Color register process for double-color spraying of vehicle body

Abstract

The invention relates to the field of vehicle coating and sleeving, in particular to a color register process for double-color spraying of a vehicle body, which comprises the following steps: pretreatment, electrophoresis, electrophoresis drying and cooling, coating of a weld joint sealant and stone-chip-resistant prime coat, and spraying and color register of a vehicle roof. Spraying a car roof color register coating on a specific area of the car roof, drying and cooling glue, spraying a car body midway, spraying car body colored paint, spraying car body varnish, and drying and cooling car paint; the color register method disclosed by the invention meets the production requirements of the double-color vehicle with the roof and the vehicle body; according to the invention, by adjusting the spraying and color register process of the car roof, spraying and color register are not needed, and a special color register line is not needed; the change of the whole coating line is small, and the investment cost of the coating line is low; according to the invention, the weld joint sealant is coated, and the stone-chip-resistant prime coat and the roof coating are synchronously dried; traditional step-by-step drying is avoided; and the drying time is shortened, and the production takt of color register is reduced.

Description

Technical Field

[0001] This invention relates to the field of vehicle painting and overlay, specifically to a two-color overlay process for vehicle body painting. Background Technology

[0002] With the increasing trend of personalized car consumption, the market demand for two-tone car bodies (especially roofs and body bodies in different colors) is growing rapidly.

[0003] Existing technologies mainly employ the following two color matching schemes:

[0004] Offline backwash solution:

[0005] After the entire vehicle body is painted, it is transferred to a dedicated color matching line, where the roof is painted a different color through masking, repainting, and secondary drying.

[0006] This solution requires the addition of an independent drying oven, masking fixtures, and a conveying system. The equipment investment is high, the footprint is large, and the secondary high-temperature baking can easily cause thermal shock to the base coat, resulting in defects such as color difference and loss of gloss.

[0007] Online masking color matching scheme:

[0008] Although this solution reduces the need for transshipment, it still requires two drying systems, resulting in high energy consumption and significant cycle time loss.

[0009] In addition, both of the above solutions require multiple shading and repeated drying, which leads to a significant increase in equipment costs and energy consumption.

[0010] Multiple thermal processes increase the risk of paint film defects, making it difficult to simultaneously meet the stringent requirements of ΔE≤1, weather resistance of 3000h, and no structural corrosion for 10 years.

[0011] Patent document 2 (CN111589629A) discloses a two-color painting system for car bodies, including: a first car body painting line, a second car body painting line, a car body exchange and transfer mechanism, and a car body return line; wherein, the car body exchange and transfer mechanism includes a second car body transfer structure between the first car body transfer structure and the second car body inspection and off-line mechanism, the first car body transfer structure and the second car body transfer structure are interconnected and cooperate to transfer the car body from the first car body painting line to the second car body painting line; the car body return line includes a third car body transfer structure and a car body off-line conveying mechanism; although this patent can realize two-color painting of car bodies, the overall structure is relatively complex and requires reciprocating transfer lines.

[0012] Therefore, in order to improve or solve at least one of the above technical problems, it is necessary to optimize the existing vehicle color matching process. Summary of the Invention

[0013] The purpose of this invention is to provide a simple and fast-paced two-tone color matching process for car bodies.

[0014] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0015] A two-tone painting process for automotive bodies, the two-tone process comprising the following steps:

[0016] Step 1: Pre-processing;

[0017] Step 2: Electrophoresis, electrophoretic drying and cooling;

[0018] Step 3: Apply weld sealant and anti-stone chip primer;

[0019] Step 4: Apply two-tone paint to the roof; apply a two-tone coating to specific areas of the roof.

[0020] Step 5: Drying and cooling the adhesive;

[0021] Step 6: Mid-process painting of the vehicle body;

[0022] Step 7: Paint application on the vehicle body;

[0023] Step 8: Apply clear coat to the car body;

[0024] Step 9: Drying and cooling of the paint.

[0025] In step 5, it is required that the weld sealant, anti-stone chip primer, and roof color coating be dried as a whole.

[0026] Before step 4 begins, the weld sealant and anti-stone impact primer applied in step 3 are not yet dry.

