Method for infinitely adjusting gloss of automobile exterior matte varnish

Abstract

The invention provides a method for infinitely adjusting gloss of automobile exterior matte varnish. The method sequentially comprises the following steps: (a) spraying a primer layer on the surface of a base material; (b) spraying a colored paint layer on the primer layer, wherein the thickness of the colored paint film is controlled to be 15-25 microns; (c) a double-station varnish spraying process is adopted, wherein matte varnish with the single glossiness smaller than or equal to 10 GU is sprayed in the first station; in the second station, common transparent varnish is sprayed; (d) dynamically adjusting the ratio of the film thickness of the first station to the film thickness of the second station to 0: 100-100: 0 to enable the final glossiness to reach a target value of 5-90GU; and (e) storing the process parameter groups corresponding to different target gloss as callable codes. According to the method for infinitely adjusting the gloss of the automobile exterior matte varnish, traditional paint switching needs to be stopped to clean a pipeline for 8-12 hours, and according to the scheme, switching within 5 minutes is achieved through a code calling parameter set (claim 9); the requirement of scheduling more than five kinds of gloss orders per day is met, and the productivity utilization rate is increased by 25%.

Description

Technical Field

[0001] This disclosure belongs to the field of automotive exterior painting technology, specifically relating to a method for infinitely adjusting the gloss of automotive exterior matte clear coat. Background Technology

[0002] 1) As customer requirements become more diversified, in addition to the regular clear coat, each brand of automotive exterior parts has a demand for matte finishes, and the gloss requirements vary (6~10 for low gloss with a frosted texture, 20~40 for matte with regular colors, and 60~70 for metallic texture).

[0003] 2) The conventional process involves developing a specific matte clear coat for each gloss level, with a gloss adjustment range typically limited to ±5. For example, PPG offers matte clear coats such as LG-8, LG-17, LG-25, and LG-38 (each with a different content of matting agent). When producing products with different gloss requirements, the corresponding paint is switched.

[0004] Disadvantages of existing technology: 1) Paints with different gloss levels increase the variety of materials on site, increase logistics storage and management costs, and incur additional cleaning and switching losses.

[0005] 2) Due to limited on-site equipment, raw material switching and cleaning takes 8 to 12 hours. When there are more than 3 different gloss products scheduled for production in a single day, delivery cannot be made on time. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to provide a method for infinitely adjusting the gloss of matte clear coat for automotive exteriors.

[0007] To address the aforementioned problems, this invention provides a method for steplessly adjusting the gloss of matte clear coat on automotive exterior surfaces, comprising the following steps: (a) Apply a primer layer to the substrate surface; (b) Spray a color paint layer on the primer layer, and control the color paint film thickness to 15-25μm; (c) Adopting a dual-station clear coat spraying process: The first step involves spraying a matte clear coat with a single gloss level ≤10GU. The second step involves spraying a standard clear varnish. (d) Dynamically adjust the film thickness ratio between the first station and the second station to the range of 0:100 to 100:0, so that the final gloss reaches the target value of 5-90 GU; (e) Store the process parameter groups corresponding to different target glosses as callable codes.

[0008] Preferably, the matte varnish has a fixed and unique content of matting powder, and its original gloss level at a 60° measurement angle is 6-10 GU. The transparent varnish is a high-gloss varnish without added matting powder.

[0009] Preferably, the film thickness ratio adjustment follows a nonlinear control rule: When the target gloss level is 5-20 GU, the matte clear coat film thickness accounts for 70%-90%; When the target gloss level is 20-40 GU, the matte clear coat film thickness accounts for 40%-70%; When the target gloss level is 60-90 GU, the matte clear coat film thickness accounts for 10%-30%.

[0010] Preferably, in step (c), the total clear coat film thickness at both stations is 25-45 μm, and the film thickness fluctuation at each station is controlled within ±2 μm, wherein: The first stage features a matte clear coat with a film thickness ranging from 3 to 25 μm. The second stage of clear varnish film thickness ranges from 5-35μm.

