CA1329718C - Developer compositions with suspension polymerized styrene butadiene resins - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Developer compositions with toner compositions comprised of suspension polymerized styrene butadiene polymers, pigment particles, magnetites, and charge enhancing additives; and carrier components comprised of a carrier core with a coating thereover comprised of a polymer mixture with from about 10 to about 90 percent by weight of a first polymer, and from about 90 to about 10 percent by weight of a second polymer, which first and second polymers are not in close proximity in the triboelectric series.

Description

~ 132~7~8 , DEVELOPER COMPOSITION5 ITH SUSPEI~SION POLYMERIZED

BACKGROUND OF THE INYENTION
This invention is generally directed to developer compositions, and rnore specifically, the present invention relates to developer compositions wherein the toner resin particles are comprised of specific styrene butadienes. More specifically, in one embodiment of the present invention there are provided developer compositions formulated by admixing toner compositions and carrier components, and wherein the toner compositions contain therein as resin p~rticles suspension polymerized styrene butadiene as illustrated in U.S. Patent 4,558,108, the disclosure of which is totally incorporated herein by reference. Of further importance with respect to the invention of the present application is the selection of carrier particles prepared by a dry coating process wherein a mixture of certain polymers is applied to the carrier enabling insulating particles with relatively constant conductivity parameters; and also wherein the triboelectric charge on the carrier can vary significantly particle~; are illusb:ated in U.S. Patents 4,935,326 and 4,937,166. I~elc~r ca~lpositicr3s l~f the p~;ent invention possess at low (abou~ 20 percent) and high (about 80 percent) relative humidities stable triboelectric charging values for extended time periods exceeding, for example, two million imaging cycles; rapid admix characteristics; excellent blocking and fusing properties; and excellent aging ~haracteristics. The toner and developer compositions of the present invention are particularly useful in electrophotographic printing and imaging systems, especially xerographic imaging processes. Furthermore, in the aforementioned imaging processes the triboelectric charge on the carrier particles can be preselected independent of the conductivity depending, for example, on the polymer composition applied to the carrier cores.

, ., . .~ ' .
.'~ ', : , .
. .

132~7~L8 "
The electrophotographic process, and particularly the xerographic process, is well known. This process involves the formation of an elec~rostatic latent image on a photoreceptor, followed by development, and subsequent transfer of the image to a suitable substrate. Numerous different types of xerographic imaging processes are known wherein, for exampJe, insulative developer particles or conductive toner compositions are sele~ed depending on the developmen~ systems used. Moreover, of impor~ance wi~h respect to the aforementioned developer compositions are the appropria~e ~riboelectric charging values associated therewith, as it is these values that enable tontinued constant developed images of high quality and excellent resolution; and a~mixing characteristics. Thus, toner and developer compositions are known, wherein th~re are selected as the toner resin styrene acrylates, s~yrene methacrylates, and certain styrene butadienes including ~hose available as ~, Pliolites. Other resins have also been selected hr incorporation into toner .~ compositions inclusive of the polyesters as iilL~strated in lJ.S. Patent 3,590,000. Moreover, it is known that single component magnetic toners can be formulated with styrene butadiene resins, particularly those resins available as Plioli~e. In addition, pe~sitively charged toner compositions containing various resins, inclusive o~ certain styrene butadienes and ~i charge enhancing additives, are known. For example, there are described ;'1, in U.S. Pate~t 4,560,635 positively c~hargd to~r c~mpositions with distea~:yl dinethyl anano~um met~ylsulfate ~harge e~in~
ad~itiv~s. mis patent also illusk~es the utilization of ` . ~ion polym~ized st~7rene butadiene for ~corporation into tor~ cc~ositions, ref#rens~ rki~g ~le IX.
.~ ,.
, ,~
~. In additi~n, a number of different carrier particles have been .; illustrated in the prior ar~, reference for exarnple the 3,590,000 patent mentioned herein; and U.S. Patent 4,233,387, wherein coated carrier components for developer mixtures which are comprised of finely divided toner particles clinging to the surface of the carrier particles are recited.
Specifically, there are disclosed in ~he '387 patent coated carrier particles , '' ' , ' , .

~32971~

obtained by mixing carrier core particles of an average diameter af from about 30 microns to about 1,000 microns with from about 0.05 percent to :~ about 3.0 percent by weight, based on the weight of the coated carrier particles, of thermoplastic resin particles. More specifically, there are :~ illustrated in the '387 patent processes for the preparation of carrier particles by a powder coating process; and wherein the arrier particles ~: consist of a core with a coating thereover comprised of polymers. More specifically, the carrier partides selected can be prepared by mixing low density porous magnetic, or rnagneticaliy a~trac~able metai core carrier - par~icles with from, for example, between about 0.05 percent and about 3 percen1: by weight, based on the weight of the coated carrier particle of polymers until adherence thereof to the carrier core by mechanical irnpa~tion or electrostatic attraction; heating the mixture of carrier core particles and polymers to a temperature of between from about 200F to i about 550F for a period of from about 10 minutes to about 60 minutes enabling the polymers to meit and fuse to the carrier core particles;
:1 cooling the coated carrier particles; and thereafter classifying the obtained ier particll#3 to a desired ]p~ticle size~ Also, ~n a specific ~li~nt of the afore~rtioned U.S. Patents 4,935,326 ~i; and 4,937,166, th~3re are discloæd ca~ie~ particles ca[prised of :'1 a oare with a coating ~re~ver canE~rised of a mix~e of a first ` L cl~ ~i~y to ~ fi~st polymer in the triboelectric s~ries.
~i m~refc~re, the a~en~tioned carrier c~[positions ca~
11 cc ~ rised of knawn oor~ rials inclu~ling iron with a dry polymer ccating mixtNre thereover. Subseguently, developer compo6itions can kei generated by admixing the af~r~mentioned ~, carrier particles with a toner ccmpo6ition comprised of resin particles and pigment particles.
, Other U.S~ jpatents of interest include 3,939,086, .` which teaches steel carrier beads with polyethylene coatings,- see colu~n 6; 3,533,835; 3,658,500; 3,798,167; 3,918,968;
3,9~2,382; 4,238,55~; 4,310,511; 4,397,935; and 4,434,22d.
NDreover, there are illustrated in U.S. Patent 4,469,770, toner and developer compo6iti~ns wherein there is ;
~. A

`
: . . ..
. ~ .
... , . - - ~. :