[0027] In step 5, the adhesive drying temperature shall not be lower than 120℃.

[0028] In step 4, it is required to use a roof color-coating robot to perform roof color-coating.

[0029] The roof paint is a single-layer paint.

[0030] The thickness of the color-coated roof coating is ≤60μm.

[0031] After step 9 is completed, the wax injection process is carried out to inject wax into the weld seams of the vehicle body cavity where the electrophoretic coating is weak and cannot be protected by adhesive.

[0032] In step 4, it is required that the non-roof areas be masked before the roof is painted with different colors. The masking material is an electrostatic adsorption film with a temperature resistance of 120°C or higher.

[0033] The drying temperature in step 9 shall not be lower than 140°C.

[0034] The advantages of this invention are:

[0035] This invention discloses a two-color painting process for automotive bodies.

[0036] The color matching method disclosed in this invention meets the production needs of two-tone vehicles with a roof and body.

[0037] In addition, by adjusting the roof painting color matching process, this invention eliminates the need for repainting and color matching, and eliminates the need for a dedicated color matching line; the overall painting line requires minimal changes, resulting in low investment costs for the painting line.

[0038] In addition, the present invention simultaneously dries the weld sealant, anti-stone chip primer and roof coating; avoids the traditional step-by-step drying; reduces drying time and helps to reduce the production cycle of color matching. Detailed Implementation

[0039] The following description of the preferred embodiment will provide a more detailed explanation of the specific implementation of the present invention.

[0040] A two-tone painting process for automotive bodies, the two-tone process comprising the following steps:

[0041] Step 1: Pre-processing;

[0042] Objective: To clean the surface of the white body (the welded body) of impurities such as oil, iron filings, welding slag, and oxide layer, and to form a conversion film (usually a phosphating film) on the metal surface, providing a good adhesion substrate and anti-corrosion base for subsequent electrophoresis.

[0043] Process: Includes degreasing (oil removal), water washing, surface conditioning, phosphating, water washing, and pure water washing.

[0044] A combination of spraying and immersion is usually used.

[0045] Step 2: Electrophoresis, electrophoretic drying and cooling;

[0046] Electrophoresis:

[0047] Purpose: The most crucial corrosion prevention process;

[0048] The pre-treated car body is immersed in an electrophoretic paint tank. Under the action of a direct current electric field, charged paint particles are evenly deposited onto all the inner and outer surfaces of the car body (including cavity structures), forming a dense and uniform primer film (electroplated paint film).

[0049] It has high penetration power and can cover gaps and cavities that are difficult to reach with ordinary spraying, providing excellent rust and corrosion protection.

[0050] Electrophoresis drying and cooling:

[0051] Objective: To cure the electrophoretic coating film at high temperature in an oven to achieve its optimal anti-corrosion and physical properties. After baking, it needs to be cooled to a suitable temperature for subsequent operations.

[0052] Step 3: Apply weld sealant and anti-stone chip primer;

[0053] Weld sealant: PVC (polyvinyl chloride) or other types of sealant are applied manually or robotically to critical weld seams on the vehicle body (such as door frames, wheel arches, floor joints, etc.). Its main functions are to seal and prevent leaks (waterproofing, dustproofing, noise reduction) and to reinforce the structure.

[0054] Stone chip protection primer: A thick layer of PVC or other elastic material coating (commonly known as "chassis armor") is sprayed onto the underside of the vehicle body, inside wheel arches, and other areas susceptible to impact from flying stones on the road. Its main functions are to resist stone chips (prevent stones from damaging the primer and causing rust), sound insulation, noise reduction, and sealing.

[0055] The two steps of applying weld sealant and anti-stone chip primer are usually performed simultaneously or completed in the same section.

[0056] Step 4: Apply two-tone paint to the roof; apply a two-tone coating to specific areas of the roof.

[0057] Purpose: If the vehicle design has a two-tone body (the roof is a different color from the main body), the roof will be masked at this work station, and then the required roof color coating will be sprayed on.

[0058] Step 5: Drying and cooling the adhesive;

[0059] Function: Simultaneous curing. Cures weld sealant, anti-stone chip primer, and roof overcoat simultaneously within a single drying oven.

