Conductive composite particles and processes for the preparation thereof

A process for the preparation of conductive submicron polymeric particles which comprises mixing at least one monomer with a polymerization initiator, a crosslinking component, and a chain transfer component; adding thereto an AB type block copolymer; effecting bulk polymerization until from about 10 to about 50 weight percent of the monomer has been polymerized; terminating polymerization by cooling the partially polymerized monomer; adding thereto from about 1 to about 50 weight percent of a conductive filler, or conductive fillers, followed by mixing thereof; dispersing the aforementioned mixture of conductive filler or fillers, and partially polymerized product in water containing a stabilizing component to obtain a suspension of particles with an average diameter of from about 0.05 to about 1 micron in water; polymerizing the resulting suspension by heating; and subsequently optionally washing and drying the product.

BACKGROUND OF THE INVENTION 
This invention is generally directed to submicron conductive composite 
particles and processes for the preparation thereof, and more 
specifically, the present invention relates to submicron, about 0.05 to 
about 0.99 in embodiments, conductive polymeric composite particles, each 
comprising a polymer, a conductive filler distributed evenly throughout 
the polymer matrix, and an AB block copolymer comprised of one block 
compatible with the polymer matrix, and a second block of a hydrophilic 
polymer, and with desirable charging properties residing on the copolymer 
surface that can enable either positive or negative triboelectric toner 
charge enhancement of from about 5 to about 25 microcoulombs per gram. The 
present invention also relates to processes for the preparation of 
polymeric composite particles. In embodiments, the present invention 
comprises adding to the polymer base resin selected an AB block copolymer, 
such as a copolymer of polystyrene-b-polyacrylic acid, to enhance the 
negative tribo driving characteristics thereof, and such as 
polystyrene-b-polyoxyethylene copolymer to enhance the positive tribo 
driving characteristics thereof. In embodiments, the process of the 
present invention comprises the preparation of submicron conductive 
composite particles containing AB block copolymers and carbon black. In 
one embodiment, the process of the present invention comprises the 
preparation of conductive submicron polymeric particles containing a 
conductive filler distributed substantially throughout the polymer matrix 
of the particles and an AB block copolymer to enhance tribo charging, and 
which particles can be selected as carrier powder coatings. In another 
embodiment, the process of the present invention comprises the preparation 
of conductive polymeric composite particles with an average particle size 
diameter of from between about 0.05 micron to about 1 micron. The 
conductivity of the generated submicron polymeric composite particles can 
be modified by, for example, varying the weight percent of conductive 
filler component present in effective amounts of, for example, from 
between about 1 weight percent to about 50 weight percent, and also by 
varying the composition of the conductive filler component. Thus, 
conductive submicron polymeric composite particles with a conductivity of 
from between about 10.sup.-10 (ohm-cm).sup.-1 to about 10.sup.-4 
(ohm-cm).sup.-1 can be prepared. In one process embodiment, the particles 
with average volume diameters of about 0.05 to about 1 micron are 
comprised of polymer, a conductive filler distributed evenly throughout 
the polymer matrix of the composite product or toner and an AB block 
copolymer, and which product can be obtained by a semisuspension 
polymerization method as illustrated in U.S. Pat. No. 5,043,404, the 
disclosure of which is totally incorporated herein by reference. In the 
aforementioned semisuspension polymerization processes, a mixture of 
monomer or comonomers, a polymerization initiator, a crosslinking 
component and a chain transfer component are bulk polymerized until 
partial polymerization is accomplished, for example. In one specific 
embodiment of the present invention, from about 10 to about 50 percent of 
monomer or comonomers are converted to polymer, thereafter the resulting 
partially polymerized monomer, or comonomers is cooled to cease bulk 
polymerization and to the cooled mixture of polymerized monomer, or 
comonomers is added a conductive filler, followed by mixing, using, for 
example, a high shear mixer until a homogeneous mixer, or organic phase is 
obtained. Subsequently, the resulting organic phase is dispersed in water 
containing a stabilizing component with, for example, a high shear mixer; 
then the resulting suspension is transferred to a reactor and completely 
polymerized; the content of polymerization reactor is then cooled; 
followed preferably by washing and drying the polymer product. Also, there 
is needed a simple method whereby the triboelectric charge of the coated 
xerographic carrier can be enhanced in either a positive or negative 
direction, and this is accomplished in accordance with the present 
invention by the addition of certain AB block copolymers to the polymer 
composite particle. This process using the block copolymer provides 
considerably enhanced process latitude by enabling materials with 
different triboelectric behavior to be produced using the same polymer 
matrix with a small amount of block copolymer, rather than having to 
design and develop an entirely new polymer matrix. 
Metals such as carrier cores are conductive or semiconductive materials, 
and the polymeric materials used to coat the surface of metals are usually 
insulating. Therefore, carrier particles coated completely with polymer or 
a mixture of polymers can lose their conductivity and become insulating. 
Although this is desired for some applications, for conductive magnetic 
brush systems (CMB) the carrier particles should be conductive. Since the 
carrier polymer coating can be utilized to control carrier tribo, a 
conductive carrier coating is needed to design carriers with the desired 
conductivity and triboelectrical properties. Conductive polymers can be 
very costly, and are not believed to be suitable for preparing low cost 
carrier components, for example less than $5/pound, thus a conductive 
polymer composite comprising a low cost polymer and a conductive filler, 
such as conductive carbon black, is considered a more suitable 
alternative. 
