Method for judging floating resistance of colored paint in automobile coating process

Abstract

The invention discloses a method for judging the anti-floating capability of colored paint in the automobile coating process, which comprises the following steps: a gluing plate is provided, and the gluing plate structurally comprises a test plate with a first surface and a second surface which are correspondingly arranged, and a sealing glue block which is cured and combined on the first surface; the temperature of the sealant block obtained after curing is higher than the normal temperature, and heat provided by the sealant block enables the temperature of the area, corresponding to the sealant block, on the second surface to at least reach the expected temperature; the temperature of the area, corresponding to the sealing rubber block, of the second surface is adjusted to be the expected temperature, according to the paint coating technology, the area, at least corresponding to the sealing rubber block, of the second surface is coated with automobile paint containing colored paint, and a coating is formed; and visually observing or measuring and judging the anti-floating capability of the coating by adopting a cloud and mist instrument. According to the method, the floating resistance of the colored paint can be quickly, intuitively and accurately judged in a laboratory.

Description

Technical Field

[0001] This invention relates to the field of paint blooming detection. More specifically, it relates to a method for determining the resistance to blooming of paint during automotive painting. Background Technology

[0002] When manufacturing cars, manufacturers need to paint the chassis, body, and other parts to protect the vehicle from corrosion and enhance its appearance. The paint job is the most significant visual impression a car leaves on consumers, making it crucial.

[0003] During the production process in the painting workshop, the temperature uniformity of the entire vehicle body may be inconsistent. In particular, when sealant is applied to the inner panels of the vehicle body, the areas on the outer panels that are normally painted with automotive paint are prone to developing uneven coloring, which in turn affects the painting quality.

[0004] "Flourish" refers to uneven coloring on the coating surface, resulting in various honeycomb-like or striped patterns, hence the name "zebra stripes." The main reason is that during the paint drying process, the evaporation of the solution on the paint film surface causes differences in temperature, surface tension, solution concentration, and density within the film. The surface tension at the edge of the vortex is higher than that at the center, causing the paint to flow from areas of low surface tension to areas of high surface tension. To balance this thermodynamic equilibrium, flow occurs within the coating film. This flow creates Bénard vortices on the dry film surface. This unevenness during the drying process results in a significantly uneven appearance of the dried paint film. Summary of the Invention

[0005] To address the above problems, the present invention aims to provide a method for determining the resistance to blooming of paint during automotive painting. This method enables a rapid, intuitive, and accurate laboratory assessment of the resistance to blooming of paint during automotive painting.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention provides a method for determining the resistance to blooming of paint during automotive painting, comprising the following steps:

[0008] A method for determining the resistance to blooming of paint during automotive painting includes the following steps:

[0009] A coating plate is provided, wherein the structure of the coating plate includes: a test plate having a first surface and a second surface correspondingly disposed, and a sealant block cured and bonded to the first surface; the temperature of the sealant block obtained after curing is higher than room temperature, and the heat provided by the sealant block causes the temperature of the area corresponding to the sealant block on the second surface to reach at least the expected temperature.

[0010] The temperature of the area on the second surface corresponding to the sealant block is adjusted to the expected temperature. According to the coating process, automotive paint containing colored paint is applied to at least the area on the second surface corresponding to the sealant block to form a coating.

[0011] The coating's resistance to blooming can be determined by visual observation or by measuring with a cloud meter.

[0012] Furthermore, the paint is a water-based metallic paint.

[0013] Furthermore, the dimensions of the sealant block relative to the test plate are as follows:

[0014] The length of the sealant block is 7 / 9 - 1 of the test plate length;

[0015] The width of the sealant block should be 1 / 3 to 1 / 2 of the width of the test plate;

[0016] The thickness of the sealant block is between 3-5cm.

[0017] Furthermore, the preparation of the coated plate includes the following steps:

[0018] A sealant is applied to the first surface of the test plate and then baked to obtain a coated plate with a sealant block formed on the first surface of the test plate. At this time, the heat provided by the sealant block on the coated plate after baking ensures that the temperature of the area corresponding to the sealant block on the second surface corresponding to the first surface can reach at least the expected temperature.

