U.S. patent application number 11/187007 was filed with the patent office on 2007-01-25 for emulsion aggregation, developer, and method of making the same.
This patent application is currently assigned to XEROX CORPORATION. Invention is credited to Raj D. Patel.
Application Number | 20070020542 11/187007 |
Document ID | / |
Family ID | 37679431 |
Filed Date | 2007-01-25 |
United States Patent
Application |
20070020542 |
Kind Code |
A1 |
Patel; Raj D. |
January 25, 2007 |
Emulsion aggregation, developer, and method of making the same
Abstract
A polyester toner includes particles of a resin, a colorant, an
optional wax, and a polyion coagulant, where the toner is prepared
by an emulsion aggregation process.
Inventors: |
Patel; Raj D.; (Oakville,
CA) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC.
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
XEROX CORPORATION
Stamford
CT
|
Family ID: |
37679431 |
Appl. No.: |
11/187007 |
Filed: |
July 22, 2005 |
Current U.S.
Class: |
430/108.2 ;
430/108.1; 430/109.4; 430/137.14 |
Current CPC
Class: |
G03G 9/08782 20130101;
G03G 9/08755 20130101; G03G 9/0804 20130101 |
Class at
Publication: |
430/108.2 ;
430/108.1; 430/109.4; 430/137.14 |
International
Class: |
G03G 9/087 20070101
G03G009/087; G03G 9/08 20070101 G03G009/08 |
Claims
1. A toner comprising particles of a resin, a colorant, an optional
wax, and a polyion coagulant, wherein said toner is prepared by an
emulsion aggregation process.
2. The toner of claim 1, wherein the resin is a polyester
resin.
3. The toner of claim 1, wherein the polyester resin is selected
from the group consisting of polyethylene-terephthalate,
polypropylene-terephthalate, polybutylene-terephthalate,
polypentylene-terephthalate, polyhexalene-terephthalate,
polyheptadene-terephthalate, polyoctalene-terephnhalate,
polyethhylene-sebacate, polypropylene sebacate,
polybutylene-sebacate, polyethylene-adipate, polypropylene-adipate,
polybutylene-adipate, polypentylene-adipate, polyhexalene-adipate,
polyheptadene-adipate, polyoctalene-adipate,
polyethylene-glutarate, polypropylene-glutarate,
polybutylene-glutarate, polypentylene-glutarate,
polyhexalene-glutarate, polyheptadene-glutarate,
polyoctalene-glutarate polyethylene-pimelate,
polypropylene-pimelate, polybutylene-pimelate,
polypentylene-pimelate, polyhexalene-pimelate,
polyheptadene-pimelate, poly(propoxylated bisphenol-fumarate),
poly(propoxylated bisphenol-succinate), poly(propoxylated
bisphenol-adipate), poly(propoxylated bisphenol-glutarate),
sulfonated forms of the preceding resins, and mixtures thereof.
4. The toner of claim 1, wherein the polyester resin is a
sulfonated polyester resin.
5. The toner of claim 1, further comprising a wax.
6. The toner of claim 1, wherein the polyion coagulant is a metal
salt or a metal oxide, the metal having a valance of at least
3.
7. The toner of claim 1, wherein the polyion coagulant is selected
from the group consisting of polyaluminum halides, polyaluminum
silicates, polyaluminum hydroxides, and polyaluminum phosphate.
8. The toner of claim 1, wherein the polyion coagulant is selected
from the group consisting of polyaluminum chloride and polyaluminum
sulfosilicate.
9. The toner of claim 1, wherein the polyion coagulant is present
in the toner particles, exclusive of any optional external
additives, and on a dry weight basis, in an amount of from less
than about 5% by weight of the toner particles.
10. A process for preparing a toner, comprising: mixing a resin
emulsion, a colorant dispersion, and an optional wax to form a
mixture; adding an organic or an inorganic acid to said mixture;
adding a polyion coagulant to said mixture; heating the mixture,
permitting aggregation and coalescence of said resin and colorant,
and optionally cooling the mixture and isolating the product,
wherein the polyion coagulant is added to said mixture at least one
of before or during said heating.
11. The process of claim 10, wherein the resin is a polyester
resin.
12. The process of claim 10, wherein the polyester resin is
selected from the group consisting of polyethylene-terephthalate,
polypropylene-terephthalate, polybutylene-terephthalate,
polypentylene-terephthalate, polyhexalene-terephthalate,
polyheptadene-terephthalate, polyoctalene-terephthalate,
polyethylene-sebacate, polypropylene sebacate,
polybutylene-sebacate, polyethylene-adipate, polypropylene-adipate,
polybutylene-adipate, polypentylene-adipate, polyhexalene-adipate,
polyheptadene-adipate, polyoctalene-adipate,
polyethylene-glutarate, polypropylene-glutarate,
polybutylene-glutarate, polypentylene-glutarate,
polyhexalene-glutarate, polyheptadene-glutarate,
polyoctalene-glutarate polyethylene-pimelate,
polypropylene-pimelate, polybutylene-pimelate,
polypentylene-pimelate, polyhexalene-pimelate,
polyheptadene-pimelate, poly(propoxylated bisphenol-fumarate),
poly(propoxylated bisphenol-succinate), poly(propoxylated
bisphenol-adipate), poly(propoxylated bisphenol-glutarate),
sulfonated forms of the preceding resins, and mixtures thereof.
13. The process of claim 10, wherein the polyester resin is a
sulfonated polyester resin.
14. The process of claim 10, further comprising mixing a wax with
said resin emulsion.
15. The process of claim 10, wherein the polyion coagulant is a
metal salt or a metal oxide, the metal having a valance of at least
3.
16. The process of claim 10, wherein the polyion coagulant is
selected from the group consisting of polyaluminum halides,
polyaluminum silicates, polyaluminum hydroxides, and polyaluminum
phosphate.
