic boron compound, and finally neutralizes self-emulsifying to finished product;The dispersion has dynamic borate ester reversible network and oxidation crosslinking double structure after film formation, can realize coating scratch self-repairing, simultaneously has excellent storage stability, anticorrosion corrosion resistance and re-coating adhesion, and VOC emission is extremely low, suitable for environmental protection type industrial anticorrosive coating field.

Description

Technical Field

[0001] This invention relates to the field of waterborne coating resin technology, specifically to a waterborne self-healing epoxy ester resin dispersion and its preparation method. Background Technology

[0002] With increasingly stringent environmental regulations, waterborne industrial coatings have become an important development direction in the field of metal protection. Compared with traditional solvent-based coatings, waterborne systems significantly reduce volatile organic compound (VOC) emissions, meeting increasingly stringent environmental regulations. However, existing waterborne epoxy ester resin technology still faces a long-standing and unresolved core problem—the coating inevitably suffers microscopic damage such as scratches and microcracks during service. Conventional epoxy ester resins form a permanent and irreversible covalent cross-linked network after curing, and the damage cannot be repaired on its own. This allows corrosive media to penetrate along the microcracks, continuously deteriorating the coating's protective performance and ultimately shortening the substrate's service life.

[0003] To address the aforementioned issues, Chinese patent document CN120607668A discloses a method for preparing a deionized waterborne epoxy ester dispersion for single-component industrial anti-corrosion coatings. This method involves high-temperature esterification of plant fatty acids, rosin, and E-14 epoxy resin to obtain an epoxy ester intermediate, followed by grafting of acrylate monomers and neutralization / emulsification. The aim is to solve the problems of slow drying of alkyd resins and complex application of epoxy resins. However, this approach still follows the traditional free radical polymerization and irreversible crosslinking approach. After curing, it still forms a static covalent network, completely lacking self-healing capabilities and failing to improve interlayer adhesion during recoating. This is an inherent defect of its technical approach.

[0004] Chinese patent document CN120574357A discloses a waterborne polymeric acrylate resin, its preparation method, and its application. This method achieves a self-healing coating by introducing 3-acrylamidophenylboronic acid into the acrylate copolymer, forming reversible borate ester bonds with the vicinal diol groups in the resin. However, this approach belongs to the adhesive field and is only applicable to pure acrylate systems. The resin structure is drastically different from epoxy ester systems, and its borate ester dynamic network is entirely dependent on alkaline conditions for triggering. Directly transplanting this into waterborne coatings would not only destroy the necessary water resistance and corrosion protection of the coating but also cause severe deterioration of mechanical properties due to excessively low crosslinking density, making it fundamentally unsuitable for meeting the basic requirements of industrial corrosion protection.

[0005] In the existing technology, there are no reports of combining the dynamic crosslinking mechanism of borate esters with waterborne epoxy ester resins, let alone technical solutions that introduce vicinal diol active sites into the side groups of epoxy esters through molecular structure design and form controllable pre-crosslinking with organoboron compounds. Summary of the Invention

[0006] The purpose of this invention is to provide a water-based self-healing epoxy ester resin dispersion. By introducing side groups containing vicinal diol structures into the water-based epoxy ester molecular chain and forming a dynamic borate ester crosslinking network with organoboron compounds, this invention solves the technical problems of irreversible coating damage, difficulty in recoating, and the contradiction between self-emulsification and water resistance in the prior art.

[0007] To address the aforementioned challenges, one objective of this invention is to provide an aqueous self-healing epoxy ester resin dispersion, prepared by means of the following components in parts by mass: 35-50 parts epoxy resin, 15-25 parts dry fatty acid, 8-15 parts polyacid anhydride, 3-8 parts diol, 2-5 parts (meth)acrylate functional monomer containing vicinal diol groups, 0.5-2 parts organoboron compound, 3-6 parts neutralizing agent, and 40-70 parts deionized water; wherein the (meth)acrylate functional monomer containing vicinal diol groups possesses both vicinal diol active sites and (meth)acrylate double bonds; the organoboron compound is selected from phenylboronic acid or 4-carboxyphenylboronic acid; and the neutralizing agent is selected from dimethylethanolamine, triethylamine, or 2-amino-2-methyl-1-propanol.

[0008] This formulation introduces reversible borate bonds into a waterborne epoxy ester system for the first time. This allows the coating to self-repair in a near-neutral environment after microcracks or scratches occur through the breaking and rearrangement of borate bonds, significantly extending its protective lifespan. During the room-temperature oxidative drying and curing process, the retained (meth)acrylate double bonds participate in the oxidative free radical crosslinking reaction of fatty acid chains, forming a double crosslinking network. This ensures the coating possesses higher crosslinking density and excellent mechanical properties, balancing self-healing ability and corrosion resistance. It addresses the core pain point of traditional epoxy ester resins, which form irreversible covalent networks after curing and cannot self-repair damage. Furthermore, it achieves stable water dispersion without additional emulsifiers, balancing the inherent contradiction between resin dispersion stability and post-curing water resistance.

[0009] Furthermore, the (meth)acrylate functional monomer containing the vicinal diol group is selected from either 2,3-dihydroxypropyl acrylate or 2,3-dihydroxypropyl methacrylate.

[0010] The vicinal diol group of the above monomer can rapidly form five- or six-membered cyclic borate esters with organoboron compounds, exhibiting excellent dynamic reversibility and a fast repair response rate, enabling efficient self-repair of micro-damage. The primary hydroxyl group of the monomer can undergo esterification with the carboxyl group on the prepolymer, thereby simultaneously introducing the vicinal diol structure and (meth)acrylate double bond into the side chain. During this grafting stage, the double bond is completely preserved, and the reaction process has no obvious side reactions, which will not interfere with the main chain crosslinking process, thus ensuring the final adhesion and anti-corrosion shielding performance of the coating.

