Toner compositions with a crosslinked resin component

A developer composition comprised of crosslinked styrene copolymers with an insoluble gel content of from about 20 to about 60 percent, pigment particles, low molecular weight wax components, first external additive particles of collodial silica, second external additive particles of fatty acid metal salts, and carrier particles.

BACKGROUND OF THE INVENTION 
This invention is generally directed to toner and developer compositions. 
More specifically, the present invention relates to toner compositions 
containing a highly crosslinked styrene resin. In one embodiment, thus 
there are provided in accordance with the present invention toner 
compositions comprised of highly crosslinked styrene methacrylate, or 
styrene acrylate resin particles, pigment particles, low molecular weight 
wax components, first additive particles, and second additive particles. 
Also, in another embodiment of the present invention developer 
compositions are formulated by admixing the aforementioned toners with 
carrier particles, preferably uncoated ferrites. The toner and developer 
compositions of the present invention are particularly useful in 
electrophotographic printing, and imaging methods, especially xerographic 
processes with soft roll fusers, and wherein release agents, such as 
silicone oils selected to prevent toner particles from adhering to the 
surface of fuser rolls, are avoided. 
Toner compositions with crosslinked resins are known, for example, in U.S. 
Pat. No. Re. 31,072 (a reissue of 3,938,992), a toner composition with 
styrene crosslinked resin particles is disclosed, which resins are 
crosslinked to a sufficient extent to extend the useful fusing range by at 
least 10.degree. C. as compared to uncrosslinked toner resins. Developer 
compositions and modifying materials for the toner are also disclosed in 
the '992 patent, see column 14, beginning at line 47, for example. A 
similar disclosure is presented in U.S. Pat. No. 3,941,898, the disclosure 
of which is totally incorporated herein by reference. In addition, there 
are illustrated in U.S. Pat. No. 4,513,074, the disclosure of which is 
totally incorporated herein by reference, stable conductive developer 
compositions comprised of first resin particles of styrene methacrylate 
copolymers grafted with, or containing a low molecular wax composition; 
second resin particles of a styrene, acrylate, acrylonitrile terpolymer; 
pigment particles; colloidal silica additive particles; fatty acid metal 
salt additives; and uncoated ferrite particles. The developer compositions 
of the present invention are similar to those illustrated in the 
aforementioned patent with the primary exception that there is selected in 
place of the first resin, and second resin particles a crosslinked styrene 
resin as illustrated hereinafter, which enables the formation of a more 
economical toner, and also provides other advantages. 
Further, there are described in U.S. Pat. No. 4,604,338 positively charged 
dry toner compositions with colored pigments excluding black, which 
compositions contain first resin particles, second crosslinked resin 
particles, a low molecular weight wax, and certain charge enhancing 
additives. Additionally, toner and developer compositions, especially 
those containing charge enhancing additives, are well known, reference for 
example, U.S. Pat. Nos. 3,893,935; 3,944,493; 4,007,293; 4,079,014 and 
4,394,430. Further, there is disclosed in U.S. Pat. No. 4,338,390 
developer and toner compositions having incorporated therein as charge 
enhancing additives organic sulfate and sulfonate substances. A similar 
disclosure is present in U.S. Pat. No. 4,394,430. Moreover, there are 
disclosed in U.S. Pat. No. 4,298,672 positively charged toner compositions 
with resin particles and pigment particles; and as a charge enhancing 
additive, alkyl pyridinium compounds, inclusive of cetyl pyridinium 
chloride. 
Additionally, toner and developer compositions useful in xerographic 
imaging processes, wherein silicone oils are not needed, are known, 
reference for example U.S. Pat. No. 4,556,624, the disclosure of which is 
totally incorporated herein by reference. In this patent, there are 
disclosed improved positively charged toner compositions comprised of a 
polyblend mixture of crosslinked copolymer compositions, a second polymer, 
pigment particles, and a particular wax component thereby enabling the 
toner compositions to be selected for imaging systems wherein release 
fluids are not required. The types of resin described in this patent and 
other patents relating to toner compositions, including those compositions 
useful in imaging methods without the need for release agents are 
polyamides, epoxies, diolefins, polyurethanes, vinyl resins, and polymeric 
esterification products of a dicarboxylic acid and a diol comprising a 
diphenol. Specific examples of known vinyl resins include homopolymers or 
copolymers of two or more vinyl monomers. Typical vinyl monomers are 
styrene, p-chlorostyrene, unsaturated mono-olefins such as ethylene, 
propylene, butylene, isobutylene and the like; vinyl esters such as esters 
of monocarboxylic acids including methyl acrylate, ethyl acrylate, 
n-butylacrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate, 
2-chloroethyl acrylate, phenyl acrylate, methylalphachloroacrylate, methyl 
methacrylate, ethyl methacrylate, butyl methacrylate, and other similar 
acrylates; acrylonitrile, methacrylonitrile, acrylimide; vinyl ethers, 
such as vinyl methyl ether, vinyl isobutyl ether, vinyl ethyl ether, and 
the like; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, 
and methyl isopropenyl keton; and N-vinyl indole, N-vinyl pyrrolidene, and 
the like; styrene butadiene copolymers; and mixtures thereof. 
