Technological treatment method for improving facade long-short wave inversion after single-color paint recoating

Abstract

The invention provides a process treatment method for improving facade long and short wave inversion after single-color paint recoating. According to the process treatment method, it is clear that single-color paint with inverted long and short waves appears after recoating, process adjustment is conducted on the single-color paint, and the process adjustment comprises a finish paint pulping process and a finish paint recoating process; the finishing paint pulping process comprises the following steps: adding the raw material components of the single-color paint according to the formula ratio, and adding pearl powder to obtain slurry; the finishing paint recoating process comprises the step of spraying the obtained slurry on a substrate containing varnish; the pearl powder is selected from gray pearl powder or white pearl powder. Corresponding pearl powder is added in a finishing paint pulping process, so that the problem that long waves and short waves of a vertical surface are inverted after single-color paint is recoated can be effectively solved on the premise of not changing conventional spraying process parameters, and the overall visual appearance of a paint film is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of coatings, and specifically comprises a process for improving the inversion of long and short waves of a facade after repainting with a single-color paint. Background Art

[0002] L w (Long wave), S w (Short wave) and DOI (distinctness of image) are commonly used evaluation indicators for the appearance of automotive paint films. The long wave value is often smaller than the short wave value, and there is a certain ratio requirement between the two. It is generally believed that the long wave value should be 1 / 3-1 / 2 of the short wave value, so as not to affect the visual appearance (that is, the ratio of the short wave value to the long wave value is 2-3), and the smaller the long wave value and the short wave value, the better. However, in the actual production process, sometimes the long wave value is close to the short wave value, or even the long wave value is greater than the short wave value. This is the "long and short wave inversion" phenomenon.

[0003] The general understanding of the automotive coatings industry on the problem of long- and short-wave inversion is: 1) The problem of long- and short-wave inversion often occurs in single-color paints and pearlescent paints with smaller pigment particle sizes, while this problem does not exist in automotive paint film colors such as brown, red, pearlescent white, and silver; 2) The vertical area of ​​the car (such as fenders and doors) is prone to the problem of long- and short-wave inversion, while the flat area of ​​the car does not have the problem of long- and short-wave inversion; 3) The inversion of long- and short-waves is often greatly affected by the substrate. The normal coating process is electrophoresis + mid-coat + color paint + clear coat. Because of the influence of electrophoresis roughness, long- and short-wave inversion generally does not occur. However, if recoating occurs, the substrate during recoating becomes the clear coat layer. The flatness of the clear coat layer is much better than that of the electrophoretic substrate, and long- and short-wave inversion is more likely to occur. At present, technicians have the following solutions to solve the problem of long-short wave inversion: If the problem of long-short wave inversion occurs in the coating development stage or the whole vehicle assembly line painting, it can usually be solved by increasing the thickness of the intermediate coating or the clear coating, improving the wettability of the coating, extending the leveling time, grinding, etc. If the recoating is performed on the complete paint film, the only way to reduce the surface gloss of the paint film and increase the short wave value is to grind it. However, this treatment method greatly increases the labor cost and time cost, and is inefficient. Therefore, it is urgent to develop a more efficient process treatment method to solve the problem of long-short wave inversion after recoating of single-color paint. Summary of the invention

[0004] In view of the above problems existing in the prior art, the purpose of the present invention is to provide a process treatment method for improving the inversion of long and short waves on the facade after repainting with single-color paint. By adding pearlescent powder in the pulping process of the topcoat, the inversion problem of long and short waves on the facade repainted with single-color paint can be effectively improved without changing the conventional spraying process parameters.

[0005] Monochrome paint, also known as solid color paint, is a color paint that is consistent in color at all visual angles and does not have any flicker. It should be noted first that the technical solution of the present invention is an improved method for those that need to re-coat monochrome paint outside the varnish, and the problem of long and short wave inversion will occur after re-coating monochrome paint. The "facade" in the present invention is a professional term in the field of automotive coatings, referring to the area of ​​the automobile body set at an angle of 70-120°, such as fenders, doors, etc., or the base material placed at an angle of 70-120° during small test spraying.

[0006] To achieve the above object, the technical solution adopted by the present invention includes:

[0007] The invention discloses a process treatment method for improving the inversion of long and short waves on a facade after recoating of a single-color paint, identifying the single-color paint with inversion of long and short waves after recoating, and adjusting the process thereof, including a topcoat pulping process and a topcoat recoating process;

[0008] The topcoat slurry making process is to add various raw material components of the single-color paint according to the formula amount, and add pearl powder to obtain slurry;

[0009] The topcoat recoating process is to spray the obtained slurry on a substrate containing varnish;

[0010] The pearlescent powder is selected from gray pearlescent powder or white pearlescent powder.