[0011] Furthermore, the epoxy resin is selected from bisphenol A type epoxy resin or bisphenol F type epoxy resin. Even further, the bisphenol A type epoxy resin is selected from bisphenol A type epoxy resin E44 and / or bisphenol A type epoxy resin E51; the bisphenol F type epoxy resin is selected from bisphenol F type epoxy resin NPEF-170.

[0012] Bisphenol A or bisphenol F type epoxy resins are selected as the matrix resin. These epoxy resins contain a rigid benzene ring backbone and multiple epoxy groups in their molecular structure. The epoxy ester prepolymer formed after esterification with dry fatty acids has excellent adhesion, chemical corrosion resistance and mechanical strength, providing basic anti-corrosion and shielding performance for the coating. In the S1 stage, the epoxy groups of the epoxy resin mainly undergo ring-opening esterification with dry fatty acids to form the epoxy ester backbone. The carboxyl groups introduced by the polyacid anhydride, in addition to being partially used for subsequent neutralization and salt formation to achieve water dispersion, provide key reaction sites for the grafting of functional monomers containing vicinal diols in the S2 stage.

[0013] Furthermore, trimellitic anhydride is selected as the polybasic acid anhydride to introduce a carboxyl hydrophilic group.

[0014] Trimeric triglycerides can introduce carboxyl hydrophilic groups into the epoxy ester molecular chain. When combined with a neutralizing agent to form a salt, the resin can achieve self-emulsification and dispersion. No additional small molecule emulsifiers need to be added throughout the process, avoiding the problem of emulsifier residues migrating to the coating surface and deteriorating the coating's water resistance and adhesion. This solves the industry problem of waterborne epoxy esters being unable to simultaneously achieve "self-emulsification stability" and "water resistance after curing" from the molecular structure design level.

[0015] Furthermore, the drying fatty acid is selected from linoleic acid and / or dehydrated ricinoleic acid to provide oxidative drying crosslinking sites.

[0016] Linoleic acid and dehydrated ricinoleic acid with an iodine value ≥140 are high-drying fatty acids. Their molecular chains contain a large number of unsaturated double bonds, which can achieve self-drying curing of coatings through oxidative crosslinking at room temperature, providing core drying and crosslinking sites for single-component coatings. At the same time, the long-chain fatty acid structure can endow epoxy ester resin with good flexibility and film-forming leveling properties, improving the appearance of the coating. The clear iodine value index can strictly guarantee the oxidative drying rate and the final degree of crosslinking.

[0017] Furthermore, the diol is selected from neopentyl glycol, 1,4-butanediol, or 1,6-hexanediol, and is used to adjust the molecular weight and flexibility of the prepolymer.

[0018] These small-molecule diols can participate in esterification reactions, precisely adjusting the molecular weight and crosslinking degree of epoxy ester prepolymers. Differentiated control of resin properties can be achieved through the difference in carbon chain length of the diols: neopentyl glycol can improve the chemical resistance of the coating, while 1,4-butanediol and 1,6-hexanediol can optimize the flexibility and impact resistance of the coating. Manufacturers can flexibly adjust the formulation according to different application scenarios.

[0019] Another objective of this application is to provide a method for preparing an aqueous self-healing epoxy ester resin dispersion, comprising the following steps:

[0020] S1. Synthesis of epoxy ester prepolymer: Epoxy resin, dry fatty acid, polyacid anhydride and diol are heated to 150-170℃ under nitrogen protection for melt esterification reaction. When the acid value drops to 15-30mgKOH / g, epoxy ester prepolymer melt is obtained.

[0021] S2, Introduction of vicinal diol side groups: After the epoxy ester prepolymer melt is cooled to 120-140℃, add (meth)acrylate functional monomers containing vicinal diol structures, keep the reaction at the temperature for 1-2 hours, and esterify the prepolymer with the primary hydroxyl groups of the functional monomers and the residual carboxyl groups on the prepolymer to obtain modified epoxy ester prepolymers containing vicinal diol side groups.

[0022] S3, Boron ester pre-crosslinking: After the modified epoxy ester prepolymer containing vicinal diol side groups is cooled to 80-100℃, an organoboron compound is added, and the reaction is maintained at this temperature for 0.5-1.0h to form a boron ester pre-crosslinking product. Through the dehydration condensation of the organoboron compound with the vicinal diol side chain groups, a preliminary equilibrium network of dynamic covalent bonds of boron ester is established.

[0023] S4. Neutralization and self-emulsification: After the temperature of the product obtained in step S3 drops to 80-95℃, add a neutralizing agent to neutralize it, and then add deionized water dropwise under high-speed shearing to carry out self-emulsification dispersion.

[0024] S5. Obtain the finished product: Grind at 40-50℃ for 2-4 hours, then cool to 20-35℃, filter and discharge to obtain the finished product.

[0025] This stepwise reaction process sets the reaction temperature and steps according to the functional group reactivity gradient. First, the epoxy ester backbone is constructed, then functional side groups are introduced, and finally a pre-crosslinked structure is constructed and emulsified. This effectively avoids side reactions such as borate ester bond decomposition and double bond self-polymerization at high temperatures, ensuring the accuracy of each stage of the reaction and the uniformity of the product structure. Pre-crosslinking of borate ester before emulsification can ensure the storage stability of the aqueous dispersion, avoid abnormal dynamic bond reactions during storage, and ensure that the dynamic crosslinking points are evenly distributed in the coating after film formation, resulting in a uniform and stable self-healing effect. The entire process adopts a melt polymerization-self-emulsification process, which does not require additional organic solvents, has low VOC emissions, and meets environmental protection regulations.

