U.S. patent application number 10/161910 was filed with the patent office on 2003-12-04 for encapsulated pigment for ink-jet ink formulations nad methods of producing same.
Invention is credited to Akers, Charles Edward JR., Sun, Jing X..
Application Number | 20030225185 10/161910 |
Document ID | / |
Family ID | 29583509 |
Filed Date | 2003-12-04 |
United States Patent
Application |
20030225185 |
Kind Code |
A1 |
Akers, Charles Edward JR. ;
et al. |
December 4, 2003 |
Encapsulated pigment for ink-jet ink formulations nad methods of
producing same
Abstract
Encapsulated pigment for use in ink-jet ink formulations,
improved ink-jet ink formulations using the encapsulated pigment,
and methods for producing same. The pigment particles are
pretreated with a polymer that is soluble in organic solvents, but
substantially insoluble in water. The pigment particles are added
to a solution of polymer/organic solvent, mixed to form a paste
then collected after driving off the solvent. The encapsulated
pigment can be used to prepare an ink-jet ink formulation by
grinding it in a water carrier with a conventional polymer
dispersant.
Inventors: |
Akers, Charles Edward JR.;
(Lexington, KY) ; Sun, Jing X.; (Lexington,
KY) |
Correspondence
Address: |
LEXMARK INTERNATIONAL, INC.
INTELLECTUAL PROPERTY LAW DEPARTMENT
740 WEST NEW CIRCLE ROAD
BLDG. 082-1
LEXINGTON
KY
40550-0999
US
|
Family ID: |
29583509 |
Appl. No.: |
10/161910 |
Filed: |
June 4, 2002 |
Current U.S.
Class: |
523/160 ;
523/161 |
Current CPC
Class: |
C09B 67/0008 20130101;
C01P 2004/62 20130101; C09C 1/56 20130101; C09D 11/322 20130101;
C09D 11/30 20130101; C01P 2004/64 20130101; C01P 2006/80 20130101;
C09C 3/10 20130101; B82Y 30/00 20130101 |
Class at
Publication: |
523/160 ;
523/161 |
International
Class: |
C03C 017/00; C09D
005/00 |
Claims
What is claimed is:
1. Encapsulated pigment particles for use in ink-jet ink
formulations, which pigment particles are at least partially
encapsulated with one or more polymer materials, which polymer
materials are at least partially soluble in an organic solvent, but
substantially insoluble in water, and which polymer materials have
at least one polar segment and at least one non-polar segment.
2. The encapsulated pigment particles of claim 1 wherein the
monomer contributing to the non-polar segment of the polymer
material is selected from the group consisting of
polydimethylsiloxane, propoxylated allyl methacrylate, nonylphenyl
polypropylene glycol acrylate, stearyl methacrylate, ethylene
glycol, ether methacrylate and alkyl(meth) acrylates.
3. The encapsulated pigment particles of claim 1 wherein the
monomer contributing to the polar segment of the polymer material
is selected from the group consisting of hydroxyethyl methacrylate,
hydroxy terminated monomer, combined with or without acid-amine
monomers.
4. The encapsulated pigment particles of claim 1 wherein the
average pigment particle is substantially totally encapsulated with
said polymer material.
5. The encapsulated pigment particles of claim 2 wherein the
monomer contributing to the polar segment of the polymer material
is selected from the group consisting of hydroxyethyl methacrylate,
a hydroxy terminated monomer, combined with or without acid-amine
monomers, and the encapsulated pigment particles are substantially
totally encapsulated with said polymer material.
6. The encapsulated pigment particles of claim 1 wherein the
monomer contributing to the non-polar segment is selected from the
alkyl(meth) acrylates, nonylphenyl polypropylene glycol, and
2-(2'hydroxy-5'-methacry- loxyethyl-phenyl)-2H-benzotriazole.
7. The encapsulated pigment particles of claim 6 wherein the
monomer contributing to the polar segment is hydroethyl
methacrylate.
8. A method for producing encapsulated pigment particles suitable
for ink-jet ink formulations, which method comprising: a)
dissolving an organic soluble polymer material in an organic
solvent, which polymer material is comprised of at least one polar
segment and at least one non-polar segment; b) introducing an
effective amount of pigment particles into the resulting
polymer/solvent solution, thereby forming a slurry; and c) mixing
the slurry at effective conditions to form a paste containing at
least partially encapsulated pigment particles.
9. The method of claim 8 wherein the monomer contributing to the
non-polar segment of said polymer material is selected from the
group consisting of polydimethylsiloxane, propoxylated allyl
methacrylate, nonylphenyl ppg acrylate, stearyl methacrylate,
ethylene glycol, ether methacrylate and alkyl(meth) acrylates.
10. The method of claim 8 wherein the monomer contributing to the
polar segment of said polymer material is selected from the group
consisting of hydroxyethyl methacrylate, hydroxy terminated
monomer, combined with or without acid-amine monomers.
11. The method of claim 8 wherein the organic solvent is selected
from the group consisting of acetone, isopropyl alcohol, ethylene
glycol, pyrrolidane and propylene glycol.
12. The method of claim 8 wherein the paste of step c) is washed
with water and dried.
13. The method of claim 8 wherein the organic solvent is also used
as a humectant in a final ink formulation and thus is not driven
off.
14. The method of claim 8 wherein the monomer contributing to the
non-polar segment is selected from the alkyl(meth)acrylates,
nonylphenyl polypropylene glycol, and
2-(2'hydroxy-5'-methacryloxyethyl-phenyl)-2H-be- nzotriazole.