[0011] Furthermore, the added amount of the pearlescent powder is 0.3-1wt% of the single-color paint, and the particle size distribution range of the pearlescent powder is 5-40μm.

[0012] Furthermore, the monochromatic paint comprises the following raw material components in parts by weight:

[0013] Polyurethane emulsion 13-18 parts;

[0014] 3-4.5 parts of polyester resin;

[0015] Acrylic emulsion 23-30 parts;

[0016] 6-8.5 parts of amino resin;

[0017] Color paste 17-33 parts;

[0018] 3-4.5 parts of additives;

[0019] 15-20 parts of solvent.

[0020] Furthermore, at the brightness L w Gray pearl powder is added to the single-color paint with brightness L w White pearlescent powder is added to the single-color paint with a value of ≥50.

[0021] Further, the specific steps of the topcoat pulping process are:

[0022] Mix the raw materials of the single-color paint evenly according to the formula, adjust to the construction viscosity, then add pearl powder, stir evenly to obtain slurry; or

[0023] The raw materials of the single-color paint and the pearlescent powder are uniformly mixed according to the formula amount, and adjusted to the construction viscosity to obtain a slurry.

[0024] Further, the specific steps of the topcoat recoating process are:

[0025] The obtained slurry is sprayed on the substrate containing varnish to recoat the topcoat layer. After pre-baking, 2K varnish is sprayed and then baked to complete the topcoat recoating process.

[0026] Furthermore, the sprayed topcoat film thickness is 14-18 μm and the leveling time is 3-5 min.

[0027] Furthermore, the sprayed 2K varnish has a film thickness of 50-60 μm and a leveling time of 7-10 min.

[0028] Furthermore, the pre-baking temperature is 80-90° C., and the pre-baking time is 7-10 min.

[0029] Furthermore, the baking condition is baking at 140-160° C. for 20-30 min.

[0030] Beneficial effects of the present invention:

[0031] The present invention provides a process treatment method for improving the problem of inverted long and short waves on a facade after recoating with a single-color paint. By adding corresponding pearlescent powder at any stage of paint preparation, the problem of inverted long and short waves on a facade after recoating with a single-color paint can be effectively solved, and the overall visual appearance of the paint film can be improved. There is no need to adjust the original spraying process parameters. Compared with various solutions disclosed in the prior art (such as increasing the thickness of the intermediate coating or the clear coating, improving the wettability of the coating, extending the leveling time, polishing, etc.), the method is more efficient. DETAILED DESCRIPTION

[0032] In order to explain the present invention more clearly, the present invention is further described below in conjunction with preferred embodiments. It should be clear that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] In the case of illustrating and explaining the purpose of the present invention through the following examples, the components of the composition are explained in parts by weight as a general standard. Unless otherwise specified, for the sake of simplicity, the "parts" described in the examples of the present invention have the same meaning as parts by weight.

[0034] In order to meet people's demand for adding patterns on the paint film of color-matching vehicles or car bodies, it is usually repainted on the basis of the original paint film. However, since the base material becomes a varnish layer during repainting, the flatness of the varnish layer is much better than that of the electrophoretic base material, so it is more likely to have long and short wave inversion. In the reports disclosed in the prior art, in order to effectively solve the problem of long and short wave inversion of the facade after repainting of single-color paint, the surface gloss of the paint film is usually reduced by grinding the varnish layer to achieve the purpose of solving the problem of long and short wave inversion. The labor cost and time cost are high, and the efficiency is low. For this reason, the present invention is aimed at those single-color paints that need to be repainted with single-color paint outside the varnish and will have the problem of long and short wave inversion after repainting the single-color paint. The process is improved, including a topcoat pulping process and a topcoat repainting process. The core technology is to add pearl powder in any stage of the coating preparation to improve the long and short waves. The specific steps are:

[0035] Solution 1

[0036] Identify the single-color paint formula that has the problem of inverted long and short waves on the facade after repainting, then add the required raw material components (including film-forming resin, color paste, additives, solvents, etc.) according to the formula amount, mix evenly, adjust the pH value and viscosity, then add pearl powder, mix again until uniform, and obtain slurry;

[0037] The obtained slurry is sprayed on a substrate containing varnish to obtain a recoating topcoat layer, and 2K varnish is sprayed after pre-baking, and then baked to complete the topcoat recoating process.

