Obtaining Stable Aqueous Dispersions of Zinc Stearate Particles

Obtaining Stable Aqueous Dispersions of Zinc Stearate Particles

Commercially available zinc stearate particles have particle sizes of between 20 microns and 50 microns that make it difficult to form a stable aqueous dispersion.

The present invention is able to achieve stable aqueous dispersions of zinc stearate particles through an in-situ process. This method is far less expensive, more efficient and easier to operate than conventional methods of obtaining stable zinc stearate dispersions.

A mixture of surfactant(s) and water is formed containing up to about 20% by weight of the zinc stearate particles. The dispersion is then cooled.

After cooling, a metal-containing salt may be introduced to the mixture, preferably a salt that is soluble in water at low temperatures. This reaction may result in the formation of a by-product containing metal-containing stearate, and may be rinsed away from the coated toner particles during subsequent washing procedures due to the by-product's ready solubility in water.

In a preferred embodiment of the invention, the salt may be selected from zinc acetate, zinc chloride or zinc sulfate. Alternatively, the salt may be selected from any other known zinc salt.

Coating of Zinc Stearate on Emulsion Aggregation Toner Particles

The coated toner particles are non-colorant containing white toner particles, and find particular utility as an additive in a developer composition containing additional colorant-containing toner particles. The presence of the zinc stearate-coated toner particles assists in inhibiting the build-up of dirt on the photoreceptor surface.