[0060] Effect: This is the key coupling point for achieving process innovation.

[0061] A drying temperature of 120°C is a common temperature window for both the adhesive and this particular single-coat paint to cure effectively.

[0062] It enables heat energy reuse, combining the original two drying processes (adhesive drying + paint drying) into one, significantly improving production efficiency and reducing energy consumption.

[0063] Step 6: Mid-process painting of the vehicle body;

[0064] Purpose:

[0065] Filling and leveling: Covers any minor unevenness that may exist in the electrophoretic layer and adhesive layer, providing a smoother base for the topcoat.

[0066] Increase adhesion: Improve the bonding strength between the paint and the substrate.

[0067] UV protection: Some intermediate coats can provide some UV protection and protect the substrate.

[0068] Enhance appearance: Improve the fullness and gloss of the final topcoat.

[0069] It is usually painted automatically by robots.

[0070] Step 7: Paint application on the vehicle body;

[0071] Objective: To provide the final color and color effect of the car body.

[0072] Process: Automatic spraying by high-precision robots.

[0073] Step 8: Apply clear coat to the car body;

[0074] Purpose: To spray a transparent coating onto the outermost layer.

[0075] Protective paint: Resists UV rays, chemicals (acid rain, bird droppings, etc.), car wash brushes, and minor scratches.

[0076] Provides gloss and fullness: makes the car body surface as shiny as a mirror.

[0077] Improved durability: Extends the lifespan of the overall paint finish.

[0078] Process: This process is carried out immediately after the color paint spraying (wet-on-wet process), and is usually done by robots.

[0079] Step 9: Drying and cooling of the paint.

[0080] Purpose: To cure the paint and varnish at high temperature in a baking oven to form a hard, glossy, and durable final paint surface.

[0081] This is the most important and final high-temperature baking process on the entire painting line.

[0082] After baking, the food must be cooled to room temperature.

[0083] Paint and varnish are usually dried and cured in the same oven in one go.

[0084] specific:

[0085] This invention discloses a two-color painting process for automotive bodies;

[0086] Step 1: Pre-processing

[0087] Function: Cleaning and conversion. Removes contaminants such as grease, welding slag, and dust from the surface of the car body, and forms a dense phosphate conversion film (phosphating film) on the clean metal surface through a phosphating reaction.

[0088] Effects: Provides a clean substrate: ensures that subsequent coatings adhere firmly to the metal substrate and prevents coating defects (such as pinholes and peeling) caused by contamination.

[0089] Enhanced corrosion resistance: The phosphating film itself has a certain degree of corrosion resistance and can greatly improve the adhesion and corrosion resistance of electrophoretic paint.

[0090] The parameter "water film continuity" is a direct standard for testing cleanliness.

[0091] Step 2: Electrophoresis and electrophoretic drying and cooling;

[0092] Function: Basic corrosion protection.

[0093] Using electrochemical principles, charged electrophoretic paint particles are uniformly deposited onto the entire interior and exterior surfaces of the car body (including cavities and gaps) to form a uniform primer coating, which is then baked and cured.

[0094] Effect: This is the cornerstone of vehicle corrosion prevention.

[0095] "No structural corrosion for 10 years" and "0-level rust in 1000h neutral salt spray test" are the core indicators for measuring the quality of the electrophoretic layer, meaning that it can effectively resist the erosion of moisture and electrolytes from the environment and protect the steel plate itself.

[0096] Step 3: Apply weld sealant and anti-stone chip primer;

[0097] Function: To enhance protection.

[0098] Targeted reinforcement protection should be provided for areas where the electrophoretic layer coverage is relatively weak.

[0099] Weld sealant: fills the gaps at the weld joints of steel plates, serving to seal (waterproof, dustproof, soundproof) and reinforce the structure.

[0100] Stone-resistant primer (PVC coating): A thick and elastic PVC coating is sprayed onto areas of the vehicle body, such as the underbody and wheel arches, which are susceptible to impact from flying stones on the road, to prevent the stones from penetrating the coating and causing the steel plate to rust.