A polymer composite coating of metal materials, such as carrier beads, is 
known and can be obtained by two general approaches, solution and powder 
coating. Solution coating of carriers using a polymer composite solution 
comprised of a polymer, a conductive filler and solvent can be utilized to 
prepare conductive carrier, however, trapping of solvent in the solution 
coating adversely interferes with the use of coated materials, for example 
the residual solvent trapped in the carrier coating reduces the carrier 
life, and the release of solvent in the developer housing can cause other 
problems related to harmful effects of absorbed solvent to various copying 
machine parts and toxicity of solvent. Moreover, the solvent recovery 
operation involved in the solution coating processes is costly and can be 
hazardous. The powder coating of metal surfaces can eliminate the need for 
solvent, and therefore, many of the problems associated with solution 
coating; however, such processes require polymer powder with very small 
size, for example less than one micron in many situations. Although 
several polymer powders with desired particle size are available for 
carrier powder coating, submicron polymer composite particles containing 
conductive filler to prepare conductive coated carriers that maintain 
their triboelectrical characteristics for extended time periods exceeding, 
for example, 200,000 images are not believed to be available. Therefore, 
there is a need for conductive submicron polymeric composite particles, 
each containing a conductive filler distributed evenly throughout 
particles, and a process for preparing them, and for a simple method to be 
able to tailor the tribocharging characteristics of carrier particles. 
The preparation of polymeric particles for powder coatings can be 
accomplished primarily by three methods, namely grinding or attrition, 
precipitation and in situ particle polymerization. Grinding or attrition, 
especially fluid energy milling, of large polymeric particles or polymeric 
composite particles containing fillers to the size needed for powder 
coating, for example less than one micron, is often not desirable both 
from an economic and functional viewpoint. These materials are difficult 
to grind, and therefore, grinding or attrition of the required materials 
for coating with present milling equipment is very costly due to very low 
processing yield, for example in the range of 5 to 10 weight percent. 
Precipitation process can also be used to prepare polymeric/polymeric 
composite particles. In one approach, the polymer solution is heated to 
above its melting temperature and then cooled to form particles. In 
another process, the polymer solution is precipitated using a nonsolvent 
or the polymer solution is spray dried to obtain polymeric/polymeric 
composite particles. With all these precipitation processes, it has been 
difficult to achieve low cost and clean, that is, for example, with no or 
substantially no impurities such as solvents or precipitants in the 
resulting polymer particles. It is also difficult to obtain particles with 
small particle size and narrow particle size distribution. It is also 
difficult to control filler distribution throughout each particle's 
polymer matrix. In the in situ particle polymerization process, polymer 
particles are prepared by using suspension dispersion, emulsion and 
semisuspension polymerization. Suspension polymerization can be utilized 
to prepare polymer particles and polymeric composite particles containing, 
for example, a conductive filler. However, this process does not usually, 
for example, enable particles with a size less than five microns. Although 
emulsion and dispersion polymerization can be utilized to prepare 
polymeric particles of small size, for example less than one micron, these 
processes wherein particle formation is achieved by nucleation and growth 
do not readily enable synthesis of particles containing fillers such as 
conductive fillers. Conductive fillers, such as carbon blacks, are free 
radical polymerization inhibitors primarily reducing the rate of 
polymerization. Moreover, inclusion of fillers to obtain particles with 
evenly distributed fillers is not believed achievable with the prior art 
processes mentioned herein. 
There is disclosed in U.S. Pat. No. 4,908,665 a developing roller or 
developer carrier comprised of a core shaft, a rubber layer and a resin 
coating layer on the surface of the rubber containing conductive fillers 
for a one component developer. It is indicated in the '665 patent that the 
conductive developing roller can eliminate variation of the image 
characteristics due to the absorption of moisture for one component 
development processes. This patent discloses a developing roller for one 
component developer and does not disclose, it is believed, the preparation 
of conductive carrier beads for dry two component developer. U.S. Pat. No. 
4,590,141 discloses carrier particles for two component developer coated 
with a layer of silicon polymer using fluidized bed solution coating. U.S. 
Pat. No. 4,562,136 discloses a two component dry type developer which 
comprises carrier particles coated with a silicon resin containing a 
monoazo metal complex charging. The two component carriers described in 
the above two patents are insulating and are not believed to be 
conductive. There is disclosed in U.S. Pat. No. 4,912,005 a conductive 
carrier composition coated with a layer of resin containing a conductive 
particle by solution coating. Residual solvent trapped in the coated layer 
adversely effects the maintainability of the carrier electrical properties 
for an extended time period. 
There is disclosed in U.S. Pat. No. 3,505,434 a process wherein particles 
for fluidized bed powder coating are prepared by dispersing the polymer in 
a liquid which is heated to above the polymer melting point and stirred 
causing the polymer particles to form. The particles are then cooled below 
their melting point and recovered. However, this process does not, it is 
believed, for example, enable particles with a size of below 50 microns. 
Also, the suspension polymerization of monomer is known for the formation 
of polymer/polymeric composite particles generally in a size range of 
about 200 microns and higher. The main advantage of suspension 
polymerization is that the product may easily be recovered, therefore, 
such a process is considered economical. However, it is very difficult by 
suspension polymerization to prepare very small particles as the monomer 
droplets tend to coalesce during the polymerization process, especially in 
the initial stage of polymerization where the droplets are very sticky. 
For example, there is disclosed in U.S. Pat. No. 3,243,419 a method of 
suspension polymerization wherein a suspending agent is generated during 
the suspension polymerization to aid in the coalescence of the particles. 
Also disclosed in U.S. Pat. No. 4,071,670 is a method of suspension 
polymerization wherein the monomer initiator mixture is dispersed in water 
containing stabilizer by a high shear homogenizer, followed by 
polymerization of suspended monomer droplets. 
