The application of plastic materials and their products in today's world has involved various industries, as well as every family and individual. Plastic has become an indispensable element in a colorful world. The choice of colorants for plastic products has also become a hot topic among professionals in the plastic industry, which is also related to the quality, cost, and other aspects of your products.

1、Types of plastic colorants

It can be divided into four types based on its physical form: powdered colorants - pigments; Paste colorant - color paste; Liquid colorants; Solid colorant - color masterbatch. Among them, powder colorants and solid colorants are widely used.
 

2、Characteristics of various colorants

（1）The characteristics of color powder coloring: The method of directly using color powder (pigment or dye) to add an appropriate amount of powdered additives to color plastic particles, also known as dry coloring.

　　Its advantages are good dispersion, low cost, and small batch operation. Due to its elimination of the consumption of manpower and material resources in the processing of other colorants, such as color masterbatch and color paste, the cost is low and the buyer and seller are not limited by quantity. It is generally not possible to accept customized quantities of 1-2kg for the production of color masterbatch, but the color powder can be customized as needed, making it very convenient to prepare. Using color powder coloring, compared to other granulation coloring methods, the processed resin undergoes less degradation process, which is beneficial for reducing the aging of plastic products and increasing their service life.

　　But the biggest drawback is that pigments can fly during transportation, storage, weighing, and mixing, causing pollution and seriously affecting the working environment. With the requirements of environmental protection and enterprise ISO9000 standards, color powder coloring is becoming increasingly limited. However, for special effects of coloring, using color powder direct mixing coloring has some effects that cannot be achieved by color masterbatch coloring. For example, some pigment powders with poor heat resistance and fear of shearing are used to make color masterbatches. Due to their long duration of withstanding high temperatures and being subjected to shearing in color masterbatch processing equipment for a long time, the coloring effect will be significantly weakened, such as pearl colored powders, fluorescent powders, and luminous powders. Using pearl powder to make color masterbatch and then color plastic, compared to directly mixing pearl powder with plastic for coloring, the pearl effect is reduced by about 10%, and the product is also prone to streamline scars and seams. When manufacturing this type of color masterbatch, we take corresponding measures to minimize the temperature, time, and degree of shearing that the color masterbatch undergoes during processing (such as using a single screw granulator instead of a twin screw granulator).

　　Another headache for users with dry coloring is that the hopper of the extruder is not easy to clean. The color powder used for coloring adheres to the inner wall of the material barrel (and even the screw) under the action of wetting agents such as white oil. When it is necessary to change materials, cleaning the material barrel has become a difficult problem for on-site operators, which is time-consuming and material intensive, with twice the effort and half the result. However, using color masterbatch coloring does not have this problem.

　　In addition, using color powder for coloring, as the pigment powder is evenly distributed in the resin to be colored, its dispersibility is good. This conclusion can only be applied to injection molded products, especially thick walled products (blown film and spinning products are another matter). Because pigments are generally not pre treated, it is impossible to ensure that the molecules of the pigment powder fully combine with the colored pigment molecules by only relying on the distance from the extruder inlet, screw, to the outlet, and such a short plasticizing mixing time after mixing with the resin, and there will be a phenomenon of "entrainment". But this "sandwich" phenomenon can be masked in thick walled products, as is evident in blown film and spinning products. So the latter's coloring method still relies mainly on color masterbatch.

　　In addition, due to the different production dates and batch numbers of the manufacturers, there is also a certain degree of color difference in the same brand of color powder. Even if users insist on using the same formula, it is difficult to achieve color consistency between batches of products during the processing process. The color master batch can compensate for the color difference in each batch of color powder through sampling, inspection, and adjustment during the production process. Relatively speaking, The repeatability of color masterbatch is significantly better than that of color powder.

　　Due to the various limitations of using toner for coloring plastic products, it has been challenged by other colorants. However, due to the relatively low production cost, color fixing and matching are not limited in quantity. For small and medium-sized enterprises and private enterprises in developing countries, to participate in fierce market competition, using toner has certain economic benefits, especially for products with single color samples, large production volume, and low color requirements, such as PVC building materials EVA soles and other products are still favored, so toner colorants cannot completely exit the stage.