~, ~32~

*~ge c~ol ~itiv~s, and rier particles axlta~ a core wi~h a coatir~ thereover of vir~ polym~s, or 2~olym~s, With further respect to carrier particl~s, recen~ efforts have foaJsed on the attainment of coatings for these partides ~r the purpose sf improviny development quality; and also to permi~ particles that can be recycled, and that do not adversely effect the imaging member in any substantial manner. I~Aany of the present commercial coatings can deteriorate rapitly, especially when sele~ed for a continuous xerographic process where the en~ire coating may separate from the carrier core in the form of chips or flakes; and fail upon impact, or abrasive contact wi~h machine parts and other carrier pa~icles. These flakes or chips, which cannot generally be reclaimed .frorn th~ developer mixture, have an adverse effect on the triboelectric charging characteristics of the carrier partides thereby providing images with lower resolutiQn in comparison to those compositions wherein the carrier coatings are retained on the surfa~e of the core sllbstra~e. Further, another problem en ountered with some prior art carrier coatings resides in fluctuating triboelectric charging characteristics, particularly with changes in relative humidity. The aforemen$ioned modifica~ion in triboelectric charging characteristics provides developed images of lower quality, and with background deposits. With the developer compositions of the present invention, these disadvantages are alleviated Furehermore, with reference to the prio!r art, carriers obtained by applying insulating resinous coatings to porous metallic carrier cores 4,~

, 132~71~

using solution coatir7g techniques are undesirable from many viewpoints.
For example, the coating materiai will usually reside in the pores of the carrier cores, rather ~han at the surfaces thereof; and therefore is not available for triboelectric charging when the coated carrier particles are mixed with finely divided toner par~icles. Attempts to resolve this problem by increasing the carrier coating weights, for example, to as much as 3 percent or greater to provide an effe~ive triboelec~rk coating to the carrier particles necessarily involves handling excessive quantities of solvents, and further usually these processes result in low product yields.
Also, solution coated carrier par~icles when combined and mixed wi~h finely divided toner particles provide in some instances triboelectric charging values which are too low for many uses. The powdær coating process selected for the carrier components of the present invention overcomes these disadvantages, and further enables developer mixtures : that are capable of generating high and useful triboelectric charging val~Jes with finely divided toner particles; and also wherein the carrier particles are o~ substantially constant conductivity. Further, when resin coated carrier particles are prepared by the powder coating process of the - ' present invention, the majority of the coating materials are fused to the carrier surface thereby reducing the number of toner impaction sites on the carrier material. Additionally, there can be achieved with the carrier par~icles of the present invention, independent of one another, desirable triboelectric charging characteristics and conductivity values; tha~ is, for example, the ~riboelectric charging parameter is not dependent on the : 1, carrier coating weight as is believed to be the situation with ~he process of U.S. Patent 4,233,387 wherein an increase in coating weight on the carrier particl~s may function to also permit an increase in the triboelectric 1:'. charging characteristics. Specifically, therefore, with the carrier compositions and process o~ the present invention there can be formulated developers with selected triboelectric charging characteristics and/or conductivity values in a number of different combinations.
Thus, for example, there can be formulated in accordance with the invention of the present application developers with breakdown : . .

1~2~7~8 voltages of ~rom about 1,000 to in excess of about 2,000 as determined in a magnetic brush conducting cell. In this device, the carrier composition or developer composition can be placed on a 1.5 inch diameter magnetic roll, followed by applying a ~/oltage across the composition, and measuring with a probe the amount of current which passes through the carrier composition or the developer cc~mposition to a rneasurement electrode for a specific applied voltage V. The measurement electrode surrounded by a grounded guard piate has a surface area of 3.0 cm2, and the developer roll to electrode spacing is usually about 2.54 millimeters. The breakdown potential is that potential at which these components begin to conduct large electrical currents, that is currents approaching û.1 milliamps. Also, the developer compositions of the present invention possess triboelectric charging vallles of from about 10 to 35 microcoulombs per gram on the carrier particles as determined by the known Faraday Cage technique.
Thus, th~ developers of the present invention can be formulated with constant conductivity values with different triboelectric charging chara~eristics by, for example, maintaining the same coating weight on the carrier particles and changing the polymer coating ratios. Similarly, there can be formulated developer compositions wherein constant triboelectric charging values are achieved, and ~he conductivities are altered by retaining the polyrner ratio coa~ing constant and modifying the coating weight for the carrier particles. Also, with the present invention there is provided toner and developer compositions w;th other improved characteristics, including superior aging properties. Thus, there is a need for developer compositions with stable charging characteristics. There is also a need for pos?tively charged toner compositions with many of the advantages indicated herein, and wherein there is selected specific styrene butadiene resins. In addition, there is a need for posi~ively charged toner compositions, especially those with magnetites therein which possess excellent blocking properties~ acceptable fusing temperature latitudes, and superior charging properties. There is also a need for toner and developer compositions possessing excellent admix charging times of, for example, less than 15 seconds; and wherein the aforementioned : - .

~32~7~

composition~ are insen~itive to relative humidities of from about 20 to about 80 percent. ~urthermore, there is a need ~or toner and developer compositions that will enable the g~neration of excellent solid areas, substantially no background deposits, and full gray ~cale reproduction of half tone images.
SUMMARY OF THE INVENTION
, It is an object of an aspect of the present invention to provide developer compositions which possess ~any of the above noted advantages.
~ In an object of an aspect of the present invention -~ there are provided developer compositions with positively charged toners containing therein suspension polymerized styrene butadiene resins.
In an object of an aspect of the present invention there are provided developer compositions comprised of toners with suspeneion polymerized styrene butadiene resins, and certain carrier particles.
Further, in an object o~ an aspect of the present j 20 invention there are provided positively charged toner compositions containing therein suspension polymerized styrene butadiene resins, ancl charge enhancing ~, additives.
Additionally in an object o~ an aspect of the '~ 25 present invention there are provided improved developers ~'' with positively charged toner compositions that possess , ., excellent electrical properties.
Moreover, in an object of an aspect of the present invention there are provided developers with stable triboelectric charging characteristics for extended time periods.
An object of an aspect o~ the present invention resides in the provision of toner compositions with excellent blocking temperatures, and acceptable fusing ; 35 temperature latitudes.
.~

, .

