A wear-resistant alkyd resin coating and its preparation method

Abstract

This invention discloses a wear-resistant alkyd resin coating and its preparation method, belonging to the technical field of alkyd resin coatings. First, a mixed vegetable oil is modified by epoxidation and ring-opening esterification to obtain a modified mixed vegetable oil. Then, this modified oil is further modified by esterification condensation and hydrophilic modification to obtain a modified waterborne alkyd resin. Simultaneously, modified nano-cerium oxide is prepared by in-situ precipitation using phosphate betaine as a modifier. Finally, the modified waterborne alkyd resin, modified nano-cerium oxide, and additives are mixed to obtain the wear-resistant alkyd resin coating. This invention, through the synergistic effect of epoxidized vegetable oil, anhydride ring-opening crosslinking network, and in-situ modified nano-cerium oxide, solves the defects of traditional alkyd resin coatings, such as insufficient wear resistance, difficulty in balancing rigidity and toughness, and easy agglomeration of fillers. It endows the coating with excellent wear resistance, high hardness, good adhesion, and flexibility, meeting the high-standard wear-resistant protection requirements of mechanical equipment and steel structures.

Description

Technical Field

[0001] This invention belongs to the field of alkyd resin coating technology, specifically a wear-resistant alkyd resin coating and its preparation method. Background Technology

[0002] Alkyd resins are an important class of polyester resins produced by polyols, polyacids, and fatty acids or vegetable oils through polycondensation reactions. Since their advent in the 20th century, they have become one of the most widely produced and applied synthetic resins in the coatings industry due to their wide availability of raw materials, mature synthesis processes, low cost, high film fullness, strong adhesion, and excellent workability. They are widely used for protection and decoration in fields such as bridges, steel structures, engineering machinery, ships, and wooden furniture. With increasingly stringent environmental regulations and the continuous increase in demand for low volatile organic compound (VOC) coatings, traditional solvent-based alkyd resins are gradually developing towards water-based formulations. Water-based alkyd resin coatings, which combine the comprehensive performance of alkyd resins with lower VOC emissions, have become one of the current research and application hotspots.

[0003] However, traditional alkyd resin coatings have some inherent defects that severely limit their application in high-end or harsh environments. First, the cross-linking density of the three-dimensional network structure formed after the coating film dries is limited, resulting in relatively low film hardness, insufficient abrasion resistance, and insufficient scratch resistance. In daily use, the coated surface is prone to losing its gloss and developing scratches due to friction and scratches, affecting its appearance and shortening the protection cycle. In industrial fields (such as machine tool guides, factory floors, transportation vehicles, etc.), poor abrasion resistance may lead to rapid coating failure and loss of protection for the substrate.

[0004] Chinese patent application CN109651781A discloses a wear-resistant water-based baking paint and its manufacturing method. By increasing the degree of crosslinking of the resin system and compounding glass fiber, metal powder and inorganic pigments and fillers into the water-based alkyd resin, a coating structure with high mechanical strength is formed, thereby improving the wear resistance and scratch resistance of the coating.

[0005] However, improving wear resistance by increasing crosslinking density or introducing high-rigidity structures often comes at the cost of coating flexibility, which can easily lead to coating embrittlement and cracking or peeling under temperature changes or substrate deformation conditions, making it difficult to balance wear resistance and reliability. Summary of the Invention

[0006] The purpose of this invention is to provide a wear-resistant alkyd resin coating and its preparation method. By synergistically combining epoxidized vegetable oil, anhydride ring-opening crosslinking network, and in-situ modified nano-cerium oxide, the defects of traditional alkyd resin coatings, such as insufficient wear resistance, difficulty in balancing rigidity and toughness, and easy agglomeration of fillers, are solved. The coating is endowed with excellent wear resistance, high hardness, good adhesion and flexibility, meeting the high standard wear-resistant protection requirements of mechanical equipment and steel structures.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] A method for preparing a wear-resistant alkyd resin coating, characterized by comprising the following steps:

[0009] Step 1: The mixed vegetable oil undergoes an epoxidation reaction with hydrogen peroxide under the catalysis of formic acid. After extraction and purification, it is then reacted with methyltetrahydrophthalic anhydride to obtain the modified mixed vegetable oil.

[0010] Step 2: Modified mixed vegetable oil, cashew nut shell oil, polyol and polyacid are esterified and polycondensed, and then hydrophilically modified by trimellitic anhydride to prepare modified waterborne alkyd resin.

