Self-healing exposed single-component waterproof coating, its preparation method and application

Abstract

This invention provides an exposed single-component waterproof coating with self-healing function, its preparation method, and its application. The exposed single-component waterproof coating, based on a total weight percentage of 100 wt%, comprises: 25-50 wt% fluorocarbon emulsion, 5-20 wt% microcapsule self-healing agent, 0.1-1 wt% water-resistant agent, 0.1-3 wt% film-forming aid, 0.1-1 wt% stabilizer, 0.1-1 wt% bactericide and preservative, with the balance being water. The fluorocarbon emulsion is a core-shell polymer emulsion. The outer shell is formed by emulsion polymerization of fluorinated acrylate monomers, furan-structured monomers, and maleimide-structured monomers, while the core is formed by emulsion polymerization of soft acrylate monomers and hard acrylate monomers. The emulsion polymerization is carried out in an aqueous solution containing emulsifiers and initiators. The microcapsule self-healing agent has a core-shell structure, including a urea-formaldehyde resin shell and a fluorooil core material encapsulated within the urea-formaldehyde resin shell.

Description

Technical Field

[0001] This invention belongs to the field of waterproof coating technology, and particularly relates to an exposed single-component waterproof coating with self-healing function, its preparation method and application. Background Technology

[0002] The unique carbon-fluorine (CF) bonds in fluorocarbon resins, with a bond energy reaching 485.3 kJ / mol, endow fluorocarbon resins with excellent weather resistance, corrosion resistance, and chemical stability. The low surface energy of fluoroalkyl compounds (typically 13-20 mN / m) results in a smoother surface in finished paints, thus providing strong stain resistance. Based on these advantages, fluorocarbon resins or emulsions are widely used in building surfaces, underground engineering, and metal structure protection.

[0003] However, when fluorocarbon emulsions are applied to single-component waterproof coatings, the existing technology has the following shortcomings:

[0004] (1) Fluorocarbon emulsions are not flexible enough. When subjected to thermal expansion and contraction for a long time or used on substrates with high activity, they are prone to micro-cracks that become water seepage channels. Moreover, the cracks are difficult to heal themselves, which reduces or even fails the waterproofing effect.

[0005] (2) Single-component coatings generally lack a “trauma response” mechanism. Most common self-healing waterproof coatings are two-component materials (such as polyurethane and epoxy microcapsule systems), which are complicated to construct and have poor storage stability.

[0006] (3) There is insufficient research on self-healing technology in fluorocarbon emulsion systems. Fluorocarbon systems have strong hydrophobicity and low surface energy, making them difficult to be compatible with traditional microcapsules, which in turn makes it difficult for self-healing agents to be evenly dispersed or released at the fracture surface.

[0007] Therefore, it is of great significance to develop a single-component waterproof coating that is easy to apply, can self-heal cracks at room temperature, and has high weather resistance. Summary of the Invention

[0008] In view of this, the present invention provides an exposed single-component waterproof coating with self-healing function, its preparation method, and its application, in order to at least partially solve the above-mentioned technical problems. The technical solution provided by the present invention is as follows.

[0009] As a first aspect of the present invention, an exposed single-component waterproof coating with self-healing function is provided, comprising, by weight percentage (100wt%): 25-50wt% fluorocarbon emulsion, 5-20wt% microcapsule self-healing agent, 0.1-1wt% water-resistant agent, 0.1-3wt% film-forming aid, 0.1-1wt% stabilizer, 0.1-1wt% bactericide and preservative, with the balance being water; wherein, the fluorocarbon emulsion is a core-shell polymer emulsion, the outer shell being formed by emulsion polymerization of fluorinated acrylate monomers, furan-structured monomers, and maleimide-structured monomers, and the core being formed by emulsion polymerization of acrylate soft monomers and acrylate hard monomers, both of which are polymerized in an aqueous solution containing an emulsifier and an initiator; the microcapsule self-healing agent has a core-shell structure, including a urea-formaldehyde resin shell layer and a fluorooil core material encapsulated within the urea-formaldehyde resin shell layer.

[0010] As a second aspect of the present invention, a method for preparing an exposed single-component waterproof coating is provided, comprising: adding fluorocarbon emulsion, water-resistant agent, film-forming aid, and stabilizer into a reactor and mixing them evenly to form a base material; adding microcapsule self-healing agent, bactericide and preservative, and the remaining water to the base material to obtain a single-component waterproof coating.

[0011] As a third aspect of the present invention, an application of an exposed single-component waterproof coating in the field of building protection is provided.

[0012] In the technical solution of this invention, furan-structured monomers and maleimide-structured monomers form a reversible dynamic covalent network (DA) through a Diels-Alder (DA) reaction. This invention introduces the DA reversible dynamic covalent network into the shell structure of the fluorocarbon emulsion via emulsion polymerization, rather than through physical blending or small molecule addition. This significantly improves the structural stability of the coating, enhances its self-healing efficiency and sustainability, significantly improves its compatibility with the fluorocarbon system, strengthens process controllability and repeatability, and effectively avoids adverse effects on mechanical properties. When the waterproof coating, after curing, is subjected to internal stress or external force leading to bond breakage and cracking, the DA reversible dynamic covalent network can spontaneously and reversibly recombine under thermal triggering, macroscopically demonstrating the self-repair of microcracks in the waterproof coating. When microcracks propagate in the waterproof coating, the wall material of the microcapsule self-healing agent within the coating is damaged, releasing the embedded fluorooil core material which penetrates into the crack and spreads to form a continuous phase. Under the influence of water and air, a curing reaction occurs to seal the crack and locally generate a hydrophobic layer, thus endowing the self-healing area with strong hydrophobic and antifouling properties. Through the aforementioned two mechanisms—the DA dynamic reversible covalent network and the microcapsule self-healing agent—a dual-channel self-healing mechanism is achieved in the waterproof coating, resulting in more stable performance. Detailed Implementation

[0013] The following describes embodiments of the present invention; however, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the invention. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the invention for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0014] To address the problems in existing technologies where fluorocarbon emulsion systems are highly hydrophobic and have low surface energy, making it difficult for traditional microcapsule self-healing agents to be compatible with them, for fluorocarbon emulsions and microcapsule self-healing agents to be uniformly dispersed within waterproof coatings, and for effective release at fracture surfaces of waterproof coatings, this invention designs and constructs a DA dynamic reversible covalent network structure for fluorocarbon emulsions to make them compatible with microcapsule self-healing agents, and proposes a dual-repair mechanism of fluorocarbon emulsions and microcapsule self-healing agents to solve the aforementioned problems.