[0101] Effect: Together with the electrophoretic layer, it forms a complete primary anti-corrosion system for the car body, ensuring the goal of "no structural corrosion for 10 years".

[0102] "Adhesion grade 0" indicates that the adhesive is extremely firmly bonded to the electrophoretic layer.

[0103] Step 4: Two-tone paint application on the roof (core innovation);

[0104] Function: Personalized color application.

[0105] Before the adhesive has cured, the roof area is pre-painted with a different color than the rest of the vehicle body.

[0106] Mechanism and effects:

[0107] Timing innovation (before adhesive drying): Utilizing the time window between steps 3 and 5 allows the roof coating to dry together with the weld adhesive, eliminating a separate drying process and significantly saving energy and time.

[0108] Technology Integration (Single-Layer Coating): Utilizing a multi-functional, high-performance coating, a single-layer coating is required to achieve the following:

[0109] Intermediate coating function: good leveling and filling properties, covering unevenness in the underlying layer.

[0110] Color paint function: accurate color rendering capability (ΔE≤1).

[0111] Clear varnish function: Provides surface hardness, gloss and critical weather resistance (UV resistance ≥3000h).

[0112] High efficiency and economy: The requirement of "thickness ≤60μm" is much thinner than the total thickness of traditional three-coat layers (usually >100μm), which reduces the amount of paint used and lowers the cost.

[0113] This move avoids the need to establish an expensive dedicated color-matching production line.

[0114] Step 5: Drying and cooling the adhesive;

[0115] Function: To cure simultaneously.

[0116] In a drying oven, weld sealant, anti-stone chip primer, and roof color coating are cured simultaneously.

[0117] Effect: This is the key coupling point for achieving process innovation.

[0118] The drying temperature of 120℃ is a common temperature window for both the adhesive and this specific single-coat paint to cure effectively; it enables heat energy reuse, combining the original two drying processes (adhesive drying + color paint drying) into one, significantly improving production efficiency and reducing energy consumption.

[0119] Step 6: Apply intermediate coat to the vehicle body;

[0120] Function: Filling and smoothing: Covers up minor imperfections in the electrophoretic layer, providing an extremely smooth base for subsequent color paints.

[0121] Isolation and protection: Enhances the overall coating thickness and impermeability.

[0122] The purpose of the base color is to allow you to choose a color similar to the paint, thereby reducing the amount of topcoat paint needed and lowering costs.

[0123] Step 7: Apply body paint & Step 8: Apply body clear coat;

[0124] Function: To give the vehicle body its color and provide final protection.

[0125] Paint: Provide the design color for the main body of the vehicle, requiring accurate color (ΔE≤1) and uniform effect (metallic, pearlescent).

[0126] Clear varnish: As the outermost layer, it directly withstands the test of the external environment. It provides high gloss, abrasion resistance, chemical resistance (acid rain, bird droppings), and most importantly, UV resistance, protecting the underlying paint from fading and chalking.

[0127] Effect: "Long Wave (LW) ≤ 7, Short Wave (SW) ≤ 15" are indicators for measuring the smoothness of the paint surface. The lower the value, the smoother the appearance. "Difference of Reflection (DOI) ≥ 90" indicates that the image reflection is extremely clear, like a mirror.

[0128] Both together ensure a high-quality visual effect;

[0129] Step 9: Topcoat drying and cooling

[0130] Function: Final curing. At temperatures above 140℃, the intermediate coat, color coat, and clear coat (main body coating) undergo a complete cross-linking reaction, curing to form a hard, durable, and high-performance paint finish.

[0131] Effect: Ensures all coating properties (mechanical properties, weather resistance, chemical resistance) meet design specifications. Forced cooling to room temperature after baking prepares the material for subsequent processes.

[0132] Wax injection process:

[0133] Function: Long-term corrosion protection for cavities.

[0134] Liquid wax is injected into the closed cavities of the vehicle body (such as door sills, pillars, and longitudinal beams) through a special wax injection hole, and the wax adheres to the inner wall to form a protective film.

[0135] Effect: Prevents moisture and salt from accumulating in the cavity and causing internal corrosion. It is the last and most important line of defense to achieve "10 years without structural corrosion".