As preferred toner resins illustrated in the '624 patent, there can be 
selected styrene polymers and the esterification products of a 
dicarboxylic acid, and a diol comprising a diphenol. The aforementioned 
polyesters are illustrated in U.S. Pat. No. 3,590,000. Other specific 
preferred toner resins include styrene/methacrylate copolymers, 
styrene/butadiene copolymers, polyester resins obtained from the reaction 
of bisphenol A and propylene oxide, followed by the reaction of the 
resulting product with fumaric acid, branched polyester resins resulting 
from the reaction of dimethylterephthalate, 1,3-butanedil, 
1,2-propanediol, and pentaerythritol; and styrene butadiene copolymers 
prepared by a suspension polymerization process, reference U.S. Pat. No. 
4,558,108. 
Furthermore, illustrated in U.S. Pat. No. 3,418,354 are processes for 
obtaining olefin-polyoxyalkylene copolymers by a graft reaction with a 
peroxide whereby there are generated free radical sites on the backbone 
polymer. One process embodiment disclosed in the '354 patent involves the 
addition of an alpha olefin such as styrene, and a peroxide to a 
polyoxyalkylene compound, such as a siloxane, wherein there results a 
graft copolymer; and more specifically, an olefin-polyoxyalkylene graft 
copolymer, see column 2, line 23. In Japanese Patent Publication No. 
46-9355, there is disclosed a procss for the preparation of graft block 
copolymers with a polysiloxane chain by the reaction of a functional 
polysiloxane with a polymer obtained from the anion polymerization of a 
styrene or a butadiene. Japanese Patent Publication No. 58-225103 
discloses a method for the crosslinking of a thermoplastic resin by the 
reaction of a hydrogenated styrene-butadiene-styrene block copolymer with 
a silane in the presence of organic peroxides. Further, in U.S. Pat. No. 
3,691,257 there are disclosed organic polymers modified by incorporating 
therein a polymer siloxane organic block copolymer; while Japanese Patent 
Publication No. 57-187345 describes a rubber modified styrene resin 
prepared by continuous bulk polymerizations in the presence of organic 
polysiloxanes and 1,2-vinyl polymers. 
Other representative patents primarily of background interest include U.S. 
Pat. No. 4,237,257 relating to methods for preparing low molecular weight 
styrene series polymers useful as toners, which preparation involves the 
selection of an organic peroxide initiator; U.S. Pat. No. 4,339,337 
relating to a suspension polymerization method for the preparation of 
magnetic beads from vinyl aromatic polymers, including styrenes, and where 
benzoyl initiators may be selected, reference column 3, line 17. 
Additionally, this patent indicates that a crosslinking monomer, reference 
divinylbenezene, may be added, reference column 2, line 39; and U.S. Pat. 
No. 4,617,249 relating to toners with a crosslinking compound, reference 
for example column 4, lines 42 to 64. 
However, there is a need for new toner resins that possess desirable 
characteristics, and that are useful in electrophotographic imaging 
systems. Additionally, there is a need for economical toner compositions 
wherein a highly crosslinked single styrene resin is selected enabling 
toners for incorporation into xerographic imaging apparatus where fixing 
can be accomplished without the utilization of release fluids, and the 
apparatus associated therewith. There is also a need for toner 
compositions which are useful in the development of images, and wherein 
fixing is accomplished without the need for release fluids. In addition, 
there is a need for resins useful for the formulation of toner 
compositions that possess desirable mechanical properties, stable 
electrical properties, excellent fusing characteristics, and acceptable 
release properties. Moreover, there is a need for developer compositions 
containing therein the toner components illustrated herein, and carrier 
particles. There is also a need for imaging and printing methods wherein 
there are selected toner and developer compositions containing therein the 
compositions illustrated herein, and wherein release fluids, such as 
silicone oils, are avoided during the fusing process. Moreover, there is a 
need for developer compositions containing therein a toner with specific 
crosslinked styrene resins, which toners possess relatively low fusing 
temperatures, 350.degree. F. for example, while maintaining high offset 
temperatures, 420.degree. F. or greater for example. Additionally, there 
remains a need for improved toner compositions that are compatible with 
fusing rolls incorporated into imaging apparatuses, especially Viton fuser 
rolls. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide toner compositions with 
the above noted advantages. 
