U.S. patent number 3,849,127 [Application Number 05/244,254] was granted by the patent office on 1974-11-19 for electrostatographic process in which coated carrier particles are used.
This patent grant is currently assigned to Xerox Corporation. Invention is credited to Robert J. Hagenbach, Robert W. Madrid.
United States Patent |
3,849,127 |
Madrid , et al. |
November 19, 1974 |
ELECTROSTATOGRAPHIC PROCESS IN WHICH COATED CARRIER PARTICLES ARE
USED
Abstract
Development is obtained in an electrostatographic imaging system
with a developer mixture wherein the carrier particles are coated
with a thin layer of a solid polyphenylene oxide resin or a blend
of a polyphenylene oxide resin and a thermoplastic or thermosetting
resin.
Inventors: |
Madrid; Robert W. (Macedon,
NY), Hagenbach; Robert J. (Rochester, NY) |
Assignee: |
Xerox Corporation (Rochester,
NY)
|
Family
ID: |
27362938 |
Appl.
No.: |
05/244,254 |
Filed: |
April 12, 1972 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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27114 |
Apr 9, 1970 |
|
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585739 |
Oct 11, 1966 |
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Current U.S.
Class: |
430/123.58;
430/111.2; 430/111.35; 427/487; 427/566; 428/404; 430/111.1 |
Current CPC
Class: |
G03G
9/1135 (20130101); G03G 9/1136 (20130101); G03G
9/1133 (20130101); Y10T 428/2993 (20150115) |
Current International
Class: |
G03G
9/113 (20060101); G03g 009/02 () |
Field of
Search: |
;96/1 ;252/62.1
;117/17.5LE |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Klein; David
Assistant Examiner: Brammer; J. P.
Parent Case Text
This is a division of application Ser. No. 27,114, filed Apr. 9,
1970 which is a continuation-in-part of application Ser. No.
585,739, filed Oct. 11, 1966.
Claims
What is claimed is:
1. An electrostatographic imaging process comprising the steps of
forming an electrostatic latent image on a recording surface and
contacting said electrostatic latent image with a developer mixture
comprising finely-divided toner particles electrostatically
clinging to the surface of carrier particles, said carrier
particles comprising particulate cores coated with an outer layer
comprising from about 1 to about 20 microns in thickness of a blend
of a polyphenylene oxide resin and a solid terpolymer of (1) from
about 5 to about 94.5 percent, by weight, of an unsaturated silicon
free organic compound, (2) from about 94.5 to about 5 percent, by
weight, of an unsaturated silicon free organic compound different
from the compound of (1), and (3) from about 0.5 to about 50
percent, by weight, of a polymerizable organosilicon compound
selected from the group consisting of silanes, silanols, and
siloxanes having from 1 to 3 hydrolyzable groups and an organic
group attached directly to a silicon atom containing less than 8
carbon atoms and an unsaturated carbon to carbon linkage, the
weight ratio of said polyphenylene oxide to said terpolymer being
from about 90:10 to about 25:75, whereby at least a portion of said
finely-divided toner particles are attracted to and held on said
recording surface in conformance to said electrostatic latent
image.
2. An electrostatographic imaging process comprising the steps of
forming an electrostatic latent image on a recording surface and
contacting said electrostatic latent image with a developer mixture
comprising finely-divided toner particles electrostatically
clinging to the surface of carrier particles, said carrier
particles comprising particulate cores coated with an outer layer
comprising from about 1 to about 20 microns in thickness of a blend
of a polyphenylene oxide resin and a solid terpolymer of (1) from
about 5 to about 94.5 percent, by weight, of a styrene composition,
(2) from about 94.5 to about 5, percent, by weight, of a
composition selected from the group consisting of acrylate and
methacrylate esters, and (3) from about 0.5 to about 50 percent, by
weight, of a polymerizable organosilicon composition selected from
the group consisting of organosilanes, silanols, and siloxanes
having from 1 to 3 hydrolyzable groups and an organic group
attached directly to a silicon atom containing less than 8 carbon
atoms and an unsaturated carbon to carbon linkage, the weight ratio
of said polyphenylene oxide to said terpolymer being from about
90:10 to about 25:75, whereby at least a portion of said
finely-divided toner particles are attracted to and held on said
recording surface in conformance to said electrostatic latent
image.
