Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Process of making developer composition
Reexamination Certificate
2002-06-05
2003-06-24
Rodee, Christopher (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Process of making developer composition
C523S335000
Reexamination Certificate
active
06582873
ABSTRACT:
In U.S. Pat. No. 6,132,924, the disclosure of which is totally incorporated herein by reference, there is illustrated a process for the preparation of toner comprising mixing a colorant, a latex, and two coagulants, followed by aggregation and coalescence and wherein one of the coagulants may be polyaluminum chloride.
In U.S. Pat. No. 6,268,102, the disclosure of which is totally incorporated herein by reference, there is illustrated a process for the preparation of toner comprising mixing a colorant, a latex, and two coagulants, followed by aggregation and coalescence, and wherein one of the coagulants is a polyaluminum suifosilicate.
Illustrated in U.S. Pat. No. 5,994,020, the disclosure of which is totally incorporated herein by reference, are toner preparation processes, and more specifically, a process for the preparation of toner comprising:
(i) preparing, or providing a colorant dispersion;
(ii) preparing, or providing a functionalized wax dispersion comprised of a functionalized wax contained in a dispersant mixture comprised of a nonionic surfactant, an ionic surfactant, or mixtures thereof;
(iii) shearing the resulting mixture of the functionalized wax dispersion (ii) and the colorant dispersion (i) with a latex or emulsion blend comprised of resin contained in a mixture of an anionic surfactant and a nonionic surfactant;
(iv) heating the resulting sheared blend of (iii) below about the glass transition temperature (Tg) of the resin particles;
(v) optionally adding additional anionic surfactant to the resulting aggregated suspension of (iv) to prevent, or minimize additional particle growth of the resulting electrostatically bound toner size aggregates during coalescence (iv);
(vi) heating the resulting mixture of (v) above about the Tg of the resin; and optionally,
(vii) separating the toner particles; and a process for the preparation of toner comprising blending a latex emulsion containing resin, colorant, and a polymeric additive: adding an acid to achieve a pH of about 2 to about 4 for the resulting mixture; heating at a temperature about equal to, or about below the glass transition temperature (Tg) of the latex resin; optionally adding an ionic surfactant stabilizer; heating at a temperature about equal to, or about above about the Tg of the latex resin; and optionally cooling, isolating, washing, and drying the toner.
The appropriate components and processes of the above recited copending applications and patents may be selected for the processes of the present invention in embodiments thereof.
BACKGROUND OF THE INVENTION
The present invention is generally directed to toner processes, and more specifically, to chemical processes which involve the aggregation and fusion of latex, colorant like pigment, or dye, and additive particles into toner particles, and wherein aggregation can be primarily controlled by utilizing a coagulant of polyaluminum chloride (PAC), and wherein there can be selected a latex comprised of, for example, submicron resin particles of, for example, about 0.1 to about 0.4 micron in volume average diameter, suspended in an aqueous phase of water, nonionic and anionic surfactants and optionally suspended in an anionic surfactant to which is added a colorant dispersion comprising, for example, submicron colorant particles of, for example, about 0.08 to about 0.3 micron in volume average diameter, anionic surfactant, or optionally a nonionic surfactant, or mixtures thereof, and optionally adding a wax dispersion comprised of submicron wax particles, for example about 0.1 to about 0.3 micron in volume average diameter, suspended in an aqueous phase of water and an anionic surfactant, and wherein the resultant blend is optionally stirred and heated to a temperature below the resin Tg, resulting in aggregates to which optionally is added a second latex, to which there is added an organic water soluble or water insoluble chelating agent wherein soluble refers, for example, to 100 percent soluble or dissolvable, and insoluble refers, for example, to less than about 50 percent soluble, and more specifically, zero percent solubility in, for example, water, adjusting the pH of the mixture with a base, and heating the mixture to a temperature above the resin Tg, followed by lowering the pH of the mixture with an acid to fuse the aggregates.
More specifically, the present invention is generally directed to the aggregation of latex, colorant like pigment, dye, or mixtures thereof, and optionally a wax in the presence of polyaluminum chloride (PAC) and optionally aluminum salts as a second coagulant, and wherein the coalescence or fusion of the aggregates is accomplished by first adding an organic chelating reagent followed by a reduction of the pH with an aqueous solution of, for example, nitric acid wherein the chelating agent prevents the formation of aluminum ions (Al
3
+) which could act as a coagulant thereby initiating further growth in particle size when the pH of the mixture is reduced to below about 3.5, and wherein there are generated toner compositions with, for example, a volume average diameter of from about 1 micron to about 25 microns, and more specifically, from about 2 microns to about 12 microns, and a narrow particle size distribution of, for example, from about 1.10 to about 1.33, and more specifically, a size distribution of about 1.11 to about 1.25, the size and size distribution being measured by a Coulter Counter without the need to resort to conventional pulverization and classification methods. Furthermore, the present invention in embodiments enables minimum washing, for example about 2 to about 4 washings to provide a suitable toner triboelectrical charge such as greater than about 20 &mgr;C/g at 20 percent RH. The toners generated can be selected for known electrophotographic imaging and printing processes, including digital color processes.
In embodiments of the present invention, an organic chelating component is orimarily utilized to freeze or stabilize the aggregates particle size during coalescence in the presence of a base, for example sodium hydroxide. In polyaluminum chloride (PAC) processed wherein only a base is utilized as a freezing or stabilizing agent, upon reducing the pH of the mixture below about 3.5 there results the formation of aluminum ions (Al
3
+) which then will result in flocculation or further aggregation of the particles causing uncontrolled and undesirable processes. The present invention is directed toward overcoming this disadvantage by using organic chelation reagents which react with Al
3
+ to form a stable complex which can withstand a low pH, for example a pH of about 2 to about 3.5 when the organic chelating reagent is, for example, 8-hydroxquinoline, salicylic acid, aluminum, 3,4-dihydrobenzoic acid, and the like, and yet more specifically, resulting in very stable complexes with metal salts, especially Al
3+
which are stable against acids and bases. Furthermore, when the toners generated are roll milled and aged over a period of, for example, about 2 to about 3 hours there results stable and negative toner charging with, for example, no or minimal wrong sign positively charged toner.
The toners generated with the processes of the present invention are especially useful for imaging processes, especially xerographic processes, which usually prefer a toner transfer efficiency. Also, the toners obtained with the processes illustrated herein can be selected for digital imaging systems, processes, and color processes wherein images with high resolution and excellent image uniformity results.
PRIOR ART
In xerographic systems, especially color systems, small sized toners of from about 2 to about 8 microns can be important to the achievement of high image quality for process color applications. It may also be important to have a low image pile height to eliminate, or minimize image feel and avoid paper curling after fusing. Paper curling can be particularly pronounced in xerographic color processes primarily because of the presence of relatively high toner coverage as a resul
Hopper Michael A.
Hu Nan-Xing
Jiang Lu
Mychajlowskij Walter
Patel Raj D.
Rodee Christopher
Thompson Robert
Xerox Corporation
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