~32~718 Furthermore, in an object of an aspect of the present invention there are provided developer compositions containing carrier particles with a coating thereover consisting of a mix$ure of polymers that are not in close proximity in the triboelectric series.
; Also, in an object of an aspect of the present invention ther~ are provided methods for the development of electrostatic latent images with toner compositions containing therein suspension pol~merized styrene butadiene re~ins, and charge enhancing additives.
In an object of an aspect of the present invention there are provided developer compositions with carrier components obtained by a dry coating process, which particles possess substantially constant conductivity parameters, and a wide range of preselected ~, triboelectric charging values.
Furthermore, in an object of an aspect of the present invention there are provided developer compositions with carrier particles comprised of a coating with a mixture of polymers that are not in close proximity, that is for example a mixture of polymers from different positions in the triboelectric series, and wherein the toner composi.tions incorporated therein ~, possess excellent admix charging values of, for ~xample, less than 15 seconds.
An object of an aspect of the present invention resides in the provision of toner and developer compositions, which are insensitive to relative humidities of from about 20 to about 80 percent, and which compositions possess superior aging characteristics enabling their utilization for a substantial number of imaging cycles with substantially no modification of the triboelectrical properties, and other characteristics.
Additionally, in an object of an aspect of the present invention there are provided developer .' .~,, "~
~: ~ A .
.~.

13~7~8 g compositions with carrier particles possessing insulating characteristics, and comprised of a core with a coating thereover generated from a mixture of polymers.
These and other objects of the present invention are accomplished by providing developer compositions , containing therein suspension polymerized styrene - butadien~ resins. More ~pecifically, in one embodiment of the present invention there are provided developer compositions comprised of positively charged toner ~ompositions with suspension pol~merized styrene butadiene resinsl and carrier particles prepared by a powder coatinq procee ; and wherein the carrier particles are comprised of a core with a coating ;~ thereover comprised of a mixture of polymers that are not in clo~e proximity in the triboelectric series.
Thu~, in one embodiment of the present invention there are provided developer compo~itions comprised of a toner compo6ition compris~d of ~uspension polymerized ~tyrene ~, butadiene polymers, pigment particles, and charge enhancing additives; and carrier components comprised of a carrier core with a coating thereover comE~rised of a polymer mixture with from about 0 to about 90 percent by weight of a first polymer, and from about 90 to about 10 percent by weight of a second polymer, which first and second polymers are not in close proximity in the triboelectric series.
Other aspects of this invention are as follows:
Developer compositions with toner compositions comprised of suspension polymerized styrene butadiene -~ polymers, pigment particles, and charge enhancing additives; and carrier components comprised of a carrier core with a coating thereover comprised of a polymer mixture with from about 10 to about 90 percent by weight of a first polymer, and from about 90 to about 10 percent by weight of a second polymer, which first and 35 second polymers are not in close proximity in the triboelectric series.

.
.; ' "

~32~718 sa A method of imaging in accordance with claim 20 wherein the suspçnsion polymerized styrene butadiene is prepared by a process which comprises a process which comprises a process for forming a copolymer of styrene and butadiene comprising providing an aqueous phase comprising an aqueous mixture comprising a water, styrene monomer, a butadiene monomer, a suspension stabilizing agent, and a chain propagating amount of a free radical polymerization initiator insoluble in water, soluble in said styrene monomer, soiuble in said butadiene monomer, and having a 1 hour half-life between about 50C
and abou~ 130C, the ratio of said s~yrene monomer and said butadiene monomer being between about 80:20 and about 95:5 by weight with the weight proportion of water to the combination of said styrene monorner and said butadiene monorn~r being between about 8:1 and about 2:1, said suspension stabilizing agent consisting essentially of a finely-divided, difficultly water-soluble powder, and a vapor phase comprising an inert gas and butadiene monomer; heating said aqueous phase and said vapor phase to a temperature between about 50C and about 1 30C at a pressure between about 20 psi and about 140 psi in the absence of redox ini~iators and mercaptan ompounds, removing bu~adiene monomer from said vapor phace a~ter at least about 75 percent by weight of said butadiene monomer and said styrene monomer in said aqueous phase are converted to a copolymer, and prk~r to conversion of mor~ than about 98 percent by weight of said butadiene monomer and said styrene monomer to a copolymer in said aqueous phase; and heating said aqueous phase at a temperature be~ween abou~ 50C and about 130C at a pressure between about 20 psi and about 140 psi until at least about 90 percent by weight of said styrene monomer and said butadiene monomer are copolymerized to form an aqueous suspension of discrete copolymer particles having a Tg value of between about 45C and about 65C, a weight average molecular weight of between abou~ 10,000 and about 400,000, a molecular weight distribution of said copolymer between about 2 and about 9, and a butadiene monomer concentration of less than about 10 parts per million by weigh~.

!

. ' ' ' ~ ' ' `

; 9b With ~ur$her reference to the present invention, the toner ~ompositions selected are comprised of suspension pol~merized styrene butadiene resins, pigment particles, inclusive of carbon black, magnetites, and charg~ ~nhancing additives. The aforementioned suspension polymerized styrene butadiene ; resins are illustrated in U.S. patPnt 4,558,108. More specifically, these resin particles are prepared by a process which comprises forming a copolymer of styrene - 10 and butadiene comprising providing an aqueous phase comprising an aqueous mixture comprising water, styrene ~ monomer, butadiene monomer, a suspension stabilizing :~, agent, and a chain propagating amount of a free radical polymerization initiator insoluble in water, soluble in said styrene monomer, soluble in said butadiene monomer, and having a 1 hour half-life between about 50C and about 130C with th~ ratio o~ said styrene monomer and ., said butadiene monomer being between about ~0:20 and about 95:5 by weight; the weight proportion of water to ~, 20 the combination of said styrene monomer and said butadiene ~onomer being between about 8:1 and about 2:1, said suspension stabilizing agent consisting essentially ~ of a finely-divided, difficu:Lty water-soluble powder and - a vapor phase comprising an inert gas and butadiene monomer; heating said aqueous phase and said vapor phase ~ to a temperature between about 50C and about 130~C at a ~, pressure between about 20 psi and about 140 psi in the , absence of redox initiators and mercaptan compounds; removing :~' ,~

'.

_~, ,, : ~ .

-1o-132~718 butadiene monomer from said vapor phase a~er at least about 75 percent by weight o~ said butadiene rnonomer and said styrene monomer in said aqueous phase are converted to a copolymer, and prior to conversion of more than about 98 percent by weight of said butadiene monomer and said styrene monomer to a copolymer in said aqueous phase; and heating said aqueous phase at a temperature between about 50C and about 1 30C
at a pressure between about 20 psi and about 140 psi until at least about 90 percent by weight of said styrene monomer and said butadiene monomer are copolymerized to forrn an aqueous suspension of discrete copolymer partkles having a Tg (ylass transition) value of be~ween about 459C and about 65C, a weight average molecular weight of betYveell about 10,000 and about 400,000, a molecular weight distribution of said sopolymer between about 2 and about 9, and a bu~adiene monomer concentration of less than abou t 10 parts per million by weight.
The resin particles are present in a sufficient, but effective amount, thus when 10 percent by weight of pigment or colorant such as carbon black is contained therein about 90 percent by weight of resin material is selected. Generally, howev2r, providing the objectives of the present invention are achieved, the toner composition is comprised of from about 75 percent to about 95 percent by weight of toner resin particles, from about 2 percent by weight to about 20 percent by weight of pigment particles such as carbon black, and from about 0.1 to about 10 percent by weight of charge enhancing additive providing the total amoun~ of components equals about 100 percent.
Nl~merous well known suitable pigmen~s or dyes can be selected as the colorantforthe toner particles including, for example~ carbon black, nigrosin~ dye, lamp black, iron oxides, magnetites, and mixtures thereof.
The pigment, which is preferably carbon black, should be present in a sufficient amount to render the toner composition highly colored. Thus, the pigment particles are present in amounts of from abolJt 2 percent by weight to about 20 percent by weight based on the total weight of the toner composition, however, lesser or greater amounts of pigment :, .. .. .

