The quality of the black masterbatch depends on the following factors: dispersion, coverage, rheology, compatibility, stability, and lightness and darkness.
Black masterbatch is produced using carbon black. Raw carbon black is a very difficult and dirty mixture, it is dusty, light and fluffy. Unless large-scale treatment measures are adopted, it will contaminate the machines and workers and make the working environment dirty. Because of this, casters generally choose to complete the pre-dispersion of carbon black on a resin carrier, that is, black masterbatch. This resin carrier is clean, free flowing and easy to use. In addition, besides being dirty, carbon black has a characteristic that it is difficult to disperse. If the raw carbon black is directly melted during injection molding, the coloring effect will be very poor. Non-dispersive carbon black stripes and speckled areas will be clearly visible if they are next to less colored areas. Standard injection molding machines cannot effectively disperse carbon black.
The performance of carbon black, which is difficult to disperse, also plagues coloring masterbatch manufacturers. High-load black masterbatch produced by single or double screw extruder has very poor dispersion. When the end user mixes or molds these black masterbatch, its performance is only slightly better than carbon black, but the effect is also unsatisfactory. In order to achieve a stable and high dispersion, a high-level shear mixer must be used to mix carbon black, such as FCM or BANBURY. With sufficient strength, these mixers can mix carbon black and base resin completely. The type of carbon black used also affects color dispersion. The smaller the carbon black particles, the harder the dispersion.
The application of thin wax is the most demanding for dispersion. The final product of the masterbatch with poor dispersion can be easily seen from the corners. In addition to lack of aesthetics, the poorly dispersed carbon black in the film significantly reduces the weatherability of the black film. Small particles with good dispersion are the main characteristics of the fiber industry. These fibers are used in rope, yarn, carpet and other industries. Large machines produce 30,000 strands of fine fibers at a speed of more than 5000 meters per minute. If the dispersion of the masterbatch is too poor, it will break the fiber and cause production shutdown.
The second factor that determines the quality of black masterbatches is the coverage. This factor is particularly important for masterbatches used in waste or recycled polymers. In these cases, the role of black is to cover other colour. The large particle carbon black has poor coloring ability, and it is not easy to cover all other colors in the lower layer. As a result, the final product only gets the deviated color. In the melting process, the ability to correctly select the carbon black with high coloring ability to cover the existing color is called the covering power.
The third factor determining the quality of the black masterbatch is rheology and fluidity. If a masterbatch itself has good dispersion, but it cannot flow into the material to be molded, the production effect is not ideal. Generally speaking, the base resin used to produce the masterbatch has a high rheology. In order to save costs, some masterbatch producers use recycled materials, waste materials or recycled materials as resin carriers. The flowability of the masterbatch produced in this way will be significantly reduced. If the rheology is not good, the mold union will have troubles in cycle time and appearance treatment. It is worth noting that if the dispersion and rheology are not high, some end users will make up for it by increasing the dilution ratio, but this approach will only increase the cost of the masterbatch. The masterbatch with the smallest dilution ratio can produce a uniform, well-dispersed black.
The fourth factor in determining the quality of the black masterbatch is compatibility. If the masterbatch is produced using chips or recycled materials, it may contain contaminants or other non-meltable polymers. This will cause some unpredictable and difficult constraints, wasting time and raw materials for the final consumer. At this time, the primer resin can be used to produce high-quality masterbatch, the masterbatch has good compatibility during the melting process. High-quality masterbatch can be produced using LLDPE, LDPE, HDPE, PP, PS, SAN, PA and other materials. If engineering grades and strict physical properties have been noted, special polymer masterbatches can be obtained. Several large-scale international masterbatch manufacturers are conducting research to produce so-called "global" masterbatch. These masterbatch can be widely used in other raw materials, have good rheology, and can be used flexibly.
In today's international economy, it is absolutely necessary for international customers to have high requirements on the quality of masterbatch and the stability of raw materials. This is also the fifth factor that determines the quality of black masterbatch. A main performance of stability is the stable carbon black ratio. If the percentage of carbon black fluctuates, then the amount of masterbatch that needs to be melted is not the same, and it is impossible to produce products of the same color tone. Some final producers report that the dilution ratios required by chemical manufacturers usually vary by 5-8%, depending on how much material the masterbatch manufacturer puts into production. Obviously this is unacceptable. Of course, other factors such as the fluidity and dispersion of the injected melt should be consistent with the amount of each batch.
Brightness and darkness
The final factor that determines the quality of the black masterbatch is the lightness and darkness of the color. There are various types of carbon black on the market that can be used for coloring masterbatch, but the colors and prices are also very different. The large-particle carbon black has a lower coloring degree and different background colors than the small-particle carbon black. Large-grain masterbatch is suitable for the production of films such as garbage bags, but it is not suitable for the production of products that pay attention to aesthetics, such as TV signs or places where UV protection is required, such as agricultural films or external pipes. For these products, only small particles of carbon black, which are more expensive, are used. In addition, low transparency is also a characteristic of small particles of carbon black.
Classification and application scope of ordinary carbon black
SRF carbon black is generally used in the production of garbage bags that do not require strong coloring power, high coverage or UV protection. The color tends to be grayish blue, the price is cheap, and it is relatively easy to disperse, so those small manufacturers of masterbatch only equipped with single or double screw extruders will choose this carbon black. The particle size of HAF carbon black is half that of SRF carbon black particles, but the coloring strength is twice. It is brownish red, its UV protection ability is obviously stronger than SRF carbon black, and the cost is lower than P carbon black. It has good coverage and can be applied in many ways. P carbon black is suitable for anti-ultraviolet applications and in the food industry and is red and blue. JET carbon black has the most satisfactory color brightness and dark, shiny black. Its particles are the smallest, but they are not susceptible to dispersion. Only those manufacturers equipped with high-efficiency shear mixers can achieve uniform dispersion when using JET carbon black. It is also the most expensive of ordinary carbon black. The cost comparison shows that the more expensive masterbatch can get better production effect economically than the cheaper masterbatch.
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