U.S. patent application number 11/759913 was filed with the patent office on 2008-12-11 for nanosized particles of monoazo laked pigment.
This patent application is currently assigned to XEROX CORPORATION. Invention is credited to C. Geoffrey Allen, Jennifer L. Belelie, Rina CARLINI, Karl W. Dawson, Sandra J. Gardner, Peter G. Odell, Paul F. Smith.
Application Number | 20080302271 11/759913 |
Document ID | / |
Family ID | 39855241 |
Filed Date | 2008-12-11 |
United States Patent
Application |
20080302271 |
Kind Code |
A1 |
CARLINI; Rina ; et
al. |
December 11, 2008 |
NANOSIZED PARTICLES OF MONOAZO LAKED PIGMENT
Abstract
A nanoscaled pigment particle composition includes an organic
monoazo laked pigment including at least one functional moiety, and
a sterically bulky stabilizer compound including at least one
functional group, wherein the functional moiety associates
non-covalently with the functional group; and the presence of the
associated stabilizer limits the extent of particle growth and
aggregation, to afford nanoscale-sized pigment particles.
Inventors: |
CARLINI; Rina; (Mississauga,
CA) ; Allen; C. Geoffrey; (Waterdown, CA) ;
Gardner; Sandra J.; (Oakville, CA) ; Dawson; Karl
W.; (Ottawa, CA) ; Odell; Peter G.;
(Mississauga, CA) ; Smith; Paul F.; (Oakville,
CA) ; Belelie; Jennifer L.; (Oakville, CA) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC.
P.O. BOX 320850
ALEXANDRIA
VA
22320-4850
US
|
Assignee: |
XEROX CORPORATION
Stamford
CT
|
Family ID: |
39855241 |
Appl. No.: |
11/759913 |
Filed: |
June 7, 2007 |
Current U.S.
Class: |
106/31.61 ;
106/31.8; 106/402 |
Current CPC
Class: |
C09B 67/0005 20130101;
B82Y 30/00 20130101; C09D 11/101 20130101; C09B 67/0009 20130101;
C09D 11/34 20130101; C09D 11/037 20130101; C09D 7/41 20180101; C09D
11/322 20130101; C09B 63/005 20130101 |
Class at
Publication: |
106/31.61 ;
106/31.8; 106/402 |
International
Class: |
C09B 63/00 20060101
C09B063/00; C09D 11/00 20060101 C09D011/00 |
Claims
1. A nanoscale pigment particle composition, comprising: an organic
monoazo laked pigment having at least one functional moiety, and a
sterically bulky stabilizer compound having at least one functional
group, wherein the functional moiety associates non-covalently with
the functional group; and presence of the associated stabilizer
limits an extent of particle growth and aggregation, to afford
nanoscale-sized pigment particles.
2. The composition of claim 1, wherein the nanoscale-sized pigment
particles have an average particle diameter as derived from
transmission electron microscopy imaging, of less than about 150
nm.
3. The composition of claim 1, wherein the at least one functional
moiety of the organic monoazo laked pigment is selected from the
group consisting of sulfonate/sulfonic acid,
(thio)carboxylate/(thio)carboxylic acid, phosphonate/phosphonic
acid, ammonium and substituted ammonium salts, phosphonium and
substituted phosphonium salts, substituted carbonium salts,
substituted arylium salts, alkyl/aryl (thio)carboxylate esters,
thiol esters, primary or secondary amides, primary or secondary
amines, hydroxyl, ketone, aldehyde, oxime, hydroxylamino, enamines
(or Schiff base), porphyrins, (phthalo)cyanines, urethane or
carbamate, substituted ureas, guanidines and guanidinium salts,
pyridine and pyridinium salts, imidazolium and (benz)imidazolium
salts, (benz)imidazolones, pyrrolo, pyrimidine and pyrimidinium
salts, pyridinone, piperidine and piperidinium salts, piperazine
and piperazinium salts, triazolo, tetraazolo, oxazole, oxazolines
and oxazolinium salts, indoles, and indenones.
4. The composition of claim 1, wherein the organic monoazo laked
pigment comprises a diazonium component linked to a coupling
component through an azo or hydrazone group, with a counterion.