132~718 :: , "

particles can be selected providing the objectives of the present invention are achieYed.
Various magnetites, which are comprised of a mixture of iron oxides (FeO.fep3), in most situations including ~hose commercially available such as Mapico Black, can be selected for incorporation into the toner composi1:ions il.lustrated herein. The aforementioned magne~ite particles are present in vari~us effective amounts, generally however, they are present in the toner composition in an amount of from about 10 percent by weight to about 25 percent by weight, and preferably in an amount of ~rom about 16 percent by weight to about 19 percent by weight. Other magnetites not specifically disclosed herein m.ay be selected provided the objectives of the present invention are achievable.
A numb~r of different charge enhancing additiYes may be selected fsr incorporation into the toner compositions of the present invention to enable these compositions to acquire a positive charge thereon of from, for example, a~ou1: 10 to about ~5 miaocoulombs per gram. Examples of charge enhancing additives include alkyl pyridinium halides, especially cetyl pyridiniurn chloride, reference U.S. Pa~ent 4,298,672; ~ c sulfate or sulfonate oompo6itions, reference U.S. Patent 4,338,390; dis ~ 1 dimethyl ammonium methyl sulfate, refererce U.S. Pa~ent 4,560,635; and cther similar kncwn charge e~hancing ,~ddi1:ivcs. Ihese, additives are usually ~rporated irlto the ton~ in an an~t of fram ~ o. 1 perc~t ~y wei,~ht tl~ a~aut 20 p~ent }~y we,i~ht, arKl preferably ~, ,~ditives are, p~esent in an am~t of fran abaLIt 0 . 2 p~nt ~y weight to a}~ut 5 perc~t ~y weight.
me tor~r oampositions of the pr~esent invention can be prepared by a n ~ er of knawn methods incl~ ~ melt bl ~ ing 1:he t~ner resin particles, the pigment particles or colorants, and charge enhancing additives; followed by mechanical attrition.
Other methods mclude those well kncwn in the art such as spray drying, melt dispersion, ~t . . I

',~'`
',:, ~, ... . .
. ', ' ' "' ' 132~7~8 ~12-~.
dispersion polymerization, extrusion processing, and suspension polymærization. In one dispersion polymerization method, a solvent dispersion of the resin particles and the pigment particles are spray dried under controlled conditions to result in the desired produc~.
Importan~ charac~eristics associa~ed with the toner compositions of the present invention include a blocking temperature of greater than 1 25F, and a fusing temperature lati~ude of from about 300 to about 450F. Moreover, the aforementioned toners possess stable triboelectric charging values of from about 10 ~o about 30 microcoulombs per gram for an extended numb~r of imaging cycles exceeding, for example, in some embodiments two miilion developed copies. Although it is not desired to be limited by theory, it is believed that an important factor for the slow, or substantially no degradation in the triboelectric charging values resides in the unique rheological properties of the suspension polymerized butadiene resins selected.
As carrier particles fa~ enablin~ the for~lation of h~rein ~e is 6elected those particles pr~ared ~y a pawd~
coati~ ~oess as illus~ated in U. S. Patents 4, 935, 326 and 4,937,166. ~e ~pec:ifically, the carri~r particles selectæd can be prepared by mixing low density porous magnetic, or magnetically attractable metal core carrier particles with from, for example, between about 0.05 percent and about 3 percent by weigh~
based on the weight of the coated carrier particles of a mixture of polymers not in close p-oximity in the triboQlectric series until adherence thereof to the carrier core by mechanical impaction or electrostatic attraceion; heating the mixture of carrier core particles and polymers to a tempera~ure, for example, of between from abou~ 200F to about 550F, for a period of from about 10 minutes to about 60 rninutes enabiing the polymers to melt and fuse to the carrier core particles; cooling the coated carrier particles; and thereafter classifying the obtained carrier particles to a desired particle size.

~, ' :

.. .. . ...
- . . . ~ .: :.

-13- ~ ~2 ~ 1;8 - In a specific embodiment of the present invention, there are :` provided carrier particles, especially particles with a breakdown voltage of greater than 1,000 volts, comprised of a core with a coating thereover comprised of a mixture of a first dry polymer component and a second dry polymer con~ponent. Therefore, the aforementioned carrier compositions can be comprised sf known core materials induding iron with a dry polymer coating mixture thereover. More specifically, the carrier particles selecl:ed for the developer cornpositions of the present invention, which carrier particles possess substantially stable conductivity parameters, are prepared by (1) mixing carrier cores with a polymer mixtL:re comprising from about 10 to about 90 persent by weight of a first polyrner, and from about 90 to about 10 percent by weight of a second polyrner; (2~ dry mixing the carrier core particles and $he polymer mixtur~ for a sufficient period of time enabiing the polymer mixture to adhere to the carrier core particles; (3j heating the mixture of carrier core particles and polymer mix~ure ~o a temperature of bet~veen 200F and about 550F, whereby the polymer rnixture melts and fuses to the carrier core particles; and (4) thereafter cooling the resulting coated carrier particles. Subsequently, develop~r ccmpositions o~ the present invention can be generated by admixing the aforementioned carrier particles with a ~oner composition comprised o~ resin particles and pigment particles.
Various suitable solid core carrier materials can be selected providing the objectives of the present invention are obtained.
Characteristic carrier properties of importance include those that will enable the toner particles to acquire a positive charge, and carrier cores that wiil permit desirable flow properties in the developer reservoir : present in the xerographic imaging apparatus. Also of importance with regard to the carrier core properties are, for example, suitable magnetic characteristics that will permit magnetic brush formation in magnetic brush development processes; and wherein ~he carrier cores possess ~- desirable mechanical aging characteristks. Examples of carrier cores that can be selected include iron, steel, ferri~es, magne~ites, nickel, and mix~ures thereof. Preferred carrier cores include ferrites and sponge iron, ~, .,:

.:
,~................................ . :

, :
: , , , 13~7~

.
.
ar steel grit ~rith an av~rage particle size diameter of fram aba~ 30 miis ~ a~aut 200 m~cr~ns.

