The dispersant needs to have good compatibility with the resin and good affinity with the pigment, which can help the pigment to disperse uniformly and no longer agglomerate.
①Polyethylene wax. The dispersion requirements of film pigments are close to those of chemical fibers, so the selection of polyethylene wax in the formulation of polypropylene chemical fiber grade masterbatches can refer to the description of the selection of dispersants in the section on the formulation of blown film masterbatches.
②Polypropylene wax. The compatibility of polypropylene wax and polypropylene resin is good in both microscopic and macroscopic aspects. The suitability of polyethylene waxes for polypropylene fibers is correspondingly limited, especially for fine denier and BCF filaments, where polypropylene waxes tend to be preferred over polyethylene waxes. Since polyethylene waxes have a significantly lower melting point than PP or polypropylene waxes, the different melting properties of the two polymers are difficult to handle. During drawing and heat setting of the as-grown polypropylene fibers, the crystalline structure of the fibers changes. In the subsequent heat treatment temperature, which was carried out at about 130°C, it was clearly found that this temperature was well within the melting temperature range of the polyethylene wax. As a result of the change in the crystalline structure of the polypropylene primary fibers, molten (and thus liquid) polyethylene wax seeps from the polypropylene matrix onto the fiber surface, not only pure wax but also pigments are brought to the surface. As with polymerized polypropylene waxes are compatible with the polymer components, exhibit a very similar melting behavior, and melt at about the same temperature.
There are two kinds of polypropylene waxes polymerized by metallocene catalysis technology, one is homopolypropylene wax, the melting point is 140~160℃;
The other is copolymerized polypropylene wax, the melting point is usually 80~110℃.
From the perspective of dispersion theory, in the pigment wetting stage, the wetting of the low-viscosity wax occurs quickly, and the wetting efficiency is higher. However, in the latter stage of extrusion and granulation, it is hoped that the wax has a corresponding viscosity, and the shear force is well transferred between the pigment and the resin melt, so that the wetted pigment can be evenly distributed in the resin melt. . At this time, we can consider combining low-melting polypropylene wax with high-viscosity polypropylene wax to achieve satisfactory dispersion.
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