Lathe machining aluminum skimming scratch resistant coating for motorcycle wheel hub and preparation process of lathe machining aluminum skimming scratch resistant coating

Abstract

The invention provides a lathe machining aluminum scrap scratch resistant coating for motorcycle hubs and a preparation process thereof, and belongs to the technical field of coatings, the preparation process comprises the following steps: S1, preparing silicon-zirconium hybrid sol; step S2, preparing an epoxy modified prepolymer solution; s3, adding a hydroxy acrylic resin solution into a reaction kettle, stirring, adding butyl acetate and sec-butyl acetate, stirring, adding hexamethoxymethyl melamine, the epoxy modified prepolymer solution, BYK4510, organobentonite and propylene carbonate, stirring, adding the silicon-zirconium hybrid sol, stirring, adding BYK333, BYK-066N, polyethylene micro-powder wax and PTFE micro-powder, stirring at a reduced speed, and cooling to room temperature to obtain a coating; and finally, adding the aluminum paste mixture, uniformly mixing, and filtering to obtain the lathe machining aluminum scrap scratch resistant coating for the motorcycle hub. The coating provided by the invention can realize the purposes of scratch resistance, stripping resistance and good appearance maintenance of the coating for resisting the scratch of the lathe machining aluminum scraps for the motorcycle hub.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a coating for motorcycle wheel hubs that resists scratches from lathe machining and aluminum shavings, and its preparation process. Background Technology

[0002] Motorcycle wheels are typically made of aluminum alloy, and their appearance and corrosion resistance significantly impact the overall quality and market acceptance of the vehicle. To achieve a metallic finish, luster, and weather-resistant protection, the industry commonly employs solvent-based or powder coating systems (such as acrylic / polyester resins combined with amino resins for baking and cross-linking, or metallic finishes combined with clear varnish) to form a decorative protective film with a certain degree of hardness, adhesion, and wear resistance.

[0003] In the wheel manufacturing process, lathe / CNC machining (such as end face finishing, inner and outer circle trimming, chamfering, etc.) is often required to ensure dimensional accuracy and assembly requirements. This machining process generates a large amount of fine, long, or flaky aluminum chips. These chips have sharp edges and high hardness, and under cutting forces, they may come into instantaneous high-pressure contact with the coated surface, causing slippage, plowing, or repeated scratching. Simultaneously, the aluminum chips easily carry cutting fluid, dust, and oxide particles, further exacerbating "biting" scratches and surface contamination. These scratches differ from ordinary wear, often manifesting as deep grooves, significant scratches, damage to the metallic effect, localized whitening, or a sudden drop in gloss. In severe cases, they may even induce the propagation of micro-cracks at the coating edges, leading to subsequent peeling, flaking, and the penetration of corrosive media, resulting in failures.

[0004] In existing technologies, common methods to improve scratch resistance include: increasing the crosslinking density of the coating to obtain higher hardness; introducing inorganic fillers or nanoparticles (such as silica, alumina, zirconium oxide, etc.) into the system to enhance the surface's resistance to indentation; adding low-friction solid lubricating phases such as wax powder and PTFE to reduce the coefficient of friction; or using sol-gel inorganic network / organic resin hybridization to improve wear resistance and scratch resistance. However, the above solutions still have limitations when facing the harsh working condition of "sharp plowing of aluminum chips": on the one hand, simply increasing the hardness and crosslinking density can easily lead to coating embrittlement and increased internal stress, making it more prone to stress whitening, edge chipping, and crack propagation when scratched, and may reduce the interfacial peel resistance to the aluminum alloy substrate; on the other hand, if the dispersion control of inorganic particles or sol systems is poor, agglomeration is likely to occur, forming "hard spots / particle defects," and micro-protrusions and stress concentration sources are generated on the coating surface, which become the preferential damage sites under the action of aluminum chips, making the scratches more obvious and the appearance worse. Furthermore, in actual production, it is necessary to take into account the application viscosity window, storage stability, and appearance retention after baking and curing, making it more difficult to achieve a comprehensive balance between "high hardness and scratch resistance" and "toughness / adhesion / appearance".

[0005] Therefore, there is a need to provide a coating for motorcycle wheel hubs that resists scratches from lathe machining and aluminum shavings, as well as its preparation process, to solve the problems existing in the prior art. Summary of the Invention

[0006] In view of this, the present invention provides a coating for motorcycle wheel hubs that resists scratches from lathe machining and aluminum shavings, and its preparation process, which can achieve the purpose of scratch resistance, peel resistance, and good appearance maintenance of the coating for motorcycle wheel hubs that resists scratches from lathe machining and aluminum shavings.

[0007] To achieve the above objectives, the present invention provides a preparation process for a coating for motorcycle wheel hubs that resists scratches from lathe machining and aluminum shavings, comprising the following steps: Step S1: Add zirconium propoxide and acetylacetone to n-butanol to obtain a zirconium complex solution, slowly add it dropwise into the silica sol precursor, stir, age, filter, and obtain a silicon-zirconium hybrid sol. Step S2: Add bisphenol A type epoxy resin and butyl acetate to the reaction vessel, heat and stir to dissolve, add adipic acid and zinc acetylacetonate to react, filter to obtain epoxy modified prepolymer solution. Step S3: Add the hydroxyl acrylic resin solution to the reaction vessel and stir. Add butyl acetate and sec-butyl acetate and stir. Add hexamethoxymethyl melamine, epoxy modified prepolymer solution, BYK4510, organobentonite and propylene carbonate and stir. Add silicon zirconium hybrid sol and stir. Then add BYK333, BYK-066N, polyethylene micro powder wax and PTFE micro powder and stir at a reduced speed. Finally, add aluminum silver paste mixture and mix well. Filter to obtain a coating for anti-machine tooling aluminum shavings scratches on motorcycle wheel hubs.