~rieli;, xeference U.S. Pa~ 4,935,326 an~ 4,937,166. ~pecific examples of polymer mix~ures used are polyvinylidenefluoride with polyethylene, polymethylmethacrylate and copolyethylenevinylacetate;
copolyvinylidenefllJoride, t~tra~luoroethylene and polyethylene;
polyme~hylmethacrylate and copolyethylene vinylacetate; and polymethylmethaaylate and polyvinylidenefluoride. Other related polymer mixtur~s not specifically mentioned herein can be selected providing the obje~iYes of the presene invention are achieved.
With f~rther reference to ~he polymer coating mixture, by close proxirnity as usedl herein it is meant that the choice of the polymers -; selected are dictated by their position in the triboelectric series, ~herefore for example, one may s~lect a first poiymer with a significantly lower triboelectric charging value than the second polymer.
- The percentage of each polymer presen~ in the carrier coating mixture can vary depending on the speci~ic cornponents selected, the coating weight, and the properti~s desired. Generally, the coated polymer mixtures used contain from about 10 to about 90 percent of the firs~
polymer, and from about 90 to about 10 percent by weight of the second ~; poiymer. Preferably, there are selected mixtures o~ polymers with from about 30 to about 60 percent by weight of the firslt polymer, and from about 7û to about 40 percent by weight of a second polymer. In one emb~liment of the present invention, when a high triboelectric charging value is desired, that is exteeding 30 microcoulombs per gram, there is ~ selected frQm about 50 percent by weight of the first polymer such as a :- polyvinylidene fluoride, commercially available as Kynar 301F; and 50 percent by weight of a second polymer such as polymethylacrylate. In : ` cvntrast, when a lower ~riboelec~ric charging value is required, less than ~or example abou~ 10 microcouiombs per gram, there is seiec~ed from .

.,~.., ,' ~ , , , . ,:, 5- 132~7~8 about 30 percent by weight of the first polymer; and 70 percent by weight of the secorld poiymer.
Generally, from about 1 part to about 5 parts by weight of toner particles are mixed with from about 10 to about 300 parts by weight of the carrier particles illustrated herein enabling the formation of developer compositions.
Aiso encompassed within the scope of the present invention are colored toner compositions comprised of toner resin particles, carrier partifles, and as pigrnents or colorants present in the toner, magenta, cyan, or yellow particles as well as mixtures thereof. More specifically, illustrative examples of magenta materials that may be select2d as pigments include 1,9-dime~hyl-substituted quinacridone and anthraquinone dye identified in th~ Color Index as Cl 6072G; Cl Dispersed Red 15, a diazo dye identified in the Color Index as Cl 26050; Cl Solvent Red 19; and the like. Examples of cyan materials that may be used as pigments include copper tetra-4(octadecyl sulfonamido~ phthalocyanine; X-copper phthalocyanine pigment listed in th~ Color Index as Cl 74î60; Cl Pigment Blue; and Anthrathrene ~iue, identified in the Color Index as Cl 69810;
~Special Blue X-2137; and the iike; while illustrative examples of yellow pigments that may be selected are diarylide yeliow 3,3-dichlorobenzidene acetoacetanilides, a monoazo pigment identified in the Color Index as Cl 12700; Cl Solvent Yellow 16, a nitrophenyl amine sulfonamide identified in the Color Index as Foron Yellow SE-/GLN; Cl Dispersed Yellow 33, 2,5-dimethoxy-4-sulfonanilide phenyl~zo-4'-chloro-2,5-dimethoxy aceto-ac~anilide; Permanent Yellow F6L; and the like. These pigments are generally present in the toner composition in an amount of from about 1 weight percent to about 15 weight percent based on the weight of the toner resin particles.
In addition, the toner and developer compositions of ~he present invention may be selected for use in electrophotographic imaging processes containing therein conventional photoreceptors, including inorganic and organic photoreceptor imaging members. Examples of imaging members are selenium, selenium alloys; and selenium or selenium '`'..'.~,' :. . ... . .
,~- . : ~

, , `
:: :

~ 132~7~8 ~ - 1 6-.

alloys containing therein additives or dopants such as halogens. These imaging members are conventionally charged positively. In a printer applica~ion, the image area can be discharged by light, and a high positive elenrical DC bias applied to the development roll. This wili permit the development of the ,1:305itiVeiy charged toner onto the inorganic photorecepgor irnaging member. Furthermore, there is preferably selected organic pho~oreceptors, illustratiYe examples of which include layered photoresponsive devices . omprised of transport layers and p~ting laye~, ref~enoe U.S. Patent 4,Z65,990 an~
o~ s~milar ~ayered ~espor~sive de~ices. 3~ples of phthalocyanines. Also, there can be selected as photogenerating pigments, squaraine compounds, thiapyrillium rnaterials, and the like. As charge transport molecules there can be selected the aryl amines disclosed in the '990 paten~. These layered members are conventionally charged negatively thus requiring a positively charged ~oner. Moreover, the developer compositions of the present invention are particularly useful in electros~atsgraphic ima~ing processes and apparatuses wherein there i~
selected a moving transporting means and ~ moving charging means; and wherein ~here is selected a deflected flexible layered imaging member, refer~nce ~.S. Pater~ts 4,394,429 ar~d 4,368,970~ ~ages ~taiTled L wi~ ~ d~l~ c~ositi~ns of the p~t i~v~tion possess :~, dark, Imif~rm 601ids havin~ ~tical d~si~ies great~r ~an 1.20, elle~rt halftorles, ar~ ~harp li~e re~olution with acceptable or ~ub6ta~ially r~ bac~ deposits.
c With fur~ respect to ~e devel~ c~ositions of ~; ~e presexlt invention, in ar~ i~Qart~ en~li~t the :~ carrier coati~s in~lude t~erein o~ctive particles su~h as :~ carbon black in varia~s effective a~ts as illus~ated in ~e aforementi~ned TJ.SA Patents ~,935,326 an~ 4,937,166.

~;J ~
:

' , . ,, ~ `;' ~. '' .` i ..