[0015] Specifically, in this invention, furan-based monomers and maleimide-based monomers directly participate in the copolymerization reaction of the fluorocarbon emulsion. This allows the reversible dynamic covalent bond network of DA (furan and maleimide) formed by the Diels-Alder (DA) reaction to become part of the fluorocarbon emulsion shell structure. This achieves high compatibility with the fluorocarbon matrix at the molecular level, avoiding phase separation problems that occur after long-term storage of physical mixtures, while simultaneously ensuring the stability and mechanical properties of the waterproof coating. When cracks appear in the waterproof coating, the reversible dynamic covalent bonds of DA on the fluorocarbon emulsion shell preferentially undergo reversible recombination at the crack interface, achieving initial crack closure. Based on this, a microcapsule self-healing agent is introduced as a secondary repair unit. When the crack damage is significant, the embedded self-healing agent is triggered and released. The released self-healing agent functions within the crack region pretreated by the DA dynamic reversible covalent bonds, thus achieving stable and effective multi-channel synergistic self-healing in the fluorocarbon emulsion system, overcoming the shortcomings of existing technologies.

[0016] Specifically, as a first aspect of the present invention, the provided exposed single-component waterproof coating with self-healing function comprises, by weight percentage (100wt%): 25-50wt% fluorocarbon emulsion, 5-20wt% microcapsule self-healing agent, 0.1-1wt% water-resistant agent, 0.1-3wt% film-forming aid, 0.1-1wt% stabilizer, 0.1-1wt% bactericide and preservative, with the balance being water; wherein, the fluorocarbon emulsion is a core-shell polymer emulsion, the outer shell being formed by emulsion polymerization of fluorinated acrylate monomers, furan-structured monomers, and maleimide-structured monomers, and the core being formed by emulsion polymerization of acrylate soft monomers and acrylate hard monomers, both of which are polymerized in an aqueous solution containing emulsifier and initiator; the microcapsule self-healing agent has a core-shell structure, including a urea-formaldehyde resin shell layer and a fluorooil core material encapsulated within the urea-formaldehyde resin shell layer.

[0017] In this invention, given the problems with fluorocarbon emulsions, existing self-healing systems fail to effectively combine the dynamic reversible covalent bonds of the DA structure in the shell layer with microcapsule self-healing agents in the same water-based fluorocarbon emulsion waterproof coating system. To address these issues, this invention improves the structure and self-healing mechanism of the waterproof coating by proposing to introduce a reversible dynamic covalent bond network of DA, formed by the Diels-Alder (DA) reaction of furan-type monomers and maleimide-type monomers, into the shell structure of the fluorocarbon emulsion through emulsion polymerization. Compared to traditional methods of physical blending or small molecule addition, this invention's formation of reversible dynamic covalent bonds offers the following advantages:

[0018] 1) Significantly improved structural stability: In physical blending, DA functional components are dispersed in the system as small molecules or oligomers, which are prone to migration, phase separation, or precipitation during storage and film formation, leading to a decline in self-healing function. In contrast, this invention uses copolymerization to fix the DA functional components to the emulsion particle shell through reversible dynamic covalent bonds, achieving chemical bonding, avoiding functional component migration, and improving the long-term stability of the system.

[0019] 2) Higher and more sustainable self-healing efficiency: In physical blending systems, DA functional components may be embedded in the matrix or unevenly distributed during film formation, making it difficult to effectively participate in reversible reactions at crack interfaces; however, in this invention, DA reversible dynamic covalent bonds are enriched in the emulsion particle shell layer, making it easier to distribute at particle interfaces and defect areas in the coating film. When cracks occur, reversible fracture and recombination can occur preferentially, thereby achieving rapid and repeatable self-healing.

[0020] 3) The compatibility with fluorocarbon systems is significantly improved: Fluorocarbon emulsion systems have low surface energy and strong hydrophobicity. Physically mixed small molecule DA functional components usually have poor compatibility with fluorocarbon and are prone to interfacial defects. However, this invention introduces the reversible dynamic covalent bond of DA into the surface of fluorocarbon emulsion particles through copolymerization, so that it forms an integrated structure with the fluorocarbon skeleton, thereby significantly improving the interfacial compatibility and dispersion uniformity of the system.

[0021] 4) Avoid adverse effects on mechanical properties: Physically mixed small molecules usually act as plasticizers or defect sources, which may reduce the mechanical properties of the coating. However, in this invention, the DA reversible dynamic covalent bond participates in the construction of the film network as part of the polymer chain segment. While providing self-healing ability, it does not significantly weaken the mechanical strength of the coating. It can even improve the elongation at break through dynamic cross-linking.

[0022] 5) Enhanced process controllability and repeatability: Physical blending methods are sensitive to dispersion conditions, resulting in significant performance fluctuations between different batches; this invention achieves in-situ construction of reversible dynamic covalent bonds of DA through emulsion polymerization, and the content and distribution of reversible dynamic covalent bonds of DA can be precisely controlled through monomer ratio and polymerization process, thereby improving product consistency and industrial feasibility.