[0011] Preferably, the paint layer in step (b) needs to meet the following requirements: Flash-drying time: 3-8 minutes; ambient humidity: 40%-70%; Metallic paint film thickness is 18-22μm, while ordinary paint film thickness is 20-25μm.

[0012] Preferably, the spraying process parameters in step (c) include: The first station uses a swirl cup speed of 25,000-35,000 rpm and a gun distance of 150-250 mm; The trajectory speed at the second station drops to 80%-90% of that at the first station, and the rate of overlapping guns is 30%-50%. The atomization pressure at both stations was controlled between 0.25 and 0.35 MPa.

[0013] Preferably, the parameter set in step (e) includes at least the following three types of data: (I) Film thickness parameters: film thickness of matte clear varnish and film thickness of transparent clear varnish; (II) Equipment parameters: rotary cup speed, atomization pressure, gun distance, trajectory speed; (III) Environmental parameters: paint flash-off humidity and varnish application temperature.

[0014] Preferably, the parameter groups are stored according to gloss range: Code A (Gloss 5-10 GU): Matte clear varnish film thickness 20-25μm, clear varnish film thickness 0-5μm, rotary cup speed ≥32,000rpm; Code B (Gloss 20-25GU): Matte clear varnish film thickness 12-18μm, clear varnish film thickness 10-15μm, gun distance 200±10mm; Code C (Gloss 40-45GU): Matte clear coat film thickness 8-12μm, transparent clear coat film thickness 20-25μm, trajectory speed 0.8m / s; Code D (Gloss 60-70GU): Matte clear coat film thickness 3-5μm, transparent clear coat film thickness 30-35μm, overlap rate ≤35%.

[0015] Preferably, when switching between products with different gloss levels, the parameter group is automatically invoked by inputting the product code, the switching response time is ≤5 minutes, and the switching process does not require cleaning the spraying equipment.

[0016] Preferably, it also includes a real-time gloss monitoring step: An online gloss meter was installed after the second spraying station. When the measured gloss deviates from the target value by ±3GU, the film thickness ratio of the next workpiece is automatically adjusted.

[0017] In summary, the present invention has at least one of the following beneficial technical effects: Material costs reduced by more than 90% Traditional solutions require stocking 6-8 types of matte clear coats (such as PPG's LG-8 / LG-17 / LG-25, etc.), while this solution only requires 1 type of matte coat + 1 type of clear coat; Based on an annual production of 1 million units, this can reduce inventory capital by approximately 3 million yuan per year (referencing the average price of automotive paint at 200 yuan per kilogram). Switching time has been reduced from hours to minutes. Traditional paint switching requires 8-12 hours of downtime for pipeline cleaning, while this solution achieves switching in ≤5 minutes by calling parameter groups via code (claim 9). To meet the demand for orders with more than 5 different gloss levels per day, capacity utilization has increased by 25% (proof case: mixed production of Shenlong S32 / Lantu H37). Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating the spraying sequence of the overall structure of the present invention; Figure 2 This is a database diagram of the present invention; Figure 3 This is a block diagram of the post-coating control of the sprayed film according to the present invention. Detailed Implementation

[0019] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0020] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0021] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0022] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0023] See also Figure 1 , Figure 2 and Figure 3 As shown in the figure, according to an embodiment of the present invention, a method for achieving stepless adjustment of gloss of automotive exterior matte clear coat is described in detail below in the order of execution: (a) Substrate pretreatment stage: A primer layer is uniformly sprayed on the surface of the metal or plastic substrate to build a basic protective system against corrosion and rust, providing an adhesion substrate for subsequent coatings.

[0024] (b) Color paint layer construction process: A precision color paint spraying operation is performed on the surface of the primer layer, wherein: The thickness of the paint film is strictly controlled within the range of 15-25μm and is monitored online using a laser thickness gauge. For metallic paints, set a flash-off time of 3-8 minutes and an ambient humidity of 40%-70%, and control the film thickness at 18-22μm; Ordinary paint systems maintain a film thickness standard of 20-25μm to ensure color stability; An infrared preheating device is used to maintain the substrate temperature at 25±2℃ to eliminate the risk of stress deformation.

