Normal-temperature self-drying repair coating, preparation method and construction method

Abstract

The invention discloses a normal-temperature self-drying repair coating for a foaming type PVC stone chip resistant coating, a preparation method and a construction method, and belongs to the technical field of surface protection of automobile parts. Hydrocarbon resin and a thermoplastic elastomer are weighed and added into a first part of diluent, and a resin solution is prepared; sequentially adding the nano calcium carbonate, the pigment, the filler, the antioxidant and the moisture absorbent into the resin solution, and stirring and dispersing after adding to obtain a uniform first mixed system; adding the polymer particles and the residual diluent into the first mixed system, and continuously stirring and dispersing to uniformly disperse the polymer particles to obtain a second mixed system; carrying out vacuum degassing on the second mixed system to obtain the bubble-free and uniformly-dispersed normal-temperature self-drying repair coating. After repairing construction, the coating and an original coating are small in color difference and similar in appearance, the adhesive force and stone impact resistance of the repairing coating are excellent, and the problems that in the prior art, repairing cost is high, efficiency is low, heating curing is needed, and coating decoration is insufficient are solved.

Description

Technical Field

[0001] This invention belongs to the field of automotive parts surface protection technology, and relates to a repair material for foamed PVC coating on the surface of the bottom guard plate of new energy vehicle battery pack. Specifically, it relates to a room temperature self-drying repair coating for foamed PVC anti-stone chip coating, its preparation method and construction method. Background Technology

[0002] With the advancement of global energy transition and environmental protection policies, the new energy vehicle industry has become a core component of the country's strategic emerging industries. In the new energy vehicle manufacturing industry chain, the battery pack, as the core power source, directly affects the performance of the entire vehicle and user safety in terms of its safety and lifespan.

[0003] In the field of new energy vehicle manufacturing, the battery pack underbody protection plate, as a key protective component for the vehicle's power battery and chassis, is constantly exposed to complex conditions such as gravel impact, rainwater erosion, road friction, and alternating high and low temperatures. The performance of its surface protective coating directly affects the safety and lifespan of the entire vehicle. Currently, the industry commonly uses PVC anti-stone impact coating to spray-coat the battery pack underbody protection plate. This coating, with its excellent impact resistance, flexibility, corrosion resistance, and weather resistance, can effectively absorb the energy generated by gravel impacts, preventing damage and corrosion of the battery pack underbody protection plate, thus providing good protection for the battery pack.

[0004] Compared to conventional non-foamed PVC anti-stone impact coatings, foamed PVC anti-stone impact coatings possess unique foaming properties. To achieve the same dry film thickness, only a lower wet film thickness needs to be applied, saving paint and reducing the weight of the final product. This makes it a lightweight new material, currently holding over 90% market share in battery pack bottom protection plate coatings. PVC anti-stone impact coatings are high-solids thick-film coatings, typically formed by high-pressure airless spraying followed by baking and curing. Baking temperatures are generally 140-170℃, and baking times are generally 25-50 minutes. Because the foaming agent added to foamed PVC anti-stone impact coatings is a microsphere capsule containing low-boiling-point hydrocarbons, the microsphere foaming agent expands up to 10 times during baking, resulting in a unique, granular yet highly uniform decorative coating surface, such as... Figure 2 The surface state image of the foamed PVC anti-stone impact coating, magnified 20 times under an optical microscope, shows that the coating combines decoration and protection and has excellent anti-stone impact performance. However, the existing technology for coating repair mainly focuses on the repair of smooth coating surfaces, which is extremely difficult to repair on this kind of surface with a grainy texture.

[0005] As car consumers increasingly demand aesthetically pleasing exterior finishes for automotive components, OEMs have mandated that the coating on battery pack underbody panels must be uniform, free from localized peeling, scratches, and significant color variations to ensure consistent appearance across mass-produced products. Any coating damage caused during transport or assembly must be repaired; otherwise, the product is considered defective. However, in actual production processes, inadequate protective measures during process transitions, handling, and warehousing make it difficult to effectively mitigate the risk of damage during battery pack underbody panels. Due to their large size, the underbody panels are stacked on racks, and friction during stacking and accidental collisions during handling easily lead to coating defects such as peeling scratches and edge chipping, with a defect incidence rate of 8%-12%.