5. (canceled)
6. The composition of claim 4, wherein the coupling component is
selected from the group consisting of .beta.-naphthol and
derivatives thereof, naphthalene sulfonic acid derivatives,
pyrazolone derivatives, and acetoacetic arylide derivatives.
7. (canceled)
8. The composition of claim 4, wherein the counterion is selected
from the group consisting of metals, non-metals, and carbon-based
cations or anions.
9. (canceled)
10. The composition of claim 1, wherein the at least one functional
group of the sterically bulky stabilizer is selected from the group
consisting of sulfonate/sulfonic acid,
(thio)carboxylate/(thio)carboxylic acid, phosphonate/phosphonic
acid, ammonium and substituted ammonium salts, phosphonium and
substituted phosphonium salts, substituted carbonium salts,
substituted arylium salts, alkyl/aryl (thio)carboxylate esters,
thiol esters, primary or secondary amides, primary or secondary
amines, hydroxyl, ketone, aldehyde, oxime, hydroxylamino, enamines
(or Schiff base), porphyrins, (phthalo)cyanines, urethane or
carbamate, substituted ureas, guanidines and guanidinium salts,
pyridine and pyridinium salts, imidazolium and (benz)imidazolium
salts, (benz)imidazolones, pyrrolo, pyrimidine and pyrimidinium
salts, pyridinone, piperidine and piperidinium salts, piperazine
and piperazinium salts, triazolo, tetraazolo, oxazole, oxazolines
and oxazolinium salts, indoles, and indenones.
11. The composition of claim 1, wherein the sterically bulky
stabilizer comprises at least one aliphatic hydrocarbon moiety.
12. (canceled)
13. The composition of claim 1, further comprising a surfactant
selected from the group consisting of derivatives of rosin natural
products; acrylic-based polymers; styrene-based copolymers;
copolymers of .alpha.-olefins; copolymers of vinyl pyridine, vinyl
imidazole, and vinyl pyrrolidinone; polyester copolymers; polyamide
copolymers; and copolymers of acetals and acetates.
14. The composition of claim 1, wherein the non-covalent
association between the organic monoazo laked pigment and the
sterically bulky stabilizer compound is at least one of van der
Waals' forces, ionic bonding, coordination bonding, hydrogen
bonding, and aromatic pi-stacking bonding.
15. The composition of claim 1, wherein the nanoscale-sized monoazo
laked pigment composition has coloristic properties that are
changeable as a function of particle size of the nanoscale-sized
particles.
16. The composition of claim 15, wherein the coloristic properties
are selected from L*, a*, b*, hue, chroma, and NLSI value.
17. The composition of claim 1, wherein the nanoscale-sized monoazo
laked pigment composition has enhanced chroma as compared to a
similar organic monoazo laked pigment not having the sterically
bulky stabilizer compound and not being of nanoscale-size.
18. The composition of claim 1, wherein when the nanoscale pigment
particle composition is dispersed in a poly(vinyl butyral-co-vinyl
alcohol-co-vinyl acetate) polymer binder, a coating formed from the
dispersion has a hue angle measured within a range spanning from
about 345.degree. to about 0.degree. on a 2-dimensional b* a*
magenta color gamut space.
19. The composition of claim 1, wherein when the nanoscale pigment
particle composition is dispersed in a poly(vinyl butyral-co-vinyl
alcohol-co-vinyl acetate) polymer binder, the pigment exhibits a
NLSI value of from about 0.01 to about 3.
20. A process for preparing nanoscale-sized monoazo laked pigment
particles, comprising: preparing a first reaction mixture
comprising: (a) a diazonium salt having at least one functional
moiety as a first precursor to the laked pigment and (b) a liquid
medium containing diazotizing agents; and preparing a second
reaction mixture comprising: (a) a coupling agent having at least
one functional moiety as a second precursor to the laked pigment
and (b) a sterically bulky stabilizer compound having one or more
functional groups that associate non-covalently with the coupling
agent; and (c) a liquid medium combining the first reaction mixture
into the second reaction mixture to form a solution and effecting a
direct coupling reaction which forms a monoazo laked pigment
composition wherein the functional moiety associates non-covalently
with the functional group and having nanoscale particle size.