In another object of the present invention there are provided toner 
compositions containing a single highly crosslinked styrene resin admixed 
with other components. 
In still a further object of the present invention there are provided toner 
compositions with stable triboelectric charging characteristics, that is 
for example these toners possess a tribo of from about a-5 to about a-30 
microcoulombs per gram. 
Another object of the present invention resides in the provision of toner 
and developer compositions that can be selected for imaging processes 
wherein the utilization of release fluids are avoided. 
In a further object of the present invention there are provided specific 
toner compositions and processes, which are compatible with Viton fuser 
rolls. 
These and other objects of the present invention are accomplished by 
providing toner and developer compositions which retain their electrical 
characteristics for extended time periods, and wherein the compositions 
can be utilized in electrophotographic imaging apparatus while avoiding 
the use of release fluids, such as silicone oils. More specifically, there 
are provided in accordance with the present invention toner compositions 
comprised of highly crosslinked styrene acrylates or styrene 
methacrylates, preferably with a gel content of from about 20 to about 60 
percent; pigment particles; a low molecular weight wax component; first 
additive colloidal silica particles; and second additive particles 
comprised of the metal salts of fatty acids or fatty acids. In another 
embodiment of the present invention, there are provided developer 
compositions comprised of the forementioned toners, and carrier particles 
that are preferably free of any polymeric coatings thereover. 
Illustrative examples of resins selected, which resins are crosslinked, for 
the toner compositions of the present invention include polyesters, 
diolefin polymers such as styrene butadiene resins, styrene/methacrylates, 
polyamides, epoxies, polyurethanes, vinyl resins, and the like, reference 
U.S. Pat. No. 4,604,338, the disclosure of which is totally incorporated 
herein by reference. Particularly preferred resins selected for the toner 
and developer compositions of the present invention are comprised of 
crosslinked co and terpolymers of styrene acrylates and styrene 
methacrylates, and wherein the crosslinking component selected is usually 
divinylbenzene. 
The aforementioned resins are crosslinked with various components including 
aromatic, and nonaromatic substances such as divinyl benzene, ethylene 
glycol, dimethyl acrylate, glycol dimethacrylates, and the like. It is 
important that the resin particles be crosslinked to enable the 
undesirable offsetting of the toner image to the fuser rolls, extended 
fuser wearability, and improved release associated with the transfer of 
the developer image from the imaging member to a suitable substrate, such 
as paper. Crosslinked resins that may be selected for the toner 
compositions of the present invention are illustrated in U.S. Pat. No. 
4,556,624, the disclosure of which is totally incorporated herein by 
reference. Specifically, thus there are selected for the toner 
compositions of the present invention crosslinked copolymers or 
terpolymers of styrene acrylates and styrene methacrylates, or mixtures 
thereof, which resins generally have an insoluble gel content of from 
about 20 to about 60 percent as determined by solvent extraction 
techniques with, for example, toluene or tetrahydrofuran solvents. 
Moreover, during formulation of the crosslinked resins there is usually 
added prior to polymerization a free radical polyerization initiator such 
as benzyl peroxide, which initiator is present in an effective amount 
depending on the amounts of the other components. For example, the ratio 
of initiator to crosslinking component is approximately, in a preferred 
embodiment, 10:1; and more specifically, in a very preferred embodiment, 
about 1.0 percent by weight of initiator based on the weight of the 
monomer, and 0.1 percent by weight of the crosslinking component are 
selected. Other preferred amounts include 3.0 percent by weight of 
initiator and 0.3 percent by weight of crosslinking agent and 4.6 percent 
by weight of initiator and 0.4 percent by weight of crosslinking compound. 
In one illustrative embodiment, the crosslinked resins of the present 
invention are prepared by reacting in water insitu monomers with the 
crosslinking component and initiator, such as benzoyl peroxide, at a 
temperature of from about 40.degree. to about 90.degree. C.; followed by 
cooling to room temperature, and separation of the resulting beads from 
the water phase, which beads are then dried. Generally, from about 45 to 
about 55 percent by weight of monomer, such as styrene, and 55 to 45 
percent by weight of the second monomer, such as methacrylate, are 
suspended with a suitable suspending agent, such as tricalcium phosphate, 
0.5 percent by weight, in water at a ratio of about 1.4 parts water to 1 
part of monomer mixture. 