[0006] Traditional PVC repair coatings, whether oven-dried or room-temperature curing, cannot achieve the distinct and evenly distributed decorative coating surface characteristic of foamed PVC stone-impact resistant coatings, regardless of the application method (spraying, extrusion, scraping, or brushing). To address these shortcomings, and because traditional PVC repair coatings cannot meet the requirements, the industry currently employs a "sanding and re-spraying of the entire battery pack bottom protector" repair solution. The specific process involves: removing the defective bottom protector from the assembly line, sanding the entire surface to remove the original coating, re-spraying with PVC stone-impact resistant coating, and then placing it in a baking oven for curing. While this solution can ensure the consistency of the appearance after repair, it has significant drawbacks: First, the entire process of sanding, repainting, and baking takes 4-6 hours, which seriously disrupts the production rhythm, especially in the case of on-the-spot repair next to the OEM assembly line, and cannot meet the efficiency requirements of "repair and install immediately"; Second, full sanding may damage the original structure of the underbody protection plate substrate, and repainting requires a large amount of paint and heat energy, resulting in an increase of more than 40% in the cost of repairing a single part, which is not in line with the development trend of energy conservation, emission reduction and lean production in the automotive manufacturing industry.

[0007] Therefore, there is an urgent need to develop a room-temperature self-drying repair coating that is suitable for on-site conditions, balances quality and efficiency, and can be used for foamed PVC anti-stone chip coatings. Summary of the Invention

[0008] The purpose of this invention is to solve the problems of high cost, low efficiency, need for heat curing, and insufficient decorative properties in repairing the bottom protective plate coating of foamed PVC anti-stone impact coating. This invention provides a room-temperature self-drying repair coating for foamed PVC anti-stone impact coatings, its preparation method, and its application method. This repair material can self-dry at room temperature, is easy to apply, and produces a small difference in appearance from the original coating after repair, while also possessing excellent adhesion and anti-stone impact properties. This invention also provides a preparation method for this repair coating, which is simple, easy to operate, and suitable for batch production. Furthermore, this invention provides an application process for this repair coating that is convenient, efficient, and adaptable to the pace of rapid on-site repairs, effectively solving the repair problems of foamed PVC coatings on battery pack bottom protective plates.

[0009] The objective of this invention can be achieved through the following technical solutions: In a first aspect, the present invention provides a room-temperature self-drying repair coating for foamed PVC stone chip resistant coatings, the room-temperature self-drying repair coating comprising the following components by weight: (1) Hydrocarbon resin 20%~25% (2) 10%~25% thermoplastic elastomer (3) Nano calcium carbonate 10%~15% (4) Pigment 0.1%~1% (5) Filler 10%~15% (6) Antioxidant 0.2%~3% (7) Desiccant 1%~3% (8) Diluent 20%~25% (9) Polymer particles 10%~15% The hydrocarbon resin is any one or a combination of C5 aliphatic hydrocarbon resin, C9 aromatic hydrocarbon resin, and C5 aliphatic / C9 aromatic copolymer hydrocarbon resin; the thermoplastic elastomer is a thermoplastic elastomer grafted with maleic anhydride.

[0010] Furthermore, the softening point of the C5 aliphatic hydrocarbon resin is 70-115℃, the softening point of the C9 aromatic hydrocarbon resin is 80-150℃, and the softening point of the C5 aliphatic / C9 aromatic copolymer hydrocarbon resin is 85-120℃.

[0011] Furthermore, the thermoplastic elastomer is obtained by grafting maleic anhydride onto any one of SEBS, SBS, SIS, or SEPS / SEP, with a grafting rate of 1.1-2.0%.

[0012] The thermoplastic elastomers mentioned above correspond to the following products: SEBS-G-MAH: styrene-ethylene-butene-styrene block copolymer grafted with maleic anhydride; SBS-G-MAH: styrene-butadiene-styrene block copolymer grafted with maleic anhydride; SIS-G-MAH: styrene-isoprene-styrene block copolymer grafted with maleic anhydride; and SEPS / SEP-G-MAH: styrene-ethylene-propylene-styrene block copolymer (hydrogenated SIS) grafted product. Furthermore, the nano-calcium carbonate has an average particle size of 50-100 μm and a specific surface area of ​​15-25 m². 2 / g.

[0013] Furthermore, the pigment may be one or more of the following: medium pigment carbon black (particle size 18-25 nm, blackness 23-30), titanium dioxide (0.2-0.3 μm).

[0014] Furthermore, the filler may be one or more of the following: heavy calcium carbonate, light calcium carbonate.

[0015] Furthermore, the antioxidant may be one or more of the following: antioxidant 1010, antioxidant 1076, and antioxidant 168.

[0016] Furthermore, the hygroscopic agent may be one or more of the following: molecular sieve, calcium oxide, anhydrous calcium chloride.