[0136] A wax film thickness of ≥100μm ensures the durability of the protection.

[0137] The effects of the above-mentioned color-matching process of the present invention are as follows:

[0138] This color-coating process successfully achieved the following objectives:

[0139] High performance and high quality: The final product meets all stringent automotive coating standards (10 years of corrosion protection, appearance, color difference, and 3000h weather resistance).

[0140] Personalization and aesthetics: It effectively achieves a two-tone effect on the roof and the main body of the vehicle, meeting the market's demand for personalization.

[0141] High efficiency and low cost:

[0142] Process integration: The color matching process is embedded into the main process of the body-in-white, eliminating the need for a separate color matching line.

[0143] Heat reuse: The roof coating and adhesive are dried together, saving the energy consumption and time of a drying oven.

[0144] Material saving: The single coating on the roof is thin and eliminates the need for intermediate and clear coat materials.

[0145] Technological advancement: The core lies in the development and application of a high-performance roof color coating that can meet the "three-in-one" functional requirements, and the finding of the optimal process sequence (spraying before the adhesive is dry) and process parameters (co-drying at 120℃) to match it.

[0146] This process is a model of combining lean manufacturing and material innovation in the automotive painting industry, significantly improving production efficiency and economy while ensuring quality.

[0147] Furthermore, in step 5 of this invention, it is required that the weld sealant, anti-stone chip primer, and roof color coating be dried as a whole; the three materials with different properties, namely weld sealant, anti-stone chip primer, and roof color coating, are cured in the same drying oven under the same temperature control curve.

[0148] By drying the entire product at 120℃, this invention enables the weld sealant, anti-stone impact primer, and roof color coating to complete key cross-linking simultaneously without adding any new furnace body. This allows for the reuse of thermal energy sequence: a single heating process simultaneously meets the curing requirements of the three materials; overall cost is reduced and cycle time is shortened.

[0149] The heat generated by the drying oven is absorbed and utilized by the three materials simultaneously, without any order of absorption.

[0150] Furthermore, before step 4 begins in this invention, the weld sealant and anti-stone-impact primer applied in step 3 are not yet dry; this setting is done in a drying oven, where the weld sealant, anti-stone-impact primer, and roof color coating are cured simultaneously.

[0151] Furthermore, in step 5 of this invention, the adhesive drying temperature is not lower than 120°C; 120°C is a common temperature window where both the adhesive and this specific single-coat paint can be effectively cured; this achieves heat energy reuse, combining the original two drying processes (adhesive drying + color paint drying) into one, significantly improving production efficiency and reducing energy consumption.

[0152] Furthermore, in step 4 of this invention, a roof color-coating robot is required to perform roof color-coating; this setup facilitates roof color-coating. In addition, the type of roof color-coating robot can be selected as needed in this invention.

[0153] In this invention, the roof painting color matching is a single-layer painting. Based on this design, this invention can improve the efficiency of roof painting color matching. At the same time, the use of single-layer painting can reduce the amount of paint used for single-layer painting. Single-layer painting means that only one painting operation is needed, which greatly shortens the operation time of this station and avoids the waiting, leveling, and color changing time required for multiple painting operations, thus ensuring the smoothness of the production line.

[0154] In actual design, the thickness of the roof overcoat is required to be ≤60μm; the film thickness is ≤60μm, which is both a reflection of material performance and a quantitative indicator of economy. This value is to achieve the best cost while ensuring functionality. Too thick a film will affect drying efficiency, while too thin a film will not meet performance requirements.

[0155] The thinner the coating, the faster the solvents and moisture can escape at the relatively low temperature of 120℃, and the more fully the resin and curing agent can cross-link and react, thus achieving complete curing. Overly thick coatings are prone to problems such as "dry on the outside but not on the inside," stickiness, and performance degradation at low temperatures.

[0156] This directly reduces the amount of expensive effect pigments and resins used, thus lowering production costs.

[0157] Furthermore, after step 9 of the present invention is completed, the process proceeds to the wax injection process, where wax is injected into the weld seams of the vehicle body cavity where the electrophoretic coating is weak and cannot be protected by adhesive.

