Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-01-22
2001-04-03
Zitomer, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S832000, C524S836000, C526S079000, C430S104000, C430S137170, C430S904000
Reexamination Certificate
active
06211287
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is generally directed to free radical initiated monomer polymerization processes for the formation of resin particles. More specifically, the present invention is directed to polymerization processes wherein monomer polymerization and particle aggregation can be achieved simultaneously under controlled monomer excess feed or “flood” feed conditions to provide monodisperse resin particles and resin particle aggregates thereof with a volume average diameter size range of, for example, from about 1 to about 10 micrometers.
The composition and processes of the present invention enable, in embodiments: emulsifier free emulsion polymerization processes; monodisperse resin particles or resin particle aggregates within an average diameter size range of, for example, from about 1 to about 3 micrometers; monodisperse resin particles or resin particle aggregates with geometric particle size distributions below about 1.05, for example, of from about 1.01 to about 1.02, and d
w
/d
n
values less than about 1.01; resin particles and particle aggregates which are suitable for use in dry and liquid developers and toner for printing applications; and resin particles and resin particle aggregates which can be grown, or increased in size if desired, to larger average particle sizes.
There are known methods for directly preparing resin particles from monomers, including dispersion polymerization, encapsulation, emulsion polymerization, and emulsion-aggregation. The product particles generally may be optionally colored during or subsequent to particle formation to afford “in-situ” or “chemical” toners. These methods possess unique advantages and disadvantages including: cost; ease of use; product contamination and purification considerations; environmental and waste concerns; reliability in producing product particles with desired physical or chemical properties, such as particle size range, particle size distribution, color, surface roughness or smoothness, particle-particle flowability, blocking temperature, melt flow rheology, chargability, conductivity, and the like characteristics.
The present invention provides, in embodiments, flood feed free radical polymerization processes which can conveniently afford well defined larger sized aggregated resin particles, greater than, for example, about 0.5 microns, for example, from about 1 to about 20, and preferably from about 1 to about 10 microns, and which resin particles are believed to arise from concurrent surfactant-free monomer polymerization and controlled particle aggregation.
The aforementioned and other advantages are achievable with the resin particles compositions and processes of the present invention. The compositions and processes of the present invention are useful in many applications including printing, for example, ink jet and electrostatographic such as in xerographic printers and copiers, including digital systems.
PRIOR ART
U.S. Pat. No. 5, 219,943, issued Jun. 15, 1993, and U.S. Pat. No. 4,935,469, issued Jun. 19, 1990, both to Akasaki et al., disclose processes for producing mondispersed fine particles of a vinyl polymer comprising polymerizing monomers containing at least one vinyl monomer, and a methacrylic ester in the presence of a surface active agent, a persulfate polymerization initiator, and a divalent metal as an electrolyte. Monodispersed vinyl polymer fine particles having a particle size of one micrometer or greater with a very narrow size distribution can be obtained.
U.S. Pat. No. 5,455,315, commonly owned and assigned, issued Oct. 3, 1995, to Paine et al., discloses an in situ process for the preparation of resin particles comprising: preparing a seed particle latex by aqueous emulsion polymerization of a first mixture comprised of at least one monomer, an optional chain transfer agent, and a water soluble free radical initiator, wherein the reaction of the free radical initiator and monomer produces oligomeric radicals which provide in situ stabilization to the resulting first generation seed particles; optionally diluting the first seed particle latex with water; heating and starve feed adding to the first generation seed particles a second mixture comprised of at least one monomer, an organic soluble free radical initiator, an optional chain transfer agent, an optional water soluble free radical initiator, and an optional surfactant to form a third mixture comprised of second generation seed particles; heating and starve feed adding to the second generation seed particles additional said second mixture to form a fourth mixture comprised of third generation seed particles; heating and starve feed adding to the third generation seed particles additional said second mixture to form a fifth mixture comprised of fourth generation seed particles; and heating and starve feed adding to the fourth generation seed particles additional said second mixture to form a sixth mixture comprised of fifth generation seed particles.
The aforementioned patents are incorporated in their entirety by reference herein.
There remains a need for an inexpensive, efficient, and environmentally acceptable methods for the preparation of resin particles with, for example, well defined particle size and size distribution properties, and imaging processes thereof.
SUMMARY OF THE INVENTION
Embodiments of the present invention, include:
overcoming, or minimizing deficiencies of prior art processes, by providing semi-continuous emulsion polymerization processes;
providing continuous emulsion polymerization processes comprising adding a mixture of at least one free radical reactive monomer continuously to a heated aqueous solution of a water soluble free radical initiator and a water soluble salt to form latex emulsion particles and aggregates thereof; and wherein the rate of continuous addition of the monomer is greater than the rate at which monomer is consumed by polymerization;
providing continuous emulsion polymerization processes wherein resin particle growth and resin particle aggregation controllably occur simultaneously to afford particulate products with well defined particle size and size distribution properties;
continuous emulsion polymerization processes wherein flood feeding of the monomer or monomers to the polymerization reaction mixture overcomes the nucleation limiting 0.5 micron particle size barrier;
providing polymerization processes wherein the total number of resin particles, for example, seed particles initially formed in the nucleation stage and their progeny, can be chemically compelled to continuously decrease (in number) over the course of the monomer polymerization via controlled resin particle aggregation phenomena with the result that monodisperse resin particles and resin particle aggregates thereof, on the order of from about 1 to about 3 microns, can be obtained in a single step;
providing polymerization processes wherein the resulting resin particles or resin particle aggregates can optionally be grown to larger particle sizes by a subsequent monomer addition stage or stages; and
providing polymerization processes wherein the resulting resin particles or resin particle aggregates thereof can optionally be colored either during or after particle formation and aggregation to provide colored particles which are useful in dry and liquid marking materials.
REFERENCES:
patent: 5455315 (1995-10-01), Paine
Paine Anthony J.
Rudin Alfred
Vlad Florin
Haack John L.
Xerox Corporation
Zitomer Fred
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