[0017] Furthermore, the diluent is xylene.

[0018] Furthermore, the polymer particles can be one or more of the following: PVC particles, rubber particles, with an average particle size of 150-300 μm.

[0019] Secondly, the present invention provides a method for preparing a room-temperature self-drying repair coating for foamed PVC anti-stone chip coating, comprising the following steps: Step 1, dissolving resin: Weigh the hydrocarbon resin and thermoplastic elastomer by weight percentage and add them to the first part of the diluent to prepare a resin solution; Step 2, Mixing and Dispersing: Add nano-calcium carbonate, pigment, filler, antioxidant, and hygroscopic agent to the resin solution in sequence according to their weight percentages. After the addition is completed, stir and disperse to obtain a uniform first mixed system. Step 3: Add remaining raw materials: Add polymer particles and remaining diluent to the first mixture, continue stirring and dispersing to make the polymer particles evenly dispersed, and obtain the second mixture. Step 4: Vacuum degas the second mixing system to obtain a bubble-free, uniformly dispersed room-temperature self-drying repair coating.

[0020] Furthermore, in step 1, the first portion of the diluent accounts for 60%-70% of the total weight of the added diluent.

[0021] Furthermore, in step 1, the process of preparing the resin solution is as follows: After adding the hydrocarbon resin and thermoplastic elastomer to the first part of the diluent, soak it at room temperature (15-35℃) for 2-4 hours, stirring once every 30 minutes during this period, at a stirring speed of 200-300 r / min for 2-10 minutes, until the hydrocarbon resin and thermoplastic elastomer are completely dissolved to form a uniform resin solution.

[0022] Furthermore, in step 2, after the addition is completed, the dispersion is carried out by stirring at a speed of 1000-1200 r / min for 10-15 minutes to ensure that the components are evenly dispersed and to avoid agglomeration.

[0023] Furthermore, in step 3, the stirring and dispersion is continued by stirring at a speed of 1000-1200 r / min for 5-20 min to ensure that the polymer particles are uniformly dispersed in the mixture.

[0024] Further, in step 4, the specific method of vacuum degassing is as follows: the second mixing system is transferred to a vacuum degassing machine and degassed for 10-30 minutes under a vacuum of -0.095 ~ -0.098 MPa to remove bubbles generated by stirring in the mixture, thereby obtaining a bubble-free, uniformly dispersed room temperature self-drying repair coating.

[0025] It should be noted that after vacuum degassing in step 4 to obtain room temperature self-drying repair paint, it should be placed in a sealed container and stored in a cool, dry place (temperature 15-35℃, relative humidity ≤60%). The shelf life is 6 months.

[0026] The advantages of the preparation method of the present invention are as follows: the resin is dissolved by soaking at room temperature, which does not require heating, has low energy consumption and is safe to operate; the components are added in steps and the stirring speed and time are controlled to ensure that each component is evenly dispersed and to avoid performance fluctuations caused by uneven mixing; the vacuum degassing step effectively removes air bubbles and ensures the appearance quality of the repair material; the overall process is simple, does not require complex equipment, and is suitable for mass production.

[0027] Thirdly, the present invention provides a method for applying a room-temperature self-drying repair coating for a foamed PVC anti-stone chip coating, comprising the following steps: S100. Repairing Defective Areas: Based on the type of defect in the foamed PVC anti-stone chip coating on the workpiece to be repaired, use sandpaper of appropriate grit to grind the original coating in the defective area and adjacent area to remove loose coating, dust and oil stains at the defective area. After grinding, clean the ground area with a thinner. S200, Color matching: Take a portion of the room temperature self-drying repair paint and apply it to the test panel. After it dries at room temperature, compare the color with the original coating. If the color difference exceeds the standard, add color matching pigment to fine-tune the color of the room temperature self-drying repair paint to be coated. S300 Repair Application: Apply the room temperature self-drying repair paint (which does not require color matching or has undergone minor color adjustments) evenly to the defective area, making the thickness slightly higher than the original coating surface, and then smooth it out. S400, room temperature air-drying curing: After the coating is applied, place the workpiece to be repaired in a room temperature environment to air dry naturally.

[0028] In step S100, the defect types include peeling, scratches, and dents. Depending on the type of defect, different grit sandpaper is selected for polishing. The grit selection range is 400-600. For scratches and defects, a larger grit, such as 600 grit, is selected for fine polishing. For peeling defects, a smaller grit is selected for quick polishing.

