Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Process of making developer composition
Reexamination Certificate
2000-09-07
2001-04-03
Martin, Roland (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Process of making developer composition
Reexamination Certificate
active
06210853
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to toner processes, and more specifically to the preparation of a surfactant free latex wherein resin particles contained therein are aggregated and coalesced with a colorant to provide toner compositions. In particular, the present invention relates to a surfactant free toner process wherein the process involves the preparation of an latex emulsion preferably containing submicron resin particles suspended in an aqueous phase which is surfactant free, (ii) preparing by polycondensation a second resin which resin is readily dispersable in warm water to provide a dispersion of submicron particles in the size range of for example, about 50 to about 300 nm, wherein this dispersion is then used as a dispersant for the colorant particles to provide a stable colorant or colorant dispersion followed by aggregation and coalescence with the latex emulsion of (i) to provide a toner composition. The resin utilized to stabilize the colorant, such as pigment particles is for example, a sodio sulfonated polyester resin and which resin is capable of self dispersing in warm water providing a submicron particle size dispersion. More specifically the processes of the present invention can select dual coagulants such as an inorganic cationic metal salt and an organic cationic coagulant to facilitate aggregation of resin and colorant, such as pigment particles, both which are in the size range of about 80 to about 400 nanometers in size and optionally the use of a release agent such as a wax and a charge control agent. With further respect to the processes of the present invention is the staged raising of the temperature during coalescence wherein two or more temperature steps are conducted to reach the coalescence to for example retain the toner particle size distribution, followed by a staged changing of the pH of the aggregate mixture wherein the pH is lowered in two or more sequences to for example, provide toner process which are surfactant free .
PRIOR ART
In forming toner compositions for use with reprographic or xerographic print devices, emulsion aggregation processes are known. For example, emulsion/aggregation/coalescing processes for the preparation of toners are illustrated in a number of Xerox patents, the disclosures 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. 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, 5,650,256 and 5,501,935.
In addition, the following U.S. Patents the disclosures of which are incorporated herein by reference in their entireties relate to emulsion aggregation processes for the forming of toner compositions. U.S. Pat. No. 5,922,501 describes a process for the preparation of toner comprising blending an aqueous colorant dispersion and a latex resin emulsion, and which latex resin is generated from a dimeric acrylic acid, an oligomer acrylic acid, or mixtures thereof and a monomer; heating the resulting mixture at a temperature about equal, or below about the glass transition temperature (Tg) of the latex resin to form aggregates; heating the resulting aggregates at a temperature about equal to, or above about the Tg of the latex resin to effect coalescence and fusing of the aggregates; and optionally isolating the toner product, washing, and drying.
U.S. Pat. No. 5,945,245 illustrates a surfactant free process for the preparation of toner comprising heating a mixture of an emulsion latex, a colorant, and an organic complexing agent.
U.S. Pat. No. 5,403,693 illustrates a process for the preparation of toner compositions with controlled particle size comprising: (i) preparing a pigment dispersion in water, which dispersion is comprised of a pigment, an ionic surfactant in amounts of from about 0.5 to about 10 percent by weight of water, and an optional charge control agent; (ii) shearing the pigment dispersion with a latex mixture comprised of a counterionic surfactant with a charge polarity of opposite sign to that of said ionic surfactant, a nonionic surfactant, and resin particles, thereby causing a flocculation or heterocoagulation of the formed particles of pigment, resin, and charge control agent; (iii) stirring the resulting sheared viscous mixture of (ii) at from about 300 to about 1,000 revolutions per minute to form electrostatically bound substantially stable toner size aggregates with a narrow particle size distribution; (iv) reducing the stirring speed in (iii) to from about 100 to about 600 revolutions per minute, and subsequently adding further anionic or nonionic surfactant in the range of from about 0.1 to about 10 percent by weight of water to control, prevent, or minimize further growth or enlargement of the particles in the coalescence step (iii); and (v) heating and coalescing from about 5 to about 50° C. about above the resin glass transition temperature, Tg, which resin Tg is from between about 45° C. to about 90° C. and preferably from between about 50° C. and about 80° C. the statically bound aggregated particles to form a toner composition comprised of resin, pigment and optional charge control agent.
U.S. Pat. No. 5,482,812 illustrates a process for the preparation of toner compositions or toner particles comprising: (i) providing an aqueous pigment dispersion comprised of a pigment, an ionic surfactant, and optionally a charge control agent; (ii) providing a wax dispersion comprised of wax, a dispersant comprised of nonionic surfactant, ionic surfactant or mixtures thereof; (iii) shearing a mixture of the wax dispersion and the pigment dispersion with a latex or emulsion blend comprised of resin, a counterionic surfactant with a charge polarity of opposite sign to that of said ionic surfactant and a nonionic surfactant; (iv) heating the above sheared blend below about the glass transition temperature (Tg) of the resin to form electrostatically bound toner size aggregates with a narrow particle size distribution; (v) adding additional ionic surfactant to the aggregated suspension of (iv) to ensure that no, or minimize additional particle growth of the electrostatically bound toner size aggregates occurs on further increasing the temperature to coalesce the aggregates into toner particles (vi); (vi) heating the mixture of (v) with bound aggregates above about or at the Tg of the resin; and optionally (vii) separating the toner particles from the aqueous slurry by filtration and thereafter optionally washing.
U.S. Pat. No. 5,622,806 illustrates a process for the preparation of toner compositions with controlled particle size comprising: (i) preparing a pigment dispersion in water, which dispersion is comprised of a pigment, an ionic surfactant in amounts of from about 0.5 to about 10 percent by weight to water, and an optional charge control agent; (ii) shearing the pigment dispersion with a latex mixture comprised of a counterionic surfactant with a charge polarity of opposite sign to that of said ionic surfactant, a nonionic surfactant, and resin particles, thereby causing a flocculation or heterocoagulation of the formed particles of pigment, resin, and charge control agent; (iii) stirring the resulting sheared viscous mixture of (ii) at from about 300 to about 1,000 revolutions per minute to form electrostatically bound substantially stable toiler size aggregates with a narrow particle size distribution; (iv) reducing the stirring speed in (iii) to from about 100 to about 600 revolutions per minutes, and subsequently adding further anionic or nonionic surfactant in the range of from about 0.1 to about 10 percent by weight of water to control, prevent, or minimize further growth or enlargement of the particles in the coalescence step (v); (v) heating and coalescing from about 5° C. to about 50° C. above about the resin glass transition temperature, Tg, which resin Tg is from
Hopper Michael A.
Moore Emily L.
Patel Raj D.
Sacripante Guerino G.
Martin Roland
Palazzo E. O.
Xerox Corporation
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