21. The process of claim 20, wherein the second reaction mixture
further comprises one or more additives selected from the group
consisting of inorganic and organic buffers, alkaline bases, and
acids.
22. The process of claim 20, wherein the combining is conducted at
ambient temperature with high-speed stirring.
23. A process for preparing nanoscale monoazo laked pigment
particles, comprising: providing a monoazo precursor dye to the
monoazo laked pigment that has at least one functional moiety;
subjecting the monoazo precursor dye to an ion exchange reaction
with a metal cation salt in the presence of a sterically bulky
stabilizer compound having one or more functional groups; and
precipitating the monoazo laked pigment as nanoscale particles,
wherein the functional moiety of the pigment associates
non-covalently with the functional group of the stabilizer and
having nanoscale particle size.
24. An ink composition comprising: a carrier, and a colorant
comprising a nanoscale pigment particle composition according to
claim 1.
25. (canceled)
26. The ink composition of claim 24, wherein the carrier is present
in an amount of about 50 to about 99.9 weight%, and said colorant
is present in an amount of about 0.1 to about 50 weight% by weight
of the ink.
27. The ink composition of claim 24, wherein the carrier comprises
one or more organic compounds that are solid at room temperature
but becomes liquid at a printer operating temperature for ejecting
the ink composition onto a print surface.
28. The ink composition of claim 24, wherein the carrier is
selected from the group consisting of amides, isocyanate-derived
resins and waxes, paraffins, microcrystalline waxes, polyethylene
waxes, ester waxes, amide waxes, fatty acids, fatty alcohols, fatty
amides, sulfonamide materials, resinous materials made from
different natural sources, and synthetic resins, oligomers,
polymers and copolymers, and mixtures thereof.
29. The ink composition of claim 24, wherein the carrier comprises
a curable material selected from the group consisting of radiation
curable monomers, radiation curable oligomers, radiation curable
polymers, and mixtures thereof, that is liquid at room
temperature.
30. The ink composition of claim 24, wherein the ink composition is
selected from the group consisting of solid ink compositions, phase
change ink compositions, curable ink compositions, aqueous ink
compositions, and non-aqueous ink compositions.
31. The ink composition of claim 24, further comprising at least
one additive selected from the group consisting of surfactants,
light stabilizers, UV absorbers, optical brighteners, thixotropic
agents, dewetting agents, slip agents, foaming agents, antifoaming
agents, flow agents, oils, plasticizers, binders, electrically
conductive agents, fungicides, bactericides, organic and inorganic
filler particles, leveling agents, opacifiers, antistatic agents,
dispersants, and mixtures thereof.
32. The ink composition of claim 24, where the colorant consists of
said nanoscale pigment particle composition, and said nanoscale
pigment particle composition is the only colorant present in the
ink composition.
33. The ink composition of claim 24, where the colorant comprises
said nanoscale pigment particle composition and at least one other
colorant material.
34. The composition of claim 1, wherein the sterically bulky
stabilizer is selected from the group consisting of the following
compounds: ##STR00028## wherein Z is H, a metal cation, or an
organic cation; ##STR00029## wherein Z is H, a metal cation, or an
organic cation, and m+n>1; ##STR00030## wherein Z is H, a metal
cation, or an organic cation, and m+n>1 per branch; ##STR00031##
wherein Z is H, a metal cation, or an organic cation, and
n.gtoreq.1; ##STR00032## wherein Z is H, a metal cation, or an
organic cation, and m.gtoreq.1; and ##STR00033## wherein Z is H, a
metal cation, or an organic cation, and n.gtoreq.1.