[0029] The adjacent area is generally selected within 5-10mm around the defect. Lightly sand the defect and the surrounding 5-10mm area of ​​the original coating to remove loose coating, dust, and oil. During sanding, maintain the sandpaper at a 30-45° angle to the base plate surface to avoid over-sanding and damaging the original coating. After sanding, wipe the defect area with a clean cotton cloth dampened with thinner to remove sanding dust and ensure the defect area is clean and dry.

[0030] In step S200, take 3-5g of repair coating and apply it to the test panel. After drying at room temperature for 30 minutes, compare the color with the original coating (when using a colorimeter, ΔE < 1.0 is required). If the color difference exceeds the standard, finely adjust the repair coating according to the color adjustment formula. For example, for every 0.5 deviation in color difference, increase or decrease the amount of carbon black by 0.05% (decrease if the color is dark, increase if the color is light), and adjust the amount of titanium dioxide by 0.05% in the opposite direction. After stirring evenly, compare again until the color difference meets the standard.

[0031] It should be noted that, under normal circumstances, the color of the room temperature self-drying repair coating prepared according to the above formula is the same as that of the original foamed PVC anti-stone chip coating. However, due to the baking process control issues or usage issues of the foamed PVC anti-stone chip coating, there may be color differences. Therefore, it is necessary to add pigments to adjust the color. So, color adjustment is not a necessary step, but a step that is determined based on whether there is a color difference.

[0032] In step S300, the specific steps are as follows: Take an appropriate amount of the adjusted repair paint with a stainless steel scraper and apply the repair paint evenly to the defect area. The thickness of the paint should be slightly higher than the original coating surface by 0.1-0.2mm (leaving room for smoothing). Then, use the scraper to gently smooth the paint along the length of the defect area at a 45-60° angle. During the smoothing process, keep the scraper moving at a uniform speed to ensure that the surface of the repair area is flat and without obvious scraper marks. For deeper defects (depth > 1mm), two-stage scraping can be used. The first stage scrapes to about two-thirds of the depth of the defect. After the surface dries (about 30 minutes), the second stage scrapes and smooths the paint to avoid uneven drying or cracks caused by applying too thick a layer at once.

[0033] In step S400, the workpiece to be repaired is placed in a room temperature environment to air dry naturally without heating. It will be surface dry within 30 minutes (the surface will not be sticky to the touch) and cured within 2 hours (the coating hardness will reach >60HA). During the drying process, avoid collisions, friction or dust contamination to the repaired area.

[0034] It should be noted that in step S400, after the repair coating has dried and cured naturally, the appearance of the repair coating is observed to confirm that there are no defects such as bubbles or cracks, the surface is flat and uniform, and the color is consistent with the original coating; then the repaired workpiece is packaged and assembled according to the normal process.

[0035] The advantages of the above-mentioned construction process of this invention are: simple steps, no need for professional equipment, and on-site operators can master it after simple training; room temperature self-curing, no need for heating equipment, adaptable to customer sites; fast drying speed, only 2 hours from application to curing, greatly improving repair efficiency. It can be used for repairing coating damage during the turnover and storage of battery pack bottom protection plates, and can also be used for on-site repair next to the assembly line of the OEM, meeting the efficiency requirements of repair and installation immediately.

[0036] The repair coating and construction process for foamed PVC anti-stone impact coating provided by this invention can quickly repair damaged coatings, achieve room temperature self-drying (30 minutes surface dry, 2 hours curing), and the repaired coating has small color difference and similar appearance. The repaired coating has excellent adhesion and anti-stone impact performance, solving the problem of repairing the battery pack bottom plate coating of foamed PVC anti-stone impact coating.

[0037] The principle behind the formulation selection of the room-temperature self-drying repair coating of this invention is as follows: This invention uses hydrocarbon resin and thermoplastic elastomer as the base resin, combined with nano-calcium carbonate and polymer particles for modification, and adds appropriate amounts of antioxidants, hygroscopic agents, pigments, fillers and diluents. The mixture is compounded in a specific ratio and prepared as a room-temperature self-drying repair coating for foamed PVC anti-stone impact coating through steps such as resin dissolution, mixing and dispersion and degassing. When using this coating to repair damaged foamed PVC anti-stone impact coatings, it is applied by hand and cured at room temperature.

[0038] The hydrocarbon resin selected in this invention has an average molecular weight of 1000~2500, a softening point of 70~150℃, strong chemical cohesion, high hardness, high strength, and fast drying speed; good fluidity, which can improve the wettability of the main material; outstanding initial tack and good tackification properties; good heat resistance, cold resistance, water resistance, acid and alkali resistance, and light stability; and good compatibility with SBS, SIS, SEBS, SEPS, natural rubber, synthetic rubber, and EVA, etc., and is inexpensive.