15. The method of claim 14 wherein the monomer contributing to the
polar segment is hydroethyl methacrylate.
16. The method of claim 14 wherein the monomer contributing to the
non-polar segment is an alkyl(meth )acrylate.
17. The method of claim 16 wherein the alkyl(meth) acrylate is
selected from n-butyl acrylate and methyl methacrylate.
18. The method of claim 14 wherein: i) the monomer contributing to
the polar segment of said polymer material is selected from the
group consisting of hydroxyethyl methacrylate, a hydroxy terminated
monomer, combined with or without acid-amine monomers; and ii) the
organic solvent is selected from the group consisting of acetone,
isopropyl alcohol, ethylene glycol, pyrrolidane and propylene
glycol.
19. The method of claim 18 wherein the organic solvent is also used
as a humectant in a final ink formulation and thus is not driven
off.
20. The method of claim 18 wherein the paste of step c) is washed
with water and dried.
21. An ink-jet ink formulation comprising: a) an aqueous carrier;
b) an effective amount of pigment particles that are at least
partially encapsulated with a first polymer material, which first
polymer material is at least partially soluble in organic solvent
but which is substantially insoluble in water and which first
polymer material contains at least one polar segment and at least
one non-polar segment; and c) a second polymer material dispersant
that is at least partially soluble or miscible in water, and which
is comprised of a polar segment and a non-polar segment.
22. The ink formulation of claim 21 wherein the monomer
contributing to the non-polar segment of said first polymer
material is selected from the group consisting of
polydimethylsiloxane, propoxylated allyl methacrylate, nonylphenyl
ppg acrylate, stearyl methacrylate, ethylene glycol, ether
methacrylate and alkyl(meth) acrylates.
23. The ink formulation of claim 21 wherein the monomer
contributing to the polar segment of said first polymer material is
selected from the group consisting of hydroxyethyl methacrylate,
hydroxy terminated monomer, combined with or without acid-amine
monomers.
24. The ink formulation of claim 21 wherein the monomer
contributing to the non-polar segment is selected from the
alkyl(meth)acrylates, nonylphenyl polypropylene glycol, and
2-(2'hydroxy-5'-methacryloxyethyl-p- henyl)-2H-benzotriazole.
25. The ink formulation of claim 21 wherein the monomer
contributing to the polar segment is hydroethyl methacrylate.
26. The ink formulation of claim 24 wherein the monomer
contributing to the non-polar segment is an alkyl(meth )
acrylate.
27. The ink formulation of claim 26 wherein the alkyl(meth)
acrylate is selected from n-butyl acrylate and methyl
methacrylate.
28. The ink formulation of claim 21 wherein there is also present
at least one additive selected from the group consisting of
co-solvents, humectants, biocides, penetrants, surfactants,
anti-coagulation agents, anti-curling agents, buffers, chelating
agents, and anti-bleed agents.
29. A method for preparing an ink-jet ink formulation comprising:
a) dissolving an organic soluble first polymer material in an
organic solvent, which first polymer material contains at least one
polar segment and at least one non-polar segment; b) introducing an
effective amount of pigment particles into the resulting
polymer/solvent solution thereby forming a slurry of pigment
particles in the polymer/solvent solution; c) mixing the slurry at
effective conditions to form a paste; d) driving off at least a
portion of the solvent, thereby resulting in pigment particles that
are at least partially encapsulated with the first polymer
material; and e) grinding the encapsulated pigment particles in a
water carrier with a water soluble or water miscible second polymer
material for an effective amount of time to result in a final
particle size from about 100 to 300 nm, which second polymer
material is comprised of a polar segment and a non-polar segment
and which second polymer material is a dispersant with respect to
the pigment particles
30. The method of claim 29 wherein the monomer contributing to the
non-polar segment of said polymer material is selected from the
group consisting of polydimethylsiloxane, propoxylated allyl
methacrylate, nonylphenyl ppg acrylate, stearyl methacrylate,
ethylene glycol, ether methacrylate and alkyl(meth) acrylate.
31. The method of claim 29 wherein the monomer contributing to the
polar segment of said polymer material is selected from the group
consisting of hydroxyethyl methacrylate, hydroxy terminated
monomer, combined with or without acid-amine monomers.
32. The method of claim 30 wherein the monomer contributing to the
non-polar segment is an alkyl(meth ) acrylate.
33. The method of claim 32 wherein the alkyl(meth) acrylate is
selected from n-butyl acrylate and methyl methacrylate.
34. The method of claim 29 wherein the organic solvent is selected
from the group consisting of acetone, isopropyl alcohol, ethylene
glycol, 2-pyrrolidone and propylene glycol.
35. The method of claim 29 wherein the paste of step c) is washed
with water and dried.
36. The method of claim 29 wherein the organic solvent is also used
as a humectant in a final ink formulation and thus is not driven
off.
37. The method of claim 21 wherein: i) the monomer contributing to
the polar segment of said polymer material is selected from the
group consisting of hydroxyethyl methacrylate, hydroxy terminated
monomer, combined with or without acid-amine monomers; and ii) the
organic solvent is selected from the group consisting of acetone,
isopropyl alcohol, ethylene glycol, 2-pyrrolidone and propylene
glycol.
38. The method of claim 37 wherein the monomer contributing to the
non-polar segment is an alkyl(meth ) acrylate.
39. The method of claim 38 wherein the paste of step c) is washed
with water and dried.
