Oily woodware protective finish paint with self-repairing function and preparation method thereof

Abstract

The invention belongs to the field of finish paint, and particularly relates to oily woodware protection finish paint with a self-repairing function and a preparation method thereof. The oily woodware protective finishing paint is composed of a component A and a component B, the component A comprises modified alkyd resin containing dynamic disulfide bonds and epoxy resin-based latent curing microcapsules; a core material of the epoxy resin-based latent curing microcapsule comprises epoxy resin and a latent curing agent, and a wall material of the epoxy resin-based latent curing microcapsule is polyurethane; the component B is an isocyanate curing agent; the weight ratio of the component A to the component B is (5-7): 1. According to the oily woodware protection finishing paint, dynamic disulfide bonds are successfully introduced into the oily alkyd resin; a high-performance microcapsule based on an epoxy resin chemical curing system is creatively designed and applied, and full-scale and high-adhesion self-repairing from microcracks to deep scratches is achieved.

Description

Technical Field

[0001] This invention belongs to the field of topcoats, specifically an oil-based wood protective topcoat with self-healing function and its preparation method. Background Technology

[0002] While oil-based paints applied to wood surfaces are hard and wear-resistant, they have a persistent drawback: once scratched, the marks are permanent and cannot self-repair. This not only affects aesthetics but also reduces their protective function. Mechanical damage (such as scratches) to wood paints is the main reason for their performance degradation and decreased appearance. Self-healing coatings represent an important development direction in the field of functional coatings. By introducing responsive repair mechanisms within the material, they endow the coating with the ability to self-heal from damage, thereby extending its service life.

[0003] As described in prior art CN 120795761 B, a high-performance solvent-free blade wear-resistant self-healing topcoat and its preparation method are provided. The high-performance solvent-free blade wear-resistant self-healing topcoat of this invention constructs a rigid and tough cross-linked network by introducing POSS-isocyanate nano-hybrids and modified polyaspartic acid ester, solving the interfacial incompatibility problem of traditional physical blend coatings. Simultaneously, it endows the coating with excellent wear resistance, strong adhesion, and micro-scratch self-healing ability. This topcoat is a solvent-free system, environmentally friendly, and has good application performance, effectively extending blade life.

[0004] However, current research on repairable protective topcoats for oil-based wood is limited. On one hand, existing repair agents can only address micro-cracks on the surface; the resulting repairs have low mechanical strength and are incompatible with the properties of high-performance oil-based coatings, affecting adhesion and leaving noticeable repair marks. On the other hand, achieving macro-level repair while maintaining coating performance remains a technical challenge. Therefore, developing a new technology capable of repairing everything from micro-cracks to deep scratches, and applicable to oil-based wood coating systems, is of significant value. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention proposes an oil-based wood protective topcoat with self-healing capabilities, which successfully introduces dynamic disulfide bonds into oil-based alkyd resins; and innovatively designs and applies a high-performance microcapsule based on an epoxy resin chemical curing system. These two components work synergistically to achieve full-scale, high-adhesion self-healing from microcracks to deep scratches.

[0006] On the one hand, the present invention proposes an oil-based wood protective topcoat with self-healing function, which is composed of component A and component B; Component A includes a modified alkyd resin containing dynamic disulfide bonds and epoxy resin-based latent curing microcapsules; the epoxy resin-based latent curing microcapsules have an epoxy resin core and a latent curing agent, and a polyurethane wall material. Component B is an isocyanate curing agent; The weight ratio of component A to component B is (5-7):1.

[0007] A further improvement to this scheme is that, based on the total weight of component A, the content of the modified alkyd resin containing dynamic disulfide bonds is 50-70 parts, the content of the epoxy resin-based latent curing microcapsules is 4-8 parts, and component A further includes 0.5-1.5 parts of wetting and dispersing agent, 0.2-0.8 parts of defoamer, and 20-35 parts of first organic solvent.

[0008] A further improvement to this scheme is the preparation method of the modified alkyd resin containing dynamic disulfide bonds as follows: under the protection of an inert gas, polyols, polyacids and fatty acids are subjected to esterification and polycondensation reaction to form an alkyd resin prepolymer; in the middle or late stage of the reaction, a chain extender containing disulfide bonds is added to continue the reaction, so that the dynamic disulfide bonds are chemically incorporated into the alkyd resin molecular chain.

[0009] Preferably, the chain extender of the disulfide bond is one or more of 2-hydroxyethyl disulfide and 4,4'-dithiobenzoic acid, and its addition amount accounts for 2-6 wt% of the resin solids.

[0010] The method for preparing the modified alkyd resin containing dynamic disulfide bonds is as follows: In a reactor, add 8-12 parts by weight of polyol, 20-28 parts by weight of polyacid, 10-16 parts by weight of fatty acid and 5-8 parts by weight of reflux solvent, introduce inert gas, and heat to 180-200℃ to carry out esterification reaction until the acid value is 8-12 mgKOH / g; cool to 120-140℃, add 2-6wt% of disulfide bond chain extender of resin solids, and keep the reaction at this temperature for 2-3 hours; cool to below 80℃, add a second organic solvent to adjust the solid content to 70±5%, and filter to discharge the material.

[0011] The polyol is one or more of pentaerythritol, trimethylolpropane, and glycerol; the polyacid is one or more of isophthalic acid and adipic acid; and the fatty acid is one or more of soybean oil fatty acid, linolenic acid, and coconut oil fatty acid.

[0012] A further improvement to this scheme is the preparation method of the epoxy resin-based latent curing microcapsules as follows: Epoxy resin, latent curing agent, and epoxy reactive diluent are mixed to obtain an oil phase; polyvinyl alcohol and anionic surfactant are dissolved in deionized water to obtain a homogeneous aqueous phase; the obtained oil phase is added to the obtained aqueous phase and emulsified by high-speed shearing to obtain a fine emulsion; wall material reactants dissolved in a third organic solvent are added to the fine emulsion; after the reaction is completed, powdered microcapsules are prepared; the average particle size D50 of the microcapsules is 8-15 micrometers.