[0039] The thermoplastic elastomer selected in this invention is SEBS-G-MAH, obtained by grafting maleic anhydride (MAH) onto styrene-ethylene-butadiene-styrene copolymer (SEBS), possessing both the polar MAH group and the flexible, highly elastic SEBS segments. SEBS-G-MAH exhibits good adhesion, bonding well with both polar and non-polar materials; it also demonstrates good compatibility, improving the dispersibility of its components and enhancing the overall performance of both polar and non-polar materials; and it exhibits excellent temperature resistance, with an embrittlement temperature ≤ -60℃. SEBS-G-MAH is a polar thermoplastic elastomer with excellent compatibility, low-temperature flexibility, and superior mechanical properties even under high filler conditions. It can serve as a template for IPN (Interpenetrating Polymer Networks) when blended with hydrocarbon resins to form an IPN structure, resulting in a repair coating with excellent adhesion and stone chip resistance.

[0040] The nano-calcium carbonate selected in this invention is made from nano-sized calcium carbonate particles as the main raw material through special surface treatment and manufacturing process. It is a toughening filler. At the same time, it has a large specific surface area, which can adjust the thixotropy of repair coatings, improve storage stability, and improve construction performance.

[0041] The antioxidants selected in this invention can inhibit the thermo-oxidative degradation of polymers, extend the service life of the coating, and improve the flame retardant properties of the coating.

[0042] The desiccant selected in this invention can effectively absorb moisture in the air, avoiding poor appearance during construction in humid environments.

[0043] The polymer particles selected in this invention have good compatibility with the above-mentioned matrix resin and have an average particle size of 150-300 μm, so that after the repair coating is cured, it can form a unique decorative coating surface with a granular texture but very uniform, like a foamed PVC anti-stone chip coating.

[0044] The room-temperature self-drying repair coating prepared by this invention is used to repair foamed PVC anti-stone impact coatings. It can be applied by hand and cured at room temperature. The repaired coating has small color difference and similar appearance. The repaired coating has excellent adhesion and anti-stone impact performance. It solves the problems of high cost, low efficiency, need for heat curing, and insufficient decorative properties of foamed PVC anti-stone impact coatings.

[0045] Compared with the prior art, the present invention has the following beneficial effects: The foamed PVC anti-stone impact coating of this invention, along with its room-temperature self-drying repair coating, preparation method, and construction process, offers significant advantages over existing technologies. Firstly, it adapts to the on-site environment, employing room-temperature self-drying curing without the need for heating equipment, thus solving the compatibility problem of existing repair coatings requiring heating for curing. Secondly, it dries quickly, achieving surface drying in 30 minutes and curing in 2 hours (coating hardness >60HA), allowing for direct packaging and assembly after repair, increasing efficiency by 3-5 times and aligning with rapid production schedules. Thirdly, it exhibits minimal color difference and excellent appearance, highly matching the color and texture of the original coating, with a color difference ΔE <1.0, meeting stringent appearance requirements. Fourthly, it boasts superior performance, achieving coating adhesion grade 0, stone impact resistance (M6 nut impact load) >30Kg, and hardness >60HA. Fifthly, preparation and construction are convenient, requiring no complex equipment, operating at room temperature, and requiring only simple training for personnel, reducing operational difficulty and labor costs. Sixthly, costs are controllable; localized repairs save over 95% of coating compared to traditional full-area re-spraying, resulting in a 90% reduction in overall cost and high promotional value. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0047] Figure 1 : This is a flowchart illustrating the preparation process of the room-temperature self-drying repair coating for foamed PVC anti-stone chip coatings according to the present invention.

[0048] Figure 2 : The surface morphology of the foamed PVC coating that is the object to be repaired in this invention is magnified 20 times using an optical microscope.

[0049] Figure 3 : These are the appearance diagrams of Embodiment 2 and the comparative example after repair. Figure 3 Image a shows the appearance after repair using room temperature self-drying repair paint in Example 2. Figure 3 Figure b shows the appearance after repair in the comparative example.