[0026] Furthermore, the borate ester pre-crosslinked product formed in step S3 has a rotational viscosity of 5000-20000 mPa·s at 25°C, the degree of neutralization in step S4 is controlled at 85-95%, and the high-speed shear rate is controlled at 3000-5000 rpm.

[0027] By controlling the viscosity of the pre-crosslinked product at 5000-20000 mPa·s, the degree of pre-crosslinking of the borate ester can be precisely controlled: it avoids the subsequent emulsification difficulties, large particle size of the dispersion, and unstable storage caused by excessive crosslinking, while also avoiding the loss of the pre-crosslinking structure regulation function due to insufficient crosslinking, thus ensuring the self-healing efficiency after film formation; by controlling the degree of neutralization at 85-95%, it ensures that the carboxyl groups are fully neutralized to form stable hydrophilic groups, while avoiding excessive neutralization that leads to excessive hydrophilicity of the resin and affects the water resistance of the coating; by controlling the high-speed shear rate at 3000-5000 rpm, it ensures that the resin droplets are fully broken up during the emulsification process, forming an aqueous dispersion with narrow particle size distribution and excellent storage stability, while avoiding mechanical degradation and uncontrolled temperature rise caused by excessively high shear rates.

[0028] The beneficial effects are as follows: This application, through molecular structural innovation, introduces a (meth)acrylate functional monomer containing vicinal diol side groups onto the epoxy ester backbone, and forms a dynamic covalent borate ester bond with an organoboron compound. For the first time, it achieves autonomous repair of microcracks and scratches in the coating under near-neutral conditions in an aqueous epoxy ester system, effectively overcoming the technical bottleneck of irreversible cross-linking networks after traditional epoxy ester curing, which prevents repair of damage. Simultaneously, the retained (meth)acrylate double bonds can participate in the synergistic free radical cross-linking of unsaturated double bonds of dry fatty acids during the coating oxidation and drying process. The system forms a dual network structure of "dynamic borate ester bonds and oxidative crosslinking," which endows the coating with self-healing function while maintaining high crosslinking density and excellent mechanical strength and anti-corrosion shielding performance, avoiding the defects of insufficient mechanical properties and weak anti-corrosion ability of a single dynamic crosslinking system. In addition, the use of trimellitic anhydride to introduce carboxyl groups and the use of a neutralizing agent for self-emulsification eliminates the need for external emulsifiers, thus eliminating the hidden dangers of reduced water resistance and deteriorated adhesion of the coating caused by emulsifier migration at the molecular structure level. This fundamentally solves the contradiction between the storage stability of waterborne epoxy ester dispersions and the water resistance of the coating film.

[0029] Furthermore, this application employs a pre-crosslinking followed by emulsification process design. The pre-crosslinking structure of the borate ester is constructed before emulsification, ensuring the long-term storage stability of the aqueous dispersion and preventing abnormal side reactions of dynamic bonds during storage. It also ensures that the dynamic crosslinking points are uniformly distributed within the coating after film formation, guaranteeing a uniform and stable self-healing effect. The stepwise gradient temperature-controlled reaction process effectively avoids side reactions such as borate ester bond decomposition and acrylate double bond self-polymerization at high temperatures, ensuring the accuracy of functional group reactions at each stage and the uniformity of the product structure. Moreover, the entire process utilizes melt polymerization, resulting in extremely low organic solvent usage and VOC emissions far below industry limits, aligning with environmental regulations and the green development direction of industrial anti-corrosion coatings. Simultaneously, the presence of dynamic borate ester bonds improves the recoating adhesion of the coating. During recoating, the interface between the old and new coatings can form effective chemical bonds through the recombination of dynamic bonds, solving the problems of poor recoatability and weak interlayer bonding in traditional epoxy ester coatings, further enhancing the engineering application value of the product.

[0030] In summary, this invention provides a waterborne self-healing epoxy ester resin dispersion with self-healing function, high anti-corrosion performance, good recoatability and environmentally friendly low VOC properties, as well as its reliable preparation route. It has significant practical value and industrial significance for promoting the upgrading and application of waterborne industrial coatings in the field of metal protection. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to specific embodiments, so that those skilled in the art can more clearly understand the present invention.

[0032] The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. All other embodiments obtained by those skilled in the art based on the specific embodiments of the invention without inventive effort are within the protection scope of the invention. The technical solutions of the various embodiments can be combined with each other, but only on the basis that those skilled in the art can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope claimed by the invention.

[0033] In the embodiments of this invention, unless otherwise specified, all raw material components are commercially available products well-known to those skilled in the art; in the embodiments of this invention, unless specifically specified, the technical means used are all conventional means well-known to those skilled in the art. Where specific experimental steps or conditions are not specified in the embodiments, they can be performed according to the conventional experimental steps or conditions described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all conventional reagent products that can be obtained commercially. The rotational viscosity of the borate ester pre-crosslinked product in this application was measured at 25°C using a Brookfield viscometer, rotor No. 4, and a rotation speed of 30 rpm.

[0034] Raw material source:

[0035] Bisphenol A type epoxy resin E44 and bisphenol A type epoxy resin E51 are both provided by Jinan Qingtian Chemical Technology Co., Ltd.

[0036] Bisphenol F type epoxy resin NPEF-170 was provided by Greenlink (Jining) Chemical Technology Co., Ltd.