3. An electrostatographic imaging process comprising the steps of
forming an electrostatic latent image on a recording surface and
contacting said electrostatic latent image with a developer mixture
comprising finely-divided toner particles electrostatically
clinging to the surface of carrier particles having a diameter of
from about 40 to about 600 microns, said carrier particles
comprising particulate cores coated with an outer layer comprising
from about 1 to about 20 microns in thickness of a blend of a solid
polyphenylene oxide resin and a solid linear addition terpolymer of
(1) from about 5 to about 94.5 percent, by weight, of a styrene
composition, (2) from about 94.5 to about 5 percent, by weight, of
a methacrylate composition selected from the group consisting of
methyl, ethyl, propyl, and butyl methacrylate and (3) from about
0.5 to about 50 percent, by weight, of a polymerizable
organosilicon composition selected from the group consisting of
silanes, silanols and siloxanes having from 1 to 3 hydrolyzable
groups and an organic group attached directly to a silicon atom
containing less than 8 carbon atoms and an unsaturated carbon to
carbon linkage, the weight ratio of said polyphenylene oxide to
said terpolymer being from about 90:10 to about 25:75, whereby at
least a portion of said finely-divided toner particles are
attracted to and held on said recording surface in conformance to
said electrostatic latent image.
Description
This invention relates in general to imaging systems and, more
particularly to improved developing materials, their manufacture
and use.
The formation and development of images on the surface of
photoconductive materials by electrostatic means is well known. The
basic xerographic process, as taught by C. F. Carlson in U.S. Pat.
No. 2,297,691, involves placing a uniform electrostatic charge on a
photoconductive insulating layer, exposing the layer to a light and
shadow image to dissipate the charge on the areas of the layer
exposed to the light and developing the resulting latent
electrostatic image by depositing on the image a finely divided
electroscopic material referred to in the art as "toner." The toner
will normally be attracted to those areas of the layer which retain
a charge, thereby forming a toner image corresponding to the latent
electrostatic image. This powder image may then be transferred to a
support such as paper. The transferred image may subsequently be
permanently affixed to the support surface as by heat. Instead of
latent image formation by uniformly charging the photoconductive
layer and then exposing the layer to a light and shadow image, one
may form the latent image by directly charging the layer in image
configuration. The powder image may be fixed to the photoconductive
layer if elimination of the powder image transfer step is desired.
Other suitable means such as solvent or overcoating treatment may
be substituted for the foregoing heat fixing step.
Several methods are known for applying the electroscopic particles
to the latent electrostatic image to be developed. One development
method, as disclosed by L. E. Walkup is U.S. Pat. No. 2,618,551 and
E. N. Wise in U.S. Pat. No. 2,618,552, is known as "cascade"
development. In this method, a developer material comprising
relatively large carrier particles having fine toner particles
electrostatically coated thereon is conveyed to and rolled or
cascaded across the electrostatic image-bearing surface. The
composition of the carrier particles is so chosen as to
triboelectrically charge the toner particles to the desired
polarity. As the mixture cascades or rolls across the image-bearing
surface, the toner particles are electrostatically deposited and
secured to the charged portion of a latent image and are not
deposited on the uncharged or background portion of the image. Most
of the toner particles accidentally deposited in the background
areas are removed by the rolling carrier, due apparently, to the
greater electrostatic attraction between the toner and carrier than
between the toner and the discharge background. The carrier and
excess toner are then recycled. This technique is extremely good
for the development of line copy images.
Another technique for developing electrostatic images is the
"magnetic brush" process as disclosed, for example, in U.S. Pat.
No. 2,874,063. In this method, a developer material containing
toner and magnetic carrier particles is carried by magnets. The
magnetic field of the magnet causes alignment of the magnetic
carrier in a brush-like configuration. This "magnetic brush" is
engaged with an electrostatic image-bearing surface and the toner
particles are drawn from the brush to the electrostatic image by
electrostatic attraction.