Further, disclosed in U.S. Pat. No. 4,835,084 is a method for preparing 
pigmented particles wherein high concentration of silica powder is used in 
the aqueous phase to prevent coalescence of the particles. There is also 
disclosed in U.S. Pat. No. 4,833,060 a process for the preparation of 
pigmented particles by dissolving polymer in monomer and dispersing in the 
aqueous phase containing silica powder to prevent coalescence of the 
particles. However, the silica powder used in both U.S. Pat. Nos. '084 and 
'060 should be removed using KOH, which is costly, and residual KOH and 
silica materials remaining on the surface affects the charging properties 
of particles. Moreover, the above patents do not disclose, it is believed, 
the preparation of submicron conductive particles. There is also disclosed 
in U.S. Pat. No. 3,954,898 a two step polymerization process for the 
preparation of a thermositting finished powder. However, this process does 
not enable, it is believed, synthesis of particles with size less than 100 
microns. Moreover, this patent does not teach the synthesis of submicron 
particles containing conductive fillers. 
As a result of a patentability search in the aforementioned U.S. Pat. No. 
5,043,404, the disclosure of which is totally incorporated herein by 
reference, there were located U.S. Pat. No. 4,486,559, which discloses the 
incorporation of a prepolymer into a monomer toner mix followed by 
emulsion polymerization; 4,680,200 and 4,702,988, which illustrate 
emulsion polymerization. It is known that submicron polymeric particles 
can be synthesized by emulsion polymerization. However, synthesis of 
submicron polymeric particles by emulsion polymerization requires a high 
concentration of emulsifier which remains in the final product and, it is 
believed, renders it humidity sensitive. Therefore, emulsion 
polymerization does not, it is believed, enable preparation of clean 
submicron polymeric particles which are insensitive to humidity. Moreover, 
in the emulsion polymerization, particle formation is controlled by 
diffusion of monomer from monomer droplet through a water phase into the 
growing particles. This mechanism, which is characteristic of emulsion 
polymerization, does not allow, it is believed, inclusion of conductive 
fillers in the polymeric particles. Furthermore, it is known that the 
addition of conductive fillers into emulsion, dispersion or suspension 
polymerization systems can cause severe inhibition which cancels or 
reduces the rate of polymerization significantly. 
Disclosed in the aforementioned U.S. Pat. No. 5,043,404, the disclosure of 
which is totally incorporated herein by reference, is a semisuspension 
polymerization process for the preparation of small polymeric particles 
which are comprised of a mixture of monomer or comonomers, a 
polymerization initiator, a crosslinking component and a chain transfer 
component which are bulk polymerized until partial polymerization is 
accomplished. The resulting partially polymerized monomer or comonomers 
are dispersed in water containing a stabilizer component with, for 
example, a high shear mixer, then the resulting suspension polymerized, 
followed by washing and drying the submicron polymeric particles. However, 
U.S. Pat. No. 5,043,404 does not, it is believed, disclose submicron 
conductive polymeric particles containing conductive fillers. 
U.S. Pat. No. 5,236,629 describes a process for the preparation of 
conductive submicron polymeric particles which comprises mixing at least 
one monomer with a polymerization initiator, a crosslinking component and 
a chain transfer component; effecting bulk polymerization until from about 
10 to about 50 weight percent of the monomer has been polymerized; 
terminating polymerization by cooling the partially polymerized monomer; 
adding thereto from about 1 to about 50 weight percent of a conductive 
filler, or conductive fillers, followed by mixing thereof; dispersing the 
aforementioned mixture of conductive filler or fillers, and partially 
polymerized product in water containing a stabilizing component to obtain 
a suspension of particles with an average diameter of from about 0.05 to 
about 1 micron in water; polymerizing the resulting suspension by heating; 
and subsequently washing and drying the product. However, the 
triboelectric charge of the polymeric particle is primarily effected by 
the type of polymer selected for the matrix and to a lesser extent the 
particular conductive additive used. The tribocharge of the coated carrier 
cannot be easily varied. To vary the triboelectric charge of the coated 
carrier using the process described in the 5,236,629 patent, it is 
necessary to formulate an entirely new product, by for example using a 
different selection of monomers. There is currently no suitable effective 
means available to vary the triboelectric charge of a single material 
without developing a completely new material or blending that material 
with one or more additional polymers. Therefore, it would be an advantage 
to have a simple means of modifying the triboelectric charge to enable 
broader design latitude while being able to preserve the essential 
identity of an existing product and without having to develop or employ 
additional materials. 
There thus remains a need for submicron conductive polymeric particles for 
which the triboelectric charge can be easily enhanced in either the 
positive or negative direction, and more specifically, conductive 
submicron polymeric particles containing conductive fillers distributed 
throughout each particle for which the triboelectric charge can be easily 
enhanced in either the positive or negative direction. Further, there is a 
need for a process to obtain conductive submicron polymer particles, each 
containing conductive fillers evenly distributed in the polymer and an AB 
block copolymer, and more specifically, there is a need for a 
semisuspension polymerization process for obtaining low cost clean and dry 
small, for example from between about 0.05 to about 1 micron in average 
diameter as determined by a scanning electron microscope, polymeric 
particles containing from about 1 to about 50 weight percent of a 
conductive filler, such as carbon black, which is evenly distributed 
throughout the polymer matrix, and containing from about 1 to about 10 
weight percent of an AB block copolymer. 
The criteria for selection of the A and B blocks of the block copolymer are 
of importance to the process of the present invention. The A block polymer 
is to be non-water soluble (less than 1 weight percent solubility in 
water); the B block polymer is to be excellent water solubility (greater 
than about 5 percent). During the particle formation and subsequent 
suspension polymerization, there exists a thermodynamic driving force for 
the block copolymer to partition such that the hydrophobic A block remains 
in the particle interior while the hydrophilic B block migrates to the 
particle surface. However, the presence of the hydrophobic A block 
prevents migration of the B block out of the particle. Because of its 
location on the particle surface, a relatively small amount of B block 
will have a significant effect on overall triboelectric charging of the 
particle. Positive or negative charging can be enhanced by appropriate 
choice of the B block polymer, for example polyacrylic acid will enhance 
negative charging while polyethylene oxide will enhance positive charging. 
