Abstract: A method of coloring thermoplastic olefin resins and pulverizing resin pellets in a single step involving the steps of metering liquid coloring onto resin pellets and then passing the combination of liquid color and resin pellets into a mill blender. The liquid color is metered onto the plastic pellets at a rate of from less than 0.2% to less than 1.0% by weight of the plastic pellets. The mill blender receives the combination of plastic pellets and liquid color and pulverizes the mixture to produce a colored thermoplastic resin powder that is suitable for subsequent processing, such as roto-molding or slush-molding.

Abstract: An apparatus for blending polymer powder and pigment inside of a blender that heats the polymer through agitation of the blending process. The apparatus includes a control scheme that monitors the condition of the powder and discharges the powder from the blender just before the powder reaches its melting point. The apparatus monitors the flowability of the powder as well as the temperature. As an additional method of controlling the temperature inside of the blender, the blending speed can be varied by virtue of a variable speed motor that is attached to the blender.