CA1087013A - ELECTROPHOTOGRAPHIC CARRIER OF MAGNETICALLY ATTRACTABLE CARRIER COATED WITH A METAL ION-LINKED CARBOXYLIC ACID .alpha.-OLEFIN COPOLYMER - Google Patents
ELECTROPHOTOGRAPHIC CARRIER OF MAGNETICALLY ATTRACTABLE CARRIER COATED WITH A METAL ION-LINKED CARBOXYLIC ACID .alpha.-OLEFIN COPOLYMERInfo
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- CA1087013A CA1087013A CA163,118A CA163118A CA1087013A CA 1087013 A CA1087013 A CA 1087013A CA 163118 A CA163118 A CA 163118A CA 1087013 A CA1087013 A CA 1087013A
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- Prior art keywords
- carrier
- carboxylic acid
- alpha
- particles
- toner
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G9/00—Developers
- G03G9/08—Developers with toner particles
- G03G9/10—Developers with toner particles characterised by carrier particles
- G03G9/113—Developers with toner particles characterised by carrier particles having coatings applied thereto
- G03G9/1132—Macromolecular components of coatings
- G03G9/1133—Macromolecular components of coatings obtained by reactions only involving carbon-to-carbon unsaturated bonds
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- Physics & Mathematics (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Spectroscopy & Molecular Physics (AREA)
- General Physics & Mathematics (AREA)
- Developing Agents For Electrophotography (AREA)
Abstract
ELECTROGRAPHIC CARRIER VEHICLE AND
DEVELOPER COMPOSITION - CASE C
Abstract of the Disclosure An electrographic carrier vehicle and developer composition containing said carrier vehicle are described.
The carrier vehicle is composed of magnetically attractable core particles having a metal ion-linked .alpha.-olefin-carboxylic acid copolymer and finely divided electrically conductive particles coated thereon.
DEVELOPER COMPOSITION - CASE C
Abstract of the Disclosure An electrographic carrier vehicle and developer composition containing said carrier vehicle are described.
The carrier vehicle is composed of magnetically attractable core particles having a metal ion-linked .alpha.-olefin-carboxylic acid copolymer and finely divided electrically conductive particles coated thereon.
Description
0~7013 This invention rel~tes to electrography and to a particulate carrier vehicle and a dry electrographic developer composition containing such a c~rrier vehicle useful in the development of latent electrostatic charye images.
Electrographic imaging and developing processes, e.g., electrophotographic imaging processes and techniques, have been .
extensively described in both the patent and other literature, for example, U.S. Patent Nos. 2,221,776 issued November 19, 1940;
Electrographic imaging and developing processes, e.g., electrophotographic imaging processes and techniques, have been .
extensively described in both the patent and other literature, for example, U.S. Patent Nos. 2,221,776 issued November 19, 1940;
2,277,013 issued March 17, 1942; 2,297,691 issued October 6, 1942;
10 2,357,809 issued September 12, 1944; 2,551,582 issued May 8, 1951;
2,825,814 issued March 4, 1958; 2,833,648 issued May 6, 1958;
10 2,357,809 issued September 12, 1944; 2,551,582 issued May 8, 1951;
2,825,814 issued March 4, 1958; 2,833,648 issued May 6, 1958;
3,220,324 issued November 30, 1965; 3,220,831 issued November 30, 1965; 3,220,833 issued November 30, 1965 and many others, ~enerally, these processes have in common the steps of forming a latent electrostatic charge image on an insulating electrographic ele-ment. The electrostatic latent image is then rendered visible by a development step in which the charged surface of the photocon-ductive element is brought into contact with suitable developer mix.
One method for applying the developer mix is by the well-known magnetic-brush process. Such a process generally utilizes apparatus of the type described, for example, in U.S. Patent No. .
3,003,462 issued October 10, 1961 and customarily comprises a non-magnetlc rotatably mounted cylinder having fixed magnetic means mounted inside. The cylinder is arranged to rotate so that part of the surface is immersed in or otherwise contacted with a supply of developer mix. The granular mass comprising the developer mix is magnetically attracted to the surface of the cylinder. As the developer mix comes within the influence of the field generated by the magnetic means within the cylinder, the particles thereof - . . . ., . , " ., . . ~, .. ,. ; ,. . . . . :
~ 7~3 arrange themselves in bristle-like formations resembling a brush. The bristle formations that are formed by the deve].oper mix tend to conform to the lines of magnetic flux, standing erect in the vicinity of the poles and laying 1 0 ' - ' ~',, ``'. ~
-2a-~1()8~ 3 F.ubstantiall~ flat when said mix is outside the environment o~
the magnet-~c poles. Within one revolution the continually rotating cylinder p~cks up developer mix from a supply source and returns part or all of this material to the supply. This mode of operation assures that fresh mix is always available to the surface of the photoconductive element at its point of contact with the brush. In a typical rotational cycle, the roller performs the successive steps of developer mix pickup, brush formation, brush contact with the electrographic element, e.g., a photocon-ductive element, brush collapse and finally mix release.
In magnetic-brush development of electrostatic images the developer is commonly a triboelectric mixture of fine toner powder comprised, for example, of a dyed or pigmented thermo-plastic resin with coarser carrier particles of a magnetlc material such as iron particles, e-tc.
In magnetic brush development as well as in various other different types of electrographic development wherein a dry triboelectric mixture of a particulate carrier vehicle and a fine toner powder are utilized, it is advantageous to modify the surface properties of the particulate carrier vehicle so that a high net electrical charge is imparted to the toner powder. Particulate carrier particles capable Or imparting a relatively stable~ high net electrlcal charge to the toner powder aid in improving retention of the toner to the carrier vehicle and thereby aid in reducing the amount of undesired "toner throw-off", i.e. the amount of toner powder thrown out of the developer mix as it is agitated in an electrographic devel-opment apparatus. Aside from the extraneous contamination problems inherent with airborne toner dust in the apparatus, "toner i1 throw-off" also leads to imaging problems such as unwanted ~Z
background and scumming of the electrostatlc image-bearing element.
~7~3 A variety of methods and materials ~or modi~ying the sur~ace properties of particulate electrographic carrier ~ehicles ha~e been proposed. See, for example, Miller, U.S
3,5L~7,822 issued December 15, 1970, describing certain carboxylated resins useful ~or coating a particulate carrier vehiclej Miller Belgian Patent 71~6,111 dated April 30, 1970 which describes magnetic carrier particles ha~ing two or more coatings of a resinous material applied thereon such that ~-there is no substantial dissolution of one resinous layer into -an adjacent resin layer, Miller, U.S 3,632,512 issued January ~, 1972, describing methods o~ treating and coating;
iron particles utilizing an acid wash followed by controlled drying and, i~ desired, a subsequent coating operation to produce a particulate iron carrier vehicle having improved surface characteristics. Miller, U.S. 3,736,257 issued May 29, 1973, describes a particulate carrier vehicle bearing an improved, highly conductive overcoat. Various other literature relating, in part, to varying the surface characteristics of a particulate carrier vehicle include U.S. Patents 2,618,551 issued November 18, 1952j 2,618,552 issued November 18, 1952; 2,753,308 issued July 3, 1956;
2,87L~,063 issued ~ebruar~ 17, 1959j 2,880,696 lssued April 7, 1959; 3,202,093 issued ~ugust 21~, 1965; 3,526,533 issued September 1, 1970; 3,533,835 issued October 13, 1970 British Patent 1,17L~,571 dated December 17, 1969j and Canadian Patent 835,317 issued February 2L~, 1970.
In accordance with the present invention, it has been discovered that core particles having on the outer surface thereof a resinous coating of an ionomeric carboxylic acid --3 ~-olefin copolymer provide an ef~ective particulate carrier vehicle ~or an electrographic developer.
According to one embodiment o~ the invention, the resinous ionomeric coating is provided as an outer coating ~or magnetically-attractable core particles. The resultant ionomeric-_L~_ 10~7C~3 coated magnetically-attractable carrier particles, when admixed with a ~ine toner powder to form an electrographic developer composition, are especially useful in a magnetic-brush electro~
graphic ~evelopment process.
According to another embodiment of the invention the ionomeric coating of the particulate carrier vehicle may have incorporated therein finely-divided electrically-conductive particles such as carbon black particles. The incorporation of finely-divided carbon black particles in the ionomeric coated carrier of the invention provides a particulate carrier which, when admixed with a suitable toner powder, provides improved ~ -solid area image development without e~fecting a substantial change in the net electrical charge imparted to the toner powder.
This result represents an unexpected and surprising discovery.
That is, it is generally recognized in the art that the addition of e~en relatively small quantities of finely-divided electrically conductive particles, such as carbon black, to conventional resin-coated carrier particles ordinarily substantially reduces the static triboelectric value of the carrier coating; therefore, -the net electrical charge imparted to toner powder admixed with such a carrier vehicle is also substantially reduced, (See U.S.
3,533,835 at Col, 10 and Examples II-VII thereof).
The ionomeric materials useful as polymerlc coatings for the carrier particles of the invention comprise ionic copolymers of (a) an ~-olefin having the general formula RCH = C~I~ wh~re R is a radical selected from the class of hydrogen and alkyl radicals having from 1 to about 8 carbon atoms and (b) an ~,~-ethylenically unsaturated carboxylic acid having from 3 to about 8 carbon atoms, said copolymers having from 10~ to about 90~ of the carboxylic acid groups ionized with metal îons The ionomers are typically formed by "neutralization" of a base q-olefin-carboxylic acid copolymer wi-th an ioni~able metal compound. The unsaturated carboxylic acid content of the copolymer ~5-~
is typically f'rom about 0.2 to 25 mole percent based on the q~olefin~acid base copolymer, and the q~ole~in content o~ thecopolymer lS at leas-t 50 mole percent based on the 4~olefi~~
acid base copolymer. ~specially useful in the invention are lonorneric, carboxyllc acid ~-olefin copolymers having a free acid content less than about 2 milliequivalents of lN NaOH per gram of the ionomeric copolymer based on the'dry weight of the ~
ionomer. Typically, the carboxylic acid groups contained in the ¦ ~ ' ionomeric materials useful in the invention are randomly distri~
10 buted throughout the polymeric structure. !'~
Ionomeric materials which have been found to provide especially good results according to the present invention are '~
' ionomeric carboxylic acid-ethylene copolymers having recurring structural units which are conventionally represented in the literature as follows:
r CH2 - CH2)n - CH - (CH2 ~ C~I2)n o~ ~Oe M+l to M-~3 ~C ~ 0~ /OH
. ~CH2 - C - (CH2 CH2)n - CH2 - C~I - (C'H2 - CH2)n3 wherein ~1 to M 3 is a metallic ion and n is an inte~er within the range o~ 1 to about 20 or more.