[0037] Trimeric triglyceride, CAS No. 552-30-7, was provided by Hubei Xingdongcheng Chemical Co., Ltd.

[0038] Linoleic acid, with an iodine value ≥160gI2 / 100g and an acid value ≥195mgKOH / g, was provided by Wuhan Jiyesheng Chemical Co., Ltd.

[0039] Dehydrated ricinoleic acid, with an iodine value ≥140gI2 / 100g and an acid value ≥195mgKOH / g, was provided by Wuhan Jiyesheng Chemical Co., Ltd.

[0040] Phenylated boric acid was provided by Hubei Jianchu Biomedical Co., Ltd.

[0041] 4-Carboxyphenylboronic acid was supplied by Nantong Runfeng Petrochemical Co., Ltd.

[0042] Dimethylethanolamine was provided by Jinan Juyang Chemical Technology Co., Ltd.

[0043] Triethylamine was supplied by Jinan Zesheng Chemical Co., Ltd.

[0044] 2-Amino-2-methyl-1-propanol was provided by Wuhan Jixin Yibang Biotechnology Co., Ltd.

[0045] 2,3-Dihydroxypropyl acrylate, CAS No. 10095-20-2, was provided by Hubei Jianchu Biomedical Co., Ltd.

[0046] 2,3-Dihydroxypropyl methacrylate (also known as glyceryl monomethacrylate, GMMA), CAS No. 5919-74-4, was provided by Shanghai Yongzheng Chemical Co., Ltd.

[0047] 2-Hydroxyethyl acrylate, CAS No. 818-61-1, was provided by Shandong Xinhongyunguang Chemical Co., Ltd.

[0048] Neopentyl glycol was provided by Hubei Jianchu Biomedical Co., Ltd.

[0049] 1,4-Butanediol (also known as 1,4-dihydroxybutane, BDO) was supplied by Nantong Changchen Chemical Co., Ltd.

[0050] 1,6-Hexanediol (also known as 1,6-dihydroxyhexane, HDO) was supplied by Wuhan Lanabai Pharmaceutical Chemical Co., Ltd.

[0051] Nonylphenol polyoxyethylene ether (NP-10) was provided by Jinan Xinkaiming Chemical Co., Ltd.

[0052] Adipic acid was supplied by Wuhan Jiyesheng Chemical Co., Ltd.

[0053] All other components are commercially available.

[0054] Example 1

[0055] This embodiment provides a water-based self-healing epoxy ester resin dispersion prepared from the following components in parts by mass:

[0056] Epoxy resin: Bisphenol A type epoxy resin E44, 42 parts

[0057] Dry fatty acids: Linoleic acid, 20 parts

[0058] Polymeric acid anhydrides: trimellitic anhydride, 12 parts

[0059] Diol: Neopentyl glycol, 5 parts

[0060] (Meth)acrylate functional monomers containing vicinal diol structures: 2,3-dihydroxypropyl acrylate, 4 parts

[0061] Organoboron compound: phenylboronic acid, 1.2 parts

[0062] Neutralizing agent: Dimethylethanolamine, 5 parts

[0063] Deionized water: 55 parts

[0064] The preparation method includes the following steps:

[0065] S1. Synthesis of epoxy ester prepolymer: Epoxy resin, dry fatty acid, polyacid anhydride and diol are added to the reactor according to the above mass parts. Under nitrogen protection, the temperature is raised to 160℃ at a uniform rate to carry out melt esterification reaction. The acid value of the system is monitored throughout the process. When the acid value drops to 22mgKOH / g, the reaction is stopped to obtain epoxy ester prepolymer melt.

[0066] S2, Introduction of vicinal diol side groups: After the epoxy ester prepolymer melt is cooled to 130℃, 2,3-dihydroxypropyl acrylate is added, and the reaction is maintained at this temperature for 1.5h to obtain a modified epoxy ester prepolymer containing vicinal diol side groups.

[0067] S3, Borate Pre-crosslinking: After the modified epoxy ester prepolymer containing vicinal diol side groups is cooled to 90°C, phenylboronic acid is added, and the reaction is maintained at this temperature for 0.8h to form a borate pre-crosslinking product with a rotational viscosity of 12500mPa·s at 25°C.

[0068] S4, Neutralization and Self-emulsification: After the temperature of the product obtained in step S3 drops to 88℃, dimethylethanolamine is added for neutralization, and the degree of neutralization is controlled at 90%. Then, 55 parts of deionized water are added dropwise under high-speed shearing at 4000rpm to carry out self-emulsification dispersion and obtain a dispersion system.

[0069] S5. Obtain the finished product: The dispersion system is kept at 45℃ for 3 hours and then cooled to 30℃. The product is filtered to obtain the water-based self-healing epoxy ester resin dispersion.

[0070] Example 2

[0071] The difference between this embodiment and Embodiment 1 is that:

[0072] The raw materials are prepared from the following components in parts by mass:

[0073] Epoxy resin: Bisphenol A type epoxy resin E44, 35 parts

[0074] Dry fatty acids: Linoleic acid, 15 parts

[0075] Polybasic acid anhydride: trimellitic anhydride, 8 parts

[0076] Diol: Neopentyl glycol, 3 parts

[0077] (Meth)acrylate functional monomers containing vicinal diol structures: 2,3-dihydroxypropyl acrylate, 2 parts

[0078] Organoboron compound: phenylboronic acid, 0.5 parts

[0079] Neutralizing agent: Dimethylethanolamine, 3 parts

[0080] Deionized water: 40 parts

[0081] Process parameters: Step S1 reaction temperature is 150℃, and the final acid value is 15 mg KOH / g; Step S2 reaction temperature is 120℃, and the reaction is maintained at this temperature for 1.0 h; Step S3 reaction temperature is 80℃, and the reaction is maintained at this temperature for 0.5 h, forming a borate ester pre-crosslinked product with a rotational viscosity of 5000 mPa·s at 25℃; Step S4 neutralization temperature is 80℃, the degree of neutralization is controlled at 85%, and the shear speed is 3000 rpm; Step S5 ripening temperature is 40℃, ripening time is 2 h, and the product is discharged after cooling to 20℃. Other components and steps are the same as in Example 1.

