Basic knowledge of color mixing——Basic paint and color paste
1. Basic paint
The so-called base paint, simply put, is the white paint or varnish (pigments that do not contain hiding power) produced by the paint company itself. The base paint is the carrier of color mixing. The control of the base paint during the color mixing process will affect all aspects of color mixing accuracy, reproducibility, compatibility, economy and color gamut coverage. At the same time, the base paint is the only part of the integrated color mixing system in the factory and store that is prepared by the paint company itself. Therefore, different base paints make significant differences in the use and effect of the color mixing system. Base paints vary greatly due to their different formulas and application ranges. In order to improve the matching of the manufacturer’s base paints when used in the integrated color mixing system and give full play to the system’s advantages, the base paints need to be adjusted.
(1) The impact of batch color difference of base paint on the color mixing system
If the base paint produced by the company is in different batches, there will be coloring differences between the base paints in each batch. These color differences will cause large deviations in the color mixing results. Experiments have proven that due to a comprehensive analysis of the color mixing results of different batches of base paint, the color difference of the base paint needs to be controlled below 0.3, which will affect the final results of the color mixing system. will be smaller.
(2) The impact of the compatibility of base paint and color paste on the final result of the color mixing system
The compatibility of the base paint and the base paint affects the accuracy and economy of color mixing. The compatibility can be seen through finger grinding tests and the method of mixing the base paint with the base paint and then letting it sit for a long time.
The so-called finger grinding test is to take 100 g of white paint, add 2 to 3 g of the color paste to be tested, stir thoroughly, and apply it on the surface of the object to be coated. When the paint film is almost dry, grind the coating film with your fingers. For the surface part, after the paint film is completely dry, observe whether there is a color difference between the areas that have been rubbed with your fingers and those that have not been rubbed. If the difference is large, the compatibility between the color paste and the paint being tested is not good. Use this color The paint mixed with slurry is prone to floating color. If the colors are the same, there will generally be no floating color phenomenon.
Experiments have proven that when the compatibility finger color difference is below 0.5, the accuracy and economic impact on the final result of color mixing will be small.
The method of mixing the color paste and the base paint and letting it sit is to add the selected color paste to the base paint, stir and mix, and let it stand for 24 hours to observe whether there is floating color (pigment delamination). If pigment delamination occurs, it means that the color paste used is not compatible with the base paint.
(3) The impact of the division of titanium dioxide content in base paint on the color matching system
The division of titanium dioxide content in base paints is mainly based on the color gamut requirements and economic requirements of color mixing, as well as the covering power requirements of coatings and the impact of the maximum amount of colorant added on coating performance. A reasonable division can only be made after comprehensive consideration of these factors.
There are many ways to divide titanium dioxide content in base paints that can meet color gamut coverage and economy. Currently, there are 4 kinds of base paint systems with titanium dioxide content and 2 kinds of base paint systems with titanium dioxide content. However, after comprehensive consideration of economics, color mixing costs, inventory savings and other comprehensive factors as well as the market’s demand for color, it is possible to determine how many types of titanium dioxide content the basic paint system is divided into based on the actual situation of the company. For example, the base paint of a certain system is divided into three types of titanium dioxide content: paint A has a titanium dioxide content of 18% to 23%, paint B has a titanium dioxide content of 7% to 13%, and paint C has a titanium dioxide content of 0.
(4) Performance indicators of base paint
In order to obtain a satisfactory final color mixing result and make the impact of the base paint on the color mixing result to a level acceptable to the customer, the requirements for the performance indicators of the base paint,
2. Color paste
The color paste mentioned here mainly refers to water-based color paste. Water-based color paste refers to the uniform and stable formation of organic or inorganic pigments under the wetting and dispersing effects of surfactants (water-soluble resins can also be added), with certain fluidity or thixotropic fluidity, and relatively high Concentrated pigment slurry with high tinting strength. There are two types of water-based color paste systems: one is a resin-free system with high pigment content; the other is a resin (general-purpose resin, other single resin) system with low pigment content. �The former has high pigment concentration, strong tinting power, good color development performance, good compatibility, and thixotropic fluidity. It generally does not cause color floating and blooming. The selection of additives is reasonable and has versatility. The pigment concentration of the latter is relatively low, but it has good tinting power, good color development, and relatively stable fluidity and viscosity. This system contains resin, and the compatibility needs to be tested, otherwise it will easily cause the paint to float or bloom. . The color mixing of oil-based paint generally uses pigment slurry ground by the company itself.
(1) The requirements of the color mixing system on the color paste and the impact of the color paste on the system
As a coloring body, color paste affects all system performance such as color accuracy, reproducibility, compatibility, economy and color gamut coverage in integrated color mixing.
As an integrated tinting paste, it has higher requirements in terms of physical and chemical indicators, mainly in the viscosity and drying speed of the tinting paste. It needs to have good adaptability to the tinting equipment and meet the equipment requirements. . In addition, there are stricter requirements for the batch stability of color pastes, and the control of batch color differences is an important guarantee for achieving the accuracy and reproducibility of system color mixing.
The impact of color paste compatibility on the system is mainly the economy of color mixing and the reproducibility of color mixing. The compatibility of the color paste is mainly manifested in the flocculation, thickening or precipitation of the pigment from the paint. These phenomena will cause the tinting power of the color paste to decrease, thereby increasing the amount of color paste, uneven distribution of color paste in the paint, etc., which will directly affect the economy and accuracy of color mixing.
(2) Selection of color paste for color mixing system
From the perspective of color gamut, the selection of colorants needs to have types corresponding to each main color in the hue circle to meet the color gamut requirements of color mixing. An integrated coloring system that fully takes into account the cost and performance of the coloring system will be equipped with about X+Y color pastes to meet different needs. Among them, branch Branch Y is a supplementary factory high-concentration color paste that takes into account the weather resistance needs of exterior wall colors and an attractive cost advantage.
From a performance perspective, the selection of colorants requires the use of pigment varieties with high environmental resistance to meet the exterior wall coloring requirements. For organic pigments, due to the particularity of the crystal structure and the smaller particle size of the pigments than inorganic pigments, they have the advantages of bright colors, high saturation, and strong tinting power. But the finer the pigment is ground, the better. The smaller the particle size of the pigment, the larger its specific surface area and the more light energy it absorbs, so the unit tinting power is stronger. However, there are also downsides. The smaller the particle size, the greater the destructive effect of water vapor, oxygen and other substances on the pigment, which will lead to the deterioration of the weather resistance of the pigment. This is also one of the reasons why some organic pigment varieties have larger original particle sizes and better weather resistance.
Therefore, the finer the pigment, the better. Although some color pastes with the same pigment index have small fineness and high tinting power, their weather resistance cannot be guaranteed. Especially for the color paste of the color mixing system, its fineness should be controlled within an appropriate range. Appropriate fineness, that is, achieving the optimal number of effective coloring particles, helps to relatively improve the weather resistance of the color paste.
From an economic perspective, integrated color mixing system colorants need to fully consider the use of high-concentration colorants in the same color gamut to reduce color mixing costs.
