Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Process of making developer composition
Reexamination Certificate
2001-08-29
2003-01-07
Goodrow, John (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Process of making developer composition
C524S501000
Reexamination Certificate
active
06503680
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to latex processes and, more preferably, to aggregation and coalescence or fusion of a latex with colorant, such as pigment, dye, or mixtures thereof, and optional additive particles, to produce toners for use in a variety of applications inclusive of electrophotographic imaging and printing processes such as xerographic applications, digital imaging, color imaging and the like.
PRIOR ART
In general, toners are produced by aggregating a colorant with a latex polymer formed by batch or semi-continuous emulsion polymerization. For example, U.S. Pat. No. 5,853,943, the disclosure of which is totally incorporated herein by reference in its entirety, is directed to a semi-continuous emulsion polymerization process for preparing a latex by first forming a seed polymer. U.S. Pat. No. 5,928,830, the disclosure of which is totally incorporated herein by reference in its entirety, is directed to a semi-continuous emulsion polymerization process for preparing a latex preparation of a latex polymer with a core encapsulated within a shell polymer with good fix and gloss characteristics. This latex can be used for the preparation of E/A (emulsion/aggregation/coalescence) toner resins.
Processes for making E/A (emuision/aggregation/coalescence) toner resins are well known. For example, E/A (emulsion/aggregation/coalescence) 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. Nos. 5,290,654, 5,278,020, 5,308,734, 5,370,963, 5,344,738, 5,403,693, 5,418,108, 5,364,729, and 5,346,797. Other patents of interest are 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 (spherical toners).
Using the aforementioned processes, appropriate latex polymers can be formed and used to make a variety of toners for different types of imaging and printing processes, for instance, a toner with higher molecular properties for a low-volume photocopier and a toner with lower molecular properties for a high-volume photocopier. In order to obtain specific toners having particular molecular properties, the latex composition used would have to be varied and/or the M
n
(number average molecular weight) would have to be varied depending on the particular molecular properties required. As a result of varying the latex composition and/or M
n
(number average molecular weight), the Tg (glass transition temperature) of the resulting polymer would vary. Subsequently, varying Tg's (glass transition temperature) would affect toner performance by changing its properties such as toner blocking, toner crease and toner document offset.
SUMMARY OF THE INVENTION
In a feature of the present invention, there is provided a process that utilizes a standard (universal) latex composition with many of the advantages illustrated herein.
In another feature of the present invention, there is provided a process that utilizes a standard (universal) latex composition consistent with E/A (emulsion/aggregation/coalescence) toner manufacture that provides latex polymers with a wide range of molecular properties.
In still a further feature of the present invention there is provided a process that customizes a wide range M
w
(weight average molecular weight) latex, preferably M
w
(weight average molecular weight) latexes of 25,000 to 100,000, without substantially varying the M
n
(number average molecular weight) and, as a result, without substantially varying the Tg (glass transition temperature) such that good toner performance is maintained.
In yet another feature of the present invention, there is provided a process that produces latexes by emulsion polymerization, and especially latexes prepared by a semi-continuous emulsion polymerization, wherein wide range M
w
(weight average molecular weight) latexes, preferably M
w
(weight average molecular weight) latexes of 25,000 to 100,000, can be produced without significantly varying M
n
(number average molecular weight) and, as a result, without substantially varying the Tg (glass transition temperature).
In another feature of the present invention, there is provided chain-transfer agent partitioning in a semi-continuous emulsion polymerization process to customize latex polymers for E/A (emulsion/aggregation/coalescence) toner particles processing to accommodate various toner requirements. In the present invention, ‘chain-transfer agent partitioning’ is understood to mean that, during the process of the present invention, a monomer emulsion, comprising a certain amount of chain-transfer agent, is used in portions, wherein more chain-transfer agent is added to at least one portion of the monomer emulsion during the process.
In still another feature of the present invention, there is provided a process that utilizes chain-transfer agent partitioning to enable higher M
w
(weight average molecular weight) latexes without substantially varying M
n
(number average molecular weight).
In another feature of the present invention, there is provided a chain-transfer agent partitioning, semi-continuous emulsion polymerization process and a method for preparing toner particles wherein, for example, the latex selected is formed by emulsion polymerization which is non-ionic surfactant-free. These toners are especially useful for imaging processes, especially xerographic processes which usually prefer high toner transfer efficiency, such as those processes with a compact machine design or those that are designed to provide high quality colored images with excellent image resolution and signal-to-noise ratio, and image uniformity.
In a further feature of the present invention, there is provided a process that produces latexes, especially latexes having a core/shell morphology, by a semi-continuous, consecutive emulsion polymerization in sequence with different monomers. The resulting latexes have wide range M
w
's (weight average molecular weight), preferably M
w
(weight average molecular weight) latexes of 25,000 to 100,000, without significantly varying M
n
(number average molecular weight) and, as a result, without substantially varying the Tg (glass transition temperature), so that appropriate M
n
's (number average molecular weight), M
w
's (weight average molecular weight), and Tg's (glass transition temperature) are attained whereby the core polymer is for gloss and the shell polymer is for fix.
In yet another feature of the present invention, there is provided a core/shell morphology having a high M
w
(weight average molecular weight) core and a low M
w
(weight average molecular weight) shell, or vice-versa, and maintaining a substantially similar M
n
(number average molecular weight).
In yet another feature of the present invention, there is provided economical processes for the preparation of latexes, and black and colored toner compositions with excellent colorant, especially pigment dispersions, thus enabling the achievement of improved color print quality, and wherein the toners possess improved fusing characteristics.
In still a further feature of the present invention, there is provided a process for the preparation of toner by aggregation and coalescence, or fusion (aggregation/coalescence) of latex, pigment, and additive particles.
In embodiments, there is provided a process for the preparation of a latex polymer that comprises mixing a seed particle latex, generated by aqueous emulsion polymerization of a first portion of a monomer emulsion, with a second portion of the monomer emulsion and at least one chain-transfer agent, whereby mixing is done in the presence of a free-radical initiator and heated, and wherein the monomer emulsion comprises a mixture of polymerization reagents of at least one monomer, at least one chain-transfer agent, at least one surfactant, and water. More specifically, the at least one chain transfer agent of the monomer emulsion is, for example, of from about 10 to about 80 pe
Burns Patricia A.
Chen Allan K.
Helbrecht Arthur
Liebermann George
Moore Emily L.
Goodrow John
Palallo E. O.
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