17. The process of claim 10, wherein the polyion coagulant is
selected from the group consisting of polyaluminum chloride and
polyaluminum sulfosilicate.
18. The process of claim 10, wherein the polyion coagulant is
present in an amount of from about 0.05 to about 10 percent by
weight of the amount of the resin.
19. The process of claim 10, wherein the polyion coagulant is added
to said mixture before said heating.
20. The process of claim 10, wherein the polyion coagulant is added
to said mixture during said heating.
21. The process of claim 10, wherein the polyion coagulant is added
to said mixture both before and during said heating.
22. The process of claim 10, wherein the organic or an inorganic
acid is selected from the group consisting of hydrochloric acid,
nitric acid, sulfuric acid, phosphoric acid, citric acid, and
acetic acid.
23. The process of claim 10, further comprising adding at least one
surfactant to said resin emulsion.
24. The process of claim 10, wherein at least about 75% by weight
of the polyion coagulant is incorporated into the toner particles
during particle aggregation.
25. A developer comprising: the toner of claim 1, and a
carrier.
26. An electrographic image development device, comprising the
toner of claim 1.
Description
BACKGROUND
[0001] This present disclosure relates to toners and developers
containing the toners for use in forming and developing images, and
in particular to polyester emulsion/aggregation toners formed using
polyions as coagulants. The disclosure also relates to processes
for producing and using such toners and developers.
[0002] Emulsion aggregation toners are excellent toners to use in
forming print and/or xerographic images in that the toners can be
made to have uniform sizes and in that the toners are
environmentally friendly. U.S. patents describing emulsion
aggregation toners include, for example, U.S. Pat. Nos. 5,370,963,
5,418,108, 5,290,654, 5,278,020, 5,308,734, 5,344,738, 5,403,693,
5,364,729, 5,346,797, 5,348,832, 5,405,728, 5,366,841, 5,496,676,
5,527,658, 5,585,215, 5,650,255, 5,650,256, 5,501,935, 5,723,253,
5,744,520, 5,763,133, 5,766,818, 5,747,215, 5,827,633, 5,853,944,
5,804,349, 5,840,462, and 5,869,215, the entire disclosures of
which are incorporated herein by reference.
[0003] Two main types of emulsion aggregation toners are known.
First is an emulsion aggregation process that forms acrylate based,
e.g., styrene acrylate, toner particles. See, for example, U.S.
Pat. No. 6,120,967, the entire disclosure of which is incorporated
herein by reference, as one example of such a process. Second is an
emulsion aggregation process that forms polyester, e.g., sodio
sulfonated polyester, toner particles. See, for example, U.S. Pat.
No. 5,916,725, the entire disclosure of which is incorporated
herein by reference, as one example of such a process.
[0004] Emulsion aggregation techniques typically involve the
formation of an emulsion latex of the resin particles, which
particles have a small size of from, for example, about 5 to about
500 nanometers in diameter, by heating the resin, optionally with
solvent if needed, in water, or by making a latex in water using an
emulsion polymerization. A colorant dispersion, for example of a
pigment dispersed in water, optionally also with additional resin,
is separately formed. The colorant dispersion is added to the
emulsion latex mixture, and an aggregating agent or complexing
agent is then added to form aggregated toner particles. The
aggregated toner particles are heated to enable coalescence/fusing,
thereby achieving aggregated, fused toner particles.
[0005] Addition of a coagulant during the emulsion/aggregation
process is an important step, to assist in aggregation of the
primary polymer, colorant, and the like particles. For example,
U.S. Pat. No. 6,120,967, mentioned above, describes a process where
styrene acrylate-based resins are used to form toner particles, and
in which a cationic coagulant such as poly-aluminum chloride,
aluminum sulfate, zinc sulfate, alum, and dialkyl benzenealkyl
ammonium chloride is used as the coagulant. However, different
coagulants are used in polyester-based resin emulsion/aggregation
processes. For example, U.S. Pat. No. 5,916,725, also mentioned
above, describes a process where polyester-based resins are used to
form toner particles, and in which the coagulant is a small organic
amine, such as 2-methyl-1,5-pentanediamine.
[0006] In other polyester-based resin emulsion/aggregation
processes, zinc acetate has been extensively used as a coagulant.
See, for example, U.S. Pat. Nos. 6,500,597, 6,743,559, and
6,756,176, which disclose the use of metal salts, such as aluminum
sulfate, aluminum chloride, zinc sulfate, magnesium sulfate,
magnesium chloride, potassium-aluminum sulfate, or zinc acetate, as
coagulants for producing polyester toners in emulsion/aggregation
processes.
[0007] However, a problem exists with the use of such metal salts
as zinc acetate in producing polyester toners. In particular, only
a small proportion of the zinc acetate, about 2 to 3 weight %, gets
incorporated into the toner particles. The remaining zinc acetate
is in the aqueous phase, and must be filtered and separated before
the aqueous phase can be discharged into the environment. This
separation thus adds a significant cost to the toner production and
waste disposal. The low rate of incorporation of zinc acetate into
the toner particles is believed to be primarily due to its high
solubility in water and the partial dissociation of the zinc
acetate However, coagulants such as polyions have not previously
been used in producing polyester toners, such as sulfonated
polyester toners, because the sulfonate groups on the polyester
resin particles are not sufficient to provide a controlled
aggregation or coalescence in the presence of the more active
polyion coagulants.
[0008] Accordingly, there is a need in the art for improved
emulsion aggregation toner processes, particularly for use with
polyester toner particles, that provide an efficient, controlled
process without increasing the separation and disposal costs.
