Development of high-color red metal automotive coatings based on new coating structures.

Jiang Xueying
Source: 2020 Paint Industry No. 9
Automotive has advanced from traditional means of transport to a very common means of styroad, while people's requirements for cars have not been limited to its use value, but also began to pay attention to and pursue its external aesthetics, and automotive coatings is an important means of expressing aesthetics. With the continuous improvement of the public aesthetic, automotive paint color types more and more, some high-color high-metallic products are constantly developed, high-color red products are particularly common (generally defined as L-27-C-10 products for high-color products).
Automotive coatings to provide color effects of the coating is often referred to as primer layer or paint layer, and electrophoresis paint, conductive primer and varnish, such products in the development phase in addition to pay attention to its performance, but also spend a lot of effort to adjust its color, and with the production and application of later products, but also need to arrange for a person to maintain the stability of its colorIn general, plain or monochrome paints are relatively easy to develop and maintain because their color formulations are simple and manageable. And for most metallic paint, because it contains different kinds of effect pigments, so that the color formula ingredients are relatively complex, more difficult to develop, need to consider a comprehensive color pigment and effect pigment type and dosing, only the material used the right to show the desired color effect.
addition, as important as the material selection is the coating structure, for high-color red products, there are currently three conventional coating structures: the first most common, that is, color paint with transparent varnish. This kind of product color is relatively not very high, easy to develop; the second type of color paint with color varnish, this kind of product color color is relatively high, Ford car color design is used more; the third coating structure is similar to the three-coated pearl white products, is made up of color paint BC1 (1st color paint) plain paint plus BC2 (2nd layer paint) metal paint matching CC (transparent varnish). These products not only have a high color, but also make the metal layer more flickering because it is sprayed separately as a coating. In addition to the above three structures, another new spray structure is also beginning to be applied, especially for metal particles more delicate and high color of red products, it can not only meet the higher color difference requirements can also effectively reduce material costs, that is, BC1 aluminum paint plus BC2 transparent red paint with transparent varnish structure. At present, the typical product application is Mazda's soul red, soul crystal red, its high-color high-quality color appearance by consumers alike, and therefore also by many automotive color designers of all ages. Whether this new coating can reduce the cost of materials varies from product to product, most of the application of conventional coating of red metal products, to ensure its high color status, the formulation will use high color and expensive red aluminum or red beads to do the effect, and BC1 using silver powder to provide flicker and product cover, the material price is bound to be reduced.
this paper has developed the color of known high-color red products by using the coating structure of silver powder paint/transparent red paint with transparent varnish, and discusses the influence of its construction film thickness on color.
1 Experimental part
1.1 main raw materials
resin substrate,red pulp, DPP (doxone and pyridine) organic red slurry, maroon 179 color paste, color control agent, matching primer and varnish: Asda; butyl acetate: BASF; xylene: Jinzhou Petrochemical; aluminum powder a, aluminum powder b: Dongyang.
1.2 paint preparation
in accordance with table 1 formula premixed and dispersed preparation paint, to be dispersed evenly, in accordance with Table 2 conditions after debugging the paint to the construction state left for spraying.
1.3 spraying equipment and parameters set
According to the site construction information feedback, the color is sprayed with a cup and gun, BC1 film thickness of more than 20 m, BC2 film thickness of up to 15 m or more, so the laboratory according to the accumulation of spray data on the site in the past, set the construction spraying parameters shown in Table 3.
table 3 paint spray construction parameters
1.4 color test
from the customer to obtain the red product's digital standard see table 4, color difference measurement instrument BYKmac-i. Color development needs to meet 3 angles of the E at the same time within the required range, that is, 25 degrees E 3, 45 degrees E 2, 75 degrees E 2, and there can be no significant difference in visual. E is a data control standard used by many customers to determine whether the color difference of automotive coatings is qualified or not, and its calculation formula is as shown in formula (1):
When the smaller the color E, the closer the model is to the standard board, and the more deviate from the standard, it is necessary to reduce the composite value of the value of the standard by reducing the color difference of the color difference of the car, the higher the value of the value of the red product, so the value of the value of the value of the value of the value of the value of the value of the value of the value of the value of the value of the value of the value of the value of the value of the value of the value of the value of the value of the value of the value of the value of the value will be relatively high.
Table 4 Product Digital Standard
1.5 Black and White Block Cover Test
During the color development process, when the composition of the formula is determined, the black and white masking force of the BC1 and BC2 layers is examined to determine the masking capacity of each color paint coating. The better the black-and-white lamination cover of the color lacquer layer, the higher the stability of the entire color, and the monitoring of this indicator during the color development process, thus guiding the formulation to make effective adjustments. The experiment is sprayed with a hand-spray gun (ANESTIWATAW-17), which is observed by the sprayer while spraying, and the film thickness gradient is pulled apart and there is a clear cover limit.
