Plastic and nonmetallic article shaping or treating: processes – With severing – removing material from preform mechanically,... – To form particulate product
Reexamination Certificate
1999-03-22
2002-03-12
Eashoo, Mark (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
With severing, removing material from preform mechanically,...
To form particulate product
C430S106200, C430S106300, C430S108200, C430S109400
Reexamination Certificate
active
06355194
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention is generally directed to carrier and developer compositions thereof, and more specifically, the present invention relates to developer compositions with synthetic carrier components, and yet more specifically, the present invention relates to melt mixing processes for the high solids content microsynthetic carrier wherein the solids content is in the range amount of from about 60 to about 90 percent by weight of carrier, and wherein the term “micro” of “microsynthetic” refers, for example, to a synthetic carrier particle size in the range of from about 20 to about 100 microns, and more specifically, from about 25 to about 80 microns in diameter, and preferably from about 30 to about 60 microns in diameter.
In embodiments of the present invention, the synthetic carrier particles are generally comprised of binder polymer, magnetic component, colorant, and optionally charge control additives. The carriers, which can be prepared by extrusion melt mixing, pelletizing, grinding and classification, can be selected for a number of different xerographic systems, such as copiers and printers like high speed color xerographic copies, digital copiers, multi copier/printers, and more specifically, wherein colored copies with excellent and substantially no background deposits are achievable. Developer compositions comprised of the carrier particles illustrated herein are generally useful in electrostatographic or electrophotographic imaging systems, especially xerographic imaging and printing processes, and digital processes. Additionally, the invention developer compositions can be selected for a number of imaging processes such as noninteractive development systems, reference U.S. Pat. Nos. 4,292,387; 5,409,791 and 5,826,151, the disclosures of which are totally incorporated herein by reference.
PRIOR ART
The electrostatographic process, and particularly the xerographic process, is well known. This process involves the formation of an electrostatic latent image on a photoreceptor, followed by development, and subsequent transfer of the image to a suitable substrate. Numerous different types of xerographic imaging processes are known wherein, for example, insulative developer particles or conductive toner compositions are selected depending on the development systems used. Moreover, of importance with respect to the aforementioned developer compositions are the appropriate triboelectric charging values associated therewith.
Certain synthetic carriers are known, for example U.S. Pat. No. 4,426,433, which discloses a carrier with a binder and a powder of a magnetizable material dispersed therein, and carbon black. The resin binder includes styrene butadiene polymers, and the magnetite can be MAPICO BLACK™. Also, U.S. Pat. No. 5,663,027 discloses a carrier of a binder resin, such as a polyester, or a styrene/acrylic copolymer, and a magnetite such as FeO.Fe
2
O
3
. In U.S. Pat. No. 4,565,765, there is illustrated a carrier composition comprised of a resin binder of for example, polyamides, epoxies, polyurethanes, polyesters, styrene acrylates, and magnetites like MAPICO BLACKS™ Carbon black can also be included in the carrier according to the disclosure of U.S. Pat. No. 4,565,765. Moreover, in U.S. Pat. No. 5,629,119 there is disclosed melt kneading processes for the preparation of a two component binder type magnetic carrier comprised of a magnetic powder and a binder resin wherein the carrier selected contains dispersed therein a release agent.
Nonsynthetic carriers are disclosed, for example, in U.S. Pat. No. 3,590,000. These carrier particles can contain various cores, including steel, with a coating thereover of fluoropolymers, and terpolymers of styrene, methacrylate, and silane compounds. A number of these coatings can deteriorate rapidly, especially when selected for a continuous xerographic process where part of, or the entire coating may separate from the carrier core in the form of chips or flakes, and fail upon impact, or abrasive contact with machine parts and other carrier particles. These flakes or chips, which cannot generally be reclaimed from the developer mixture, usually adversely effect the triboelectric charging characteristics of the carrier particles thereby providing images with lower resolution in comparison to those compositions wherein the carrier coatings are retained on the surface of the core substrate. Further, another problem encountered with some prior art carrier coatings resides in fluctuating triboelectric charging characteristics, particularly with changes in relative humidity, and relatively low tribo as compared to the high tribo carriers of the present invention.
There are illustrated in U.S. Pat. No. 4,233,387, the disclosure of which is totally incorporated herein by reference, coated carrier components for electrostatographic developer mixtures comprised of finely divided toner particles clinging to the surface of the carrier particles. Specifically, there is disclosed in this patent coated carrier particles obtained by mixing carrier core particles of an average diameter of from between about 30 microns to about 1,000 microns with from about 0.05 percent to about 3.0 percent by weight, based on the weight of the coated carrier particles, of thermoplastic or thermosetting resin particles. The resulting mixture is then dry blended until the resin particles adhere to the carrier core by mechanical impaction, and/or electrostatic attraction. Thereafter, the mixture is heated to a temperature of from about 320° F. to about 650° F. for a period of 20 minutes to about 120 minutes, enabling the resin particles to melt and fuse on the carrier core.
There is illustrated in U.S. Pat. Nos. 4,937,166 and 4,935,326, the disclosures of which are totally incorporated herein by reference, carrier containing a mixture of polymers, such as two polymers, not in close proximity in the triboelectric series. Moreover, in U.S. Pat. No. 4,810,611, the disclosure of which is totally incorporated herein by reference, there is disclosed the addition to carrier coatings of colorless conductive metal halides in an amount of from about 25 to about 75 weight percent, such halides including copper iodide, copper fluoride, and mixtures thereof.
There are disclosed in U.S. Pat. No. 4,565,765 processes for the preparation of synthetic carriers containing a MAPICO BLACK™ magnetite up to 60 percent by weight of carrier, and VULCAN XC72R™ carbon black up to 8 percent by weight of carrier. The compositions can be ground in a Fitzmill and screened to an average particle size of about 75 microns. The MAPICO BLACK™ magnetite disclosed in U.S. Pat. No. 4,565,765 has a coercivity less than 200 gauss, and therefore is considered soft magnetic. To prepare a hard magnetic carrier, there is selected a hard magnetic powder such as, for example, strontium ferrite which is more insulative than MAPICO BLACK™ magnetite. The induced magnetic moment of a synthetic carrier in an applied magnetic field is a function of the concentration of magnetic material in the carrier particle. It is, therefore, preferred to maximize the amount of magnetic material contained in the carrier particle. To minimize the effect of magnetic moment reduction by dilution of magnetic material in the carrier particle by the binder resin and carbon black, it is desirable to have a concentration of magnetic material greater than 50 percent by weight, that is, in the range from about 50 to about 85 percent by weight, and preferably in the range from about 60 to about 75 percent by weight of carrier.
Other U.S. patents that may be of interest include U.S. Pat. No. 3,939,086, which illustrates steel carrier beads with polyethylene coatings, see column U.S. Pat. No. 6; 4,264,697, which discloses dry coating and fusing processes; U.S. Pat. Nos. 3,533,835; 3,658,500; 3,798,167; 3,918,968; 3,922,382; 4,238,558; 4,310,611; 4,397,935; and 4,434,220, the disclosures of each of these patents being totally incorporated herein by reference.
For specified interactive or noninteractive development syst
Agur Enno E.
Allison Gerald R.
Creatura John A.
Kao Sheau V.
Mahabadi Hadi K.
Eashoo Mark
Palazzo E. O.
Xerox Corporation
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