SUMMARY
[0009] The present disclosure addresses these and other needs, by
providing improved coagulants and processes for making polyester
emulsion/aggregation toner compositions. The disclosure provides
more efficient coagulant materials, in that a higher amount of the
coagulant is incorporated into the aggregated toner particles,
thereby improving process efficiency, reducing process cost, and
reducing waste processing.
[0010] In embodiments, the present disclosure provides a toner
comprising particles of a resin, a colorant, an optional wax, and a
polyion coagulant, wherein said toner is prepared by an emulsion
aggregation process.
[0011] In another embodiment, the present disclosure provides a
process for preparing a toner, comprising:
[0012] mixing a resin emulsion, a colorant dispersion, and an
optional wax to form a mixture;
[0013] adding an organic or an inorganic acid to said mixture;
[0014] adding a polyion coagulant to said mixture;
[0015] heating the mixture, permitting aggregation and coalescence
of said resin and colorant, and optionally cooling the mixture and
isolating the product,
[0016] wherein the polyion coagulant is added to said mixture at
least one of before or during said heating.
[0017] In embodiments, the present disclosure also provides methods
for making developers incorporating such toners, as well as
development processes using the toners and developers.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0018] The toner of the present disclosure is comprised of toner
particles comprised of at least a latex emulsion polyester polymer
resin and a colorant dispersion. The toner particles may also
include at least a wax dispersion and other conventional optional
additives, such as colloidal silica (as a flow agent) and the like.
The toner is made using a polyion as a coagulant during the
aggregation phase of the process.
[0019] The specific latex for resin, polymer or polymers selected
for the toner of the present disclosure include polyester and/or
its derivatives, including polyester resins and branched polyester
resins, polyimide resins, branched polyimide resins,
poly(styrene-acrylate)resins, crosslinked
poly(styrene-acrylate)resins, poly(styrene-methacrylate)resins,
crosslinked poly(styrene-methacrylate)resins,
poly(styrene-butadiene)resins, crosslinked
poly(styrene-butadiene)resins, alkali sulfonated-polyester resins,
branched alkali sulfonated-polyester resins, alkali
sulfonated-polyimide resins, branched alkali sulfonated-polyimide
resins, alkali sulfonated poly(styrene-acrylate)resins, crosslinked
alkali sulfonated poly(styrene-acrylate)resins,
poly(styrene-methacrylate)resins, crosslinked alkali
sulfonated-poly(styrene-methacrylate)resins, alkali
sulfonated-poly(styrene-butadiene) resins, crosslinked alkali
sulfonated poly(styrene-butadiene)resins, and the like. In an
embodiment, for example, a particularly referred resin is a
polyester, such as a sulfonated polyester.
[0020] Illustrative examples of polymer resins selected for the
process and particles of the present disclosure include any of the
various polyesters, such as polyethylene-terephthalate,
polypropylene-terephthalate, polybutylene-terephthalate,
polypentylene-terephthalate, polyhexalene-terephthalate,
polyheptadene-terephthalate, polyoctalene-terephthalate,
polyethylene-sebacate, polypropylene sebacate,
polybutylene-sebacate, polyethylene-adipate, polypropylene-adipate,
polybutylene-adipate, polypentylene-adipate, polyhexalene-adipate,
polyheptadene-adipate, polyoctalene-adipate,
polyethylene-glutarate, polypropylene-glutarate,
polybutylene-glutarate, polypentylene-glutarate,
polyhexalene-glutarate, polyheptadene-glutarate,
polyoctalene-glutarate polyethylene-pimelate,
polypropylene-pimelate, polybutylene-pimelate,
polypentylene-pimelate, polyhexalene-pimelate,
polyheptadene-pimelate, poly(propoxylated bisphenol-fumarate),
poly(propoxylated bisphenol-succinate), poly(propoxylated
bisphenol-adipate), poly(propoxylated bisphenol-glutarate),
SPAR.TM. (Dixie Chemicals), BECKOSOL.TM. (Reichhold Chemical Inc),
ARAKOTE.TM. (Ciba-Geigy Corporation), HETRON.TM. (Ashland
Chemical), PARAPLEX.TM. (Rohm & Hass), POLYLITE.TM. (Reichhold
Chemical Inc), PLASTHALL.TM. (Rohm & Hass), CYGAL.TM. (American
Cyanamide), ARMCO.TM. (Armco Composites), ARPOL.TM. (Ashland
Chemical), CELANEX.TM. (Celanese Eng), RYNITE.TM. (DuPont),
STYPOL.TM. (Freeman Chemical Corporation) mixtures thereof and the
like. The resins can also be functionalized, such as carboxylated,
sulfonated, or the like, and particularly such as sodio sulfonated,
if desired.
[0021] In embodiments, a sulfonated polyester resin such as a sodio
sulfonated polyester resin is preferred. When used, the sulfonated
polyester resin can have any desired degree of sulfonation. For
example, the sulfonation degree can be from about 0.1 to about 20
percent, such as from about 0.3 to about 6 percent.
[0022] The latex polymer may be present in an amount of from about
70 to about 95% by weight of the toner particles (i.e., toner
particles exclusive of external additives) on a solids basis, such
as from about 75 to about 85% by weight of the toner. However,
amounts outside of these ranges can be used, in embodiments,
depending upon the type and amounts of other materials present.
[0023] The monomers used in making the selected polymer are not
limited, and the monomers utilized may include any one or more of,
for example, ethylene, propylene, and the like. Known chain
transfer agents, for example dodecanethiol or carbon tetrabromide,
can be utilized to control the molecular weight properties of the
polymer. Any suitable method for forming the latex polymer from the
monomers may be used without restriction.