As can be seen by the a'bove structural ~ormula, the metal ions contained in the ionomeric materials are believed to provlde ionic crosslinki.ng, Metals especially useful as the me-tal lons contalned within the ionomeric materials are alkali metal ions including Na~, K~, Li+, and Cs+. ~Iowever, a variety of other metallic ions may also be used including com-plexed and uncomplexed metal ions.
When using the uncomplexed metal ions the valence of the ion corresponds to the valence of the metal. These metal ions are obtainod from the commonly known and used metal ~alts. The complexed metal ions are those in which the metal is bonded to more than one type of salt group, at least one of which is ionized and at least on~ o~ which is no-t. Since the formation o~ the ionic copolymers requires only one ionized valence state, it will be apparent that such complexed metal ions are equally well suited in the present invention. The term "metal ion having one or more ionized valence states" means a metal ion having the general formula Me+nXm, where n is the ionic charge and is at least one~ X is a nonionized group and n~m equal the valence of the metal. The utility of compleXed metal ions employed in the ~ormation of ionic copolymers corresponds in their ionized valences to those o~ the uncomplexed metal ions.
The monovalent metal~ are, of course, excluded but higher valent metals may be included depending on how many metal valences are complexed and how many can be ionized. q~e pr~ferred complexed metal ions are those in which all but one metal valences are `~
complexed and on~ is readily ionized. Such compounds are in particular the mixed salts of very weak acids, such as oleic and stearic acid, with ionizable acids, such as formic and acetic acid.
The uncomplexed metal ions which are sultable ln formlng the ionlc copolymers used in the present invention comprlse mono- d:L- and trlval~nt lons of` metals in Groups I, II, III, IV-A and VIII of the Periodic Table of Elements (see page 392, EIandbook of Chemistry and Physics, Chemical Rubber Publishing Co., 37th ed~) Suitable monovalent metal ions are Na+, K , Li+, Cs~~, Ag~, Hg~ and Cu+. Suitable divalent metal ions are +2 M +2 Ca~2 Sr-~2 Ba~2 Cu~~2, Hg , Sn , Pb , Fe ~ Cd Co , Ni and Zn . Suitable trivalent metal ions are Al S ~3 F ~~3 nd Y+3 The quantity of ions employed or the degree of neu- j tralization will differ with the degree of solid property change ~ 37~3 and the degree of melt property change desired in the resultant ionomeric material. In general, it has been reported that the concentration of the metal ion should be at least such that the metal ion neutralizes at least 10 percent of the carboxylic acid ~ ,, groups in order to obtain a significant cha ~e in properties.
The degree of neutralization for optimum properties will vary with the acid concentration and the molecular weight of the base copolymer. However, it is generally reported desirable to neu-tralize at least 50 percent of the acid groups. The degree of neutralization may be measured by several techniques. Thus, infrared analysis may be employed and the degree of neutraliza-tion calculated from the changes resulting in the absorption bands. Another method comprises the titration of a solution of ; the ionic copolymer with a strong base. In general, it has been reported that the added metal ion reacts stoichiometrically wlth the carboxylic acid in the base polymer up to 90 percent neutrallzations. Small excess quantities of the crosslinking agent are necessary to carry the neutralization to completion.
However, large excess quantities of the crosslinking agent do not add to the properties of the ionic copolymer, since once all carboxylic acid groups have been ionically crosslinked, no further crosslinks are formed As stated above, especially u~seful ionomeric materials ln the present invention are those in which the resultant ionomer has a free acid content less than about 2 milliequivalents of lN NaOH per gram of the ionomeric copolyrner based on the dry welght of the ionomer Such ionomeric coated carrier particles have been found to impart a high net electrical charge to the toner material and produce extremely small amounts of "toner throw-off" in a rnagnetic brush development apparatus.
The ~ -olef`in polymers employed in the formation of the ba~se copolymers are ~ -olefins which have the general formula RC~I - CII2 where R is either a hydrogen or an alkyl group I
-8 ` I
` ~0~7~3 ha~ing preferably from 1 to 8 carbon atoms. Thus, suitable ole~ins include ethylene, propylene, butene-l, pentene-l, hexene-l~ heptene-l, 3-methylbu-tene-1,4-methylpentene-1, etc.
~lthough ole~ins ha~ing hlgher carbon numbers can be employed, they are not materials which are readily obtained or a~ailable.
The concentration of the ~-olefin is at least 50 mol percen~
in the base copolymer, and is preferably greater than 80 mol -percent. -The second component employed in the formation of the base copolymer comprises an ~,~-ethylenically unsaturated carboxylic acid having preferably from 3 to 8 carbon a-toms.
Examples of such monomers are acrylic acid, methacrylic acid, ethacrylic acid, itaconic acid, maleic acid, ~urnaric acid, monoesters ofsaid dicarboxylic acids, such as methyl hydrogen maleate, methyl hydrogen ~umarate, ethyl hydrogen ~umarate and maleic anhydride. Although maleic anhydride is not a carboxylic acid in that it has no hydrogen attached to the carboxyl groups, it can be considered an acid for present purposes because of its - chemical reactivity being that of an acid. Similarly, other ~ monoethylenically unsaturated anhydrides of carboxylic acids can be employed. As indicated, the concentration of acidic monomer in the ~ase copolymer is ~rom 0.2 mol percent to 25 mol percent, and, pre-~erabl~, from 1 to lO mol percent.
Greater detall concerning the ionomeric (i.e., ion-linked) materials useful in the present invention may be found in Rees, U S. Patent 3,264,272 issued August 2, 1966.
In accordance with the present invention, ionomeric coating material is applied to a core particle in the form of an aqueous-alcoholic dispersion containing finely-di~ided parti-cles of the ionomer dispersed therein. Typically, a surfactantis also present to aid in -the formation and stabilization of the aqueous ionomeric dispersion. Typically, the aqueous-alcoholic ionomer dispersions have a solids content ranging from about lO
1~' 9 37~3 , ~:
to about 60% by weight. The particle size of the ionomeric mater-ial dispersed therein is reported to vary from about 0.02 to 0.6 microns, generally from 0.1 to 0.6 microns. The pH of the iono-meric dispersion is typically basic in character varying from about 7.0 to about 12. The melt viscosity of a typical dry iono-meric coating on a carrier core particle is on the order of about 5 x 103 poise as measured at 150C. at a shear rate of 300 sec.
The dispersions are typically applied to the core particles to be coated at a temperature within the range of from roughly 25C. to about 85C. When so applied, a thin highly adherent film of the ionomeric material is formed which may cover all or only certain portions of the outer surface of the core particles. Once applied, the coating may be heated up to about 140C. to develop optimum film strength and to dry the coating. No special binding agents are necessary to adhere the ionomeric resin to the magnetic core particles thus providing one of the advantages of the invention.
The ionomer dispersion may be applied to the core particle by any known coating technique, e.g., by a fluidized bed coating , process. It may be applied by passing the particulate material to be coated through a bath containing the coating composition, in a continuous manner or in a batch manner. The coating may also be sprayed on the ~ilm, or applied manually by brushing or the like.
The amount of the ionomeric material coated on the carrier core particles may vary from about 0.001 to about 3~ by weight based on the total weight of the carrier particles. For example, on sponge iron core particles it appears that dry ionomeric coatings in the range of about 0.05 to about 0.60 percent by weight based on the total weight of the coated carrier is desir-able. Especially good results have been obtained utilizing on sponge iron particles ionomeric coatings comprising 0.15 to 0.30 percent by weight of the coated carrier particle. Although more or less of the ionomeric coating may be utilized if desired, ~7013 it appears that~ for example, on sponge iron particle levels below about 0.05 percent start to exhibit an increase in "toner throw-off" while levels above about 0.60 percent ~o not appear to provide as good development o~ solid area images as ls otherw~se obtainable. I
As indica~ed above, in accordance with one embodiment ~;
of the invention, finely-divided electrically conductive particles `!' ; such as carbon black may be incorporated in the ionomeric coating.
A variety o~ different methods for incorporating such additives m~y~be usedl One use~ul meth~d simply involves a-dmixing the electrically conductive particulate additive into the ionomeric dispersion prior to its application on the particulate carrier core particles. Typically, these electrically conductive particles have a particle size within the range of from about 1 to about 20 microns. The electrically conductive particles have a speci~ic resistance less than about 10 ohm-cm., typioally, as in the cAse o~ carbon black, less than 1 ohm-cm. /Speaific resistanoe as used herein is measured at room temperature./
Generally, if electrically conductive particles are incorporated in the ionomeric coating, useful amounts Or suoh oonductive con-ductive part;cles are within the range of from about 1 to about 50 parts by weight of conductive particl0s per 100 part~ by weight of ionomer ooating (based on the dry wei~ht o~ the ionomerio ooating~
;; ~dvantageously, the core materials whioh can suitably be coated to ~orm carrier parti¢les in accordance with this invention are magnetio materials. The phrase ~magnetic materials~' as u.sed herein encompasses a variety of magnetically attractable mat6rials. Particularly useful materials would include ferro-magnetic materials such as the metals of the first transition series, i.e., nickel, iron, cobalt, and alloys and mixtures ` ' -11-.