35. The composition of claim 4, wherein the diazo component is a
compound of Formula (2) ##STR00034## where R.sub.1, R.sub.2, and
R.sub.3 independently represent H, a straight or branched alkyl
group of from about 1 to about 10 carbon atoms, halogen, NH.sub.2,
NO.sub.2, CO.sub.2H, or CH.sub.2CH.sub.3; and FM represents
SO.sub.3H, --C(.dbd.O)-NH-Aryl-SO.sub.3 (where the aryl group can
be unsubstituted or substituted with either halogens or alkyl
groups having from about 1 to about 10 carbons), CO.sub.2H,
halogen, NH.sub.2, or --C(.dbd.O)-NH.sub.2, or is a compound of
Formula (3): ##STR00035##
36. The composition of claim 35, wherein the diazo component is
selected from the group consisting of the following compounds of
Formula (2) wherein: FM is SO.sub.3H, R.sub.1 is CH.sub.3, R.sub.2
is H, and R.sub.3 is NH.sub.2, FM is SO.sub.3H, R.sub.1 is
CH.sub.3, R.sub.2 is Cl, and R.sub.3 is NH.sub.2, FM is SO.sub.3H,
R.sub.1 is Cl, R.sub.2 is CH.sub.3, and R.sub.3 is NH.sub.2, FM is
SO.sub.3H, R.sub.1 is Cl, R.sub.2 is CO.sub.2H, and R.sub.3 is
NH.sub.2, FM is SO.sub.3H, R.sub.1 is Cl, R.sub.2 is
CH.sub.2CH.sub.3, and R.sub.3 is NH.sub.2, FM is SO.sub.3H, R.sub.1
is Cl, R.sub.2 is Cl, and R.sub.3 is NH.sub.2, FM is SO.sub.3H,
R.sub.1 is H, R.sub.2 is NH.sub.2, and R.sub.3 is H, FM is
SO.sub.3H, R.sub.1 is H, R.sub.2 is NH.sub.2, and R.sub.3 is
CH.sub.3, FM is SO.sub.3H, R.sub.1 is NH.sub.2, R.sub.2 is H, and
R.sub.3 is Cl, FM is SO.sub.3H, R.sub.1 is H, R.sub.2 is H, and
R.sub.3 is NH.sub.2, FM is SO.sub.3H, R.sub.1 is H, R.sub.2 is
NH.sub.2, and R.sub.3 is H, FM is SO.sub.3H, R.sub.1 is NO.sub.2,
R.sub.2 is NH.sub.2, and R.sub.3 is H, FM is
--C(.dbd.O)-NH-Phenyl-SO.sub.3, R.sub.1 is NH.sub.2, R.sub.2 is
CH.sub.3, and R.sub.3 is H, FM is CO.sub.2H, R.sub.1 is H, R.sub.2
is H, and R.sub.3 is NH.sub.2, FM is Cl, R.sub.1 is H, R.sub.2 is
H, and R.sub.3 is NH.sub.2, FM is NH.sub.2, R.sub.1 is CH.sub.3,
R.sub.2 is H, and R.sub.3 is H, FM is NH.sub.2, R.sub.1 is H,
R.sub.2 is CH.sub.3, and R.sub.3 is H, FM is --C(.dbd.O)NH.sub.2,
R.sub.1 is NH.sub.2, R.sub.2 is CH.sub.3, and R.sub.3 is H, FM is
--C(.dbd.O)NH.sub.2, R.sub.1 is H, R.sub.2 is NH.sub.2, and R.sub.3
is H, and FM is NH.sub.2, R.sub.1 is H, R.sub.2 is H, and R.sub.3
is H.