[0024] Various suitable colorants can be employed in toners of the
present disclosure, including suitable colored pigments, dyes, and
mixtures thereof, including carbon black, such as REGAL 330 carbon
black, acetylene black, lamp black, aniline black, Chrome Yellow,
Zinc Yellow, SICOFAST Yellow, SUNBRITE Yellow, LUNA Yellow,
NOVAPERM Yellow, Chrome Orange, BAYPLAST Orange, Cadmium Red,
LITHOL Scarlet, HOSTAPERM Red, FANAL PINK, HOSTAPERM Pink, LUPRETON
Pink, LITHOL Red, RHODAMINE Lake B, Brilliant Carmine, HELIOGEN
Blue, HOSTAPERM Blue, NEOPAN Blue, PV Fast Blue, CINQUASSI Green,
HOSTAPERM Green, titanium dioxide, cobalt, nickel, iron powder,
SICOPUR 4068 FF, and iron oxides such as MAPICO Black (Columbia)
NP608 and NP604 (Northern Pigment), BAYFERROX 8610 (Bayer), M08699
(Mobay), TMB-100 (Magnox), mixtures thereof and the like.
[0025] The colorant, such as carbon black, cyan, magenta and/or
yellow colorant, is incorporated in an amount sufficient to impart
the desired color to the toner. In general, pigment or dye is
employed in an amount ranging from about 2% to about 35% by weight
of the toner particles on a solids basis, such as from about 5% to
about 25% by weight or from about 5 to about 15% by weight.
However, amounts outside these ranges can also be used, in
embodiments.
[0026] Of course, as the colorants for each color are different,
the amount of colorant present in each type of color toner
typically is different. For example, in some embodiments of the
present disclosure, a cyan toner may include about 3 to about 11%
by weight of colorant (such as Pigment Blue 15:3 from SUN), a
magenta toner may include about 3 to about 15% by weight of
colorant (such as Pigment Red 122, Pigment Red 185, Pigment Red
238, and/or mixtures thereof), a yellow toner may include about 3
to about 10% by weight of colorant (such as Pigment Yellow 74), and
a black toner may include about 3 to about 10% by weight of
colorant (such as carbon black).
[0027] In addition to the latex polymer binder and the colorant,
the toners of the present disclosure may also optionally contain a
wax, typically provided in a wax dispersion, which wax dispersion
can be of a single type of wax or a mixture of two or more
preferably different waxes. A single wax can be added to toner
formulations, for example, to improve particular toner properties,
such as toner particle shape, presence and amount of wax on the
toner particle surface, charging and/or fusing characteristics,
gloss, stripping, offset properties, and the like. Alternatively, a
combination of waxes can be added to provide multiple properties to
the toner composition.
[0028] When a wax dispersion is used, the wax dispersion can
include any of the various waxes conventionally used in emulsion
aggregation toner compositions. Suitable examples of waxes include,
but are not limited to, polyethylene, polypropylene,
polyethylene/amide, polyethylenetetrafluoroethylene, and
polyethylenetrtraflouorethylene/amide. Other examples include, for
example, polyolefin waxes, such as polyethylene waxes, including
linear polyethylene waxes and branched polyethylene waxes, and
polypropylene waxes, including linear polypropylene waxes and
branched polypropylene waxes; paraffin waxes; Fischer-Tropsch
waxes; amine waxes; silicone waxes; mercapto waxes; polyester
waxes; urethane waxes; modified polyolefin waxes (e.g., a
carboxylic acid-terminated polyethylene wax or a carboxylic
acid-terminated polypropylene wax); amide waxes, such as aliphatic
polar amide functionalized waxes; aliphatic waxes consisting of
esters of hydroxylated unsaturated fatty acids; high acid waxes,
such as high acid montan waxes; microcrystalline waxes, such as
waxes derived from distillation of crude oil; and the like. By
"high acid waxes" it is meant a wax material that has a high acid
content. The waxes can be crystalline or non-crystalline, as
desired, although crystalline waxes are preferred, in embodiments.
By "crystalline polymeric waxes" it is meant that a wax material
contains an ordered array of polymer chains within a polymer matrix
that can be characterized by a crystalline melting point transition
temperature, Tm. The crystalline melting temperature is the melting
temperature of the crystalline domains of a polymer sample. This is
in contrast to the glass transition temperature, Tg, which
characterizes the temperature at which polymer chains begin to flow
for the amorphous regions within a polymer.
[0029] To incorporate the wax into the toner, it is preferable for
the wax to be in the form of one or more aqueous emulsions or
dispersions of solid wax in water, where the solid wax particle
size is usually in the range of from about 100 to about 500 nm.
[0030] The toners may contain the wax in any amount of from, for
example, about 3 to about 15% by weight of the toner, on a dry
basis. For example, the toners can contain from about 5 to about
11% by weight of the wax.
[0031] The toners of the present disclosure may also contain a
coagulant. A variety of coagulants are known in the art, as
described above. However, the disclosure relates to the specific
selection of polyions, or multivalent ions, as coagulants in
forming the toner compositions. As used herein, "polyion coagulant"
refers to a coagulant that is a salt or oxide, preferably a metal
salt or metal oxide, formed from a metal species having a valence
of at least 3, and preferably at least 4 or 5. Suitable coagulants
thus include, for example, coagulants based on aluminum such as
polyaluminum halides such as polyaluminum fluoride and polyaluminum
chloride (PAC), polyaluminum silicates such as polyaluminum
sulfosilicate (PASS), polyaluminum hydroxide, polyaluminum
phosphate, and the like. Other suitable coagulants include, but are
not limited to, tetraalkyl titinates, dialkyltin oxide,
tetraalkyltin oxide hydroxide, dialkyltin oxide hydroxide, aluminum
alkoxides, alkylzinc, dialkyl zinc, zinc oxides, stannous oxide,
dibutyltin oxide, dibutyltin oxide hydroxide, tetraalkyl tin, and
the like. Such polyion coagulants may have any desired number of
polyion atoms present. For example, preferred polyaluminum
compounds in embodiments have from about 2 to about 13, such as
from about 3 to about 8, aluminum ions present in the compound
[0032] Such polyion coagulants are preferred, in embodiments,
because they are more highly incorporated into the toner particles
during particle aggregation, and thus less of the coagulant remains
in solution requiring extra subsequent waste processing. For
example, in embodiments, at least about 50%, such as at least about
75% or at least about 80% by weight of the polyion coagulant is
incorporated into the toner particles during particle aggregation,
meaning that less than about 50%, such as less than about 25% or
less than about 20%, respectively, of the coagulant remains in
solution after completion of particle aggregation. In one
embodiment, as high as about 90% or more of the polyion coagulant
is incorporated into the toner particles during particle
aggregation, meaning that less than about 10% of the coagulant
remains in solution after completion of particle aggregation.
