Black masterbatch is produced using carbon black. Raw carbon black is a very difficult and dirty mixture. It is covered with dust, light weight and fluffy. Unless large-scale measures are taken, it will stain the machines and workers and make the work environment dirty. Because of this, foundry workers generally choose a resin carrier, that is, black masterbatch, to complete the pre dispersion of carbon black. This resin carrier is clean, free flowing and easy to use. In addition, carbon black, besides dirty, has another characteristic: it is difficult to carry out dispersion. If the carbon black is melted directly during injection, the coloring effect will be very poor. Carbon black stripes and spots with no dispersion will be visible next to areas with less coloring. Standard injection molding machines can not effectively remove carbon black.
This difficult dispersion property of carbon black also haunted black masterbatch producers. The dispersion of high load black masterbatch produced by single or double screw extruders is very poor. When the final user mixes or moulded the black masterbatch, its performance is only slightly better than that of carbon black, but the effect is equally unsatisfactory. To achieve a stable high dispersion, a high level shear mixer must be used to mix carbon black, such as FCM or BANBURY mixture. With sufficient strength, these mixers can completely mix carbon black and base resin. The type of carbon black used also affects the dispersivity. The smaller the carbon black particles, the more difficult the dispersion will be.
The application of thin wax is the most demanding of dispersion. The final product of black masterbatch with poor dispersion can be easily seen by the naked eye from the edges and corners. In addition to the lack of aesthetics, the poor dispersion of carbon black in the film significantly reduces the weathering resistance of the black film. Fine particles with good dispersion are the main characteristics of the fiber industry, which are used in ropes, yarns, carpets and other industries. Large machines produce 30000 strands of fibers at a speed of more than 5000 meters per minute. If the dispersion of the black masterbatch is too poor, it will break the fiber and cause the production to stop.