[0023] Therefore, this invention achieves the stable existence and efficient function of reversible dynamic covalent DA in fluorocarbon emulsions through the "chemical introduction + structural positioning" method, which is significantly better than the physical mixing method in the prior art.

[0024] In the early stages of damage to the waterproof coating, the dynamic reversible covalent bonds of DA within the coating spontaneously and reversibly recombine under thermal triggering, restoring the surface microstructure. Macroscopically, this manifests as the self-repair of microcracks in the waterproof coating. As the depth of damage to the waterproof coating increases, the microcracks expand, the wall material of the microcapsule self-healing agent in the waterproof coating is destroyed, and the embedded fluorinated oil core material passively flows into the cracks, spreading to form a continuous phase to fill the pores. Under the action of water and air, a curing reaction occurs to seal the cracks and locally generate a hydrophobic layer, thus endowing the self-healing area with strong hydrophobic and antifouling properties. This invention achieves dual-channel self-healing of the waterproof coating through the above-mentioned dynamic reversible covalent bond network of DA and the microcapsule self-healing agent.

[0025] According to embodiments of the present invention, the raw materials for preparing fluorocarbon emulsions include: seed monomers, auxiliaries, and the balance water. The seed monomers, based on a total weight of 100 parts, include: 20-55 parts of fluorinated acrylate monomers, 15-45 parts of soft acrylate monomers, 10-35 parts of hard acrylate monomers, 2-15 parts of furan-structured monomers, and 0.5-5 parts of maleimide-structured monomers; the auxiliaries, based on a total weight of 100 parts of seed monomers, include 1-5 parts of emulsifier, 0.3-1.5 parts of initiator, 0.1-1 part of pH adjuster, 0.1-0.5 parts of defoamer, and 0.1-0.3 parts of bactericide and preservative; and the water, which can be deionized water or ultrapure water, is 80-200 parts of the total weight of seed monomers. It should be noted that the amounts of additives and water are calculated relative to the total amount of seed monomers. For example, if the total weight of seed monomers is 100 parts, the emulsifier is 1-5 parts. Alternatively, it can be understood that the raw materials for preparing fluorocarbon emulsions include, by weight percentage (100 wt%), the seed monomers as follows: 20-55 wt% fluorinated acrylate monomers, 15-45 wt% soft acrylate monomers, 10-35 wt% hard acrylate monomers, 2-15 wt% furan-structured monomers, and 0.5-5 wt% maleimide-structured monomers; 1-5 wt% emulsifier, 0.3-1.5 wt% initiator, 0.1-1 wt% pH adjuster; 0.1-0.5 wt% defoamer; 0.1-0.3 wt% bactericide and preservative; and 80-200 wt% water.

[0026] Fluorinated acrylate monomers include fluorinated vinyl acrylate monomers, which are selected from either perfluorooctyl ethyl acrylate or perfluorohexyl ethyl acrylate. Fluorinated acrylate monomers provide hydrophobicity and weather resistance to fluorocarbon emulsions.

[0027] Furan-structured monomers are polymerizable monomers containing a furan ring, selected from any one of 2,5-bis(hydroxymethyl)furan, furfuryl alcohol-modified acrylates, and methacrylate compounds, with furfuryl methacrylate being the preferred methacrylate compound. Maleimide-structured monomers are reversible crosslinking agents, selected from any one of N,N'-(1,3-phenylene)dimaleimide (BMI) and 4,4'-bismaleimide diphenylmethane. The furan-structured monomers and maleimide-structured monomers form a dynamic reversible covalent network through the Diles-Alder (DA) reaction. When the waterproof coating is subjected to internal stress or external force causing bond breakage and cracks to appear, this dynamic reversible covalent network structure automatically reorganizes under thermal triggering, thus macroscopically repairing the microcracks in the waterproof coating and achieving self-healing.

[0028] The acrylate soft monomers are selected from at least one of butyl acrylate (BA), 2-ethylhexyl acrylate, or isooctyl acrylate; the acrylate hard monomers are selected from at least one of methyl methacrylate (MMA), styrene-acrylate copolymer, or isobornyl acrylate. Adding acrylate soft monomers to fluorocarbon emulsions can effectively improve the elongation at break of the waterproof coating and enhance its crack resistance; adding acrylate hard monomers can adjust the mechanical properties of the waterproof coating. Through the synergistic effect of acrylate soft monomers and acrylate hard monomers, the waterproof coating is endowed with excellent physical and mechanical properties.

[0029] The emulsifier is selected from at least one of the following: polyvinyl alcohol derivatives containing oxime functional groups, polyvinyl alcohol (PVA), emulsifier OP-10, sodium dodecyl sulfate (SDS), and allyl sulfonate reactive emulsifiers (such as sodium allyl sulfonate). The oxime-functionalized polyvinyl alcohol derivatives are obtained by reacting polyvinyl alcohol with an aldehyde compound (such as acetaldehyde) and then with hydroxylamine; and / or by reacting polyvinyl alcohol with a dialdehyde compound (such as glutaraldehyde) and then with hydroxylamine. The initiator is selected from at least one of the following: ammonium persulfate (APS), potassium persulfate, and azobisisobutyramidine hydrochloride (V50). The use of the emulsifier serves three purposes: first, it reduces interfacial tension, allowing the aforementioned seed monomers to be uniformly dispersed in water as tiny droplets, forming a stable emulsion and ensuring the stability of the fluorocarbon emulsion product during storage; second, it guides the nucleation and directional polymerization of the seed monomers, forming a stable core-shell structure; and third, it helps improve the adhesion between the waterproof coating and the substrate interface, preventing detachment during use. The use of an initiator can initiate the polymerization of the aforementioned seed monomers. In the early stages of emulsion polymerization, the emulsifier can increase the contact area between the seed monomers and the initiator, thereby improving polymerization efficiency. As the polymerization reaction occurs, the initiator initiates the polymerization reaction inside or on the outer surface of the latex particles. At this time, the emulsifier can maintain the stability of the latex particles and prevent aggregation. In the later stages of emulsion polymerization, by controlling the ratio of emulsifier to initiator, the viscosity, solid content, and other properties of the finished fluorocarbon emulsion can be optimized.