37. The composition of claim 4, wherein the coupling component is
selected from the group consisting of compounds of Formulas
(4)-(8), wherein * denotes a point of coupling or attachment to the
azo or hydrazone group: ##STR00036## where FM represents H,
CO.sub.2H, SO.sub.3H, --C(.dbd.O)-NH-Aryl-SO.sub.3 where the aryl
group can be unsubstituted or substituted with either halogens, or
alkyl groups having from about 1 to about 10 carbons, CO.sub.2H,
halogen, NH.sub.2, --C(.dbd.O)-NH.sub.2, substituted benzamides of
the formula: ##STR00037## wherein groups R.sub.2' R.sub.3',
R.sub.4' , and R.sub.5' can independently be H, alkyl groups having
from about 1 to 10 carbons, alkoxyl groups, hydroxyl or halogens,
or nitro NO.sub.2; or benzimidazolone amides of the formula:
##STR00038## where FM represents SO.sub.3H, CO.sub.2H, or
--C(.dbd.O)-NH-Aryl-SO.sub.3 where the aryl group can be
unsubstituted or substituted with either halogens, or alkyl groups
having from about 1 to about 10 carbons, CO.sub.2H, halogens,
NH.sub.2, or --C(.dbd.O)-NH.sub.2 groups, and R.sub.3 and R.sub.4
independently represent H, or SO.sub.3H; ##STR00039## where FM
represents SO.sub.3H, CO.sub.2H, or --C(.dbd.O)-NH-Aryl-SO.sub.3
where the aryl group can be unsubstituted or substituted with
either halogens, or alkyl groups having from about 1 to about 10
carbons, CO.sub.2H, halogens, NH.sub.2, or --C(.dbd.O)-NH.sub.2;
and R.sub.1, R.sub.2, R.sub.3 and R.sub.4 independently represent
H, SO.sub.3H, or --C(.dbd.O)-NH-Phenyl; ##STR00040## where G
represents CO.sub.2H, straight or branched alkyl having from 1 to
about 10 carbons atoms; and R.sub.1, R.sub.2, R.sub.3 and R.sub.4
independently represent H, halogens, SO.sub.3H, nitro (NO.sub.2) or
alkoxyl groups; and ##STR00041## where R.sub.1' represents a
straight or branched alkyl group having from 1 to about 10 carbon
atoms, R2' represents ##STR00042## where each of R.sub.a, R.sub.b,
and R.sub.c independently represents H, a straight or branched
alkyl group having from 1 to about 10 carbon atoms, OCH.sub.3, or
halogens.
Description
TECHNICAL FIELD
[0001] This disclosure is generally directed to nanoscale pigment
particle compositions, and methods for producing such nanoscale
pigment particle compositions, as well as to uses of such
compositions, for example, in ink compositions. More specifically,
this disclosure is directed to organic mono-azo laked nanoscale
pigments. Such particles are useful, for example, as nanoscopic
colorants for such compositions as inks, toners and the like.
CROSS-REFERENCE TO RELATED APPLICATIONS
[0002] Disclosed in commonly assigned U.S. patent application Ser.
No. ______ to Maria Birau et al. filed concurrently herewith
(Attorney Docket Number 132754) is a nanoscale pigment particle
composition, comprising: a quinacridone pigment including at least
one functional moiety, and a sterically bulky stabilizer compound
including at least one functional group, wherein the functional
moiety associates non-covalently with the functional group; and the
presence of the associated stabilizer limits the extent of particle
growth and aggregation, to afford nanoscale-sized particles. Also
disclosed is a process for preparing nanoscale quinacridone pigment
particles, comprising: preparing a first solution comprising: (a) a
crude quinacridone pigment including at least one functional moiety
and (b) a liquid medium; preparing a second solution comprising:
(a) a sterically bulky stabilizer compound having one or more
functional groups that associate non-covalently with the functional
moiety, and (b) a liquid medium; combining the first reaction
mixture into the second reaction mixture to form a third solution
and effecting a direct coupling reaction which forms a quinacridone
pigment composition wherein the functional moiety associates
non-covalently with the functional group and having nanoscale
particle size. Still further is disclosed a process for preparing
nanoscale quinacridone pigment particles, comprising: preparing a
first solution comprising a quinacridone pigment including at least
one functional moiety in an acid; preparing a second solution
comprising an organic medium and a sterically bulky stabilizer
compound having one or more functional groups that associate
non-covalently with the functional moiety of the pigment; treating
the second solution containing with the first solution; and
precipitating quinacridone pigment particles from the first
solution, wherein the functional moiety associates non-covalently
with the functional group and the quinacridone pigment particles
have a nanoscale particle size.
[0003] The entire disclosure of the above-mentioned application is
totally incorporated herein by reference.
BACKGROUND
[0004] Pigments are a class of colorants useful in a variety of
applications such as, for example, paints, plastics and inks. Dyes
have typically been the colorants of choice for inkjet printing
inks because they are readily soluble colorants which enable
jetting of the ink. Dyes have also offered superior and brilliant
color quality with an expansive color gamut for inks, when compared
with conventional pigments. However, since dyes are molecularly
dissolved in the ink vehicle, they are often susceptible to
unwanted interactions that lead to poor ink performance, for
example photooxidation from light (will lead to poor
lightfastness), dye diffusion from the ink into paper or other
substrates (will lead to poor image quality and showthrough), and
the ability for the dye to leach into another solvent that makes
contact with the image (will lead to poor water/solventfastness).