[0082] Example 3

[0083] The difference between this embodiment and Embodiment 1 is that:

[0084] The raw materials are prepared from the following components in parts by mass:

[0085] Epoxy resin: Bisphenol A type epoxy resin E44, 50 parts

[0086] Dry fatty acids: Linoleic acid, 25 parts

[0087] Polymeric acid anhydrides: trimellitic anhydride, 15 parts

[0088] Diol: Neopentyl glycol, 8 parts

[0089] (Meth)acrylate functional monomers containing vicinal diol structures: 2,3-dihydroxypropyl acrylate, 5 parts

[0090] Organoboron compound: phenylboronic acid, 2 parts

[0091] Neutralizing agent: Dimethylethanolamine, 6 parts

[0092] Deionized water: 70 parts

[0093] Process parameters: Step S1 reaction temperature is 170℃, and the final acid value is 30 mg KOH / g; Step S2 reaction temperature is 140℃, and the reaction is maintained at this temperature for 2 hours; Step S3 reaction temperature is 100℃, and the reaction is maintained at this temperature for 1 hour, forming a borate ester pre-crosslinked product with a rotational viscosity of 20000 mPa·s at 25℃; Step S4 neutralization temperature is 95℃, neutralization degree is 95%, and shear speed is 5000 rpm; Step S5 ripening temperature is 50℃, ripening time is 4 hours, and the product is discharged after cooling to 35℃. Other components and steps are the same as in Example 1.

[0094] Example 4

[0095] The difference between this embodiment and Example 1 is as follows: the epoxy resin is replaced with bisphenol A type epoxy resin E51, with an amount of 42 parts; the drying fatty acid is replaced with dehydrated ricinoleic acid, with an amount of 20 parts; the diol is replaced with 1,4-butanediol, with an amount of 5 parts; the (meth)acrylate functional monomer containing an ortho-diol structure is replaced with 2,3-dihydroxypropyl methacrylate, with an amount of 4 parts; and the neutralizing agent is replaced with triethylamine, with an amount of 5 parts. All other components and steps are the same as in Example 1.

[0096] Example 5

[0097] The difference between this embodiment and Example 1 is as follows: the epoxy resin is replaced with bisphenol F type epoxy resin NPEF-170, and the amount used is 42 parts; the diol is replaced with 1,6-hexanediol, and the amount used is 5 parts; the (meth)acrylate functional monomer containing the vicinal diol structure is replaced with 2,3-dihydroxypropyl methacrylate, and the amount used is 4 parts; the organoboron compound is replaced with 4-carboxyphenylboronic acid, and the amount used is 1.2 parts; the neutralizing agent is replaced with 2-amino-2-methyl-1-propanol, and the amount used is 5 parts. All other components and preparation methods are the same as in Example 1.

[0098] Comparative Example 1

[0099] The difference between this comparative example and Example 1 is that 2,3-dihydroxypropyl acrylate is not added to the formulation, and the step S2, which introduces the vicinal diol side group, is omitted. The epoxy ester prepolymer obtained in step S1 is directly cooled to 90°C and 1.2 parts of phenylboronic acid are added for pre-crosslinking. Other components and preparation methods are the same as in Example 1.

[0100] Comparative Example 2

[0101] The difference between this comparative example and Example 1 is that phenylboronic acid is not added to the formulation, and the S3 borate ester pre-crosslinking process is omitted. The modified epoxy ester prepolymer with vicinal diol side groups obtained in S2 is directly cooled to 88°C and neutralized with 5 parts of dimethylethanolamine. Other components and preparation methods are the same as in Example 1.

[0102] Comparative Example 3

[0103] The difference between this comparative example and Example 1 is that 4 parts of 2-hydroxyethyl acrylate (HEA, monohydroxy, without ortho-diol structure) are used instead of 4 parts of 2,3-dihydroxypropyl acrylate. All other components and preparation methods are the same as in Example 1.

[0104] Comparative Example 4

[0105] The difference between this comparative example and Example 1 is that 12 parts of the dicarboxylic acid adipic acid were used instead of 12 parts of the polycarboxylic acid anhydride trimellitic anhydride, and 2.5 parts of nonylphenol polyoxyethylene ether (NP-10) were added in step S4 to assist emulsification. All other components and preparation methods are the same as in Example 1.

[0106] Comparative Example 5

[0107] The difference between this comparative example and Example 1 is that the order of steps S2 and S3 is reversed. Specifically, after the epoxy ester prepolymer is synthesized, the temperature is first lowered to 90°C, then 1.2 parts of phenylboronic acid are added and the reaction is maintained at this temperature for 0.8 hours. Then, the temperature is raised to 130°C, then 4 parts of 2,3-dihydroxypropyl acrylate are added and the reaction is maintained at this temperature for 1.5 hours. All other process parameters remain the same as in Example 1.