[0158] Waxing is an important process for preventing corrosion in the body's cavities; it involves injecting liquid or wax-like rust-preventive wax into the closed cavities of the body structure (such as the inner cavity of the door, longitudinal beams, cross beams, side panels, pillars, etc.).

[0159] The wax liquid forms a protective film on the inner wall of the cavity, isolating moisture and oxygen and preventing the cavity from rusting due to long-term dampness.

[0160] The car body is injected with wax through a wax injection device, using pressure or vacuum to inject wax into each cavity via preset wax injection holes; excess wax will flow out from the wax discharge hole and be recycled.

[0161] This is the final process in the painting workshop. After completion, the car body will have complete anti-corrosion and exterior protection, and will be ready to enter the final assembly workshop.

[0162] Final assembly:

[0163] The painted car body (at this point called the "painted car body") is transported to the final assembly workshop, where all components such as the engine, chassis, interior (seats, dashboard, etc.), electrical system, doors, glass, and tires are installed, ultimately assembling a complete, drivable car.

[0164] Furthermore, in step 4 of this invention, it is required that the non-roof areas be masked before the roof is painted with the color-coated coating. The masking material is an electrostatic adsorption film with a temperature resistance of 120°C or higher. When painting the roof color-coated coating, it is necessary to ensure that the paint adheres precisely only to the designed roof area.

[0165] The purpose of the shielding is to physically isolate non-roof areas (such as the windshield frame, A-pillar, B-pillar, C-pillar, sunroof area, etc.) to prevent these parts from being accidentally sprayed with paint of the same color as the roof.

[0166] The masking film is applied in step 4 (before spraying). After that, the car body will go directly into the drying oven in step 5 and stay at ≥120℃ for 20-30 minutes.

[0167] This invention uses a specially designed high-temperature resistant masking film, whose substrate and adhesive can stably withstand baking temperatures above 120°C, maintain shape, adhesion and chemical stability throughout the drying process, and can be cleanly peeled off after cooling without leaving any residue.

[0168] Furthermore, in step 9 of this invention, the drying temperature is not lower than 140°C; the intermediate coat, color paint, and clear coat (especially the clear coat) of the car body are mainly thermosetting coatings, and their film-forming process is not a simple physical drying, but involves complex chemical reactions; temperature is the most critical factor driving the speed and extent of this chemical reaction; 140°C is the critical temperature to ensure that these reactions are fully and thoroughly completed within the time required by the production line cycle.

[0169] Example 1:

[0170] Single-layer spray coating with multiple colors:

[0171] It mainly enables two-tone painting of the roof and body. The main process is as follows: body pretreatment → electrophoresis → electrophoresis drying and cooling → weld sealant and anti-stone chip primer → roof two-tone painting → adhesive drying and cooling → intermediate coat spraying → color paint spraying → clear coat spraying → topcoat drying and cooling → wax injection → final assembly.

[0172] Main functions and parameters of pretreatment: to clean and remove oil from steel plate bodies, with an oil removal rate of 100% and continuous water film; to form a pretreatment film on the clean steel plate surface to ensure a tight bond between the steel plate and the electrophoretic layer, with a film thickness of 100-200nm.

[0173] The main functions and parameters of electrophoresis + drying / cooling: A dense electrophoretic coating is formed on the surface of the steel plate, achieving no structural corrosion of the steel plate for 10 years and rust level 0 after 1000 hours of electrophoretic neutral salt spray.

[0174] Main functions and parameters of weld sealant and anti-stone chip primer: Apply sealant to the weld seams of steel plates with weak electrophoretic coating and the underside of the vehicle in harsh environments to achieve 10 years of structural corrosion-free vehicle body, with complete sealant coverage and adhesion grade 0.

[0175] The main function and parameters of roof painting with multiple colors: After applying adhesive but before it dries, the roof area is painted with a different color than the subsequent body parts, fulfilling the personalized multiple-color requirements of the roof. At this stage, the roof painting is a single-coat application, combining the subsequent intermediate coat, color coat, and clear coat into a single layer. This requires high-performance coatings: coating thickness ≤ 60 micrometers, color difference from the standard ≤ 1, and resistance to xenon lamp aging ≥ 3000 hours.