[0013] Preferably, the epoxy resin-based latent curing microcapsules are prepared as follows: a) Preparation of core material oil phase: 60-70 parts by weight of bisphenol A type epoxy resin and / or bisphenol F type epoxy resin, 30-40 parts by weight of dicyandiamide and / or its derivatives are mixed with 1-5 parts by weight of epoxy reactive diluent and stirred at 35-40℃ until uniform to obtain oil phase. b) Aqueous phase preparation: Dissolve 1-3 parts by weight of polyvinyl alcohol and 0.5-1.5 parts by weight of anionic surfactant in 200 parts by weight of deionized water, and heat to 50-55℃ to obtain a homogeneous aqueous phase. c) Emulsification: Add the oil phase obtained in step a) to the aqueous phase obtained in step b), and emulsify at 6000-8000 rpm for 5-8 minutes at 50±2℃, and then perform high-pressure homogenization cycling at 40-60 MPa for 2-4 times to obtain a fine emulsion. d) Interfacial polymerization: The fine emulsion is transferred to the reactor and stirred at 50±2℃ and 400-600 rpm. The wall material reactant dissolved in the third organic solvent is slowly added dropwise to the system over 30-45 minutes. The wall material reactant dissolved in the third organic solvent consists of 8-12 parts by weight of PPG-220 or / and PPG-2000, 6-10 parts by weight of HDI trimer, and 10-15 parts by weight of the third organic solvent acetone. e) Curing and post-treatment: After the addition is completed, the temperature is raised to 65±2℃ and the reaction continues for 4-5 hours; after the reaction is completed, the mixture is cooled, washed, and filtered. The resulting solid is vacuum dried at 40-45℃ for 24-36 hours, pulverized and sieved to obtain powdered microcapsules.

[0014] In a further improvement to this scheme, the isocyanate curing agent is one or more of HDI trimer, HDI biuret, and IPDI trimer.

[0015] Secondly, the present invention provides a method for preparing the above-mentioned oil-based wood protective topcoat, comprising the following steps: By weight, 50-70 parts of modified alkyd resin containing dynamic disulfide bonds, 4-8 parts of epoxy resin-based latent curing microcapsules, 0.5-1.5 parts of wetting and dispersing agent, and 0.2-0.8 parts of defoamer are dispersed at 400-600 rpm for 10-20 minutes; then 20-35 parts of the first organic solvent are added to adjust the viscosity to 80-120 seconds at a Fore-4 cup, and the mixture is filtered to obtain component A. Mix component A with isocyanate curing agent at a weight ratio of (5-7):1 until homogeneous, cure, apply to the wood surface, and cure.

[0016] The beneficial effects of this invention are as follows: (1) The modified alkyd resin containing dynamic disulfide bonds in this invention forms a reversible dynamic cross-linking network, which can spontaneously and repeatedly heal micro-scratches under external stress or mild heat stimulation through the exchangeability of disulfide bonds. At the same time, the epoxy resin-based latent curing microcapsules, as high-performance repair units, can rupture when the coating suffers macroscopic deep scratches. The released epoxy resin and latent curing agent undergo chemical cross-linking after being triggered to form a high-strength, high-adhesion solid repair, achieving permanent filling of macroscopic damage. The dual repair targets damage at different scales, forming a complementary and complete repair system.

[0017] (2) This invention, through precise molecular design and formulation control, ensures that the introduction of self-healing function does not come at the expense of the traditional excellent performance of the coating film. By modifying the alkyd resin, employing interfacial polymerization technology for the microcapsule wall material, and precisely controlling the curing ratio of components A and B, the final cured coating maintains the inherent excellent adhesion of polyurethane paint while possessing outstanding self-healing capabilities. The performance of the self-healing component matches that of the base resin, achieving a balance between functionality and protection. This invention is highly practical and easily scalable for industrial production and market promotion. Detailed Implementation

[0018] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0019] This application discloses an oil-based wood protective topcoat with self-healing function, which is composed of component A and component B.

[0020] Component A includes modified alkyd resin containing dynamic disulfide bonds and epoxy resin-based latent curing microcapsules; the epoxy resin-based latent curing microcapsules have an epoxy resin core and a latent curing agent, and a polyurethane wall material.

[0021] The dynamic disulfide bonds (-SS-) in the main chain of modified alkyd resin can undergo reversible breakage and exchange reactions when stimulated by stress and heat. This enables the resin molecular network to achieve topological restructuring at microscopic damage sites, thereby automatically and repeatedly repairing shallow scratches at the micrometer level and below, achieving primary repair at the molecular scale.

[0022] When the damage is deep enough to reach the microcapsule, the capsule wall ruptures, and the epoxy resin and latent curing agent in the core material flow out and mix. The latent curing agent is activated, initiating chemical cross-linking and curing of the epoxy resin at the damaged site, forming a robust, three-dimensional network structure epoxy resin restoration, achieving primary repair at the macroscale.

[0023] Simultaneously, the alkyd resin matrix containing dynamic disulfide bonds exhibits a certain degree of molecular activity at the repair interface, which helps alleviate stress concentration and promotes the formation of a stronger interpenetrating or anchoring structure between the repair and the old paint film, thus achieving repair. The high hardness, strong adhesion, and excellent solvent resistance of epoxy resin cured products are highly compatible with the matrix properties of oil-based polyurethane topcoats, resulting in minimal differences in the physicochemical properties between the repaired area and the original paint film.

[0024] Component B is an isocyanate curing agent; it reacts with the hydroxyl groups (-OH) of the modified alkyd resin in component A to form a cross-linked network structure, giving the paint film high hardness, high wear resistance, and chemical resistance. Furthermore, the cross-linking reaction forms a stable but locally mobile network from the resin segments containing dynamic disulfide bonds, ensuring that microcracks can heal without the paint film becoming loose overall.

[0025] The preferred isocyanate curing agents are HDI trimer, HDI biuret, and IPDI trimer.

[0026] The weight ratio of component A to component B is (5-7):1, such as 5:1, 5.5:1, 6:1, 6.5:1, or 7:1. This range allows for the formation of a polymer network with moderate crosslinking density, exhibiting both rigidity and localized chain segment mobility. This network structure provides the necessary micro-region mobility for the reversible exchange of dynamic disulfide bonds, ensuring the realization of self-healing function. Furthermore, it avoids film softening due to insufficient crosslinking or film embrittlement due to excessive crosslinking, thus endowing the coating with excellent self-healing capabilities while ensuring the hardness, adhesion, and durability necessary for a high-performance topcoat.

[0027] Of which, based on the total weight of component A, the content of the modified alkyd resin containing dynamic disulfide bonds is 50-70 parts, such as 50 parts, 55 parts, 60 parts, 65 parts, or 70 parts; and the content of the epoxy resin-based latent curing microcapsules is 4-8 parts, such as 4 parts, 5 parts, 6 parts, 7 parts, or 8 parts. Component A also includes 0.5-1.5 parts of wetting and dispersing agent (such as 0.5, 0.7, 0.9, 1.0, 1.2, or 1.5 parts), 0.2-0.8 parts of defoamer (such as 0.2, 0.4, 0.5, 0.6, or 0.8 parts), and 20-35 parts of a first organic solvent (such as 20, 25, 30, or 35 parts).

