Definition of plastic color matching:
The color matching is based on the three basic colors of red, yellow and blue (three primary colors), with the color that is pleasing to the eye, meets the color difference requirements of the color card, meets the color and economy that the customer hopes to obtain, and does not change color during processing and use. In addition, plastic coloring can also give plastics a variety of functions, such as improving the light resistance and weather resistance of plastics; imparting special properties to plastics, such as electrical conductivity, antistatic properties, antibacterial properties, etc.; different colored agricultural mulch films have weeding or pest control , breeding, and so on. That is, color matching can also achieve an application requirement.
Colorant:
Pigment characteristics: Pigments are colorants that are insoluble in common solvents. Therefore, in order to obtain the desired coloring performance, it is necessary to uniformly disperse the pigment in the plastic by mechanical heating and kneading.
Pigment classification: According to structural pigments, it can be divided into organic pigments and inorganic pigments.
Organic pigments:
Advantages: high tinting strength, bright color, complete chromatogram, low relative density and small addition amount.
Disadvantages: heat resistance, weather resistance and hiding power are not as good as inorganic pigments, poor dispersion effect, poor transparency compared to dyes, and high price.
Mainly used in: POM, PE, PP, TPU, TPE and other crystalline materials and partially bright (dark color products that can not be achieved by dyes).
Inorganic pigments:
Advantages: good thermal stability, excellent weather resistance, excellent light stability, low price and excellent dispersion performance. For example: titanium dioxide, carbon black, and the like.
Titanium dioxide series: mainly titanium white powder, zinc oxide, zinc antimony white. Titanium dioxide is divided into two structures: rutile and anatase. Rutile titanium dioxide has high refractive index, high hiding power, stability, and good weather resistance. If the titanium dioxide is not processed by the original factory, a large amount of black spots will be generated in the color matching process. It is dispersed and not opened, so it needs to be dispersed by dispersing agent before it can be used. Some manufacturers' grades are processed. Entering the market, such materials can be used directly. It is mainly used to cover the transmittance of resin and increase the whiteness.
Carbon black: It is a common black pigment, which is cheap, and also has ultraviolet protection (anti-aging) effect and conductive effect on plastics. Different production processes can obtain various carbon blacks with a wide range of particle sizes, and the properties are also very different. . Carbon black is divided into pigment carbon black and rubber reinforcing carbon black according to the use. The pigment carbon black is further classified into high pigment carbon black, medium pigment carbon black and low pigment carbon black according to its coloring ability. Carbon black particles are prone to aggregation. To increase the coloring power of carbon black, it is necessary to add a dispersant for processing to solve the dispersibility of carbon black.
Disadvantages: the tinting strength is relatively poor, the relative density is large, the amount of addition is large, and the color is not bright;
Mainly used for: to increase the color concentration (depending on the color requirements, generally all kinds of resins), especially in engineering plastics have good superior performance, such as: PA, PC, PBT, POM, PPO, PPS, etc. Materials and non-transparent colors, gray and other resins.
Dyes :
Advantages: Dyes are organic compounds that can be used in most solvents and dyed plastics. They have the advantages of low density, high tinting strength and good transparency.
Disadvantages: However, its general molecular structure is small, and it is easy to migrate when colored (crystalline material) is more expensive than inorganic, and some prices are close to the price of organic pigment.
Pearlescent pigment: also known as mica titanium pearlescent pigment, is a titanium dioxide coated mica wafer. According to different hue, it can be divided into silver-based pearlescent pigments, rainbow-based pearlescent pigments, and colored pearlescent pigments.
be careful:
When purchasing pigments, you must understand the dye index (CI) of the pigment. CI is a compilation of international dyes and pigments compiled by the British Dyers Association and the American Textile Chemist and the Dyed Association. Each pigment is applied and chemical. The structure category has two numbers, which avoids misunderstanding of the same molecular structure and different pigments when purchasing. It also facilitates the management of color during use and the use of the correct pigment to find the cause when problems occur.
Color matching process:
The color matching can be directly added to the resin method, the toner mixed resin extrusion method, and the master batch method using the toner.