[0008] Zirconium n-propoxide is highly reactive; if it comes into direct contact with water / hydroxyl groups, it readily hydrolyzes and condenses to form ZrO2-like aggregates, which become hard particle defects in the coating film, easily leading to scratches. After acetylacetone complexes with Zr(IV), it can reduce the hydrolysis rate of the zirconium source, allowing it to participate in the condensation reaction in a "controlled manner," resulting in a more uniform zirconium distribution and finer inorganic structural units. Slowly adding the zirconium complex solution eliminates local concentration gradients and exothermic reactions, making zirconium more likely to co-condense with Si-OH in the silica sol, forming Zr-O-Si bonds rather than self-aggregating into coarse zirconium-oxygen clusters. This creates a true silicon-zirconium hybrid network, improving the coating surface's resistance to indentation and abrasion. Further filtration removes small amounts of gel cores / impurity particles, directly reducing "hard spots" and "stress concentration sources" in the coating film. The final product is a silicon-zirconium hybrid sol with more uniform particle size and structure, and a surface that is easier to couple with the resin, thereby improving the coating's resistance to indentation and abrasion, and reducing scratches caused by hard defects.

[0009] Adipic acid undergoes ring-opening addition / esterification with epoxy, introducing aliphatic methylene segments and ester bonds into the prepolymer. In highly cross-linked systems, these structures provide microscopic yield and shear band energy dissipation, converting concentrated stress during scratching into dispersed plastic energy dissipation, thereby inhibiting microcrack propagation and stress whitening. Zinc complexation catalysis improves reaction controllability, avoiding excessive reaction leading to high internal stress and brittleness (higher internal stress makes aluminum scratches more prone to whitening and peeling). The polar structures such as ester groups / residual epoxy in the prepolymer enhance wetting and interaction forces on the aluminum alloy oxide film and sol particle surface, making the coating more prone to "intra-film energy dissipation" rather than "interfacial peeling propagation" after scratching. By introducing controllable flexible ester segments into the epoxy system and adjusting the degree of reaction, toughening and interfacial strengthening of the coating are achieved under high hardness conditions, thereby reducing whitening, edge chipping, and peeling propagation induced by aluminum scratches.

[0010] First, a hydroxyl acrylic resin solution, butyl acetate, and sec-butyl acetate are added to establish a basic continuous phase and a suitable viscosity window, ensuring that subsequent crosslinking agents, sols, and fillers can be fully wetted and uniformly dispersed, avoiding agglomeration. Then, hexamethoxymethyl melamine, an epoxy-modified prepolymer solution, dispersant BYK4510, organobentonite, and propylene carbonate are added. This establishes the future crosslinking network (hexamethoxymethyl melamine + hydroxyl acrylic acid) and, through the action of the polar activator (propylene carbonate), forms a thixotropic framework, stabilizing the structure. The system is stabilized and sedimentation is suppressed to ensure uniform coating film thickness and component distribution. Subsequently, a silicon-zirconium hybrid sol is added, allowing the sol-reinforced phase to enter the established resin / rheological network environment and be "locked" in the continuous phase, preventing localized agglomeration. Next, BYK333, BYK-066N, and PE wax powder / PTFE micro-powder are added to control surface / interface defects (leveling, defoaming) and introduce a low-friction solid phase. Finally, an aluminum silver paste mixture is added to maximize the protection of aluminum flake morphology and orientation, preventing high shear from causing aluminum flake breakage, curling, or re-flocculation. Ultimately, a uniform coating microstructure, minimal defects, and low surface friction are achieved, thus resisting aluminum chip scratches while also providing resistance to indentation, ploughing, and visible defects.

[0011] Preferably, the aging time is 12-24 hours.

[0012] The aging stage allows the hydrolysis and condensation of the silicon-zirconium system to reach a more suitable "partially cross-linked stable state". On the one hand, it consumes active Si-OH / Zr-OR to avoid agglomeration caused by the subsequent rapid reaction in the main reactor; on the other hand, it makes the functional groups on the surface of the particles more uniformly distributed, thereby forming a more stable sol dispersion in the organic resin.

[0013] Preferably, the preparation of the silica sol precursor includes the following steps: KH560, methyltrimethoxysilane and n-butanol were mixed and stirred to obtain a mixture; deionized water, glacial acetic acid and n-butanol were mixed to prepare a hydrolysate, which was added dropwise to the mixture. After the addition was complete, stirring was continued to obtain the silica sol precursor.

[0014] Preferably, in step S2, the epoxy equivalent of the bisphenol A type epoxy resin is 450-550 g / eq; the temperature for heating and stirring is 110-120℃; the reaction temperature is 130-140℃; and the reaction time is 120-180 min.

[0015] Preferably, the preparation of the aluminum silver paste mixture includes the following steps: adding aluminum silver paste, butyl acetate and sodium polyacrylate into a reaction vessel and stirring evenly to obtain the aluminum silver paste mixture; the aluminum silver paste mixture includes the following components in parts by weight: 55-66 parts aluminum silver paste, 25-30 parts butyl acetate and 0.3-0.36 parts sodium polyacrylate.

[0016] Sodium polyacrylate, added in powder form as a dispersion stabilizer, forms an electrically / sterically stabilizing layer on the aluminum sheet surface, inhibiting secondary adsorption and flocculation between aluminum sheets. Butyl acetate provides a suitable solvent environment and viscosity conditions, facilitating the wetting, spreading, and uniform distribution of the aluminum sheets. After the aluminum sheets are uniformly dispersed, hard spots or weak points are less likely to appear in the coating, thus reducing the probability of aluminum chips "biting" at these defects.

[0017] Preferably, in step S3, the solid content of the hydroxyl acrylic resin solution is 59-61 wt%, the Tg is 55-65℃, and the average molecular weight is 8000-12000.

[0018] Preferably, in step S3, double-walled microcapsule powder is added and stirred before adding the aluminum silver paste mixture; the preparation of the double-walled microcapsule powder includes the following steps: Polysulfone was added to NMP and stirred until clear. 1-Ethyl-3-methylimidazolium diethyl phosphate was added and stirring continued to obtain the inner phase. PVA aqueous solution was placed in an emulsification vessel, and the inner phase was added dropwise under high shear conditions to obtain an emulsion. The rotation speed was adjusted, and deionized water was slowly added. The mixture was stirred, centrifuged, washed, and transferred to an ethanol solution. Ammonia water was then added, and the mixture was stirred evenly. TEOS was added dropwise to carry out the reaction. The mixture was filtered, washed, and dried to obtain double-walled microcapsule powder.