[0108] Comparative Example 6

[0109] The difference between this comparative example and Example 1 is that the order of steps S3 and S4 is reversed. Specifically, after step S2, the modified epoxy ester prepolymer containing the vicinal diol side group is directly cooled to 88°C, and 5 parts of dimethylethanolamine are added for neutralization (90% neutralization). Then, 55 parts of deionized water are added dropwise under high-speed shear at 4000 rpm for emulsification. After emulsification, the dispersion is heated to 90°C, 1.2 parts of phenylboronic acid are added, and the reaction is maintained at this temperature for 0.8 hours. Then, it is matured at 45°C for 3 hours, cooled, and filtered before being discharged. All other components and preparation methods are the same as in Example 1.

[0110] Test case

[0111] Test subjects: Samples provided in Examples 1-5 and Comparative Examples 1-6.

[0112] Cold-rolled steel sheets were selected, sanded to Sa2.5 grade, and dried with acetone. The samples provided in each example and comparative example were coated onto the pretreated cold-rolled steel sheet surface using a 100μm wet film coater. The sheets were then ventilated and dried for 7 days at room temperature (25±2℃) and humidity (50±5%) to form a coating with a thickness of 30±2μm.

[0113] Storage stability of dispersions: The samples provided in Examples 1-5 and Comparative Examples 1-6 were stored at a constant temperature of 25°C, and the storage stability endpoint was defined as the time when obvious stratification / flocculation / gelation occurred.

[0114] The surface drying / complete drying time of the coating film shall be determined in accordance with GB / T1728-2020 "Determination of Drying Time of Paint Film and Putty Film" Method A (Finger Touch Method) / Method B (Cotton Ball Method) and tested at 25±2℃ and 50±5% humidity.

[0115] Adhesion testing shall be conducted in accordance with GB / T9286-2021 "Cross-cut test for paint and varnish films";

[0116] Flexibility shall be determined in accordance with GB / T1731-2020 "Test Method for Flexibility of Paint Film and Putty Film";

[0117] Adhesion: According to GB / T9286-2021 "Paints and Varnishes Cross-cut Test", the adhesion is determined by cross-cut method, and the coating adhesion level is judged according to the grading standard of 0 to 5, with level 0 being the best level where no coating peels off.

[0118] The recoating adhesion test was performed by lightly sanding the coated and fully cured sample of Example 1 with P320 sandpaper, then recoating the same dispersion sample and curing it, and conducting a cross-cut test according to GB / T 9286-2021.

[0119] Salt spray corrosion resistance time: According to GB / T10125-2021 "Artificial Atmosphere Corrosion Test Salt Spray Test", a 5wt% NaCl solution was used at 35±2℃ and pH 6.5~7.2. Continuous spraying was carried out, and the time when corrosion phenomena such as blistering, rusting, and peeling began to appear on the coating surface was recorded.

[0120] The impact resistance of the coating shall be tested in accordance with GB / T1732-2020 "Test Method for Impact Resistance of Coating Film";

[0121] Water resistance was tested according to GB / T1733-1993 "Test Method for Water Resistance of Coating Film". The coating was immersed in deionized water at 25±2℃, and the time when blistering, rusting, peeling and other corrosion phenomena first appeared on the coating surface was recorded.

[0122] Salt water resistance was tested according to GB / T1763-2020 "Test Method for Chemical Resistance of Coating Film". The coating was immersed in 3wt% NaCl solution at 25±2℃, and the time when blistering, rusting, peeling and other corrosion phenomena began to appear on the coating surface was recorded.

[0123] Scratch healing rate: The scratch method was used. First, a scratch with a width of about 50±2μm and a scratch depth of 15±2μm was artificially made on the sample surface. Then, the sample was placed in a near-neutral atmospheric environment (pH7±0.2) at 25℃, 50% relative humidity, and 25℃ for 48 hours. The change in scratch width was measured by optical microscope. The scratch healing rate was calculated by the following formula: Scratch healing rate (%) = (W0-Wt) / W0×100%, where W0 is the initial scratch width and Wt is the scratch width after repair.

[0124] Scratch healing rate after thermal cycling: After placing the sample in a temperature cycling chamber from -20℃ to 80℃ for 100 thermal cycles (60 min per cycle), the scratch repair ability was tested according to the above method.

[0125] The test results are shown in Table 1.

[0126] Table 1. Performance test results for each embodiment and comparative example.

[0127] project Storage stability (days) Coating surface drying time (min) Coating drying time (h) Adhesion (Grade) Recoating adhesion (grade) Impact resistance of coating (kg·cm) Example 1 183 37 6.5 0 0 54 Example 2 190 35 6.2 0 0 59 Example 3 180 42 7.0 0 0 52 Example 4 187 38 6.6 0 0 56 Example 5 182 40 6.8 0 0 58 Comparative Example 1 178 35 6.2 0 2 43 Comparative Example 2 166 37 6.5 1 3 35 Comparative Example 3 172 36 6.4 0 3 40 Comparative Example 4 75 38 6.8 2 4 37 Comparative Example 5 68 45 7.3 2 4 34 Comparative Example 6 57 42 6.9 1 3 31

[0128] Table 1 Performance test results of each embodiment and comparative example (continued)

[0129] project Water resistance (h) Salt water resistance (h) Salt spray corrosion resistance time (h) Scratch healing rate (%, initial) Scratch healing rate (%) after thermal cycling, after 100 thermal cycles Example 1 365 256 213 86 76 Example 2 359 278 205 84 74 Example 3 401 263 222 89 81 Example 4 382 249 219 88 79 Example 5 374 271 208 82 70 Comparative Example 1 351 225 165 0 0 Comparative Example 2 333 189 132 15 10 Comparative Example 3 346 235 179 22 12 Comparative Example 4 186 123 105 85 75 Comparative Example 5 198 151 124 45 30 Comparative Example 6 212 142 119 55 35

[0130] As can be seen from the data in Table 1, all embodiments exhibit excellent comprehensive performance: storage stability at 25℃ exceeds 180 days, meeting the storage requirements of industrial water-based coatings; surface drying time is 35-42 minutes and complete drying time is 6.2-7.0 hours, balancing construction efficiency and leveling properties; adhesion is the best grade 0, impact resistance reaches over 52 kg·cm, and flexibility and mechanical strength are well balanced; water resistance reaches over 359 hours, salt water resistance reaches over 249 hours, and salt spray corrosion resistance reaches over 205 hours; scratch healing rate reaches over 82%, and after 100 thermal cycles, it still maintains a healing rate of over 70%, demonstrating the reliability of the dynamic borate ester network under long-term service conditions.