[0050] Figure 4These are comparison images of the surface morphology before and after repair using an optical microscope, magnified 5 times, for Embodiment 2 and the comparative example of the present invention. Figure 4 Image a shows the surface morphology of the foamed PVC coating with pitting defects before repair. Figure 4 Image b in Example 2 shows the surface morphology after repair using a room-temperature self-drying repair coating. Figure 4 In the middle c, the surface morphology after repair is shown in the comparative example. Detailed Implementation

[0051] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0052] like Figure 1 As shown, this invention provides a method for preparing a room-temperature self-drying repair coating for foamed PVC anti-stone chip coating, comprising the following steps: Step 1, dissolving resin: Weigh the hydrocarbon resin and thermoplastic elastomer by weight percentage and add them to the first part of the diluent to prepare a resin solution; Step 2, Mixing and Dispersing: Add nano-calcium carbonate, pigment, filler, antioxidant, and hygroscopic agent to the resin solution in sequence according to their weight percentages. After the addition is completed, stir and disperse to obtain a uniform first mixed system. Step 3: Add remaining raw materials: Add polymer particles and remaining diluent to the first mixture, continue stirring and dispersing to make the polymer particles evenly dispersed, and obtain the second mixture. Step 4: Vacuum degas the second mixing system to obtain a bubble-free, uniformly dispersed room-temperature self-drying repair coating.

[0053] Example 1 1. Composition of repair coating (by weight percentage) (1) Hydrocarbon resin (YL-90, softening point 100±5℃) 22% (2) Thermoplastic elastomer (SEBS FG1901, grafting rate 1.5%) 18% (3) Nano calcium carbonate (KLNM-CO2, average particle size 60 μm, specific surface area 25 m²) 2 / g) 12% (4) Pigment (medium-pigment carbon black, particle size 18-25 nm, blackness 23-25) 0.5% (5) Filler (heavy calcium carbonate) 12% (6) Antioxidant (1010) 1.5% (7) 2% desiccant (calcium oxide) (8) Diluent (xylene) 22% (9) Polymer particles (PVC particles, average particle size 250 μm) 10% 2. Preparation method Step 1: Weigh 2.2 kg of hydrocarbon resin YL-90 and 1.8 kg of thermoplastic elastomer SEBS FG1901, add them to 1.54 kg of xylene (accounting for 70% of the total xylene weight), soak at room temperature (25℃) for 3 hours, stirring at a speed of 250 r / min every 30 minutes (about 5 min) until completely dissolved to form a resin solution; Step 2: Add 1.2 kg of nano calcium carbonate, 0.05 kg of medium-pigment carbon black, 1.2 kg of heavy calcium carbonate, 0.15 kg of antioxidant 1010, and 0.2 kg of calcium oxide to the resin solution in sequence. After adding, stir at 1200 r / min for 15 min to ensure uniform dispersion. Step 3: Continue to add 1 kg of PVC granules and 0.66 kg of xylene (the remaining 30% of xylene), and stir at 1200 r / min for 15 minutes; Step 4: Transfer the mixture to a vacuum degasser and degas for 20 minutes at a vacuum of -0.096 MPa to remove air bubbles and obtain the repair coating.

[0054] Store the repair paint in a sealed container in a cool, dry place (temperature 15-35℃, relative humidity ≤60%) for later use.

[0055] 3. How to use S100: For a scratch defect on the bottom guard plate that is 25mm long, 6mm wide and 0.7mm deep, use 500-grit sandpaper to sand the defect and the surrounding 8mm area, and clean it with a cotton cloth soaked in xylene. S200: Compare a small amount of repair material with the original coating. The color difference ΔE = 0.7, no adjustment is needed. S300: Use a scraper to apply repair material to the defect, about 0.9mm thick, and smooth it along the length. S400: Air dry at 25℃ and 50% relative humidity, surface dry in 28 minutes, and cured in 1.8 hours.

[0056] After curing, the appearance is smooth and without defects. The adhesion test is grade 0. The stone impact resistance test of the M6 ​​nut is 32Kg and the hardness is 62HA. After meeting the standards, it is packaged.

[0057] Example 2 1. Repair material components (by weight percentage) (1) Hydrocarbon resin (SU-120, softening point 120±5℃) 20% (2) Thermoplastic elastomer (SEBS FG1901, grafting rate 1.5%) 20% (3) Nano calcium carbonate (P150, average particle size 90 micrometers, specific surface area 15m²) 2 / g) 11% (4) Pigment (medium-pigment carbon black, particle size 19-20nm, blackness 25-28) 0.9% (5) Filler (light calcium carbonate) 10% (6) Antioxidant (168) 0.2% (7) Desiccant (anhydrous calcium chloride) 1.5% (8) Diluent (xylene) 22% (9) Polymer particles (rubber particles, average particle size 180 μm) 14.4% 2. Preparation method Step 1: Weigh 2 kg of hydrocarbon resin SU-120 and 2 kg of thermoplastic elastomer SEBS FG1901, add them to 1.54 kg of xylene (accounting for 70% of the total xylene weight), soak at room temperature (22℃) for 4 hours, stirring at 300 r / min every 30 minutes (about 8 min) until completely dissolved to form a resin solution; Step 2: Add 1.1 kg nano calcium carbonate, 0.9 kg medium pigment carbon black, 1 kg light calcium carbonate, 0.02 kg antioxidant 168, and 0.15 kg anhydrous calcium chloride to the resin solution in sequence. After adding, stir at 1200 r / min for 12 minutes. Step 3: Continue to add 1.44 kg of rubber granules and 0.66 kg of xylene (the remaining 30% of xylene), and stir at 1200 r / min for 18 minutes; Step 4: Degas at a vacuum of -0.095 MPa for 25 minutes to obtain the repair coating.