[0019] The polysulfone inner wall provides a high-strength, solvent-resistant skeleton, preventing swelling failure in the solvent / crosslinking agent environment of the main reactor; 1-ethyl-3-methylimidazolium diethyl phosphate, as the core material, has the characteristics of low volatility, strong polarity, and easy formation of adsorption layers on metal / oxide surfaces, forming a stable boundary lubrication film at the friction interface; TEOS (ethyl silicate) forms a SiO2 shell under ammonia catalysis, which enhances shear resistance and swelling resistance, and is more prone to brittle fracture under the action of sharp aluminum chips, realizing the "release when it should" trigger response. When scratches occur, the microcapsules rupture at the stress concentration point of the groove, allowing 1-ethyl-3-methylimidazolium diethyl phosphate to spread and adsorb, thereby reducing shear resistance, making aluminum chips easier to slide, and reducing the coefficient of friction and plowing depth.

[0020] Preferably, the rotational speed under high shear conditions is 8000-10000 rpm; the adjusted rotational speed is 400-600 rpm; the concentration of ammonia is 25-28 wt%, the concentration of PVA aqueous solution is 1-1.5 wt%, and the concentration of ethanol solution is 75-85 wt%.

[0021] Ammonia solution with a concentration of 25-28 wt% causes TEOS to condense within a window of "rapid shell formation without excessive roughness / brittleness". If the shell is too thin, it is easy to leak prematurely, while if it is too thick, it is not easy to trigger release and may introduce hard spots.

[0022] Preferably, the double-walled microcapsule powder comprises the following components in parts by weight: 10-12 parts polysulfone, 88-90 parts NMP and 18-25 parts 1-ethyl-3-methylimidazolium diethyl phosphate; and further comprises the following components in parts by volume: 500 parts PVA aqueous solution, 300-400 parts deionized water, 400 parts ethanol solution, 1-1.5 parts ammonia and 6-10 parts TEOS.

[0023] To achieve the above objectives, the present invention also provides a motorcycle wheel hub anti-machine tooling aluminum shavings scratch coating prepared by the above-described preparation process, comprising the following components in parts by weight: The mixture comprises 289-359 parts of hydroxyl acrylic resin, 130-156 parts of hexamethoxymethyl melamine, 45-54 parts of epoxy modified prepolymer solution, 71.5-85.8 parts of butyl acetate, 50-60 parts of sec-butyl acetate, 55-66 parts of silicon-zirconium hybrid sol, 18-21.6 parts of BYK4510, 12-14.4 parts of organobentonite, 1.2-1.44 parts of propylene carbonate, 2.5-3 parts of BYK333, 2-2.4 parts of BYK-066N, 25-30 parts of polyethylene micronized wax, 10-12 parts of PTFE micronized powder, and 80.3-96.36 parts of aluminum silver paste mixture.

[0024] The anti-scratch coating for motorcycle wheel hubs prepared using the process of this invention can achieve the goals of scratch resistance, peel resistance, and good appearance maintenance.

[0025] The above-described technical solution of the present invention has at least the following beneficial effects: 1. By following the path of "complexation and slow release - controlled co-condensation - aging and stabilization - filtration and nucleation", a silicon-zirconium hybrid sol with more uniform particle size and structure and a surface that is easier to couple with the resin is obtained, thereby improving the coating's resistance to indentation and abrasion from the source and reducing scratches caused by hard defects.

[0026] 2. By introducing controllable flexible ester segments into the epoxy system and adjusting the degree of reaction, toughening and interface strengthening of the coating film under high hardness background are achieved, thereby reducing whitening, edge chipping and peeling propagation induced by aluminum chip scratches.

[0027] 3. By following the sequence of "first building a continuous phase and thixotropic framework, then uniformly introducing nano-sol reinforcement, then controlling surface defects and constructing a low-friction solid phase, and finally introducing low-shear aluminum sheets", the coating achieves uniform microstructure, minimal defects, and low surface friction, thereby resisting aluminum chip scratches while also resisting indentation, ploughing, and visible defects. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. The described embodiments are some embodiments of the present invention, and all other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0029] The hydroxy acrylic resin solution used in the embodiments of this application has a solid content of 59-61 wt%, a Tg of 55-65℃, and an average molecular weight of 8000-12000; the hydroxy acrylic resin solutions used in the following embodiments are all of the above specifications.

[0030] Example 1 125g KH560, 55g methyltrimethoxysilane, and 215g n-butanol were mixed and stirred at 25°C for 10 min to obtain a mixture. 20g deionized water, 0.6g glacial acetic acid, and 85g n-butanol were mixed to prepare a hydrolysate, which was then added dropwise to the mixture at 25°C over a period of 40 min. After the addition was complete, stirring was continued for 75 min to obtain a silica sol precursor. Separately, 50g n-zirconium propoxide and 33g acetylacetone were added to 160g n-butanol and stirred at 25°C for 30 min to obtain a zirconium complex solution. This solution was slowly added dropwise to the silica sol precursor, and stirring was continued for 135 min. The mixture was then aged at room temperature for 18 h and filtered to obtain a silicon-zirconium hybrid sol.

[0031] 95g of bisphenol A type epoxy resin (epoxy equivalent of 450-550g / eq) and 58g of butyl acetate were added to a reaction vessel, heated to 115℃ and stirred to dissolve. 22g of adipic acid and 0.35g of zinc acetylacetonate were added, the temperature was raised to 138℃, and the reaction was carried out for 180min. The mixture was then filtered to obtain an epoxy-modified prepolymer solution.