The block copolymer can be prepared by any known means for preparing block 
copolymers, for example, such as ionic polymerization or group transfer 
polymerization, see the Encyclopedia of Polymer Science and Engineering, 
Volume 2, page 324, John Wiley and Sons, New York, 1984, the disclosure of 
which is totally incorporated herein by reference. 
SUMMARY OF THE INVENTION 
It is, therefore, an object of this invention to provide conductive 
submicron polymeric composite particles and processes thereof with many of 
the advantages illustrated herein. 
In another object of the present invention there are provided conductive 
submicron polymeric composites comprised of a polymer and a conductive 
filler distributed evenly throughout the polymer matrix of the composite, 
and an AB block copolymer to enhance triboelectric charging in either a 
positive or negative charge direction and processes for the preparation 
thereof. 
In yet another object of the present invention there are provided low cost, 
clean and dry conductive submicron polymeric composite particles comprised 
of from about 50 to about 99 weight percent of polymer and from about 1 to 
about 50 weight percent of conductive filler distributed throughout the 
polymer matrix of the composite as measured by TEM, and from about 1 to 
about 10 weight percent of an AB block copolymer that provides enhanced 
triboelectric charging properties, and processes for the preparation 
thereof. 
Another object of the present invention resides in conductive submicron 
polymeric composite particles with a conductivity from about 10.sup.-10 
(ohm-cm).sup.-1 to about 10.sup.-4 (ohm-cm).sup.-1 and processes for the 
preparation thereof. 
Another object of the present invention resides in conductive submicron 
polymeric composite particles with an average volume particle diameter 
size of from about 0.05 micron to about 1 micron. 
In another object of the present invention there are provided conductive 
submicron polymeric composites, which can be selected for two component 
carrier powder coatings, and processes for preparing such particles. 
In another object of the present invention there are provided simple 
processes for the formation of small conductive polymeric particles, and 
more specifically, submicron size conductive polymeric particles with 
preselected tailored triboelectric charging behavior. 
Also, in another object of the present invention there are provided simple 
and economical processes for the formation of conductive submicron 
polymeric particles that can be selected as carrier coatings, reference 
U.S. Pat. Nos. 4,937,166 and 4,935,326, the disclosures of which are 
totally incorporated herein by reference. 
Another object of the present invention resides in simple and economical 
semisuspension polymerization processes for the preparation of low cost, 
clean, and dry submicron conductive polymeric particles, and more 
specifically, submicron size conductive polymeric particles useful as 
carrier powder coatings. 
Additionally, in another object of the present invention there are provided 
as a result of the enhanced degree of control and flexibility processes 
for the preparation of polymeric particles containing a conductive filler, 
or fillers with improved flow and fusing properties, and particles that 
can be selected for conductive carrier powder coating with a triboelectric 
charge in the range, for example, of from about -40 to about +40 
microcoulombs per gram as determined by the known Faraday Cage process. 
These and other objects of the present invention can be accomplished in 
embodiments by the provision of processes for the preparation of submicron 
conductive polymer particles, each containing conductive filler or 
fillers, distributed evenly throughout the polymer matrix of the particles 
and an AB block copolymer, referred to as semisuspension polymerization 
processes in which a mixture of monomer or comonomers, a polymerization 
initiator, an optional crosslinking component and an optional chain 
transfer component together with an AB block copolymer is bulk polymerized 
until partial polymerization is accomplished, for example from about 10 to 
about 50 percent of monomer or comonomers is converted to polymer. The 
bulk polymerization is then terminated by cooling the partially 
polymerized monomer or comonomers. To the cooled partially polymerized 
product there is then added a conductive filler, followed by mixing 
thereof with, for example, a high shear homogenizer, such as a Brinkman 
homogenizer to prepare a mixture, or organic phase. The viscosity of the 
organic phase can in embodiments be an important factor in controlling 
dispersion of the conductive filler in the particles, and which viscosity 
can be adjusted by the percentage of polymer in the mixture. The 
aforementioned partially polymerized product with filler is then dispersed 
in water containing a stabilizing component with, for example, a high 
shear mixer to permit the formation of a suspension containing small, less 
than 10 microns for example, particles therein, and thereafter, 
transferring the resulting suspension product to a reactor, followed by 
polymerization until complete conversion to the polymer product is 
achieved. The polymer product can then be cooled, washed and dried. More 
specifically, the process of the present invention is comprised of (1) 
mixing a monomer or comonomers with polymerization initiators, a 
crosslinking component and a chain transfer component; (2) adding an AB 
block copolymer such that the A block is compatible with the polymer 
matrix and the B block is a hydrophilic polymer that provides enhanced 
triboelectric charging in the desired positive or negative direction; and 
effecting bulk polymerization by increasing the temperature of the 
aforementioned mixture to from about 45.degree. C. to about 120.degree. 
C. until from about 10 to about 50 weight percent of monomer or comonomers 
has been polymerized; the molecular weight of polymer in the bulk or the 
percentage of polymer present in the mixture which affects the viscosity 
of the partially polymerized monomer or comonomers can be an important 
factor in controlling conductive filler distribution in the particles; (3) 
cooling the partially polymerized monomer or comonomers and adding a 
conductive filler, followed by mixing thereof with, for example, a high 
shear homogenizer to form an organic phase; (4) dispersing the organic 
phase in from about 2 to about 5 times its volume of water containing from 
about 1 to about 5 weight percent of a stabilizing component to form a 
suspension with a particle size diameter of from about 0.05 micron to 
about 1 micron particles containing from about 1 to about 50 weight 
percent of a conductive filler, or conductive fillers using a high shear 
mixer; (5) transferring the resulting suspension to a reactor and 
polymerizing the suspension by increasing its temperature to from about 
45.degree. C. to about 120.degree. C. to allow the complete conversion of 
monomer or comonomers to polymer; (6) cooling the product and washing the 
product with, for example, water and/or an alcohol like methanol; (7) 
separating polymer particles from the water/methanol by means of 
filtration or centrifugation; and (8) drying the polymeric particles. 