~01~ 3 thereof. Other use~ul materials which exhibit a net magnetic moment are the ferrimagnetic materials. ~xamples o~ such ~errimagnetic materials would include the rerrites, which are ;
materials having the general ~ormula ~eO.~e203, where Me is a metal ion, as well as mixed ferrites, which contain more than `-one species of metal ion in addition to iron~ and the substituted ferrites, in which another metal replaces some of the iron.
Also included in the phrase magnetic material are particles such as those described in Miller, Canadian 835,317 issued February 24, 1970, and which are comprised of, for example, iron dispersed in a resin binder. Such magnetic materials are used as a core in accordance with this invention over which is coated the above-described ionomeric resin. The core can consist of a solid particle of magnetic material or can be a nonmagnetic particle overcoated with ferromagnetic materials as described in Belgian Patent No. 726,806, dated ~arch ll~, 1969. The core can comprise rough-surfaced magnetically responsive ;
particles, smooth-surfaced magnetically responsive particle;
or a mixture of rough-surfaced and smooth-surfaced magnetically -responsive particles. Particles having these varying surface properties and mixtures thereof are more fully described in Trachtenberg et al., U.S. 3,838,o5l~ lssued September 24, 197 ent:Ltled "~lectrographic Carrier Vehicle and ~eveloper Compositlon -- Case A core can vary in size and shape with core particles having an average diameter of from about 1200 to about 30 microns. Particularly good development is obtained with core materials of from about 300 to about 60 microns average diameter.
The size of the core particles used will, of course, depend upon several factors such as the type of images ultimately developed, desired thickness of the ionomeric resin coating, etc.
The phrase "average diameter" as used herein is not meant to împly that only perfectly uniformly dimensioned particles can A~ 12- ~
.. ... . . .. ... ... :. :
,."\
-~ - 1087013 1-be used This phrase is used to refer to the average thickness of particles when measured along several axes. Average diameter also refers to the approxirnate size of the openings in a standard ¦~
sieve series which would ~ust retain or just pass a given particle.
In addltion, it may be noted that the core materials useful in the present invention may be sub~ected to various treatments to modi~y their sur~ace properties prior to being coated with the !:
above-described terpolymer. For example, it may be desirable to wash a magnetic core in an acid-wash, rinse and subject ~0 the washed particles to controlled drying conditions so as to ind~ce or exclude oxidation of the surface of the carrier particles. Such treatments are especially use~ul when the magnetic core comprise~ iron particles. Such treatment processes are described mora fully in Belgian Patent 71~6,109 dated April ;
30, 1970-Electrostatic developer compositions of the present invention can be prepared b~ mixing ~rom about 90 to about 99 b~ weight of the above-described carrier vehicle with from about lO to about l~ by weight of a suitable electroscopic toner ~20 material.
~he toner material (or marking particles) useful in dry electrograph-Lc developer compositions ar~ generally comprised ..,., .
; `I o~ a resin binder and a colorant. Suitable toners can be s~lected ~rom a wlde variet~ o~ materlals to glve deslred ~ .
physical properties to the developed image and the proper triboelectric relationship to match th~ carrier particles used. Generally, any of the toner powders known in the art are suitable for mixing in the developer composition of this invention. In certain instances, the toner may be comprised solely of colorant material without any resinous binder.
In other cases, where a visible image is not desired or needed, .¦
-13- .
'~
. . , . , . ~
1~87013 the toner may be composed solely of a colorless material, such as a resinous material, having the desired physical and triboelectric properties.
When the toner powder selected is utilized with magnetic carrier particles in a magnetic-brush development arrangement,the toner clings to the carrier by triboelectric attraction. The carrier particles acquire a charge of one polarity and the toner acquires a charge of the opposite polarity. Thus, if the carrier is mixed with a resin toner which is higher in the triboelectric series, the toner normally acquires a positive charge and the carrier a negative charge.
Useful toner particles can be prepared by various methods.
Two convenient techniques for preparing these toners are spray-drying or melt-blending followed by grinding. Spray-drying in-volves dissolving the resin, colorant and any additives in a vola-tile organic solvent such as dichloromethane. This solution is then sprayed through an atomizing nozzle using a substantially non-reactive gas such as nitrogen as the atomixing agent. During ; atomization, the volatile solvent evaporates from the airborne droplets, producing toner particles of the uniformly colored .
resin. The ultimate particle size is determined by varying the size of the atomizing nozzle and the pressure oE the gaseous atomizing agent. Further details relating to spray-drying may be found in Carlson, U.S. Patent 2,357,809 issued Sept. 12, 1944.
Conventionally, particles of a diameter between about 1/2~ and about 30~ are used, with particles between about 2~ and 15J~ being preferred, although larger or smaller particles can be used where ;
desired for particular development or image considerations.
Suitable toners can also be prepared by melt-blending.
This technique involves melting a powdered form of polymer or resin and mixing it with suitable colorants and additives. The resin can readily be melted or heat~d on compounding rolls ` -` 10~370~3 ~
, ~.
which are also useful to mix or otherwise blend the resin and -~
addenda so as to promote the complete intermixing of these various ingredients. A~ter thorough blending, the mixture is colled and solidi~ied. The resultant solid mass is then broken into small `
pieces and finely ground to form a free-flowing powder of toner particles. Such a melt-blending technique is described in Walkup/ U.S. Patent 2,618,551 issued November 18, 1951. Of course, various other techniques for making toner particles may also be used. For example, certain spray-freeze drying techniques may be -~
modified to provide useful methods for preparing toner particles.
An example of such a modified spray freeze drying technique is described in Product Licensing Index, Volume 84, April, 1971. The resultant toner particles usually range in size from about 1/2 to about 30~.
The resin material used in preparing the toner can be selected from a wide variety of materials, including natural resins, modified natural resins and synthetic resins. Exemplary of useful natural resins are balsam resins, colophony, and shellac. Exemplary of sultable modified natural resins are colophony-modified phenol resins and other resins listed below with a large proportion of colophony. Suitable synthetic resins are all synthetic resins known to be useful for toner purposes, for example, polymers, such as certain polycarbonate resins described in U.S. 3,694,359 issued September 26, 1972, and in Product Licensing Index, Volume 84, April 1971, vinyl polymers and copolymers including polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyvinyl acetals, polyvinyl ether, polyacrylic and polymethacrylic esters, polystyrene, including substituted polystyrenes; polycondensates, e.g., polyesters, such as phthalate, terephthalic and isophthalic polyesters, maleinate resins and colophony-mixed esters of high alcohols; phenol-~ !37e~3formaldehyde resins, including modified phenol-formaldehyde con-dcnsates; aldehyde resins; ketone resins; polyamides; polyurethanes, etc. Moreover, chlorina~ed rubber and polyolefins, such as various polyethylenes, polypropyl~nes, polyisobutyl~nes, are also suitable.
Typical toner ma~erials having incorpora~ed therein styrene con-taining materials are disclosed in the following U.S. Patents:
2,917,460, Solar, issued December 15, 1959; Re. 25,136, Carlson, issued March 13, 1962; 2,788,288, Kheinfrank et al, issued April 9, 1957; 2,638,416, Walkup et al, issued April L2, 1953;
2,618,552, Wise, issued November 18, 1952; and 2,659,670, Copley, issued November 17, 1953. Other useful styrene containing toner resins are copolymers prepared from a monomeric blend of (a) 40-60% by weight styrene or styrene homolog; (b) 20-50% by weight of lower alkyl acrylate and rnethacrylate, e.g., alkyl meth-acryLates and alkyl acryl~tes having up to 3 carbon atoms in the alkyl groups; and (c) 5-30% by weight oE higher alkyl acrylates and methacrylates, e.g., alkyl methacrylates and alkyl acrylates having 6-20 or more carbon atoms in the alkyl group.
Colorants useful in the practice of this inYentiOn can be selected ~rom a variety of materials such as dyestuffs or pigments.
Such materials serve to color the to;~er and thus render it more visible. Suitable toner materials having appropriate caking and charging properties can, of course, be pr~pared without the use o~
a colorant matcrial where it is desired to ha~e a developed ima~e o~ low optical opacity. In those instances where it is desired to ~l have high optical opacity, the colorants used can, in principle, be ;, selected rom vir~ually all of the compounds mentioned in the Color Index, Vols. I and II, Second Edition. Included among the vast ~umber o use~ul colorants would be such materials as l-lansa Yello~ G
(C.I. 11680), Nigrosine Spirit soluble (C.I. 50415), Chromogen Black ET00 (C.I. 14645), Rhodamine B (C.I. 45170), Solvent Black 3 ! :-(C.I. 26150), Fuchsine N (C.I. 42510), C.I. Basic Blue g (C.I. 52015), etc. Anotller useful class o~ colorants is comprised of nigrosine salts 5uch as nigrosine salts o~ mono- and di-functional organic acids ~.~87(J~3 having from about 2 to about 20 carbon atoms such as chloroacetic acid, stearic acid, sebacic acid, lauric acid, azelaic acid, adipic acid, abietic acid and the like. Nigrosine salts of this t~pe are disclosed in Belgian Patent 734,570 dated August 14,1969.
Carbon black also provides a useful colorant as disclosed in Walkup, U.S. Patent 2,618,551 issued November 18, 1952. The ;~
amount of colorant added may vary over a wide range, ~or example, from about 3 to about 20 percent of the weight of the resin binder. Par~icularly good results are obtained when the amount ;~
is from about 5 to about 10 percent. In certain instances, it may be desirable or preferred to omit the colorant, in which case the lower limit of concentration would be zero.
In addition, if desired, organic melt viscosity modifying agents for the resin binder may be incorporated in the toner par-ticles. If such viscosity modifying agents are utilized, the ratio of melt viscosity modifying agent to resin binder generally can vary from about 1:3 to about 1.5:1. Further information con-cerning these viscosity modifying agents may be found in Merrill et al, French Patent 2,085,119 dated November 22, 1971.
