The color matching of plastics is the key to the coloring of plastics. Only with good color can you prepare a product that is excellent and suitable. In the color matching process, first of all, to determine the application requirements of the product, and according to the coloring properties of the plastic material, select the appropriate colorant. When selecting the color, the technician should strictly check the color, tinting strength, dispersibility, performance, processing balance stability, mixing and cost of the available pigments, and then select the pigment to be used. In addition to relying on the technical expertise of the technicians, the color selection and color matching effects require technicians to have sound visual functions. At the same time, it depends on high-tech color matching instruments and equipment. This article on plastic color matching procedures and color matching methods.
1. Color matching program
Color matching is one of the important aspects of coloring. The first choice for color matching is to design the preliminary formula, and then adjust the preliminary formula to make it suitable for scale production and ensure the uniformity of color of plastic products.
1.1 Design of the preliminary formula
(1) According to the requirements of the overall design of plastic products, find a sample similar to the standard color sample as a reference. Whether the reference is selected properly or not is directly related to the coloring effect. In order to find a better coloring reference object, it is necessary to accumulate and prepare more colored plastic swatches or plastic color materials for reference. At the same time, the color selection experience and lessons should be compiled into corresponding coloring formulas for reference.
(2) In the absence of reference materials, the color shade, hue and brightness of the plastic products (samples) should be carefully observed and analyzed, and the color properties should be determined to determine whether the colors used are transparent or opaque, and whether they contain other special pigments. (such as fluorescent pigments, metallic pigments, etc.), and then according to the Munsell color system color.
(3) Repeatedly comparing the difference from the standard color sample and the reference substance in terms of hue, brightness, gradation, etc., on the basis of which the colorant formulation of the reference substance is corrected, and a preliminary formula is prepared.
Or design the required color according to the Munsell color system calibration principle, and draw up the preliminary formula.
1.2 Adjusting the formula The physical coloring test was carried out according to the proposed preliminary formula, and the colored sample was compared with the standard color sample and the reference material to further adjust the coloring formula. Then, according to the adjusted formula, the actual sample is prepared for comparison, and then the formula is adjusted, and thus repeated until the actual color tone is the same as the standard color sample or reaches the satisfactory level closest to the standard color sample. Finally, the coloring recipe is determined for production. However, the color chosen is usually not the same as the color of the plastic products produced in actual production. The reason for these differences is largely the color weighing error. So how to make the color matching accurate? How to make the color matching consistent in continuous production?
The accuracy of color matching is based on the selection of accurate pigments (dyeing materials). The choice of pigments (dyes) is based on the understanding of the effects of the products and the observation of the samples. Understanding and observing the samples depends on the experience and skills of the color matching personnel. . At present, many units use instrument color matching, but some units still use artificial visual methods for color matching. Although the manual color matching method is simple, it requires a lot of experience from visual inspection personnel. When two objects are viewed under the same light source (such as daylight), the colors may be different. Similarly, for one observer, the color of two objects may be exactly the same; for another observer, it may be different. We call these two objects a conditional isomer or a conditional color pair, also known as a conditional color or a variable color. If two objects are required to look the same under any light source, it means that the spectral reflection curves of the two objects must be the same. This color matching is called unconditional color matching or non-color changing color matching. Immutable color matching requires the same colorant to be used in the color matching sample. It is impossible to adjust the color of the plastic to an immutable color. There are many reasons for this. For example, the dispersion of the same pigment varies among different plastics; in a plastic, sometimes it needs to be achromatic or toned to remove other colors in the original plastic; In another type of plastic, this adjustment may not be necessary. Understand these situations, we have done a good job in the actual color matching process, and do not pursue immutable color matching. Since the colors we match are all variable colors, which one should we prevail? This requires a specific analysis of the specific problem, the principle is to simulate the final use of the product to observe the color. If the product is ultimately used outdoors, it should also be color-selected under natural light when matching colors.
2. Color matching method
2.1 visual color matching
An experienced color-matcher must have a clearer idea of ​​the colorants he needs before color matching. To master the general rule of coloring mixed coloring, it should also have a clear understanding of the properties of the colorants used, such as hue, color, migration, heat resistance, weather resistance, chemical stability, etc., while accumulating representative Various plastic coloring samples and color combinations. Before finding a suitable colorant formulation, a large number of tests must be performed and the same color is repeatedly toned until the desired color is obtained. Obviously, the visual color matching method is a trial and error method, not very scientific. Because this method is simple and practical, it is still widely used. However, this method is very time consuming and requires a relatively rich experience of the operator, otherwise it will be difficult to operate.
2.2 Instrument color matching
The instrument color matching method is based on the visual color matching method. This method uses a spectrophotometer and other measuring instruments to replace the functions of the human eye and the brain. The trial-and-error process of color scale is performed by computer simulation without the need for actual mixing of the coloring of the plastic. The operator only needs to measure the reflectance, its standard value, and select the pigment used for color matching. The measurement system is made to match the standard conversion value by adjusting the concentration of the color matching pigment. If the operator selects a reasonable color, the system will output a recipe in the form of a mass fraction and then convert the percentage formula to a mass ratio.
If (qualitative) knows which type of colorant is used in the sample, the computer can easily calculate the actual amount of various pigments in the formulation. However, the formulation of the colorant used in the sample is often unknown, in which case the color coordinates of the sample can be used to match the color. There are many analytical and empirical relationships for selecting the appropriate colorant formulation and determining the concentration to apply to each formulation. The establishment of these relationships requires a lot of calculations. Using a computer reduces the time for the entire color matching process to ten minutes.
One color can be formulated from several formulations containing different pigments. The performance characteristics and ingredients of these formulations are different. Color matching instruments and computers can be used to derive a variety of formulas for color matching, to choose whether to use a small amount of expensive organic pigments, or to use a large amount of cheap inorganic pigments, so that people have larger Choose a range.
In addition, instrument color matching and visual matching of fluorescent materials are difficult because fluorescence is a new variable, and different results may occur when two samples are compared under different light sources. Not only does the light source affect the observation of the sample, but the angle between the incident light and the viewing position also affects the observation of the sample.
3 problems should be paid attention to during the color matching process
At the time of toning and coloring, attention should first be paid to the color light of the colorant. Each coloring agent has its own color light in addition to its natural color, that is, a comparatively minor pigment which is compared with the determined standard color, which is called color light. . Such as phthalocyanine green with yellow light, medium chrome yellow with red light and so on. If the medium chrome yellow is combined with the phthalocyanine green, it is necessary to avoid the red light of the medium chrome yellow, and there are three primary colors of red, yellow and blue, so that the color of the distribution is dark. Therefore, in order to obtain a bright color, when the two colorants are combined, it is necessary to pay attention to the interference of the color light. In the actual preparation of pure red, the color matching of Lissol red and fast red can be used, which is offset by the yellow, blue (purple) and other color light, and white coloring agent is added to improve the brightness.
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