[0025] (c) Dual-station clear coat composite spraying process: Constructing a two-stage series spraying system, including: First stop (matte layer spraying): The spray-applied matte clear varnish has an optimized and fixed content of matte powder to ensure that the original gloss level at a 60° measurement angle remains constant within the range of 6-10 GU. The film thickness can be adjusted from 3 to 25 μm, and μm-level precision control is achieved through a solenoid valve assembly. Spraying parameter settings: rotary cup speed 25,000-35,000 rpm, gun distance 150-250 mm, atomization pressure 0.25-0.35 MPa.

[0026] Second station (transparent layer spraying): Spray a high-gloss clear varnish without matting agent to form a gloss-enhancing layer; The film thickness can be adjusted from 5 to 35 μm, forming a total film thickness system of 25 to 45 μm with the first station; Process parameter optimization: The trajectory speed is reduced by 10%-20% compared to the first station, and the stacking rate is controlled at 30%-50% to ensure interlayer bonding.

[0027] (d) Dynamic film thickness control system: Closed-loop control of the spraying flow rate at both stations is achieved through a metering pump group driven by a servo motor. The film thickness ratio adjustment follows a three-level nonlinear control rule: Target gloss range of 5-20 GU: Matte clear coat accounts for 70%-90%, forming a low-gloss base; Target gloss range of 20-40 GU: Matte clear coat accounts for 40%-70%, with gradual control in the transition zone; Target gloss range of 60-90 GU: Matte clear coat accounts for 10%-30%, and high gloss layer dominates surface characteristics; The single-station film thickness fluctuation was controlled within ±2μm, and the paint mist particle size distribution was monitored using a Malvern particle size analyzer.

[0028] (e) Digital packaging of process parameters: Establish a multi-dimensional parameter database and store it according to gloss range: Code A (5-10GU): Matte layer 20-25μm / Transparent layer 0-5μm, Rotary cup speed ≥32,000rpm; Code B (20-25GU): Matte layer 12-18μm / Transparent layer 10-15μm, gun spacing 200±10mm; Code C (40-45GU): Matte layer 8-12μm / Transparent layer 20-25μm, trajectory speed 0.8m / s; Code D (60-70GU): Matte layer 3-5μm / Transparent layer 30-35μm, overlap ratio ≤35%; The parameter group includes three main categories of data: film thickness parameters, equipment parameters (rotary cup speed, atomization pressure, gun distance, trajectory speed), and environmental parameters (color paint flash-off humidity, varnish application temperature). When switching production, the product code is entered through the HMI, and the system automatically calls the preset parameter group, extending the equipment cleaning cycle to ≥72 hours and the switching response time to ≤5 minutes.

[0029] (f) Closed-loop quality control system: An online gloss meter is installed at the second station's spraying exit, and 100% full inspection is carried out using 60° geometric conditions; A PID feedback control system is established so that when the measured gloss deviates from the target value by ±3GU, the film thickness compensation algorithm for the next workpiece is automatically triggered. The historical data storage module records the parameter combinations for each workpiece, forming a process big data platform.

[0030] This process, through a double-layer clear coat design, breaks through the limitations of traditional single-layer clear coat gloss adjustment while maintaining a constant concentration of matte powder. It achieves continuous adjustability from 5GU ultra-matte to 90GU high gloss, making it particularly suitable for flexible production lines that require rapid switching between different gloss levels.

[0031] It will be readily understood by those skilled in the art that the aforementioned advantageous methods can be freely combined and superimposed without conflict.

[0032] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention. The above are merely preferred embodiments of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the protection scope of the present invention.

Claims

1. A method for infinitely adjusting the gloss of matte clear coat on automotive exterior surfaces, characterized in that, The steps are as follows: (a) Apply a primer layer to the substrate surface; (b) Spray a color paint layer on the primer layer, and control the color paint film thickness to 15-25μm; (c) Adopting a dual-station clear coat spraying process: The first step involves spraying a matte clear coat with a single gloss level ≤10GU. The second step involves spraying a standard clear varnish. (d) Dynamically adjust the film thickness ratio between the first station and the second station to the range of 0:100 to 100:0, so that the final gloss reaches the target value of 5-90 GU; (e) Store the process parameter groups corresponding to different target glosses as callable codes.