The following examples are provided to further illustrate ~` the present invention and certain advantages thereof:
This example illustrates certain of the unique electrical properties of the ionomeric coated carrier particles of the pre-sent invention. The example illustrates that even when relatively large amounts of finely-divided electrically conductive parti-culate matter such as carbon black are incorporated in the iono-meric coatings of the carrier particle, these coated carrier par-ticles nevertheless impart relatively high net electrical charge ;~
to toner particles admixed with the ionomeric coated carrier particles. In this example, a control toner composed of pigmented ~ .
1~370~3 thermoplastic resin particles is used. The carrier particles are composed of sponge iron particles having an average diameter within the range of from 80 to 120 mesh. These sponge iron carrier particles are obtained from the Hoeganaes Corporation under the tradename of Hoeganaes EH iron particles. These sponge iron particles utilized in the example have an oxidized sur~ace which may be obtained, for example, by treating these particles ~.
in an acid wash and drying in an oxygen-containing atmosphere as described in Belgian Patent 746,109 dated April 30, 1970. The oxidized sponge iron particles are then coated with an aqueous dispersion of an ionomeric, acid-modified ethylene copolymer.
. The dispersion of ionomeric material is purchased from the E. I.
DuPo.nt Company under the trademark Elvax D-1070. After coati~g the oxidized sponge iron particles with the aqueous dispersion of ionic material, the coated particles are dried to form the resultant carrier particles having coated on the outer surface . thereof a tough, thin discontinuous coating of ionomeric material. ~;
, When dry, the total amount of ionomeric material contained on the . ::
surface of the carrier particles is approximately 0.15% by weight based on the total weight of the coated carrier particles. A
total of five different particulate carrier vehicles are made as described hereinabove, the only difference among the five carrier vehicles being the quantity of electrically conductive particles incorporated in the ionomeric coating. Each of the 5 carriers are then mixed with an identical amount of the control toner to form 5 separate developer mixes, each mix containing 5~ by weight of toner. In each case the electrically conductive particles are incorporated in the resultant ionomeric coated carrier particles by admixing a suitable amount of finely-divided carbon particles ~.
in the aqueous dispersion of ionomeric material prior to the `: ~.0~7~3~ 3 :
coating thereof on the oxidized sponge iron core particle. The amount of finely-divided electrically conductive carbon particles incorporated in each of the ionomeric coated carrier vehicles utilized in this example are set forth immediately hereinbelow.
' : .
-18a-~ 01!3~013 The net toner charge, Q, imparted by each of the 5 carrier vehicles to the control toner is measured (using the technique described in Example 3 hereinafter). `
Carbon Particles (parts by weight carbon particles per Carrier hundred parts by weight Net Toner Charge Vehicle of dry ionomerlc coating) (microcoulombs /gram) 1 0 - 18.6 ` ;~
2 10 17 ~ 3 ~I r 3 20 19.2
One method for applying the developer mix is by the well-known magnetic-brush process. Such a process generally utilizes apparatus of the type described, for example, in U.S. Patent No. .
3,003,462 issued October 10, 1961 and customarily comprises a non-magnetlc rotatably mounted cylinder having fixed magnetic means mounted inside. The cylinder is arranged to rotate so that part of the surface is immersed in or otherwise contacted with a supply of developer mix. The granular mass comprising the developer mix is magnetically attracted to the surface of the cylinder. As the developer mix comes within the influence of the field generated by the magnetic means within the cylinder, the particles thereof - . . . ., . , " ., . . ~, .. ,. ; ,. . . . . :
~ 7~3 arrange themselves in bristle-like formations resembling a brush. The bristle formations that are formed by the deve].oper mix tend to conform to the lines of magnetic flux, standing erect in the vicinity of the poles and laying 1 0 ' - ' ~',, ``'. ~
-2a-~1()8~ 3 F.ubstantiall~ flat when said mix is outside the environment o~
the magnet-~c poles. Within one revolution the continually rotating cylinder p~cks up developer mix from a supply source and returns part or all of this material to the supply. This mode of operation assures that fresh mix is always available to the surface of the photoconductive element at its point of contact with the brush. In a typical rotational cycle, the roller performs the successive steps of developer mix pickup, brush formation, brush contact with the electrographic element, e.g., a photocon-ductive element, brush collapse and finally mix release.
In magnetic-brush development of electrostatic images the developer is commonly a triboelectric mixture of fine toner powder comprised, for example, of a dyed or pigmented thermo-plastic resin with coarser carrier particles of a magnetlc material such as iron particles, e-tc.
In magnetic brush development as well as in various other different types of electrographic development wherein a dry triboelectric mixture of a particulate carrier vehicle and a fine toner powder are utilized, it is advantageous to modify the surface properties of the particulate carrier vehicle so that a high net electrical charge is imparted to the toner powder. Particulate carrier particles capable Or imparting a relatively stable~ high net electrlcal charge to the toner powder aid in improving retention of the toner to the carrier vehicle and thereby aid in reducing the amount of undesired "toner throw-off", i.e. the amount of toner powder thrown out of the developer mix as it is agitated in an electrographic devel-opment apparatus. Aside from the extraneous contamination problems inherent with airborne toner dust in the apparatus, "toner i1 throw-off" also leads to imaging problems such as unwanted ~Z
background and scumming of the electrostatlc image-bearing element.
~7~3 A variety of methods and materials ~or modi~ying the sur~ace properties of particulate electrographic carrier ~ehicles ha~e been proposed. See, for example, Miller, U.S
3,5L~7,822 issued December 15, 1970, describing certain carboxylated resins useful ~or coating a particulate carrier vehiclej Miller Belgian Patent 71~6,111 dated April 30, 1970 which describes magnetic carrier particles ha~ing two or more coatings of a resinous material applied thereon such that ~-there is no substantial dissolution of one resinous layer into -an adjacent resin layer, Miller, U.S 3,632,512 issued January ~, 1972, describing methods o~ treating and coating;
iron particles utilizing an acid wash followed by controlled drying and, i~ desired, a subsequent coating operation to produce a particulate iron carrier vehicle having improved surface characteristics. Miller, U.S. 3,736,257 issued May 29, 1973, describes a particulate carrier vehicle bearing an improved, highly conductive overcoat. Various other literature relating, in part, to varying the surface characteristics of a particulate carrier vehicle include U.S. Patents 2,618,551 issued November 18, 1952j 2,618,552 issued November 18, 1952; 2,753,308 issued July 3, 1956;
2,87L~,063 issued ~ebruar~ 17, 1959j 2,880,696 lssued April 7, 1959; 3,202,093 issued ~ugust 21~, 1965; 3,526,533 issued September 1, 1970; 3,533,835 issued October 13, 1970 British Patent 1,17L~,571 dated December 17, 1969j and Canadian Patent 835,317 issued February 2L~, 1970.
In accordance with the present invention, it has been discovered that core particles having on the outer surface thereof a resinous coating of an ionomeric carboxylic acid --3 ~-olefin copolymer provide an ef~ective particulate carrier vehicle ~or an electrographic developer.
According to one embodiment o~ the invention, the resinous ionomeric coating is provided as an outer coating ~or magnetically-attractable core particles. The resultant ionomeric-_L~_ 10~7C~3 coated magnetically-attractable carrier particles, when admixed with a ~ine toner powder to form an electrographic developer composition, are especially useful in a magnetic-brush electro~
graphic ~evelopment process.
According to another embodiment of the invention the ionomeric coating of the particulate carrier vehicle may have incorporated therein finely-divided electrically-conductive particles such as carbon black particles. The incorporation of finely-divided carbon black particles in the ionomeric coated carrier of the invention provides a particulate carrier which, when admixed with a suitable toner powder, provides improved ~ -solid area image development without e~fecting a substantial change in the net electrical charge imparted to the toner powder.
This result represents an unexpected and surprising discovery.
That is, it is generally recognized in the art that the addition of e~en relatively small quantities of finely-divided electrically conductive particles, such as carbon black, to conventional resin-coated carrier particles ordinarily substantially reduces the static triboelectric value of the carrier coating; therefore, -the net electrical charge imparted to toner powder admixed with such a carrier vehicle is also substantially reduced, (See U.S.
3,533,835 at Col, 10 and Examples II-VII thereof).
The ionomeric materials useful as polymerlc coatings for the carrier particles of the invention comprise ionic copolymers of (a) an ~-olefin having the general formula RCH = C~I~ wh~re R is a radical selected from the class of hydrogen and alkyl radicals having from 1 to about 8 carbon atoms and (b) an ~,~-ethylenically unsaturated carboxylic acid having from 3 to about 8 carbon atoms, said copolymers having from 10~ to about 90~ of the carboxylic acid groups ionized with metal îons The ionomers are typically formed by "neutralization" of a base q-olefin-carboxylic acid copolymer wi-th an ioni~able metal compound. The unsaturated carboxylic acid content of the copolymer ~5-~
is typically f'rom about 0.2 to 25 mole percent based on the q~olefin~acid base copolymer, and the q~ole~in content o~ thecopolymer lS at leas-t 50 mole percent based on the 4~olefi~~
acid base copolymer. ~specially useful in the invention are lonorneric, carboxyllc acid ~-olefin copolymers having a free acid content less than about 2 milliequivalents of lN NaOH per gram of the ionomeric copolymer based on the'dry weight of the ~
ionomer. Typically, the carboxylic acid groups contained in the ¦ ~ ' ionomeric materials useful in the invention are randomly distri~
10 buted throughout the polymeric structure. !'~
Ionomeric materials which have been found to provide especially good results according to the present invention are '~
' ionomeric carboxylic acid-ethylene copolymers having recurring structural units which are conventionally represented in the literature as follows:
r CH2 - CH2)n - CH - (CH2 ~ C~I2)n o~ ~Oe M+l to M-~3 ~C ~ 0~ /OH
. ~CH2 - C - (CH2 CH2)n - CH2 - C~I - (C'H2 - CH2)n3 wherein ~1 to M 3 is a metallic ion and n is an inte~er within the range o~ 1 to about 20 or more.
