Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2001-02-09
2002-06-11
Rodee, Christopher (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S109300, C430S137150, C430S108400
Reexamination Certificate
active
06403273
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to toner particulates and toner compositions comprising particulates. More particularly, the invention relates to toner particulates comprising a styrene/acrylic copolymer having a first aliphatic hydrocarbon wax incorporated in the copolymer during polymerization, and a second aliphatic hydrocarbon wax mixed with the copolymer.
BACKGROUND OF THE INVENTION
Numerous methods and apparatus for electrophotography, electrostatic recording and electrostatic printing are known in the art. Typically, a charged photosensitive surface, for example, a charged photosensitive drum, is irradiated with an optical image and an electrostatic latent image is formed on the photosensitive surface. In the development process, a developing agent, i.e. toner, is added to the electrostatic latent image.
Typically, toner is fed to a developer roller by a metering blade positioned against the surface of the developing roller. The developing roller, with the toner on its surface, is typically rotated in a direction opposite to that of the photosensitive drum, and the toner adheres to the electrostatic latent image to develop the image.
Various toner compositions have been developed in order to provide improved copying, recording and/or printing with such apparatus. The toner may be applied as a dry powder or may be applied from a liquid. When applied from a liquid, the liquid portion does not transfer to the substrate in large amounts and solid toner particles carried by the liquid form a dry or damp powder image. To bind the toner image to the substrate, one or more steps are taken, known collectively as fixing the image. Although various ways of fixing are known, such as the application of solvent, fixing by heat is a predominant technique employed in current technology. Fixing by heat avoids the addition of new materials to the system, which are a separate expense and which must be kept out of the atmosphere or otherwise kept from being an environmental hazard to users.
However, heat fixing does not necessarily bind the powder firmly into the substrate and does not necessarily preserve the fixed image over time. It has been found that styrene/acrylic resin-based toners do not exhibit equivalent fuse grade, which is resistance to rubbing and scratching, of a polyester-based toner at low fusing temperatures. However, the polyester-based toner is more expensive than a styrene/acrylic resin-based toners.
Unfortunately, many less expensive toner compositions have unacceptable fuse grade, thereby decreasing the print quality of the printer. Accordingly, a need exists to develop toners with improved fuse grade at lower costs than polyester-based toners while maintaining good print quality.
SUMMARY OF THE INVENTION
Accordingly, it is the object of this invention to provide improved toner particulates and toner compositions.
One aspect of the present invention is a toner particulate. The toner particulate comprises a styrene/acrylic copolymer having a first aliphatic hydrocarbon wax incorporated therein during polymerization of the copolymer, and a second aliphatic hydrocarbon wax mixed with the copolymer.
Another aspect of the present invention is a toner particulate made by the process of incorporating a first aliphatic hydrocarbon wax during polymerization of a styrene/acrylic copolymer and mixing a second aliphatic hydrocarbon wax with the copolymer after polymerization of the copolymer.
The toner particulates may be manufactured at relatively low cost and exhibit good fuse grade. Still other objects, advantages and novel features of the present invention will become apparent to those skilled in the art from the following detailed description, which is simply by way of illustration, various modes contemplated for carrying out the invention. As will be realized, the invention is capable of other different obvious aspects, all without departing from the invention. Accordingly, the description is illustrative in nature and not restrictive.
DETAILED DESCRIPTION
The present invention relates to toner particulates and toner compositions comprising a styrene/acrylic copolymer having a first aliphatic hydrocarbon wax incorporated therein during polymerization of the copolymer, and a second aliphatic hydrocarbon wax mixed during the extrusion process with the copolymer.
The toner particulate comprises a styrene/acrylic polymer. As used herein, “styrene/acrylic polymer” refers to polymers formed from styrene monomer and acrylic monomer. Suitable acrylic monomers include, but are not limited to, acrylic acid, and acrylates thereof, for example, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, and phenyl acrylate, methacrylic acid, and methacrylates thereof, for example, methyl methacrylate, ethyl methacrylate, butyl methacrylate, and octyl methacrylate, acrylonitrile, methacrylonitrile, and acrylamide. Suitable styrene monomers include styrene, and substituted styrenes, including, but not limited to, alphamethyl styrene, parachlorosytrene, vinyl toluene and divinyl benzene.
Polymers typically exhibit a softening temperature and a flow temperature. As used herein, “softening temperature” is intended to refer to the temperature at which particle collapse begins, and “flow temperature” is intended to refer to the temperature at which the polymer achieves sufficient liquidity to be extruded in a capillary rheometer. The softening temperature and flow temperature can be determined using rheometers such as the SHIMADZU™ capillary rheometer.
The polymers for use in the toner particulates may include a cross-linking agent in an amount of from about 0.01 to about 5 parts by weight per 100 parts by weight of the monomers employed therein. Conventional cross-linking agents may be used. In one embodiment, the toner comprises a resin which is free of cross-linking agents.
Toner particulates may comprise more than one polymer. Generally, the polymers will have a glass transition temperature of no less than 55° C. In one embodiment, the particulate comprises a first polymer and a second polymer, each having a glass transition temperature of no less than about 55° C., preferably no less than about 60° C. Generally, the polymers will have molecular weights greater than about 2000.
In one embodiment, the toner particulate may comprise a first low molecular weight polymer and a second high molecular weight polymer.
The toner particulate further comprises a first aliphatic hydrocarbon wax, which is incorporated during the polymerization of the styrene/acrylic polymer. A second aliphatic hydrocarbon wax is mixed with the polymerized styrene/acrylic polymer containing the first aliphatic hydrocarbon wax after polymerization of the copolymer.
In one embodiment of the present invention, the first in-situ aliphatic hydrocarbon wax comprises a paraffin wax. In one exemplary embodiment, the paraffin wax has a melting point of from about 40° C. to about 130° C. More preferably, the paraffin wax has a melting point of from about 70° C. to about 120° C., and most preferably from about 80° C. to about 110° C. In another exemplary embodiment, the paraffin wax is of the formula C
n
H
2n+2
, wherein n ranges from about 12 to about 22, more preferably n is about 17.
In another embodiment of the present invention, the second external aliphatic hydrocarbon wax comprises a polyolefin wax. In one exemplary embodiment, the polyolefin wax has a melting point of from about 110° C. to about 140° C., more preferably from about 115° C. to about 125° C. In another exemplary embodiment, the polyolefin wax comprises polyethylene, polypropylene, a copolymer of an olefin and a styrene-malic anhydride half ester, or mixtures thereof.
In yet another embodiment of the present invention, the second aliphatic hydrocarbon wax comprises paraffin wax. In one exemplary embodiment, the paraffin wax is of the formula C
n
H
2n+2
, wherein n ranges from about 12 to about 22, more preferably n is about 17.
In another exemplary embodiment, the first aliphatic hydrocar
Moore Michael Thomas
Ting Vincent Wen-Hwa
Brady John A.
Lexmark International Inc.
Rodee Christopher
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