One specific embodiment of the present invention comprises the preparation 
of polymeric particles, which comprises mixing at least one monomer with a 
polymerization initiator, a crosslinking component and a chain transfer 
component; adding an AB block copolymer; effecting bulk polymerization 
until from about 10 to about 50 weight percent of the monomer has been 
polymerized; adding a conductive filler thereto and mixing; dispersing the 
aforementioned product in water containing a stabilizing component to 
obtain a suspension of particles with an average diameter of from about 
0.05 to about 1 micron in water; and polymerizing the resulting 
suspension. By at least one monomer is intended to include from about 2 to 
about 20 monomers, comonomers thereof, and the like. Throughout "from 
about to about" includes between the ranges provided. 
The present invention is directed to the preparation of small conductive 
polymeric particles, that is with, for example, an average particle 
diameter in the range of from about 0.05 micron to about 1 micron, and 
preferably from about 0.1 to about 0.8 micron as measured by SEM 
containing 1 to about 50 percent and preferably 10 to 20 percent 
conductive filler distributed throughout the polymer matrix of particles, 
and with about 0.5 to 25 weight percent, and preferably from about 1 to 10 
weight percent of an AB block copolymer, and which polymer particles have 
a number and weight average molecular weight of from between about 5,000 
to about 500,000 and from between about 10,000 to about 2,000,000, 
respectively, in embodiments. 
Further, the process of the present invention is directed to the 
preparation of conductive polymeric particles of average diameter of from 
about 0.1 micron to about 0.8 micron containing 10 to 20 weight percent of 
a conductive filter and 80 to 90 weight percent of a polymeric material. 
This polymeric material can be comprised of a linear and crosslinked 
portions with a number average molecular weight of the linear portion 
being from about 5,000 to about 50,000 and a weight average molecular 
weight of from about 100,000 to about 500,000 and from 0.1 to about 5 
weight percent of a crosslinked portion, and a third portion which is an 
AB block copolymer with the number average molecular weight of the A block 
of the AB type block copolymer component being in the range of from about 
500 to about 500,000 and more preferably from about 10,000 to about 
100,000, and the number average molecular weight of the B block of the AB 
type block copolymer component being in the range from about 500 to about 
1,000,000 and, more preferably, from about 1,000 to about 50,000, and 
which polymer product is useful for carrier coatings. More specifically, 
the process of the present invention in embodiments is directed to the 
preparation of conductive polymeric particles of an average diameter in 
the range of between about 0.1 to about 0.8 micron with conductive filler 
distributed evenly throughout the resulting polymer matrix as measured by 
TEM with a linear portion having a number average molecular weight in the 
range of from about 5,000 to about 50,000, and a weight average molecular 
weight of from about 100,000 to about 500,000, and from about 0.1 to about 
5 weight percent of a crosslinked portion, and about 1 to 10 weight 
percent of an AB block copolymer. This process as indicated herein 
comprises (1) mixing a monomer or comonomers with a polymerization 
initiator with the ratio of monomer or comonomers to initiator being from 
about 100/2 to about 100/20, a crosslinking component with the ratio of 
monomers or comonomers to crosslinking component being from about 100/0.1 
to about 100/5, and a chain transfer component with the ratio of monomer 
or comonomers to the chain transfer component being from about 100/0.01 to 
about 100/1; (2) adding an AB block copolymer such that the A block is 
compatible with the polymer matrix and the B block is a hydrophilic 
polymer that provides enhanced triboelectric charging in the required 
positive or negative direction, the AB block is added with the ratio of 
monomer or monomers to AB block copolymer being from about 100/1 to about 
100/25, and the ratio of the A block to the B block being from about 
100/10 to about 10/100; (3) effecting bulk polymerization by increasing 
the temperature of the mixture to from about 45.degree. C. to about 
120.degree. C. until from about 10 to about 50 weight percent of monomer 
or comonomers has been converted to polymer with a number average 
molecular weight of from 5,000 to about 50,000 and a weight average 
molecular weight of from about 10,000 to about 40,000, and thereafter, 
adding conductive filler thereto with the ratio of filler to polymer 
monomer mixture being from about 0.1 to about 0.2, followed by extensive 
mixing to prepare organic phase; (4) dispersing the resulting organic 
phase from about 2 to about 5 times its volume in water containing from 
about 1 to about 5 weight percent of a stabilizing component, preferably 
polyvinylalcohol having a weight average molecular weight of from about 
1,000 to about 10,000 to form a suspension containing particles with a 
particle size diameter of from about 0.1 to about 0.8 micron by using high 
shear mixer; (5) transferring the resulting suspension to a reactor and 
polymerizing the suspension by increasing its temperature to from about 
45.degree. C. to about 120.degree. C. to allow the complete conversion of 
monomer or comonomers to polymer; (6) washing the resulting product with 
equal volumes of methanol and/or water from about 3 to about 5 times; (7) 
separating polymeric particles from water/methanol by means of filtration 
or centrifugation; and (8) drying of the polymeric particles. 