[0019] Furthermore, the baking temperature is not lower than 160°C, and the baking time is not lower than 20 minutes.

[0020] Furthermore, the method for visually observing the coating's resistance to blooming is: SAE J361: Visual Evaluation Standard for Automotive Interior and Exterior Trim.

[0021] Furthermore, when an automotive paint containing a colored pigment is applied to the entire second surface to form a coating, the method for measuring and determining the coating's resistance to blooming using a cloud meter is as follows:

[0022] The area of ​​the coating surface corresponding to the area on the first surface where the sealant block is provided is designated as the adhesive scraping area.

[0023] The area with a constant temperature in the coating surface area corresponding to the area on the first surface where no sealant block is provided is denoted as the constant temperature zone.

[0024] The area between the glue scraping zone and the constant temperature zone is designated as the gradient cooling zone.

[0025] The SM values ​​of the coating scraping zone, gradient cooling zone, and constant temperature zone were measured using a cloud meter and recorded as SM1, SM2, and SM3, respectively.

[0026] If both |SM3-SM1| and |SM3-SM2| are ≤1, it means that the paint will not cause color blooming during the car painting process; otherwise, it means that the paint will cause color blooming during the car painting process.

[0027] Furthermore, when an automotive paint containing colored pigment is applied only to the area corresponding to the sealant block on the second surface to form a coating, the method for measuring and determining the anti-blooming ability of the coating using a cloud meter is as follows:

[0028] A control test plate is provided, which is made of the same material and has the same dimensions as the test plate.

[0029] Following the same coating process as in claim 1, an automotive paint containing colored paint is applied to one surface of the test panel to form a control coating.

[0030] The SM values ​​of the coating on the glued board and the coating on the test board were measured using a cloud meter and recorded as SM4 and SM5, respectively.

[0031] If |SM4-SM5|≤1, it means that the paint color will not cause color blooming during the car painting process; otherwise, it means that the paint color will cause color blooming during the car painting process.

[0032] Furthermore, the test plate is made of tinplate, steel plate, or plastic plate.

[0033] Furthermore, the plastic sheet is made of PP, ABS, or a mixture of PP and EPDM.

[0034] Furthermore, the method for applying the paint is rotary cup spraying.

[0035] The beneficial effects of this invention are as follows:

[0036] The method provided in this invention studies the effect of temperature on the blooming of automotive paint. By simulating the actual painting process, it solves the problem of temperature control in laboratory simulations, enabling rapid and accurate determination of the paint's resistance to blooming during automotive painting under laboratory conditions. This method bypasses the complex structure of the vehicle body and directly and intuitively displays the blooming state of the paint film, making it simple and easy to implement. Detailed Implementation

[0037] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments, further clarifies the invention. Those skilled in the art should understand that the specific descriptions below are illustrative rather than restrictive, and should not be construed as limiting the scope of protection of the present invention.

[0038] Automotive paints, especially water-based metallic paints, are susceptible to color variations due to temperature differences on the vehicle's body panels during application, leading to coating defects and affecting overall paint quality. This invention addresses this issue by conducting a thorough investigation and analysis of factory painting operations. The investigation revealed that areas where sealant is applied to the inner body panels before the outer panels are painted are particularly prone to color variations. Because the sealant is located on the inner body panels, heat dissipation is poor, causing localized overheating during painting. This affects the flash-drying process, especially in metallic paints where the Bénard vortex is particularly affected by temperature differences, making them more susceptible to color variations.

[0039] To at least address this problem and simulate the process under laboratory conditions, accurately and quickly determining the resistance to blooming of paint during automotive painting, thereby reducing the occurrence of painting defects, this invention provides a method for determining the resistance to blooming of paint during automotive painting. This method allows for flexible setting of parameters during the measurement process, improving the accuracy of the results and facilitating on-site problem solving. Therefore, this measurement method has good application potential, especially in comparing the effect of temperature on the blooming resistance of metallic paints.

