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In the last article, we learned the characteristics and application of polyethylene wax as one of the color masterbatch dispersants. In this article today, we will continue to understand the amount of polyethylene wax. In addition, another dispersant - polypropylene wax will be introduced.
Amount of polyethylene wax
As a dispersant in the color master batch formula, the best dispersion of pigment depends on the following three factors: the dispersibility of pigment itself, the shearing ability of efficient equipment, and the type and amount of wax used for dispersant.
So how much is appropriate? Whether more is better depends on the oil absorption value of pigments and the processing technology of color masterbatch.
(1) The amount of polyethylene wax added is related to the nature of pigment, and the amount of polyethylene wax added is related to the difficulty of pigment dispersion. Obviously, when the type of polyethylene wax is determined, the amount of polyethylene wax added should be determined according to the difficulty of pigment dispersion. Generally speaking, inorganic pigments have a large proportion, the original particle size is large, and they are easy to disperse, so the amount of addition is generally small, while organic pigments are smaller than the original particle size, and the specific surface area is large, so the relative amount of addition is large.
(2) The amount of polyethylene wax added is related to the processing technology of color masterbatch. At present, the processing of color masterbatch mainly includes high-mixing twin-screw extrusion and internal mixing method, and the internal mixing method includes intermittent and continuous single-rotor mixing internal mixer and continuous double-rotor mixing internal mixer. Generally speaking, the addition of polyethylene wax in the high mixing twin-screw extrusion process is relatively higher than that in the internal mixing process. Even the process characteristics of the internal mixing process determine that the dispersible and high-quality color masterbatch products can be prepared without polyethylene wax, especially the black color masterbatch which is difficult to disperse.
(3)When the type and quantity of polyethylene wax are determined, attention should be paid to the determination of processing conditions in order to obtain the best dispersion of pigment. When the pigment particles are dispersed, the motion force transmitted by the processing machinery through the melt in different ways also plays a great role in accelerating the wetting and penetration of the pigment particles. For polyethylene wax varieties with different specifications, it is particularly important to select appropriate wetting temperature and wetting promotion method according to their characteristics. In short, wetting requires energy (thermal or mechanical energy).
Characteristics and selection principles of polypropylene wax
We have introduced the wetting and dispersing effects of polyethylene wax. Practice has proved that polyethylene wax with low viscosity is more beneficial as a dispersing agent. They can quickly and effectively wet and coat the surface of the pigment and the interior of the aggregate. This weakens the strong adhesive force inside the aggregate, so it is easy to disperse the aggregate by using weak shear. Once the aggregate is dispersed, the wax will cover the free surface and stabilize the dispersion. According to the law of capillary effect, it is easy to understand the different characteristics of high-viscosity and low-viscosity liquids. Low-viscosity polyethylene wax is more effective as a wetting agent in a certain period of time. They can even reach the pigment primary particles that are difficult to stay in high-viscosity plastic polymers. Therefore, polyethylene wax and polypropylene wax are the first choice for the pigment dispersion additives.
However, the applicability of polyethylene wax in polypropylene fiber spinning is limited for polypropylene fiber. Polypropylene wax is often preferable to polyethylene wax for ordinary filaments and high-quality fibers, especially for soft wool-like fine denier and BCF filaments suitable for floor covering and textile outerwear. This is because polypropylene and polyethylene are very difficult to mix uniformly due to their incompatibility of polymers, which will lead to phase separation. Secondly, because the melting point of polyethylene wax is significantly lower than that of polypropylene or polypropylene wax, it is difficult to deal with the different melting characteristics of these two polymers. The unevenness and inappropriate rheology of the product may lead to spinning process breakage, which may worsen the physical textile properties of the fiber due to these negative effects.
In addition, when polypropylene fiber is stretched and heat set, the temperature of heat treatment (usually about 130 ℃) can clearly be found that this temperature is just within the melting temperature range of polyethylene wax. Due to the change of crystal structure of polypropylene primary fiber, it can be observed that molten polyethylene wax seeps from the polypropylene matrix to the fiber surface, and not only pure wax, but also pigment will be brought to the surface.
For the color masterbatch of polypropylene fiber, the use of polypropylene wax is the only way to achieve good results and meet the highest requirements technically and economically, with excellent thermal stability; The wetting and dispersing effect of pigment is high; It reduces the blockage of filter and spinneret, reduces fiber breakage, especially for carpet fiber, and does not damage the recovery performance after compression (very important for carpet fiber).
For more details, please consult us!
Qingdao Sainuo Chemical Co.,Ltd. We are manufacturer for PE wax, PP wax, OPE wax, EVA wax, PEMA,EBS,Zinc/Calcium Stearate…. Our products have passed the REACH, ROHS, PAHS, FDA testing.
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