（2）Color masterbatch coloring characteristics: In order to overcome the various drawbacks of color powder coloring and improve the quality of plastic products, with the continuous development of the plastic industry, the types of plastic resins, additives, plastic product processing equipment and processes continue to innovate and break through, another way of plastic coloring - color masterbatch coloring has been widely adopted, and color masterbatch coloring technology has also been continuously improved in application and practice.

　（1）The so-called color masterbatch refers to the use of a certain process and corresponding equipment, under the action of additives, to mix pigments (or dyes) into the carrier, and through heating, plasticizing, stirring, and shearing, finally fully combine the molecules of pigment powder with those of the carrier resin, and then make particles of similar size to resin particles. We refer to this high concentration colorant as a color masterbatch, and its effect is similar to that of" Saccharin; Similarly, when used, only a small proportion (1% to 4%) needs to be added to the resin to be colored to achieve the purpose of coloring the resin.

　　Compared with color powder coloring, color masterbatch coloring has the following obvious advantages: a. It improves the environmental pollution caused by color powder flying, makes color changing easy during use, and does not require special cleaning of the extruder hopper, making it more convenient.

　　b. Strong targeting and correct color matching. Due to the fact that the color masterbatch manufacturing factory has reasonably selected pigments (dyes), additives, processing equipment, and processing techniques based on the performance of the applicable resin during the manufacturing process, and promptly corrected and supplemented the color differences that may be caused by different batch numbers of color powders during the production process. Inspection will be conducted at the factory to ensure that the colors of the same brand masterbatch and the two batches remain relatively stable.

　　c. Compared with batch resin dry dyeing and granulation before making plastic parts, the use of color masterbatch can reduce the resin performance aging caused by secondary processing of plastic products, which is beneficial for improving the service life of plastic products.

　　The biggest advantage of using color masterbatch is that during the processing, the pigment is fully mixed with the carrier resin under the action of additives. When used, placing it in a certain proportion of the resin to be processed has significantly better compatibility than coloring with toner. Therefore, it is more appreciated by manufacturers of film and spinning products.

　　Of course, the coloring of color masterbatch also has its limitations. Due to the small amount of addition, the processing time of plastic products is short, and the dispersion of color masterbatch is often not as good as that of color powder due to the limitation of the aspect ratio of the extruder screw. If there is an additional manufacturing process, the cost of dyeing will definitely be higher than that of coloring powder. When there is a difference in the performance between the carrier in the color masterbatch and the resin that needs to be colored, the surface of plastic products often shows undispersed spots, color spots, and patterns. Therefore, the use of color masterbatch is limited due to its compatibility and dispersibility.
 

3、Selection of Universal Color Master and Specialized Color Master

Because color masterbatch coloring has many advantages over color powder coloring, with the development of the plastic product processing industry, especially the establishment of numerous joint ventures and the improvement of coloring requirements for export products, color masterbatch coloring has gradually taken a dominant position. In terms of the applicability classification of color masterbatches, they can be divided into universal color masterbatches and specialized color masterbatches.

　　(1) When producing special color masterbatches, the same resin as the intended coloring resin is selected as the carrier, and high concentration pigments (dyes) are added. Under the action of additives, the special color masterbatch is made by heating, plasticizing, mixing, and extruding to produce a dyeing agent specifically suitable for this type of resin, which is called a special color masterbatch. The concentration of specialized color masterbatch can be high or low, with a general addition amount ranging from 1% to 4%.

　　(2)The main difference between a universal color master and a specialized color master is that although a universal color master also uses a certain resin as a carrier, it can be used for coloring other resins besides its carrier resin, hence it is called a universal color master.

　　The so-called universal color masterbatch generally adopts the following measures (some manufacturing factories simply do not use resin as the carrier, but all use high melting point propylene wax as the carrier): first, choose low melting point and high melting index resin as the carrier of the universal color masterbatch, such as PE or EVA; Secondly, the pigment powder ratio in the color masterbatch should be as high as possible, so the universal color masterbatch must be a high concentration color masterbatch, and the usage amount in injection molded products is generally 1%. Due to the limited number of different media carriers in the color masterbatch (usually around 20% after deducting auxiliary factors), when it is diluted with 1% of the resin to be colored, the content of different resins in the plastic product is:0.2kg／100＝2g／kg.In order to enable the universal color master to bind well with other types of resins being colored (with good affinity), other measures have been taken in the universal color master, such as adding more special coupling agents and extending the mixing time, which are beneficial for improving the widespread applicability of the universal color master.