[0032] 10g of polysulfone was added to 89g of NMP and stirred at 60℃ until clear. 18g of 1-ethyl-3-methylimidazolium diethyl phosphate was added and stirred for 30min to obtain the internal phase. 500mL of 1.15wt% PVA aqueous solution was placed in an emulsification vessel, and the internal phase was added dropwise at 8000rpm for 12min. Emulsification was continued for 3min to obtain an emulsion. The stirring speed was adjusted to 480rpm, and 400mL of deionized water was slowly added at 30℃. The mixture was stirred for 60min, centrifuged, washed, and added to 400mL of ethanol solution (ethanol concentration 80wt%). 1.3mL of ammonia (25wt%) was added, and the mixture was stirred evenly at 25℃. 8mL of TEOS was added dropwise, and the reaction was carried out for 120min. The mixture was filtered, washed, and vacuum dried at 60℃ for 12h to obtain double-walled microcapsule powder.

[0033] Add 58g of aluminum silver paste, 25g of butyl acetate and 0.35g of sodium polyacrylate to the reaction vessel and stir evenly to obtain the aluminum silver paste mixture. 570g of hydroxyl acrylic resin solution was added to a reaction vessel and stirred at 600rpm. 75.7g of butyl acetate and 60g of sec-butyl acetate were added and stirred for 9 minutes. Then, 143g of hexamethoxymethyl melamine, 51g of epoxy-modified prepolymer solution, 21g of BYK4510, 14.4g of organobentonite, and 1.44g of propylene carbonate were added and stirred for 10 minutes. 66g of silicon-zirconium hybrid sol was added and stirred for another 15 minutes at 30°C. Then, 2.65g of BYK333, 2.4g of BYK-066N, 30g of polyethylene micronized wax, and 11g of PTFE micronized powder were added and stirred for 10 minutes. The stirring speed was reduced to 200rpm, and 6.7g of double-walled microcapsule powder was added and stirred for 5 minutes. Finally, 83.35g of aluminum silver paste mixture was added, stirred evenly, and filtered to obtain a coating for motorcycle wheel hubs resistant to machine tool scratches from aluminum shavings.

[0034] Example 2 120g KH560, 60g methyltrimethoxysilane, and 230g n-butanol were mixed and stirred at 30°C for 10 min to obtain a mixture. 22g deionized water, 0.8g glacial acetic acid, and 90g n-butanol were mixed to prepare a hydrolysate, which was then added dropwise to the mixture at 25°C over a time of 45 min. After the addition was complete, stirring was continued for 60 min to obtain a silica sol precursor. Separately, 45g n-zirconium propoxide and 30g acetylacetone were added to 150g n-butanol and stirred at 30°C for 30 min to obtain a zirconium complex solution. This solution was slowly added dropwise to the silica sol precursor, and stirring was continued for 120 min. The mixture was then aged at room temperature for 24 h and filtered to obtain a silicon-zirconium hybrid sol.

[0035] 110g of bisphenol A type epoxy resin (epoxy equivalent of 450-550g / eq) and 55g of butyl acetate were added to a reaction vessel, heated to 110℃ and stirred to dissolve. 19g of adipic acid and 0.2g of zinc acetylacetonate were added, the temperature was raised to 133℃, and the reaction was carried out for 130min. The mixture was then filtered to obtain an epoxy-modified prepolymer solution.

[0036] 11 g of polysulfone was added to 90 g of NMP and stirred at 60 °C until clear. 25 g of 1-ethyl-3-methylimidazolium diethyl phosphate was added and stirring was continued for 30 min to obtain the internal phase. 500 mL of 1.5 wt% PVA aqueous solution was placed in an emulsification vessel, and the internal phase was added dropwise under high shear conditions of 8500 rpm for 9 min. Emulsification was continued for 4 min to obtain an emulsion. The stirring speed was adjusted to 400 rpm, and 350 mL of deionized water was slowly added at 28 °C. Stirring was continued for 60 min, centrifuged, washed, and added to 400 mL of ethanol solution (ethanol concentration of 75 wt%). Then, 1.5 mL of ammonia water (28 wt%) was added, and the mixture was stirred evenly at 30 °C. 6 mL of TEOS was added dropwise, and the reaction was carried out for 120 min. The mixture was filtered, washed, and vacuum dried at 60 °C for 12 h to obtain double-walled microcapsule powder.

[0037] Add 55g of aluminum silver paste, 25g of butyl acetate and 0.36g of sodium polyacrylate to the reaction vessel and stir evenly to obtain the aluminum silver paste mixture. 560g of hydroxyl acrylic resin solution was added to a reaction vessel and stirred at 650rpm. 82.3g of butyl acetate and 58g of sec-butyl acetate were added and stirred for 8 minutes. Then, 151g of hexamethoxymethyl melamine, 47g of epoxy-modified prepolymer solution, 19g of BYK4510, 13g of organobentonite, and 1.3g of propylene carbonate were added and stirred for 10 minutes. 58g of silicon-zirconium hybrid sol was added and stirred for another 15 minutes at 30°C. Then, 2.8g of BYK333, 2g of BYK-066N, 28g of polyethylene micronized wax, and 12g of PTFE micronized powder were added and stirred for 10 minutes. The stirring speed was reduced to 370rpm, and 7.2g of double-walled microcapsule powder was added and stirred for 5 minutes. Finally, 80.3g of aluminum silver paste mixture was added, stirred evenly, and filtered to obtain a coating for motorcycle wheel hubs resistant to machine tool scratches from aluminum shavings.

[0038] Example 3 130g KH560, 50g methyltrimethoxysilane, and 200g n-butanol were mixed and stirred at 25°C for 10 min to obtain a mixture. 18g deionized water, 0.4g glacial acetic acid, and 80g n-butanol were mixed to prepare a hydrolysate, which was then added dropwise to the mixture at 25°C over a period of 30 min. After the addition was complete, stirring was continued for 90 min to obtain a silica sol precursor. Separately, 55g n-zirconium propoxide and 35g acetylacetone were added to 170g n-butanol and stirred at 25°C for 30 min to obtain a zirconium complex solution. This solution was slowly added dropwise to the silica sol precursor, and stirring was continued for 150 min. The mixture was then aged at room temperature for 12 h and filtered to obtain a silicon-zirconium hybrid sol.