In certain situations, pigments are the better alternative as
colorants for inkjet printing inks since they are insoluble and
cannot be molecularly dissolved within the ink matrix, and
therefore do not experience colorant diffusion. Pigments are also
significantly less expensive than dyes, and so are attractive
colorants for use in all printing inks.
[0005] Key issues with using pigments for inkjet inks are their
large particle sizes and wide particle size distribution, the
combination of which can pose critical problems with reliable
jetting of the ink (i.e. inkjet nozzles are easily blocked).
Pigments are rarely obtained in the form of single crystal
particles, but rather as large aggregates of crystals and with wide
distribution of aggregate sizes. The color characteristics of the
pigment aggregate can vary widely depending on the aggregate size
and crystal morphology. Thus, there is a need addressed by
embodiments of the present invention, for smaller pigment particles
that minimize or avoid the problems associated with conventional
pigment particles. The present nanosized pigment particles are
useful in for example paints, coatings and inks (e.g., inkjet
printing inks) and other compositions where pigments can be used
such as plastics, optoelectronic imaging components, photographic
components and cosmetics.
[0006] A printing ink is generally formulated according to strict
performance requirements demanded by its intended market
application and desired properties. Whether formulated for office
printing or for production printing, a particular ink is expected
to produce images that are robust and durable under stress
conditions, such as exposure to abrasive or sharp objects or
actions that produce a crease defect in the image (such as folding
or scratching the imaged paper). For example, in a typical design
of a piezoelectric ink jet device, the image is applied by jetting
appropriately colored inks during four to six rotations
(incremental movements) of a substrate (an image receiving member
or intermediate transfer member) with respect to the ink jetting
head, i.e., there is a small translation of the printhead with
respect to the substrate in between each rotation. This approach
simplifies the printhead design, and the small movements ensure
good droplet registration. At the jet operating temperature,
droplets of liquid ink are ejected from the printing device and,
when the ink droplets contact the surface of the recording
substrate, either directly or via an intermediate heated transfer
belt or drum, they quickly solidify to form a predetermined pattern
of solidified ink drops.
[0007] Hot melt inks typically used with ink jet printers have a
wax based ink vehicle, e.g., a crystalline wax. Such solid ink jet
inks provide vivid color images. In typical systems, these
crystalline wax inks partially cool on an intermediate transfer
member and are then pressed into the image receiving medium such as
paper. Transfuse spreads the image droplet, providing a richer
color and lower pile height. The low flow of the solid ink also
prevents show through on the paper. However, the use of crystalline
waxes places limitations for printing, such as the brittleness of
these materials which may reduce the ink's robustness properties
that are required to provide abrasion-resistant images.
Consequently, increased mechanical robustness is desired.
[0008] The following documents provide background information:
[0009] Hideki Maeta et al., "New Synthetic Method of Organic
Pigment Nano Particle by Micro Reactor System," in an abstract
available on the internet at
http://aiche.confex.com/aiche/s06/preliminaryprogram/abstract.sub.--40072-
.htm, describes a new synthetic method of an organic pigment nano
particle was realized by micro reactor. A flowing solution of an
organic pigment, which dissolved in an alkaline aqueous organic
solvent, mixed with a precipitation medium in a micro channel. Two
types of micro reactor can be applied efficiently on this build-up
procedure without blockage of the channel. The clear dispersion was
extremely stable and had narrow size distribution, which were the
features, difficult to realize by the conventional pulverizing
method (breakdown procedure). These results proved the
effectiveness of this process on micro reactor system.
[0010] U.S. Patent Application Publication No. 2005/0109240
describes a method of producing a fine particle of an organic
pigment, containing the steps of: flowing a solution of an organic
pigment dissolved in an alkaline or acidic aqueous medium, through
a channel which provides a laminar flow; and changing a pH of the
solution in the course of the laminar flow.