[0058] Store the repair paint in a sealed container in a cool, dry place (temperature 15-35℃, relative humidity ≤60%) for later use.

[0059] 3. How to use S100: For a peeling defect with a diameter of 20mm and a depth of about 1.2mm on the bottom guard plate, use 400-grit sandpaper to sand the defect and the surrounding 10mm area, clean and let it dry. S200: Compare the repair material with the original coating; the color difference ΔE = 0.9, no adjustment is needed. S300: Apply in two coats. Apply the first coat to a thickness of about 0.8 mm. After it is surface dry for 30 minutes, apply the second coat to a thickness of 1.3 mm and smooth it out. S400: Air dry at 22℃ and 45% relative humidity, surface dry in 30 minutes, and cured in 2 hours.

[0060] No defects were found in the appearance inspection. The adhesion was rated as 0. The stone impact resistance test load was 35Kg and the hardness was 65HA. After meeting the standards, the product was packaged.

[0061] The coatings repaired using room-temperature self-drying repair coatings in Examples 1 and 2 of the present invention meet the following performance indicators: Drying speed: At room temperature (15-35℃), surface drying time ≤30 minutes, curing time ≤2 hours (coating hardness reaches >60HA); Color difference: The color difference ΔE between the coating and the original PVC anti-stone chip coating is less than 1.0, which meets the customer's appearance color difference requirements; Adhesion: Tested according to GB / T 9286-2021 "Cross-cut test of paint and varnish film", the adhesion level reaches 0 (the cut edge is complete and smooth, with no peeling).

[0062] Stone chip resistance: Impact test was conducted using an M6 nut, with an impact load >30Kg; Hardness: Tested according to GB / T 2411-2008 "Determination of indentation hardness (Shore hardness) of plastics and hard rubber using a hardness tester", Shore A hardness > 60HA; Appearance: The repaired coating is uniform, free from defects such as bubbles, pinholes, cracks, and runs, and the surface texture is completely consistent with that of the original foamed PVC anti-stone chip coating.

[0063] Comparative example: Commercially available paint (purchased from Taobao, Shilidun, quick-drying anti-rust elastic adhesive, self-spraying type), shake well before use, apply by spraying, air dry at room temperature for 24 hours (≥25℃ is optimal). When using this product, the surrounding area should be masked to prevent spray from splashing onto the adjacent coating, causing color difference and unevenness.

[0064] like Figure 3 The figures shown are the appearance diagrams of Embodiment 2 and the comparative example after repair. Figure 3 Image a shows the appearance after repair using room temperature self-drying repair paint in Example 2. The area highlighted by the red rectangle is the repaired area. Figure 3 In the comparison diagram, b shows the appearance after repair. The area outlined by the red rectangle is the repaired area. Figure 3 Comparing the areas selected by the red rectangles in sections a and b, it can be seen that the appearance after repair in Embodiment 2 of the present invention is basically the same as the original foamed PVC coating. Although the color of the repaired coating in the comparative example is similar, the surface of the repaired coating is smooth, resulting in a large visual difference and inferior protective performance compared to the original foamed PVC coating.

[0065] like Figure 4The image shown is a comparison of the surface morphology before and after repair using an optical microscope (magnified 5x) in Embodiment 2 and the comparative example of the present invention. Figure 4 Image a shows the appearance of the foamed PVC coating before repair. Figure 4 Image b shows the appearance after repair using the room-temperature self-drying repair coating in Example 2. Figure 4 Figure c shows the appearance after repair in the comparative example. It can be seen that the repaired area in Example 2 of this invention is basically granular, with a surface particle size similar to the original foamed PVC coating, and also exhibits good stone impact resistance. In contrast, after repair in the comparative example, the repaired area appears smooth, showing a significant difference from the overall appearance of the coating. Furthermore, there is a risk of poor impact resistance due to poor adhesion, which does not meet the appearance requirements of OEMs, reduces consumer trust in the brand, and causes driving anxiety, thus hindering product sales. Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this invention and are not intended to limit it. Although the invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this invention.