[0011] Step 3: Using phosphate betaine as a modifier, cerium nitrate is modified by in-situ precipitation to obtain modified nano-cerium oxide powder.

[0012] Step 4: Add the modified waterborne alkyd resin, modified nano-cerium oxide powder, talc powder, wetting and dispersing agent, defoamer, film-forming aid, leveling agent and deionized water into the mixing equipment, and disperse, mix and filter in steps to obtain the wear-resistant alkyd resin coating.

[0013] Furthermore, the mass ratio of modified waterborne alkyd resin, modified nano-cerium oxide powder, talc powder, wetting and dispersing agent, defoamer, film-forming aid, leveling agent, and deionized water is 40-60:15-20:3-5:0.3-0.6:0.1-0.2:5-8:0.4-0.6:30-40.

[0014] Furthermore, the specific preparation steps of the modified waterborne alkyd resin are as follows:

[0015] Modified mixed vegetable oil, cashew nut shell oil, diethylene glycol, benzoic acid, terephthalic acid, phthalic anhydride, pentaerythritol, and xylene were sequentially added to a reaction vessel and reacted at 250-350 rpm and 208-212°C for 5-6 hours. Trimeric trioxide was added at 70-80°C, and the mixture was stirred and dispersed at 40-60 rpm for 10-12 minutes. The reaction was then continued at 250-350 rpm and 158-162°C for 2.5-3 hours until the acid value of the product was <40 mg KOH / g. Heating was stopped and the temperature was lowered to 143-147°C. Xylene was removed by vacuum, and the temperature was further lowered to 50°C. Ethylene glycol monobutyl ether and distilled water were added, and the mixture was stirred thoroughly and mixed evenly. The mixture was then filtered through a 200-mesh filter to obtain the modified waterborne alkyd resin.

[0016] Furthermore, the mass ratio of the modified mixed vegetable oil, cashew nut shell oil, diethylene glycol, benzoic acid, terephthalic acid, phthalic anhydride, pentaerythritol, xylene, trimellitic anhydride, ethylene glycol monobutyl ether, and distilled water is 100:10.7-28.6:10.7-28.6:46.3-64.3:7.1-21.4:1.8-5.4:42.9-60.7:17.9-28.6:2-7:21.4-42:55-70.

[0017] Furthermore, the specific preparation steps for the modified mixed vegetable oil are as follows:

[0018] Nitrogen gas was introduced throughout the process. Epoxidized mixed vegetable oil, methyltetrahydrophthalic anhydride, and 2,4,6-tris(dimethylaminomethyl)phenol were added to a reaction vessel and stirred evenly at 55-65℃ and 300-500 r / min. The mixture was then placed at 148-152℃ for 1.5-2.5 h. The reaction endpoint was controlled by monitoring the acid value and epoxy value of the product. The reaction was completed when the acid value was ≤5 mg KOH / g and the epoxy residue was ≤0.05 mol / 100g, yielding the modified mixed vegetable oil.

[0019] Furthermore, the mass ratio of epoxidized mixed vegetable oil, methyltetrahydrophthalic anhydride, and 2,4,6-tris(dimethylaminomethyl)phenol is 100-140:20-30:0.2-0.3.

[0020] Furthermore, the specific preparation steps for epoxidized mixed vegetable oils are as follows:

[0021] The vegetable oil mixture was added to the reaction vessel, and formic acid was added at 550-650 r / min. A 30% hydrogen peroxide aqueous solution was slowly added dropwise to the vessel over 30-45 min. After the addition was completed, the rotation speed was maintained and the temperature was raised to 58-62℃ to continue the reaction for 7-9 h. After the reaction was completed, the mixture was cooled to room temperature, and dichloromethane was added for extraction. After washing, drying, impurity removal, and concentration, the epoxidized mixed vegetable oil was obtained.

[0022] Furthermore, the mass ratio of the vegetable oil mixture, formic acid, and hydrogen peroxide aqueous solution is 80-120:6.5-8.5:15-20.

[0023] Furthermore, the vegetable oil mixture is composed of castor oil, soybean oil, and tung oil in a mass ratio of 4:3:2.

[0024] Furthermore, the specific preparation steps of the modified nano-cerium oxide powder are as follows:

[0025] Deionized water and phosphate betaine were added to a reaction vessel and stirred at 300-500 r / min until dissolved. Then, cerium nitrate hexahydrate was added and stirred evenly. Under continuous stirring at 65-75℃, an 8.4 wt% sodium hydroxide aqueous solution was slowly added dropwise over 30 min. After the addition was complete, the reaction was carried out for 1.5-2.5 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain modified nano-cerium oxide powder.