[0176] The main functions and parameters of adhesive drying and cooling are as follows: to dry the weld sealant, anti-stone chip primer, and roof color coating as a whole, with a drying temperature of at least 120℃.

[0177] The main functions and parameters of intermediate coating spraying are: to fill the electrophoretic coating to ensure a good overall appearance of the subsequent coating, and at the same time, to reduce the amount of paint used in the subsequent color paint coating by providing a certain degree of color coverage. The thickness of the intermediate coating is 12-30 micrometers.

[0178] Main functions and parameters of paint spraying: To achieve the main body color spraying of the vehicle body, with a standard color difference of ≤1.

[0179] Main functions and parameters of clear coat spraying: to achieve a good overall appearance of the vehicle body, to provide UV protection for the underlying paint, electrophoresis, etc., and to ensure that the appearance has a long wavelength ≤7, a short wavelength ≤15, a clearness ≥90, and that the coating can withstand xenon lamp aging ≥3000h.

[0180] Main functions and parameters of topcoat drying and cooling: To ensure the overall drying of intermediate coat, color paint and clear coat, and to ensure the paint film is dry. The drying temperature is at least 140℃.

[0181] The main function and parameters of wax injection: to inject wax into the weld seams of the car body cavity where the electrophoretic coating is weak and cannot be protected by adhesive, so that the weld seams of the cavity are protected by the flow of wax liquid to achieve no structural corrosion for 10 years, and the wax film thickness is ≥100 micrometers.

[0182] This invention eliminates the need for back-spraying for color matching and a dedicated color matching line. It utilizes adhesive drying to achieve color matching on the car roof. The color matching coating simultaneously functions as a primer, color paint, and clear coat, meeting the requirements for coloring, aging, and UV protection.

[0183] Obviously, the specific implementation of this invention is not limited to the above-described methods. Any non-substantial improvements made using the inventive concept and technical solution of this invention are within the protection scope of this invention.

Claims

1. A two-tone painting process for car bodies, characterized in that, The color matching process includes the following steps: Step 1: Pre-processing; Step 2: Electrophoresis, electrophoretic drying and cooling; Step 3: Apply weld sealant and anti-stone chip primer; Step 4: Apply two-tone paint to the roof; apply a two-tone coating to specific areas of the roof. Step 5: Drying and cooling the adhesive; Step 6: Mid-process painting of the vehicle body; Step 7: Paint application on the vehicle body; Step 8: Apply clear coat to the car body; Step 9: Drying and cooling of the paint.

2. The two-tone painting process for a car body according to claim 1, characterized in that, In step 5, it is required that the weld sealant, anti-stone chip primer, and roof color coating be dried as a whole.

3. A two-tone painting process for vehicle bodies according to any one of claims 1-2, characterized in that, Before step 4 begins, the weld sealant and anti-stone impact primer applied in step 3 are not yet dry.

4. The two-tone painting process for a car body according to claim 1, characterized in that, In step 5, the adhesive drying temperature shall not be lower than 120℃.

5. The two-tone painting process for a car body according to claim 1, characterized in that, In step 4, it is required to use a roof color-coating robot to perform roof color-coating.

6. The two-tone painting process for a car body according to claim 1, characterized in that, The roof paint is a single-layer paint.

7. The two-tone painting process for a car body according to claim 6, characterized in that, The thickness of the color-coated roof coating is ≤60μm.

8. The two-tone painting process for a car body according to claim 1, characterized in that, After step 9 is completed, the wax injection process is carried out to inject wax into the weld seams of the vehicle body cavity where the electrophoretic coating is weak and cannot be protected by adhesive.

9. The two-tone painting process for a car body according to claim 1, characterized in that, In step 4, it is required that the non-roof areas be masked before the roof is painted with different colors. The masking material is an electrostatic adsorption film with a temperature resistance of 120°C or higher.

10. The two-tone painting process for a car body according to claim 1, characterized in that, The drying temperature in step 9 shall not be lower than 140°C.