As can be seen by the a'bove structural ~ormula, the metal ions contained in the ionomeric materials are believed to provlde ionic crosslinki.ng, Metals especially useful as the me-tal lons contalned within the ionomeric materials are alkali metal ions including Na~, K~, Li+, and Cs+. ~Iowever, a variety of other metallic ions may also be used including com-plexed and uncomplexed metal ions.
When using the uncomplexed metal ions the valence of the ion corresponds to the valence of the metal. These metal ions are obtainod from the commonly known and used metal ~alts. The complexed metal ions are those in which the metal is bonded to more than one type of salt group, at least one of which is ionized and at least on~ o~ which is no-t. Since the formation o~ the ionic copolymers requires only one ionized valence state, it will be apparent that such complexed metal ions are equally well suited in the present invention. The term "metal ion having one or more ionized valence states" means a metal ion having the general formula Me+nXm, where n is the ionic charge and is at least one~ X is a nonionized group and n~m equal the valence of the metal. The utility of compleXed metal ions employed in the ~ormation of ionic copolymers corresponds in their ionized valences to those o~ the uncomplexed metal ions.
The monovalent metal~ are, of course, excluded but higher valent metals may be included depending on how many metal valences are complexed and how many can be ionized. q~e pr~ferred complexed metal ions are those in which all but one metal valences are `~
complexed and on~ is readily ionized. Such compounds are in particular the mixed salts of very weak acids, such as oleic and stearic acid, with ionizable acids, such as formic and acetic acid.
The uncomplexed metal ions which are sultable ln formlng the ionlc copolymers used in the present invention comprlse mono- d:L- and trlval~nt lons of` metals in Groups I, II, III, IV-A and VIII of the Periodic Table of Elements (see page 392, EIandbook of Chemistry and Physics, Chemical Rubber Publishing Co., 37th ed~) Suitable monovalent metal ions are Na+, K , Li+, Cs~~, Ag~, Hg~ and Cu+. Suitable divalent metal ions are +2 M +2 Ca~2 Sr-~2 Ba~2 Cu~~2, Hg , Sn , Pb , Fe ~ Cd Co , Ni and Zn . Suitable trivalent metal ions are Al S ~3 F ~~3 nd Y+3 The quantity of ions employed or the degree of neu- j tralization will differ with the degree of solid property change ~ 37~3 and the degree of melt property change desired in the resultant ionomeric material. In general, it has been reported that the concentration of the metal ion should be at least such that the metal ion neutralizes at least 10 percent of the carboxylic acid ~ ,, groups in order to obtain a significant cha ~e in properties.
The degree of neutralization for optimum properties will vary with the acid concentration and the molecular weight of the base copolymer. However, it is generally reported desirable to neu-tralize at least 50 percent of the acid groups. The degree of neutralization may be measured by several techniques. Thus, infrared analysis may be employed and the degree of neutraliza-tion calculated from the changes resulting in the absorption bands. Another method comprises the titration of a solution of ; the ionic copolymer with a strong base. In general, it has been reported that the added metal ion reacts stoichiometrically wlth the carboxylic acid in the base polymer up to 90 percent neutrallzations. Small excess quantities of the crosslinking agent are necessary to carry the neutralization to completion.
However, large excess quantities of the crosslinking agent do not add to the properties of the ionic copolymer, since once all carboxylic acid groups have been ionically crosslinked, no further crosslinks are formed As stated above, especially u~seful ionomeric materials ln the present invention are those in which the resultant ionomer has a free acid content less than about 2 milliequivalents of lN NaOH per gram of the ionomeric copolyrner based on the dry welght of the ionomer Such ionomeric coated carrier particles have been found to impart a high net electrical charge to the toner material and produce extremely small amounts of "toner throw-off" in a rnagnetic brush development apparatus.
The ~ -olef`in polymers employed in the formation of the ba~se copolymers are ~ -olefins which have the general formula RC~I - CII2 where R is either a hydrogen or an alkyl group I
-8 ` I
` ~0~7~3 ha~ing preferably from 1 to 8 carbon atoms. Thus, suitable ole~ins include ethylene, propylene, butene-l, pentene-l, hexene-l~ heptene-l, 3-methylbu-tene-1,4-methylpentene-1, etc.
~lthough ole~ins ha~ing hlgher carbon numbers can be employed, they are not materials which are readily obtained or a~ailable.
The concentration of the ~-olefin is at least 50 mol percen~
in the base copolymer, and is preferably greater than 80 mol -percent. -The second component employed in the formation of the base copolymer comprises an ~,~-ethylenically unsaturated carboxylic acid having preferably from 3 to 8 carbon a-toms.
Examples of such monomers are acrylic acid, methacrylic acid, ethacrylic acid, itaconic acid, maleic acid, ~urnaric acid, monoesters ofsaid dicarboxylic acids, such as methyl hydrogen maleate, methyl hydrogen ~umarate, ethyl hydrogen ~umarate and maleic anhydride. Although maleic anhydride is not a carboxylic acid in that it has no hydrogen attached to the carboxyl groups, it can be considered an acid for present purposes because of its - chemical reactivity being that of an acid. Similarly, other ~ monoethylenically unsaturated anhydrides of carboxylic acids can be employed. As indicated, the concentration of acidic monomer in the ~ase copolymer is ~rom 0.2 mol percent to 25 mol percent, and, pre-~erabl~, from 1 to lO mol percent.
Greater detall concerning the ionomeric (i.e., ion-linked) materials useful in the present invention may be found in Rees, U S. Patent 3,264,272 issued August 2, 1966.
In accordance with the present invention, ionomeric coating material is applied to a core particle in the form of an aqueous-alcoholic dispersion containing finely-di~ided parti-cles of the ionomer dispersed therein. Typically, a surfactantis also present to aid in -the formation and stabilization of the aqueous ionomeric dispersion. Typically, the aqueous-alcoholic ionomer dispersions have a solids content ranging from about lO
1~' 9 37~3 , ~:
to about 60% by weight. The particle size of the ionomeric mater-ial dispersed therein is reported to vary from about 0.02 to 0.6 microns, generally from 0.1 to 0.6 microns. The pH of the iono-meric dispersion is typically basic in character varying from about 7.0 to about 12. The melt viscosity of a typical dry iono-meric coating on a carrier core particle is on the order of about 5 x 103 poise as measured at 150C. at a shear rate of 300 sec.
The dispersions are typically applied to the core particles to be coated at a temperature within the range of from roughly 25C. to about 85C. When so applied, a thin highly adherent film of the ionomeric material is formed which may cover all or only certain portions of the outer surface of the core particles. Once applied, the coating may be heated up to about 140C. to develop optimum film strength and to dry the coating. No special binding agents are necessary to adhere the ionomeric resin to the magnetic core particles thus providing one of the advantages of the invention.
The ionomer dispersion may be applied to the core particle by any known coating technique, e.g., by a fluidized bed coating , process. It may be applied by passing the particulate material to be coated through a bath containing the coating composition, in a continuous manner or in a batch manner. The coating may also be sprayed on the ~ilm, or applied manually by brushing or the like.
The amount of the ionomeric material coated on the carrier core particles may vary from about 0.001 to about 3~ by weight based on the total weight of the carrier particles. For example, on sponge iron core particles it appears that dry ionomeric coatings in the range of about 0.05 to about 0.60 percent by weight based on the total weight of the coated carrier is desir-able. Especially good results have been obtained utilizing on sponge iron particles ionomeric coatings comprising 0.15 to 0.30 percent by weight of the coated carrier particle. Although more or less of the ionomeric coating may be utilized if desired, ~7013 it appears that~ for example, on sponge iron particle levels below about 0.05 percent start to exhibit an increase in "toner throw-off" while levels above about 0.60 percent ~o not appear to provide as good development o~ solid area images as ls otherw~se obtainable. I
As indica~ed above, in accordance with one embodiment ~;
of the invention, finely-divided electrically conductive particles `!' ; such as carbon black may be incorporated in the ionomeric coating.
A variety o~ different methods for incorporating such additives m~y~be usedl One use~ul meth~d simply involves a-dmixing the electrically conductive particulate additive into the ionomeric dispersion prior to its application on the particulate carrier core particles. Typically, these electrically conductive particles have a particle size within the range of from about 1 to about 20 microns. The electrically conductive particles have a speci~ic resistance less than about 10 ohm-cm., typioally, as in the cAse o~ carbon black, less than 1 ohm-cm. /Speaific resistanoe as used herein is measured at room temperature./
Generally, if electrically conductive particles are incorporated in the ionomeric coating, useful amounts Or suoh oonductive con-ductive part;cles are within the range of from about 1 to about 50 parts by weight of conductive particl0s per 100 part~ by weight of ionomer ooating (based on the dry wei~ht o~ the ionomerio ooating~
;; ~dvantageously, the core materials whioh can suitably be coated to ~orm carrier parti¢les in accordance with this invention are magnetio materials. The phrase ~magnetic materials~' as u.sed herein encompasses a variety of magnetically attractable mat6rials. Particularly useful materials would include ferro-magnetic materials such as the metals of the first transition series, i.e., nickel, iron, cobalt, and alloys and mixtures ` ' -11-.
~01~ 3 thereof. Other use~ul materials which exhibit a net magnetic moment are the ferrimagnetic materials. ~xamples o~ such ~errimagnetic materials would include the rerrites, which are ;
materials having the general ~ormula ~eO.~e203, where Me is a metal ion, as well as mixed ferrites, which contain more than `-one species of metal ion in addition to iron~ and the substituted ferrites, in which another metal replaces some of the iron.