[0026] Furthermore, the ratio of deionized water, phosphate betaine, cerium nitrate hexahydrate, and sodium hydroxide aqueous solution is 40-60 mL: 0.5-1 g: 14-16 g: 40-60 mL.

[0027] The beneficial effects of this invention are:

[0028] 1. This invention solves the core defect of traditional alkyd resin coatings, which sacrifice flexibility due to simply increasing crosslinking density or introducing rigid structures, resulting in brittleness and cracking, by constructing a ternary synergistic reinforcement system of epoxidized vegetable oil / anhydride modified active resin matrix, functionalized waterborne alkyd resin, and phosphate betaine in situ modified nano-cerium oxide. This system not only fundamentally strengthens the coating structure through chemical bonding and interface design, but also achieves deep integration of reinforcement, toughening, stable dispersion, and multiple crosslinking functions through the synergistic effect of the functional groups of each component, thus avoiding the bottleneck of functional limitations and difficulty in balancing performance of single modification methods.

[0029] 2. This invention achieves a synergistic design of rigidity and toughness in the resin matrix at the molecular level through epoxidation and anhydride ring-opening-esterification modification technology. Epoxidation transforms the flexible double bonds in vegetable oil into highly active epoxy groups, constructing a customizable reaction platform; anhydride ring-opening chemically bonds the rigid benzene ring structure onto this platform. This design endows the coating with high hardness and excellent wear resistance. At the same time, through the microstructure of "rigid segments dispersed in a flexible matrix", silvering is induced under stress and crack propagation is prevented, ensuring that the coating has both good flexibility and impact resistance, breaking through the bottleneck of traditional technology where wear resistance and toughness are difficult to balance.

[0030] Furthermore, the modified resin is rich in polar groups such as carboxyl and ester groups, which significantly enhances the interfacial compatibility and interaction with fillers and substrates, further improving the overall mechanical properties of the composite material. The modified vegetable oil also has thermally induced phase change characteristics, acting as a solid reinforcing phase at room temperature and melting and flowing at high temperatures, achieving good fluidity during processing. After cooling, it re-cures into a reinforcing network, giving the coating certain temperature responsiveness and structural designability. While improving performance, this system maintains the environmentally friendly characteristics and good processing adaptability of bio-based materials, providing a feasible path for the development of high-performance environmentally friendly coatings.

[0031] 3. This invention utilizes in-situ modification technology with phosphate betaine to prepare nano-cerium oxide fillers that possess both high surface activity and excellent interfacial compatibility. This technology allows nanoparticles to be coated with amphiphilic molecules instantly upon generation, with phosphate groups strongly anchored to the inorganic surface, while the betaine structure and long alkyl chains extend outward. This design macroscopically solves the problem of nanofiller aggregation in resin, ensuring the storage stability of the coating. At the microscopic level, the modified nanoparticles can directly improve wear resistance through physical barrier and load-bearing effects. Furthermore, their organic shells can strongly interact with the polar groups of the modified resin, forming an "organic-inorganic" bridging network that effectively disperses external forces, thereby synergistically improving the overall mechanical strength, durability, and adhesion to the substrate of the coating. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0033] Example 1: A wear-resistant alkyd resin coating, prepared by the following method:

[0034] S1: 100g of a mixture of vegetable oils (castor oil, soybean oil, and tung oil in a mass ratio of 4:3:2) was added to a reaction vessel. 7.5g of formic acid, an oxidation catalyst, was added at a rotation speed of 600 r / min. 17.5g of a 30% (w / w) aqueous solution of hydrogen peroxide was slowly added dropwise to the vessel over 30-45 min. After the addition was complete, the rotation speed was maintained and the temperature was raised to 60℃ to continue the reaction for 8 h. After the reaction was completed, the reaction solution was cooled to room temperature, and dichloromethane was added for extraction. The organic phase was washed successively with water, saturated sodium bicarbonate solution, and saturated sodium chloride solution, then dried with anhydrous sodium sulfate. The desiccant was removed by filtration, and the filtrate was concentrated under reduced pressure to obtain the epoxidized mixed vegetable oil.