　　(3)Which color masterbatch is the appropriate choice principle? Is universal color masterbatch the most appropriate? Let's analyze from the perspectives of manufacturing factories, distributors, users, economic benefits, convenience, and product effectiveness.

　　From the perspective of manufacturing factories, in order to produce universal color masterbatch, it is necessary to choose pigments with high heat resistance and wide applicability. However, after the temperature resistance level of pigment powder reaches a certain level, the cost of pigments increases by 50% to 100% for every 10 ℃ to20 ℃increase. When a universal color masterbatch is made with a high-temperature resistant pigment and used for coloring high melting point resins, it is used as a material, while when used for low melting point trees like LDPE, it increases residual value.

　　For example, some dyes can be applied to the coloring of hard plastics such as ABS and HIPS, with strong coloring power, no migration, and low cost. The color masterbatch made of them cannot be used in polyethylene products because it will cause severe migration, and universal color masterbatches cannot be used as dyeing materials.

　　Because universal color masterbatch emphasizes universality, it needs to consider other resins, so its material usage is limited. Production costs will inevitably increase, and sales and usage costs will also increase, but it is not absolute. Sometimes, for some users, the cost of using universal color masterbatch will decrease. This is because the use ratio of specialized color masterbatch is 1:25, while the use ratio of universal color masterbatch is 1:100, Then 1kg of universal color masterbatch can be used to offset 4kg of specialized color masterbatch. The manufacturing cost for producing color masterbatch is between 5-15 yuan per kilogram (equipment, color masterbatch quality, color masterbatch variety, and management level vary). By purchasing less than 3kg of color masterbatch, the processing cost is saved by the manufacturer for users. Therefore, even if the price of a universal color masterbatch unit is higher, due to the reduction in usage, the coloring fee per ton of resin is actually cheaper than using a specialized color masterbatch. Some remote distributors and users often prefer universal color masterbatches, which can save thousands of yuan/ton in shipping costs and is also a factor in convenient use. Some small and medium-sized enterprises have received orders with a wide variety of resin varieties, and they need to constantly replace the resin during the production process. In cases where the requirements for coloring are not very strict, purchasing a universal color masterbatch fully demonstrates the advantages of its wide applicability. In addition, purchasing fewer varieties of color masterbatch not only reduces inventory but also makes it easier to sell; From the perspective of color masterbatch manufacturers, in the face of fierce market competition and insufficient orders, we hope to produce more specialized color masterbatches, which not only saves raw material costs but also earns more processing fees.

　　Analyzing from the perspective of coloring effect: Due to the varying degrees of "color eating" among different resins during the coloring process, the same amount of addition can result in different coloring effects, sometimes with significant differences. ABS and HIPS, for example, have strong "color eating power" and poor liquidity. At this point, it is difficult to achieve the desired effect with a universal color master. Conversely, the widespread applicability of a universal color master, although the incompatibility between its carrier resin and the colored resin can be ignored, does not mean that it does not exist at all. Units that produce and use universal color masterbatches face certain pressures, and if there is a slight carelessness in each link, the "implicit" problem will become a "explicit" problem.

　　In addition to the coloring bias mentioned above, due to the small addition ratio and relatively poor dispersibility, plastic products are prone to patterns, color spots, and color spots on the surface, even leading to cracking due to different material types. Especially for large and thin-walled plastic parts with complex shapes, special color masterbatches should be used as much as possible, and low concentration color masterbatches should be selected, Increase the addition amount to improve its dispersibility (special color masterbatch with a ratio of 1:20 or 1:10 can be selected).

Through the above analysis and comparison, we can see that both universal and specialized color masterbatches have their own advantages, but in terms of coloring effect and product performance, specialized color masterbatches are still superior to universal color masterbatches. We suggest that when users have determined the type of resin they want to color, they choose a dedicated color masterbatch first.

Please also ask procurement personnel and process technicians to "shine" your eyes, it is not just a simple low unit price that can bring low product manufacturing costs.

Many times, the plasticization and quality issues reflected in the product have led to the production equipment becoming the "back pot hero". The correct choice of colorants is also a key factor affecting the cost and quality of your product.

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