Color matching is based on the three basic colors of red, yellow, and blue (the three primary colors) to match the color that is attractive, meets the color difference requirements of the color card, conforms to the color that the customer wishes to get, is economical, and does not change color in processing and use.

01 Colorant

Pigments and dyes
Characteristics of pigment: Pigment is a colorant which cannot be dissolved in common solvents, therefore, to obtain ideal coloring performance, it is necessary to use mechanical heating and mixing methods to disperse the pigment uniformly in the plastic.
Pigment Classification: According to the structure pigment can be divided into organic pigment and inorganic pigment.

Inorganic pigments:
Advantages: good thermal stability, very good weathering performance, excellent light stability, low price, superior dispersion performance. Examples: titanium dioxide, carbon black, etc.

Titanium dioxide series: There are mainly three kinds of titanium dioxide, zinc oxide and zinc barium 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. Titanium dioxide in the original factory factory if there is no dispersion processing, in the process of color matching will produce a large number of black spots, belongs to the dispersion is not open state, so you need to use dispersant for dispersion processing before you can use, some manufacturers of the brand after processing into the market, so that the material can be used directly. It is mainly used to cover the transmittance of resin and increase the whiteness.

Carbon black: It is a commonly used black pigment, cheap, and also has the role of UV protection (anti-aging) and conductive effect on plastics, different production processes can be obtained in a wide range of particle size of different carbon black, the nature of the difference is also very big. Carbon black according to the use of carbon black and rubber reinforcing carbon black, pigmented carbon black according to its coloring ability is divided into high pigmented carbon black, medium pigmented carbon black and low pigmented carbon black. Carbon black particles are prone to aggregation, in order to improve the coloring power of carbon black, to solve the dispersion of carbon black need to add dispersants for processing before use.

Organic pigments:
Advantages: high coloring power, bright color, complete color spectrum, small relative density, small amount of additive.
Disadvantages: not as good as inorganic pigment in terms of heat resistance, weather resistance and covering power, poor dispersion effect, poor transparency compared to dyes, and high price.

Dye:
Advantages: Dyes are organic compounds that can be used in most solvents and dyed plastics. Advantages include low density, high coloring power, and good transparency.
Disadvantages: but its general molecular structure is small, easy to migrate when coloring (crystalline materials) price is more expensive than the inorganic, part of the price and the price of organic pigments close to.

pearl pigment
Also called mica titanium pearlescent pigment, it is a kind of titanium dioxide coated mica wafer. According to the different hues, it can be divided into three categories: silver-white type pearlescent pigment, rainbow type pearlescent pigment, and color type pearlescent pigment.

caveat
When purchasing pigments, it is necessary to know the dye index (C.I) of the pigment. C.I is an international compilation of dyes and pigments published by the British Dyers' Association and the American Association of Textile Chemists and Dyers, with two numbers for each pigment according to the application and the chemical structure category, so as to avoid any misunderstanding during the purchasing process due to the same molecular structure and different names of the pigments, and also to facilitate the management of the colors and their use during the use process. It also facilitates color management and the use of the correct pigment to find the cause of problems when they occur.

02 Color Matching Coloring Process

Color matching and coloring can be done by directly adding color powder to resin, mixing color powder with resin extrusion method and color masterbatch method.

Color powder directly added to resin method:
Color powder and plastic resin directly mixed, sent to the next step of the product molding process, the process is short, low cost, but the working environment is poor, poor coloring power, poor coloring uniformity and quality stability.

Color powder mixed resin extrusion method:
This method has the best effect on the uniformity of resin and color, and enables the pigment to be fully dispersed in the resin, with accurate color, clean quality and easy processing.

Masterbatch method:
It is colorant and carrier resin, dispersant, other additives formulated into a certain concentration of colorant granules, products molding according to the coloring requirements, add a certain amount of masterbatch, so that the products contain the required amount of colorant to achieve the coloring requirements.

Color masterbatches can be classified according to the resin to be colored, such as ABS masterbatches, PC masterbatches, PP masterbatches, etc.; can also be classified according to the process of coloring resin, there are three major types of masterbatches: injection molding, blown film, extrusion level. Due to the pretreatment of pigment, masterbatches have high coloring power, reduced dosage and stable quality, easy transportation, storage and use, and greatly reduced environmental pollution.