[0035] The epoxidation reaction based on olefins begins with hydrogen peroxide reacting with formic acid in an acidic environment catalyzed by formic acid catalyst, generating highly reactive peroxyformic acid in situ. This peroxyformic acid acts as a key oxygen carrier, and the active oxygen atoms in its molecule then attack the carbon-carbon double bonds (C=C) in the unsaturated fatty acid structural units of the molecular chains of mixed vegetable oils (castor oil, soybean oil, and tung oil). This electrophilic addition process allows an oxygen atom to be inserted between the carbon-carbon double bonds, thereby transforming the unstable double bond into a stable three-membered oxygen heterocyclic structure, namely the epoxy group (-C(O)C-), completing the epoxidation reaction. The resulting product is then purified by extraction, alkaline washing to neutralize the residual acid catalyst, water washing, and salting out to obtain the epoxidized mixed vegetable oil.

[0036] S2: Nitrogen gas was introduced throughout the process. 120g of epoxidized mixed vegetable oil, 24g of methyltetrahydrophthalic anhydride and 0.24g of 2,4,6-tris(dimethylaminomethyl)phenol were added to the reactor and stirred evenly at 60℃ and 400r / min. The mixture was then placed at 150℃ for 2h. The reaction endpoint was controlled by monitoring the acid value and epoxy value of the product. When the acid value ≤5mgKOH / g and the epoxy residue ≤0.05mol / 100g, the reaction was considered complete, and the modified mixed vegetable oil was obtained.

[0037] Based on the anhydride ring-opening-esterification synergistic reaction, under nitrogen protection, 2,4,6-tris(dimethylaminomethyl)phenol catalyzes the nucleophilic ring-opening of methyltetrahydrophthalic anhydride with the three-membered epoxy ring in the epoxidized mixed vegetable oil, generating a carboxyl-ester intermediate. The system is then heated to 150°C, and the carboxylic acid and adjacent hydroxyl groups in the half-ester structure are further esterified and dehydrated to form a cross-linked network. At the same time, excess anhydride ensures complete epoxy conversion, resulting in a modified mixed vegetable oil with both rigid ester rings and flexible aliphatic chains.

[0038] S3: 100g of modified mixed vegetable oil, 19.7g of cashew nut shell oil, 19.7g of diethylene glycol, 55.3g of benzoic acid, 14.3g of terephthalic acid, 3.6g of phthalic anhydride, 51.8g of pentaerythritol, and 23.3g of xylene as reflux solvent were sequentially added to the reactor. Esterification was carried out under reflux for 5.5 hours at a rotation speed of 300 rpm and a temperature of 210℃. Water was removed using a water separator, and the acid value was monitored in real time until the acid value of the reaction product was <70mg KOH / g. Heating was stopped and the temperature was lowered to 75℃. 4.5g of trimellitic anhydride was added to the reactor, and the mixture was kept at a rotation speed of 50 rpm for 11 minutes to ensure thorough dispersion. The reaction was then continued for 3 hours at a rotation speed of 300 rpm and a temperature of 160℃ until the acid value of the product was <40mg KOH / g. KOH / g, stop heating, cool the material to 145℃, remove xylene from the system by vacuuming, continue cooling to below 50℃, add 31.7g ethylene glycol monobutyl ether and 62.5g distilled water, stir thoroughly and mix evenly, filter through a 200-mesh filter to remove impurities, and obtain modified waterborne alkyd resin.

[0039] Based on the principles of stepwise condensation and hydrophilic modification, firstly, modified mixed vegetable oil (containing rigid ester rings), cashew nut shell oil, polyols (pentaerythritol, diethylene glycol), and polyacids (benzoic acid, terephthalic acid, phthalic anhydride) undergo esterification and polycondensation at high temperature. By removing reaction water to drive equilibrium, an alkyd resin prepolymer with both rigid cyclic structure and flexible aliphatic chains linked by ester bonds is formed. The acid value reaches the target, indicating that the carboxyl groups are fully consumed and the molecular chain growth is complete. Subsequently, the system is cooled, and trimellitic anhydride is added. Its anhydride groups undergo ring-opening esterification with the residual hydroxyl groups of the prepolymer, further increasing the crosslinking density and introducing additional carboxyl groups as hydrophilic sites. Finally, the solvent is removed, and water is added under the action of a film-forming aid (ethylene glycol monobutyl ether) to form a stable aqueous dispersion of the carboxylated resin. The final product is obtained by filtration.

