In the process of color matching of white base coating for metal packaging, accurate control of the brightness of white is a critical and complex task, which involves multiple factors and precise operating skills.
Titanium dioxide is the most commonly used white pigment in white base coating for metal packaging. Its crystal structure and particle size distribution have an important influence on the brightness of white. Rutile titanium dioxide has a high refractive index and hiding power, which can provide a brighter white. At the same time, titanium dioxide with uniform particle size and good dispersibility should be selected, which can reduce the scattering of light and improve the purity and brightness of white. In addition, a small amount of auxiliary pigments such as zinc oxide can be added to fine-tune the hue of white and further enhance the brightness.
Good dispersion can make the white pigment evenly distributed in the coating system and give full play to its optical properties. In the dispersion process, suitable dispersants and dispersing equipment are required. Dispersants can reduce the surface tension between pigment particles and prevent agglomeration. High-speed stirring and grinding equipment can refine the pigment particles and evenly disperse them in the coating. By controlling the dispersion time and speed, the best dispersion effect can be achieved to ensure that the brightness of the white base coating is not affected by pigment agglomeration.
In addition to white pigments and dispersants, other ingredients in the coating, such as resins, solvents and additives, will also affect the brightness of white. Choosing resins with low viscosity and high transparency can reduce the absorption and scattering of light and improve the brightness of white. The evaporation rate of the solvent also needs to be reasonably controlled. Too fast or too slow evaporation rates may cause defects on the coating surface and affect the appearance of white. In addition, adding an appropriate amount of leveling agents, defoamers and other additives can improve the construction performance and surface quality of the coating and indirectly improve the brightness of white.
Using high-precision color mixing equipment, such as electronic scales, mixers and grinders, can ensure that the amount of pigments and other ingredients added is accurate. At the same time, with the help of instruments such as colorimeter, the brightness and color changes of white base coating can be monitored in real time. During the color mixing process, the prepared paint sample is compared with the standard color card, and the various color parameters are measured by the colorimeter. Fine-tuning is performed according to the measurement results until the required brightness value is reached.
The ambient temperature, humidity and light conditions during the color mixing process will affect the brightness of white base coating. Generally speaking, the temperature should be controlled at 20℃ - 25℃, and the humidity should be 40% - 60%. The visual effect of white will be different under different lighting conditions, so color matching and color testing should be carried out under standard lighting conditions to ensure color accuracy and consistency.
Skilled operators can accurately judge the color change trend and make reasonable adjustments based on color theory and practical experience. They are familiar with the characteristics and interactions of various pigments, and can flexibly use color matching techniques to quickly and accurately mix white base coatings that meet the brightness requirements. At the same time, operators also need to have good observation and patience, carefully observe the results of each color matching, and continuously optimize and adjust.
Before mass production, the prepared white base coating needs to be quality controlled and stability tested. By testing the performance indicators of the coating such as viscosity, drying time, hiding power, brightness, etc., ensure that it meets the production requirements. At the same time, it is also necessary to conduct aging tests and weather resistance tests on the white base coating to observe the changes in white brightness during long-term storage and use, and promptly discover potential problems and make improvements to ensure the stability and consistency of product quality.
Accurately controlling the brightness of white base coating for metal packaging requires multiple aspects, including pigment selection, dispersion process, formula design, equipment and instruments, environmental factors, operator skills, and quality control. Only when each link is accurately and strictly controlled can a white base coating with accurate brightness and stable quality be formulated.
