Color matching techniques and application of colorants

First, the definition:

The color matching is based on the three basic colors of red, yellow, and blue, and is matched with colors that are desirable, conform to the color difference requirements of the color chart, and are economical and do not change color during processing and use. In addition plastic coloring can also give a variety of plastic functions, such as improving the plastic light resistance and weather resistance; to give some of the plastic special features, such as conductivity, antistatic properties; different color agricultural film with weeding or prevention of insects, eel and so on. That is, color matching can achieve certain application requirements.

Second, coloring agent:

Coloring agents are mainly divided into two kinds of pigments and dyes. Pigments are colorants that are insoluble in common solvents. Therefore, to obtain the desired coloring properties, it is necessary to mechanically disperse the pigments uniformly in the plastic. According to the structure can be divided into organic pigments and inorganic pigments. Inorganic pigments are excellent in thermal stability and light stability, low in price, but relatively poor in coloring power and relatively high in density; organic pigments have high coloring power, bright color, complete chromatogram, and low relative density, and disadvantages are heat resistance, weather resistance and hiding. The strength is not as good as inorganic pigments. Dyes are organic compounds that can be used in most solvents and dyed plastics. They have the advantages of low density, high coloring power, and good transparency. However, their general molecular structure is small and they tend to migrate when they are colored.

The main white pigments are titanium dioxide, zinc oxide, and zinc antimony white. Titanium dioxide is divided into rutile type and anatase type. Rutile titanium dioxide has a high refractive index, high hiding power, stability, and good weather resistance.

Carbon black is a commonly used black pigment, which is cheap and has ultraviolet protection (anti-aging) and conductive effect on plastics. Different production processes can obtain various carbon blacks with a wide range of particle sizes, and the properties vary greatly. Carbon black is divided into pigmented carbon black and rubber-reinforcing carbon black depending on the purpose. Pigmented carbon black is classified into high-pigmented carbon black, medium-pigmented carbon black, and low-pigmented carbon black according to its coloring ability. The carbon black particles are prone to aggregation, and the coloring power of the carbon black needs to be improved, and the dispersibility of the carbon black must be solved.

Pearlescent pigment, also known as mica titanium pearlescent pigment, is a titanium dioxide coated mica wafer. According to the different hue, it can be divided into silver-white pearlescent pigments, rainbow pearlescent pigments, colored pearlescent pigments.

To purchase pigments, it is necessary to understand the dye index (CI) of pigments. CI is a compilation of international dyes and pigments published by the British Dyers Association and the American Association of Textile Chemists and Colorists. Each pigment is applied and chemically structured. There are two numbers in the category to avoid misunderstanding of the same molecular structure and different colors when purchasing, and it is also helpful to manage and find out the reasons for use.

Third, coloring coloring process:

Coloring coloring can be directly added to the resin and the masterbatch method.

After the toner and the plastic resin are directly mixed, they are sent to the next product forming process. The process is short and the cost is low, but the working environment is poor, the coloring power is poor, and the coloring uniformity and quality stability are poor.

Masterbatch method is a colorant and carrier resin, dispersant, and other additives formulated into a certain concentration of colorant pellets, the product according to the coloring requirements when molding, adding a certain amount of masterbatch, so that the product contains the required colorant dose, to achieve Coloring requirements.

Masterbatch can be classified according to the resin to be colored, such as ABS masterbatch, PC masterbatch, PP masterbatch, etc.; it can also be classified according to the process of colored resin and additive. There are three types of masterbatch: injection molding, blown film and extrusion grade. . The masterbatch has higher coloring power because of the pretreatment of the pigment, the amount can be reduced and the quality is stable, and the transportation, storage, use is convenient, and the environmental pollution is greatly reduced.

The dispersant removes the surface air by wetting and penetrating the pigment, disperses the agglomerates and agglomerates into fine, stable and uniform particles, and no longer coagulates during the processing. The commonly used dispersant is a low molecular weight polyethylene wax. For the more difficult to disperse organic pigments and carbon black using EVA wax or oxidized polyethylene wax, the synthesis of low molecular weight polyethylene wax and polyethylene cracking method of low molecular weight polyethylene wax is very different. Other auxiliaries include coupling agents, antioxidants, light stabilizers, antistatic agents, fillers, etc., depending on the requirements and variety of additives, known as multi-functional masterbatch, and if brighteners are added, it is beneficial to molded products. Demoulding and improve the surface brightness of products.

Color masterbatch performance indicators are color, whiteness, yellowness, yellowing, thermal stability, oxygen index, melt flow rate, of course, pigment fineness, mobility, chemical resistance, toxicity and color masterbatch The properties of the pellets are relevant, and some of the specifications are important in specific applications, such as the fineness of the DF value of the fiber-grade masterbatch.

Fourth, color management and instruments

The color management hardware includes a colorimeter and a computer that processes the measured data. Colorimeter can be divided into spectrophotometer and colorimeter two kinds, instead of the human eye to determine the color, remove the influence of human factors on the measurement results.

The spectrophotometer is used to measure the reflection coefficient of a completely diffuse reflecting surface at each wavelength, and the colorimetric value or color difference cannot be obtained directly, but the colorimetric value and other various values ​​can be evaluated by processing the data. Spectrophotometers can be classified into two types: diffraction gratings and interference filters. The advanced spectrophotometer with built-in microprocessor has 0%, 100% auto-calibration and magnification increase, which improves the accuracy.

Colorimeter is a kind of simple test instrument, that is to make a filter with spectral characteristics equal to the sensitivity of human eye sense. Using it to measure the light of the template, the key is to design a sensor with the sensitivity of the photoreceptor and can The filter for measuring the color difference value under a certain light source has a small volume and is easy to operate. It is suitable for the batch management of the same product with small change in the spectral characteristics. The color difference meter with a small microcomputer is easy to use with a standard model. Correct and output multiple color difference values.

The color matching management software has the spectral refraction rate curve, the color difference formula, the conditional color representation, the hiding power representation, and the haze representation. The spectral reflectance curve is used for the analysis when selecting the colorant and cannot be used to determine the color consistency. The color difference value is one of the most important indicators in color management, but the color differences obtained by different color difference formulas are not the same, so it is necessary to specify the color system or the color difference formula used.

Five, computer color:

The use of computers for color formulation and its management has been successfully used in plastic hues.

The computer color matching instrument has the following functions:

(1) Color Matching Establish a database of commonly used pigments (prepare basic swatches and input them) as required. Then enter the incoming swatches into the computer under the software menu, point out a number of candidate paints in the keyboard, and immediately calculate a series of formulas, which are sorted by color difference and price respectively, for color matching selection;

(2) Recipe correction The correction computer lists formulas and formulas from other sources. When the color difference is unqualified, the inconsistent reflection curve displayed on the display is used to increase or decrease the amount of pigment directly through the keyboard until the two curves basically coincide and the corrected formula is obtained;

(3) Color Measurement and Color Difference Control The color intensity of the colorant, the whiteness of the product, the color fastness of the product, and the color difference of the color are measured. As the computer can quantify the color performance indicators, it is beneficial to the communication and transmission of information between the two parties;

(4) Color management The color samples, recipes, process conditions, production date, and user information in the daily work can be stored in the computer for easy retrieval, search, and reference for modification. It is convenient, fast, and improves work efficiency. Confidentiality.

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