In most commercial processes, the cascade technique is carried out
in automatic machines. In these machines, small buckets on an
endless belt conveyor scoop the developer material from a sump and
convey it to a point above an electrostatic image-bearing surface
where the developer mixture is allowed to fall and cascade or roll
by gravity across the image-bearing surface. The carrier beads
along with any unused toner particles are then returned to the sump
for recycling through the developing system. Small quantities of
toner are periodically added to the developer mixture to compensate
for the toner depleted during the development process. This process
is repeated for each copy produced in the machine and is ordinarily
repeated many thousands of times during the usable life of the
developer. It is apparent that in this process, as well as in other
development techniques the developer mixture is subjected to a
great deal of mechanical attrition which tends to degrade both the
toner and carrier particles. This degradation, of course, occurs
primarily as a result of shear and impact forces due to the
tumbling of the developer mixture on the xerographic plate and the
movement of the bucket conveyor through the developer material in
the sump. Deterioration or degradation of carrier particles is
characterized by the separation of portions of or the entire
carrier coating from the carrier core. The separation may be in the
form of chips, flakes or entire layers and is primarily caused by
fragile, poorly adhering coating materials which fail upon impact
and abrasive contact with machine parts and other carrier
particles. Carriers having coatings which tend to chip and
otherwise separate from the carrier core must be frequently
replaced thereby increasing expense and consuming time. Print
deletion and poor print quality occur when carrier particles having
damaged coatings are not replaced. Fines and grit formed from
carrier coating disintegration tend to drift and form unwanted
deposits on critical machine parts. Many materials having high
compressive and tensile strength either do not adhere well to the
carrier core or do not possess the desired triboelectric
characteristics. The triboelectric and flow characteristics of many
carriers are adversely effected when relative humidity is high. For
example, the triboelectric values of some carrier coatings
fluctuate with changes in relative humidity and are not desirable
for employment in xerographic systems, particularly in automatic
machines which require carriers having stable predictable
triboelectric values. Another factor affecting the stability of
carrier triboelectric properties is the susceptibility of carrier
coatings to "toner impaction." When the carrier particles are
employed in automatic machines and recycled through many cycles,
the many collisions which occur between the carrier particles and
other surfaces in the machine cause the toner particles carried on
the surface of the carrier particles to be welded or otherwise
forced into carrier coatings. The gradual accumulation of
permanently attached toner material to the surface of the carrier
particles causes a change in the triboelectric value of the carrier
particles and directly contributes to the degradation of copy
quality by eventual destruction of the toner carrying capacity of
the carrier. Further, many carrier coating materials are difficult
to apply to carrier cores because they tend to form thin filaments
rather than smooth continuous coatings. Since developer materials
must flow freely to facilitate accurate metering and even
distribution during the development and developer recycling phases
of the electrostatographic process, the presence of filaments and
carrier having rough outer surfaces in developer materials is
unsuitable because the developer materials tend to cake, bridge,
and agglomerate. Some carrier coating materials having acceptable
triboelectric and coating properties are unacceptable for
employment on a commercial scale because they cannot be
economically mass produced. For example, quality control of the
triboelectric value of some resin blends is difficult to maintain
because a slight deviation in component percentages causes the
triboelectric value of the resulting product to change drastically.
Carrier coating materials having close tolerance triboelectric
values are particularly important in high speed automatic copying
machines. Thus, there is a continuing need for a better system for
developing latent electrostatic images.
It is, therefore, an object of this invention to provide developing
materials which overcome the above noted deficiencies.
It is another object of this invention to provide carrier coating
materials which tenaciously adhere to carrier cores.
It is a still further object of this invention to provide carrier
coatings having stable triboelectric values.
It is yet another object of this invention to provide carrier
coatings having high tensile and compressive strength.
It is a further object of this invention to provide coated carriers
having smooth outer surfaces.
It is still another object of this invention to provide toner
impaction resistant carrier coatings.
It is a further object of this invention to provide carrier coating
materials having easily adjustable triboelectric values.
It is yet another object of this invention to provide carrier
coatings which are more resistant to chipping and flaking.
It is another object of this invention to provide developers having
physical and chemical properties superior to those of known
developer materials.
The above objects and others are accomplished, generally speaking,
by providing novel electrostatographic developer materials
including carrier cores coated with a composition comprising a
polyphenylene oxide resin. The resin component employed in the
carrier coatings of this invention may comprise a polyphenylene
oxide resin per se, or a polyphenylene oxide resin blended with one
or more other resins. The polyphenylene oxide resin coating may be
employed in any suitable thickness. Typically, the coating on the
free flowing carrier particles is at least about 1 micron in
thickness. However, a coating having a thickness of at least about
2.5 microns is preferred because the carrier coating will then
possess sufficient thickness to resist abrasion and prevent any
pinholes which would adversely affect the triboelectric properties
of the coated carrier particles. The maximum coating thickness is
generally determined by the amount of coating material capable of
being coated on the core by any given coating technique which
produces free flowing coated particles and which does not result in
agglomeration. A practical maximum coating thickness for large size
cores is therefore about 20 microns. Within these limits, a coating
thickness of from about 3 to about 5 microns provides superior
abrasion resistance and stable triboelectric properties. While not
absolutely necessary, excellent abrasion resistance and stable
triboelectric properties are generally achieved with a
substantially smooth, continuous uniform coating of a polyphenylene
oxide resin. However, superior abrasion resistance has been
achieved with coatings which are neither uniform or continuous.
Any suitable linear polyphenylene oxide resin may be employed.
These polyphenylene oxide resins have the general formula:
##SPC1##
wherein: R' and R" are each selected from the group consisting of H
and alkyl radicals having a total of up to 12 carbon atoms in R'
and R" and n is a positive integer of at least about 25. Generally,
the high molecular weight film-forming polyphenylene oxide resins
employed in the carrier coatings of this invention are obtained by
well known polymerization techniques such as the oxidative coupling
of phenols. Oxidative coupling involves the reaction of oxygen with
active hydrogens from different molecules to produce water and a
dimer linked by an oxygen. In order to form polymers by the
oxidative coupling technique, a polyphenylene oxide monomer must
have at least two active hydrogens. Optimum impaction resistance is
obtained with a polyphenylene oxide resin formed by the copper
catalyzed oxidation of 2,6-dimethylphenol. The resulting polymer
has methyl groups at R' and R" in the general formula set forth
above. While a 2,6-xylenol monomer is preferred, any other suitable
phenol may be used to produce useful resin carrier coatings.