In an embodiment, the present invention is directed to a process for the 
preparation of conductive submicron polymeric particles, which comprises 
mixing at least one monomer with a polymerization initiator, a 
crosslinking component and a chain transfer component; adding an AB block 
copolymer with the A block being a polymer that is compatible with the 
polymeric particle matrix polymer and the B block being a hydrophilic 
polymer that provides the required enhanced charging; effecting bulk 
polymerization until from about 10 to about 50 weight percent of the 
monomer has been polymerized; terminating polymerization by cooling the 
partially polymerized monomer; adding thereto from about 1 to about 50 
weight percent of a conductive filler, or conductive fillers, followed by 
mixing thereof; dispersing the aforementioned mixture of conductive filler 
or fillers, and partially polymerized product in water containing a 
stabilizing component to obtain a suspension of particles with an average 
diameter of from about 0.05 to about 1 micron in water; polymerizing the 
resulting suspension by heating; and subsequently washing and drying the 
product. 
Illustrative examples of monomer or comonomers preferably selected in an 
amount of, for example, from about 80 to about 99 weight percent include 
vinyl monomers comprised of styrene and its derivatives such as styrene, 
.alpha.-methylstyrene, p-chlorostyrene, and the like; monocarboxylic acids 
and their derivatives such as acrylic acid, methyl acrylate, ethyl 
acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl 
acrylate, methacrylic acids, methyl methacrylate, ethyl methacrylate, 
butyl methacrylate, octyl methacrylate, acrylonitrile and acrylamide; 
dicarboxylic acids having a double bond and their derivatives such as 
maleic acid, monobutyl maleate, dibutylmaleate; vinyl esters such as vinyl 
chloride, vinyl acetate and vinyl benzoate; vinyl ketones such as vinyl 
methyl ketone and vinyl ether ketone; and vinyl ethyl ether and vinyl 
isobutyl ether; vinyl naphthalene; unsaturated mono-olefins such as 
isobutylene, and the like; vinylidene halides such as vinylidene chloride 
and the like; N-vinyl compounds such as N-vinyl pyrrole and fluorinated 
monomers such as pentafluoro styrene, allyl pentafluorobenzene and the 
like; and mixtures thereof. 
Illustrative examples of polymerization initiators selected in an amount 
of, for example, from about 0.1 to about 20 weight percent of monomer 
include azo compounds such as 2,2'-azodimethylvaleronitrile, 
2,2'-azoisobutyronitrile, azobiscyclohexanenitrile, 2-methylbutronitrile, 
and the like, and peroxide such as benzoyl peroxide, lauryl peroxide, 
1-1-(t-butylperoxy)-3,3,5-trimethylcyclohexane, 
n-butyl-4,4-di-(t-butylperoxy)valerate, dicumyl peroxide, and the like. 
Crosslinkers selected for the process of the present invention are known 
and can be comprised of compounds having two or more polymerizable double 
bonds. Examples of such compounds include aromatic divinyl compounds such 
as divinylbenzene and divinylnaphthalene; carboxylic acid esters having 
two double bounds such as ethylene glycol diacrylate, ethylene glycol 
dimethylacrylate, and the like; divinyl compounds such as divinyl ether, 
divinyl sulfite, divinyl sulfone, and the like. Among these divinylbenzene 
is particularly useful. The crosslinking component is preferably present 
in an amount of from about 0.1 to about 5 parts by weight in 100 parts by 
weight of monomer or comonomers mixture. 
Examples of conductive fillers present in effective amounts as illustrated 
herein, for example, include conductive carbon blacks such as acetylene 
black, available from Chevron Chemical, VULCAN BLACK.TM., BLACK PEARL 
L.RTM., KEYTJEN BLACK EC600JD.RTM., available from AK20, CONDUCTEX SC 
ULTRA.TM., available from Columbian-Chemical, metal oxides such as iron 
oxides, TiO, SnO.sub.2 and metal powders such as iron powder. 
Stabilizers selected in an amount of, for example, from about 0.1 to about 
5 weight percent of water are selected from the group consisting of both 
nonionic and ionic water soluble polymeric stabilizers such as methyl 
cellulose, ethyl cellulose, hydroxypropyl cellulose, block copolymer such 
as PLURONIC E87.TM. from BASF, sodium salt of carboxyl methyl cellulose, 
polyacrylate acids, and their salts; polyvinyl alcohol, gelatins, 
starches, gums, alginates, zein and casein, and the like; and barrier 
stabilizers such as tricalcium phosphate, talc, barium sulfate, and the 
like. Among these, polyvinyl alcohol with a weight average molecular 
weight of from about 1,000 to about 10,000 is particularly useful. 
Chain transfer components selected, which primarily function to control 
molecular weight by inhibiting chain growth, include mercaptans such as 
laurylmercaptan, butylmercaptan, and the like, or halogenated carbons such 
as carbon tetrachloride or carbon tetrabromide, and the like. The chain 
transfer agent is preferably present in an amount of from about 0.01 to 
about 1 weight percent of monomer or comonomer mixture. Also, stabilizer 
present on the surface of the polymeric particles can be washed using an 
alcohol such as, for example, methanol, and the like, or water. Separation 
of washed particles from solution can be achieved by any classical 
separation technique such as filtration, centrifugation, and the like. 
Classical drying techniques such as vacuum drying, freeze drying, spray 
drying, fluid bed drying, and the like can be selected for drying of the 
polymeric particles. 
Illustrative specific examples of polymer or copolymer products present in 
an amount of about 50 to about 99 weight percent containing, for example, 
both a linear and a crosslinked portion in which the ratio of crosslinked 
portion to linear portion is from about 0.001 to about 0.05, and the 
number and weight average molecular weight of the linear portion is from 
about 5,000 to about 500,000 and from about 10,000 to about 2,000,000, 
respectively, include vinyl polymers of polystyrene and its copolymers, 
polymethylmethacrylate and its copolymers, unsaturated polymers or 
copolymers such as styrene-butadiene copolymers, fluorinated polymers or 
copolymers such as polypentafluorostyrene polyallylpentafluorobenzene, and 
the like. 