[0039] 100g of bisphenol A type epoxy resin (epoxy equivalent of 450-550g / eq) and 60g of butyl acetate were added to a reaction vessel, heated to 120℃ and stirred to dissolve. 18g of adipic acid and 0.27g of zinc acetylacetonate were added, the temperature was raised to 135℃, and the reaction was carried out for 180min. The mixture was then filtered to obtain an epoxy-modified prepolymer solution.

[0040] 11g of polysulfone was added to 90g of NMP and stirred at 60℃ until clear. 18g of 1-ethyl-3-methylimidazolium diethyl phosphate was added and stirring was continued for 30min to obtain the internal phase. 500mL of 1wt% PVA aqueous solution was placed in an emulsification vessel, and the internal phase was added dropwise under high shear conditions of 9500rpm for 10min. Emulsification was continued for 3min to obtain an emulsion. The speed was adjusted to 600rpm, and 300mL of deionized water was slowly added at 28℃. Stirring was continued for 60min, centrifuged, washed, and added to 400mL of ethanol solution (ethanol concentration of 80wt%). 1.5mL of ammonia water (25wt%) was added, and the mixture was stirred evenly at 28℃. 10mL of TEOS was added dropwise, and the reaction was carried out for 120min. The mixture was filtered, washed, and vacuum dried at 60℃ for 12h to obtain double-walled microcapsule powder.

[0041] Add 66g of aluminum silver paste, 30g of butyl acetate and 0.36g of sodium polyacrylate to the reaction vessel and stir until homogeneous to obtain the aluminum silver paste mixture. Add 588g of hydroxyl acrylic resin solution to the reactor and stir at 620rpm. Add 80.5g of butyl acetate and 52g of sec-butyl acetate and stir for 5min. Then add 156g of hexamethoxymethyl melamine, 54g of epoxy modified prepolymer solution, 18g of BYK4510, 13.3g of organobentonite and 1.33g of propylene carbonate and stir for 10min. Add 58g of silicon-zirconium hybrid sol and continue stirring at 30℃ for 15min. Then add 2.5g of BYK333, 2g of BYK-066N, 27g of polyethylene micron wax and 10g of PTFE micron powder and stir for 10min. Reduce the speed to 400rpm and add 6g of double-walled microcapsule powder and stir for 5min. Finally, add 96.36g of aluminum silver paste mixture, stir evenly, filter, and obtain a coating for motorcycle wheel hubs that resists machine tool scratches from aluminum shavings.

[0042] Example 4 120g KH560, 60g methyltrimethoxysilane, and 200g n-butanol were mixed and stirred at 30°C for 10 min to obtain a mixture. 18g deionized water, 0.7g glacial acetic acid, and 85g n-butanol were mixed to prepare a hydrolysate, which was then added dropwise to the mixture at 25°C over a time of 45 min. After the addition was complete, stirring was continued for 90 min to obtain a silica sol precursor. Separately, 50g n-zirconium propoxide and 32g acetylacetone were added to 150g n-butanol and stirred at 27°C for 30 min to obtain a zirconium complex solution. This solution was slowly added dropwise to the silica sol precursor, and stirring was continued for 150 min. The mixture was then aged at room temperature for 12 h and filtered to obtain a silicon-zirconium hybrid sol.

[0043] 100g of bisphenol A type epoxy resin (epoxy equivalent of 450-550g / eq) and 60g of butyl acetate were added to a reaction vessel, heated to 113℃ and stirred to dissolve. 20g of adipic acid and 0.2g of zinc acetylacetonate were added, the temperature was raised to 130℃, and the reaction was carried out for 150min. The mixture was then filtered to obtain an epoxy-modified prepolymer solution.

[0044] 10g of polysulfone was added to 88g of NMP and stirred at 60℃ until clear. 22g of 1-ethyl-3-methylimidazolium diethyl phosphate was added and stirring was continued for 30min to obtain the internal phase. 500mL of 1.2wt% PVA aqueous solution was placed in an emulsification vessel, and the internal phase was added dropwise under high shear conditions of 10000rpm for 12min. Emulsification was continued for 5min to obtain an emulsion. The stirring speed was adjusted to 500rpm, and 380mL of deionized water was slowly added at 25℃. Stirring was continued for 60min, centrifuged, washed, and added to 400mL of ethanol solution (ethanol concentration of 75wt%). Then, 1.35mL of ammonia water (27wt%) was added, and the mixture was stirred evenly at 30℃. 10mL of TEOS was added dropwise, and the reaction was carried out for 120min. The mixture was filtered, washed, and vacuum dried at 60℃ for 12h to obtain double-walled microcapsule powder.

[0045] Add 61g of aluminum silver paste, 27g of butyl acetate and 0.33g of sodium polyacrylate to the reaction vessel and stir until homogeneous to obtain the aluminum silver paste mixture. Add 510g of hydroxyl acrylic resin solution to the reactor and stir at 670rpm. Add 82g of butyl acetate and 50g of sec-butyl acetate and stir for 10min. Then add 156g of hexamethoxymethyl melamine, 51g of epoxy modified prepolymer solution, 19g of BYK4510, 14.4g of organobentonite and 1.44g of propylene carbonate and stir for 10min. Add 66g of silicon-zirconium hybrid sol and continue stirring at 30℃ for 15min. Then add 2.8g of BYK333, 2g of BYK-066N, 30g of polyethylene micron wax and 11g of PTFE micron powder and stir for 10min. Reduce the speed to 350rpm and add 6.8g of double-walled microcapsule powder and stir for 5min. Finally, add 88.33g of aluminum silver paste mixture, stir evenly, filter, and obtain a coating for motorcycle wheel hubs that resists machine tool scratches from aluminum shavings.