[0028] The content of modified alkyd resin containing dynamic disulfide bonds, at 50-70 parts, ensures that the resin, while fulfilling its basic film-forming function, provides a scientifically reasonable proportioning space for other key components of the entire functional coating system. The content of epoxy resin-based latent curing microcapsules, at 4-8 parts, guarantees the reliability of the repair and ensures a sufficiently dense distribution of microcapsules within the coating film. Simultaneously, it maintains the mechanical properties of the coating film: as embedded particles, excessive addition of microcapsules can disrupt the continuous resin matrix, creating stress defect points and leading to a significant decrease in key mechanical properties such as film hardness, adhesion, and impact resistance.

[0029] For wetting and dispersing agents, BYK-163 or TEGO Dispers 750 can be used. Ensure stable dispersion of components in the solvent and prevent aggregation and sedimentation.

[0030] Defoamers such as BYK-066N or TEGO Airex 902W can be used. These suppress the formation of bubbles during production and construction, and promote the rapid collapse of existing bubbles.

[0031] The first organic solvent can be xylene, butyl acetate, or propylene glycol methyl ether acetate. These solvents can dissolve the resin, adjust the application viscosity, and control the evaporation rate to achieve ideal leveling properties. The mixture should be formulated according to the solubility parameters of the modified alkyd resin to ensure workability while avoiding premature activation of the microcapsules due to excessively rapid evaporation.

[0032] The method for preparing the modified alkyd resin containing dynamic disulfide bonds is as follows: under the protection of an inert gas, polyols, polyacids and fatty acids are subjected to esterification and polycondensation reaction to form an alkyd resin prepolymer; in the middle or late stage of the reaction, a chain extender containing disulfide bonds is added to continue the reaction, so that the dynamic disulfide bonds are chemically incorporated into the alkyd resin molecular chain.

[0033] The polyol can be one or more of pentaerythritol, trimethylolpropane, and glycerol; the polyacid can be one or more of isophthalic acid and adipic acid; and the fatty acid can be one or more of soybean oil fatty acid, linolenic acid, and coconut oil fatty acid.

[0034] The chain extender containing disulfide bonds is one or more of 2-hydroxyethyl disulfide (CAS No.: 1892-29-1) and 4,4'-dithiobenzoic acid (CAS No.: 1155-51-7), and its addition amount accounts for 2-6 wt% of the theoretical solids of the resin. The solids refer to the total mass of the polyols, polyacids, fatty acids, and the chain extender itself that constitute the resin, excluding the solvents used in the process.

[0035] Specifically, the preparation method of the modified alkyd resin containing dynamic disulfide bonds is as follows: In a reactor, add 8-12 parts by weight of polyol, 20-28 parts by weight of polyacid, 10-16 parts by weight of fatty acid, and 5-8 parts by weight of reflux solvent (xylene or propylene glycol methyl ether acetate). Inert gas (preferably nitrogen) is introduced, and the temperature is raised to 180-200℃ to carry out esterification reaction until the acid value is 8-12 mgKOH / g. The temperature is lowered to 120-140℃, and a disulfide bond chain extender containing 2-6 wt% of the resin solids is added. The reaction is maintained for 2-3 hours. The temperature is lowered to below 80℃, and a solvent (propylene glycol methyl ether acetate or butyl acetate) is added to adjust the solid content to 70±2%. The mixture is then filtered and discharged.

[0036] This preparation method first involves the esterification of a polyol (taking pentaerythritol as an example) with a polyacid (taking phthalic acid as an example): the hydroxyl groups (-OH) of pentaerythritol undergo dehydration condensation with the carboxyl groups (-COOH) of phthalic acid to form ester bonds (-O-CO-). This is a condensation reaction, in which the molecular chain continuously grows, generating a branched polyester backbone. The carboxyl groups of fatty acids (such as soybean oil fatty acids) also react with the hydroxyl groups of pentaerythritol, becoming attached as monoesters. Its long-chain structure acts as an internal plasticizer, changing the rigid structure of the polyester chain, thus giving the final resin and paint film the necessary flexibility. Then, a chain extender containing disulfide bonds, as a small molecule, undergoes a further esterification condensation reaction with the active functional groups at the ends of the prepolymer synthesized in the first step.

[0037] Through this reaction, the chain extender links two or more alkyd resin prepolymer molecular chains together, while simultaneously permanently integrating dynamic disulfide bonds (-SS-) into the polymer network backbone of the entire resin in the form of strong chemical bonds (ester bonds). This forms a polymer resin with a flexible modified polyester (alkyd resin) as the main chain, long fatty acid chains as side chains, and dynamic disulfide bond functional segments embedded in the main chain or branches. When the paint film is damaged and microcracks occur, the embedded disulfide bonds (-SS-) can undergo reversible breakage-exchange-recombination under stress or weak heat stimulation. This dynamic exchange allows molecular chain segments to migrate and recombine at the damage interface, thereby achieving self-healing of microcracks.

[0038] Acid value indicates the content of residual free carboxyl groups in the system. When the acid value drops to 8-12 mgKOH / g, controlling the acid value within this range makes the degree of reaction controllable. At this point, the esterification reaction is basically complete, but not completely. A certain amount of hydroxyl or carboxyl groups are still retained at the end of the prepolymer molecular chain, providing active sites for the next reaction with the chain extender.

[0039] The purpose of cooling the reaction to 120-140℃ is twofold: firstly, to protect the disulfide bonds, which are prone to thermal decomposition or side reactions at the higher esterification temperature (180-200℃) in the first step. Chain extension at a moderate temperature ensures the integrity of the disulfide bonds; secondly, to ensure reactivity: this temperature is sufficient to drive the esterification reaction between the chain extender and the terminal carboxyl group of the prepolymer to proceed smoothly, while suppressing side reactions.

[0040] The preparation method of the epoxy resin-based latent curing microcapsules is as follows: epoxy resin, latent curing agent and epoxy reactive diluent are mixed to obtain an oil phase; polyvinyl alcohol and anionic surfactant are dissolved in deionized water to obtain a homogeneous aqueous phase; the obtained oil phase is added to the obtained aqueous phase and emulsified by high-speed shearing to obtain a fine emulsion; wall material reactants dissolved in a third organic solvent are added to the fine emulsion; after the reaction is completed, powdered microcapsules are prepared; the average particle size D50 of the microcapsules is 8-15 micrometers.