[0033] The coagulant is present in the toner particles, exclusive
of external additives and on a dry weight basis, in amounts of from
0 to about 5% by weight of the toner particles, such as from about
greater than 0 to about 3% by weight of the toner particles.
[0034] The toner may also include additional known positive or
negative charge additives in effective suitable amounts of, for
example, from about 0.1 to about 5 weight percent of the toner,
such as quaternary ammonium compounds inclusive of alkyl pyridinium
halides, bisulfates, organic sulfate and sulfonate compositions
such as disclosed in U.S. Pat. No. 4,338,390, cetyl pyridinium
tetrafluoroborates, distearyl dimethyl ammonium methyl sulfate,
aluminum salts or complexes, and the like.
[0035] Also, in preparing the toner by the emulsion aggregation
procedure, one or more surfactants may be used in the process.
Suitable surfactants include anionic, cationic and nonionic
surfactants. In embodiments, the use of anionic and nonionic
surfactants are preferred to help stabilize the aggregation process
in the presence of the polyion coagulant, which otherwise could
lead to aggregation instability.
[0036] Anionic surfactants include sodium dodecylsulfate (SDS),
sodium dodecyl benzene sulfonate, sodium dodecylnaphthalene
sulfate, dialkyl benzenealkyl, sulfates and sulfonates, abitic
acid, and the NEOGEN brand of anionic surfactants. An example of a
suitable anionic surfactant is NEOGEN RK available from Daiichi
Kogyo Seiyaku Co. Ltd., or TAYCA POWER BN2060 from Tayca
Corporation (Japan), which consists primarily of branched sodium
dodecyl benzene sulphonate.
[0037] Examples of cationic surfactants include dialkyl benzene
alkyl ammonium chloride, lauryl trimethyl ammonium chloride,
alkylbenzyl methyl ammonium chloride, alkyl benzyl dimethyl
ammonium bromide, benzalkonium chloride, cetyl pyridinium bromide,
C.sub.12, C.sub.15, C.sub.17 trimethyl ammonium bromides, halide
salts of quatemized polyoxyethylalkylamines, dodecyl benzyl
triethyl ammonium chloride, MIRAPOL and ALKAQUAT available from
Alkaril Chemical Company, SANISOL (benzalkonium chloride),
available from Kao Chemicals, and the like. An example of a
suitable cationic surfactant is SANISOL B-50 available from Kao
Corp., which consists primarily of benzyl dimethyl alkonium
chloride.
[0038] Examples of nonionic surfactants include polyvinyl alcohol,
polyacrylic acid, methalose, methyl cellulose, ethyl cellulose,
propyl cellulose, hydroxy ethyl cellulose, carboxy methyl
cellulose, polyoxyethylene cetyl ether, polyoxyethylene lauryl
ether, polyoxyethylene octyl ether, polyoxyethylene octylphenyl
ether, polyoxyethylene oleyl ether, polyoxyethylene sorbitan
monolaurate, polyoxyethylene stearyl ether, polyoxyethylene
nonylphenyl ether, dialkylphenoxy poly(ethyleneoxy) ethanol,
available from Rhone-Poulenc Inc. as IGEPAL CA-210, IGEPAL CA-520,
IGEPAL CA-720, IGEPAL CO-890, IGEPAL CO-720, IGEPAL CO-290, IGEPAL
CA-210, ANTAROX 890 and ANTAROX 897. An example of a suitable
nonionic surfactant is ANTAROX 897 available from Rhone-Poulenc
Inc., which consists primarily of alkyl phenol ethoxylate.
[0039] Any suitable emulsion aggregation procedure may be used in
forming the emulsion aggregation toner particles without
restriction. These procedures typically include the basic process
steps of at least aggregating an emulsion containing binder, one or
more colorants, one or more surfactants, a polyion coagulant,
optionally a wax emulsion, and one or more additional optional
additives to form aggregates, subsequently coalescing or fusing the
aggregates, and then recovering, optionally washing and optionally
drying the obtained emulsion aggregation toner particles.
[0040] In an embodiment, the process comprises mixing a
polyester-based resin emulsion with a colorant in the presence of a
polyion coagulant, an acid and one or more surfactants, and
thereafter heating the mixture resulting in metal ions generated
from the reaction between the polyion coagulant and the acid to
effect aggregation/coalescence of the emulsion particles and
colorant to form coalesced toner particles of resin and
colorant.
[0041] An exemplary process for producing the toner particles
comprises the following steps.
[0042] First, an emulsion latex is provided (or generated),
comprised of polyester-based resin particles, such as sodio
sulfonated polyester resin particles. The latex is preferably
heated in water to a temperature of, for example, from about
65.degree. C. to about 90.degree. C.