40. The method of claim 37 wherein the organic solvent is also used
as a humectant in a final ink formulation and thus is not driven
off.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to encapsulated pigment for use in
ink-jet ink formulations, improved ink-jet ink formulations using
the encapsulated pigment, and methods for producing same.
[0003] 2. Description of Related Art
[0004] Ink-jet printing is a conventional technique by which
printing is normally accomplished without contact between the
printing apparatus and the medium on which the desired print
characters are deposited. Such printing is accomplished by ejecting
ink from an ink-jet printhead of the printing apparatus via
numerous methods that employ, for example, pressurized nozzles,
electrostatic fields, piezo-electric elements and/or heaters for
vapor-phase bubble formation.
[0005] Ink compositions used in ink-jet printing typically employ
water, colorants and low molecular weight water-soluble or
water-miscible solvents. The colorants are generally selected from
dyes and pigments. Dye-based inks, while in general superior in
color properties, have several disadvantages as compared to
pigment-based inks. For example, dyes are usually water-soluble and
remain so after drying on the print medium, and thus are easily
re-dissolved by water spills. In addition, dyes typically exhibit
relatively poor light stability relative to pigments and are known
to fade even under normal office lighting. Thus, dye-based inks are
often unsuitable for use in applications requiring water resistance
and light stability. Consequently, pigments are generally preferred
colorants for ink-jet ink formulations.
[0006] Unfortunately, the use of pigments in ink-jet ink
formulations is not problem free. For example, pigments are
typically water insoluble and exist as discrete particles in the
final ink formulation and have a tendency to aggregate. The
insoluble pigment particles are typically stabilized as a
dispersion by use of a polymer dispersant component having a
hydrophobic segment and a hydrophilic segment. Generally speaking,
most pigment inks stabilized with polymer dispersants in aqueous
media are based on an electosteric stabilizing mechanism in which
the hydrophobic segment of the dispersant acts as an anchor
adsorbed onto the surface of the pigment particle through
acid-base, electron donor/acceptor, Van der Waals forces, or
physical absorption. In such a system, the hydrophilic segment of
the dispersant is extended into the aqueous medium to keep the
dispersant dispersed and to set up an electosteric layer to prevent
aggregation of the pigment particles.
[0007] Many interrelated and competing forces are present in these
complex pigmented ink formulations, consequently, it is extremely
difficult to formulate a polymer dispersant system for pigmented
ink-jet inks that simultaneously provide improved stability,
water-fastness, light-fastness, smear resistance, highlighter
resistance, minimized nozzle clogging and print density.
[0008] It is desirable to produce a final ink formulation having as
many of these properties as possible, especially smear resistance
and highlighter resistance. Conventional methods for producing
pigment-based ink-jet inks using conventional polymer dispersants
fall short since they typically have inferior film-forming
properties. Pigment-to-dispersant ratio plays an important role in
the film-forming property versus optical density. For example, a
higher level of dispersant will typically improve smear resistance
but at the expense of optical density. One conventional solution to
this problem is to use a binder to improve film-forming properties,
such as those taught in U.S. Pat. No. 6,063,834 which is
incorporated herein by reference. Binders are typically very
sensitive to heat and thus are not compatible with thermal ink-jet
print heads. Therefore, the amount of binder that can be added to
the ink is limited and thus, the ink does not produce high quality
print.
[0009] Therefore, there still remains a need in the art for ink-jet
ink formulations and manufacturing techniques that leads to print
having improved properties.
SUMMARY OF THE INVENTION
[0010] In accordance with the present invention, there is provided
encapsulated-pigment particles for use in ink-jet ink formulations,
which pigment particles are at least partially encapsulated with
one or more polymer materials, which polymer materials are at least
partially soluble in an organic solvent, but substantially
insoluble in water.
[0011] Also, in accordance with the present invention, there is
provided a method for producing encapsulated pigment particles
suitable for ink-jet ink formulations, which method comprising: a)
at least partially dissolving an organic soluble polymer material
in an organic solvent, thereby forming a solution; b) introducing
an effective amount of pigment particles into the resulting
polymer/solvent solution, thereby forming a slurry; c) mixing the
slurry at effective conditions to form a paste; and d) drying off
the solvent thereby leaving pigment particles that are at least
partially encapsulated with the polymer material.
[0012] The paste of step c) can be subjected to a water wash and
dried, but the preferred embodiment is to drive off the solvent
when feasible.
[0013] Also in accordance with the present invention, there is
provided ink-jet ink formulations comprising: a) an aqueous
carrier; b) an effective amount of pigment particles that are at
least partially encapsulated with a first polymer material, which
first polymer material is at least partially soluble in organic
solvent, but which is substantially insoluble in water; and c) a
second polymer material that is a dispersant for the pigment and
which is at least partially soluble or miscible in water.
[0014] In preferred embodiments of the present invention there is
also present in the ink formulations at least one additive selected
from the group consisting of driers, waxes, antioxidants,
lubricants, surfactants, defoamers, wetting agents, biocides,
chelators, and anti-curling agents.
[0015] Also in accordance with the present invention there is
provided a method for preparing an ink-jet ink formulation
comprising: a) at least partially dissolving an organic soluble
first polymer material in an organic solvent, thereby resulting in
a solution; b) introducing an effective amount of pigment particles
into the resulting polymer/solvent solution thereby forming a
slurry of pigment particles in the polymer/solvent solution; c)
mixing the slurry at effective conditions to form a paste; d)
drying off the solvent, thereby resulting in pigment particles that
are at least partially encapsulated with the first polymer
material; and e) grinding the encapsulated pigment particles with a
water soluble or water miscible second polymer material that is a
dispersant for the pigment for an effective amount of time to
result in a final particle size from about 50 nm to 300 nm.