[0030] The pH adjuster is AMP-95, CAS number: 124-68-5

[0031] The bactericides and preservatives are selected from isothiazolinones, such as methylisothiazolinone.

[0032] The defoamer is selected from silicone defoamers or polyether-modified defoamers. The silicone defoamer is selected from polydimethylsiloxane and its modified products, preferably hydrophobic silica-modified polydimethylsiloxane. The polyether-modified defoamer is selected from polyether-modified polysiloxane or fatty alcohol polyoxyethylene ether compounds.

[0033] According to an embodiment of the present invention, the method for preparing fluorocarbon emulsion includes steps A1-A4.

[0034] Step A1: Add water to the reactor, and after replacing the air in the reactor, raise the temperature to the first temperature.

[0035] Step A2: At the first temperature, an emulsifier and 3-10 wt% seed monomers are added to the reactor, and emulsion polymerization is carried out under the action of a partial initiator to obtain a fluorocarbon seed emulsion.

[0036] Step A3: Using a semi-continuous emulsion polymerization method, the remaining seed monomers and initiator are added to the fluorocarbon seed emulsion, the mixture is kept at a constant temperature and the emulsion polymerization reaction is carried out. After adjusting the pH to the first alkaline state, the fluorocarbon emulsion intermediate is obtained.

[0037] Step A4: Cool the fluorocarbon emulsion intermediate, add pH adjuster, defoamer and bactericide / preservative to obtain fluorocarbon emulsion.

[0038] Specifically, in step A1, after adding deionized water to the reactor, an inert gas (such as nitrogen or argon) is introduced under stirring conditions to remove dissolved oxygen from the reactor and prevent it from affecting the stability of the fluorocarbon emulsion. Subsequently, the temperature is raised to a first temperature of 70-80°C to provide reaction conditions for subsequent emulsion polymerization.

[0039] In step A2, an emulsifier is added to water to form a micelle solution. The seed monomer is then added and mixed uniformly with the micelle solution (e.g., mechanical or ultrasonic mixing). Under the initiation of an initiator, a fluorocarbon seed emulsion (i.e., latex ions, also simply "seeds") is formed. The pre-synthesized fluorocarbon seed emulsion can serve as the site for subsequent polymerization reactions. The seed monomer diffuses into the interior of the fluorocarbon seed emulsion or adsorbs onto its surface, undergoing chain growth reactions under the action of the initiator.

[0040] In step A3, after the fluorocarbon seed emulsion is formed, the remaining seed monomers are added at a constant rate over 1.5-2.0 hours using a semi-continuous feeding method to avoid excessively high local concentrations that could lead to aggregation. The remaining seed monomers contain furan-based and maleimide-based monomers, which, under the action of the initiator, form a shell structure rich in DA-based dynamic reversible covalent bonds on the surface of the fluorocarbon seed emulsion. During the emulsion polymerization in step A3, the initiator dosage is 0.3-1.5 wt% of the seed monomers (i.e., 0.3-1.5 wt% of initiator for 100 parts by weight of seed monomers). The initiator is added in batches, preferably in 2-4 batches, with each batch containing 20-40% of the total initiator. After all seed monomers have been added, the mixture is kept at a constant temperature for 30-60 minutes to complete the polymerization reaction, yielding a fluorocarbon emulsion intermediate with a core-shell structure.

[0041] In step A4, after forming the fluorocarbon emulsion with a core-shell structure, the system is cooled to 35-45°C. 0.1-1 parts by weight of a pH adjuster is added to adjust the pH of the emulsion to 7.0-8.5. Additionally, 0.1-0.5 parts by weight of a bactericide / preservative and 0.1-0.5 parts by weight of an antifoaming agent are added to ensure the stability of the fluorocarbon emulsion and prevent problems such as deterioration, spoilage, spoilage, mold growth, and discoloration due to microbial contamination. This also prevents the formation of large amounts of air bubbles during the preparation and application of the waterproof coating, which could affect the stability of the emulsion, the density of the coating film, and its corrosion resistance. Without pH adjustment, the residual acidic groups in the fluorocarbon emulsion can easily lead to particle aggregation, increased viscosity, and even demulsification during storage, which is detrimental to the storage stability of the emulsion and cannot guarantee subsequent film-forming performance.

[0042] According to embodiments of the present invention, the fluorocarbon emulsion prepared by the above method has a particle size of 100nm-300nm, a solid content of 35-50wt%, a Zeta potential of -25mV to -40mV, and a film-forming temperature of less than 40℃. The Zeta potential is an important parameter for evaluating the dispersion stability of the fluorocarbon emulsion system, and its absolute value directly reflects the electrostatic repulsion between emulsion particles. When the absolute value of the Zeta potential is low (usually less than 20mV), it indicates insufficient electrostatic repulsion between fluorocarbon emulsion particles, making them prone to flocculation and aggregation, leading to particle size increase, system stratification, and decreased storage stability. The present invention, by controlling the fluorocarbon emulsion formulation, enables the formation of a stable charged interface structure on the surface of the emulsion particles, maintaining the Zeta potential within the range of -25 to -40mV. This potential range corresponds to a strong electrostatic repulsion force, which can effectively inhibit the aggregation behavior of emulsion particles during storage, thereby reducing the particle size increase rate and improving the storage stability of the system. Therefore, fluorocarbon emulsions within the particle size, zeta potential, and solid content range provided by this invention can be uniformly dispersed, effectively preventing particle size growth and emulsion stratification during storage. Fluorocarbon emulsions can be uniformly distributed in waterproof coatings, achieving dynamic repair while enhancing mechanical properties; in some formulations, the tensile strength of the waterproof coating can reach 2.2 MPa, and the elongation at break can be increased to 170%.