The toner is directly added to the resin method: the toner is directly mixed with the plastic resin, and then sent to the next product molding process, the process is short, the cost is low, but the working environment is poor, the coloring power is poor, the coloring uniformity and the quality stability are poor. Toner mixed resin extrusion method: This method has the best effect on the uniformity of resin and color, and can fully disperse the pigment in the resin, with accurate color, clean quality and easy processing.
Masterbatch method:
It is a kind of coloring agent and carrier resin, dispersing agent and other auxiliary agent formulated into a certain concentration of coloring agent. When the product is formed, a certain amount of color masterbatch is added according to the coloring requirement, so that the product contains the required coloring amount to achieve the coloring requirement.
The 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 coloring resin and process, and there are three kinds of masterbatch of injection molding, blown film and extrusion grade. . The color masterbatch has a higher coloring power due to the pretreatment of the pigment, the dosage can be reduced and the quality is stable, and transportation, storage, use and convenience, and environmental pollution are greatly reduced.
The dispersing agent removes the surface air by wetting and infiltrating the pigment, disperses the agglomerates and agglomerates into fine, stable and uniform particles, and does not agglomerate during the processing. The commonly used dispersing agent is a low molecular weight polyethylene wax. For EVA waxes or oxidized polyethylene waxes, which are difficult to disperse organic pigments and carbon blacks, synthetic low molecular weight polyethylene waxes and polyethylene low molecular weight polyethylene waxes are very different. Other additives include coupling agents, antioxidants, light stabilizers, antistatic agents, fillers, etc., depending on the requirements and variety, called multi-functional masterbatch, and if added brightener, it is beneficial to molded products. Demolding and improving the surface brightness of the product.
The performance indicators of masterbatch include color difference, whiteness, yellowness, yellowing degree, thermal stability, oxygen index, melt flow rate, etc. Of course, pigment fineness, migration, chemical resistance, toxicity and color masterbatch Particle performance is related, and some indicators are important in special applications, such as the filter size (DF value) fineness of the fiber grade masterbatch.
Color management and instruments:
The hardware for color management has a colorimeter and a computer that processes the measured data. The colorimeter can be divided into two types, a spectrophotometer and a color difference meter, instead of measuring the color of the human eye, and removing the influence of human factors on the measurement result.
The spectrophotometer is used to measure the reflection coefficient of each wavelength to the completely diffuse reflection surface, and the chromaticity value or chromatic aberration cannot be directly obtained, but the chromaticity value and other various values ​​can be evaluated by the data processing. Spectrophotometers can be classified into two types: diffraction grating diffraction and interference filter splitting. The advanced spectrophotometer with built-in microprocessor has 0%, 100% auto-correction and multiplier increase, which improves accuracy.
The color difference meter is a simple test instrument, which is to produce a filter with the same spectral sensitivity as the human eye. It is used to measure the light of the sample. The key is to design a photometric sensitivity characteristic of the photoreceptor. Filter for measuring color difference under a certain light source. The color difference meter is small in size and easy to operate. It is suitable for batch management of the same product with small change in spectral characteristics. The color difference meter with small microcomputer is easy to use with standard template. Correct and output multiple color difference values. The color management software has a spectral reversal rate curve, a color difference formula, a conditional color representation, an opacity representation, and a haze representation. The spectral reflectance curve is used for analysis when selecting a colorant and cannot be used to determine the color uniformity. Color difference is one of the most important indicators in color management, but the color difference obtained by different color difference formulas is different, so the chromaticity system or color difference formula must be indicated.
The computer color meter has the following features:
(1) Color matching Create a common pigment (dye) database according to requirements (prepare the basic swatch and input). Then enter the incoming swatch into the computer under the software menu, click on a number of candidate pigments in the keyboard, and immediately calculate a series of recipes, and sort them by color difference and price respectively for color matching;
(2) Recipe correction correction The computer lists the formula and other source formulas. When the color difference is unqualified, the inconsistent reflection curve displayed by the display is used to increase or decrease the amount of pigment directly through the keyboard until the two curves are substantially coincident, and the corrected formula is obtained;
(3) Color measurement and color difference control The coloring strength of the colorant, the whiteness of the product, the color fastness of the product, and the color chromatic aberration are measured. Because the computer can quantitatively express the performance indicators of color, 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 daily work can be stored in the computer, which is convenient for searching, searching and as a reference for modification. It is convenient and fast, and improves work efficiency and convenience. Confidential.
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