ABSTRACT
A variety of additive dispersions are used for the modification and improvement of plastics and synthetic fibers, to impart light stability or flame retardancy or to achieve reinforcement, for example. Perhaps the most important role of additive dispersions, however, is to introduce the color required for product identification, safety, aesthetics, or decoration. The ingredients of the dispersion are premixed to ensure homogeneous distribution of all components. As solid dispersions usually contain high amounts (10-70 percent) of pigment powder, a satisfactory premix is obtained only if the binder is also added in powder form. A practical method to judge the quality of dispersions for Polyvinyl chloride is the observation of the "calendering effect." Liquid color dispersions are offered for polyolefins, usually as part of a package, which may include suitable metering pumps and control systems. The achievement of fiber-grade quality pigment dispersions requires the use of an efficient melt-filtration system during concentrate production.