[0131] Comparative Example 1, without the addition of 2,3-dihydroxypropyl acrylate and omitting step S2 (the introduction of the vicinal diol side group), exhibited a near-zero scratch healing rate. This is likely due to the lack of vicinal dihydroxyl active sites in the system that can form reversible cyclic boronic acid esters with organoboron compounds. The organoboron compounds cannot participate in the construction of a dynamic covalent network, remaining dispersed in the resin matrix only in a free state or with weak interactions. Therefore, the coating cannot heal through the breaking and rearrangement of chemical bonds after damage, resulting in a near-complete loss of self-repair function. Furthermore, the lack of acrylate double bonds participating in oxidative crosslinking leads to a decrease in the overall crosslinking density of the coating, which may be the core reason for its weaker impact resistance, salt water resistance, and salt spray performance compared to the examples. Notably, its basic adhesion and storage stability did not show significant deterioration, indirectly confirming that the absence of the vicinal diol side group does not disrupt the basic film-forming properties of the epoxy ester backbone.

[0132] In Comparative Example 2, phenylboronic acid was not added to the formulation, and the S3 borate ester pre-crosslinking process was omitted. The resulting coating exhibited extremely low scratch healing rate. This is likely because the system only contains a single static covalent network formed by the oxidative crosslinking of dry fatty acids and acrylate double bonds. Although the vicinal diol side groups are retained, the lack of a boron source prevents the formation of a dynamic borate ester crosslinking network. Therefore, the coating essentially lacks self-healing capabilities, and may only exhibit a very slight scratch healing effect due to the room-temperature creep of the resin molecular chains. Furthermore, the absence of the borate ester pre-crosslinking structure reduces the uniformity of the crosslinking network during resin film formation, weakens interfacial bonding, and leads to a significant decrease in coating adhesion, impact resistance, and corrosion resistance. This indicates that the dynamic borate ester network not only provides self-healing functionality but can also regulate the resin microstructure through pre-crosslinking, forming a synergistic reinforcing effect with the oxidative crosslinking network to jointly improve the mechanical and protective properties of the coating.

[0133] Comparative Example 3, which used monohydroxy acrylate-2-hydroxyethyl ester instead of the functional monomer containing the vicinal diol structure, showed a significantly lower scratch healing rate than the examples. This may be because, although the monohydroxy group can still undergo esterification grafting with the carboxyl group of the prepolymer, the monohydroxy structure cannot form cyclic borate esters with phenylboronic acid, but can only form unstable linear borate esters or physical complexes with extremely low bond exchange activity, making it difficult to achieve effective network rearrangement after damage. Simultaneously, due to the difference in monomer structure, the contribution of side groups to the crosslinking network decreases, and the mechanical strength and corrosion resistance of the coating also show a certain degree of attenuation. This demonstrates the irreplaceable role of the vicinal diol structure in constructing a dynamic borate ester self-healing system.

[0134] Comparative Example 4, which replaced trimellitic anhydride with the dicarboxylic acid adipic acid, significantly reduced the carboxyl content of the system, resulting in insufficient hydrophilicity. Nonylphenol polyoxyethylene ether emulsifiers were required to achieve water dispersion. While the presence of emulsifiers provided short-term dispersion assistance, they tended to migrate to the coating surface after film formation, leading to decreased interfacial adhesion and significant deterioration in water and salt water resistance. Furthermore, the aliphatic adipic acid backbone exhibited weaker chemical corrosion resistance than the aromatic trimellitic anhydride, resulting in insufficient coating shielding performance and a salt spray tolerance time far lower than in the examples. These comparative results clearly demonstrate that the multi-carboxyl structure introduced by trimellitic anhydride can achieve molecular-level self-emulsification without the need for external emulsifiers, and its aromatic ring backbone contributes positively to chemical resistance. Notably, its self-healing properties were similar to those in the examples, indirectly confirming that the repair ability of the dynamic borate ester network itself is almost unaffected by the source of carboxyl groups.

[0135] Comparative Example 5 reversed the order of steps S2 (ovaldiol grafting) and S3 (boron ester pre-crosslinking), i.e., the boron ester reaction was performed first, followed by an attempt to introduce the ovaldiol monomer. This operation resulted in significant difficulties during the emulsification stage, poor storage stability of the dispersion, and a substantial decrease in the mechanical properties and self-healing efficiency of the coating film. This may be because the organoboron compound added early preferentially crosslinks with the free ovaldiol monomer in the system, not only consuming the active sites required for subsequent grafting reactions but also potentially forming locally over-crosslinked gel particles. At the same time, the boron ester bonds are prone to thermal decomposition at high temperatures, further exacerbating the uncontrolled degree of pre-crosslinking. Ultimately, this leads to coarse particle size during emulsification, a sharp decline in storage stability, and simultaneous deterioration of mechanical and anti-corrosion properties after film formation. This demonstrates that a stepwise reaction following the functional group reactivity gradient, first constructing functional side groups and then forming pre-crosslinks, is crucial for ensuring the structural uniformity and performance stability of the product.

