Emulsion polymerization processes and toners thereof

DETAILED DESCRIPTION OF THE INVENTION Emulsion polymerization and monodisperse toner particle formation processes of the present invention employ starve feed emulsion polymerization (SFEP) to accomplish the synthesis of successive generations of seed particles.
Seed particles are subsequently grown or enlarged in a series of starve fed polymerizations to give final particles of about 2 to about 8 microns with very narrow or monodisperse particle size distributions.
During a starve fed polymerization, a feed mixture containing monomer(s), initiator(s), and optional surfactant(s), and optional chain transfer agent(s), is added at a relatively slow and constant rate of about 0.
1 gram per kilogram of reactor content per minute to about 25 grams per kilogram of reactor content per minute.
Starved conditions occur when the monomer is consumed by polymerization at about the same rate as it is added, most preferably in the range of about 1 gram per kilogram of reactor content per minute to about 10 grams per kilogram of reactor content per minute to the emulsion polymerization reaction.
Pigments, dyes, carbon black or magnetite colorants can be added at any stage of the process, or the final resin particles may be colored by known post particle coloration processes.
Since certain aforementioned colorants, such as carbon black, may interfere with free radical polymerization processes, the colorants may be optionally surface treated with passivating compounds or coatings prior to the coloration step.
Emulsion polymerizations of the present invention are conducted in aqueous media containing an optional suitable surfactant, monomer droplets or previously formed monodisperse resin particles, and typically either a water soluble initiator or monomer soluble initiator or both.
In some cases an optional small amount of previously prepared "seed" particles may be employed to improve the reproducibility and degree of control of the polymerization reaction.
In other seeded reactions, monomer addition may be controlled to prevent the formation of separate or "secondary" monomer droplets while promoting the swelling of existing particles