Typical phenols include: phenol; 2-methylphenol; 2-propyl phenol;
2-isobutyl phenol; 2,6-diethyl phenol; 2,6-diisopropyl phenol;
2-ethyl-6-methyl phenol; 2,5-dimethyl phenol; 3,5-dimethyl phenol;
and the like.
Any suitable resin may be blended with a polyphenylene oxide resin
to form the carrier coating materials of this invention. These
resins may include natural resins, modified natural resins or
synthetic resins prepared by addition, condensation or any other
technique proving suitable. The polyphenylene oxide resin may be
blended with other resins in any suitable amount. Generally to
maintain the properties of the polyphenylene oxide resin as a
coating it is present in the blend in at least the major
proportion. Typical natural and modified natural resins include:
gum copal, gum sandarac, rosin, fossil resins, zein, ethyl
cellulose, cellulose acetate, cellulose nitrate, gum nitrate,
oxidized rosin, pentaerythritol esters of rosin and the like.
Typical synthetic resins include polymers, copolymers, terpolymers
and other polymeric structures and modified polymeric structures
including, for example, polyolefins such as polyethylene,
polypropylene, chlorinated polyethylene, and chlorosulfonated
polyethylene; polyvinyl and polyvinylidine compounds such as
polystyrene, polymethylstyrene, polymethyl methacrylate,
polyacrylic acid, polyacrylonitrile, polyvinyl acetate, polyvinyl
alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl
carbazole, polyvinyl ethers and polyvinyl ketones; fluorocarbons
such as polytetrafluoroethylene, polyvinylfluoride,
polyvinylidenefluoride and polychlorotrifluoroethylene; polyamides
such as polycaproloctamo and polyhexamethylene adipamide;
polyesters such as polyethylene terephthalate; polyurethanes;
polysulfides; polycarbonates; epoxies such as the condensation
reaction product of epichlorohydrin with any one of a bisphenol A,
resorcinol, hydroquinone and ethylene glycol; phenolic resins such
as phenol formaldehyde, phenol furfural and resorcinol
formaldehyde; amino aldehydes such as urea formaldehyde and
melamine formaldehyde; and mixtures thereof.
Excellent results are obtained with a carrier coating containing a
polyphenylene oxide resin blended with the products of an addition
polymerization reaction between monomers or prepolymers of: (1)
organo silanes, silanols or siloxanes having from 1 to 3
hydrolyzable groups and an organic group attached directly to the
silicon atom containing less than 8 carbon atoms and an unsaturated
carbon to carbon linkage capable of addition polymerization and (2)
one or more silicon free types of unsaturated polymerizable organic
compounds. These addition reaction products have a weight average
molecular weight of at least about 5,000. Outstanding results are
obtained with a carrier coating containing a solid polymeric
reaction product of monomers or prepolymers of: (1) styrene and
homologues thereof, (2) acrylate or methacrylate esters and (3)
organo silanes, silanols or siloxanes having from 1 to 3
hydrolyzable groups and an organic group attached directly to a
silicon atom containing less than 8 carbon atoms and an unsaturated
carbon to carbon linkage capable of addition polymerization. These
organosilicon terpolymers are preferred additives because the
resulting blend possesses especially good triboelectric stability
and synergistic resistance to toner impaction.
Typically a solid copolymer addition reaction product may be
obtained from about 99.5 to about 50 percent, by weight, of an
unsaturated silicon free organic compound and from about 0.5 to
about 50 percent, by weight, of the above described polymerizable
organosilicon composition. Typically the solid terpolymer comprises
from about 5 to about 94.5 percent, by weight, of an unsaturated
silicon free organic compound, from about 94.5 to about 5 percent,
by weight, of an unsaturated silicon free organic compound
different from the first mentioned silicon free compound and from
about 0.5 to about 50 percent, by weight, of one of the above
described polymerizable organosilicon compounds.