The aforementioned illustrated resins can be formulated into toner 
compositions, including colored toner compositions, by adding thereto 
pigment partices such as carbon black, cyan, magenta, yellow, red, green, 
blue, or mixtures thereof, and the like, in an amount of from about 1 to 
about 20 percent by weight. Numerous well known suitable pigments or dyes 
can be selected as the colorant for the toner particles including, for 
example, carbon black, nigrosine dye, aniline blue, 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 enabling the formation of a clearly visible image on a 
suitable recording member. Generally, the pigment particles are present in 
amounts of from about 1 percent by weight to about 20 percent by weight, 
and preferably from about 8 to about 20 percent by weight, based on the 
total weight of the toner composition; however, lesser or greater amounts 
of pigment particles can be selected providing the objectives of the 
present invention are achieved. 
In addition, as indicated herein the pigment particles can also be selected 
from cyan, magenta, yellow, blue, red, green, and other similar colored 
pigments, or mixtures thereof, enabling the formation of colored toner 
compositions. These pigments are generally present in the toner 
compositions in an amount of from about 2 percent by weight to about 30 
percent by weight. Illustrative examples of cyan, magenta and yellow 
pigments that can be selected include, for example, 
2,9-dimethyl-substituted quinacridone and anthraquinone dyes identified in 
the Color Index as Cl 60710, Cl dispersed Red 15, a diazo dye identified 
in the Color Index as Cl 26050, Cl Solvent Red 19, and the like. 
Illustrative examples of cyan materials that may be used as pigments 
include copper tetra-4-(octadecyl sulfonamido) phthalocyanine, X-copper 
phthalocyanine pigment listed in the Color Index as Cl 74160, Cl Pigment 
Blue, and Anthrathrene Blue, identified in the Color Index as Cl 69810, 
Special Blue X-2137, and the like, while illustrative examples of yellow 
pigments that may be selected include diarylide yellow 
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 yYellow 33,2,5-dimethoxy-4-sulfonanilide 
phenylazo-4'-chloro-2,5-dimethoxy acetoacetanilide, Permanent Yellow FGL, 
and other similar compositions. 
Examples of waxes, which are available from Allied Chemical, Petrolite, 
Inc., and Sanyo, Inc., are generally present in an amount of from about 
0.5 to about 15 percent by weight. Generally, these waxes possess a weight 
average molecular weight of from about 500 to about 20,000, and preferably 
from about 1,000 to about 5,000, such as polyethylenes and polypropylenes, 
reference U.S. Pat. No. 4,604,338, and British No. 1,442,835, the 
disclosures of which are totally incorporated herein by reference. 
The toner and developer compositions of the present invention also contain 
therein first and second external additive components, the first additive 
component being comprised of silica particles, and the second additive 
components being comprised of fatty acids, or fatty acid metal salts 
thereof. Examples of silicas include Aerosil R972, reference U.S. Pat. No. 
3,983,045, the disclosure of which is totally incorporated herein by 
reference, and the like; while examples of the second additives are zinc 
stearate, calcium stearate, and the like, reference for example U.S. Pat. 
Nos. 3,590,000 and 3,320,169, the disclosures of which are totally 
incorporated herein by reference. These additives are usually present in 
an amount of from about 0.5 to about 1 percent by weight, and preferably 
0.7 percent by weight. These additives are added subsequent to the 
preparation of the toner compositions. 
Illustrative examples of carrier particles that can be selected for mixing 
with the toner of the present invention, thus enabling developer 
compositions, include those particles that are capable of 
triboelectrically obtaining a charge of opposite polarity to that of the 
toner particles. Accordingly, the carrier particles of the present 
invention can be selected so as to be of a negative or positive polarity, 
allowing the toner particles which are positively or negatively charged to 
adhere to and surround the carrier particles. Illustrative examples of 
carrier particles include methyl methacrylate, glass, steel, nickel, iron, 
ferrites, and the like. Additionally, there can be selected as carrier 
particles nickel berry carriers as illustrated in U.S. Pat. No. 3,847,604, 
the disclosure of which is totally incorporated herein by reference, which 
carriers are comprised of nodular carrier beads of nickel characterized by 
surfaces of reoccurring recesses and protrusions thereby providing 
particles with a relatively large external area. The selected carrier 
particles can be used with or without a coating, the coating generally 
being comprised of fluoropolymers, such as polyvinylidenefluoride resins, 
terpolymers of styrene, methylmethacrylate, and a silane, such as vinyl 
triethoxysilane, tetrafluoroethylenes, copolymers available as FP 461, 
other known coatings, and the like. Preferred are the uncoated ferrites 
illustrated in U.S. Pat. No. 3,914,181, the disclosure of which is totally 
incorporated herein by reference. 