[0043] In some embodiments, the microcapsule self-healing agent of the present invention has a core-shell structure, comprising a urea-formaldehyde resin shell and a fluorooil core material encapsulated within the urea-formaldehyde resin shell. The urea-formaldehyde resin shell is formed by the condensation of urea and formaldehyde into a hydroxymethyl urea prepolymer. The fluorooil core material is selected from at least one of perfluorooctyl ethyl acrylate and perfluorohexyl ethyl acrylate. The fluorooil core material of the present invention has similar surface energy and compatibility to fluorinated acrylate monomers, thereby enabling it to spread and form a continuous phase in the cracked areas of the waterproof coating, achieving the purpose of self-healing. Preferably, the fluorooil core material of the present invention uses the same material as the fluorinated acrylate monomer; more preferably, the fluorooil core material of the present invention preferably uses a perfluorooctyl ethyl acrylate oligomer.

[0044] In this invention, a waterproof coating is cured to form a waterproof layer, and the microcapsule self-healing agent is physically dispersed within the waterproof coating. When the waterproof coating is subjected to external force and cracks are generated, the urea-formaldehyde resin shell of the microcapsules ruptures, and the self-healing agent (i.e., fluorinated oil) embedded inside the urea-formaldehyde resin shell is released. The released fluorinated oil spreads in the crack area and forms a local low surface layer of continuous phase to fill the crack, enhancing hydrophobicity while achieving antifouling performance, thereby realizing the self-healing of the waterproof coating.

[0045] In some embodiments, the method for preparing microcapsule self-healing agents according to the present invention includes steps B1-B4.

[0046] Step B1: Under the second temperature and second alkaline conditions, urea is dissolved in water, formaldehyde solution is added, and a prepolymerization reaction is carried out to obtain a water-soluble hydroxymethyl urea prepolymer.

[0047] Step B2: Add fluorinated oil to an aqueous solution containing polyvinyl alcohol, mix well, and obtain fluorinated oil core material.

[0048] Step B3: Add the hydroxymethyl urea prepolymer to the fluorinated oil core material and carry out a polycondensation reaction under the third temperature and acidic conditions to obtain a microcapsule dispersion system.

[0049] Step B4: Cool the microcapsule dispersion system to room temperature and adjust the pH to the third alkaline state to obtain the microcapsule self-repairing agent.

[0050] Specifically, in step B1, the second temperature is 60-70°C and the second alkalinity is pH 8.0. Therefore, at 60-70°C, urea is dissolved in a portion of deionized water, 37wt% formaldehyde solution is slowly added, and the pH of the system is controlled at 8.0 with ammonia water so that the prepolymerization reaction can be carried out at this temperature and alkalinity for 20-30 minutes to generate water-soluble hydroxymethyl urea prepolymer.

[0051] In step B2, fluorinated oil is slowly added to an aqueous solution containing polyvinyl alcohol (PVA, used as a protective colloid) at a stirring speed of 1000-2000 rpm, and after mixing evenly, fluorinated oil core material is obtained.

[0052] In step B3, the hydroxymethyl urea prepolymer prepared in step B1 is slowly added to the fluorinated oil core material, and the pH is adjusted to 3-4 (third alkalinity) with acetic acid. Then, the mixture is stirred at 50-60℃ for 1.5-3 hours to carry out a polycondensation reaction. A cross-linked urea-formaldehyde (UF) resin shell is deposited in situ at the oil-water interface to encapsulate the fluorinated oil core material, thereby forming a suspended and stable microcapsule dispersion system.

[0053] In step B4, after the microcapsule dispersion system cools to room temperature, it is neutralized with ammonia to maintain the pH of the system at 7-8, so as to avoid residual acidic substances affecting the stability of the microcapsules in the waterproof coating, thereby obtaining the microcapsule self-healing agent.

[0054] According to embodiments of the present invention, the shell structure of fluorocarbon emulsions can be detected using Fourier transform infrared spectroscopy (FTIR), revealing the structural characteristic peaks of the reversible dynamic covalent bonds of DA, namely the CO absorption peak of imide (1710-1780 cm⁻¹). -1 The CO / C=C absorption peak of furan (1010-1600 cm⁻¹) -1 ), DA cycloaddition absorption peak of newly formed C-C bonds (1180-1230 cm⁻¹) -1 Differential scanning calorimetry (DSC) can detect the reversible endothermic peak (60-90℃) and closed-loop exothermic peak of DA. This invention can also confirm that the DA structure is located in the shell region of the fluorocarbon emulsion using transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy.

[0055] According to embodiments of the present invention, the elemental composition of the microcapsule self-healing agent can be detected by X-ray photoelectron spectroscopy (XPS), where the F1s peak (689-693 eV) indicates the presence of a fluoropolymer core material. Further characterization of the wall material by Fourier transform infrared spectroscopy (FTIR) reveals characteristic absorption peaks of urea-formaldehyde resin, including the C=O stretching vibration peak (approximately 1650-1720 cm⁻¹). -1 CN stretching vibration peak (approximately 1400-1550 cm⁻¹) -1 ) and the NH stretching vibration peak (approximately 3200-3500 cm⁻¹) -1 In addition, a weak COC absorption peak (approximately 1100-1150 cm⁻¹) was observed in some samples. -1 This is attributed to the ether bond structure formed during the polycondensation process.

[0056] According to embodiments of the present invention, the water resistance and interfacial adhesion of the waterproof coating are enhanced by adding a water-resistant agent to the waterproof coating. The water-resistant agent used in this invention is selected from at least one of epoxy-based silane oligomers and silane coupling agents. For example, the epoxy-based silane oligomer is selected from LD3168 of Lida Chemicals; the silane coupling agent is selected from γ-glycidyl etheroxypropyltrimethoxysilane (KH-560, CAS: 2530-83-8), such as Momentive silane coupling agent coatosil MP200.

