Coating science and technology: influence of powder coating manufacturing and coating process on product color difference

Coating science and technology knowledge: the main reason for color difference of powder coating products From the formulation design, raw material selection, manufacturing process and construction process of powder coating, the methods to solve the problem of color difference are listed 1 The main functions of the coating are introduced On the one hand, it can make the coating products have good decorative and beautifying functions; on the other hand, it can improve the anti rust, anti-corrosion and protection functions of the coating products Powder coating is no exception, also for these two purposes The decoration and beautification function of powder coating is very important because of the appearance and color of the coating Generally speaking, the color of the coating product shall be consistent with the color plate or color card provided by the user, and the color difference shall be within the color difference range of the coating allowed by the user Especially between different batches of coating products sprayed with different batches of powder coating; with the same batch of powder coating, coating the color difference between workpieces of different materials, shapes, sizes and thicknesses will affect the color difference of the final assembled products, and finally the quality of the coating products According to the production experience of powder coating and the coating experience of powder coating plant, in order to ensure the color difference of powder coating products and meet the requirements of users, it can not be solved only by powder coating manufacturer or one party of powder coating plant, but also by the close cooperation of both parties who produce and use powder coating to meet the requirements of color difference of coating products In order to overcome the problem of color difference in coating products, the following three aspects should be considered: the formula design of powder coating and the selection of raw materials; the strict control of powder coating manufacturing process; and the strict control of powder coating process Now from the experience of production practice, we will talk about our views on the above three issues The formulation design of powder coating and the selection of raw materials the formulation design of powder coating and the selection of raw materials are the internal fundamental factors affecting the color stability of coating products If this is not a good level, then the congenital deficiency of powder coating, with the latter measures to make up for is difficult to solve, or even unable to make up Therefore, this problem should be considered first, and then the problems that need to be solved in the manufacturing and coating of powder coating should be considered 2.1 formulation design of powder coating the formulation design of powder coating is of great significance to the stability of coating color of powder coating (1) First of all, in the formulation design of powder coatings, because the selection of pigment varieties plays a decisive role in the stability of the coating color, we must consider the high baking temperature of powder coatings At present, the baking temperature of most powder coatings is 180 ℃ ~ 200 ℃, and the heat-resistant temperature of pigments must meet this requirement For the pigments used in weather resistant products, the requirements of light resistance and weather resistance shall be considered The light resistance grade of the best pigments shall reach 7-8 (the best grade is 8), and the weather resistance grade shall reach 4-5 (the best grade is 5) For indoor products, it is also necessary to consider the problems such as the discoloration of coating film when the coating product is placed in a sunny warehouse or temporarily placed before leaving the factory Therefore, the light resistance of the pigment should not be too poor Secondly, some components in the formula, such as resin, curing agent and additives, will also make the film color unstable in the curing process For example, the commonly used epoxy resin, 2-methylimidazole and cyclopentadienyl carboxylic acid matting agent in epoxy and polyester epoxy powder coating are prone to yellowing when curing in light color powder coating In order to solve this problem, in the formulation design, we use resin varieties, add anti yellowing agent, or use non yellowing accelerant, or non yellowing extinction resin to solve the problem of unstable color difference (2) In the formulation design of powder coating, the covering power of powder coating should be considered When the coating thickness reaches the user's requirements, the covering power of the coating can completely cover the substrate, so that the color of the substrate will not affect the color difference of the coating Because when the covering power of the powder coating is not good, the film thickness will affect the color difference of the film, so it is fully considered in the formula design that when the coating thickness is reached, the covering power of the film is better, so that the problem of color difference between workpieces with different coating thickness caused by the covering power difference of the film can be avoided.