[0038] Solution 2

[0039] The formula of the single-color paint with the problem of inverted long and short waves on the facade after repainting is clarified, and then the required raw material components (including film-forming resin, color paste, additives, solvents, etc.) and pearlescent powder are added according to the formula amount, and after mixing evenly, the pH value and viscosity are adjusted to obtain a slurry;

[0040] The obtained slurry is sprayed on a substrate containing varnish to obtain a recoating topcoat layer, and 2K varnish is sprayed after pre-baking, and then baked to complete the topcoat recoating process.

[0041] The only difference between the two schemes is the timing of adding pearlescent powder. Pearlescent powder can be added at any stage of mixing single-color paint. It can be added after adjusting the pH value and viscosity as in scheme one, or it can be mixed evenly with the raw materials of single-color paint at the beginning of mixing, and then adjusting the pH value and viscosity as in scheme two.

[0042] The technicians can understand that the topcoat recoating process of the present invention is only a spraying process disclosed as an example. The technicians can also spray a layer of mid-coat of any one of the processes 3C1B1PH, 3C1B2PH or 3C2B on the substrate containing the varnish according to the actual situation, and then spray the topcoat and varnish in turn. This will also improve the problem of inversion of long and short waves on the facade. In other words, the specific topcoat recoating process is not limited, as long as the obtained slurry is sprayed on the substrate of the original varnish.

[0043] Due to the difference in the base materials used to make pearlescent powder, pearlescent powder can be roughly divided into glass pearlescent powder that can provide a strong visual flickering feeling and ordinary pearlescent powder without visual flickering feeling. Glass pearlescent powder has sharper edges and corners because its main base material is glass, so the visual flickering feeling is stronger, while the main base material of ordinary pearlescent powder is generally natural mica or synthetic mica, and the shape is flatter and without edges and corners, so there is no visual flickering feeling. In solving the problem of inversion of the vertical long and short waves of monochrome paint, it should be ensured that the visual color of monochrome paint does not change, so it can be understood by those skilled in the art that the pearlescent powder described in the present invention refers to ordinary pearlescent powder rather than glass pearlescent powder. Once glass pearlescent powder is added to monochrome paint, it no longer belongs to the category of monochrome paint, and the visual color will change. In addition, the present invention has no requirements for the source of pearlescent powder. Both natural pearlescent powder and synthetic pearlescent powder can be selected. The main focus is on the amount of pearlescent powder, the particle size distribution of pearlescent powder, and the matching of pearlescent powder with the color of monochrome paint. In a specific embodiment, the amount of the pearlescent powder added is 0.3-1wt% of the single-color paint. If the amount of the pearlescent powder added is too high, it will cause a flickering effect in visual observation, and too little addition will not improve the effect of long-short wave inversion. In a specific embodiment, the particle size of the pearlescent powder needs to be distributed in a small particle size (≥5μm and <10μm), a medium particle size (≥10μm and <30μm), and a large particle size (≥30μm and ≤40μm). For example, the particle size distribution range of the pearlescent powder can be 5-40μm, 9-35μm, 6-40μm, 5-30μm, etc., and cannot be distributed only in a small particle size, a medium particle size, or a large particle size, such as 5-9μm, 5-20μm, 10-25μm, 15-35μm, 30-40μm, etc. If the particle size distribution range exceeds the upper limit or is close to the large particle size, the larger particle size of the pearlescent powder will cause a flickering effect in visual observation. If the particle size distribution range is lower than the lower limit or is close to the small particle size, the smaller particle size of the pearlescent powder will not improve the effect of long-short wave inversion.

[0044] It should be noted that there is also a solution of adding pearlescent powder to single-color paint in the prior art, but its purpose is to achieve a certain color and flashing visual effect, and does not involve the repainting process, nor does it pay attention to the problem of long and short wave inversion that may exist on the facade after repainting of single-color paint. In the present invention, 0.3-1wt% of pearlescent powder is added to the single-color paint in order to improve the phenomenon of long and short wave inversion in the case of repainting without changing the color characteristics of the single-color paint.

[0045] Further, the pearlescent powder is selected from gray pearlescent powder or white pearlescent powder; illustratively, in the brightness L w Gray pearl powder is added to the single-color paint with brightness L w White pearlescent powder is added to the single-color paint with a value of ≥50.

[0046] Furthermore, the white pearlescent powder is selected from CQV AK-909K-OP (particle size distribution range is 9-35 μm) and / or Merck T60-10 (particle size distribution range is 5-30 μm); the gray pearlescent powder is selected from Merck 9602 (particle size distribution range 5-40 μm) and / or Merck 602WNT (particle size distribution range is 5-40μm).