-17~ 7 ~ ~3 The following examples are being supplied to further define the present invention, it being noted that these examples are intended to illustrate and not lirnit the scope of the present invention. Parts and percentages are by weight unless otherwise indicated.
With regard to the Examples that follow, the aging fixture selected consists of a developer housiny with a single development roll moving in the opposite direction as the photoreceptor drum comprised of an arsenic selenium alloy, 99 percent selenium, 1 percent arsenic, deposited on an aluminum substrate. This photoreceptor was maintained in a discharged state in that it is discharged to substantially zero volts by a fluorescent lamp and a corotron. In this device, the housing was sequentially electrically biased with 95 volts DC, and 580 volts DC to result in background development for 95 percent of the drum cycle and solid area image development for S percent of the cycle. Also, the density of the background and image patches on the photoreceptor was monitored continuously by an infrared sensor. 1he output of the sensor controls the toner dispensing systems in that this sensor determines the amount of toner that was a~ded to the developer housing, and hence to the electrostatic image. Further, the imaged toner was removed after each cycle by a brush cleaner, proceeded by dicorotron charging, in order to provide a clean selenium alloy photoreceptor for each development step.
Using this aging device, key developer composition properties were measured at different times, for example, tl and t2, including toner concentration and triboelectric charging values. Graphs of the triboelectric parameter, At = (TC + 1) tribo were then plotted as a function of aging time with one hour of aging in the aging fixture being equal to approximately 4,000 copies, which graphs can ~e used to assess developer performance. Also, unless otherwise noted, the triboelectric charge values reported were accomplished at 50 percent relative humidity, and at room temperature.
,, ~,,, :`

.

:.

. ~ : .. . .

. . .
.~

~.

132~718 :
EXAMPLE I
There was prepared by extrusion processing a magnetic toner composition containing 1 percent by weight of the charge enhancing additive distearyl dimethyl ammonium methyl sulfate, 4 percent by weight of carbon black, 16 percent by weight of Mapico Black magnetite par~icles, and 79 percent by weight of styrene butadiene resin particles, with 10 parts of styrene, and 1 part of butadiene, which resin was formulated by an 4j469,770. qhe ~C~iG~ E~rocess ~i~h ~s well kna~ i~volves W~ and Pfleid~r Oorporatian, ~y, N.J.

A developer composition was then prepared by mixing 200 grams of carrier particles, and 6 grams of ~he above prepared toner compositiorl, wherein the carrier particles were comprised of a Toniolo atomized steel core, 120 microns in diameter, containing as a coating thereon 1.25 percent of a copolymer of vinylchloride/chlorotrifluoroethylene with the coating having dispersed therein 7.5 percent of carbon black particles. Mixing was accomplished by placing the toner, and carrier particles in an 8 ounce glass jar with a tightened screw cap thereon on a paint shaker for 10 minutes. Subsequent to removal of a sample of developer composition, a standard blow off tribo measurement was affected in a Faraday Cage, and there was ~, 1~ measured on the toner a positive charge of 32 microcoulombs per gram.
-' The above prepared developer composition was then incorporated into the aging fixture indicated here, which fixture mimics the xerographic process. The charging ability of the developer at a given time is represented by At = (TC + 1) tribo, wherein TC is the toner concentration, and tribo is the triboelectric charge on the toner. Triboelectric aging for the above prepared developer evidences a rapid initial decline followed by a more gradual exponential degradation.
The exponential degradation is expressed as At2 = At~ exp [-k(t2 - t1)], wherein tl was 47 hours, t2 was 98 hours, A~, was 46.3 microcoulombs ,, .. I

- .. . . .
: . ,. , ,, ~ , . : , ,~ , .. . . . ..

; 132~71~
_19_ per gram, At2 was 28 microcoulombs per gram, and k is the degradation ra~e. For the above prepared developer the degradation rate was 0.0098 hours-l. Also, the life of this developer, which is inversely proportional to ~he dQgradation rate constant k, would be 70 hours (about 280,000 copies).

E)SAMPLIE II
A magnetic toner and developer composition was prepared by repeating the procedure of Example I wi~h the exception that there was selected in place of the emulsion polymerized s~yrene butadiene, a suspension polymerized styrene butadiene prepared by the process as illustrated in U.S. Pat~nt 4,558,108. The toner resulting possessed a triboelecl:ric charge of a positive 30 microcoulombs per gram. Also, the triboelectric aging curve was similar to that of the deYeloper of Example I
with ~he exception that the long term degradation rate k was 0.0063 hou~1, t1 was 17 hours, t2 was 72 hours, Atl was 107 microcoulombs per gram, and At2 was 73 microcoulombs per gram. For this developer, the li~e would thus be 110 hours (about 440,000 copies).
:'' EXAMF'LI~ III
~ ~ ma~etic to~ ar~ ~ve.lc~er cc~ositia~ of ~he ~.;"J, ~ imt211tion was p~pd }~ ~3atirlg the prooedure o~

~, ~ p2rticles a st~ re wit:h a coat~ ~eover of 0.7 p~rcent ~y J wei~t of a c~y mixb~e ~f 40 peroent ~y w~iqht of polyvinylidene ride available a~; Kyr~lM 301F, arxl 60 p~rcent ~y weight of ; ~ polymet~yl ~ac~ylate, ~ich particl~ re prepared as ill~s ~ atqd in U.S. Pater~ts 4,935,326 and 4,937,166. Ihe af~rementioned o~mponerts were 2dmixed for 60 minutes in a ~unson MX-l blender rokating at 27.5 RFM~ There3ft2r, the carrier p~rticles result m g were me~red at a rate of llO grams per minute into a rota~ing tube furnace, which was ~aintai~ed at a temperatNre o~ 410F. A developer composition was then prepared by ~ 200 grams of the prepared carrier particles, and 6 gzams of the toner composition of Example II in an 8 `~ :

-~- 1~71~

ounce glass jar with a tightened screw cap thereon on a paint shaker for 10 minutes. Subsequent to the removal of a sample of developer composition, a standard blow off tribo measurement was affected and ~here resulted on the toner a positive triboelectric charge of 15 microcoulombs per gram. The triboele~tric asing of this developer composition in the aging test fixture indicated that it was superior to the triboelectric aging of the developers of Examples I and Il in that there was an initial rise in At, followed by a very slow exponential degradation (k =
0.0025 hour-1) in the triboelectric aging curve. For the prepared developer of this Example, the life was 280 hours (about 1,1û0,000 copies), t1 was 67 hours, t2 was 142 hours, At1 was 211 microcoulombs per gram, and A~2 was 175 microcoulombs per gram.