The unsaturated organic group attached to the silicon atom contains
the unsaturation in a non-benzoid group and is preferably an
unsaturated hydrocarbon group. Typical unsaturated organic groups
include: vinyl, chlorvinyl, divinyl, distyryl, allyl, diallyl,
triallyl, allyl phenyl, dimethyl allyl and methacryloxypropyl
groups. Typical hydrolyzable groups include: ethoxy, methoxy,
chloro, bromo, propoxy, acetoxy and amino groups. Examples of
typical unsaturated organo silanes having hydrolyzable groups
attached to a silicon atom include: vinyl triethosy silane, vinyl
trimethoxy silane, vinyl-tris, (beta-methoxyethoxy), silane,
gamma-methacryloxypropyltrimethoxy silane, vinyl trichlorosilane,
vinyl triacetoxy silane, divinyl dichloro silane, and dimethyl
vinyl chloro silane. Suitable corresponding polymerizable
hydrolysis products and the corresponding siloxanes may be
substituted for the foregoing unsaturated organo silanes.
Unsaturated organic groups having less than 6 carbon atoms attached
to the silicon atom are preferred because of the unusually greater
polymerization activities of these groups. If more than one organic
group is attached to the silicon atom, only one of the organic
groups need be unsaturated to enter into a polymerization reaction
with other unsaturated monomers. Hence, compounds such as dimethyl
vinyl chloro silanes are suitable. When more than one unsaturated
organic group attached to the silicon atom are present, these
unsaturated groups need not be identical. For example, vinyl allyl
silicon chlorides and bromides may be employed. Partially condensed
siloxanes in the liquid state having reactive unsaturated organic
groups attached to a silicon atom may be employed as a terpolymer
reactant.
Suitable silicon free monomers or prepolymers with which the above
organosilicon compounds are particularly adapted to react to form
the polymeric organosilicon resin additives of this invention
include the unsaturated compounds which normally form resinous
polymers by addition type polymerization. Monomers or prepolymers
containing the unsaturation in a non-benzoid group may be employed,
such unsaturated monomers or prepolymers include those having
ethylenic or acetylenic linkage. Thus, there are included olefins,
diolefins, acetylenes and their derivatives, particularly
derivatives having substituents such as halogen, alkyl, aryl,
unsaturated alicyclic and other types of substituent groups
including, for example, nitrile or nitro groups. The unsaturated
organic monomers containing the unsaturation in a non-benzoid group
also include unsaturated hydrocarbons, aliphatic carbocyclic, and
heterocyclic compounds including unsaturated alcohols, aldehydes,
ketones, quinones, acids, acid anhydrides, esters, nitriles or
nitro compounds. Typical unsaturated monomers include: ethylene,
propylene, butenes, isobutylene, pentenes, hexenes, methyl
methacrylate, methyl acrylate, vinyl chloride, vinylidene chloride,
acrylonitrile, chlorovinyl acetate, styrene, butadene, chloroprene,
cyclopentadene, divinyl benzene, cyclohexadiene, ethyl
methacrylate, vinyl acetate, vinyl toluene, acetylene,
phenylacetylene, ethylvinyl benzene, allyl chloride, allyl benzene,
maleic anhydride, ethyl acrylate, diethylmaleate, butyl acrylate,
butyl methacrylate, isobutyl methacrylate, methacrylic anhydride,
vinyl formate, and mixtures thereof.
Polymerization of the unsaturated organosilicon and unsaturated
silicon free unsaturated compounds are effected with any suitable
free-radical initiator or catalyst capable of polymerizing the
monomers or prepolymers. By a "free-radical initiator or catalyst"
is meant a compound which is capable of producing free-radicals
under the polymerization conditions employed, such as compounds
having an --O--O-- or an --N=N-- linkage. Examples of the more
commonly employed free-radical initiators or catalysts include:
alkyl peroxides, such as tert-butyl hydroperoxide, and
di-tert-butyl peroxide; acyl and aroyl peroxides, such as dibenzoyl
peroxide, perbenzoic acid, dilauroy peroxide, perlauric acid and
acetyl benzoyl peroxide; azo compounds such as
azo-bisisobutyronitrile, dimethaylazodiisobutyrate,
azo-bis-1-phenylethane and alkali metal azodisulfonates; and the
like.
Generally, the impaction resistance of most resin blends increases
with an increase in the quantity of polyphenylene oxide resin
present in the blend. The polyphenylene oxide resin is therefore
generally at least present in the major amount in resin blends.
However, an exception to this general rule has been found with
combinations of polyphenylene oxide resins with the organosilicon
terpolymers described above. As illustrated in the Examples below,
optimum synergistic results are obtained when the polyphenylene
oxide resin-organosilicon terpolymer resin ratio is from about
90:10 to about 25:75. The extremely high resistance to toner
impaction is completely unexpected because the polyphenylene oxide
resin organosilicon terpolymer resin blend possesses higher toner
impaction resistance than either the polyphenylene oxide resin or
the organosilicon terpolymer resin alone. No satisfactory
explanation for this surprising result has been found.