[0040] The method specifically includes the following steps:

[0041] 1) Provide a coating plate, wherein the structure of the coating plate includes: a test plate having a first surface and a second surface correspondingly disposed, and a sealant block cured and bonded to the first surface; the temperature of the sealant block obtained after curing is higher than room temperature, and the heat provided by the sealant block causes the temperature of the area corresponding to the sealant block on the second surface to reach at least the expected temperature.

[0042] In this embodiment, the test plate is preferably a clean and smooth material. Exemplary test plates may be made of tinplate, steel, or plastic.

[0043] For example, the plastic sheet is PP, ABS, or a mixture of PP and EPDM.

[0044] The test plate surface can be cleaned before use. For example, it is preferable to wipe the test plate surface clean with a degreasing solvent or alcohol.

[0045] For example, the test plate is rectangular in shape, and its dimensions are, for example, 45cm in length and 30cm in width.

[0046] In this embodiment, the material of the sealant block can be the same sealant used in the coating process on the actual production line, such as edge-folding adhesive.

[0047] The technical solution of this invention mainly considers the influence of temperature on the coating (including flash-drying and baking) of colored paints (especially metallic paints), and uses sealant blocks as a heat source for heat preservation. Its advantages are mainly as follows:

[0048] ① It is easy to make; it can be made according to a fixed length, width and height.

[0049] ② The operation is simple. By controlling the oven temperature and keeping it warm for a very short time (e.g., 20 minutes), you can obtain sealing blocks at different temperatures.

[0050] ③ The sealant block has a longer heat preservation time and the sealant material loses heat more slowly, which can keep the surface temperature of the board stable and uniform during the spraying process, and can more accurately simulate the actual situation.

[0051] ④ In modern coating technology, high-pressure electrostatic spraying is mostly used for paint, and sealant is used as a heat source for insulation. It is not easy to catch fire and is safe and reliable.

[0052] ⑤ The sealing blocks are not easily damaged and can be reused repeatedly without needing to be remade for each test.

[0053] In summary, using sealing blocks for insulation has unique advantages in terms of temperature control, facilitating experiments and ensuring the accuracy of results.

[0054] The dimensions of the sealant block are a crucial factor in controlling the temperature of the test panel. The length, width, and height of the sealant block all need to be controlled. Length and width distinguish the temperature-controlled and non-temperature-controlled areas for subsequent cloud meter testing during result evaluation. Thickness directly affects temperature control; if it's too thin, the temperature control effect will be ineffective. Excessive sealant block thickness will interfere with the coating process, preventing the sealant block from adhering tightly to the coating panel. Conversely, if the sealant block is too thin, the designated insulation area (i.e., the scraping area) will cool down too quickly, failing to reach room temperature by the time the expected temperature is reached, thus hindering temperature control.

[0055] By selecting and controlling the size of the sealing blocks, the stability of temperature control during the experimental testing process can be ensured, thereby accurately testing the effect of temperature on the anti-blooming properties of automotive paint.

[0056] For example, the size of the sealant block relative to the size of the test plate is:

[0057] The length of the sealant block is 7 / 9 - 1 of the test plate length;

[0058] The width of the sealant block should be 1 / 3 to 1 / 2 of the width of the test plate;

[0059] The thickness of the sealant block is between 3-5cm.

[0060] Under these conditions, the sealant block can effectively maintain the temperature, making the test results more accurate.

[0061] For example, when the size of the test plate is 45cm (length) * 30cm (width), the size of the sealant block is preferably 40cm (length) * 10cm (width) * 3cm (thickness).

[0062] In this technical solution, "at least reach the expected temperature" means that the temperature is equal to or higher than the expected temperature.

[0063] In this technical solution, the expected temperature refers to the temperature of the surface of the outer panel corresponding to the sealant position after the inner panel of the car body is coated with sealant at the factory car painting site.