[0057] According to embodiments of the present invention, by adding a film-forming aid to the waterproof coating, the film-forming temperature of the waterproof coating is lowered, enabling it to form a film rapidly at room temperature. The film-forming aid of the present invention is selected from at least one of dodecyl alcohol ester and dipropylene glycol butyl ether.

[0058] According to embodiments of the present invention, a stabilizer is added to improve the dispersibility of the waterproof coating, thicken and aid sedimentation, and enhance the storage stability of the finished product. The stabilizer used in this invention is selected from at least one of 2-amino-2-methyl-1-propanol and silane-modified pH adjusters, such as AMP-95 and Wacker's deodorizing pH adjuster SILRES® BS 168.

[0059] According to embodiments of the present invention, by adding bactericides and preservatives to waterproof coatings, problems such as deterioration and delamination caused by microbial contamination during the production, storage, and use of the waterproof coatings are prevented, thereby ensuring the performance (such as waterproofing, self-healing, and weather resistance) and service life of the waterproof coatings. Specifically, the bactericides and preservatives used in the present invention are selected from isothiazolinone bactericides and preservatives, such as at least one of 1,2-benzisothiazolin-3-one (BIT), 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT), and 2-methyl-4-isothiazolin-3-one (also known as methylisothiazolinone, MIT).

[0060] As a second aspect of the present invention, a method for preparing an exposed single-component waterproof coating with self-healing function is provided, comprising: adding fluorocarbon emulsion, water-resistant agent, film-forming aid, and stabilizer into a reactor and mixing them evenly to form a base material; adding microcapsule self-healing agent, bactericide and preservative and the balance water to the base material to obtain a single-component waterproof coating.

[0061] For example: Based on a total weight of 100%, add 25-50 wt% of fluorocarbon emulsion, 0.1-1 wt% of water-resistant agent, 0.1-3 wt% of film-forming aid, and 0.1-wt% of stabilizer to a dispersion vessel (i.e., reactor). Start a high-speed disperser and disperse at 400-500 rpm for 10-30 minutes to form a base material. Reduce the speed to 300-400 rpm and add 5-20 wt% of microcapsule self-healing agent to the base material. Disperse for 10-30 minutes, then add 0.1-1 wt% of bactericide and preservative and the remaining water. Continue stirring for 10-30 minutes to obtain a single-component waterproof coating.

[0062] In the preparation of the waterproof coating of this invention, microcapsule self-healing agents and other additives (i.e., water-resistant agents, film-forming aids, stabilizers, bactericides, and preservatives) can be added to the fluorocarbon emulsion and mixed evenly with water. This method for preparing an exposed, single-component waterproof coating is simple, reduces the complexity and energy consumption of synthesizing waterproof coatings, and facilitates industrial application. Furthermore, the waterproof coating of this invention can be prepared and used immediately, or it can be prepared and stored for a period of time before use.

[0063] As a third aspect of the present invention, the application of the above-mentioned exposed single-component waterproof coating in the field of building protection is provided.

[0064] Specifically, the waterproof coating of this invention is suitable for metal roofs, exterior walls, waterproofing projects, and building coatings requiring high weather resistance. As a waterproof coating, this invention can significantly extend the service life of waterproof coatings and reduce maintenance costs. Furthermore, the waterproof coating of this invention has excellent self-healing capabilities and is expected to be used in high-elasticity building coatings, industrial anti-corrosion coatings, and other fields, enhancing the added value and market competitiveness of waterproof coatings (including fluorocarbon emulsions and microcapsule self-healing agents).

[0065] The technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0066] Preparation of fluorocarbon emulsions

[0067] 70 g of deionized water was added to the reactor, and nitrogen gas was purged for 30 min under stirring (300 rpm) to remove dissolved oxygen from the system. The temperature was then raised to 80 °C. At this temperature, an aqueous solution of 1.0 g of oxime-modified polyvinyl alcohol emulsifier (approximately 2.2 wt% of the total monomer) and 3 wt% (approximately 1.4 g) of seed monomer were added. Seed emulsion polymerization was initiated by 0.12 g of ammonium persulfate (approximately 0.26 wt% of the total seed monomer) for 20 min to form a stable fluorocarbon seed emulsion. After the formation of the fluorocarbon seed emulsion, the remaining monomer (approximately 44.6 g) was added dropwise to the reaction system at a constant rate over 1.5 h using a semi-continuous feeding method. Simultaneously, the remaining initiator, totaling 0.28 g, was added in three separate additions of 0.10 g, 0.10 g, and 0.08 g, with an interval of 30 min between additions, to maintain a stable free radical concentration in the system. After the seed monomers were added, the reaction was continued at a constant temperature for 45 minutes to improve the monomer conversion rate. After the reaction was completed, the system was cooled to 40°C, and ammonia was added to adjust the pH to 7.5. Then, 0.2 g of the bactericidal and preservative BIT (1,2-benzisothiazolin-3-one) and 0.2 g of the organosilicon defoamer (polydimethylsiloxane) were added, and the mixture was stirred evenly to obtain a stable fluorocarbon emulsion with a core-shell structure.