[0041] Specifically, the preparation method of the epoxy resin-based latent curing microcapsules is as follows: a) Preparation of core material oil phase: 60-70 parts by weight of bisphenol A type epoxy resin and / or bisphenol F type epoxy resin, 30-40 parts by weight of dicyandiamide and / or its derivatives are mixed with 1-5 parts by weight of epoxy reactive diluent and stirred at 35-40℃ until uniform to obtain oil phase. b) Aqueous phase preparation: Dissolve 1-3 parts by weight of polyvinyl alcohol and 0.5-1.5 parts by weight of anionic surfactant in 200 parts by weight of deionized water, and heat to 50-55℃ to obtain a homogeneous aqueous phase. c) Emulsification: Add the oil phase obtained in step a) to the aqueous phase obtained in step b), and emulsify at 6000-8000 rpm for 5-8 minutes at 50±2℃, and then perform high-pressure homogenization cycling at 40-60 MPa for 2-4 times to obtain a fine emulsion. d) Interfacial polymerization: The fine emulsion is transferred to the reactor and stirred at 50±2℃ and 400-600 rpm. The wall material reactant dissolved in the third organic solvent is slowly added dropwise to the system over 30-45 minutes. The wall material reactant dissolved in the third organic solvent consists of 8-12 parts by weight of PPG-220 or / and PPG-2000, 6-10 parts by weight of HDI trimer, and 10-15 parts by weight of the third organic solvent acetone. e) Curing and post-treatment: After the addition is completed, the temperature is raised to 65±2℃ and the reaction continues for 4-5 hours; after the reaction is completed, the mixture is cooled, washed, and filtered. The resulting solid is vacuum dried at 40-45℃ for 24-36 hours, pulverized and sieved to obtain powdered microcapsules.

[0042] The epoxy reactive diluent may be one or more of D-1217 polypropylene glycol diglycidyl ether and phenyl glycidyl ether; polyvinyl alcohol is preferably of average Mw 13000-23000; and the anionic surfactant is preferably sodium dodecylbenzenesulfonate (SDBS).

[0043] The oil phase was added to an aqueous phase containing polyvinyl alcohol and sodium dodecylbenzenesulfonate (SDBS). SDBS, acting as a small-molecule emulsifier, rapidly adsorbed at the oil-water interface to reduce surface tension; polyvinyl alcohol (PVA), acting as a high-molecular-weight protective colloid, formed a viscoelastic protective film at the interface. Subsequently, the immense shear force of high-pressure homogenization pulverized the oil phase into micron-sized droplets, which were then stabilized by the two surfactants, forming a uniform fine emulsion. This forms the basis for the subsequent formation of well-defined microcapsules.

[0044] The NCO groups of the HDI trimer undergo an addition polymerization reaction with the OH groups of the PPG polyol to form polyurethane. This reaction gradually forms a dense, water-insoluble, cross-linked polyurethane film that completely encapsulates the core material droplets. The HDI trimer provides aliphatic resistance to yellowing and high cross-linking density; polypropylene glycol provides flexible chain segments. The combination of these two components gives the wall material both toughness and strength. Heating to 65°C accelerates the reaction, ensuring the complete reaction of the NCO groups and the formation of a robust and intact wall material.

[0045] The dense polyurethane wall material completely isolates the core material from the external environment (and other components in the paint film). As long as the wall material remains intact, the internal epoxy resin and dicyandiamide remain in a "latent" state. When the paint film is scratched deep enough, the mechanical stress breaks the microcapsule wall material, and the core material mixture (epoxy resin + dicyandiamide + thinner) flows out into the scratch. The effluent mixes evenly, and under the energy provided by the subsequent baking process of the paint film or local frictional heat, the dicyandiamide is activated. Its amine groups undergo a ring-opening addition polymerization reaction with the epoxy groups of the epoxy resin to form a three-dimensional cross-linked network, which solidifies and fills the scratch, completing the repair.

[0046] The average particle size (D50) of the microcapsules is 8-15 micrometers. When these 8-15 micrometer capsules are distributed within the paint film, a microscopic or macroscopic scratch has a very high probability of penetrating multiple capsules, ensuring reliable release of the repair agent. Particles that are too small (e.g., <5 micrometers) may be bypassed by the scratch. As embedded particles, excessively large particle sizes (e.g., >20 micrometers) will severely disrupt the continuous phase resin matrix, becoming stress defect points and significantly reducing paint film adhesion, impact resistance, and hardness. 8-15 micrometers is the upper limit size that ensures functionality without significantly compromising the integrity of the paint film.

[0047] On the other hand, the present invention provides a method for preparing the above-mentioned oil-based wood protective topcoat, comprising the following steps: By weight, 50-70 parts of modified alkyd resin containing dynamic disulfide bonds, 4-8 parts of epoxy resin-based latent curing microcapsules, 0.5-1.5 parts of wetting and dispersing agent, and 0.2-0.8 parts of defoamer are dispersed at 400-600 rpm for 10-20 minutes; then 20-35 parts of the first organic solvent are added to adjust the viscosity to 80-120 seconds at a Fore-4 cup, and the mixture is filtered to obtain component A. Mix component A and isocyanate curing agent at a weight ratio of (5-7):1 until homogeneous, cure, and then apply to the wood surface for curing. The curing time is preferably 20-30 minutes.

[0048] In practical applications, pigments and fillers can be added as needed, such as titanium dioxide and precipitated barium sulfate.

[0049] The present invention will be further illustrated below with specific embodiments.

[0050] All reagents used in the embodiments of this application are commercially available products. Among them, the HDI trimer is selected from Desmodur® N 3390, the HDI biuret is selected from Desmodur® N75 BA, and the IPDI trimer is selected from Vestanet T1890E. The soybean oil fatty acids are selected from Shandong Xinyida Chemical Technology Co., Ltd., the linseed oil fatty acids are selected from Wuhan Maikairui Chemical Co., Ltd., and the coconut oil fatty acids are selected from Shandong Qianfanshun Chemical Co., Ltd. (density 0.84-0.86 g / ml).

[0051] Example 1: The preparation method of modified alkyd resin containing dynamic disulfide bonds is as follows: In a reactor, 10 parts by weight of pentaerythritol, 25 parts by weight of isophthalic acid, 15 parts by weight of soybean oil fatty acids, and 6 parts by weight of xylene as reflux solvent are added. An inert gas is introduced, and the temperature is raised to 190°C to carry out an esterification reaction until the acid value is 10 mgKOH / g. The temperature is lowered to 130°C, and 4 wt% of disulfide bond chain extender 2-hydroxyethyl disulfide is added. The reaction is maintained at this temperature for 2.5 hours. The temperature is lowered to below 80°C, and propylene glycol methyl ether acetate solvent is added to adjust the solid content to 70±2%. The mixture is then filtered and discharged.