EXAMPLE IV
A magnetic toner composition was prepared by repeating the procQdure of Example I with the exception that there was selected 76.5 percent of the resin, 4 percent of carbon black, 19 perceq~t of magnetite, and 0.5 percent of distearyl dimethyl ammonium methyl sulfate.
Subsequently, this toner was mixed with the carrier particles of E~sarnple III
with the exception that the coating mixture contained 35 percent by weight of Kynar 301F, and 65 percent by weight of polymethyl methacrylate. Subsequent to mixin~3 in a paint shaker for 10 minutes, the toner had a triboelectric charge thereon of 9.5 microcoulombs per gram.
In the aging fixture, this developer composition had a tribo degradation rate of 0.0021 hour-1, tl was 89 hours, t2 was 204 hours, A~l was 81 microcoulombs per gram, and A~2 was 64 microcoulombs per gram. Also, it is believed that this developer would have a life olF 330 hours, or 1 ,300,ûO0 coples.
However, when the above prepared developer was exposed to a relative humidity of 80 percent for 24 hours in a glove box at 80F, it exhibited ~ 57 percent loss in tribocharging ability, thus the triboelec~ric charge on the toner decreased from 9.5 to 4.1 microcoulombs per gram.

:`
.;

- ' ' . . . ': ~

-21- ~ 3297~8 The aforem2ntioned decreases reduce the deveioper life to 34 hours, or 135,000 copies at 80 percent relative humidity.

EXAMPLE Y
A developer composition was prepared by repeating the procedure of Exarnple Iv with the exception that there was selected the suspension polymerized styrene butadiene of Ex~mple II, and there resulted a toner with a triboelectric charge thereon o~ 17 microcoulombs per grarn, and a tribo degradation rate of only 0.0013 hour-1; and wherein t1 was 79 hours, t2 was 237 hours, Atl was 108 microcoulombs per yram, and At7 was 88 microcoulombs per gram. The life of this developer was projected to be 500 hours, or 2,000,000 copies. Additionally, the toner of this Example was placed in a glove box, and exposed to a relative humidity of 80 percent at about 80F for 24 hours, and there resulted only a 20 percent 105s for the triboelectric charge on the toner, thus reducing the developer life to 335 hours, or 1,340,000 copies from 2,000,000 copies as compared to a 57 percent charge loss for ~he ~oner of Example IV.
Addi~ionally, the admixing time was 15 seconJs subsequent to the addition of one percent of the above preparedl toner composition to the developer composition of this Exarnple.
., .i EXAMPLE VI
:P A developer composition was prepared by repeat;ng the procedure of Fxample V with the exception that there was selec~ed 15.5 - percent by weight of magnetite, and 79.5 percent by weight of the ;: suspension polymerized styrene butadiene resin. This developer was then incorporated into a high speed, greater than 70 copies per minute, xerogr~phic imaging test fixture wherein the imaging member selected was comprised of a suppor~ing subs~rate 9f Mylar overcoa~ed Wittl a photogenerating layer of trigonal selenium, 95 percent by weight, dispersed in a polycarbazole resinous binder, and as a top layer in contact : ~ with the photogenerating iayer a charge transpor~ layer of N,N'-bis(3-methylphenyl~1,1'-biphenyl-4,4' diamine molecules, 55 percent by weight, ., '~,`
., :;, --,. . . - .

- .......................... - . ... .....
. . ,. ~ .

,;~ .

~32~71~

di~pers~ in 45 ~t ~y weight of a polycar~o~ate res~
bi~ oc~ially avail~ble as Mal~ola, ref~renae U.S. P~terst 4,265,990, There resulted for 2,000,000 developed copies, smudgeproof images with no background deposits. The ~riboelectric aging of this material was very stable with values of the triboelectric parameter At r3nging from 80 to 116. The breakdown vol~age of the carrier remained in an acceptable value specificaliy unmeasurable, but greater than 1,550 volts, and ending ~2,000,000 copies) at 400 volts. No change in copy quality (no background deposits, no loss of line sharpness, and full gray scale reproduc~ion for haKtQnes) resulted for 2,000,000 copies.
~`;
EXAMPLE VXI
The toner composition of Example III was prepared into a i, developer composition by admixing carrier particles therewith comprised of an oxidized steel core, available from Toniolo lnc., with a semicontinuous dry fused coating (carrier core and coating mixed for 70 to fusi~, reference U. S . Patent 4, 233, 387 '~ ~ of 0.15 p~t lt:y weig~t of polyvL~ylidene fluoridle.
re~n voltage of ffiis carrier w less ~an 100 volts, /' which results in a si~ficant lo~s of the full gray scale `~ ~duc:ti~n fo~ half~es, an~l the trih~Plectric ~harge of ~e O~her n~difications of the present invention may occ~
to th~se skilled in the ~rt su~ent to a review of the present .` application, an~ these modifications as well as equivalents - th~eof are intend~d to be inclu~ed within the scope of t~he . ~resf~t inv~tion.
: ~
:,:

: ,~
::~
.:
. .

.~ .

. . .
.

,

Claims (29)

1. Developer compositions with toner compositions comprised of suspension polymerized styrene butadiene polymers, pigment particles, and charge enhancing additives; and carrier components comprised of a carrier core with a coating thereover comprised of a polymer mixture with from about 10 to about 90 percent by weight of a first polymer, and from about 90 to about 19 percent by weight of a second polymer, which first and second polymers are not in close proximity in the triboelectric series.

2. A developer composition in accordance with claim 1 wherein the suspension polymerized styrene butadiene polymer is comprised of from about 80 to about 90 percent by weight of styrene, and from about 20 to about 10 percent by weight of butadiene.

3. A developer composition in accordance with claim 1 wherein the suspension polymerized styrene butadiene is prepared by a process which comprises a process for forming a copolymer of styrene and butadiene comprising providing an aqueous phase comprising an aqueous mixture comprising a water, styrene monomer, a butadiene monomer, a suspension stabilizing agent, and a chain propagating amount of a free radical polymerization initiator insoluble in water, soluble in said styrene monomer, soluble in said butadiene monomer, and having a 1 hour half-life between about 50°C and about 130°C, the ratio of said styrenemonomer and said butadiene monomer being between about 80:20 and about 95:5 by weight with the weight proportion of water to the combination of said styrene monomer and said butadiene monomer being between about 8:1 and about 2:1, said suspension stabilizing agent consisting essentially of a finely-divided, difficultly water-soluble powder, and a vapor phase comprising an inert gas and butadiene monomer;
heating said aqueous phase and said vapor phase to a temperature between about 50°C and about 130°C: at a pressure between about 20 psi and about 140 psi in the absence of redox initiators and mercaptan compounds; removing butadiene monomer from said vapor phase after at least about 75 percent by weight of said butadiene monomer and said styrene monomer in said aqueous phase are converted to a copolymer, and prior to conversion of more than about 98 percent by weight of said butadiene monomer and said styrene monomer to a copolymer in said aqueous phase; and heating said aqueous phase at a temperature between about 50°C and about 130°C at a pressure between about 20 psi and about 140 psi until at least about 90 percent by weight of said styrene monomer and said butadiene monomer are copolymerized to form an aqueous suspension of discrete copolymer particles having a Tg value of between about 45°C and about 65°C, a weight average molecular weight of between about 10,000 and about 400,000, a molecular weight distribution of said copolymer between about 2 and about 9, and a butadiene monomer concentration of less than about 10 parts per million by weight.