DETAILED DESCRIPTION OF THE INVENTION
[0016] This invention relates to improved pigment for ink-jet ink
formulations and a method of producing them. A first polymer
material is used to pre-treat the pigment particles before grinding
them with conventional second polymer dispersant materials that are
water-soluble or water miscible. The first polymer material, which
is substantially insoluble in water, will be at least partially,
preferably substantially totally, encapsulate the pigment
particles. The ink formulations prepared with the encapsulated
pigments of the present invention result in improved print that is
substantially smear-free and highlighter resistant on suitable
substrates, with improved print quality such as water-fastness and
light-fastness.
[0017] There is no limitation with respect to the pigments that can
be used in this invention, other than that they be suitable for use
in ink-jet ink formulations. Any of the commonly employed organic
and inorganic pigments can be used in the practice of the present
invention. Non-limiting examples of pigments that can be used in
the practice of the present invention include azo pigments such as
condensed and chelate azo pigments; polycyclic pigments such as
phthalocyanines, anthraquinones, quinacridones, thioindigoids,
isoindolinones and quinophthalones. Still other pigments that can
be employed include, for example, nitro pigments, daylight
fluorescent pigments, carbonates, chromates, titanium oxides, zinc
oxides, iron oxides and carbon black. A more complete list of such
pigments can be found in U.S. Pat. No. 6,057,384, which is
incorporated herein by reference. Such pigments can be prepared by
any conventional technique and many of them are commercially
available.
[0018] The pigment is pre-treated in accordance with the present
invention by treating it with a first polymer material that is at
least partially soluble in an organic solvent but substantially
insoluble in water. It is preferred that an organic solvent be used
in which the polymer is totally soluble at the concentrations
needed to encapsulate the pigment particles. That is, wherein the
polymer dissolves without any residual solids remaining.
Conventional methods teach grinding pigment with a water-soluble
polymer material dispersant without first pre-treating it with a
water-insoluble polymer material. It is preferred that the first
polymer material have: a) a relatively strong affinity for the
second polymer material; b) film-forming ability; and c) a
relatively strong affinity for the pigment. It is also preferred
that the first polymer material be structurally similar to the
second polymer material used to prepare the final ink formulation.
The polymer materials used herein will also have a polar and a
non-polar segment. It is more preferred that both polymer materials
have a polar segment and a non-polar segment, which are often
referred to as a hydrophilic segment and a hydrophobic segment. The
average weight molecular weight is preferred from 1,000-15,000 more
preferred is from 3,000-10,000, most preferred 5,000-8,000.
[0019] Non-limiting examples of preferred monomers that can
contribute to the non-polar section of the first polymer material
include: polydimethylsiloxane, propoxylated allyl methacrylate,
nonylphenyl polypropylene gylcol acrylate, stearyl methacrylate,
ethylene glycol, dicyclophentenyl ether methacrylate,
alkyl(meth)acrylate, styrene, poly(ethylene
glycol)2,4,6,-tris(1-phenylethyl)phenyl ether,
2-(2'hydroxy-5'-methacryloxyethyl-phenyl)-2H-benzotriazole and the
like. More preferred are the alkyl(meth)acrylates, nonylphenyl
polypropylene glycol, and
2-(2'hydroxy-5'-methacryloxyethyl-phenyl)-2H-benzotriazole. Most
preferably are the alkyl(meth) acrylates, particularly n-butyl
acrylate and methyl methacrylate styrene. Non-limiting examples of
preferred monomers that can contribute to the polar section of the
polymer material include: hydroxyethyl methacrylate, hydroxy
terminated monomer, combined with or without acid-amine monomers
and the like. More preferred is hydroxyethyl methacrylate. The
ratio of pigment to first polymer material will be from about 10 to
1 to about 1 to 1, preferably from about 3 to 1 to about 1 to
1.
[0020] One preferred method of practicing the present invention is
to encapsulate the pigment particles with a first polymer material
by: a) dissolving a water-insoluble polymer material in a suitable
organic solvent thereby resulting in a polymer/solvent solution; b)
introducing an effective amount of pigment particles into the
solution thereby resulting in a slurry of pigment particles in the
polymer/solvent solution; c) mixing, or kneading the slurry for an
effective amount of time and under effective conditions to form a
paste; and d) driving, or drying, off the solvent and collecting
the pigment particles that will be at least partially encapsulated
with the first polymer material. It is preferred that the pigment
particles be substantially totally encapsulated with the first
polymer material.
[0021] It will be understood that after the mixing, or kneading
step, the resulting paste can be washed with water and dried
depending on whether or not the organic solvent is also used as a
humectant in the final ink formulation. An alternative is to simply
dry, or evaporate off, the solvent if a relatively low-boiling
solvent is used, such as acetone or isopropyl alcohol. Further, a
mixture of a high-boiling and a low-boiling solvents can be used in
which case the low-boiling solvent can be dried off and the
higher-boiling solvent left as a humectant for the final ink
formulation. For example, if the solvent is not used as a humectant
in the final ink formulation, or if the amount of solvent in the
paste would exceed that called for in the final ink formulation,
then it will be necessary to wash and dry the paste. If the solvent
can also be used as a humectant in the final ink formulation, and
if the amount of organic solvent does not exceed that required for
the final ink formulation, then it is preferred not to wash and dry
the paste.