[0052] The preparation method of epoxy resin-based latent curing microcapsules is as follows: a) Core material oil phase preparation: 65 parts by weight of bisphenol A epoxy resin, 35 parts by weight of dicyandiamide, and 3 parts by weight of epoxy reactive diluent D-1217 polypropylene glycol diglycidyl ether were mixed and stirred at 38°C until homogeneous to obtain the oil phase; b) Aqueous phase preparation: 2 parts by weight of polyvinyl alcohol (average Mw 13000-23000) and 1 part by weight of anionic surfactant sodium dodecylbenzenesulfonate were dissolved in 200 parts by weight of deionized water and heated to 50°C to obtain a homogeneous aqueous phase; c) Emulsification: The oil phase obtained in step a) was added to the aqueous phase obtained in step b), and emulsified at 50±2°C with high-speed shearing at 7000 rpm for 6 minutes, followed by high-pressure homogenization cycling at 50 MPa for 3 times to obtain a fine emulsion; d) Interfacial polymerization: The fine emulsion was transferred to a reactor and maintained at 50±2°C and 500... The wall material reactant dissolved in the third organic solvent was slowly added dropwise to the system over 40 minutes while stirring at rpm. The wall material reactant dissolved in the third organic solvent consisted of 10 parts by weight of PPG-220, 8 parts by weight of HDI trimer, and 13 parts by weight of the third organic solvent acetone. e) Curing and post-treatment: After the dropwise addition was completed, the temperature was raised to 65±2℃ and the reaction was continued for 4 hours. After the reaction was completed, the mixture was cooled, washed, and filtered. The resulting solid was vacuum dried at 40℃ for 30 hours, pulverized, and sieved to obtain powdered microcapsules with an average particle size D50 of 10.5 micrometers.

[0053] Topcoat preparation method: By weight, 60 parts of modified alkyd resin containing dynamic disulfide bonds, 6 parts of epoxy resin-based latent curing microcapsules, 1 part of wetting and dispersing agent BYK-163, and 0.6 parts of defoamer BYK-066N were dispersed at 500 rpm for 15 minutes; then 30 parts of the first organic solvent xylene were added to adjust the viscosity to 100 seconds at a Fore-4 cup, and the mixture was filtered to obtain component A. The A component and the isocyanate curing agent HDI trimer are mixed evenly at a weight ratio of 6:1, cured, and then applied to the wood surface for curing.

[0054] Comparative Example 1: Unlike implementation 1, epoxy resin-based latent curing microcapsules are not added during the preparation of the topcoat.

[0055] Comparative Example 2: The difference from Implementation 1 is that the modified alkyd resin containing dynamic disulfide bonds is not added in the preparation of the topcoat. Instead, the same mass fraction of alkyd resin is used, and the preparation method is as follows.

[0056] In the reactor, add 10 parts by weight of pentaerythritol, 25 parts by weight of isophthalic acid, 15 parts by weight of soybean oil fatty acid and 6 parts by weight of xylene as reflux solvent. Inert gas is introduced and the temperature is raised to 190°C to carry out the esterification reaction until the acid value is 10 mgKOH / g. The temperature is then lowered to below 80°C, and propylene glycol methyl ether acetate solvent is added to adjust the solid content to 70±2%. The mixture is then filtered and discharged.

[0057] Comparative Example 3: The difference from Embodiment 3 is that epoxy resin-based latent curing microcapsules are not added during the preparation of the topcoat. Furthermore, modified alkyd resin containing dynamic disulfide bonds is not added during the preparation of the topcoat; instead, an equal mass fraction of alkyd resin is used.

[0058] Example 2: Nanoscale scratch repair rate test Using a nano-scratch instrument, a fixed low load (5 mN) was applied to the paint film surface, and a scratch with a depth of approximately 1-2 micrometers was created at a constant speed. The initial cross-sectional profile of the scratch was recorded using the instrument's built-in morphology scanning module, and the initial scratch cross-sectional area (A1) was calculated.

[0059] Place the sample in a 60℃ oven for 2 hours. Rescan the scratch outline at the same location and calculate the cross-sectional area of ​​the scratch after repair (A2). Depth repair rate = (1 - A2 / A1) × 100%.

[0060] The experimental results are as follows: Table 1 Micro-scratch depth repair rate Example 1 91% ± 5% Comparative Example 1 85% ± 7% Comparative Example 2 11%± 4% Comparative Example 3 5%±2% The comparison revealed that Example 1 and Comparative Example 1 exhibited high repair rates, which is directly attributed to the modified alkyd resin containing dynamic disulfide bonds. Under heat treatment at 60°C, the disulfide bonds (-SS-) in the resin network underwent reversible "breakage-exchange-reorganization." This process provides the kinetics for the migration and re-entanglement of molecular chain segments at the scratch interface, thereby driving the material on both sides of the crack to flow into the gap and reconnect, achieving microscale self-healing.

[0061] Comparative Examples 2 and 3 both exhibited low repair rates: neither contained dynamic disulfide bonds. Their resin networks were permanently covalently cross-linked, with molecular chain segments fixed. Upon heating, they only underwent physical expansion and could not achieve effective mass transfer and interface reconstruction, thus lacking repair capabilities.

[0062] Example 3: Adhesion Test of Restoration Using a sharp carbide blade, and under the control of a scratching fixture, standardized scratches are made at a fixed angle (30°) and a load of 20 N, extending to the metal substrate (width > 20 micrometers, depth to the substrate to ensure cutting through microcapsules) and approximately 3 cm in length.

[0063] The scratched sample was placed in a 60℃ oven for 30 minutes, and then placed under standard conditions (23±2℃) for 72 hours. The cross-cut adhesion test (GB / T9286-2021) was performed directly on the repaired scratch to evaluate the bonding strength between the repair and the substrate.

[0064] The experimental results are as follows: Table 2 Cross-cut adhesion rating Macro characteristics Example 1 Level 0 Smooth edges, with no missing sections. Comparative Example 1 Level 5 The coating peeled off completely in the cutting area. Comparative Example 2 Level 4 Large pieces of the cut edge peeled off, >35%. Comparative Example 3 Level 5 The scratches are hollow. Combining the data in Tables 2 and 1, Comparative Example 1 shows that without microcapsules to provide repair materials, regardless of whether the resin itself has microscale damage repair properties, it is impossible to repair macroscopic scratches that extend deep into the substrate. Comparative Example 2: This group contained microcapsules, and repair could occur, but the adhesion was poor. The reason is that ordinary alkyd resin forms a chemically inert interface with low surface energy after curing. When the epoxy component released by the microcapsules cures, the two rely only on weak physical adsorption and mechanical interlocking, becoming a weak link under stress and easily peeling off from the interface.