[0043] Second, a colorant dispersion is added, preferably with
shearing, to the resin latex. The colorant dispersion can comprise,
for example, from about 20 to about 50 percent of a predispersed
colorant in water. An organic or an inorganic acid, and one or more
surfactants, are also added to the mixture of the resin and
colorant dispersions. If desired, the mixture can be heated to a
desired temperature in preparation for a subsequent aggregation
reaction, such as a temperature of from about 45.degree. C. to
about 65.degree. C. Other optional additives and/or dispersions can
also be included, such as a wax dispersion, a second or additional
resin dispersion, and the like. The shearing can be conducted, for
example, by homogenizing at from about 1,000 revolutions per minute
to about 10,000 revolutions per minute, at a temperature of from
about 25.degree. C. to about 35.degree. C., and for a duration of
from about 1 minute to about 120 minutes. As desired, the mixture
can also comprise other components, such as an optional wax, and
the like.
[0044] Third, a polyion coagulant, as described above, is added to
the mixture. The polyion coagulant, which is preferably water
insoluble, releases metal ions and permits aggregation and
coalescence of the resin and colorant particles, resulting in
formation of toner particles of from about 2 to about 25 microns,
such as from about 3 to about 15 microns, in volume average
diameter. The geometric size distribution of the resultant
particles can, in embodiments, be less than about 1.40 or less than
about 1.25, such as from about 1.15 to about 1.40.
[0045] Preferably, in embodiments, the polyion coagulant is added
to the mixture before the mixture is heated to cause aggregation
and coalescence of the resin and colorant dispersions. For example,
the polyion coagulant can be added to the mixture at any time
before heating, such as during mixing of the individual components
to form a mixture or after the individual components are mixed
together, but prior to heating. Alternatively, the polyion
coagulant can be added during the heating process, such as
concurrent with or after starting of the heating process, although
it is preferred that the polyion coagulant is added before the
final aggregation/coalescence temperature is reached. If desired,
the polyion coagulant can be added to the mixture both before and
during the heating step. Also if desired, the polyion coagulant or
an additional amount of the same or different polyion coagulant can
alternatively be added during or after the heating step.
[0046] Fourth, one or more optional steps can be conducted
following aggregation of the toner particles. For example, the
mixture can be cooled, such as to near room temperature, and the
toner product isolated from the reaction medium.
[0047] In the above process, the aggregation and coalescence
temperature can be at any suitable temperature, such as from about
45.degree. C. to about 80.degree. C., or from about 50.degree. C.
to about 75.degree. C.
[0048] The organic or an inorganic acid suitable for use in the
process is not particularly limited. Examples of such acids
include, but are not limited to, inorganic acids such as
hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid,
and organic acids such as citric acid and acetic acid.
[0049] The polyion coagulant can be added to the emulsion mixture
in any suitable and desirable amount. However, in embodiments, the
polyion coagulant is added to the emulsion mixture in an amount of
from about 0.05 to about 10 percent by weight, such as from about
0.1 or from about 0.2 to about 1 or to about 5 percent, by weight
of the amount of the resin. Amounts outside these ranges can also
be used.
[0050] Toner particles formed in the foregoing processes, and
modification thereof, can be isolated by any suitable means known
in the art. For example, isolation can be conducted by filtration,
wet sieving, classification, washing, drying, or the like.
[0051] The toner particles of the present disclosure can be made to
have the following physical properties when no external additives
are present on the toner particles.
[0052] The toner particles can have a surface area, as measured by
the well known BET method, of about 1.3 to about 6.5 m.sup.2/g. For
example, for cyan, yellow and black toner particles, the BET
surface area is less than 2 m.sup.2/g, such as from about 1.4 to
about 1.8 m.sup.2/g, and for magenta toner, from about 1.4 to about
6.3 m.sup.2/g.
[0053] It is also desirable to control the toner particle size and
limit the amount of both fine and coarse toner particles in the
toner. In an embodiment, the toner particles have a very narrow
particle size distribution with a lower number ratio geometric
standard deviation (GSD) of approximately 1.15 to approximately
1.30, or approximately less than 1.25. The toner particles of the
present disclosure also can have a size such that the upper
geometric standard deviation (GSD) by volume is in the range of
from about 1.15 to about 1.30, such as from about 1.18 to about
1.22, or less than 1.25. These GSD values for the toner particles
of the present disclosure indicate that the toner particles are
made to have a very narrow particle size distribution.
[0054] Shape factor is also an important control process parameter
associated with the toner being able to achieve optimal machine
performance. The toner particles can have a shape factor of about
105 to about 170, such as about 110 to about 160, SF1*a. Scanning
electron microscopy (SEM) is used to determine the shape factor
analysis of the toners by SEM and image analysis (IA) is tested.
The average particle shapes are quantified by employing the
following shape factor (SF1*a) formula: SF1*a=100 .pi.d.sup.2/(4A),
where A is the area of the particle and d is its major axis. A
perfectly circular or spherical particle has a shape factor of
exactly 100. The shape factor SF1*a increases as the shape becomes
more irregular or elongated in shape with a higher surface area. In
addition to measuring shape factor SF, another metric to measure
particle circularity is being used on a regular bases. This is a
faster method to quantify the particle shape. The instrument used
is an FPIA-2100 manufactured by Sysmex. For a completely circular
sphere the circularity would be 1.000. The toner particles can have
circularity of about 0.920 to 0.990 and, such as from about 0.940
to about 0.975.
[0055] In addition to the foregoing, the toner particles of the
present disclosure also have the following rheological and flow
properties. First, the toner particles can have the following
molecular weight values, each as determined by gel permeation
chromatography (GPC) as known in the art. The binder of the toner
particles can have a weight average molecular weight, Mw of from
about 15,000 daltons to about 90,000 daltons.
[0056] Overall, the toner particles in embodiments have a weight
average molecular weight (Mw) in the range of about 17,000 to about
60,000 daltons, a number average molecular weight (Mn) of about
9,000 to about 18,000 daltons, and a MWD of about 2.1 to about 10.