Also included in the phrase magnetic material are particles such as those described in Miller, Canadian 835,317 issued February 24, 1970, and which are comprised of, for example, iron dispersed in a resin binder. Such magnetic materials are used as a core in accordance with this invention over which is coated the above-described ionomeric resin. The core can consist of a solid particle of magnetic material or can be a nonmagnetic particle overcoated with ferromagnetic materials as described in Belgian Patent No. 726,806, dated ~arch ll~, 1969. The core can comprise rough-surfaced magnetically responsive ;
particles, smooth-surfaced magnetically responsive particle;
or a mixture of rough-surfaced and smooth-surfaced magnetically -responsive particles. Particles having these varying surface properties and mixtures thereof are more fully described in Trachtenberg et al., U.S. 3,838,o5l~ lssued September 24, 197 ent:Ltled "~lectrographic Carrier Vehicle and ~eveloper Compositlon -- Case A core can vary in size and shape with core particles having an average diameter of from about 1200 to about 30 microns. Particularly good development is obtained with core materials of from about 300 to about 60 microns average diameter.
The size of the core particles used will, of course, depend upon several factors such as the type of images ultimately developed, desired thickness of the ionomeric resin coating, etc.
The phrase "average diameter" as used herein is not meant to împly that only perfectly uniformly dimensioned particles can A~ 12- ~
.. ... . . .. ... ... :. :
,."\
-~ - 1087013 1-be used This phrase is used to refer to the average thickness of particles when measured along several axes. Average diameter also refers to the approxirnate size of the openings in a standard ¦~
sieve series which would ~ust retain or just pass a given particle.
In addltion, it may be noted that the core materials useful in the present invention may be sub~ected to various treatments to modi~y their sur~ace properties prior to being coated with the !:
above-described terpolymer. For example, it may be desirable to wash a magnetic core in an acid-wash, rinse and subject ~0 the washed particles to controlled drying conditions so as to ind~ce or exclude oxidation of the surface of the carrier particles. Such treatments are especially use~ul when the magnetic core comprise~ iron particles. Such treatment processes are described mora fully in Belgian Patent 71~6,109 dated April ;
30, 1970-Electrostatic developer compositions of the present invention can be prepared b~ mixing ~rom about 90 to about 99 b~ weight of the above-described carrier vehicle with from about lO to about l~ by weight of a suitable electroscopic toner ~20 material.
~he toner material (or marking particles) useful in dry electrograph-Lc developer compositions ar~ generally comprised ..,., .
; `I o~ a resin binder and a colorant. Suitable toners can be s~lected ~rom a wlde variet~ o~ materlals to glve deslred ~ .
physical properties to the developed image and the proper triboelectric relationship to match th~ carrier particles used. Generally, any of the toner powders known in the art are suitable for mixing in the developer composition of this invention. In certain instances, the toner may be comprised solely of colorant material without any resinous binder.
In other cases, where a visible image is not desired or needed, .¦
-13- .
'~
. . , . , . ~
1~87013 the toner may be composed solely of a colorless material, such as a resinous material, having the desired physical and triboelectric properties.
When the toner powder selected is utilized with magnetic carrier particles in a magnetic-brush development arrangement,the toner clings to the carrier by triboelectric attraction. The carrier particles acquire a charge of one polarity and the toner acquires a charge of the opposite polarity. Thus, if the carrier is mixed with a resin toner which is higher in the triboelectric series, the toner normally acquires a positive charge and the carrier a negative charge.
Useful toner particles can be prepared by various methods.
Two convenient techniques for preparing these toners are spray-drying or melt-blending followed by grinding. Spray-drying in-volves dissolving the resin, colorant and any additives in a vola-tile organic solvent such as dichloromethane. This solution is then sprayed through an atomizing nozzle using a substantially non-reactive gas such as nitrogen as the atomixing agent. During ; atomization, the volatile solvent evaporates from the airborne droplets, producing toner particles of the uniformly colored .
resin. The ultimate particle size is determined by varying the size of the atomizing nozzle and the pressure oE the gaseous atomizing agent. Further details relating to spray-drying may be found in Carlson, U.S. Patent 2,357,809 issued Sept. 12, 1944.
Conventionally, particles of a diameter between about 1/2~ and about 30~ are used, with particles between about 2~ and 15J~ being preferred, although larger or smaller particles can be used where ;
desired for particular development or image considerations.
Suitable toners can also be prepared by melt-blending.
This technique involves melting a powdered form of polymer or resin and mixing it with suitable colorants and additives. The resin can readily be melted or heat~d on compounding rolls ` -` 10~370~3 ~
, ~.
which are also useful to mix or otherwise blend the resin and -~
addenda so as to promote the complete intermixing of these various ingredients. A~ter thorough blending, the mixture is colled and solidi~ied. The resultant solid mass is then broken into small `
pieces and finely ground to form a free-flowing powder of toner particles. Such a melt-blending technique is described in Walkup/ U.S. Patent 2,618,551 issued November 18, 1951. Of course, various other techniques for making toner particles may also be used. For example, certain spray-freeze drying techniques may be -~
modified to provide useful methods for preparing toner particles.
An example of such a modified spray freeze drying technique is described in Product Licensing Index, Volume 84, April, 1971. The resultant toner particles usually range in size from about 1/2 to about 30~.
The resin material used in preparing the toner can be selected from a wide variety of materials, including natural resins, modified natural resins and synthetic resins. Exemplary of useful natural resins are balsam resins, colophony, and shellac. Exemplary of sultable modified natural resins are colophony-modified phenol resins and other resins listed below with a large proportion of colophony. Suitable synthetic resins are all synthetic resins known to be useful for toner purposes, for example, polymers, such as certain polycarbonate resins described in U.S. 3,694,359 issued September 26, 1972, and in Product Licensing Index, Volume 84, April 1971, vinyl polymers and copolymers including polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyvinyl acetals, polyvinyl ether, polyacrylic and polymethacrylic esters, polystyrene, including substituted polystyrenes; polycondensates, e.g., polyesters, such as phthalate, terephthalic and isophthalic polyesters, maleinate resins and colophony-mixed esters of high alcohols; phenol-~ !37e~3formaldehyde resins, including modified phenol-formaldehyde con-dcnsates; aldehyde resins; ketone resins; polyamides; polyurethanes, etc. Moreover, chlorina~ed rubber and polyolefins, such as various polyethylenes, polypropyl~nes, polyisobutyl~nes, are also suitable.
Typical toner ma~erials having incorpora~ed therein styrene con-taining materials are disclosed in the following U.S. Patents:
2,917,460, Solar, issued December 15, 1959; Re. 25,136, Carlson, issued March 13, 1962; 2,788,288, Kheinfrank et al, issued April 9, 1957; 2,638,416, Walkup et al, issued April L2, 1953;
2,618,552, Wise, issued November 18, 1952; and 2,659,670, Copley, issued November 17, 1953. Other useful styrene containing toner resins are copolymers prepared from a monomeric blend of (a) 40-60% by weight styrene or styrene homolog; (b) 20-50% by weight of lower alkyl acrylate and rnethacrylate, e.g., alkyl meth-acryLates and alkyl acryl~tes having up to 3 carbon atoms in the alkyl groups; and (c) 5-30% by weight oE higher alkyl acrylates and methacrylates, e.g., alkyl methacrylates and alkyl acrylates having 6-20 or more carbon atoms in the alkyl group.
Colorants useful in the practice of this inYentiOn can be selected ~rom a variety of materials such as dyestuffs or pigments.
Such materials serve to color the to;~er and thus render it more visible. Suitable toner materials having appropriate caking and charging properties can, of course, be pr~pared without the use o~
a colorant matcrial where it is desired to ha~e a developed ima~e o~ low optical opacity. In those instances where it is desired to ~l have high optical opacity, the colorants used can, in principle, be ;, selected rom vir~ually all of the compounds mentioned in the Color Index, Vols. I and II, Second Edition. Included among the vast ~umber o use~ul colorants would be such materials as l-lansa Yello~ G
(C.I. 11680), Nigrosine Spirit soluble (C.I. 50415), Chromogen Black ET00 (C.I. 14645), Rhodamine B (C.I. 45170), Solvent Black 3 ! :-(C.I. 26150), Fuchsine N (C.I. 42510), C.I. Basic Blue g (C.I. 52015), etc. Anotller useful class o~ colorants is comprised of nigrosine salts 5uch as nigrosine salts o~ mono- and di-functional organic acids ~.~87(J~3 having from about 2 to about 20 carbon atoms such as chloroacetic acid, stearic acid, sebacic acid, lauric acid, azelaic acid, adipic acid, abietic acid and the like. Nigrosine salts of this t~pe are disclosed in Belgian Patent 734,570 dated August 14,1969.
Carbon black also provides a useful colorant as disclosed in Walkup, U.S. Patent 2,618,551 issued November 18, 1952. The ;~
amount of colorant added may vary over a wide range, ~or example, from about 3 to about 20 percent of the weight of the resin binder. Par~icularly good results are obtained when the amount ;~
is from about 5 to about 10 percent. In certain instances, it may be desirable or preferred to omit the colorant, in which case the lower limit of concentration would be zero.
In addition, if desired, organic melt viscosity modifying agents for the resin binder may be incorporated in the toner par-ticles. If such viscosity modifying agents are utilized, the ratio of melt viscosity modifying agent to resin binder generally can vary from about 1:3 to about 1.5:1. Further information con-cerning these viscosity modifying agents may be found in Merrill et al, French Patent 2,085,119 dated November 22, 1971.
The following examples are provided to further illustrate ~` the present invention and certain advantages thereof:
This example illustrates certain of the unique electrical properties of the ionomeric coated carrier particles of the pre-sent invention. The example illustrates that even when relatively large amounts of finely-divided electrically conductive parti-culate matter such as carbon black are incorporated in the iono-meric coatings of the carrier particle, these coated carrier par-ticles nevertheless impart relatively high net electrical charge ;~
to toner particles admixed with the ionomeric coated carrier particles. In this example, a control toner composed of pigmented ~ .