When the carrier coatings of this invention contain thermosetting
resins blended with a polyphenylene oxide resin, the blending
should be effected while the thermosetting resin is in a monomeric
or partially polymerized stage. Polymerization of the thermosetting
monomer or partially polymerized prepolymer may be completed in
situ after the blend is applied to a carrier core. In situ
polymerization may be effectuated by any well known technique as by
application of heat. If a thermosetting resin prepolymer is
employed, the prepolymer should be in a liquid or thermoplastic
stage so that uniform blending of the prepolymer as a melt or in a
solvent solution will be facilitated.
To achieve further variation in the properties of the final
resinous product, well known additives such as plasticizers,
reactive resins, dyes, pigments, wetting agents, and mixtures
thereof may be mixed with the resin coating of this invention. When
an organosilicon polymer is blended with the polyphenylene oxide
resin, hydrolysis of the hydrolyzable groups attached to the
silicon atoms may be promoted by pre-treating the carrier core with
any suitable hydrolyzing medium such as a dilute solution of acetic
acid or by mixing the hydrolyzing material with the organosilicon
polymer prior to the coating operation.
Any suitable well known coated or uncoated carrier material may be
employed as the core of the carriers of this invention. Typical
carrier materials include sodium chloride, ammonium chloride,
aluminum potassium chloride, Rochelle salt, sodium nitrate,
potassium chlorate, granular zircon, granular silicon, methyl
methacrylate, glass, silicon dioxide, flintshot, iron, steel,
ferrite, nickel, carborundum and mixtures thereof. Many of the
foregoing and other typical carriers are described by L. E. Walkup
in U.S. Pat. No. 2,618,551; L. E. Walkup et al in U.S. Pat. No.
2,638,416 and E. N. Wise in U.S. Pat. No. 2,618,552. An ultimate
coated carrier particle diameter between about 40 microns to about
600 microns is preferred because the carrier particles then possess
sufficient density and inertia to avoid adherence to the
electrostatic latent images during the cascade development process.
Adherence of the carrier beads to an electrostatographic drum is
undesirable because of the formation of deep scratches on the drum
surface during the image transfer and drum cleaning steps,
particularly when cleaning is accomplished by a web cleaner such as
the web disclosed by W. P. Graff Jr., et al. in U.S. Pat. No.
3,186,838.
The surprisingly better results obtained from the employment of
polymeric carrier coating materials containing polyphenylene oxide
resins and blends thereof may be due to many factors. For example,
it is postulated that the unusually low water absorption properties
of the polyphenylene oxide resins contribute to the stable
triboelectric properties thereof. Further, although it is not
entirely clear, the high resistance of the carrier coatings to
toner impaction may be at least partly due to the high tensile
strength and heat resistance exhibited by polyphenylene oxide
resins, particularly blends of polyphenylene oxide resins with
organosilicon terpolymers. The polyphenylene oxide coatings of this
invention adhere well to the carrier cores tested and are also
highly resistant to chipping, and flaking.
The polyphenylene oxide resin coating compositions may be applied
to a carrier core by any conventional method such as spraying,
dipping, fluidized bed coating, brushing, and the like. The
polyphenylene oxide resins or blends thereof may be applied as a
powder, dispersion, solution, emulsion, or hot melt. When applied
as a solution, any suitable solvent may be employed. Solvents
having relatively low boiling points are preferred because less
energy and time is required to remove the solvent subsequent to
application of the coating to the carrier core. Typical solvents
include the halogenated aliphatics such as chloroform and
1,2-dichloro ethane; aromatic hydrocarbons such as toluene and
o-chlorobenzene; and the like. Any suitable coating thickness may
be employed. However, the carrier coating should be sufficiently
thick to resist flaking and chipping. The quantity of resin to be
applied to the carrier cores depends upon the density and the
surface area presented by the carrier cores. Typical coating
weights include from about 20 to about 1,000 grams of coating
material per 100 pounds of flintshot carrier cores haivng an
average diameter of about 600 microns.
Any suitable pigmented dyed electroscopic toner material may be
employed with the coated carrier of this invention. Typical toner
materials include: cumarone-indene resin, asphaltum,
phenolformaldehyde resins, rosin-modified phenolformaldehyde
resins, methacrylic resins, polystyrene resins, polypropylene
resins, epoxy resins, polyethylene resins and the like. Typical
toner materials are disclosed by H. E. Copley in U.S. Pat. No.
2,659,670; R. B. Landrigan in U.S. Pat. No. 2,753,308; M. A.
Insalaco in U.S. Pat. No. 3,079,342 and C. F. Carlson in U.S. Pat.
Reissue No. 25,136.
The following examples further define, describe and compare methods
of preparing the carrier materials of the present invention and of
utilizing them to develop electrostatic latent images. Parts and
percentages are by weight unless otherwise indicated.
