As a dispersant in the masterbatch formulation, the best dispersion of pigment depends on the following three factors: the ease of dispersion of the pigment itself; the shearing capacity of the equipment; and the variety and amount used for the dispersant. How much is appropriate to add, and whether more is better, is related to the oil absorption value of the pigment and the masterbatch processing process.
①The amount of polyethylene wax added is related to the nature of pigment. It is obvious that when the variety of polyethylene wax is determined, its addition amount should be based on the difficulty of pigment dispersion. Generally speaking, inorganic pigments have large relative density, large original particle size and easy to disperse, so the addition amount is generally small, while organic pigments have small original particle size and large specific surface area, so the relative addition amount is large.
②The amount of polyethylene wax added is related to the masterbatch processing technology. At present, the color masterbatch processing mainly has high mixed twin-screw extrusion and dense refining method, dense refining method has gap type and continuous single rotor mixing dense refining machine and continuous double rotor mixing dense refining machine. Generally speaking, the amount of polyethylene wax added by the high-mix twin-screw extrusion process is relatively higher than that of the dense refining process, and even the process characteristics of the dense refining method determine that it can produce well-dispersed, high-quality masterbatch products without adding polyethylene wax, especially the black masterbatch which is difficult to disperse.
③After the variety and quantity of polyethylene wax is determined, in order to obtain the best dispersion of pigments, attention should be paid to the determination of the processing conditions. When the pigment particles are dispersed, the processing machinery conducts the force through the melt in different ways, which also plays a great role in accelerating the wetting and penetration of the pigment particles. For different sizes of polyethylene wax varieties, it is particularly important to choose the appropriate wetting temperature and wetting promotion according to their characteristics. In short, wetting requires energy (thermal or mechanical).
Polyethylene wax is a polymer wax or PE wax for short. As a fine chemical material, polyethylene wax is widely used in plastic and rubber processing and in the production of coatings and inks. Polyethylene wax is compatible with polyethylene and polypropylene, and can improve the fluidity of polyethylene, polypropylene and ABS and the demoulding of polymethyl methacrylate and polycarbonate. In PVC processing, compared with microcrystalline wax, polyethylene wax has stronger external lubrication effect. In addition, polyethylene wax can also be used in inks, coatings, paper and hot melt adhesives.
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