[0022] The mixing of pigment particles and first polymer material
can be accomplished in any suitable mixing device so long as the
mixing is energetic enough to associate the polymer material with
the pigment particles to result in at least a partial encapsulation
of the pigment particles. It is preferred that substantially all of
the pigment particles be substantially entirely encapsulated with
the polymer material.
[0023] The selected pigment can be used in dry or wet form, with a
dry-powder form being preferred. Pigments are usually manufactured
in an aqueous media and the resulting pigment is often obtained as
water-wet presscake. Thus, pigments in water-wet presscake form
typically do not require much deflocculation in the process of
preparing the inks as dry pigments.
[0024] Once the pigment particles have been encapsulated with the
polymer material there is no limitation with respect to the method
used to prepare the ink formulations. Essentially, the components
(e.g., encapsulated pigment, additive, polymer dispersant, and
water carrier) of the inks can, for example, be mixed, stirred or
agitated using any conventional technique to reduce the size of the
pigment particles. This is generally accomplished by use of
grinding mill used to produce the particle size of about 50 nm to
300 nm, preferably to less than about 200 nm, and more preferably
to less than about 140 nm. This particle size is achieved by
extensive shearing of the pigment particles using small grinding
media. Typical of the grinding media includes spherical particles
made from suitable materials, such as stainless steel, zirconium
silicate, zirconium oxide and glass. Preferred grinding media are
spherical ceramic particles having a smooth and substantially
uniform exterior surface, a high density and high hardness. A
particularly preferred grinding medium is a material commercially
available under the name YTZ Ceramic Beads, commercially available
from S. E. Firestone Associates. This material is in the form of
spherical ceramic particles having a core of a high purity
zirconium oxide treated with yttrium to make the spheres highly
wear resistant. Grinding times will typically be from about 7 to 12
hours and solids content in grinding will be about 20 wt. %, which
will be lowered to about 12 to 15 wt. % with deionized water, after
grinding.
[0025] It is preferred to grind the components in a suitable
grinding device such as an attritor using suitable grinding media,
such as conventional grinding beads. The addition of the components
is not limited to any particular order so long as the resulting ink
formulation is one that can be satisfactorily used to produce print
on a suitable substrate.
[0026] The second polymer material can act as both the wetting
agent and the dispersant that stabilizes the pigment particles and
prevents them from agglomerating. There is essentially no
limitation with respect to the dispersants that can be used in this
invention. In fact, any non-polymer or polymer dispersant that can
be used to make a pigment-based ink formulation can be used in this
invention. The preferred dispersants are polymer dispersants. An
illustrative list of such polymer dispersants include random, block
and branched polymers, whereby the polymers can be anionic,
cationic or nonionic in nature. The polymer dispersants typically
have polar segments for aqueous solubility and non-polar segments
for pigment interaction. Moreover, polymer dispersants, as used
herein, are meant to include water-soluble homopolymers and
copolymers (including terpolymers).
[0027] Since the second polymer material used in this invention are
generally limited only to the extent that they are capable of
dispersing a colorant (pigment) in an aqueous-based ink
formulation, the precursor units that can be used to make such
polymer dispersants are not limited. Precursor, as used herein, is
meant to include monomeric and macromeric units.
[0028] A general list of the monomeric units that can be employed
to make such second polymer dispersant materials include, for
example, acrylic monomers, styrene monomers and monomers having
acid/amine groups. Illustrative examples of the monomers that can
be employed include acrylic and methacrylic acid, acrylamide and
methacrylamide. Such polymer dispersants tend to be any of those
that are commercially available as well as the polymer dispersants
that can be made via conventional techniques that include, for
example, condensation and addition polymerizations such as anionic,
group transfer or free radical polymerizations of monomeric
units.
[0029] The preferred polymer dispersants that can be employed in
this invention as the second polymer material are random
terpolymers prepared from three precursors. The most preferred
precursors include monomeric and macromeric precursors, including
at least one member selected from the group consisting of acrylates
and methacrylates, at least one member selected from the group
consisting of acryloyl-and methacryloyl-terminated
polydiakylsiloxanes and at least one member selected from the group
consisting of stearyl acrylate, stearyl (meth)acrylate, nonyl
phenyl(polypropylene glycol) methacrylate, and lauryl methacrylate.
A more preferred polymer dispersant used herein is referred to as
Lexmark.TM. acrylic terpolymer and is made from polymerizing
methacrylic acid, stearyl methacrylate, and dimethylsiloxane.
[0030] The polymer dispersants prepared from these particularly
preferred precursors can be made by polymerizing the monomeric and
macromeric precursors via art-recognized techniques that include
free radical polymerizations. A more detailed description of the
most preferred polymer dispersants that can be employed in this
invention can be found in U.S. Pat. Nos. 5,719,204 and 6,225,370,
the disclosures of which are incorporated herein by reference.
Generally, free radical polymerization used to prepare the polymer
dispersants utilize initiators and chain transfer agents to control
the polymer molecular weight. Any conventional free radical
initiator can be used in the present invention as long as they are
compatible with the reactants being utilized. Suitable free radical
initiators include the azo-type and peroxide-type initiators.
Preferred initiators are the azo-type. Preferred initiators include
dimethyl 2,2'-azobisisobutyrate (V-601TM), AIBNTM and V-501TM from
the Wako Company.