[0065] Example 1 exhibits superior performance, demonstrating a significant synergistic effect between the modified alkyd resin containing dynamic disulfide bonds and the epoxy resin-based latent curing microcapsules described in this invention, rather than a simple superposition of their functions. When the microcapsules rupture and the epoxy component flows out, the molecular chain segments of the resin matrix containing dynamic disulfide bonds exhibit high mobility at the fresh interface of the scratch. During subsequent heat treatment, these dynamic bonds can undergo reversible breakage and recombination. When the repair is subjected to test stress (such as the shear force of a cross-cut test), the exchange reaction of dynamic bonds can effectively dissipate interfacial stress and prevent microcracks from propagating along the fragile interface. Simultaneously, some resin segments can diffuse into the incompletely cured epoxy network, forming a microscopic interpenetrating network, thereby combining mechanical interlocking with chemical anchoring. It is this synergistic effect that makes the topcoat prepared by this invention exhibit a significantly better adhesion (reaching grade 0) between the repair and the substrate after repairing macroscopic scratches than ordinary systems containing only microcapsules. This proves that the dynamic disulfide bond resin matrix not only has its own repair capabilities, but also fundamentally improves the strength and durability of the repair, achieving a technical effect of 1+1>2.

[0066] Example 4 The preparation method of modified alkyd resin containing dynamic disulfide bonds is as follows: In a reaction vessel, add 8 parts by weight of pentaerythritol, 20 parts by weight of isophthalic acid, 10 parts by weight of soybean oil fatty acid, and 5 parts by weight of xylene as reflux solvent. Inert gas is introduced, and the temperature is raised to 180°C to carry out esterification reaction until the acid value is 8 mgKOH / g. The temperature is lowered to 120°C, and 2 wt% of disulfide bond chain extender 2-hydroxyethyl disulfide is added. The reaction is maintained at this temperature for 2 hours. The temperature is lowered to below 80°C, and propylene glycol methyl ether acetate solvent is added to adjust the solid content to 70±2%. The mixture is then filtered and discharged.

[0067] The preparation method of epoxy resin-based latent curing microcapsules is as follows: a) Core material oil phase preparation: 60 parts by weight of bisphenol A type epoxy resin, 30 parts by weight of dicyandiamide, and 1 part by weight of epoxy reactive diluent D-1217 polypropylene glycol diglycidyl ether are mixed and stirred at 35°C until homogeneous to obtain the oil phase; b) Aqueous phase preparation: 1 part by weight of polyvinyl alcohol (average Mw 13000-23000) and 0.5 parts by weight of anionic surfactant sodium dodecylbenzenesulfonate are dissolved in 200 parts by weight of deionized water and heated to 50°C to obtain a homogeneous aqueous phase; c) Emulsification: The oil phase obtained in step a) is added to the aqueous phase obtained in step b), and emulsified at 50±2°C with high-speed shearing at 6000 rpm for 5 minutes, followed by high-pressure homogenization circulation twice at 40 MPa to obtain a fine emulsion; d) Interfacial polymerization: The fine emulsion is transferred to a reactor and maintained at 50±2°C and 400... Stirring at rpm, the wall material reactant dissolved in the third organic solvent was slowly added dropwise to the system over 30 minutes; the wall material reactant dissolved in the third organic solvent consisted of 8 parts by weight of PPG-220, 6 parts by weight of HDI trimer, and 10 parts by weight of the third organic solvent acetone; e) Curing and post-treatment: After the dropwise addition was completed, the temperature was raised to 65±2℃ and the reaction was continued for 4 hours; after the reaction was completed, the mixture was cooled, washed, and filtered. The resulting solid was vacuum dried at 40℃ for 24 hours, pulverized, and sieved to obtain powdered microcapsules.

[0068] Topcoat preparation method: By weight, 50 parts of modified alkyd resin containing dynamic disulfide bonds, 4 parts of epoxy resin-based latent curing microcapsules, 0.5 parts of wetting and dispersing agent BYK-163, and 0.2 parts of defoamer BYK-066N were dispersed at 400 rpm for 10 minutes; then 20 parts of the first organic solvent xylene were added to adjust the viscosity to 80 seconds at a Fore-4 cup, and the mixture was filtered to obtain component A. Component A and HDI trimer isocyanate curing agent were mixed evenly at a weight ratio of 5:1, cured, and then applied to the wood surface for curing. The micro-scratch depth repair rate was 88%, and the cross-cut adhesion rating was Grade 1.

[0069] Example 5 The preparation method of modified alkyd resin containing dynamic disulfide bonds is as follows: In a reactor, 12 parts by weight of pentaerythritol, 28 parts by weight of isophthalic acid, 16 parts by weight of soybean oil fatty acids, and 8 parts by weight of reflux solvent xylene are added. An inert gas is introduced, and the temperature is raised to 200°C to carry out an esterification reaction until the acid value is 12 mgKOH / g. The temperature is then lowered to 140°C, and 6 wt% of the solids of the resin containing disulfide chain extender 2-hydroxyethyl disulfide is added. The reaction is maintained at this temperature for 3 hours. The temperature is then lowered to below 80°C, and propylene glycol methyl ether acetate solvent is added to adjust the solid content to 70±2%. The mixture is then filtered and discharged.

[0070] The preparation method of epoxy resin-based latent curing microcapsules is as follows: a) Core material oil phase preparation: 70 parts by weight of bisphenol A epoxy resin, 40 parts by weight of dicyandiamide, and 5 parts by weight of epoxy reactive diluent D-1217 polypropylene glycol diglycidyl ether were mixed and stirred at 40°C until homogeneous to obtain the oil phase; b) Aqueous phase preparation: 3 parts by weight of polyvinyl alcohol (average Mw 13000-23000) and 1.5 parts by weight of anionic surfactant sodium dodecylbenzenesulfonate were dissolved in 200 parts by weight of deionized water and heated to 55°C to obtain a homogeneous aqueous phase; c) Emulsification: The oil phase obtained in step a) was added to the aqueous phase obtained in step b), and emulsified at 8000 rpm for 8 minutes at 50±2°C, followed by high-pressure homogenization and circulation at 60 MPa for 4 times to obtain a fine emulsion; d) Interfacial polymerization: The fine emulsion was transferred to a reactor and maintained at 50±2°C and 600 rpm. Stirring at rpm, the wall material reactant dissolved in the third organic solvent was slowly added dropwise to the system over 45 minutes; the wall material reactant dissolved in the third organic solvent consisted of 12 parts by weight of PPG-220, 10 parts by weight of HDI trimer, and 15 parts by weight of the third organic solvent acetone; e) Curing and post-treatment: After the dropwise addition was completed, the temperature was raised to 65±2℃ and the reaction was continued for 5 hours; after the reaction was completed, the mixture was cooled, washed, and filtered. The resulting solid was vacuum dried at 45℃ for 36 hours, pulverized, and sieved to obtain powdered microcapsules.