1~370~3 thermoplastic resin particles is used. The carrier particles are composed of sponge iron particles having an average diameter within the range of from 80 to 120 mesh. These sponge iron carrier particles are obtained from the Hoeganaes Corporation under the tradename of Hoeganaes EH iron particles. These sponge iron particles utilized in the example have an oxidized sur~ace which may be obtained, for example, by treating these particles ~.
in an acid wash and drying in an oxygen-containing atmosphere as described in Belgian Patent 746,109 dated April 30, 1970. The oxidized sponge iron particles are then coated with an aqueous dispersion of an ionomeric, acid-modified ethylene copolymer.
. The dispersion of ionomeric material is purchased from the E. I.
DuPo.nt Company under the trademark Elvax D-1070. After coati~g the oxidized sponge iron particles with the aqueous dispersion of ionic material, the coated particles are dried to form the resultant carrier particles having coated on the outer surface . thereof a tough, thin discontinuous coating of ionomeric material. ~;
, When dry, the total amount of ionomeric material contained on the . ::
surface of the carrier particles is approximately 0.15% by weight based on the total weight of the coated carrier particles. A
total of five different particulate carrier vehicles are made as described hereinabove, the only difference among the five carrier vehicles being the quantity of electrically conductive particles incorporated in the ionomeric coating. Each of the 5 carriers are then mixed with an identical amount of the control toner to form 5 separate developer mixes, each mix containing 5~ by weight of toner. In each case the electrically conductive particles are incorporated in the resultant ionomeric coated carrier particles by admixing a suitable amount of finely-divided carbon particles ~.
in the aqueous dispersion of ionomeric material prior to the `: ~.0~7~3~ 3 :
coating thereof on the oxidized sponge iron core particle. The amount of finely-divided electrically conductive carbon particles incorporated in each of the ionomeric coated carrier vehicles utilized in this example are set forth immediately hereinbelow.
' : .
-18a-~ 01!3~013 The net toner charge, Q, imparted by each of the 5 carrier vehicles to the control toner is measured (using the technique described in Example 3 hereinafter). `
Carbon Particles (parts by weight carbon particles per Carrier hundred parts by weight Net Toner Charge Vehicle of dry ionomerlc coating) (microcoulombs /gram) 1 0 - 18.6 ` ;~
2 10 17 ~ 3 ~I r 3 20 19.2
4 30 18.4 l~o 17 ~ 5 Observation o~ the above data collected in Table 1 hereinabove indicates that there is no significant decrease in the triboelectric charge imparted to a toner powder even when relatively large amounts o~ conductive carbon particles are incorporated in the ionomeric coated carrler particles of the 20 invention. This unique property of the ionomeric coating carrier , ,.
particles of the invention is surprising and unexpected in view of the teachings of the art which suggests that by incorporating conductive particles in a polymer coated carrier vehicle~ the electrical charge imparted to the toner powder is substantially reduced, Each of the above-described carrier vehicles, i.e.
Numbers 1-5 are then admixed with 5~ by weight of a dry pigmented `!
thermoplastic resinous toner powder and used in a magnetic-brush process to develop an electrostatlc charge pattern carried on an electrophotographic film. In each case good electrographic images are obtained. It is observed that better development of solid area images -Ls obtained by utilizing carrier vehicles Numbers 2-5 as described in Example 1 above which contain a quantity of elec-trically conductive particles incorporated in the ionomeric coated carrier vehicle.
0~3 In this example the ability of -the ionomeric coated carrier vehicles of the present invention to impart a relatively high net electrical charge to a toner powder is compared to a similar car- ~
rier vehicle coated with a vinylidene chloride-acrylonitrile- ;
acrylic acid terpolymeric coating material. In additon, the toner throw-off of these respective polymeric coated carrier , .
vehicles is compared. The reason for choosing the vinyliaene chloride-acrylonitrile-acrylic acid terpolymeric coated carrier vehicle for pu~poses of o~arison with the iono~eric coated carrier vehicle of ~he present invention is because the vinylidene chloride-acrylonitrile-acrylic acid terpolymeric material is known to be an extremely good poly-meric coating ma-terial for carrier vehicles. In this regard, further de-i tails concerning the use of vinylidene chloride-acrylonitrile-acrylic acid terpolymer ooated carrier vehicles is provided in~ be U.S. 3,795,617 issued March 5, 1974 entitled "Electrographic Carrier Vehicle and Devel-oper Composition -- Case B". In this example a control toner composition is utilized which comprises:
poly(4,4'-isopropylidene diphenyl-alt-ethylene carbonate) 200 g.
20 Aerosol TR (a trademark) ~is-tridecylester of sulfosuccinic acid sodium salt purchased from American Cyanamid Co~ 2 g.
Nigrosine Base (Color Index No. 50415B) 9 g.
Docosanoic Acid 7.1 g.
Carbon Black ~Sterling FT (a trademark) obtained from Cabot Corp~ 11.4 g.
Color balancing dyes 1.0 g.
In this example the net charge Q imparted to the toner powder is measured using a Farraday Cage in the following manner:
A weighed portion of each of the developers is placed in an iron tube that is covered at one end with a 200 mesh screen that re-tains all carrier particles within the tube. An air stream is then directed throuyh the tube, blowing toner particles off the carrier, through the 200 mesh screen at the exit and into a Farraday Cage condenser that is at an initial electrical potential .. . . . . .
7~3 i, .
of 0 volt as measured b~ an electrometer. As the triboelec-trically charged toner particles settle on the walls o~ the cage, their electrical potential is measured by the electrometer.
~he potentlal obtained is converted to electrical charge in micro-coulcmbs and this figure is divided by the weight in grams of the toner powder particles that have settled in the Farraday ;-Cage, thus providing the net toner charge in microcoulombs per gram. m e net toner charge is therefore the algebraic sum ~`~
of the electrical charges on the toner particles which have settled on the walls of the case. In addition, in this example the amount of toner throw-off is observed so as to obtain a comparison of toner throw-o~f between the ionomeric-coated carrier vehicle of the present invention and a carrier vehicle having the terpolymeric resin overcoat described hereinabove. ;
Toner throw-off is defined herein as the quantity of the toner powder thrown out of a particular developer mix upon mechanlcal agitation. Each of the developer compositions tested in this ~`
example contain 5 weight percent of the above-described controlled toner powder. m e remaining 95~ by weight of the developer com-20 prises a carrier vehicle. A total of three developer mixes are ~`
tested. The first developer mix (1) contains a carrier vehicle ,~
which is composed of oxidized sponge iron particles as described l~;
in Example 1 hereinabove having thereon a 0.3~ by weight resin coating of an ion:Lc makeri~1 purchased from the E. I. DuPont Company under the trademark Elvax D-1070 (which is described by the DuPont Comp~ny as an ion-linked, acid-modified ethylene inter- ;`
polymcr that is moderately ion-linked. The second developer mix (2) is similar to developer mix (1) except that the ionomeric coating material is Elvax D-1263 (A trademark of the E. I. DuPont Company which is described by DuPont as an ion-linked, acid-modified ethylene interpolymer -that is highly ion-linked). The third developer mix (3) contains a carrier vehicle which is composed of oxidized sponge iron particles as described in Example 1 hereinabove coated with a o.l~ by weight of vinylidene ,., . .. ,. .. . - ,: . . , ~
?B'~ 3 ; chloride-acrylonitrile-acrylic acid terpolymeric resin composed '~
of approximately ~o~ by weight vinylidene chloride units~ %
by weight of acrylonitrile units, and 6~ by weight of acrylic ~:
' acid units. The net,toner charge is measured for ea~h of developer ,, mixes Nos, 1 to Nos, 3 and is reported in Table 2 hereinbelow.
In addition the amount o~ toner throw-of~ observed is reported.
,~.
~Developer Net Toner Charge (microcoulombs/gram) Toner Throw-off 1~ 1 14.46 Very little , 10 throw-off 2 11.45 ' do.
~, 3 I6.89 do.
As illustrated in Table 2 hereinabove, the electro- ' ` ' graphic developer mixes of the present invention containing the lonomeric-coated carrier vehicle of the present invention impart a high net electrical charge to the toner powder and exh~bit '~, ~ very small amounts of toner throw-off, ; The invention has been described in detail with particular reference to certain preferred embodiments thereo~, but it will be understood that variations and modifica- ~:
tions can be ef~ected within the spirik and scope o~ the l, invention, ; j' ' ,, , ` .
1.
-22- ~ 1
particles of the invention is surprising and unexpected in view of the teachings of the art which suggests that by incorporating conductive particles in a polymer coated carrier vehicle~ the electrical charge imparted to the toner powder is substantially reduced, Each of the above-described carrier vehicles, i.e.
Numbers 1-5 are then admixed with 5~ by weight of a dry pigmented `!
thermoplastic resinous toner powder and used in a magnetic-brush process to develop an electrostatlc charge pattern carried on an electrophotographic film. In each case good electrographic images are obtained. It is observed that better development of solid area images -Ls obtained by utilizing carrier vehicles Numbers 2-5 as described in Example 1 above which contain a quantity of elec-trically conductive particles incorporated in the ionomeric coated carrier vehicle.
0~3 In this example the ability of -the ionomeric coated carrier vehicles of the present invention to impart a relatively high net electrical charge to a toner powder is compared to a similar car- ~
rier vehicle coated with a vinylidene chloride-acrylonitrile- ;
acrylic acid terpolymeric coating material. In additon, the toner throw-off of these respective polymeric coated carrier , .
vehicles is compared. The reason for choosing the vinyliaene chloride-acrylonitrile-acrylic acid terpolymeric coated carrier vehicle for pu~poses of o~arison with the iono~eric coated carrier vehicle of ~he present invention is because the vinylidene chloride-acrylonitrile-acrylic acid terpolymeric material is known to be an extremely good poly-meric coating ma-terial for carrier vehicles. In this regard, further de-i tails concerning the use of vinylidene chloride-acrylonitrile-acrylic acid terpolymer ooated carrier vehicles is provided in~ be U.S. 3,795,617 issued March 5, 1974 entitled "Electrographic Carrier Vehicle and Devel-oper Composition -- Case B". In this example a control toner composition is utilized which comprises:
poly(4,4'-isopropylidene diphenyl-alt-ethylene carbonate) 200 g.