[0040] S4: Add 50 mL of deionized water and 0.75 g of phosphate betaine (PB) to the reactor and stir at 400 r / min until completely dissolved. Then add 14.92 g of cerium nitrate hexahydrate and continue stirring until a homogeneous solution is obtained. Heat the system to 70 °C and slowly add 50 mL of 8.4 wt% sodium hydroxide aqueous solution over 30 min while stirring continuously. After the addition is complete, continue the reaction at 70 °C for 2 h. After the reaction is complete, filter the reaction mixture and wash the precipitate repeatedly with 90 °C hot water until the last filtrate is neutral. Dry the obtained solid under vacuum at 60 °C for 20 h to obtain modified nano-cerium oxide powder.

[0041] S5: Add 50g of modified waterborne alkyd resin to the stirred tank and stir continuously for 6.5min at 38℃ and 400r / min to reduce the resin viscosity and remove air bubbles. Then, add 0.45g of wetting and dispersing agent BYK-190, 0.08g of defoamer BYK-024, 4g of talc powder (1250 mesh), and 17.5g of modified nano-cerium oxide powder to the tank in sequence. Increase the speed to 1000r / min and stir for 18min to allow the nano-filler to fully dissolve. After the material is fully pre-dispersed, the system is cooled to 26°C, and 6.5g of film-forming aid dipropylene glycol methyl ether, 0.5g of leveling agent BYK-333, and 0.08g of defoamer BYK-024 are added to the system at a speed of 450r / min. The mixture is stirred for 12min until it is uniformly mixed. Finally, 35g of deionized water is added to adjust the viscosity, and the mixture is stirred for 8min at a speed of 350r / min. After filtering through a 200-mesh filter to remove impurities, the wear-resistant alkyd resin coating is obtained.

[0042] Example 2-Example 3: A wear-resistant alkyd resin coating, which differs from Example 1 in that the amount of substance added in step S1 is different, while the other steps and parameters remain the same. The specific amount added is shown in Table 1 below.

[0043] Table 1. Comparison of the amount of substances used in step S1

[0044] Group Vegetable oil mixture (g) Formic acid (g) Hydrogen peroxide aqueous solution (g) Example 2 80 6.5 15 Example 3 120 8.5 20

[0045] Example 4-Example 5: A wear-resistant alkyd resin coating, which differs from Example 1 in that the amount of substance added in step S2 is different, while the other steps and parameters remain the same. The specific amount added is shown in Table 2 below.

[0046] Table 2 Comparison of the amount of relevant substances used in step S2

[0047] Group Epoxidized mixed vegetable oil (g) Methyltetrahydrophthalic anhydride (g) 2,4,6-Tris(dimethylaminomethyl)phenol (g) Example 4 100 20 0.2 Example 5 140 30 0.3

[0048] Example 6-Example 7: A wear-resistant alkyd resin coating and its preparation method. The difference from Example 1 is that the amount of substance added in step S3 is different, while the other steps and parameters remain the same. The specific amount added is shown in Table 3 below.

[0049] Table 3. Comparison of the amount of substances used in step S3

[0050] Group Modified blended vegetable oil (g) Cashew shell oil (g) Diethylene glycol (g) Benzoic acid (g) Terephthalic acid (g) Phthalic anhydride (g) Pentaerythritol (g) Xylene (g) Trimeric trioxide (g) Ethylene glycol monobutyl ether (g) Distilled water (g) Example 6 100 10.7 10.7 46.3 7.1 1.8 42.9 17.9 2 21.4 55 Example 7 100 28.6 28.6 64.3 21.4 5.4 60.7 28.6 7 42 70

[0051] Example 8: A wear-resistant alkyd resin coating, which differs from Example 1 in that the ratio of deionized water, phosphate betaine, cerium nitrate hexahydrate and sodium hydroxide aqueous solution in step S4 is 60mL:1g:16g:60mL, while the remaining steps and parameters remain the same.