EXAMPLE I
A control sample containing 1 part colored toner particles having
an average particle size of about 10 to about 12 microns and about
99 parts coated carrier particles available in the Xerox 813
Developer sold by the Xerox Corporation, Rochester, N.Y. is
cascaded across an electrostatic imagebearing surface. The
resulting developed image is transferred by electrostatic means to
a sheet of paper whereon it is fused by heat. The residual powder
is removed from the electrostatic imaging surface by a cleaning web
of the type disclosed by W. P. Graff, Jr., et al. in U.S. Pat. No.
3,186,838. After the copying process is repeated 8,000 times, the
developer mix is examined for the presence of carrier coating chips
and flakes. Numerous carrier chips and flakes are found in the
developer mix.
EXAMPLE II
A coating solution containing about 20 grams, by weight, of
polyphenylene oxide resin, PPO Grade C-1001 resin sold by the
General Electric Company, Pittsfield, Mass., dissolved in about 100
parts chloroform and 175 parts dichloro benzene is sprayed onto
glass beads having an average diameter of about 600 microns. About
20 grams of polyphenylene oxide resin is applied to about 5 pounds
of glass carrier cores. After drying, the developing procedure of
Example I is repeated with the foregoing coated carriers
substituted for the Xerox 813 carrier particles. An examination of
the developer mix after test termination reveals substantially no
carrier coating chips or flakes.
EXAMPLE III
A coating solution about 20 grams, by weight, of a resin blend
comprising about 85 percent polyphenylene oxide resin and about 15
percent of an organosilicon terpolymer resin consisting essentially
of the addition polymerization reaction product between about 15
parts sytrene, about 85 parts methyl methacrylate and about 5 parts
of vinyl triethoxy silane dissolved in toluene is sprayed onto
glass beads having an average diameter of about 600 microns. About
10 grams of resin blend is applied to about 5 pounds of glass
carrier cores. Afer drying, the developing procedure of Example I
is repeated with the foregoing coated carrier substituted for the
Xerox 813 carrier particles, an examination of the developer mix
after test termination reveals substantially no carrier coating
chips or flakes.
EXAMPLE IV
A control sample containing one part pigmented resin toner
particles having an average particle size of about 10 to about 12
microns and about 99 parts coated carrier particles available in
the Xerox 813 Developer sold by the Xerox Corporation, Rochester,
N.Y., is tumbled in a rotating cylindrical jar having a diameter of
about 21/2 inches and a surface speed of about 140 feet per minute.
Most of the carrier coating separated in the form of flakes from
the carrier core after about 100 hours after the test is initiated.
The carrier coating remaining on the carrier core is almost
completely impacted with toner.
EXAMPLE V
Glass carrier cores having an average diameter of about 600 microns
are spray coated with a coating solution comprising about 10
percent, by weight, of polyphenylene oxide resin derived from the
oxidative coupling of 2,6-dimethylphenol. About 20 grams of the
polyphenylene oxide resin is applied to about 5 pounds of glass
cores. After drying, the milling procedure of Example IV is
repeated with the foregoing coated carrier particles substituted
for the Xerox 813 carrier particles. No chips or flakes are found.
A slight amount of toner impaction is first observed after a
milling time of about 144 hours.
EXAMPLE VI
The milling procedure described in Example V is continued until the
cumulative milling time is about 240 hours. Upon termination of the
milling, no chips or flakes are found. Examination of the carrier
surfaces reveals complete impaction.
EXAMPLE VII
Glass carrier cores having an average diameter of about 600 microns
are spray coated with a coating solution comprising about 10
percent, by weight, of a resin blend comprising about 85 percent
polyphenylene oxide resin, PPO PR5311 resin sold by the General
Electric Co., and about 15 precent of an organosilicon terpolymer
resin consisting essentially of the addition polymerization
reaction product between about 15 parts styrene, about 85 parts
methyl methacrylate and about 5 parts vinyl triethoxy silane. About
20 grams of the resin blend is applied to about 5 pounds of glass
cores. After drying, the milling procedure of Example IV is
repeated with the foregoing coated carrier particles substituted
for the Xerox 813 carrier particles. A slight amount of toner
impaction is first observed after a milling time of about 144
hours. No chips or flakes are found.
EXAMPLE VIII
The milling procedure described in Example VII is continued until
the cumulative milling time is about 240 hours. Upon termination of
the milling, no chips or flakes are found. Examination of the
carrier surfaces reveals almost complete toner impaction.
EXAMPLE IX
Glass carrier cores having an average diameter of about 600 microns
are spray coated with a coating solution comprising about 10
percent, by weight, of a resin blend comprising about 75 percent
polyphenylene oxide resin and about 25 percent of an organosilicon
terpolymer resin consisting essentially of the addition
polymerization reaction product between about 50 parts styrene,
about 85 parts methyl methacrylate and about 5 parts vinyl
triethoxy silane. About 20 grams of the resin blend is applied to
about 5 pounds of glass cores. After drying, the milling procedure
of Example IV is repeated with the foregoing coated carrier
particles substituted for the Xerox 813 carrier particles. A slight
amount of toner impaction is first observed after a milling time of
about 192 hours. No chips or flakes are found.