4. A developer composition in accordance with claim 1 wherein the pigment particles are carbon black, magnetites, or mixtures thereof.

5. A developer composition in accordance with claim 1 wherein the charge enhancing additives are selected from the group consisting of alkyl pyridinium halides, organic sulfates, and sulfonates; and distearyl dimethyl ammonium methylsulfate.

6. A developer composition in accordance with claim 1 wherein the charge enhancing additive is distearyl dimethyl ammonium methylsulfate.

7. A developer composition in accordance with claim 1 wherein the polymer mixture selected is comprised of from about 30 percent by weight to about 60 percent by weight of the first polymer, and from about 70 percent by weight to about 40 percent by weight of the second polymer.

8. A developer composition in accordance with claim 1 wherein the first polymer is polyvinylidene fluoride, and the second polymer is polymethyl methacrylate.

9. A developer composition in accordance with claim 1 wherein the triboelectric charge on the toner particles is from about 10 to about 35 microcoulombs per gram.

10. A developer composition in accordance with claim 1 wherein the breakdown voltage of the carrier particles is greater than 1,000 volts.

11. A developer composition in accordance with claim 1 wherein the carrier particles are prepared by a process which comprises (1) mixing carrier cores with a polymer mixture comprising from about 10 to about 90 percent by weight of a first polymer, and from about 90 to about 10 percent by weight of a second polymer; (2) dry mixing the carrier core particles and the polymer mixture for a sufficient sufficient of time enabling the polymer mixture to adhere to the carrier core particles; (3) heating the mixture of carrier core particles and polymer mixture to a temperature of between about 200°F and about 550°F, whereby the polymer mixture melts and fuses to the carrier core particles; and (4) thereafter cooling the resulting coated carrier particles.

12. A developer composition in accordance with claim 1 wherein the suspension polymerized styrene butadiene is present in an amount of from about 70 to about 85 percent by weight.

13. A developer composition in accordance with claim 1 wherein the charge enhancing additive is present in an amount of from about 0.1 to about 10 percent by weight.

14. A developer composition in accordance with claim 1 wherein the pigment particles, exclusive of magnetites, are present in an amount of from about 0.1 to about 5 percent by weight.

15. A developer composition in accordance with claim 1 wherein the magnetite is present in an amount of from about 10 to about 25 percent by weight.

16. A developer composition in accordance with claim 14 wherein the pigment particles are carbon black.

17. A developer composition in accordance with claim 3 with a positive triboelectric charge thereon of from about 10 to about 30 microcoulombs per gram.

18. A developer composition in accordance with claim 1 with stable triboelectric charging characteristics for extended time periods.

19. A developer composition in accordance with claim 1 wherein the carrier core is selected from the group consisting of steel, iron, nickel and ferrites.

20. A method for developing images which comprises the formation of an electrostatic latent image on a photoconductive member;
developing the resulting image with the composition of claim 1;
subsequently transferring the developed image to a suitable substrate;
and thereafter permanently affixing the image thereto.

21. A method of imaging in accordance with claim 20 wherein the developer composition maintains its electrical characteristics for about two million copies.

22. A method of imaging in accordance with claim 21 wherein stability of the developer is present at a relative humidity of from about 20 to about 80 percent.

23. A method of imaging in accordance with claim 20 wherein the suspension polymerized styrene butadiene polymer is comprised of from about 80 to about 90 percent by weight of styrene, and from about 20 to about 10 percent by weight of butadiene.

24. A method of imaging in accordance with claim 20 wherein the suspension polymerized styrene butadiene is prepared by a process which comprises a process which comprises a process for forming a copolymer of styrene and butadiene comprising providing an aqueous phase comprising an aqueous mixture comprising a water, styrene monomer, a butadiene monomer, a suspension stabilizing agent, and a chain propagating amount of a free radical polymerization initiator insoluble in water, soluble in said styrene monomer, soluble in said butadiene monomer, and having a 1 hour half-life between about 50°C
and about 130°C, the ratio of said styrene monomer and said butadiene monomer being between about 80:20 and about 95:5 by weight with the weight proportion of water to the combination of said styrene monomer and said butadiene monomer being between about 8:1 and about 2:1, said suspension stabilizing agent consisting essentially of a finely-divided, difficultly water-soluble powder, and a vapor phase comprising an inert gas and butadiene monomer; heating said aqueous phase and said vapor phase to a temperature between about 50°C and about 130°C at a pressure between about 20 psi and about 140 psi in the absence of redox initiators and mercaptan compounds, removing butadiene monomer from said vapor phase after at least about 75 percent by weight of said butadiene monomer and said styrene monomer in said aqueous phase are converted to a copolymer, and prior to conversion of more than about 98 percent by weight of said butadiene monomer and said styrene monomer to a copolymer in said aqueous phase; and heating said aqueous phase at a temperature between about 50°C and about 130°C at a pressure between about 20 psi and about 140 psi until at least about 90 percent by weight of said styrene monomer and said butadiene monomer are copolymerized to form an aqueous suspension of discrete copolymer particles having a Tg value of between about 45°C and about 65°C, a weight average molecular weight of between about 10,000 and about 400,000, a molecular weight distribution of said copolymer between about 2 and about 9, and a butadiene monomer concentration of less than about 10 parts per million by weight.

25. A method of imaging in accordance with claim 20 wherein the developer composition contains as the pigment particles carbon black, magnetites, or mixtures thereof.

26. A method of imaging in accordance with claim 20 wherein the charge enhancing additives for the toner are selected from the group consisting of alkyl pyridinium halides, organic sulfates, and sulfonates; and distearyl dimethyl ammonium methylsulfate.

27. A method of imaging in accordance with claim 20 wherein the charge enhancing additive for the toner is distearyl dimethyl ammonium methylsulfate.

28. A method of imaging in accordance with claim 20 wherein the polymer mixture selected is comprised of from about 40 percent by weight to about 60 percent by weight of the first polymer, and from about 60 percent by weight to about 40 percent by weight of the second polymer.

29. A method of imaging in accordance with claim 20 wherein the image is affixed at a temperature of from about 300 to about 450°F.