Coloring method and formulation design of pigment fillers in powder coatings

China Coatings Online News Information
Abstract Article on the scientific use of pigments in powder coating formulations and quickly and accurately according to the requirements of the customer sciss palette or color card color deployment, put forward a number of treatment methods.Introduction
Powder coating is a film-forming substance (often called solvent-free coating) that does not contain volatile parts and is a powder substance coated with air as a dispersing medium. Because it has the advantages of saving resources, reducing pollution, simple application and excellent film coating performance, people pay attention to it.
powder coating in the parts, production process, construction process and other aspects of solvent-based coatings are very different, coupled with the difficulty of dispersion of solid parts and high temperature baking during construction. Color conditioning is particularly important in powder coatings. According to some manufacturers, powder paint production in the color problem, is the manufacturer timely delivery to customers, delay the production schedule of a major obstacle. Therefore, this paper on how to accurately and quickly according to the customer's scissive plate or color card to adjust its color and in the powder coating formula reasonable and economical use of pigments to propose some treatment methods.color and tonal method
color has three main properties, namely tone, brightness and purity or saturation, and to accurately determine the color. Two colors, if they have the same hue, brightness, and purity, are exactly the same color, or slightly different from each of the three parameters. The color is different. All colors can be divided into two categories, i.e. fade and color. White and all neutral gray until black belongs to the fade. The difference between the antichromation classes is the brightness, the amount of light reflected. The rest of the colors except fade are colors. Objects of the same hue appear different in color when exposed to white light of different brightness. The difference is not in the hue but in the brightness of the color. Color of a certain tone has strong or weak, from strong to weak can be regarded as the same color, if a different number of color, white or neutral gray and even black to dilute, then the formation of a series of color purity or called saturation will be different. Colors that are smallly different from neutral grays are called weak saturation, and colors that are largely different, i.e. little or no color, are called saturated.
In terms of color matching, the production of paint color matching, generally using a color-reducing color scheme, that is, in the process of mixing several pigments and obtaining a new color pigment, each pigment in the mixture will subtract a certain wavelength range of light and a certain amount of light energy from the white light irradiated to the mixture. The wavelengths of visible light are slightly different, the colors are different, and the human eye feels differently about them.
, yellow and blue are called the three primary colors and form the basis of various colors. Such as yellow plus blue into green, red plus blue into purple, red plus yellow into orange, and orange, green, purple is also known as asking color. If you mix and match between colors, or between primary, intercolor, and recolor, you can blend a very rich color. Figure l is a diagram of the color subtract scheme, and the two pigments opposite the center of the circle belong to complementary colors. Pigments that mix complementary colors at the right proportions do not get white, where as a result of dark gray, because they do not reflect enough light energy. Figure 1 subtracts the color scheme around the circle of many pigments, mixing two pigments that are not complementary colors, and the resulting color will be somewhere between the two pigments, the corresponding blend color can be found on the shorter arc linking the two. If you connect two pigments in a straight line, the closer the straight line is to the center of the circle, the darker the color you get. When you make colors according to a user-provided slab or card, you can usually do so using the following steps.▶ observation and analysis of the swatch
A closer look at the swatch to find out that the color of the swatch contains several monochromes (main and secondary) and the degree to which the color is bright or dim. Make sure the slab is powder paint. It is also solvent-based coatings, and the user provides model manufacturing time, preservation and other factors affecting the color of the coating film.▶-adjusting color
According to the observation of the swatch main and auxiliary colors, the initial drawing of a variety of pigments ratio, take a small proportion of the mixed color vegetable oil for color matching, in a smooth white porcelain plate will be color coating and customer color plate for careful comparison (in tone, brightness, saturation), found differences and then quantitative adjustment of the ratio. Continue to color, repeated many times, until the color is exactly the same as the customer's sci-color, record the ratio of various pigments and then according to the pigment cover strength and pigment PVC value to determine the color of the powder coating formula, and make it into a powder paint small sample color plate, check the reliability of the color. If there are differences, determine the nature of the color differences, and then fine-tune the color until the customer's requirements are met.
in the color matching process, there are two points to note: First, when using a strong covering pigment. Especially when mixing light complex colors, do not add color-strong pigments too much at a time, and before color must be fully stirred evenly: the second is to estimate the color difference produced after baking and the effect of the yellow phase of the resin itself, to find out the law between them. Accurately judge and eliminate it.Although there are many varieties of salt filler design
powder coatings informulation, the appearance requirements of coating properties are usually color, masking force, gloss and flat state, etc., in which the color, masking force and gloss of the coating are closely related to the pigments used in the coating. Pigments can give the coating film a variety of beautiful bright colors, fillers can reduce the cost of powder coating, enhance the mechanical properties of the coating. Therefore, in the design of various powder coating formulations, in addition to the correct use of resins, pigments and additives ratio relationship, but also pay great attention to pigment selection, as far as possible to use those fine particle size, good dispersion performance, high coloration, high temperature resistance pigments. It is generally believed that the pigment in the powder coating particle size is small, low content, it forms a good coating decorative, bright color, high gloss, smooth coating film;
In the design of powder coating formulation pigment dosage, there are two very important parameters, one is pigment / base material, referred to as pigment ratio, by the pigment weight percentage to the resin weight percentage of the weight ratio to express;
choose the right Yanjibi. Very useful for determining the original formulation of powder coatings. For example, in the case of general high gloss powder coatings, the Yanji ratio is between 0.5 and 4. The PVC value in powder coating has a certain relationship with the gloss of the coating film, which can be divided into as follows: (1) lightless coating, PVC value is more than 40%, (2) half-gloss coating, PVC value is between 20% and 40%, (3) highlight coating, PVC value is less than 20%. But this magnitude does not represent all types of products, and there is no clear line between them. The critical PVC value of different resins is also different, for example, in the case of polyester, epoxy, acrylic three powder coatings. Its critical PVC value is polyester resin> epoxy > acrylic. Take titanium dioxide pigments, for example. Up to 40% in polyester and only 20% in acrylic resins. But in terms of gloss, acrylic > polyester > epoxy. The PVC value of the pigment in the coating film must be lower than the critical volume concentration in order to satisfy the mechanical and weather-resistant properties of the coating film. If the amount of pigment is too high. Exposure and other effects can cause early damage to the coating film, while the amount of pigment is too low. It is also detrimental to mechanical and light resistance. Therefore, as far as powder coatings are speaking, they cannot rely entirely on increasing PVC values to achieve light dissipation. Because doing so will not only reduce the performance of the coating film, but also the melting flow of the coating film is poor, making it difficult for the coating film to form a complete continuous film. Therefore, to obtain an economical, ideal lightless or semi-light powder coating, in addition to the PVC value in the powder coating formulation, a small amount of anti-light must be added. Table 1 lists the ratio of resins to pigments in commonly used powder coatings, and Table 2 lists the formulations of some high-gloss, half-light, light-free powder coatings.