[0052] The raw materials used in Examples 1-8 of this application are all commercially available. Castor oil, soybean oil, tung oil, formic acid, and pentaerythritol were purchased from Shanghai Aladdin Biochemical Co., Ltd.; hydrogen peroxide (analytical grade) was purchased from Chongqing Wansheng Chuandong Chemical Co., Ltd.; industrial grade methyltetrahydrophthalic anhydride and 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30) were purchased from Shanghai Resin Factory Co., Ltd.; cashew nut shell oil (99%) was purchased from Pande (Shanghai) International Trading Co., Ltd.; diethylene glycol (99%), benzoic acid (≥99%), terephthalic acid (99%), and phthalic acid... Dicarboxylic anhydride (99.7%) and xylene (99%) were purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; pentaerythritol was purchased from Hubei Yihua Chemical Co., Ltd.; trimellitic anhydride was purchased from Jinjinle Chemical Co., Ltd.; ethylene glycol monobutyl ether was purchased from Dow Chemical; wetting and dispersing agent BYK-190 and leveling agent BYK-333 were purchased from Guangzhou Yinman New Materials Co., Ltd.; defoamer BYK-024 was purchased from Guangdong Wengjiang Chemical Reagent Co., Ltd.; talc powder (1250 mesh) was purchased from Xi'an Jinxiang Pharmaceutical Excipients Co., Ltd.; dipropylene glycol methyl ether (purity 98%) was purchased from Shanghai Puzhen Biotechnology Co., Ltd.

[0053] Phosphate betaine was prepared from the reference ([1] Yan Xiuhua, Tang Lanqin. Synthesis and performance study of phosphate betaine modified ZnO[J]. Daily Chemical Industry (Chinese and English), 2025, 55(11):1402-1407.).

[0054] Comparative Example 1: Based on Example 1, steps S1 and S2 were omitted, and the modified mixed vegetable oil in step S3 was replaced with an unmodified original mixed vegetable oil (castor oil, soybean oil, and tung oil in a mass ratio of 5:3:2). All other steps and parameters remained the same as in Example 1, resulting in an alkyd resin coating.

[0055] Comparative Example 2: Based on Example 1, 100g of vegetable oil mixture in step S1 was replaced with 100g of castor oil, and castor oil was used as the only raw material for subsequent reactions. The amount of raw material added and the process parameters were kept the same as in Example 1, and alkyd resin coating was obtained.

[0056] Comparative Example 3: Based on Example 1, in step S4, the coating preparation stage, ordinary nano-cerium oxide powder without phosphate betaine (PB) treatment was used as filler with the same mass as the modified nano-cerium oxide powder in Example 1. Except for the change in filler, all other steps, raw material addition amounts and process parameters were kept consistent with Example 1 to obtain alkyd resin coating.

[0057] Films were prepared from the alkyd resin coatings prepared in Examples 1-8 and Comparative Examples 1-3: the dry film thickness was controlled to be 45±5μm by one-time coating. The coated test plate was placed horizontally and leveled for 10min under standard experimental conditions of temperature 23±2℃ and relative humidity 50±5%, and then placed in a constant temperature and humidity chamber for curing for 7d to allow it to fully cure, thus obtaining the test coating sample.

[0058] Subsequent performance tests were conducted based on this coating. Among them, the abrasion resistance was determined according to the method specified in GB / T 1768-2006. A rotary abrasion tester was used, and a standard rubber grinding wheel with a load of 1000g was used to rotate and rub the surface of the coating sample at 500r. The mass loss of the paint film (mg) was measured by a precision balance. The lower the value, the stronger the coating's resistance to friction and the better its abrasion resistance.

[0059] Hardness was determined according to the method specified in GB / T 6739-2006. A standard drawing pencil (6B to 9H) of known hardness was used to scratch the coating at a 45° angle. The highest hardness grade of the pencil that did not scratch the coating was taken as the pencil hardness of the coating. The higher the hardness grade, the stronger the surface rigidity of the coating.

[0060] The adhesion was tested according to the method specified in GB / T 9286-2021. A multi-functional cross-cutting tool was used to prepare a grid with a spacing of 1 mm on the paint film surface to the substrate. After cleaning, a special pressure-sensitive adhesive tape was applied and quickly peeled off. The degree of coating detachment from the grid was evaluated with reference to the standard chart (0-5 levels). Level 0 indicates that the cut edge is completely smooth and no grid has fallen off. The lower the rating, the stronger the coating adhesion.

[0061] The flexibility was determined according to the method specified in GB / T 1731-2020. The coated test panel was placed with the painted surface facing up and bent at a uniform speed of 180° on a shaft of a specified diameter (1mm-32mm) within 1 second. The coating at the bent part was observed with a 4x magnifying glass to see whether the coating produced a network pattern, cracks or peeling. The minimum shaft diameter (mm) that did not cause damage to the coating was used to evaluate the flexibility. The smaller the diameter, the better the flexibility of the coating.