[0071] Topcoat preparation method: By weight, 70 parts of modified alkyd resin containing dynamic disulfide bonds, 8 parts of epoxy resin-based latent curing microcapsules, 1.5 parts of wetting and dispersing agent BYK-163, and 0.8 parts of defoamer BYK-066N were dispersed at 600 rpm for 20 minutes; then 35 parts of the first organic solvent xylene were added to adjust the viscosity to 120 seconds at a Fore-4 cup, and the mixture was filtered to obtain component A. Component A and HDI trimer isocyanate curing agent were mixed evenly at a weight ratio of 7:1, cured, and then applied to the wood surface for curing. The micro-scratch depth repair rate was 85%, and the cross-cut adhesion rating was Grade 1.

[0072] Example 6 The preparation method of modified alkyd resin containing dynamic disulfide bonds is as follows: In a reaction vessel, 10 parts by weight of trimethylolpropane, 25 parts by weight of adipic acid, 15 parts by weight of linseed oil fatty acids, and 6 parts by weight of reflux solvent propylene glycol methyl ether acetate are added. An inert gas is introduced, and the temperature is raised to 190°C to carry out an esterification reaction until the acid value is 10 mg KOH / g. The temperature is lowered to 130°C, and 4,4'-dithiodibenzoic acid, a disulfide bond chain extender accounting for 4 wt% of the resin solids, is added. The reaction is maintained at this temperature for 2 hours. The temperature is lowered to below 80°C, and butyl acetate is added to adjust the solid content to 70 ± 2%. The mixture is then filtered and discharged.

[0073] The preparation method of epoxy resin-based latent curing microcapsules is as follows: a) Core material oil phase preparation: 65 parts by weight of bisphenol F epoxy resin, 35 parts by weight of dicyandiamide, and 3 parts by weight of epoxy reactive diluent phenyl glycidyl ether were mixed and stirred at 38°C until homogeneous to obtain the oil phase; b) Aqueous phase preparation: 2 parts by weight of polyvinyl alcohol (average Mw 13000-23000) and 1 part by weight of anionic surfactant sodium dodecylbenzenesulfonate were dissolved in 200 parts by weight of deionized water and heated to 50°C to obtain a homogeneous aqueous phase; c) Emulsification: The oil phase obtained in step a) was added to the aqueous phase obtained in step b), and emulsified at 50±2°C with high-speed shearing at 7000 rpm for 6 minutes, followed by high-pressure homogenization cycling at 50 MPa for 3 times to obtain a fine emulsion; d) Interfacial polymerization: The fine emulsion was transferred to a reactor and maintained at 50±2°C and 500... Stirring at rpm, the wall material reactant dissolved in the third organic solvent was slowly added dropwise to the system over 40 minutes; the wall material reactant dissolved in the third organic solvent consisted of 10 parts by weight of PPG-2000, 8 parts by weight of HDI trimer, and 13 parts by weight of the third organic solvent acetone; e) Curing and post-treatment: After the dropwise addition was completed, the temperature was raised to 65±2℃ and the reaction was continued for 4 hours; after the reaction was completed, the mixture was cooled, washed, and filtered. The resulting solid was vacuum dried at 40℃ for 30 hours, pulverized, and sieved to obtain powdered microcapsules.

[0074] Topcoat preparation method: By weight, 60 parts of modified alkyd resin containing dynamic disulfide bonds, 6 parts of epoxy resin-based latent curing microcapsules, 1 part of wetting and dispersing agent TEGO Dispers 750, and 0.6 parts of defoamer TEGO Airex 902W were dispersed at 500 rpm for 15 minutes; then 30 parts of the first organic solvent butyl acetate were added to adjust the viscosity to 100 seconds at a Fore-4 cup, and the mixture was filtered to obtain component A. Component A and the isocyanate curing agent HDI biuret were mixed evenly at a weight ratio of 6:1, cured, and then applied to the wood surface for curing. The micro-scratch depth repair rate was 93%, and the cross-cut adhesion rating was 0.

[0075] Example 7: The preparation method of modified alkyd resin containing dynamic disulfide bonds is as follows: In a reaction vessel, 10 parts by weight of glycerol, 25 parts by weight of adipic acid, 15 parts by weight of coconut oil fatty acids, and 6 parts by weight of reflux solvent propylene glycol methyl ether acetate are added. An inert gas is introduced, and the temperature is raised to 190°C to carry out an esterification reaction until the acid value is 10 mgKOH / g. The temperature is then lowered to 130°C, and 4,4'-dithiodibenzoic acid, a disulfide bond chain extender, is added, accounting for 4 wt% of the resin solids. The reaction is maintained at this temperature for 2 hours. The temperature is then lowered to below 80°C, and butyl acetate is added to adjust the solid content to 70±2%. The mixture is then filtered and discharged.

[0076] The preparation method of epoxy resin-based latent curing microcapsules is as follows: a) Core material oil phase preparation: 65 parts by weight of bisphenol F epoxy resin, 35 parts by weight of dicyandiamide, and 3 parts by weight of epoxy reactive diluent phenyl glycidyl ether were mixed and stirred at 38°C until homogeneous to obtain the oil phase; b) Aqueous phase preparation: 2 parts by weight of polyvinyl alcohol (average Mw 13000-23000) and 1 part by weight of anionic surfactant sodium dodecylbenzenesulfonate were dissolved in 200 parts by weight of deionized water and heated to 50°C to obtain a homogeneous aqueous phase; c) Emulsification: The oil phase obtained in step a) was added to the aqueous phase obtained in step b), and emulsified at 50±2°C with high-speed shearing at 7000 rpm for 6 minutes, followed by high-pressure homogenization cycling at 50 MPa for 3 times to obtain a fine emulsion; d) Interfacial polymerization: The fine emulsion was transferred to a reactor and maintained at 50±2°C and 500... Stirring at rpm, the wall material reactant dissolved in the third organic solvent was slowly added dropwise to the system over 40 minutes; the wall material reactant dissolved in the third organic solvent consisted of 10 parts by weight of PPG-2000, 8 parts by weight of HDI trimer, and 13 parts by weight of the third organic solvent acetone; e) Curing and post-treatment: After the dropwise addition was completed, the temperature was raised to 65±2℃ and the reaction was continued for 4 hours; after the reaction was completed, the mixture was cooled, washed, and filtered. The resulting solid was vacuum dried at 40℃ for 30 hours, pulverized, and sieved to obtain powdered microcapsules.