[0047] Furthermore, in Scheme 1 and Scheme 2, the sprayed topcoat film thickness is 14-18 μm, preferably 16 μm, and the leveling time is 3-5 min, preferably 3 min; the sprayed 2K clearcoat film thickness is 50-60 μm, preferably 55 μm, and the leveling time is 7-10 min, preferably 7 min.

[0048] Furthermore, the present invention does not strictly limit the single-color paint formula, and provides a solution to improve the problem of long and short wave inversion of the facade after repainting of single-color paint under various single-color paint formulas, which is independent of the single-color paint formula. Therefore, the present invention takes a conventional formula in the field as an example to further illustrate, and the formula comprises the following raw material components in parts by mass:

[0049] Polyurethane emulsion 13-18 parts;

[0050] 3-4.5 parts of polyester resin;

[0051] Acrylic emulsion 23-30 parts;

[0052] 6-8.5 parts of amino resin;

[0053] Color paste 17-33 parts;

[0054] 3-4.5 parts of additives;

[0055] 15-20 parts of solvent.

[0056] Further, the polyurethane emulsion is selected from DAOTAN STW 6434 / 40WA, One or more of TW 6464 / 36WA, DAOTAN TW 6431 / 45WA.

[0057] Furthermore, the polyester resin is selected from SETAL 6306SS-60 and / or SETAQUA 6407.

[0058] Furthermore, the acrylic emulsion is selected from one or more of SETAQUA6801, Setaqua 6802, and Setaqua 6803.

[0059] Furthermore, the amino resin is selected from one or more of CYMEL 303LF, LUWIPAL 072, and LUWIPAL 069.

[0060] Furthermore, the color paste is selected from AR 2000(T)MAPICO YELLOW yellow paste, AR-2000(T)343MAGENTA17% color paste, AR-2000(T)6520BLUE UDP blue, AR-2000(T)ANCHOR RED UDP 24% color paste, AR-2000(T)BLACK W / O RESIN color paste, AR-2000(T)WHITE(W / O), NAPER WF L6210 blue color paste, etc.

[0061] Furthermore, the auxiliary agent includes pH regulators such as dimethylethanolamine and AMP-95, defoamers such as SURFYNOL 104PE and BYK-015, wetting agents such as TEGO Wet 505 and DYNOL 607, and thickeners such as HV30 and RHEOVIS AS1130.

[0062] Furthermore, the solvent comprises 4-6 parts of water and 10-14 parts of an organic solvent.

[0063] The present invention only takes the above single-color paint formula as an example to illustrate the contribution of pearlescent powder in improving the problem of long-short wave inversion on the facade after re-coating of single-color paint. Those skilled in the art can understand that as long as other single-color paints have the problem of long-short wave inversion, the problem of long-short wave inversion can be effectively solved by appropriate adjustment using the method of the present invention. Therefore, the single-color paint formulas are not listed one by one for proof, and they are all within the protection scope of the present invention.

[0064] The invention will be further described below through specific embodiments.

[0065] Example 1

[0066] This embodiment provides a single-color paint (gray) formula with inverted long and short waves and an adjusted paint formula with gray pearlescent added to the single-color paint formula, see Table 1.

[0067] Table 1

[0068]

[0069] Topcoat pulping process: add polyurethane emulsion, polyester resin, acrylic emulsion, amino resin, alkaline thickener, defoamer, wetting agent, organic solvent, various color pastes, water, pH adjuster in sequence under stirring conditions, and adjust to 160-200mPa.s (R-180 viscometer 23℃ 250s -1 ) and pH = 8.2-8.6, a single-color paint slurry is obtained. If the paint slurry is prepared for adjustment, gray pearl powder needs to be added after adjusting to the target viscosity and pH.

[0070] Topcoat recoating process: the obtained single-color paint slurry or adjusted paint slurry is sprayed on the substrate sprayed with varnish (the varnish film thickness is 55 μm), the topcoat film thickness is 16 μm, after leveling for 3 minutes, pre-bake at 85°C for 8 minutes, spray 2K varnish after pre-bake, the varnish film thickness is 55 μm, after leveling for 7 minutes, bake at 145°C for 25 minutes to complete the entire recoating process. The results are shown in Table 3.

[0071] Comparative Example 1

[0072] This comparative example provides an adjusted paint formula with the addition of aluminum powder, see Table 2.