[0136] Comparative Example 6 reversed the order of steps S3 and S4, adopting a process route of emulsification followed by crosslinking. This resulted in a sharp deterioration in the storage stability of the dispersion. This may be because after emulsification, the resin is dispersed in the aqueous phase in the form of particles, making it difficult for phenylboronic acid to diffuse into the particles. The crosslinking reaction tends to occur on the particle surface, leading to flocculation or even gelation of the dispersion during storage, resulting in significantly lower storage stability than the example. After film formation, the dynamic crosslinking points are extremely unevenly distributed in the coating body, exhibiting obvious interfacial enrichment characteristics. This leads to a decrease in the overall mechanical properties and anti-corrosion barrier properties of the coating, and the self-healing effect is also uneven due to the uneven distribution of crosslinking points. The overall performance of this comparative example is significantly lower than that of the example, fully demonstrating that the process design of pre-crosslinking followed by emulsification plays a crucial role in ensuring the stability of the dispersion and the uniformity of coating performance.

[0137] In summary, the comparative examples verified the overall innovation of this invention in terms of molecular structure design, raw material selection, and process route from different dimensions: the synergistic effect of the vicinal diol side group and organoboron compound is the core prerequisite for achieving self-healing function; the selection of trimellitic anhydride is the key to balancing dispersion stability and water resistance; the stepwise gradient temperature control and the process design of "pre-crosslinking followed by emulsification" are important supports for ensuring the uniformity of product structure and performance stability. The various technical elements are coupled with each other to jointly achieve a synergistic improvement in the self-healing function, mechanical strength, anti-corrosion performance, and storage stability of the waterborne epoxy ester resin dispersion.

[0138] The above are merely embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A water-based self-healing epoxy ester resin dispersion, characterized in that, The product is prepared according to the following components in parts by weight: 35-50 parts epoxy resin, 15-25 parts dry fatty acid, 8-15 parts polyacid anhydride, 3-8 parts diol, 2-5 parts (meth)acrylate functional monomer containing vicinal diol group, 0.5-2 parts organoboron compound, 3-6 parts neutralizing agent, and 40-70 parts deionized water; wherein the (meth)acrylate functional monomer containing vicinal diol group has both vicinal diol active site and (meth)acrylate double bond; the organoboron compound is selected from phenylboronic acid or 4-carboxyphenylboronic acid; the neutralizing agent is selected from any one of dimethylethanolamine, triethylamine, or 2-amino-2-methyl-1-propanol.

2. The waterborne self-healing epoxy ester resin dispersion according to claim 1, characterized in that, The (meth)acrylate functional monomer containing the vicinal diol group is selected from either 2,3-dihydroxypropyl acrylate or 2,3-dihydroxypropyl methacrylate.

3. The waterborne self-healing epoxy ester resin dispersion according to claim 1, characterized in that, The epoxy resin is selected from bisphenol A type epoxy resin or bisphenol F type epoxy resin.

4. The waterborne self-healing epoxy ester resin dispersion according to claim 3, characterized in that, The bisphenol A type epoxy resin is selected from bisphenol A type epoxy resin E44 and / or bisphenol A type epoxy resin E51.

5. The waterborne self-healing epoxy ester resin dispersion according to claim 3, characterized in that, The bisphenol F type epoxy resin used is NPEF-170 bisphenol F type epoxy resin.

6. The waterborne self-healing epoxy ester resin dispersion according to claim 1, characterized in that, The polyacid anhydride is selected from trimellitic anhydride.

7. The waterborne self-healing epoxy ester resin dispersion according to claim 1, characterized in that, The dry fatty acids are selected from linoleic acid and / or dehydrated ricinoleic acid.

8. The waterborne self-healing epoxy ester resin dispersion according to claim 1, characterized in that, The diol is selected from neopentyl glycol, 1,4-butanediol, or 1,6-hexanediol.

9. A method for preparing the aqueous self-healing epoxy ester resin dispersion according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Synthesis of epoxy ester prepolymer: Epoxy resin, dry fatty acid, polyacid anhydride and diol are heated to 150-170℃ under nitrogen protection for melt esterification reaction. When the acid value drops to 15-30mgKOH / g, epoxy ester prepolymer melt is obtained. S2, Introduction of vicinal diol side groups: After the epoxy ester prepolymer melt is cooled to 120-140℃, add (meth)acrylate functional monomers containing vicinal diol structures, and keep the reaction at the temperature for 1-2 hours to obtain modified epoxy ester prepolymers containing vicinal diol side groups. S3, Boron ester pre-crosslinking: After the modified epoxy ester prepolymer containing vicinal diol side groups is cooled to 80-100℃, an organoboron compound is added, and the reaction is maintained at this temperature for 0.5-1.0h to form a boron ester pre-crosslinking structure; S4. Neutralization and self-emulsification: After the temperature of the product obtained in step S3 drops to 80-95℃, add a neutralizing agent to neutralize it, and then add deionized water dropwise under high-speed shearing to carry out self-emulsification dispersion. S5. Obtain the finished product: After maturation, cooling, and filtration, the finished product is obtained.

10. The method for preparing the waterborne self-healing epoxy ester resin dispersion according to claim 9, characterized in that, The borate ester pre-crosslinked product formed in step S3 has a rotational viscosity of 5000-20000 mPa·s at 25°C, and the degree of neutralization in step S4 is controlled at 85-95%, while the high-speed shear rate is controlled at 3000-5000 rpm.