Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Process of making developer composition
Reexamination Certificate
2001-08-06
2002-12-31
Goodrow, John (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
06500597
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 sulfosilicate.
Illustrated in U.S. Pat. No. 5,994,020, the disclosure of which is totally incorporated herein by reference, are toner 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.
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 a resin containing 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 sulfosilicate (PASS), which silicate is commercially available, and is believed to be disclosed in U.S. Pat. Nos. 4,981,675; 5,069,893; 5,149,400; 5,296,213, the disclosures of which are totally incorporated herein by reference; and subsequently adding a cationic ionic surfactant as a second co-coagulant, such as SANIZOL B™, that is a benzylalkonium chloride, and wherein there is preferably selected a latex comprised of, for example, submicron resin particles in the size range of, for example, about 0.1 to about 0.5 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 in the size range of, for example, about 0.08 to about 0.5 micron in volume average diameter, anionic surfactant, or optionally a nonionic surfactant, or mixtures thereof, and optionally adding thereto a wax dispersion comprising, for example, submicron wax particles in the size range of about 0.1 to about 0.5 micron in volume average diameter suspended in an aqueous phase of water and an anionic surfactant, and wherein the resultant blend is preferably stirred and heated to a temperature below the resin Tg, resulting in aggregates to which is optionally added thereto a second latex, followed by 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, for example, a metal salt to fuse the aggregates.
More specifically, the present invention is generally directed to the aggregation of latex, colorant and optionally a wax in the presence of polyaluminum sulfosilicate and optionally a coagulant, such as SANIZOL B™, that is benzylalkonium chloride, and wherein the coalescence or fusion of the aggregates is accomplished by a reduction of the pH with an aqueous solution of, for example, aluminum sulfate, and wherein there are generated toner compositions with, for example, 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, from about 1.10 to about 1.33, and preferably a size distribution in the range of 1.11 to 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 the embodiments of the present invention when a co-coagulant, such as SANIZOL B™, is used in conjunction with the polyaluminum sulfosilicate (PASS), the process time may be further reduced by about 30 to about 50 percent as compared, for example, to similar toner processes wherein there is selected polyaluminum sulfosilicate alone. Furthermore, the advantage of using a second coagulant, such as SANIZOL B™, in combination with PASS over polyaluminum chloride (PAC) alone resides in better retention of colorant wherein the colorant is, for example, about 95 to 100 percent retained in the toner particles. Additionally, with the invention processes in embodiments, toner washing can be reduced by about 60 to about 75 percent and the triboelectric charging values of the toner obtained are substantially constant irrespective of the colorant selected. 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 in excess of greater than about 90 percent, such as those with a compact machine design without a cleaner or those that are designed to provide high quality colored images with excellent image resolution, acceptable signal-to-noise ratio, and image uniformity. Also, the toners obtained with the processes illustrated herein can be selected for digital imaging systems and processes.
With respect to the prior art, only a small part thereof has been selected and this part may or may not be fully representative of the prior art teachings or disclosures.
PRIOR ART
In xerographic systems, especially color systems, small sized toners of from about 2 to about 8 microns can be of value with regard to the achievement of high image quality for process color applications. Also, of value is the achievement of 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 result of the application of three to four colored toners. During fusing, moisture escapes from the paper due to high fusing temperatures of from about 120° C. to about 200° C., and wherein with only one layer of toner selected, such as in one-color black or highlight color xerographic applications, the amount of moisture driven off during fusing can be reabsorbed by the paper and the resulting print remains relatively flat with minimal paper curl. In process color where toner coverage is high, the relatively thick toner plastic covering
Hopper Michael A.
Patel Raj D.
Rettinger Lori A.
Goodrow John
Palazzo E. O.
Xerox Corporation
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