[0031] Other additives can be added to the ink formulation.
Non-limiting examples of such additives include driers, waxes,
antioxidants, lubricants, surfactants, gallants, defoamers, wetting
agents, biocides, chelators, and anti-curling agents.
[0032] The surfactants can be anionic, cationic, or amphoteric
non-ionic surfactants. Non-limiting examples of suitable anionic
surfactants include fatty acid salt, alkyl sulfate, alkylaryl
sulfonate, alkylnaphthalene sulfonate, dialkyl sulfonate, dialkyl
sulphosuccinate, alkyl diaryl ether disulfonate, alkyl phosphate,
polyoxyethylene alkyl ether sulfate, polyoxyethylene alkylaryl
ether sulfate, naphthalene sulfonate-formalin condensate,
polyoxyethylene alkyl phosphate, glycerol borate fatty acid ester
and polyoxyethylene glycerol fatty acid ester.
[0033] Non-limiting examples of suitable the nonionic surfactants
include polyoxyethylene alkyl ether, polyoxyethylene alkylaryl
ether, polyoxyethylene oxypropylene block copolymer, sorbitan fatty
acid ester, polyoxyethylene sorbitan fatty acid ester,
polyoxyethylene sorbitol fatty acid ester, glycerin fatty acid
ester, polyoxyethylene fatty acid ester polyoxyethylene alkylamine,
a fluorine-containing nonionic surfactant and a silicon-containing
nonionic surfactant.
[0034] Non-limiting examples of suitable the cationic surfactants
include alkylamine salt, ammonium salt, alkylpyridinium salt and
alkylimidazolium salt. Examples of the amphoteric surfactants
include alkylbetaine, alkylamine oxide and phosphatidylcholine.
[0035] The aqueous carrier used for the ink formulations of the
present invention is comprised of water or a mixture of water and
at least one water-soluble organic solvent. Selection of a suitable
mixture depends on requirements of the specific application, such
as desired surface tension and viscosity, the selected pigment,
drying time of the pigmented ink jet-ink, and the type of paper
onto which the ink will be printed. Representative examples of
water-soluble organic solvents that can be selected include (1)
alcohols, such as methyl alcohol, ethyl alcohol, n-propyl alcohol,
iso-propyl alcohol, n-butyl alcohol, sec-butyl alcohol, t-butyl
alcohol, iso-butyl alcohol, furfuryl alcohol, and
tetrahydrofurfuryl alcohol; (2) ketones or ketoalcohols such as
acetone, methyl ethyl ketone and diacetone alcohol; (3) ethers,
such as tetrahydrofuran and dioxane; (4) esters, such as ethyl
acetate, ethyl lactate, ethylene carbonate and propylene carbonate;
(5) polyhydric alcohols, such as ethylene glycol, diethylene
glycol, triethylene glycol, propylene glycol, tetraethylene glycol,
polyethylene glycol, glycerol, 2-methyl-2,4-pentanediol
1,2,6-hexanetriol and thiodiglycol; (6) lower alkyl mono- or
di-ethers derived from alkylene glycols, such as ethylene glycol
mono-methyl (or -ethyl) ether, diethylene glycol mono-methyl (or
-ethyl) ether, propylene glycol mono-methyl (or -ethyl) ether,
triethylene glycol mono-methyl (or -ethyl) ether and diethylene
glycol di-methyl (or -ethyl) ether; (7) nitrogen containing cyclic
compounds, such as pyrrolidone, N-methyl-2-pyrrolidone, and
1,3-dimethyl-2-imidazoli- dinone; and (8) sulfur-containing
compounds such as dimethyl sulfoxide and tetramethylene
sulfone.
[0036] The ink-jet ink formulations of the present invention can
contain 0.05 to 1.0% by weight, based on the ink formulation, of a
biocide for preventing the occurrence of biological growth.
[0037] A pH adjuster such as an amine, an inorganic salt or ammonia
and a buffer solution such as phosphoric acid can be used for
adjusting the pH of the ink formulation, stabilizing the ink and
stabilizing an ink-tubing in a recording device.
[0038] Further, the ink formulations of the present invention can
contain an anti-foaming agent for preventing the occurrence of
foams when the ink is circulated, moved or produced.
[0039] The following examples serve to exemplify a more general
description set forth above and are for illustrative purposes only
and are not intended to limit the scope of the present invention in
any way.
EXAMPLE 1
Preparation of the Water Insoluble Polymer-A (WIPA)
[0040] The following ingredients were weighed into a round bottom
flask:
1 2-Hydroxyethyl Methacrylate 24.38 g n-Butyl Acrylate 40.00 g
Methyl Methacrylate 12.50 g Dodecanethiol 3.79 g Isopropyl Alcohol
200 mL V-601 azo Initiator 0.71 g
[0041] The flask was equipped with a condenser, a thermometer and a
mechanical stirrer. The flask was evacuated and then back-filled
with nitrogen. The reaction mixture was then heated using an oil
bath to 75.degree. C. and maintained at that temperature for 18
hours. The reaction mixture was then cooled to room temperature
(about 24.degree. C.) and transferred to a bottle. The weight
average molecular weight (MW) was 6813 and the percent solids was
about 35%.
[0042] The Water Soluble Polymer-A (WSPA)
[0043] The water-soluble polymer used for this example contained
the following monomer set at a molar ratio of 9:1:1 respectively,
all the water soluble polymers may be prepared by the method
described in U.S. Pat. No. 5,714,538 to Beach et al. (incorporated
herein by this reference).