The dispersant excludes the surface air by wetting and penetrating the pigment, and disperses the cohesion and agglomeration into fine, stable and uniform particles, and no longer coalesce in the process, the commonly used dispersant is low molecular weight polyethylene wax, and EVA wax or oxidized polyethylene wax is used for the organic pigments and carbon black which are difficult to be dispersed, and there is a great difference between the synthetic low molecular weight polyethylene wax and low molecular weight polyethylene wax made by the method of polyethylene cracking. There is a big difference between synthetic low molecular weight polyethylene wax and polyethylene cracking low molecular weight polyethylene wax. Other additives are coupling agent, antioxidant, light stabilizer, antistatic agent, filler, etc., depending on the requirements and varieties of the amount to be added, known as multifunctional masterbatch, and then add brightener, which is conducive to the molded products to release the mold and improve the surface brightness of the products.

The performance indexes of masterbatches are color difference, whiteness, yellowness, yellowing, thermal stability, oxygen index, melt flow rate, etc. Of course, the fineness, migration, chemical resistance and toxicity of pigments are also related to the performance of masterbatches, and some of the indexes are very important in specialized applications, such as the fineness of the filtering value (DF value) of the masterbatches of fiber grade.

03 Color Matching Management

The hardware for color matching management consists of a colorimeter and a computer to process the measured data. Colorimeter can be divided into two kinds of spectrophotometer and colorimeter, instead of the human eye to determine the color, to remove the influence of human factors on the measurement results.
Spectrophotometer is used to determine the reflection coefficient of each wavelength on the completely diffuse reflection surface, can not directly obtain the chromaticity value or color difference, but through its data processing can be evaluated chromaticity value and other various values. Spectrophotometers can be divided into two types: diffraction grating spectroscopy and interference filter spectroscopy. Advanced spectrophotometers with built-in microprocessors have functions such as automatic correction of 0% and 100% and multiplication increase to improve accuracy.

Colorimeter is a simple test instrument, that is, to make a piece of filter with spectral characteristics equal to the color sensitivity of the human eye, with which the sample for photometry, the key is to design a photoreceptor with spectral sensitivity characteristics and can be measured in a certain light source color difference value of the filter, the colorimeter is small in size, easy to operate, it is more suitable for the spectral characteristics of the same small changes in the same kind of products for the management of the batch, with a small microcomputer Colorimeter with a small microcomputer, easy to calibrate and output more than one color difference value with a standard sample plate.

Color matching management software includes spectral reflectance curves, color difference formulas, conditional isochromatic representation, coverage representation, and haze representation. Spectral reflectance curves are used for analysis when selecting colorants and cannot be used to judge the consistency of colors. The color difference value is one of the most important indicators in color management, but different color difference formulas yield different color differences, so it is necessary to specify the chromaticity system or color difference formula used.

04 Computer Color Matching

colorimeter
The use of computers for color mixing formulations and their management has been successfully used for color matching and color mixing of plastics.
The computerized colorimeter has the following functions:
1) Color Matching
According to the requirements to establish a database of commonly used pigments (dyeing) (preparation of the basic color palette and input). Then input the incoming color palette into the computer under the software menu, point out several candidate pigments in the keyboard, and immediately calculate a series of formulas and list them according to the color difference and price sorting for color matching;

2) Formulation correction
Correct the computer listed formula, other sources of formula, color difference failed to use the monitor display inconsistent reflection curve directly through the keyboard to increase or decrease the amount of pigment, until the two curves basically overlap, resulting in the correction of the formula;

3) Color measurement and color difference control
Measurement of colorant tinting strength, product whiteness, product color fastness, and color chromatic aberration. Since the computer can quantitatively express the performance index of color, it is beneficial to the communication and transmission of information between both parties;

4) Color Management
Daily work in the color samples, formulas, process conditions, production date and user information can be stored in the computer, easy to retrieve, find and as a reference for modification, convenient, fast, improve work efficiency, and easy to confidentiality.