Illustrative specific examples of monomers used in forming the A block of 
the AB type block copolymer component include monomers that polymerize to 
polymers with low water solubility, less than 1, and preferably about 0.5 
weight percent, for example, such as .alpha.-methyl-styrene, 
p-chlorostyrene; vinyl ketones; vinyl naphthalene; unsaturated 
monoolefins; vinylidene halides; fluorinated vinyl compounds, methyl 
acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl 
acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl 
methacrylate, octyl methacrylate, monobutyl maleate, dibutyl maleate; 
vinyl chloride, and vinyl benzoate; vinylidene chloride; pentafluoro 
styrene and allyl pentafluorobenzene. 
Illustrative specific examples of monomers used in forming the B block of 
the AB type block copolymer component include monomers that polymerize to 
polymers with high water solubilities in excess of about 5, such as about 
10 weight percent, such as acrylic acids, methacrylic acids, acrylamide, 
acrylonitrile, ethylene oxide, N-vinyl pyrrolidinone, maleic acid, 
vinylsulfonic acid, styrenesulfonic acid, 
2-acrylamido-2-methylpropanesulfonic acid, 3-vinyloxypropane-1-sulfonic 
acid, 2-methacryloyoxy ethanesulfonate, 
3-methyacryloyoxy-2-hydroxypropanesulfonate, 2-acrylamido-2-methyl 
propanesulfonate, 3-sulfo-2-hydroxypropyl methacrylate, vinylphosphonic 
acid, 4-vinylphenol, N-vinylsuccinimidic acid; diallyldimethylammonium 
chloride, diallyldiethylammonium chloride, diethylaminoethyl methacrylate, 
dimethylaminoethyl methacrylate, methacryloyoxyethyl trimethylammonium 
sulfate, methacryloyoxyethyl trimethylammonium chloride, and 
3-(methacrylamido)propyltrimethylammonium chloride. 
The resulting polymer composite particles with, for example, fillers of the 
present invention can be selected as carrier powder coatings, which 
carriers contain, for example, a steel or ferrite core, and can be admixed 
with toner compositions comprised of resin particles, pigment particles 
and optional additives such as charge control components, reference U.S. 
Pat. No. 4,560,635, the disclosure of which is totally incorporated herein 
by reference, enabling the formation of a developer composition useful in 
electrophotographic imaging processes. 
The following Examples are being submitted to further define various 
species of the present invention. These Examples are intended to be 
illustrative only and are not intended to limit the scope of the present 
invention. Also, parts and percentages are by weight unless otherwise 
indicated.

EXAMPLE I 
Methylmethacrylate monomer (200 grams) was added to 6 grams of 
2,2'-azobis(2,4-dimethylvaleronitrile), 1.6 grams of benzoyl peroxide and 
0.85 gram of divinyl benzene crosslinking agent, and mixed in a one liter 
flask using a mechanical stirrer. To this mixture were added 10 grams of 
the block copolymer polystyrene-b-polyethylene oxide. This block copolymer 
contained 40 weight percent of polystyrene and 60 weight percent of 
polyethylene oxide. The number average molecular weights of the 
polystyrene and polyethylene oxide blocks were 15,000 and 8,000, 
respectively. The mixture was bulk polymerized by heating to 45.degree. C. 
until 12 weight percent of the monomer as measured by gravimetry was 
converted to polymer. The bulk polymerization was quenched by cooling, and 
then 30 grams of CONDUCTEX SC ULTRA.RTM. carbon black were added and the 
contents were mixed using a Brinkmann Polytron homogenizer to produce a 
homogeneous organic phase mixture. This organic phase was then poured into 
a container along with 650 grams of an aqueous solution of 4 weight 
percent of polyvinyl alcohol having a weight average molecular weight of 
3,000, and the resulting mixture was then homogenized for 5 minutes to 
produce a microsuspension of polymeric particles containing carbon black 
in water. A quantity of 5.0 grams of potassium iodide was then added as an 
aqueous phase inhibitor. The resulting microsuspension was transferred to 
a 1 liter stainless steel reactor and the temperature was raised from 
25.degree. to 60.degree. C. in 35 minutes where it was held for 2 hours; 
the temperature was then increased to 85.degree. C. during a 2 hour period 
and held there for 1 hour, after which the suspension was cooled in 30 
minutes to 25.degree. C. When cooled to 25.degree. C., the suspension 
polymerization was complete as measured using gas chromatography. The 
microsuspension product was then poured into 1 liter of methanol. The 
resulting diluted suspension was centrifuged. The resulting supernatant 
liquid comprised of the diluted polyvinyl alcohol was decanted, fresh 
methanol/water 50:50 ratio was added, and the resulting mixture was mixed 
for 1 to 2 minutes at 5,000 revolutions per minute. This washing procedure 
was again repeated with deionized water. After the final wash, the product 
was freeze dried to provide dry individual particles. Scanning electron 
microscope (SEM) photomicrographs of the dry product indicated that the 
average particle size of the polymer product was 0.7 micron. The glass 
transition temperature of 113.degree. C. was measured by DSC. The polymer 
product conductivity was measured by melting one gram of product in the 
form of film, and using a conductivity meter, the results showed a 
conductivity of 10.sup.-8 (ohm-cm).sup.-1. 0.7 Gram of the resulting 
polymethyl methacrylate particles containing carbon black with block 
copolymer were mixed with 100 grams of an iron core carrier with an 
average bead diameter of 90 microns in a Munson type mixer at room 
temperature. The coated materials were then fused on the surface of the 
carrier at 350.degree. F. in a rotary kiln furnace. The product was sieved 
through a 177 micron screen to remove coarse materials. The coarse 
fraction was found to be about 0.1 weight percent. The sieved materials 
were scanned for surface coverage using SEM. The results evidenced 100 
percent surface coverage of polymer. The functional evaluation of the 
resulting carrier in the Xerox Corporation 5100 two component development 
system indicated a triboelectric charge (tribo) of 41 microcoulombs per 
gram as determined by the Faraday Cage method. 