[0046] Example 5 120g KH560, 50g methyltrimethoxysilane, and 230g n-butanol were mixed and stirred at 25°C for 10 min to obtain a mixture. 22g deionized water, 0.4g glacial acetic acid, and 90g n-butanol were mixed to prepare a hydrolysate, which was then added dropwise to the mixture at 27°C over a period of 40 min. After the addition was complete, stirring was continued for 75 min to obtain a silica sol precursor. Separately, 45g n-zirconium propoxide and 30g acetylacetone were added to 170g n-butanol and stirred at 25°C for 30 min to obtain a zirconium complex solution. This solution was slowly added dropwise to the silica sol precursor, and stirring was continued for 140 min. The mixture was then aged at room temperature for 15 h and filtered to obtain a silicon-zirconium hybrid sol.

[0047] 100g of bisphenol A type epoxy resin (epoxy equivalent of 450-550g / eq) and 70g of butyl acetate were added to a reaction vessel, heated to 115℃ and stirred to dissolve. 15g of adipic acid and 0.35g of zinc acetylacetonate were added, the temperature was raised to 140℃, and the reaction was carried out for 150min. The mixture was then filtered to obtain an epoxy-modified prepolymer solution.

[0048] 12g of polysulfone was added to 89g of NMP and stirred at 60℃ until clear. 21g of 1-ethyl-3-methylimidazolium diethyl phosphate was added and stirring was continued for 30min to obtain the internal phase. 500mL of 1.4wt% PVA aqueous solution was placed in an emulsification vessel, and the internal phase was added dropwise under high shear conditions of 9000rpm for 8min. Emulsification was continued for 5min to obtain an emulsion. The stirring speed was adjusted to 550rpm, and 350mL of deionized water was slowly added at 27℃. Stirring was continued for 60min, centrifuged, washed, and added to 400mL of ethanol solution (ethanol concentration of 80wt%). Then, 1mL of ammonia water (28wt%) was added, and the mixture was stirred evenly at 25℃. 8mL of TEOS was added dropwise, and the reaction was carried out for 120min. The mixture was filtered, washed, and vacuum dried at 60℃ for 12h to obtain double-walled microcapsule powder.

[0049] Add 55g of aluminum silver paste, 25g of butyl acetate and 0.3g of sodium polyacrylate to the reaction vessel and stir evenly to obtain the aluminum silver paste mixture. 490g of hydroxyl acrylic resin solution was added to a reaction vessel and stirred at 780rpm. 71.5g of butyl acetate and 60g of sec-butyl acetate were added and stirred for 5min. Then, 130g of hexamethoxymethyl melamine, 51g of epoxy-modified prepolymer solution, 21.6g of BYK4510, 13g of organobentonite, and 1.3g of propylene carbonate were added and stirred for 10min. 55g of silicon-zirconium hybrid sol was added and stirred for 15min at 30℃. Then, 3g of BYK333, 2.1g of BYK-066N, 25g of polyethylene micronized wax, and 12g of PTFE micronized powder were added and stirred for 10min. The stirring speed was reduced to 250rpm, and 6.2g of double-walled microcapsule powder was added and stirred for 5min. Finally, 80.3g of aluminum silver paste mixture was added, stirred evenly, and filtered to obtain a coating for motorcycle wheel hubs resistant to machine tool scratches from aluminum shavings.

[0050] Example 6 130g KH560, 60g methyltrimethoxysilane, and 215g n-butanol were mixed and stirred at 28°C for 10 min to obtain a mixture. 20g deionized water, 0.8g glacial acetic acid, and 80g n-butanol were mixed to prepare a hydrolysate, which was then added dropwise to the mixture at 30°C over a period of 30 min. After the addition was complete, stirring was continued for 60 min to obtain a silica sol precursor. Separately, 55g n-zirconium propoxide and 35g acetylacetone were added to 160g n-butanol and stirred at 30°C for 30 min to obtain a zirconium complex solution. This solution was slowly added dropwise to the silica sol precursor, and stirring was continued for 120 min. The mixture was then aged at room temperature for 24 h and filtered to obtain a silicon-zirconium hybrid sol.

[0051] 105g of bisphenol A type epoxy resin (epoxy equivalent of 450-550g / eq) and 65g of butyl acetate were added to a reaction vessel, heated to 110℃ and stirred to dissolve. 20g of adipic acid and 0.15g of zinc acetylacetonate were added, the temperature was raised to 130℃, and the reaction was carried out for 120min. The mixture was then filtered to obtain an epoxy-modified prepolymer solution.

[0052] 11g of polysulfone was added to 90g of NMP and stirred at 60℃ until clear. 18g of 1-ethyl-3-methylimidazolium diethyl phosphate was added and stirring was continued for 30min to obtain the internal phase. 500mL of 1wt% PVA aqueous solution was placed in an emulsification vessel, and the internal phase was added dropwise under high shear conditions of 9500rpm for 10min. Emulsification was continued for 3min to obtain an emulsion. The speed was adjusted to 600rpm, and 300mL of deionized water was slowly added at 28℃. Stirring was continued for 60min, centrifuged, washed, and added to 400mL of ethanol solution (ethanol concentration of 80wt%). 1.5mL of ammonia water (25wt%) was added, and the mixture was stirred evenly at 28℃. 10mL of TEOS was added dropwise, and the reaction was carried out for 120min. The mixture was filtered, washed, and vacuum dried at 60℃ for 12h to obtain double-walled microcapsule powder.

[0053] Add 66g of aluminum silver paste, 30g of butyl acetate and 0.36g of sodium polyacrylate to the reaction vessel and stir until homogeneous to obtain the aluminum silver paste mixture. 525g of hydroxyl acrylic resin solution was added to a reaction vessel and stirred at 800 rpm. 85.8g of butyl acetate and 55g of sec-butyl acetate were added and stirred for 8 minutes. Then, 140g of hexamethoxymethyl melamine, 45g of epoxy-modified prepolymer solution, 18g of BYK4510, 12g of organobentonite, and 1.2g of propylene carbonate were added and stirred for 10 minutes. 58g of silicon-zirconium hybrid sol was added and stirred for 15 minutes at 30°C. Then, 2.7g of BYK333, 2.2g of BYK-066N, 28g of polyethylene micronized wax, and 12g of PTFE micronized powder were added and stirred for 10 minutes. The stirring speed was reduced to 300 rpm, and 6.6g of double-walled microcapsule powder was added and stirred for 5 minutes. Finally, 96.36g of aluminum silver paste mixture was added, stirred evenly, and filtered to obtain a coating for motorcycle wheel hubs resistant to machine tool scratches from aluminum shavings.