[0044] Methacrylic Acid
[0045] Poly(ethylene glycol) 2,4,6-tris
[0046] (1-phenylethyl)phenyl ether methacrylate (60%)
[0047] Polydimethyl Siloxane Methacrylate
[0048] Encapsulation of Pigment (PA)
[0049] The following ingredients were weighed into a beaker:
2 Self Dispersing Carbon Black (CB) - 15.0 g (oxidized with sodium
hypochlorite) Water Insoluble Polymer-A (still in IPA solution)
15.0 g (polymer only)
[0050] The ingredients were thoroughly mixed until substantially
all of the pigment was wetted. The wetted ingredients were then
placed in an oven at 85.degree. C. for 18 hour whereupon they were
removed and placed in a bottle until ready for use. Encapsulation
of Pigment (PB)
[0051] The procedure for preparing pigment PA was followed except
15.5 g of Monarch 880 pigment was used instead of the
self-dispersing carbon black and 15.5 g of water insoluble polymer
(WIPA) was used.
[0052] Method for Dispersing Encapsulated Pigment
[0053] The following ingredients were weighed into an attritor
cup:
3 Encapsulated Monarch 880 (PB) 31.00 g Water Soluble Polymer-A
(based on 15% solution) 33.33 g Poly(ethylene glycol) 400 30.00 g
Deionized Water 85.67 g
[0054] The ingredients were ground for 16 hours after which the
resulting dispersion was separated from the grinding media using a
sieve. The dispersion, having an average particle size of 295 nm,
was stored in a bottle for use in an ink formulation.
[0055] The above procedure for dispersing the encapsulated pigment
was used except the ingredients weighed into an attritor cup
were:
4 Encapsulated Self Dispersing CB (PA) 30.00 g Water Soluble
Polymer-A (based on 15% solution) 40.00 g Poly(ethylene glycol) 400
30.00 g Deionized Water 80.00 g
[0056] A control ink formulation and an encapsulated pigment ink
formulation were prepared as set forth in the Table 1 below. All
percents are by weight based on the total weight of the ink
formulation.
5TABLE 1 Control: Encapsulated Pigment Formulation 2% pigment
Monarch 880 2% pigment encapsulated M880 dispersion 2% pigment
self-dispersed carbon 2% pigment encapsulated self black dispersed
carbon black 7.5% Polyethylene Glycol 400 7.5% Polyethylene Glycol
400 7.5% 2-Pyrrolidone 7.5% 2-Pyrrolidone 1.2% 1,2-Hexanediol 1.2%
1,2-Hexanediol 0.4% Hexylcarbitol 0.4% Hexycarbitol 0.5-2.5% Binder
Balance deionized water Balance deionized water
[0057] Each ink formulation was filtered and filled into ink-jet
printheads for print testing. Table 2 below shows the results
obtained for highligther smear. "+" means better than the control,
"=" means equal to the control, and "-" means not as good as the
control.
6 TABLE 2 Control Encapsulated Pigment No Binder + 0.5% Binder +
1.0% Binder + 2.5% Binder nearly =
EXAMPLE 2
Preparation of Water Insoluble Polymer-B:
[0058] The following ingredients were weighed into a round bottom
flask:
7 2-Hydroxyethyl Methacrylate 37.70 g PolyDimethyl Siloxane(1000
Mw) 1.13 g Stearyl Methacrylate 12.50 g Dodecanethiol 8.81 g
Isopropyl Alcohol 100 mL V-601 Azo Initiator 0.76 g
[0059] The flask was equipped with a condenser, a thermometer and a
mechanical stirrer. The flask was evacuated and then back-filled
with nitrogen. The reaction mixture was then heated with an oil
bath to 75.degree. C. and maintained at that temperature for 18
hours. The reaction mixture was then cooled to room temperature and
transferred to a bottle. The weight average as 5464 and the percent
solids was about 40%.
[0060] Example 1 was then followed using the same pigments,
encapsulation procedures, ink formulations, and testing of the ink
formulations. The results are set forth in Table 3 below.
8 TABLE 3 Control Encapsulated Pigment No Binder + 0.5 wt. % Binder
+ 1.0 wt. % Binder = 2.5 wt. % Binder -
EXAMPLE 3
Preparation of Water Insoluble Polymer-C:
[0061] The following ingredients were weighed into a round bottom
flask:
9 2-Hydroxyethyl Methacrylate 37.70 g Poly(propylene glycol)
4-noniylphenyl ether Acrylate 15.19 g Poly(Dimethyl Siloxane(1000
Mw) 31.13 g Dodecanethiol 8.91 glsopropyl Alcohol 125 mL V-601 Azo
Initiator 0.82 g
[0062] The flask was equipped with a condenser, a thermometer, and
a mechanical stirrer. The flask was evacuated and then back-filled
with nitrogen. The reaction mixture was then heated using an oil
bath to 75.degree. C. and maintained at that temperature for 18
hours. The reaction mixture was then cooled to room temperature and
transferred to a bottle. The weight average molecular weight was
5084 and the percent solids was about 40%.
[0063] Water Soluble Polymer-B:
[0064] The water-soluble polymer (B) used for this example was
comprised of the following monomer set at the molar ratio 8:1:1
respectively.