[0064] For example, the preparation of the coated plate includes the following steps:

[0065] A sealant is applied to the first surface and baked to cure, resulting in a coated plate with a sealant block formed on the first surface. At this time, the heat provided by the sealant block after baking ensures that the temperature of the area corresponding to the sealant block on the second surface corresponding to the first surface can reach at least the expected temperature.

[0066] One method for applying sealant to a test panel is by scraping, for example, using a scraper to scrape along one edge of the test panel to form a cuboid block, i.e., a sealant block.

[0067] In this embodiment, after the sealant is applied to the test plate, it is baked for curing. The preferred baking conditions are: a baking temperature not lower than 160°C (e.g., 160°C or 160-200°C), and a baking time not lower than 20 minutes (e.g., 20 minutes). The baking conditions can be determined based on the curing conditions of the sealant material itself.

[0068] 2) Adjust the temperature of the area on the second surface corresponding to the sealant block to the expected temperature, and apply automotive paint containing color paint to at least the area on the second surface corresponding to the sealant block according to the paint coating process to form a coating.

[0069] For example, the method for adjusting the temperature of the area on the second surface corresponding to the sealant block to the desired temperature can be natural cooling. Whether the desired temperature has been reached can be determined by further monitoring the temperature of the area on the second surface corresponding to the sealant block (e.g., using a temperature measuring instrument).

[0070] In some more specific examples, during the preparation of the coated plate, the coated plate (which is a hot plate at this time) obtained after baking can be placed at room temperature for natural cooling until the temperature of the area on the second surface corresponding to the sealant block reaches the expected temperature.

[0071] Based on the actual coating process of the factory's production line, a coating containing color paint is applied to the coating board. For example, in some coating processes, electrophoretic paint and color paint are applied to the test board in sequence, while in others, color paint and clear varnish are applied in sequence. The specific selection of coatings, coating conditions, and process parameters are detailed here based on actual conditions.

[0072] For example, the preferred method for applying paint is rotary cup spraying.

[0073] The paints and other coatings used in this embodiment are all paints used in the actual coating process on the factory production line, and will not be described in detail here. The preferred exemplary paint is a water-based metallic paint.

[0074] In this embodiment, before use, the paint and other coatings are sampled according to the requirements of GB / T 3186-2006, and the matching thinner and curing agent are selected according to the quality control standards to adjust to the coating viscosity. The product is then filtered using a clean filter cloth according to its characteristics.

[0075] In this step, automotive paint containing color can be applied to the entire second surface to form a coating, or automotive paint containing color can be applied only to the area on the second surface corresponding to the sealant block to form a coating.

[0076] 3) Visually observe or use a cloud meter to measure and determine the coating's resistance to blooming.

[0077] In some examples, when visual inspection is used, the method of judgment is SAE J361: Visual Evaluation Standard for Automotive Interior and Exterior Trim. This method is intuitive and can quickly and roughly determine the paint's resistance to blooming based on experience.

[0078] In some other examples, the method for determining the coating's resistance to blooming using a cloud meter is as follows:

[0079] If an automotive paint containing a colored pigment is applied to the entire second surface to form a coating, the method for measuring and determining the coating's resistance to blooming using a cloud meter is as follows:

[0080] The area of ​​the coating surface corresponding to the area on the first surface where the sealant block is set is denoted as the adhesive scraping area.

[0081] The area on the coating surface corresponding to the area on the first surface where no sealant block is provided, and the area with a constant temperature, is denoted as the constant temperature zone.

[0082] The area between the glue scraping zone and the constant temperature zone is designated as the gradient cooling zone.

[0083] The SM values ​​of the coating scraping zone, gradient cooling zone, and constant temperature zone were measured using a cloud meter and recorded as SM1, SM2, and SM3, respectively.

[0084] If both |SM3-SM1| and |SM3-SM2| are ≤1, it means that the paint will not cause color blooming during the car painting process; otherwise, it means that the paint will cause color blooming during the car painting process.