MWD is a ratio of the Mw to Mn of the toner particles, and is a
measure of the polydispersity, or width, of the polymer. For cyan
and yellow toners, the toner particles in embodiments can exhibit a
weight average molecular weight (Mw) of about 22,000 to about
38,000 daltons, a number average molecular weight (Mn) of about
9,000 to about 13,000 daltons, and a MWD of about 2.2 to about 10.
For black and magenta, the toner particles in embodiments can
exhibit a weight average molecular weight (Mw) of about 22,000 to
about 38,000 daltons, a number average molecular weight (Mn) of
about 9,000 to about 13,000 daltons, and a MWD of about 2.2 to
about 10.
[0057] Further, the toners if desired can have a specified
relationship between the molecular weight of the latex binder and
the molecular weight of the toner particles obtained following the
emulsion aggregation procedure. As understood in the art, the
binder undergoes crosslinking during processing, and the extent of
crosslinking can be controlled during the process. The relationship
can best be seen with respect to the molecular peak values for the
binder. Molecular peak is the value that represents the highest
peak of the weight average molecular weight. In the present
disclosure, the binder can have a molecular peak (Mp) in the range
of from about 22,000 to about 30,000 daltons, such as from about
22,500 to about 29,000 daltons. The toner particles prepared from
such binder also exhibit a high molecular peak, for example of
about 23,000 to about 32,000, such as about 23,500 to about 31,500
daltons, indicating that the molecular peak is driven by the
properties of the binder rather than another component such as the
colorant.
[0058] Another property of the toners of the present disclosure is
the cohesivity of the particles prior to inclusion of any external
additives. The greater the cohesivity, the less the toner particles
are able to flow. The cohesivity of the toner particles, prior to
inclusion of any external additives, may be from, for example,
about 55 to about 98% for all colors of the toner. Cohesivity was
measured by placing a known mass of toner, two grams, on top of a
set of three screens, for example with screen meshes of 53 microns,
45 microns, and 38 microns in order from top to bottom, and
vibrating the screens and toner for a fixed time at a fixed
vibration amplitude, for example for 90 seconds at a 1 millimeter
vibration amplitude. A device to perform this measurement is a
Hosokawa Powders Tester, available from Micron Powders Systems. The
toner cohesion value is related to the amount of toner remaining on
each of the screens at the end of the time, and is calculated by
the formula: % cohesion=50*A+30*B+10*C, where A, B and C are
respectively the weight of the toner remaining on the 53 microns,
45 microns, and 38 microns screens, respectively. A cohesion value
of 100% corresponds to all of the toner remaining on the top screen
at the end of the vibration step and a cohesion value of zero
corresponds to all of the toner passing through all three screens,
that is, no toner remaining on any of the three screens at the end
of the vibration step. The higher the cohesion value, the lesser
the flowability of the toner.
[0059] Finally, the toner particles in embodiments have a bulk
density of from about 0.22 to about 0.34 g/cc and a compressibility
of from about 33 to about 51.
[0060] The toner particles can be blended with external additives
following formation. Any suitable surface additives may be used in
embodiments. Most suitable are one or more of SiO.sub.2, metal
oxides such as, for example, TiO.sub.2 and aluminum oxide, and a
lubricating agent such as, for example, a metal salt of a fatty
acid (e.g., zinc stearate (ZnSt), calcium stearate) or long chain
alcohols such as UNILIN 700, as external surface additives. In
general, silica is applied to the toner surface for toner flow,
tribo enhancement, admix control, improved development and transfer
stability and higher toner blocking temperature. TiO.sub.2 is
applied for improved relative humidity (RH) stability, tribo
control and improved development and transfer stability. Zinc
stearate is optionally also used as an external additive for the
toners of the disclosure, the zinc stearate providing lubricating
properties. Zinc stearate provides developer conductivity and tribo
enhancement, both due to its lubricating nature. In addition, zinc
stearate enables higher toner charge and charge stability by
increasing the number of contacts between toner and carrier
particles. Calcium stearate and magnesium stearate provide similar
functions. In embodiments, a commercially available zinc stearate
known as Zinc Stearate L, obtained from Ferro Corporation, can be
used. The external surface additives can be used with or without a
coating.
[0061] A particular advantage of embodiments is that the above
external additives, or others, can be added to the aggregated toner
particles and effectively form a thin shell on the toner particles.
Because larger amounts of the coagulant remains as part of the
toner particles, the coagulant species provide sites for increased
attachment of the external additives to the aggregated particles.
This increased attachment can result in formation of a shell around
the toner particles, not possible with previously known coagulant
materials.
[0062] In embodiments, the toners contain from, for example, about
0.1 to about 5 weight percent titania, about 0.1 to about 8 weight
percent silica and about 0.1 to about 4 weight percent zinc
stearate.
[0063] The toner particles of the disclosure can optionally be
formulated into a developer composition by mixing the toner
particles with carrier particles. Illustrative examples of carrier
particles that can be selected for mixing with the toner
composition prepared in accordance with the present disclosure
include those particles that are capable of triboelectrically
obtaining a charge of opposite polarity to that of the toner
particles. Accordingly, in one embodiment the carrier particles may
be selected so as to be of a negative polarity in order that the
toner particles that are positively charged will adhere to and
surround the carrier particles. Illustrative examples of such
carrier particles include iron, iron alloys, steel, nickel, iron
ferrites, including ferrites that incorporate strontium, magnesium,
manganese, copper, zinc, and the like, magnetites, and the like.
Additionally, there can be selected as carrier particles nickel
berry carriers as disclosed in U.S. Pat. No. 3,847,604, the entire
disclosure of which is totally incorporated herein by reference,
comprised of nodular carrier beads of nickel, characterized by
surfaces of reoccurring recesses and protrusions thereby providing
particles with a relatively large external area. Other carriers are
disclosed in U.S. Pat. Nos. 4,937,166 and 4,935,326, the
disclosures of which are totally incorporated herein by
reference.
