Aggregation processes

Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Process of making developer composition

Reexamination Certificate

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C430S137170, C523S335000

Reexamination Certificate

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06309787

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention is generally directed to colorant and toner processes, and more specifically, to processes which utilize aggregation and coalescence, or fusion of a latex, colorant, such as pigment, dye, or mixtures thereof, and optional additive particles. In embodiments, the present invention is directed to processes which provide toner compositions with a volume average diameter of from about 1 micron to about 25 microns, and preferably from about 2 microns to about 12 microns, and a narrow particle size distribution of, for example, about 1.10 to about 1.45 as measured by the Coulter Counter method. The resulting toners can be selected for known electrophotographic imaging and printing processes, including digital color processes.
The present invention in aspects thereof is directed to a process for the preparation of toners by mixing polymer encapsulated colorant particles and colorant particles, and more specifically, by blending an aqueous colorant, such as a pigment dispersion containing an ionic surfactant with a miniemulsion latex emulsion comprised of monomer particles, preferably submicron in size, of from, for example, about 100 nanometers to about 1,000 nanometers and preferably from about 200 nanometers to about 600 nanometers in volume average diameter, a nonionic surfactant and an ionic surfactant of opposite charge polarity to that of the ionic surfactant in the colorant dispersion, heating to accomplish polymerization of the monomer, thereafter heating the resulting mixture at, for example, below about the polymer glass transition temperature, and more specifically, from about 35° C. to about 60° C. (Centigrade) to form toner sized aggregates of from about 2 microns to about 20 microns in volume average diameter, and which toner is comprised of polymer, colorants, and optional additive particles, followed by heating the aggregate suspension above about the resin, or polymer glass transition temperature, and more specifically, at, for example, from about 70° C. to about 100° C. to effect coalescence or fusion of the components of the aggregates and to form mechanically stable integral toner particles. The miniemulsion contains, for example, a latex of water, polymer or resin, and colorant, oil, or monomer, water, surfactants, and preferably a cosurfactant, such as an alcohol, an alkane, an ether, an alcohol ester, an amine, a halide, or a carboxylic acid ester, which cosurfactant is preferably inert, nonvolatile, water insoluble, and is a liquid at a temperature of, for example, from about 40° C. to about 90° C., and contains a terminal aliphatic hydrocarbyl group with at least about 10 carbon atoms, and more specifically, from about 12 to about 24 carbon atoms, and mixtures thereof, and more specifically, an aliphatic alcohol with at least about 8 carbon atoms, such as from about 10 to about 25 carbon atoms, and an alkane with from about 10 to about 30 carbon atoms. The cosurfactant primarily functions to reduce the diffusion of monomer out of the monomer droplet and enables relatively stable miniemulsions since, it is believed, there is formed intermolecular complexes at the oil/water interface. The complexes are believed to be liquid condensed and electrically charged thus creating a low, for example from about 0.5 dyne/centimeter to about 5 dyne/centimeter interfacial tension and high resistance to droplet coalescence.
With the present invention in embodiments, there is selected a colorant encapsulated with polymer generated by miniemulsion polymerization process. Aggregation/coalescence of these colorant encapsulated polymer particles with colorant particles permit, for example, the generation of a wide range of colored toner compositions with, for example, high colorant loading, narrow particle size distribution, and excellent projection efficiency. Other advantages in embodiments include, for example, (1) better particle dispersion in the resin matrix; (2) improved mechanical properties; (3) protection of the colorant from outside influences during toner processing; and (4) protection of the matrix or toner resin from interaction with the colorant.
The aforementioned toners are especially useful for imaging processes, especially xerographic processes, which usually require high toner transfer efficiency, such as those having a compact machine design without a cleaner, or those that are designed to provide high quality colored images with excellent image resolution, improved signal-to-noise ratio, and image uniformity.
PRIOR ART
There is illustrated in U.S. Pat. No. 4,996,127 a toner of associated particles of secondary particles comprising primary particles of a polymer having acidic, or basic polar groups and a coloring agent. The polymers selected for the toners of the '127 patent can be prepared by an emulsion polymerization method, see for example columns 4 and 5 of this patent. In column 7 of this '127 patent, it is indicated that the toner can be prepared by mixing coloring agent and optional charge additive with an emulsion of the polymer having an acidic or basic polar group obtained by emulsion polymerization. In U.S. Pat. No. 4,983,488, there is disclosed a process for the preparation of toners by the polymerization of a polymerizable monomer dispersed by emulsification in the presence of a colorant and/or a magnetic powder to prepare a principal resin component and then effecting coagulation of the resulting polymerization liquid in such a manner that the particles in the liquid after coagulation possess diameters suitable for a toner. It is indicated in column 9 of this patent that coagulated particles of 1 to 100, and particularly 3 to 70, are obtained. This process is thus directed to the use of coagulants, such as inorganic magnesium sulfate, which results in the formation of particles with a wide particle size distribution. Similarly, the aforementioned disadvantages, for example poor particle size distributions are obtained hence classification is required resulting in low toner yields, are illustrated in other prior art, such as U.S. Pat. No. 4,797,339, wherein there is disclosed a process for the preparation of toners by resin emulsion polymerization, wherein similar to the '127 patent certain polar resins are selected, and wherein flocculation as in the present invention is not believed to be disclosed; and U.S. Pat. No. 4,558,108, wherein there is disclosed a process for the preparation of a copolymer of styrene and butadiene by specific suspension polymerization.
In U.S. Pat. No. 5,561,025, the disclosure of which is totally incorporated herein by reference, there are illustrated emulsion/aggregation/coalescence processes wherein water phase termination agents, that is chain transfer agents that are not water miscible are selected.
Other prior art that may be of interest includes U.S. Pat. Nos. 3,674,736; 4,137,188 and 5,066,560.
Emulsion/aggregation processes for the preparation of toners are illustrated in a number of Xerox patents, the disclosures of each of which are totally incorporated herein by reference, such as U.S. Pat. No. 5,290,654, U.S. Pat. No. 5,278,020, U.S. Pat. No. 5,308,734, U.S. Pat. No. 5,370,963, U.S. Pat. No. 5,344,738, U.S. Pat. No. 5,403,693, U.S. Pat. No. 5,418,108, U.S. Pat. No. 5,364,729, and U.S. Pat. No. 5,346,797; and also of interest may be U.S. Pat. Nos. 5,348,832; 5,405,728; 5,366,841; 5,496,676; 5,527,658; 5,585,215; 5,650,255; and 5,650,256.
Processes for the preparation of spherical toners at coalescence temperatures of from about 100° C. to about 120° C. are illustrated in U.S. Pat. No. 5,501,935, the disclosure of which is totally incorporated herein by reference.
The appropriate components and processes of the above patents may be selected for the processes of the present invention in embodiments thereof.
SUMMARY OF THE INVENTION
It is a feature of the present invention to provide toner processes with many of the advantages illustrated herein.
In another feature of the present invention there are provided simple and economical processes for t

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