[0085] This method can quickly and objectively determine the coating's resistance to blooming under actual construction conditions (especially temperature).

[0086] In this method, the adhesive-scraping area can be considered as an insulation zone because the sealant block has poor heat dissipation but good insulation properties. The heat it provides ensures that the temperature of the adhesive-scraping area remains essentially the same as the actual field temperature throughout the experiment. It can be understood that the temperature on the second surface radiates outwards from the adhesive-scraping area, resulting in a cooling process. This gradually decreasing temperature region is the gradient cooling zone. After passing through the gradient cooling zone, a constant temperature zone is reached, where the temperature is essentially constant and lower than that of the adhesive-scraping area and the gradient cooling zone.

[0087] If automotive paint containing color is applied only to the area corresponding to the sealant block on the second surface to form a coating, the method for measuring and judging the anti-blooming ability of the coating using a cloud meter is as follows:

[0088] A control test plate is provided, which is made of the same material and has the same dimensions as the test plate.

[0089] Following the same coating process as described above, automotive paint containing colored paint was applied to one surface of the test panel to form a control coating.

[0090] The SM values ​​of the coating on the glued board and the coating on the test board were measured using a cloud meter and recorded as SM4 and SM5, respectively.

[0091] If |SM4-SM5|≤1, it means that the paint color will not cause color blooming during the car painting process; otherwise, it means that the paint color will cause color blooming during the car painting process.

[0092] This method can also accurately determine the coating's resistance to blooming under actual construction conditions (especially temperature).

[0093] The technical solution of the present invention will be described below with reference to specific embodiments:

[0094] Example 1

[0095] A method for determining the anti-blooming ability of a colored paint (metallic paint A (AR-3020-1 1K1)) during automotive painting includes the following steps:

[0096] Provide a tinplate with a length of 45cm and a width of 30cm (as a test plate), clean the tinplate with alcohol, and wipe the surface of the tinplate clean.

[0097] Apply sealant (e.g., edge-folding adhesive) to the first surface of the test board, and use a scraper to spread the sealant along the edge of the board to form a rectangular sealant block with a length of 40cm, a width of 10cm, and a height of 3cm, thus obtaining the adhesive board.

[0098] The prepared rubber sheet is placed in an oven and baked at 160℃ for 20 minutes according to the on-site process. The baked rubber sheet is then removed.

[0099] After baking, the rubber sheet is allowed to cool naturally at room temperature. Simultaneously, the temperature of the area corresponding to the sealing block on the second surface of the rubber sheet (the surface corresponding to the first surface) is measured. When the temperature of this area drops to the expected temperature of 45°C, a coating (color paint, varnish) containing the aforementioned metallic paint A is applied to the entire surface of the second surface of the rubber sheet according to the actual coating process on the factory coating line. The coating method is rotary cup spraying.

[0100] The spraying process requires setting parameters for the spraying robot based on the on-site simulation, including flow rate, rotation speed, forming air (including forming air 1 and forming air 2, i.e., external air shape 1 and internal air shape 2), time, and high voltage (HV), as shown below:

[0101] Paint: AR-3020-1 8X7 Specifications:

[0102] Screw cup diameter: 77mm (ABB);

[0103] Gun distance: 300mm;

[0104] Velocity of fire: 600mm / s;

[0105] Discharge rate: 190cc / min;

[0106] Rotary cup speed: 15000 rpm;

[0107] Forming air: SA1: 380NL / min, SA2: 200NL / min;

[0108] Spraying angle: vertical;

[0109] Voltage: -80kV;

[0110] Film thickness: 15-20μm;

[0111] Leveling angle: horizontal;

[0112] Leveling time: 23±2℃ / 4min;

[0113] Flash-dry angle: horizontal;

[0114] Flash-drying time: 80±5℃ / 30min.