[0062] The impact resistance test is conducted according to the method specified in GB / T 1732-2020 standard. An impact tester with a fixed height is used, and a 1kg weight is dropped freely to impact the coating on the back of the test plate. The drop height of the weight is gradually increased (5cm per increment). The coating at the impact point is checked for cracks, wrinkles, or peeling. The impact resistance is expressed as the product of the maximum impact height that does not cause damage to the coating and the weight (kg·cm). The higher the value, the stronger the coating's resistance to instantaneous impact.

[0063] The test results are shown in Table 4.

[0064] Table 4 Performance test results of various alkyd resin coatings

[0065]

[0066] As shown in Table 4, Examples 1-8 achieved a synergistic and breakthrough improvement in key mechanical properties of alkyd resin coatings, such as high wear resistance, excellent adhesion, good flexibility, and high impact resistance, by using an epoxidized mixed vegetable oil / anhydride modified resin synergistic film-forming system and a phosphate betaine (PB) surface-modified nano-cerium oxide functional enhancement system.

[0067] The abrasion resistance and impact resistance of the sample in Comparative Example 1 were the lowest among all groups, and its pencil hardness, adhesion, and flexibility all failed to meet the standards. This result may be because it completely adopted the traditional alkyd resin process, omitting the core epoxidized vegetable oil-anhydride ring-opening modification of this invention. On the one hand, the rigid benzene ring structure introduced by the ring-opening reaction of methyltetrahydrophthalic anhydride is missing as a crosslinking point of the molecular skeleton, resulting in the resin network lacking sufficient hardness and rigidity support, which macroscopically manifests as insufficient hardness and easy wear. On the other hand, the unmodified vegetable oil molecular chain is too flexible and has poor interfacial compatibility with inorganic fillers, resulting in stress concentration and accelerated crack propagation, which manifests as a significant decrease in impact resistance and flexibility. This result confirms from the opposite perspective that constructing a molecular structure that combines rigidity and flexibility is the fundamental prerequisite for achieving a balance between high abrasion resistance and high toughness in the coating, highlighting the cornerstone role of the resin chemical modification step of this invention.

[0068] The performance results of Comparative Example 2 were unsatisfactory because it only used castor oil as a raw material, lacking the castor oil-soybean oil-tung oil mixture system of this invention. Although castor oil contains hydroxyl groups which are beneficial to the reaction, its single structure cannot provide the balance between the high rigidity of the benzene ring unit provided by tung oil and the segment flexibility contributed by soybean oil. This results in the prepared resin matrix lacking sufficient rigidity to resist deformation and wear, and also making it difficult to optimize hardness and toughness due to the lack of diversified segment synergy. At the same time, the fatty acid composition from a single source may reduce the broad compatibility with nanofillers and substrates, manifested as a serious decrease in adhesion. This result proves that the mixing ratio of vegetable oils with specific functional combinations is the key design variable for regulating the overall performance of the resin, rather than a simple raw material substitution.

[0069] Although the performance of Comparative Example 3 was stronger than that of Comparative Examples 1 and 2, it was still significantly inferior to all examples. Its core defect was that the in-situ surface modification process of phosphate betaine in step S4 was omitted, and ordinary nano-cerium oxide was used directly. CeO2 nanoparticles without PB modification have extremely high surface energy, which will cause severe agglomeration in the hydrophobic resin matrix. These agglomerates become stress concentration points and structural weak points in the coating. Not only can they not exert the dispersion reinforcement and scratch resistance effect that nanoparticles should have, but they will also induce and accelerate the initiation and propagation of cracks, resulting in the wear resistance not achieving the expected improvement. At the same time, agglomeration also damages the interfacial bonding between the filler and the resin, affecting the overall rigidity. This result shows that the phosphate betaine surface treatment process is a key step to exert the function of nano-cerium oxide and realize the nano-reinforcement effect.