[0068] Preparation of microcapsule self-healing agents

[0069] At 60℃, 20g of urea was dissolved in 200g of deionized water, and 45g of 37wt% formaldehyde solution was slowly added. The pH of the system was adjusted to 8.0 with ammonia under stirring, and the reaction was continued at this temperature for 25min to obtain hydroxymethyl urea prepolymer. Separately, 300g of a 1wt% polyvinyl alcohol (PVA) aqueous solution (containing 3g of PVA) was slowly added to 100g of perfluorooctyl ethyl acrylate under stirring at 1500rpm, and emulsified for 20min to obtain a stable oil-water emulsion system as the core material dispersion system (i.e., fluorooil core material). Subsequently, the above hydroxymethyl urea prepolymer was slowly added to the fluorooil core material, and the pH of the system was adjusted to 3.8 with acetic acid under stirring. The reaction was continued at 55℃ for 2h, allowing the hydroxymethyl urea prepolymer to undergo a condensation reaction at the oil droplet interface to form a urea-formaldehyde resin shell, thus obtaining a microcapsule dispersion system. After the reaction was completed, the system was cooled to room temperature and the pH was adjusted to 7.0 with ammonia. After washing with deionized water, it was stored in suspension to obtain a stable microcapsule self-healing agent.

[0070] Other raw materials

[0071] Water-resistant agent: LD3168 epoxy silane oligomer (Lida Chemical) is used.

[0072] Film-forming aid: Dodecyl alcohol ester is used.

[0073] Stabilizer: 2-amino-2-methyl-1-propanol is used.

[0074] Bactericide and preservative: BIT is used.

[0075] Preparation of waterproof coatings

[0076] Different exposed single-component waterproof coatings were prepared using the above-mentioned raw materials. The specific method for preparing the waterproof coatings is as follows: based on a total weight of 100%, fluorocarbon emulsion water-resistant agent, film-forming aid, and stabilizer were added to the dispersion vessel, and a high-speed disperser was started and dispersed at a speed of 500 rpm for 10 minutes to form a base material; the speed was reduced to 400 rpm and microcapsule self-healing agent was added to the base material and dispersed for 30 minutes, then bactericide and preservative and the remaining water were added, and stirring was continued for 10 minutes to obtain the single-component waterproof coating.

[0077] The specific formulations of different waterproof coatings by weight percentage are shown in Table 1. Among them, Examples 1-3 and Comparative Example 1 were prepared using the above method to prepare fluorocarbon emulsions and microcapsule self-healing agents. The fluorocarbon emulsion in Comparative Example 2 was prepared using the same formulation and emulsion polymerization process as in Example 1. The difference is that furan-structured monomers and maleimide-structured monomers were not used.

[0078] Table 1. Formulations of different waterproof coatings

[0079]

[0080] The performance of the different waterproof coatings prepared in Examples 1-3 and Comparative Examples 1-2 was tested. The specific test methods and test results are shown in Tables 2-4 below.

[0081] 1. Self-healing rate test

[0082] Standard coating samples with a thickness of 1 mm were prepared from the above different waterproof coatings and cured for 7 days (d) at 25℃ and 50% relative humidity. Standard cracks were prepared in the middle of the coating samples using a blade, and then the samples were left to stand at 25℃ for 24 hours.

[0083] Calculate the self-healing rate using the following formula:

[0084] Self-healing rate = (Tensile strength after repair / Initial tensile strength) * 100%

[0085] 2. Cyclic self-healing rate

[0086] Repeat the following process for the same sample: crack preparation → self-healing → tensile testing, for three consecutive cycles.

[0087] 3. Crack closure rate

[0088] The crack width was measured using a graduated optical magnifying glass and calculated as follows: Crack closure rate = (Initial crack width - Repaired crack width) / Initial crack width * 100%.

[0089] Table 2. Self-healing rate

[0090]

[0091] As shown in Table 2, the self-healing rate of the waterproof coatings using this invention is above 70%, which is significantly higher than that of the comparative examples without microcapsule self-healing agents. Specifically, under the same fluorocarbon emulsion dosage (comparing Example 3 and Comparative Example 1), the self-healing ability of the waterproof coating significantly decreased without the introduction of microcapsule self-healing agents, indicating that the self-healing function of the fluorocarbon emulsion itself is poor. With the increase in the dosage of microcapsule self-healing agents, the self-healing rate of the waterproof coating shows a significant upward trend and maintains a high repair efficiency even under damaged conditions.

[0092] Table 3. Cyclic Self-Healing Rate

[0093]

[0094] As shown in Table 3, compared with the waterproof coating containing only fluorocarbon emulsion in Comparative Example 1, the waterproof coating formed by curing the waterproof coating in Example 3 has a higher self-healing rate and cyclic self-healing rate. This indicates that there is a synergistic repair mechanism between the DA reversible dynamic covalent bond of the fluorocarbon emulsion shell layer and the microcapsule self-repairing agent, rather than a simple physical superposition effect.

[0095] Table 4. Crack Closure Rate

[0096]

[0097] As shown in Table 4, the waterproof coating of the present invention has a higher crack closure rate than Comparative Example 1, which also proves that there is a synergistic mechanism between fluorocarbon emulsion and microcapsule self-healing agent.

[0098] In summary, a dual-mechanism self-healing and waterproof coating is constructed by introducing a reversible dynamic covalent bond network structure (i.e., the Diels–Alder / Michael addition system) into a fluorocarbon emulsion and combining it with a microcapsule self-healing agent containing a fluorinated oil core material. When the waterproof coating suffers microcracks or pinhole damage, the shell of the microcapsule self-healing agent ruptures, releasing the fluorinated oil core material. Simultaneously, the reversible dynamic covalent bonds of DA flow and fill the cracks in localized areas, achieving rapid self-healing. The waterproof coating prepared using the formulation of this invention, after curing, achieves a healing rate of over 90%, and the cyclic healing rate remains at 50–75% even after multiple damages, significantly improving the durability and service life of the waterproof coating.