Claims

1. A room-temperature self-drying repair coating for foamed PVC anti-stone chip coating, characterized in that, The room temperature self-drying repair coating comprises the following components by weight: Hydrocarbon resin 20%~25% Thermoplastic elastomers 10%~25% Nano-calcium carbonate 10%~15% Pigment 0.1%~1% Filler 10%~15% Antioxidant 0.2%~3% Desiccant 1%~3% Diluent 20%~25% Polymer particles 10%~15% The hydrocarbon resin is any one or a combination of C5 aliphatic hydrocarbon resin, C9 aromatic hydrocarbon resin, and C5 aliphatic / C9 aromatic copolymer hydrocarbon resin; the thermoplastic elastomer is a thermoplastic elastomer grafted with maleic anhydride.

2. The room-temperature self-drying repair coating for foamed PVC anti-stone chip coating according to claim 1, characterized in that, The thermoplastic elastomer is obtained by grafting maleic anhydride onto any one of SEBS, SBS, SIS, or SEPS / SEP, with a grafting rate of 1.1-2.0%.

3. The room-temperature self-drying repair coating for foamed PVC anti-stone chip coating according to claim 1, characterized in that, The nano-calcium carbonate has an average particle size of 50-100 μm and a specific surface area of ​​15-25 m². 2 / g.

4. The room-temperature self-drying repair coating for foamed PVC anti-stone chip coating according to claim 1, characterized in that, The filler is any one or two of heavy calcium carbonate and light calcium carbonate.

5. The room-temperature self-drying repair coating for foamed PVC anti-stone chip coating according to claim 1, characterized in that, The hygroscopic agent may be any one or a combination of several of molecular sieves, calcium oxide, and anhydrous calcium chloride.

6. The room-temperature self-drying repair coating for foamed PVC anti-stone chip coating according to claim 1, characterized in that, The polymer particles are any one or a combination of two of PVC particles and rubber particles, with an average particle size of 150-300 μm.

7. A method for preparing a room-temperature self-drying repair coating for foamed PVC anti-stone chip coating as described in any one of claims 1-6, characterized in that, Includes the following steps: Weigh out the hydrocarbon resin and thermoplastic elastomer by weight percentage and add them to the first part of the diluent to prepare a resin solution; Nano-calcium carbonate, pigment, filler, antioxidant, and hygroscopic agent were added to the resin solution in sequence according to their weight percentages. After the addition was completed, the mixture was stirred and dispersed to obtain a uniform first mixed system. Add polymer particles and the remaining diluent to the first mixture, and continue stirring and dispersing to ensure uniform dispersion of the polymer particles, thus obtaining the second mixture. The second mixing system was degassed under vacuum to obtain a bubble-free, uniformly dispersed, room-temperature self-drying repair coating.

8. The method for preparing the room-temperature self-drying repair coating for foamed PVC anti-stone chip coating according to claim 7, characterized in that, The first part of the diluent accounts for 60%-70% of the total weight of the diluent added.

9. The method for preparing the room-temperature self-drying repair coating for foamed PVC anti-stone chip coating according to claim 7, characterized in that, The stirring speed of the first mixture was 1000-1200 r / min, and the stirring time was 10-15 minutes. The stirring speed of the second mixture was 1000-1200 r / min, and the stirring time was 5-20 minutes.

10. A method for applying the room-temperature self-drying repair coating for foamed PVC anti-stone chip coating as described in any one of claims 1-6, characterized in that, Includes the following steps: Repairing defective areas: Depending on the type of defect in the foamed PVC anti-stone chip coating on the workpiece to be repaired, use sandpaper of appropriate grit to sand the defective area and the original coating in the adjacent area to remove loose coating, dust and oil stains. After sanding, clean the sanded area with a thinner. Color matching: Take a portion of the room temperature self-drying repair paint and apply it to the test panel. After it dries at room temperature, compare the color with the original coating. If the color difference exceeds the standard, add color matching pigments to fine-tune the color of the room temperature self-drying repair paint to be coated. Repair application: Apply room temperature self-drying repair paint (which does not require color matching or has undergone minor color adjustments) evenly to the defective area, making sure the thickness is slightly higher than the original coating surface, and then smooth it out. Room temperature air-drying curing: After the coating is applied, place the workpiece to be repaired in a room temperature environment to air dry naturally.

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