[0054] Example 7 130g KH560, 60g methyltrimethoxysilane, and 215g n-butanol were mixed and stirred at 28°C for 10 min to obtain a mixture. 20g deionized water, 0.8g glacial acetic acid, and 80g n-butanol were mixed to prepare a hydrolysate, which was then added dropwise to the mixture at 30°C over a period of 30 min. After the addition was complete, stirring was continued for 60 min to obtain a silica sol precursor. Separately, 55g n-zirconium propoxide and 35g acetylacetone were added to 160g n-butanol and stirred at 30°C for 30 min to obtain a zirconium complex solution. This solution was slowly added dropwise to the silica sol precursor, and stirring was continued for 120 min. The mixture was then aged at room temperature for 24 h and filtered to obtain a silicon-zirconium hybrid sol.

[0055] 105g of bisphenol A type epoxy resin (epoxy equivalent of 450-550g / eq) and 65g of butyl acetate were added to a reaction vessel, heated to 110℃ and stirred to dissolve. 20g of adipic acid and 0.15g of zinc acetylacetonate were added, the temperature was raised to 130℃, and the reaction was carried out for 120min. The mixture was then filtered to obtain an epoxy-modified prepolymer solution.

[0056] Add 66g of aluminum silver paste, 30g of butyl acetate and 0.36g of sodium polyacrylate to the reaction vessel and stir until homogeneous to obtain the aluminum silver paste mixture. Add 525g of hydroxyl acrylic resin solution to a reaction vessel and stir at 800rpm. Add 85.8g of butyl acetate and 55g of sec-butyl acetate and stir for 8min. Then add 140g of hexamethoxymethyl melamine, 45g of epoxy modified prepolymer solution, 18g of BYK4510, 12g of organobentonite and 1.2g of propylene carbonate and stir for 10min. Add 58g of silicon-zirconium hybrid sol and continue stirring at 30℃ for 15min. Then add 2.7g of BYK333, 2.2g of BYK-066N, 28g of polyethylene micron wax and 12g of PTFE micron powder and stir for 10min. Reduce the speed to 300rpm and add 96.36g of aluminum silver paste mixture. Stir evenly and filter to obtain a coating for anti-machine tooling aluminum shavings scratches on motorcycle wheel hubs.

[0057] The present invention also includes comparative examples and related experiments.

[0058] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that acetylacetone is not added when preparing the silicon-zirconium hybrid sol. The other components and preparation process are the same as in Example 1, and a coating for motorcycle wheel hubs resistant to machine tool aluminum chip scratches is prepared.

[0059] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the epoxy modified prepolymer solution is not prepared. Instead, bisphenol A type epoxy resin is dissolved in butyl acetate and filtered to replace it. The other components and preparation process are the same as in Example 1. A coating for motorcycle wheel hubs that resists scratches from lathe machining and aluminum chips is prepared.

[0060] Performance testing Performance tests were conducted on the anti-machine tooling aluminum chip scratch coatings for motorcycle wheel hubs prepared in Examples 1-7 and Comparative Examples 1-2. The test plates were made of aluminum alloy substrates and were sprayed after conventional degreasing and grinding pretreatment. The dry film thickness was controlled at (30±5) μm, and the baking curing conditions were (140±5)℃×(20±5)min. Adhesion was tested according to GB / T 5210-2006 "Paints and Varnishes - Pull-off Adhesion Test"; abrasion resistance was tested according to GB / T 1768-2006 "Determination of Abrasion Resistance of Paints and Varnishes - Rotating Rubber Grinding Wheel Method", expressed as mass loss; scratch resistance was tested according to GB / T 9279-2015 "Determination of Scratch Resistance of Paints and Varnishes", expressed as critical load; abrasion resistance was tested according to GB / T 31591-2015 "Determination of Abrasion Resistance of Paints and Varnishes", expressed as color difference change ΔE; the lighting conditions for visual evaluation of appearance were performed according to GB / T 37356-2019 "Lighting Conditions and Methods for Visual Evaluation of Paint and Varnish Coatings", and a 5-point rating system was used (5 being the best, 1 being the worst). The appearance rating comprehensively considered pinholes, craters, particles, flow defects, etc., and the average of the 5 evaluations was taken. The test results are shown in Table 1.

[0061] Table 1

[0062] As can be seen from Table 1 above, compared with Example 1, the scratch critical load of the anti-machine tooling aluminum chip scratch coating for motorcycle wheel hubs prepared in Comparative Example 1 decreased significantly, and the scratch resistance ΔE increased significantly. This indicates that without zirconium complexation, the zirconium source will rapidly hydrolyze and condense, and the number of agglomerated "hard spots" will increase. This makes it easier for local stress concentration and microcracks to start in the coating, resulting in deeper furrows when scratched / scratched. The pull-off adhesion and appearance grade of the anti-machine tooling aluminum chip scratch coating for motorcycle wheel hubs prepared in Comparative Example 2 decreased significantly. This indicates that the lack of introduction of flexible ester segments makes the crosslinking network more brittle and the internal stress higher. As a result, the stress cannot be dissipated when scratched by aluminum chips, and cracks are more likely to penetrate and extend along the interface, which in turn manifests as decreased adhesion and more severe whitening / peeling.

[0063] The difference between Example 7 and Example 6 is that double-walled microcapsule powder was not used. Compared with Example 6, the critical load of the anti-machine tool aluminum chip scratch coating for motorcycle wheel hub prepared by Example 7 decreased and the wear loss increased. Without microcapsules, the boundary lubrication of "releasing 1-ethyl-3-methylimidazolium diethyl phosphate at stress concentration points" was lacking, resulting in a higher coefficient of friction, deeper plowing, and thus more prone to scratches and decreased wear resistance.