[0065] Methacrylic Acid
[0066] Poly(propyl cne glycol) 4-nonylphenyl ether acrylate
[0067] Polydimethyl Siloxane Methacrylate
[0068] Encapsulation of the Pigment C:
[0069] The following ingredients were weighed into a beaker:
10 Pigment Blue 15:3 15.0 g Water insoluble polymer 15.0 g (polymer
only) (still in IPA solution)
[0070] The ingredients were thoroughly mixed until substantially
all pigment was wetted. The resulting mixture was placed in oven at
85.degree. C. for 18 hours, then removed and placed in a bottle
until ready for use.
[0071] Method of Dispersing Encapsulated Pigments:
[0072] The following ingredients were weighed into an attritor
cup:
11 Encapsulated Pigment Blue 15:3 30.00 g Water Soluble Polymer
(based on 15% solution) 40.00 g Poly(ethylene glycol) 400 30.00 g
DI Water 80.00 g
[0073] The ingredients were ground for 16 hours, after which the
resulting dispersion was separated from the grinding media using a
sieve. The resulting dispersion was stored in a bottle for use in
an ink formulation.
[0074] A control ink formulation and an encapsulated pigment blue
ink formulation were prepared as set forth in Table 4 below. All
percents are by weight based on the total weight of the ink
formulations.
12TABLE 4 Control: Encapsulated Pigment Formulation 2% pigment
Monarch 880 2% encapsulated Pigment Blue dispersion 15:3 2% pigment
self-dispersed carbon 2% encapsulated self dispersed black carbon
black pigment (PA) 7.5% Polyethylene Glycol 400 7.5% Polyethylene
Glycol 400 7.5% 2-Pyrrolidone 7.5% 2-Pyrrolidone 1.2%
1,2-Hexanediol 1.2% 1,2-Hexanediol 0.4% Hexylcarbitol 0.4%
Hexycarbitol 0.5-2.5% Binder Balance deionized water Balance
deionized water
[0075] The inks were then filtered and filled in ink-jet printheads
for print testing. The results for the hi-liter smear test are set
forth in Table 5 below.
13 TABLE 5 Control Encapsulated Pigment No Binder + 0.5 wt. %
Binder + 1.0 wt. % Binder = 2.5 wt. % Binder -
EXAMPLE 4
Preparation of the Water Insoluble Polymer-D:
[0076] The following ingredients were weighed into a round bottom
flask:
14 2.Hydroxyethyl Methacrylate 8.00 g Sipomer SEM-251 from Rhodia
80.00 g Norbloc 7966 (Jansen) 15.00 g Dodecanethiol 3.50 g
Isopropyl Alcohol 50 mL Tetrahydrofuran 50 mL V.601 Azo Initiator
0.30 g
[0077] 1 Sipomer SEM-25 is poly(ethylene glycol)
2,4,6-tris(1-phenylethyl)- phenyl ether.
[0078] 2 Norbloc 7966 is
2-(2'Hydroxy-5'-methacryloxyethylphenyl)-2H-benzo- triazole.
[0079] The flask was equipped with a condenser, a thermometer and a
mechanical stirrer. The flask was evacuated, then back-filled with
nitrogen. The reaction mixture was then heated using an oil bath to
75.degree. C. and maintained at that temperature for 18 hours. The
reaction mixture was then cooled to room temperature and
transferred to a bottle. The weight average molecular weight was
8535 and the percent solids was about 40%.
[0080] Example 1 was then followed using the same pigments,
encapsulation procedures, ink formulations, and testing of the ink
formulations. The results are set forth in Table 6 below.
15 TABLE 6 Control Encapsulated Pigment No Binder + 0.5 wt. %
Binder + 1.0 wt. % Binder = 2.5 wt. % Binder -
EXAMPLE 5
Preparation Of Water Insoluble Polymer E
[0081]
16 2-Hydroxyethyl Methacrylate 35.19 g Styrene 30.00 g Butyl
Acrylate 8.50 g Dodecancthiol 3.56 g Isopropyl Alcohol 200 ml V-601
0.71
[0082] Preparation method is the same as WIPA and the product has
an average weight molecular weight 6000and 37% solid.
[0083] Preparation of Water Soulble Polymer C
[0084] This polymer contains the following monomer set, at a molar
ration 15:1:1 respectively.
[0085] Methacrylate Acid
[0086] Poly (propyl ene glycol) 4-nonylphenyl ether acrylate
[0087] Poly (ethylene glycol) 2,4,6,-tris (1-phenylethyl)phenyl
ether methacrylate
[0088] Encapsulation of the Pigment:
17 Polymer E 13.8 g Pigment yellow 74 18.0 g Diethylene glycol 8.0
g
[0089] The ingredients were mixered together and dried off the IPA
in oven.
[0090] Method of Dispersing Encapsulated Pigment
[0091] Encapsulated Pigment Yellow 74
[0092] 51.8 g of polymer C (based on 12.08% aqueous solution 60 g
of DI water)
[0093] Grinding for 12 hours and the final particle size is 191
nm
[0094] The control experiment used the same method without add
polymer.
[0095] Ink is made from the above concentrate in the following
formulation:
18 Pigment 3% 2-pyrrolindone 5% PEG 1000 5% Thiodiethanol 5% 1,2
Hexanediol 1% Balance water
[0096] Lightfastness of the ink is tested on Kodak Premium Photo
Paper. Sample of the prints are faded for a week with Xenon arc
lamp. Humidity was not controlled.
19 TABLE 7 DeltaE @ OD = 1 % change in OD Control 37.4 50% Example
5 14.3 19%
* * * * *