2 Results and discussion
2.1 effect pigment selection
effect pigments including pearl powder, aluminum powder and glass powder. The red standard plate provided by the customer was analyzed, the size, shape and color of the particles were observed under a microscope and spotlight, the material type was identified as aluminum powder, and two different particle distributions were observed, all of which were silver particles, with the D50 around 25 m and 12 m, respectively. In addition, through the measurement of color data, the FlopIndex (FI, reflecting the difference in the L-value of the positive side of the aluminum powder, the larger the FI, the greater the difference in the brightness of the positive side of the aluminum powder), and further narrow the material selection range. The effect pigment involved in this experiment is aluminum powder, aluminum powder from the shape of the division can be divided into cornflakes and silver meta-type (Figure 1), corn flake aluminum powder under the microscope to observe the edge is jagged and irregular, after the film aluminum powder is arranged in the coating also It seems very irregular, at the same time because of its multi-edge effect, its visual flicker is stronger, and silver-type aluminum powder under the microscope to observe the edge regulation smooth, aluminum powder layer arrangement is relatively dense and flat, so it has a strong metal sense and cover effect. The above analysis of this experiment is precisely through the microscopic shape and the approximate size of the observation, to determine the scope of aluminum powder selection, the preliminary selection of 2 aluminum powder, respectively, aluminum powder a, aluminum powder b.
figure 1 50 times microscope to observe the aluminum powder status
2.2 color pigment selection
color pigments are often used in the form of color paste, it includes inorganic and organic two categories, these materials in the paint mainly provide color effect. Inorganic material after grinding color paste is suspended scattered in the resin, the material is more stable, and has a better masking, in the color of plain paint in the application of more. Organic materials can be dissolved well in coating resins and solvent systems, with which the grinding of the slurry not only has a good dispersion, but also has a high transparency, in the metal paint color has more applications. Experiments on the customer's standard plate analysis, found that the product's color slurry is mainly concentrated in the BC2 coating, the layer mainly provides high color, and it can not have too strong cover, otherwise it will press the BC1 layer of aluminum powder particle effect, so it is necessary to choose a higher transparency of the color paste. At the same time, from the chroma data, the color yellow is higher than, so the selected color paste needs a slightly yellow red slurry. This kind of color paste is generally mainly organic red pulp, such as DPP red,red, chestnut red and so on. Experiments first selected a red pulp main pulp (red pulp 1), with the addition of a DPP red pulp (red pulp 2), BC1 layer of red pulp used for maroon 179 color pulp (red pulp 3)
2.3 formula determination and color data signs
After the box is removed and placed at room temperature, the BYKmac-i chromatometer is used for data measurement, and the standard board is compared to do visual observation, to find the difference point (particle status, phase), after many experiments repeatedly adjusted the formula, get satisfactory visual and data effect, the final formula as shown in Table 5, its corresponding chroma data as shown in Table 6.
effect of 2.4-color paint film thickness on color
the black-and-white cover of the BC1 and BC2 coatings was first tested, and the results are shown in Figure 2.
black-and-white block cover for BC1 and BC2 coatings
as can be seen from Figure 2, BC1 achieves full cover at 12 m, while BC2 has a black-and-white grid cover force of more than 50 m. This shows that the entire paint coating cover force can reach at least 12 m, strong construction, on the other hand, BC2 individual covering force of more than 50 m, it can be seen that BC2 transparency is very good, can effectively enhance the color color without covering the lower metal texture.
addition, in order to investigate the influence of film thickness on the color of this type of coating, 2 sets of gradient film thickness experiments were set: the first group of experimental BC2 spray film thickness was set at about 15 m, BC1 film thickness to do gradient spraying, from 5 to 20 m variation; BC1 spray film thickness is set at about 15 m, BC2 film thickness to do gradient spraying, from 7 to 20 m changes, and then collect schrome data, to investigate the value of L, a, b, with the change of film thickness, the results are shown in Figure 3.
3 L, a, b, with BC1, BC2 film thickness changes
as can be seen from Figure 3, with the increase of BC1 film thickness, 15 degrees, 25 degrees of Xenon L, The first increase is raised, and then at 12 m, until it stabilizes at 17 m, another inflection point occurs at 18 m, the data decreases, and the stability stabilizes at 18 to 20 m. This trend of change is due to the color of the black-and-white grid cover at 12 m, reached the black-and-white grid cover after the data tend to stabilize, after the film thickness further increased, BC1 layer of silver powder has accumulated, can not be effectively directed, resulting in 15 degrees, 25 degrees of the S-L and a-a-somewhat fluctuating. However, the increase of 45 degrees, 75 degrees, 110 degrees of L, a, and b, gradually increased with the increase of film thickness, and the data gradually stabilized. When the BC1 film thickness is fixed, and the change of chroma data with the increase of BC2 film thickness can be observed, it can be found that the data fluctuations are 15 degrees, 25 degrees of xenon L, xenon a, and xenon b, and BC2 membrane thickness negative relationship, analysis is due to the increase of BC2 film thickness, BC2 and BC1 interaction between stronger, BC1 layer aluminum powder orientation is caused by interference. At the same time, the 45-degree, 75-degree, 110-degree l', 'a' and 'b' are relatively stable, because this part of the data is more affected by the slurry, while the BC2 layer cover force is very poor, the increase in film thickness in this range will not lead to a significant change in the large angle color difference. The change trend of the above data can effectively guide the film thickness control of the product in the actual construction.
3 Conclusion
In summary, metal paint in the coloring process, the effective selection of materials is very important, whether it is coloring pigments or effect pigments, to match each other in order to combine the ideal color difference data and color effect. At the same time, for high-color red products, finding the right coating structure is also the key to the correct expression of color. In this paper, the use of silver powder paint / transparent red paint with transparent varnish new coating structure to develop high-color red automotive paint research, not only make us the color of the mass production stability control has a certain amount of data accumulation, but also for the subsequent development of similar colors will also play an important reference significance.
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