Example X
The milling procedure described in Example IX is continued until
the cumulative milling time is about 240 hours. Upon termination of
the milling, no chips or flakes are found. Examination of the
carrier surfaces reveals only slight toner impaction.
EXAMPLE XI
Glass carrier cores having an average diameter of about 600 microns
are spray coated with a coating solution comprising 10 percent, by
weight, of a resin blend comprising about 50 percent polyphenylene
oxide resin and about 50 percent of an organosilicon terpolymer
resin consisting essentially of the addition polymerization
reaction product between about 15 parts styrene, about 85 parts
methyl metacrylate and about 5 parts vinyl triethoxy silane. About
20 grams of the resin blend is applied to about 5 pounds of glass
cores. After drying, the milling procedure of Example IV is
repeated with the foregoing coated carrier particles substituted
for the Xerox 813 carrier particles. A slight amount of toner
impaction is first observed after a milling time of about 96 hours.
No chips or flakes are found.
EXAMPLE XII
The milling procedure described in Example XI is continued until
the cumulative milling time is about 192 hours. Upon termination of
the milling, no chips or flakes are found. Examination of the
carrier surfaces reveals almost complete toner impaction.
EXAMPLE XIII
Glass carrier cores having an average diameter of about 600 microns
are spray coated with a coating solution comprising about 10
percent, by weight, of an organosilicon terpolymer resin consisting
essentially of the addition polymerization reaction product between
about 15 parts styrene, about 85 parts methyl methacrylate and
about 5 parts vinyl triethoxy silane. About 20 grams of the resin
is applied to about 5 pounds of glass cores. After drying, the
milling procedure of Example IV is repeated with the foregoing
coated carrier particles substituted for the Xerox 813 carrier
particles. A slight amount of toner impaction is first observed
after a milling time of about 96 hours. No chips or flakes are
found.
EXAMPLE XIV
The milling procedure described in Example XIII is continued until
the cumulative milling time is about 192 hours. Upon termination of
the milling, no chips or flakes are found. Examination of the
carrier surfaces reveals complete toner impaction.
EXAMPLE XV
Steel carrier cores having an average diameter of about 250 microns
are spray coated with a coating solution comprising about 15
percent, by weight, of a resin blend comprising about 90 percent
polyphenylene oxide resin NORYL resin sold by the General Electric
Company, and about 10 percent of an organosilicon terpolymer resin
consisting essentially of the addition polymerization reaction
product between about 50 parts styrene, about 50 parts isobutyl
methacrylate and about 5 parts gammamethacryloxypropyltrimethoxy
silane. About 20 grams of the resin blend is applied to about 15
pounds of steel cores. After drying, the milling procedure of
Example IV is repeated with the foregoing coated carrier particles
substituted for the Xerox 813 carrier particles. A slight amount of
toner impaction is first observed after a milling time of about 144
hours. No chips or flakes are found.
EXAMPLE XVI
Flintshot carrier cores having an average diameter of about 600
microns are spray coated with a coating solution comprising about
20 percent, by weight, of a resin blend comprising about 90 percent
polyphenylene oxide resin and about 10 percent of polycarbonate
resin. About 35 grams of the resin blend is applied to about 5
pounds of flintshot cores. After drying, the milling procedure of
Example IV is repeated with the foregoing carrier particles
substituted for the Xerox 813 carrier particles. A slight amount of
toner impaction is first observed after a milling time of about 240
hours. No chips or flakes are found.
EXAMPLE XVII
Iron carrier cores having an average diameter of about 500 microns
are spray coated with a coating solution comprising about 10
percent, by weight, of a resin blend comprising about 75 percent
polyphenylene oxide resin and about 25 percent of
ethylene-vinylacetate copolymer resin. About 20 grams of the resin
blend is applied to about 10 pounds of iron cores. After drying,
the milling procedure of Example IV is repeated with the foregoing
coated carrier particles substituted for the Xerox 813 carrier
particles. A slight amount of toner impaction is first observed
after a milling time of about 144 hours. No chips or flakes are
found.
Although specific materials and conditions were set forth in the
above exemplary processes in making and using the developer
materials of this invention, these are merely intended as
illustrations of the present invention. Various other toners,
carrier cores, substituents and processes such as those listed
above may be substituted for those in the examples with similar
results.
Other modifications of the present invention will occur to those
skilled in the art upon a reading of the present disclosure. These
are intended to be included within the scope of this invention.
* * * * *