[0099] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An exposed type one-component waterproof paint having a self-repairing function, characterized by, Based on a total weight percentage of 100 wt%, it includes: 25-50 wt% fluorocarbon emulsion, 5-20 wt% microcapsule self-healing agent, 0.1-1 wt% water-resistant agent, 0.1-3 wt% film-forming aid, 0.1-1 wt% stabilizer, 0.1-1 wt% bactericide and preservative, balance water; The fluorocarbon emulsion is a core-shell polymer emulsion. The outer shell is formed by emulsion polymerization of fluorinated acrylate monomers, furan-structured monomers, and maleimide-structured monomers, while the core is formed by emulsion polymerization of soft acrylate monomers and hard acrylate monomers. Both emulsion polymerizations are carried out in an aqueous solution containing emulsifiers and initiators. The microcapsule self-healing agent has a core-shell structure, including a urea-formaldehyde resin shell and a fluorinated oil core material encapsulated within the urea-formaldehyde resin shell.

2. The exposed single-component waterproof coating according to claim 1, characterized in that: The water-resistant agent is selected from at least one of epoxy silane oligomers and silane coupling agents; The film-forming aid is selected from at least one of dodecyl alcohol ester and dipropylene glycol butyl ether; The stabilizer is selected from at least one of 2-amino-2-methyl-1-propanol and silane-modified pH adjusters; The bactericide and preservative are selected from isothiazolinone bactericides and preservatives.

3. The exposed one-component waterproofing coating according to claim 1, characterized in that, The raw materials for preparing the fluorocarbon emulsion include: seed monomers, additives, and water; The seed monomers, in a total weight of 100 parts, include: 20-55 parts of fluorinated acrylate monomers, 15-45 parts of soft acrylate monomers, 10-35 parts of hard acrylate monomers, 2-15 parts of furan structure monomers, and 0.5-5 parts of maleimide structure monomers. Based on a total weight of 100 parts of the seed monomers, the adjuvants include: 1-5 parts of emulsifier, 0.3-1.5 parts of initiator, 0.1-1 parts of pH adjuster; 0.1-0.5 parts of defoamer; and 0.1-0.3 parts of bactericide and preservative. Water is used in quantities of 80-200.

4. The exposed one-component waterproofing coating according to claim 3, characterized in that, The fluorocarbon emulsion is obtained by the following method: Step A1: Add water to the reactor, and after replacing the air in the reactor, raise the temperature to the first temperature; Step A2: At the first temperature, the emulsifier and 3-10 wt% of seed monomers are added to the reactor, and emulsion polymerization is carried out under the action of a partial initiator to obtain a fluorocarbon seed emulsion; Step A3: Using a semi-continuous emulsion polymerization method, the remaining seed monomers and initiator are added to the fluorocarbon seed emulsion, the mixture is kept at a constant temperature and the emulsion polymerization reaction is carried out. After adjusting the pH to the first alkaline state, the fluorocarbon emulsion intermediate is obtained. Step A4: Cool the fluorocarbon emulsion intermediate, add pH adjuster, defoamer and bactericide / preservative to obtain fluorocarbon emulsion.

5. The exposed one-component waterproofing coating according to claim 1 or 3, characterized in that, In the fluorocarbon emulsion: The fluorinated acrylate monomers include fluorinated vinyl acrylate monomers, selected from any one of perfluorooctyl ethyl acrylate and perfluorohexyl ethyl acrylate; The furan-structured monomer is a polymerizable monomer containing a furan ring, selected from any one of 2,5-bis(hydroxymethyl)furan, furfuryl alcohol-modified acrylates, and methacrylate compounds; The maleimide-type monomer is selected from either N,N'-(1,3-phenylene)dimaleimide or 4,4'-bismaleimide diphenylmethane. The acrylate soft monomer is selected from at least one of butyl acrylate, 2-ethylhexyl acrylate or isooctyl acrylate; The acrylate hard monomer is selected from at least one of methyl methacrylate, styrene-acrylate copolymer, and isobornyl acrylate; The emulsifier is selected from at least one of the following: polyvinyl alcohol derivatives containing oxime functional groups, polyvinyl alcohol, emulsifier OP-10, sodium dodecyl sulfate, and allyl sulfonate reactive emulsifiers; The initiator is selected from at least one of ammonium persulfate, potassium persulfate, and azobisisobutyramidine hydrochloride.

6. The exposed one-component waterproofing coating according to claim 1, characterized in that, In the microcapsule self-healing agent: The urea-formaldehyde resin shell is formed by the condensation of urea and formaldehyde hydroxymethyl urea prepolymer. The fluorinated core material is selected from at least one of perfluorooctyl ethyl acrylate and perfluorohexyl ethyl acrylate.

7. The exposed single-component waterproof coating according to claim 1 or 6, characterized in that, The microcapsule self-healing agent is obtained by the following method: Under the second temperature and second alkaline conditions, urea is dissolved in water, formaldehyde solution is added, and a prepolymerization reaction is carried out to obtain a water-soluble hydroxymethyl urea prepolymer. Fluorinated oil is added to an aqueous solution containing polyvinyl alcohol and mixed evenly to obtain fluorinated oil core material; The hydroxymethyl urea prepolymer was added to the fluorinated oil core material, and a polycondensation reaction was carried out under a third temperature and acidic conditions to obtain a microcapsule dispersion system. The microcapsule dispersion system was cooled to room temperature and the pH was adjusted to the third alkaline state to obtain the microcapsule self-healing agent.

8. The exposed single-component waterproof coating according to claim 1, characterized in that, The fluorocarbon emulsion has a particle size of 100nm-300nm, a solid content of 35-50wt%, a zeta potential of -25mV to -40mV, and a film-forming temperature of less than 40℃.

9. The method for preparing an exposed single-component waterproof coating as described in any one of claims 1-8, characterized in that, include: Add fluorocarbon emulsion, water-resistant agent, film-forming aid, and stabilizer to the reactor and mix them evenly to form a base material; Microcapsule self-healing agent, bactericide and preservative, and the balance of water are added to the base material to obtain a single-component waterproof coating.

10. The application of the exposed single-component waterproof coating as described in any one of claims 1-8 in the field of building protection.

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