SEQUENTIAL ADDITION BLENDING FOR COLOR TONER PREPARATION
Original Publication Date: 1997-Oct-31
Included in the Prior Art Database: 2004-Apr-08
Xerox Disclosure Journal
Disclosed is a method for the preparation of color toner comprising blending a lubricant surface additive, for example, zinc stearate on to toner particles for a longer period of time and at higher intensity to sufficiently attached the zinc stearate to the toner surface; and then blending, for example, fumed silica flow aid with the resulting zinc stearate treated toner particles for a shorter time interval and at a lower intensity to retain the triboelectric charging and admix performance characteristics contributed by the fumed silica. Fumed silica flow aids include for example, commercially available materials known as AEROSILS. The zinc stearate, if not sufficiently attached to the toner surface as for example when blended with toner particles for shorter periods of time and or at lower blend intensities, causes filming phenomena on the photoreceptor which has a tendency to reduce the coefficient of friction. The reduced coefficient of friction may cause "image push", that is a subsequent second development step of, for example, a black toner, to disturb the previously developed color image. When the color toner particles are prepared in accordance with the method disclosed herein image push is effectively diminished or eliminated. In an exemplary example, zinc stearate powder in an amount of from about 0.1 to about 3.0 weight percent, and up to about one half of the total AEROSIL to be applied, is added to a color toner and thereafter blended at high intensity for about 5 to about 10 minutes, followed by the addition of the remaining AEROSIL and continued blending at a lower intensity for about 1 to about 5 minutes. High intensity is, for example, about 80 to 100 percent of the available blade speed for a particular blending device, and low intensity is from about 30 to about 70 percent of the available blade speed. The amount of fumed silica employed is from about 0.01 to about 3 weight percent by weight of the toner.