[0115] Clear coat: MAC O-1860 clear coat, specifications:

[0116] Screw cup diameter: 77mm (ABB);

[0117] Gun distance: 200mm;

[0118] Velocity of fire: 600mm / s;

[0119] Discharge rate: 260cc / min;

[0120] Rotary cup speed: 30,000 rpm;

[0121] Forming air: SA1: 420NL / min, SA2: 200NL / min;

[0122] Spraying angle: vertical;

[0123] Voltage: -80kV;

[0124] Film thickness: 30-35μm;

[0125] Leveling angle: horizontal;

[0126] Leveling time: 23±2℃ / 4min;

[0127] Baking angle: horizontal;

[0128] Baking time: 140±5℃ / 30min.

[0129] The area on the second surface of the adhesive sheet that corresponds to the area on the first surface where the sealing adhesive block is located is designated as the adhesive scraping area.

[0130] The area on the second surface of the adhesive sheet that has a constant temperature, corresponding to the area on the first surface where no sealing adhesive block is provided, is denoted as the constant temperature zone.

[0131] The cooling area between the glue scraping area and the constant temperature area on the second surface of the glue sheet is called the gradient cooling area.

[0132] The SM values ​​of the adhesive scraping zone, the gradient cooling zone, and the constant temperature zone were measured using a cloud meter and denoted as SM1, SM2, and SM3, respectively. The specific data are as follows:

[0133] SM1 = 4.8;

[0134] SM2 = 4.9;

[0135] SM3 = 4.9;

[0136] Since both |SM3-SM1| and |SM3-SM2| are ≤1, it indicates that this paint is unlikely to cause color variations during the automotive painting process.

[0137] Based on these results, this paint color was selected, and no related color blooming defects occurred in subsequent paint coating experiments. This method has high accuracy and can be used as a standard in actual production.

[0138] Verify the reproducibility of this method:

[0139] The above method was repeated 5 times. Under the same conditions each time, the SM value of the gradient cooling zone was tested by the cloud and fog instrument. The results are shown in Table 1 below.

[0140] Table 1

[0141]

[0142] As can be seen from Table 1 above, the data on the determination of flowering provided by the present invention are basically consistent and have repeatability.

[0143] In this method, since the sealant block is an insulator, there are no requirements for subsequent spraying methods, etc., which makes it highly safe.

[0144] Example 2

[0145] Following the method described in Example 1 above, the anti-blooming ability of metallic paint B (AR-3020-1 1F7) during the actual coating process was determined.

[0146] The SM values ​​of the adhesive scraping zone, the gradient cooling zone, and the constant temperature zone were measured using a cloud meter and denoted as SM1, SM2, and SM3, respectively. The specific data are as follows:

[0147] SM1 = 6.0;

[0148] SM2 = 6.2;

[0149] SM3 = 6.2;

[0150] Since both |SM3-SM1| and |SM3-SM2| are ≤1, it indicates that this paint is unlikely to cause color variations during the automotive painting process.

[0151] Based on these results, this paint color was selected, and no related color blooming defects occurred in subsequent paint coating experiments. This method has high accuracy and can be used as a standard in actual production.

[0152] Verify the reproducibility of this method:

[0153] The above method was repeated 5 times. Under the same conditions each time, the SM value of the gradient cooling zone was tested by the cloud and fog instrument. The results are shown in Table 2 below.

[0154] Table 2

[0155]

[0156] As can be seen from Table 2 above, the data on the determination of flowering provided by the present invention are basically consistent and have repeatability.

[0157] In this method, since the sealant block is an insulator, there are no requirements for subsequent spraying methods, etc., which makes it highly safe.

[0158] Example 3

[0159] Following the method described in Example 1 above, the anti-blooming ability of metallic paint C (AR-3020-1 1L1) during the actual coating process was determined.

[0160] The SM values ​​of the adhesive scraping zone, the gradient cooling zone, and the constant temperature zone were measured using a cloud meter and denoted as SM1, SM2, and SM3, respectively. The specific data are as follows:

[0161] SM1 = 4.2;

[0162] SM2 = 7.4;

[0163] SM3 = 4.1;

[0164] Since |SM3-SM2|>1, it indicates that this paint is prone to blooming during the automotive painting process.