While the diameter of the carrier particles can vary, generally it is from 
about 50 microns to about 1,000 microns, thus allowing these particles to 
possess sufficient density and inertia to avoid adherence to the 
electrostatic images during the development process. The carrier particles 
can be mixed with the toner composition in various suitable combinations, 
however, best results are obtained when about 1 part to about 10 parts 
toner to about 200 parts by weight of carrier are selected. 
The toner compositions of the present invention can be prepared by a number 
of known methods including melt blending the toner resin particles 
containing the pigment particles and wax, followed by mechanical 
attrition. Thereafter, the first and second additive particles are added 
thereto. Other methods include those well known in the art such as spray 
drying, melt dispersion, dispersion polymerizations, suspension 
polymerizations, and extrusion processes. 
Also, the toner and developer compositions of the present invention may be 
selected for use in developing images in electrophotographic imaging 
systems containing therein conventional photoreceptors, such as selenium, 
and selenium alloys. Illustrative examples of layered photoresponsive 
devices, which can be selected for use with the toner and developer 
compositions of the present invention include those comprised of transport 
layers and photogenerating layers, reference U.S. Pat. No. 4,265,990, the 
disclosure of which is totally incorporated herein by reference. Examples 
of generating layers include trigonal selenium, metal phthalocyanines, 
metal free phthalocyanines, squaraine pigments and vanadyl 
phthalocyanines; while examples of charge transport layers include the 
aryl amines as disclosed in U.S. Pat. No. 4,265,990. With negatively 
charged layered imaging members, there are incorporated into the toner 
compositions charge enhancing additives such as alkyl pyridinium halides, 
distearyl dimethyl ammonium methyl sulfate, and the like. These additives, 
which are present in an amount of from about 0.1 percent to about 15 
percent by weight, are selected since the layered imaging members are 
usually negatively charged, thus positively charged toner compositions are 
needed.

The following examples are being supplied to further define various species 
of the present invention, it being noted that these examples are intended 
to illustrate and not to limit the scope of the present invention. Parts 
and percentages are by weight unless otherwise indicated. 
EXAMPLE 1 
A crosslinked styrene methacrylate copolymer composition was prepared by 
bead suspension as described herein, which composition was comprised of 51 
parts of a styrene monomer, 49 parts of n-butyl methacrylate monomer, 4.6 
parts of benzoyl peroxide, and 0.4 parts of divinylbenzene. This resin had 
an insoluble gel content of 30 percent as determined by solvent extraction 
with toluene. 
Thereafter, a toner composition was formulated by admixing the above 
prepared styrene n-butyl methacrylate crosslinked resin particles, 84 
percent by weight, with 6 parts by weight of polypropylene wax, available 
from Sanyo, Inc., which wax is believed to have a weight average molecular 
weight of about 5,000; and 10 parts by weight of carbon black, which 
preparation involved melt mixing in a Banbury apparatus. 
There was added, subsequent to removal of the above toner from the Banbury, 
after roll milling, jetting, and classification to remove toner particles 
with an average diameter of 5 microns or less thereby resulting in toner 
particles with a volume average of 11.5 to 13.5 microns, to the prepared 
toner composition 0.7 percent by weight of Aerosil R972, and 0.7 percent 
by weight of zinc stearate as external additives. This toner composition 
had a low fusing temperature of 350.degree. F. 
Thereafter, there was prepared a developer composition by admixing two 
parts by weight of the above prepared toner composition with 98 parts by 
weight of ferrite carrier particles. The toner composition had a 
triboelectric charge thereon of -15 microcoulombs per gram as determined 
in a Faraday Cage apparatus. 
The above prepared developer was then incorporated into a xerographic 
imaging test fixture containing a positively charged selenium 
photoconductor, and there resulted for 50,000 imaging cycles images of 
excellent resolution with no background deposits. Moreover, no toner 
offsetting at 420.degree. F. to the fuser roll in the imaging test fixture 
was observed; it being noted that this fixture did not contain any 
silicone oil release fluid. 
EXAMPLE II 
A toner and developer composition was prepared by repeating the procedure 
of Example I with the exception that there was selected a crosslinked 
styrene n-butyl methacrylate resin with an insoluble gel content of 40 
percent, and substantially similar results were achieved. 
Other modifications of the present invention may occur to those skilled in 
the art subsequent to a review of the present application, and these 
modifications are intended to be included within the scope of the present 
invention.