[0073] Table 2

[0074]

[0075] Topcoat pulping process: add polyurethane emulsion, polyester resin, acrylic emulsion, amino resin, alkaline thickener, defoamer, wetting agent, organic solvent, various color pastes, water, pH adjuster in sequence under stirring conditions, and adjust to 160-200mPa.s (R-180 viscometer 23℃ 250s -1 ) and pH = 8.2-8.6, add aluminum powder to obtain adjusted paint slurry.

[0076] Topcoat recoating process: The adjusted paint slurry is sprayed on the substrate sprayed with varnish (the varnish film thickness is 55μm), the topcoat film thickness is 16μm, and after leveling for 3min, it is pre-baked at 85℃ for 8min. After pre-baking, 2K varnish is sprayed, and the varnish film thickness is 55μm. After leveling for 7min, it is baked at 145℃ for 25min to complete the entire recoating process. The results are shown in Table 3.

[0077] Table 3

[0078]

[0079]

[0080] Example 2

[0081] This embodiment provides a single-color paint (beige) formula with inverted long and short waves and an adjusted paint formula with white pearlescent added to the single-color paint formula, see Table 4.

[0082] Table 4

[0083]

[0084] The topcoat pulping process and topcoat recoating process are the same as those in Example 1. The properties of the resulting paint film are shown in Table 6.

[0085] Comparative Examples 2-6

[0086] This comparative example provides the following five adjusted paint formulations, see Table 5.

[0087] Table 5

[0088]

[0089] The topcoat pulping process and topcoat recoating process are the same as those in Example 1. The properties of the resulting paint film are shown in Table 6.

[0090] Table 6

[0091]

[0092]

[0093] Example 3

[0094] This embodiment provides a single-color paint (beige) formula with inverted long and short waves and an adjusted paint formula with white pearlescent added to the single-color paint formula, see Table 7.

[0095] Table 7

[0096]

[0097]

[0098] The topcoat pulping process and topcoat recoating process are the same as those in Example 1. The properties of the resulting paint film are shown in Table 8.

[0099] Table 8

[0100]

[0101] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A process for improving the inversion of long and short waves on a facade after repainting with a single-color paint. It is characterized in that Identify the single-color paint that has inverted long and short waves after recoating, and adjust its process, including the topcoat pulping process and the topcoat recoating process; The topcoat slurry making process is to add various raw material components of the single-color paint according to the formula amount, and add pearl powder to obtain slurry; The topcoat recoating process is to spray the obtained slurry on a substrate containing varnish; The pearlescent powder is selected from gray pearlescent powder or white pearlescent powder.

2. The process according to claim 1, It is characterized in that The added amount of the pearlescent powder is 0.3-1wt% of the single-color paint, and the particle size distribution range of the pearlescent powder is 5-40μm.

3. The process according to claim 1, It is characterized in that The monochromatic paint comprises the following raw material components in parts by weight: Polyurethane emulsion 13-18 parts; 3-4.5 parts of polyester resin; Acrylic emulsion 23-30 parts; 6-8.5 parts of amino resin; Color paste 17-33 parts; 3-4.5 parts of additives; 15-20 parts of solvent.

4. The process according to claim 1, It is characterized in that At brightness L w Gray pearl powder is added to the single-color paint with brightness L w White pearlescent powder is added to the single-color paint with a value of ≥50.

5. The process according to claim 1, It is characterized in that The specific steps of the topcoat pulping process are: Mix the raw materials of the single-color paint evenly according to the formula, adjust to the construction viscosity, then add pearl powder, stir evenly to obtain slurry; or The raw materials of the single-color paint and the pearlescent powder are uniformly mixed according to the formula amount, and adjusted to the construction viscosity to obtain a slurry.

6. The process according to claim 1, It is characterized in that The specific steps of the topcoat recoating process are: The obtained slurry is sprayed on the substrate containing varnish to recoat the topcoat layer. After pre-baking, 2K varnish is sprayed and then baked to complete the topcoat recoating process.

7. The process according to claim 6, It is characterized in that The sprayed topcoat film thickness is 14-18μm and leveling takes 3-5min.

8. The process according to claim 1 or 6, It is characterized in that The sprayed 2K varnish has a film thickness of 50-60μm and a leveling time of 7-10min.

9. The process according to claim 6, It is characterized in that The pre-baking temperature is 80-90° C., and the pre-baking time is 7-10 min.

10. The process according to claim 6, It is characterized in that The baking condition is baking at 140-160° C. for 20-30 minutes.

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