[0077] Topcoat preparation method: By weight, 60 parts of modified alkyd resin containing dynamic disulfide bonds, 6 parts of epoxy resin-based latent curing microcapsules, 1 part of wetting and dispersing agent TEGO Dispers 750, and 0.6 parts of defoamer TEGO Airex 902W were dispersed at 500 rpm for 15 minutes; then 30 parts of the first organic solvent butyl acetate were added to adjust the viscosity to 100 seconds at a Fore-4 cup, and the mixture was filtered to obtain component A. Component A and IPDI trimer isocyanate curing agent were mixed evenly at a weight ratio of 6:1, cured, and then applied to the wood surface for curing. The micro-scratch depth repair rate was 88%, and the cross-cut adhesion rating was Grade 1.

[0078] Examples 4-7 demonstrate that the present invention maintains good stability, exhibiting a high micro-scratch depth repair rate and excellent cross-cut adhesion level.

Claims

1. An oil-based protective coating for wood with self-healing function, characterized in that: It consists of component A and component B; Component A includes a modified alkyd resin containing dynamic disulfide bonds and epoxy resin-based latent curing microcapsules; the epoxy resin-based latent curing microcapsules have an epoxy resin core and a latent curing agent, and a polyurethane wall material. Component B is an isocyanate curing agent; The weight ratio of component A to component B is (5-7):

1.

2. The oil-based wood protective topcoat according to claim 1, characterized in that, Based on the total weight of component A, the content of the modified alkyd resin containing dynamic disulfide bonds is 50-70 parts, the content of the epoxy resin-based latent curing microcapsules is 4-8 parts, and component A also includes 0.5-1.5 parts of wetting and dispersing agent, 0.2-0.8 parts of defoamer, and 20-35 parts of first organic solvent.

3. The oil-based wood protective topcoat according to claim 1, characterized in that, The method for preparing the modified alkyd resin containing dynamic disulfide bonds is as follows: under the protection of an inert gas, polyols, polyacids and fatty acids are subjected to esterification and polycondensation reaction to form an alkyd resin prepolymer; in the middle or late stage of the reaction, a chain extender containing disulfide bonds is added to continue the reaction, so that the dynamic disulfide bonds are chemically incorporated into the alkyd resin molecular chain.

4. The oil-based wood protective topcoat according to claim 3, characterized in that, The chain extender of the disulfide bond is one or more of 2-hydroxyethyl disulfide and 4,4'-dithiodibenzoic acid, and its addition amount accounts for 2-6 wt% of the resin solids.

5. The oil-based wood protective topcoat according to claim 3, characterized in that, The method for preparing the modified alkyd resin containing dynamic disulfide bonds is as follows: In a reactor, add 8-12 parts by weight of polyol, 20-28 parts by weight of polyacid, 10-16 parts by weight of fatty acid and 5-8 parts by weight of reflux solvent, introduce inert gas, and heat to 180-200℃ to carry out esterification reaction until the acid value is 8-12 mgKOH / g; cool to 120-140℃, add 2-6wt% of disulfide bond chain extender of resin solids, and keep the reaction at this temperature for 2-3 hours; cool to below 80℃, add a second organic solvent to adjust the solid content to 70±5%, and filter to discharge the material.

6. The oil-based wood protective topcoat according to claim 3, characterized in that, The polyol is one or more of pentaerythritol, trimethylolpropane, and glycerol; the polyacid is one or more of isophthalic acid and adipic acid; and the fatty acid is one or more of soybean oil fatty acid, linolenic acid, and coconut oil fatty acid.

7. The oil-based wood protective topcoat according to claim 1, characterized in that, The preparation method of the epoxy resin-based latent curing microcapsules is as follows: Epoxy resin, latent curing agent, and epoxy reactive diluent are mixed to obtain an oil phase; polyvinyl alcohol and anionic surfactant are dissolved in deionized water to obtain a homogeneous aqueous phase; the obtained oil phase is added to the obtained aqueous phase and emulsified by high-speed shearing to obtain a fine emulsion; wall material reactants dissolved in a third organic solvent are added to the fine emulsion; after the reaction is completed, powdered microcapsules are prepared; the average particle size D50 of the microcapsules is 8-15 micrometers.

8. The oil-based wood protective topcoat according to claim 7, characterized in that, The preparation method of the epoxy resin-based latent curing microcapsules is as follows: a) Preparation of core material oil phase: 60-70 parts by weight of bisphenol A type epoxy resin and / or bisphenol F type epoxy resin, 30-40 parts by weight of dicyandiamide and / or its derivatives are mixed with 1-5 parts by weight of epoxy reactive diluent and stirred at 35-40℃ until homogeneous to obtain the oil phase. b) Aqueous phase preparation: Dissolve 1-3 parts by weight of polyvinyl alcohol and 0.5-1.5 parts by weight of anionic surfactant in 200 parts by weight of deionized water, and heat to 50-55℃ to obtain a homogeneous aqueous phase. c) Emulsification: Add the oil phase obtained in step a) to the aqueous phase obtained in step b), and emulsify at 50±2℃ for 5-8 minutes at high speed shearing at 6000-8000 rpm, and then perform high pressure homogenization cycling 2-4 times at 40-60 MPa pressure to obtain a fine emulsion. d) Interfacial polymerization: The fine emulsion is transferred to the reactor and stirred at 50±2℃ and 400-600 rpm. The wall material reactant dissolved in the third organic solvent is slowly added dropwise to the system over 30-45 minutes. The wall material reactant dissolved in the third organic solvent consists of 8-12 parts by weight of PPG-220 or / and PPG-2000, 6-10 parts by weight of HDI trimer, and 10-15 parts by weight of the third organic solvent acetone. e) Curing and post-treatment: After the addition is completed, the temperature is raised to 65±2℃ and the reaction continues for 4-5 hours; after the reaction is completed, the mixture is cooled, washed, and filtered. The resulting solid is vacuum dried at 40-45℃ for 24-36 hours, pulverized and sieved to obtain powdered microcapsules.

9. The oil-based wood protective topcoat according to claim 1, characterized in that, The isocyanate curing agent is one or more of HDI trimer, HDI biuret, and IPDI trimer.

10. The method for preparing an oil-based protective topcoat for wood according to any one of claims 1-9, characterized in that, Includes the following steps: By weight, 50-70 parts of modified alkyd resin containing dynamic disulfide bonds, 4-8 parts of epoxy resin-based latent curing microcapsules, 0.5-1.5 parts of wetting and dispersing agent, and 0.2-0.8 parts of defoamer are dispersed at 400-600 rpm for 10-20 minutes; then 20-35 parts of the first organic solvent are added to adjust the viscosity to 80-120 seconds at a Fore-4 cup, and the mixture is filtered to obtain component A. Mix component A with isocyanate curing agent at a weight ratio of (5-7):1 until homogeneous, cure, apply to the wood surface, and cure.