[0070] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0071] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing a wear-resistant alkyd resin coating, characterized in that, Prepared by the following steps: Step 1: The mixed vegetable oil undergoes an epoxidation reaction with hydrogen peroxide under the catalysis of formic acid. After extraction and purification, it is then reacted with methyltetrahydrophthalic anhydride to obtain the modified mixed vegetable oil. Specifically, the vegetable oil mixture is added to a reaction vessel, formic acid is added at 550-650 r / min, and a 30% (w / w) hydrogen peroxide aqueous solution is slowly added dropwise to the vessel over 30-45 min. After the addition is complete, the rotation speed is maintained and the temperature is raised to 58-62℃ to continue the reaction for 7-9 h. After the reaction is completed, the mixture is cooled to room temperature, and dichloromethane is added for extraction. After washing, drying, impurity removal, and concentration, epoxidized mixed vegetable oil is obtained. The mass ratio of the vegetable oil mixture, formic acid, and hydrogen peroxide aqueous solution is 80-120:6.5-8.5:15-20. The vegetable oil mixture is composed of castor oil, soybean oil and tung oil in a mass ratio of 4:3:

2. Nitrogen gas was introduced throughout the process. Epoxidized mixed vegetable oil, methyltetrahydrophthalic anhydride, and 2,4,6-tris(dimethylaminomethyl)phenol were added to the reactor and stirred evenly at 55-65℃ and 300-500 r / min. The mixture was then placed at 148-152℃ for 1.5-2.5 h to obtain modified mixed vegetable oil. Step 2: Modified mixed vegetable oil, cashew nut shell oil, polyol and polyacid are esterified and polycondensed, and then hydrophilically modified by trimellitic anhydride to prepare modified waterborne alkyd resin. Specifically, the modified mixed vegetable oil, cashew nut shell oil, diethylene glycol, benzoic acid, terephthalic acid, phthalic anhydride, pentaerythritol, and xylene are sequentially added to a reaction vessel and reacted at 250-350 r / min and 208-212℃ for 5-6 h. Trimeric trioxide is added at 70-80℃ and stirred and dispersed at 40-60 r / min for 10-12 min. The reaction is then carried out at 250-350 r / min and 158-162℃ for 2.5-3 h. Xylene is removed by vacuuming at 143-147℃. The temperature is lowered to 50℃ and ethylene glycol monobutyl ether and distilled water are added. After thorough stirring and mixing, the mixture is filtered to remove impurities, yielding the modified waterborne alkyd resin. Step 3: Using phosphate betaine as a modifier, cerium nitrate is modified by in-situ precipitation to obtain modified nano-cerium oxide powder; Step 4: Add the modified waterborne alkyd resin, modified nano-cerium oxide powder, talc powder, wetting and dispersing agent, defoamer, film-forming aid, leveling agent and deionized water into the mixing equipment, and disperse, mix and filter in steps to obtain the wear-resistant alkyd resin coating.

2. The method for preparing a wear-resistant alkyd resin coating according to claim 1, characterized in that, The mass ratio of the modified waterborne alkyd resin, modified nano-cerium oxide powder, talc powder, wetting and dispersing agent, defoamer, film-forming aid, leveling agent, and deionized water is 40-60:15-20:3-5:0.3-0.6:0.1-0.2:5-8:0.4-0.6:30-40.

3. The method for preparing a wear-resistant alkyd resin coating according to claim 1, characterized in that, The modified mixed vegetable oil, cashew nut shell oil, diethylene glycol, benzoic acid, terephthalic acid, phthalic anhydride, pentaerythritol, xylene, trimellitic anhydride, ethylene glycol monobutyl ether, and distilled water are in a mass ratio of 100:10.7-28.6:10.7-28.6:46.3-64.3:7.1-21.4:1.8-5.4:42.9-60.7:17.9-28.6:2-7:21.4-42:55-70.

4. The method for preparing a wear-resistant alkyd resin coating according to claim 1, characterized in that, The mass ratio of the epoxidized mixed vegetable oil, methyltetrahydrophthalic anhydride, and 2,4,6-tris(dimethylaminomethyl)phenol is 100-140:20-30:0.2-0.

3.

5. The method for preparing a wear-resistant alkyd resin coating according to claim 1, characterized in that, The specific preparation steps of the modified nano-cerium oxide powder are as follows: Deionized water and phosphate betaine were added to the reaction vessel and stirred at 300-500 r / min until dissolved. Then, cerium nitrate hexahydrate was added and stirred evenly. Under continuous stirring at 65-75℃, an 8.4 wt% sodium hydroxide aqueous solution was added dropwise over 30 min. After the addition was complete, the reaction was carried out for 1.5-2.5 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain modified nano-cerium oxide powder. The ratio of deionized water, phosphate betaine, cerium nitrate hexahydrate, and sodium hydroxide aqueous solution is 40-60 mL: 0.5-1 g: 14-16 g: 40-60 mL.

6. A wear-resistant alkyd resin coating, characterized in that, It is prepared by the preparation method described in any one of claims 1-5.

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