[0165] Based on these results, no paint was applied, and no related color blooming defects occurred in subsequent paint application experiments. This method has high accuracy and can be used as a standard in actual production.

[0166] Verify the reproducibility of this method:

[0167] The above method was repeated 5 times. Under the same conditions each time, the SM value of the gradient cooling zone was tested by the cloud and fog instrument. The results are shown in Table 2 below.

[0168] Table 3

[0169]

[0170] As can be seen from Table 3 above, the data on the determination of flowering provided by the present invention are basically consistent and have repeatability.

[0171] In this method, since the sealant block is an insulator, there are no requirements for subsequent spraying methods, etc., which makes it highly safe.

[0172] Example 4

[0173] Example 1 is repeated, except that a visual method is used to determine the paint's resistance to blooming during automotive painting. The method is based on SAE J361: Visual Evaluation Standard for Automotive Interior and Exterior Trim, specifically:

[0174] Visual inspection for color variation is a subjective method of color difference detection, relying primarily on human observation and judgment. In visual inspection, it typically requires evaluation by professionals with color vision sensitivity, who determine the color, gloss, and texture of the coating, such as identifying large and small patches.

[0175] 1. Light source requirements: The lighting system must include the following four light sources and meet certain requirements:

[0176] a) D65, color temperature 6500K±200K, illuminance 1080-1730 lux, using halogen lamp filtering technology, spectral power distribution meets the requirements of ASTM E 308 and CIE 51A;

[0177] b) Cool white fluorescent CWF, color temperature 4150K ± 200K, illuminance greater than 860 lux;

[0178] c) Horizontal daylight, color temperature 2300K ± 200K, illuminance greater than 860 lux, simulated by halogen lamps for sunrise and sunset;

[0179] d) Ultraviolet light, which can be used alone or in combination with other light sources, is used to evaluate the effects of whitening agents and fluorescent pigments;

[0180] 2. Environmental requirements:

[0181] The recommended lighting structure has a 30° angle between the light box and the observation platform;

[0182] If the sample is small, with mutual agreement, a standard light source box conforming to the specifications can be used directly for evaluation.

[0183] To prevent the influence of the surrounding environment, the color of the observation platform and the surrounding environment should be Munsell N6-N7 neutral gray, and the saturation C* value should be less than 1. It is best to be in a closed room with no external light. If conditions do not permit, curtains can be used to block the influence of external light. The walls need to be painted with Munsell N6-N7 matte paint, and the color of the curtains should also be as close as possible to N6-N7 gray.

[0184] When evaluating samples, no other items are allowed around the samples; evaluators need to wear gray coats to avoid bright clothing reflecting light and affecting the sample evaluation.

[0185] Samples need to be placed on the evaluation table, centered on the light source. All samples must be placed closely together in the same direction. All samples must be evaluated under sunlight, fluorescence, and horizontal sunlight. Sunlight is the primary evaluation light source, while fluorescence and horizontal sunlight are mainly used to evaluate metamerism. Color judgment must be made immediately, as prolonged viewing will reduce color difference sensitivity. The sample placement angle and observation angle vary depending on the color attribute. For solid colors, two directions are generally observed: face and flap. For special effect colors, such as paint-free products, multi-angle dynamic evaluation (TRAV) is required.

[0186] According to statistical studies, one in 12 men has some form of color vision deficiency, while only one in 255 women has color vision deficiency.

[0187] Therefore, assessors must undergo color blindness testing to exclude individuals with color vision deficiencies; they also need to undergo color sensitivity testing to ensure that assessors have keen color perception.

[0188] When using the method of the present invention, the results of visual judgment are consistent with those of the judgment methods in Examples 1 and 3 above.

[0189] Example 5

[0190] Repeat Example 1, except that when coating the second surface of the adhesive sheet, the coating is only applied to the area on the second surface corresponding to the sealant block.