20 Aerosol TR (a trademark) ~is-tridecylester of sulfosuccinic acid sodium salt purchased from American Cyanamid Co~ 2 g.
Nigrosine Base (Color Index No. 50415B) 9 g.
Docosanoic Acid 7.1 g.
Carbon Black ~Sterling FT (a trademark) obtained from Cabot Corp~ 11.4 g.
Color balancing dyes 1.0 g.
In this example the net charge Q imparted to the toner powder is measured using a Farraday Cage in the following manner:
A weighed portion of each of the developers is placed in an iron tube that is covered at one end with a 200 mesh screen that re-tains all carrier particles within the tube. An air stream is then directed throuyh the tube, blowing toner particles off the carrier, through the 200 mesh screen at the exit and into a Farraday Cage condenser that is at an initial electrical potential .. . . . . .
7~3 i, .
of 0 volt as measured b~ an electrometer. As the triboelec-trically charged toner particles settle on the walls o~ the cage, their electrical potential is measured by the electrometer.
~he potentlal obtained is converted to electrical charge in micro-coulcmbs and this figure is divided by the weight in grams of the toner powder particles that have settled in the Farraday ;-Cage, thus providing the net toner charge in microcoulombs per gram. m e net toner charge is therefore the algebraic sum ~`~
of the electrical charges on the toner particles which have settled on the walls of the case. In addition, in this example the amount of toner throw-off is observed so as to obtain a comparison of toner throw-o~f between the ionomeric-coated carrier vehicle of the present invention and a carrier vehicle having the terpolymeric resin overcoat described hereinabove. ;
Toner throw-off is defined herein as the quantity of the toner powder thrown out of a particular developer mix upon mechanlcal agitation. Each of the developer compositions tested in this ~`
example contain 5 weight percent of the above-described controlled toner powder. m e remaining 95~ by weight of the developer com-20 prises a carrier vehicle. A total of three developer mixes are ~`
tested. The first developer mix (1) contains a carrier vehicle ,~
which is composed of oxidized sponge iron particles as described l~;
in Example 1 hereinabove having thereon a 0.3~ by weight resin coating of an ion:Lc makeri~1 purchased from the E. I. DuPont Company under the trademark Elvax D-1070 (which is described by the DuPont Comp~ny as an ion-linked, acid-modified ethylene inter- ;`
polymcr that is moderately ion-linked. The second developer mix (2) is similar to developer mix (1) except that the ionomeric coating material is Elvax D-1263 (A trademark of the E. I. DuPont Company which is described by DuPont as an ion-linked, acid-modified ethylene interpolymer -that is highly ion-linked). The third developer mix (3) contains a carrier vehicle which is composed of oxidized sponge iron particles as described in Example 1 hereinabove coated with a o.l~ by weight of vinylidene ,., . .. ,. .. . - ,: . . , ~
?B'~ 3 ; chloride-acrylonitrile-acrylic acid terpolymeric resin composed '~
of approximately ~o~ by weight vinylidene chloride units~ %
by weight of acrylonitrile units, and 6~ by weight of acrylic ~:
' acid units. The net,toner charge is measured for ea~h of developer ,, mixes Nos, 1 to Nos, 3 and is reported in Table 2 hereinbelow.
In addition the amount o~ toner throw-of~ observed is reported.
,~.
~Developer Net Toner Charge (microcoulombs/gram) Toner Throw-off 1~ 1 14.46 Very little , 10 throw-off 2 11.45 ' do.
~, 3 I6.89 do.
As illustrated in Table 2 hereinabove, the electro- ' ` ' graphic developer mixes of the present invention containing the lonomeric-coated carrier vehicle of the present invention impart a high net electrical charge to the toner powder and exh~bit '~, ~ very small amounts of toner throw-off, ; The invention has been described in detail with particular reference to certain preferred embodiments thereo~, but it will be understood that variations and modifica- ~:
tions can be ef~ected within the spirik and scope o~ the l, invention, ; j' ' ,, , ` .
1.
-22- ~ 1
Claims (8)
1. In an electrographic developing composition for use in developing electrostatic charge patterns and comprising a physical mixture of magnetically attractable carrier particles and electro-scopic toner particles, the improvement wherein said carrier particles comprise cores of magnetically-attractable material having thereon a resinous coating of a polymer comprising a metal ion-linked carboxylic acid .alpha.-olefin copolymer, said .alpha.-olefin having the formula RCH=CH2 where R is an alkyl radical having from 1-8 carbon atoms, said carboxylic acid selected from the group consisting of .alpha.,.beta.-ethylenically unsaturated carboxylic acids having from 3 to about 8 carbon atoms, said copolymers having from 10 to about 90 percent of the carboxylic acid groups ionized with metal ions.
2. The invention of Claim 1 wherein said copolymer has a free acid content of less than about 2 milli-equivalents of 1N
NaOH per gram of the ion-linked copolymer based on the dry weight of said copolymer.
NaOH per gram of the ion-linked copolymer based on the dry weight of said copolymer.
3. The invention as described in Claim 1 wherein the magnetically-attractable core contains a material selected from the group consisting of iron, nickel, cobalt and alloys and mixtures thereof.
4. The invention as described in Claim 1 wherein the average size of the carrier core particle is from about 30 to about 1200 microns.
5. An electrographic developer composition comprising a mixture of from about 1 to about 10 weight percent of electroscopic toner particles and from about 90 to 99 weight percent of carrier particles wherein said carrier particles comprise cores of ferromagnetic material having thereon a coating of a polymer comprising a metal ion-linked carboxylic acid .alpha.-olefin copolymer, said .alpha.-olefin having the formula RCH=CH2 where R is an alkyl radical having from 1 to about 8 carbon atoms, said carboxylic acid selected from the group consisting of .alpha.,.beta.-ethylenically unsaturated carboxylic acids having from 3 to about 8 carbon atoms, said copolymers having from 10 to about 90 percent of the carboxylic acid groups ionized with metal ions.
6. The invention of Claim 5 wherein the ferro-magnetic material is selected from the group consisting or iron and iron alloys and wherein the average size of the carrier core particles is within the range of from about 60 to about 300 microns.
7. The invention of Claim 5 wherein said polymer comprises from about 0.001 to about 3 percent by weight of the total weight of the coated carrier particle.
8. An electrographic carrier vehicle comprising cores of magnetically-attractable material having thereon a resinous coating of a polymer comprising a metal ion-linked carboxylic acid .alpha.-olefin copolymer, said .alpha.-olefin having the formula RCH=CH2 where R is an alkyl radical having from 1-8 carbon atoms, said carboxylic acid selected from the group consisting of .alpha.,.beta.-ethylenically unsaturated carboxylic acids having from 3 to about 8 carbon atoms, said copolymers having from 10 to about 90 percent of the carboxylic acid groups ionized with metal ions.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA215,149A CA1072801A (en) | 1972-03-21 | 1974-12-03 | Electrophotographic carrier of ferromagnetic material coated with copolymer containing electrically conductive particles |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US23658472A | 1972-03-21 | 1972-03-21 | |
| US236,584 | 1972-03-21 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1087013A true CA1087013A (en) | 1980-10-07 |
Family
ID=22890104
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA163,118A Expired CA1087013A (en) | 1972-03-21 | 1973-02-07 | ELECTROPHOTOGRAPHIC CARRIER OF MAGNETICALLY ATTRACTABLE CARRIER COATED WITH A METAL ION-LINKED CARBOXYLIC ACID .alpha.-OLEFIN COPOLYMER |
Country Status (2)
| Country | Link |
|---|---|
| BE (1) | BE797132A (en) |
| CA (1) | CA1087013A (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0690355A1 (en) | 1994-06-08 | 1996-01-03 | Eastman Kodak Company | Humidity-stabilized toners and developers |
| US5604069A (en) | 1994-12-07 | 1997-02-18 | Eastman Kodak Company | Toners and developers containing ammonium trihalozincates as charge-control agents |
| US5547803A (en) | 1994-12-07 | 1996-08-20 | Eastman Kodak Company | Quaternary phosphonium trihalocuprate salts as charge-control agents for toners and developers |
| US5516616A (en) | 1994-12-21 | 1996-05-14 | Eastman Kodak Company | Quaternary ammonium salts as charge-control agents for toners and developers |
| US5508140A (en) | 1994-12-21 | 1996-04-16 | Eastman Kodak Company | Toners and developers containing quaternary phosphonium 3,5-Di-tertiary-alkyl-4-hydroxybenzenesulfonates as charge-control agents |
| EP0757294A1 (en) * | 1995-07-28 | 1997-02-05 | Eastman Kodak Company | Toner compositions including crosslinked and N-alkylsarcosine soaps |
| US5783346A (en) * | 1996-03-06 | 1998-07-21 | Eastman Kodak Company | Toner compositions including polymer binders with adhesion promoting and charge control monomers |
| US7541130B2 (en) | 2005-11-01 | 2009-06-02 | Eastman Kodak Company | Sulfone charge control agents for electrostatographic toners |
| US8435712B2 (en) | 2008-05-21 | 2013-05-07 | Eastman Kodak Company | Developer for selective printing of raised information by electrography |
-
1973
- 1973-02-07 CA CA163,118A patent/CA1087013A/en not_active Expired
- 1973-03-21 BE BE129092A patent/BE797132A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| BE797132A (en) | 1973-09-21 |
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