[0064] The above are preferred embodiments of the present invention. Those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A preparation process for a coating for motorcycle wheel hubs resistant to scratches from lathe machining and aluminum shavings, characterized in that, Includes the following steps: Step S1: Add zirconium propoxide and acetylacetone to n-butanol to obtain a zirconium complex solution, slowly add it dropwise into the silica sol precursor, stir, age, filter, and obtain a silicon-zirconium hybrid sol. Step S2: Add bisphenol A type epoxy resin and butyl acetate to the reaction vessel, heat and stir to dissolve, add adipic acid and zinc acetylacetonate to react, filter to obtain epoxy modified prepolymer solution. Step S3: Add the hydroxyl acrylic resin solution to the reaction vessel and stir. Add butyl acetate and sec-butyl acetate and stir. Add hexamethoxymethyl melamine, epoxy modified prepolymer solution, BYK4510, organobentonite and propylene carbonate and stir. Add silicon zirconium hybrid sol and stir. Then add BYK333, BYK-066N, polyethylene micro powder wax and PTFE micro powder and stir at a reduced speed. Finally, add aluminum silver paste mixture and mix well. Filter to obtain a coating for anti-machine tooling aluminum shavings scratches on motorcycle wheel hubs.

2. The preparation process of a coating for motorcycle wheel hubs resistant to scratches from lathe machining and aluminum shavings according to claim 1, characterized in that, The aging time is 12-24 hours.

3. The preparation process of a coating for motorcycle wheel hubs resistant to scratches from lathe machining and aluminum shavings according to claim 1, characterized in that, The preparation of the silica sol precursor includes the following steps: KH560, methyltrimethoxysilane and n-butanol were mixed and stirred to obtain a mixture; deionized water, glacial acetic acid and n-butanol were mixed to prepare a hydrolysate, which was added dropwise to the mixture. After the addition was complete, stirring was continued to obtain the silica sol precursor.

4. The preparation process of a coating for motorcycle wheel hubs resistant to scratches from lathe machining and aluminum shavings according to claim 1, characterized in that, In step S2, the epoxy equivalent of the bisphenol A type epoxy resin is 450-550 g / eq; the temperature for heating and stirring is 110-120℃; the reaction temperature is 130-140℃, and the reaction time is 120-180 min.

5. The preparation process of a coating for motorcycle wheel hubs resistant to scratches from lathe machining and aluminum shavings according to claim 1, characterized in that, The preparation of the aluminum silver paste mixture includes the following steps: Aluminum silver paste, butyl acetate, and sodium polyacrylate are added to a reaction vessel and stirred evenly to obtain an aluminum silver paste mixture. The aluminum silver paste mixture comprises the following components in parts by weight: 55-66 parts aluminum silver paste, 25-30 parts butyl acetate, and 0.3-0.36 parts sodium polyacrylate.

6. The preparation process of a coating for motorcycle wheel hubs resistant to scratches from lathe machining and aluminum shavings according to claim 1, characterized in that, The hydroxy acrylic resin solution has a solid content of 59-61 wt%, a Tg of 55-65℃, and an average molecular weight of 8000-12000.

7. The preparation process of a coating for motorcycle wheel hubs resistant to scratches from lathe machining and aluminum shavings according to claim 1, characterized in that, In step S3, double-walled microcapsule powder was added and stirred before adding the aluminum silver paste mixture; the preparation of the double-walled microcapsule powder includes the following steps: Polysulfone was added to NMP and stirred until clear. 1-Ethyl-3-methylimidazolium diethyl phosphate was added and stirring continued to obtain the inner phase. PVA aqueous solution was placed in an emulsification vessel, and the inner phase was added dropwise under high shear conditions to obtain an emulsion. The rotation speed was adjusted, and deionized water was slowly added. The mixture was stirred, centrifuged, washed, and transferred to an ethanol solution. Ammonia water was then added, and the mixture was stirred evenly. TEOS was added dropwise to carry out the reaction. The mixture was filtered, washed, and dried to obtain double-walled microcapsule powder.

8. The preparation process of a coating for motorcycle wheel hubs resistant to scratches from lathe machining and aluminum shavings according to claim 7, characterized in that, The high shear conditions are achieved at a rotation speed of 8000-10000 rpm; after adjustment, the rotation speed is 400-600 rpm; the concentration of ammonia is 25-28 wt%, the concentration of PVA aqueous solution is 1-1.5 wt%, and the concentration of ethanol solution is 75-85 wt%.

9. The preparation process of a coating for motorcycle wheel hubs resistant to scratches from lathe machining and aluminum shavings according to claim 7, characterized in that, The double-walled microcapsule powder comprises the following components in parts by weight: 10-12 parts polysulfone, 88-90 parts NMP and 18-25 parts 1-ethyl-3-methylimidazolium diethyl phosphate; and also comprises the following components in parts by volume: 500 parts PVA aqueous solution, 300-400 parts deionized water, 400 parts ethanol solution, 1-1.5 parts ammonia and 6-10 parts TEOS.

10. A scratch-resistant coating for motorcycle wheel hubs made from aluminum shavings from lathe machining, prepared using the preparation process described in any one of claims 1-9, characterized in that... The components include the following parts by weight: The mixture comprises 289-359 parts of hydroxyl acrylic resin, 130-156 parts of hexamethoxymethyl melamine, 45-54 parts of epoxy modified prepolymer solution, 71.5-85.8 parts of butyl acetate, 50-60 parts of sec-butyl acetate, 55-66 parts of silicon-zirconium hybrid sol, 18-21.6 parts of BYK4510, 12-14.4 parts of organobentonite, 1.2-1.44 parts of propylene carbonate, 2.5-3 parts of BYK333, 2-2.4 parts of BYK-066N, 25-30 parts of polyethylene micronized wax, 10-12 parts of PTFE micronized powder, and 80.3-96.36 parts of aluminum silver paste mixture.

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