[0191] A control test plate is also provided, which is made of the same material and has the same dimensions as the test plate.

[0192] Following the same coating process as in Example 1, automotive paint containing colored paint was applied to one surface of the test panel to form a control coating.

[0193] The SM values ​​of the coating on the glued plate and the coating on the test plate were measured using a cloud meter and recorded as SM4 and SM5, respectively. Since |SM4-SM5|<1, the results are consistent with those of Example 1.

[0194] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for determining the resistance to blooming of paint during automotive painting, characterized in that, Includes the following steps: A coating plate is provided, wherein the structure of the coating plate includes: a test plate having a first surface and a second surface correspondingly disposed, and a sealant block cured and bonded to the first surface; the temperature of the sealant block obtained after curing is higher than room temperature, and the heat provided by the sealant block causes the temperature of the area corresponding to the sealant block on the second surface to reach at least the expected temperature. The temperature of the area on the second surface corresponding to the sealant block is adjusted to the expected temperature. According to the coating process, automotive paint containing colored paint is applied to at least the area on the second surface corresponding to the sealant block to form a coating. The coating's resistance to blooming can be determined by visual observation or by measuring with a cloud meter.

2. The method according to claim 1, characterized in that, The paint is a water-based metallic paint.

3. The method according to claim 1, characterized in that, The dimensions of the sealant block relative to the test plate are: The length of the sealant block is 7 / 9 - 1 of the test plate length; The width of the sealant block should be 1 / 3 to 1 / 2 of the width of the test plate; The thickness of the sealant block is between 3-5cm.

4. The method according to claim 1 or 3, characterized in that, The preparation of the coated plate includes the following steps: A sealant is applied to the first surface and baked to obtain a coated plate with a sealant block formed on the first surface. At this time, the heat provided by the sealant block on the coated plate after baking ensures that the temperature of the area corresponding to the sealant block on the second surface corresponding to the first surface can reach at least the expected temperature.

5. The method according to claim 4, characterized in that, The baking temperature is not lower than 160°C and the baking time is not lower than 20 minutes.

6. The method according to claim 1, characterized in that, When an automotive paint containing a colored pigment is applied to the entire second surface to form a coating, the method for measuring and determining the coating's resistance to blooming using a cloud meter is as follows: The area of ​​the coating surface corresponding to the area on the first surface where the sealant block is provided is designated as the adhesive scraping area. The area with a constant temperature in the coating surface area corresponding to the area on the first surface where no sealant block is provided is denoted as the constant temperature zone. The area between the glue scraping zone and the constant temperature zone is designated as the gradient cooling zone. The SM values ​​of the coating scraping zone, gradient cooling zone, and constant temperature zone were measured using a cloud meter and recorded as SM1, SM2, and SM3, respectively. If both |SM3-SM1| and |SM3-SM2| are ≤1, it means that the paint will not cause color blooming during the car painting process; otherwise, it means that the paint will cause color blooming during the car painting process.

7. The method according to claim 1, characterized in that, When an automotive paint containing a colored pigment is applied only to the area corresponding to the sealant block on the second surface to form a coating, the method for measuring and determining the coating's resistance to blooming using a cloud meter is as follows: A control test plate is provided, which is made of the same material and has the same dimensions as the test plate. Following the same coating process as in claim 1, an automotive paint containing colored paint is applied to one surface of the test panel to form a control coating. The SM values ​​of the coating on the coated board and the coating on the test board were measured using a cloud meter and recorded as SM4 and SM5, respectively. If |SM4-SM5|≤1, it means that the paint color will not cause color blooming during the car painting process; otherwise, it means that the paint color will cause color blooming during the car painting process.

8. The method according to claim 1, characterized in that, The test plate is made of tinplate, steel plate or plastic plate.

9. The method according to claim 8, characterized in that, The plastic sheet is made of PP, ABS, or a mixture of PP and EPDM.

10. The method according to claim 1, characterized in that, The method for applying the paint is rotary cup spraying.

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