EXAMPLE II 
Styrene monomer (200 grams) was added to 8 grams of 
2,2'-azobis(2,4-dimethylvaleronitrile), 2.0 grams of benzoyl peroxide and 
0.65 grams of divinyl benzene crosslinking agent, and mixed in a one liter 
flask using a mechanical stirrer. To this mixture were added 10 grams of a 
block copolymer of polystyrene-b-polyethylene oxide. This block copolymer 
contained 40 weight percent of polystyrene and 60 weight percent of 
polyethylene oxide. The number average molecular weights of the 
polystyrene and polyethylene oxide blocks were 15,000 and 8,000, 
respectively. The mixture was bulk polymerized by heating to 55.degree. C. 
until 16 weight percent of the monomer as measured by gravimetry was 
converted to polymer. The bulk polymerization was quenched by cooling and 
then 30 grams of CONDUCTEX SC ULTRA.RTM. carbon black were added and the 
contents were mixed using a Brinkmann Polytron homogenizer. The resulting 
organic phase was then poured into a flask, along with 650 grams of an 
aqueous solution of 4 weight percent of polyvinyl alcohol having a weight 
average molecular weight of 3,000, and the resulting mixture was then 
homogenized for 5 minutes to produce a microsuspension of polymeric 
particles containing carbon black in water. A quantity of 5.0 grams of 
potassium iodide was then added as an aqueous phase inhibitor. The organic 
phase mixture was then polymerized by heating, reference Example I. The 
same carrier coating procedure as described in Example I was then 
repeated. The coated carrier had a tribo of 19.8 microcoulombs per gram. 
EXAMPLE III 
The process of Example I was repeated except that the block copolymer 
selected was a polystyrene-b-polyacrylic acid block copolymer. This block 
copolymer contained 50 weight percent of polystyrene. The coated carrier 
had a tribocharge of 22.4 microcoulombs per gram. 
EXAMPLE IV 
The process of Example II was repeated except that the block copolymer 
selected was a polystyrene-b-polyacrylic acid block copolymer. This block 
copolymer contained 50 weight percent of polystyrene. The coated carrier 
had a tribocharge of 3.3 microcoulombs per gram. 
EXAMPLE V 
The process of Example I was repeated except that no block copolymer was 
selected. The coated carrier had a tribocharge of 29.8 microcoulombs per 
gram. 
EXAMPLE VI 
The process of Example II was repeated except that no block copolymer was 
selected. The coated carrier had a tribocharge of 12.5 microcoulombs per 
gram. 
EXAMPLE VII 
The process of Example I was repeated except that the block copolymer was a 
polystyrene-b-polymethylmethacrylate polymer comprised of 45 percent 
polystyrene. This material does not have a suitable B block as described 
herein in that polymethylmethacrylate is not sufficiently hydrophilic and 
hence will not diffuse to the particle surface. The coated carrier had a 
tribocharge of 29.1 microcoulombs per gram, which is the same charge 
resulting when no block copolymer is used (Example V). 
EXAMPLE VIII 
The process of Example II was repeated except that the block copolymer was 
a polystyrene-b-polymethylmethacrylate polymer comprised of 45 percent 
polystyrene. This material does not have a suitable B block as 
polymethylmethacrylate is not sufficiently hydrophilic and hence will not 
diffuse to the particle surface. The coated carrier had a tribo charge of 
12.9 microcoulombs per gram, which is the same charge resulting when no 
block copolymer is used (Example VI). 
EXAMPLE IX 
The process of Example I was repeated except a mixture of styrene and 
methylmethacrylate with 20 weight percent of styrene and 90 weight percent 
of methylmethacrylate comonomer was used in place of the monomers of 
Example I. The resulting submicron polymeric particles and coated carrier 
possessed properties similar to that of Example I, and wherein the 
tribocharge of the coated carrier was 18 microcoulombs per gram. 
EXAMPLE X 
The process of Example IV was repeated except styrene monomer was used. 
Submicron conductive particles and coated carrier with the same properties 
of Example IV except with a tribocharge of 5 microcoulombs per gram were 
obtained. 
EXAMPLE XI 
The process of Example IV was repeated except a mixture of 20 weight 
percent of acrylic acid and 80 weight percent of styrene comonomer was 
used. There resulted submicron conductive particles and coated carrier 
thereof with the same properties as that of Example IV except with a 
carrier tribocharge of -10 microcoulombs per gram. 
EXAMPLE XII 
The process of Example IV was repeated except pentafluorostyrene monomer 
was used. There resulted submicron conductive particles and xerographic 
coated carrier thereof with the same properties as that of Example IV 
except with a tribocharge of -25 microcoulombs per gram were obtained. 
EXAMPLE XIII 
The process of Example IV was repeated except allyl pentafluorobenzene 
monomer was used in place of methylmethacrylate monomer. There resulted 
submicron conductive particles and coated carrier thereof with the same 
properties as that of Example IV except with a tribocharge of -35 
microcoulombs per gram were obtained. 
Other modifications of the present invention may occur to those skilled in 
the art subsequent to a review of the present application. The 
aforementioned modifications, including equivalents thereof, are intended 
to be included within the scope of the present invention.