[0064] The selected carrier particles can be used with or without a
coating, the coating generally being comprised of acrylic and
methacrylic polymers, such as methyl methacrylate, acrylic and
methacrylic copolymers with fluoropolymers or with monoalkyl or
dialkylamines, fluoropolymers, polyolefins, polystyrenes, such as
polyvinylidene fluoride resins, terpolymers of styrene, methyl
methacrylate, and a silane, such as triethoxy silane,
tetrafluoroethylenes, other known coatings and the like.
[0065] The carrier particles can be mixed with the toner particles
in various suitable combinations. The toner concentration is
usually about 2% to about 10% by weight of toner and about 90% to
about 98% by weight of carrier. However, one skilled in the art
will recognize that different toner and carrier percentages may be
used to achieve a developer composition with desired
characteristics.
[0066] Toners of the present disclosure can be used in known
electrostatographic imaging methods. Thus for example, the toners
or developers of the disclosure can be charged, e.g.,
triboelectrically, and applied to an oppositely charged latent
image on an imaging member such as a photoreceptor or ionographic
receiver. The resultant toner image can then be transferred, either
directly or via an intermediate transport member, to a support such
as paper or a transparency sheet. The toner image can then be fused
to the support by application of heat and/or pressure, for example
with a heated fuser roll.
[0067] It is envisioned that the toners of the present disclosure
may be used in any suitable procedure for forming an image with a
toner, including in applications other than xerographic
applications.
[0068] Specific embodiments of the disclosure will now be described
in detail. These Examples are intended to be illustrative, and the
disclosure is not limited to the materials, conditions, or process
parameters set forth in these embodiments. All parts and
percentages are by weight unless otherwise indicated.
EXAMPLES
Resin Emulsion A:
[0069] A sulfonated polyester resin emulsion is prepared as
follows.
[0070] A sulfonated polyester resin containing 3.75 moles of
sulfonation is prepared by a polycondensation reaction. The resin
is ground into powder by milling. To 4400 mL of water in a reactor,
is added 12.0 g NEOGEN RK.RTM. (anionic surfactant) and 8.2 g CA
897 (nonionic surfactant) and stirred at a speed of 500 rpm with a
pitch blade turbine until dissolved. To this mixture is added 616 g
of polyester resin powder, and the temperature of the reactor is
raised to 85.degree. C. and allowed to stir for a period of 4 hours
in order to dissipate the resin into an emulsion containing about
36 nm sulfonated polyester resin particles suspended in water. The
reactor is then cooled down to room temperature, and the emulsion
discharged. The emulsion contains 14.0 weight percent resin and
86.0 weight percent water.
Resin Emulsion B:
[0071] A sulfonated polyester resin emulsion is prepared as
follows.
[0072] A sulfonated polyester resin containing 3.75 moles of
sulfonation is prepared by a polycondensation reaction. The resin
is ground into powder by milling. To 2000 mL of water in a reactor,
is added 5.45 g NEOGEN RK.RTM. (anionic surfactant) and 1.9 g CA
897 (nonionic surfactant) and stirred at a speed of 500 rpm with a
pitch blade turbine until dissolved. To this mixture is added 280 g
of polyester resin powder, and the temperature of the reactor is
raised to 80.degree. C. and allowed to stir for a period of 4 hours
in order to dissipate the resin into an emulsion containing about
45 nm sulfonated polyester resin particles suspended in water. The
reactor is then cooled down to room temperature, and the emulsion
discharged. The emulsion contains 14.0 weight percent resin and
86.0 weight percent water.
Pigment Dispersion:
[0073] A pigment dispersion of an aqueous dispersion of Blue 15.3
pigment, obtained from Sun Chemicals, is used. The pigment
dispersion contains an anionic surfactant. The content of the
pigment dispersion is 26.5 percent pigment, 2 percent surfactant,
and 71.5 percent water.
Example 1
[0074] A toner is prepared as follows. To 350 g deionized water is
added 687 g of the polyester resin A and 14.3 g of the colorant
dispersion in a 2 L glass reactor. To the mixture is added 3.0 g
PAC (polyaluminum chloride) and 30 g of 0.1M nitric acid while
being polytroned with an IKA homogenizer at a speed of 4000 rpm.
The mixture is stirred and heated to a temperature of 62.degree. C.
The particle growth is monitored during the heat-up step. The
particle size obtained is 4.3 microns with a GSD of 1.19.
[0075] The reactor temperature is next raised to 64.degree. C. and
allowed to stir for 4 hours. The result is particles having a
particle size of 7.4 microns and a GSD of 1.17. The particles have
a circular shape having a circularity of 0.978. The particles are
washed 4 times with deionized water and dried on a freeze
drier.
[0076] The thus formed toner composition is tested for its charging
properties.
Comparative Example 1
[0077] A toner composition is made as in Example 1, except that the
coagulant zinc acetate is used instead of polyaluminum chloride.
The formed toner particles are similar in size and properties to
those of Example 1, and have similar charging properties.
Example 2
[0078] A toner composition is made as in Example 1, except that the
coagulant used is 4.0 g polyaluminum chloride, and the aggregation
temperature is 62.degree. C.
Example 3
[0079] A toner composition is made as in Example 1, except that the
resin latex used is latex emulsion B. The resultant toner particles
have a particle size of 5.0 microns and a GSD of 1.19.
[0080] It will be appreciated that various of the above-disclosed
and other features and functions, or alternatives thereof, may be
desirably combined into many other different systems or
applications. Also that various presently unforeseen or
unanticipated alternatives, modifications, variations or
improvements therein may be subsequently made by those skilled in
the art which are also intended to be encompassed by the following
claims.
* * * * *