2. The method for infinitely adjusting the gloss of matte clear coat on automotive exteriors according to claim 1, characterized in that: The matte varnish has a fixed and unique content of matting powder, and its original gloss level at a 60° measurement angle is 6-10 GU. The transparent varnish is a high-gloss varnish without added matting powder.

3. The method for infinitely adjusting the gloss of matte clear coat on automotive exteriors according to claim 1, characterized in that: The film thickness ratio adjustment follows a nonlinear control rule: When the target gloss level is 5-20 GU, the matte clear coat film thickness accounts for 70%-90%; When the target gloss level is 20-40 GU, the matte clear coat film thickness accounts for 40%-70%; When the target gloss level is 60-90 GU, the matte clear coat film thickness accounts for 10%-30%.

4. The method for infinitely adjusting the gloss of matte clear coat on automotive exteriors according to claim 1, characterized in that: In step (c), the total clear coat film thickness at both stations is 25-45 μm, and the film thickness fluctuation at each station is controlled within ±2 μm. The first stage features a matte clear coat with a film thickness ranging from 3 to 25 μm. The second stage of clear varnish film thickness ranges from 5-35μm.

5. The method for infinitely adjusting the gloss of matte clear coat on automotive exteriors according to claim 1, characterized in that: The paint layer in step (b) must meet the following requirements: Flash-drying time: 3-8 minutes; ambient humidity: 40%-70%; Metallic paint film thickness is 18-22μm, while ordinary paint film thickness is 20-25μm.

6. The method for infinitely adjusting the gloss of matte clear coat on automotive exteriors according to claim 1, characterized in that: The spraying process parameters for step (c) include: The first station uses a swirl cup speed of 25,000-35,000 rpm and a gun distance of 150-250 mm; The trajectory speed at the second station drops to 80%-90% of that at the first station, and the rate of overlapping guns is 30%-50%. The atomization pressure at both stations was controlled between 0.25 and 0.35 MPa.

7. The method for infinitely adjusting the gloss of matte clear coat on automotive exteriors according to claim 1, characterized in that: The parameter group in step (e) contains at least the following three types of data: (I) Film thickness parameters: film thickness of matte clear varnish and film thickness of transparent clear varnish; (II) Equipment parameters: rotary cup speed, atomization pressure, gun distance, trajectory speed; (III) Environmental parameters: paint flash-off humidity and varnish application temperature.

8. The method for infinitely adjusting the gloss of matte clear coat on automotive exteriors according to claim 7, characterized in that: The parameter groups are stored according to gloss range: Code A (Gloss 5-10 GU): Matte clear varnish film thickness 20-25μm, clear varnish film thickness 0-5μm, rotary cup speed ≥32,000rpm; Code B (Gloss 20-25GU): Matte clear varnish film thickness 12-18μm, clear varnish film thickness 10-15μm, gun distance 200±10mm; Code C (Gloss 40-45GU): Matte clear coat film thickness 8-12μm, transparent clear coat film thickness 20-25μm, trajectory speed 0.8m / s; Code D (Gloss 60-70GU): Matte clear coat film thickness 3-5μm, transparent clear coat film thickness 30-35μm, overlap rate ≤35%.

9. The method for infinitely adjusting the gloss of matte clear coat on automotive exteriors according to claim 1, characterized in that: When switching between products with different gloss levels, the parameter group is automatically invoked by entering the product code. The switching response time is ≤5 minutes, and the switching process does not require cleaning the spraying equipment.

10. The method for infinitely adjusting the gloss of matte clear coat on automotive exteriors according to claim 1, characterized in that: It also includes a real-time gloss monitoring step: An online gloss meter was installed after the second spraying station. When the measured gloss deviates from the target value by ±3GU, the film thickness ratio of the next workpiece is automatically adjusted.

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