[0011] WO 2006/132443 A1 describes a method of producing organic
pigment fine particles by allowing two or more solutions, at least
one of which is an organic pigment solution in which an organic
pigment is dissolved, to flow through a microchannel, the organic
pigment solution flows through the microchannel in a non-laminar
state. Accordingly, the contact area of solutions per unit time can
be increased and the length of diffusion mixing can be shortened,
and thus instantaneous mixing of solutions becomes possible. As a
result, nanometer-scale monodisperse organic pigment fine particles
can be produced in a stable manner.
[0012] K. Balakrishnan et al., "Effect of Side-Chain Substituents
on Self-Assembly of Perylene Diimide Molecules: Morphology
Control," J. Am. Chem. Soc., vol. 128, p. 7390-98 (2006) describes
the use of covalently-linked aliphatic side-chain substituents that
were functionalized onto perylene diimide molecules so as to
modulate the self-assembly of molecules and generate distinct
nanoparticle morphologies (nano-belts to nano-spheres), which in
turn impacted the electronic properties of the material. The
side-chain substituents studied were linear dodecyl chain, and a
long branched nonyldecyl chain, the latter substituent leading to
the more compact, spherical nanoparticle.
[0013] WO 2006/011467 discloses a pigment, which is used, for
example, in color image display devices and can form a blue pixel
capable of providing a high level of bright saturation,
particularly a refined pigment, which has bright hue and is
excellent in pigment properties such as lightfastness, solvent
resistance and heat resistance, and a process for producing the
same, a pigment dispersion using the pigment, and an ink for a
color filter. The pigment is a subphthalocyanine pigment that is
prepared by converting subphthalocyanine of the specified formula,
to a pigment, has diffraction peaks at least at diffraction angles
(2.theta.) 7.0.degree., 12.3.degree., 20.4.degree. and 23.4.degree.
in X-ray diffraction and an average particle diameter of 120 to 20
nm.
[0014] U.S. Patent Application Publication No. 2006/0063873
discloses a process for preparing nano water paint comprising the
steps of: A. modifying the chemical property on the surface of nano
particles by hydroxylation for forming hydroxyl groups at high
density on the surface of the nano particles; B. forming
self-assembly monolayers of low surface energy compounds on the
nano particles by substituting the self-assembly monolayers for the
hydroxyl groups on the nano particles for disintegrating the
clusters of nano particles and for forming the self-assembly
monolayers homogeneously on the surface of the nano particles; and
C. blending or mixing the nano particles having self-assembly
monolayers formed thereon with organic paint to form nano water
paint.
[0015] WO 2006/024103 discloses nanopigments prepared from organic
IR dye and Na-bentonite with CEC of 95 mmole Na per 100 g of
bentonite, at room temperature, by dissolving the Na-bentonite in
water and mixing for 2 hours, and mixing in the dye, dissolved in
ethanol, for 18 hours. The precipitate is filtered, washed three
times with water/ethanol mixture, dried at 105.degree. C. for 10
hours, and milled in a kitchen miller for 2 mins. 0.3 parts of the
nanopigments were mixed to 100 parts of pulverized SPG resin and
processed in an extruder with a die temperature of 190.degree. C.
to form transparent, faintly green or grey colored extrudates which
were used to press film of 0.4 mm thickness at 160.degree. C. The
films were used to prepare IR-active laminated glass. Near infrared
absorption spectra of the glass structures were obtained in a
Perkin-Elmer Spectrophotometer.
[0016] WO 2006/005521 discloses a photoprotective composition
comprising, in a physiologically acceptable medium: a) at least one
aqueous phase, b) at least hydrophilic metal oxide nanoparticles,
c) at least one vinylpyrrolidone homopolymer. The reference also
discloses the use of at least one vinylpyrrolidone homopolymer in a
photoprotective composition comprising at least one aqueous phase
and at least hydrophilic metal oxide nanoparticles for the purpose
of reducing the whitening and/or of improving the stability of the
said composition (dispersibility of the nanoparticles in the
aqueous phase).
[0017] WO 2006/005536 discloses a method for producing
nanoparticles, in particular, pigment particles. Said method
consists of the following steps: (i) a raw substance is passed into
the gas phase, (ii) particles are produced by cooling or reacting
the gaseous raw substance and (iii) an electrical charge is applied
to the particles during the production of the particles in step
(ii), in a device for producing nanoparticles. The disclosure
further relates to a device for producing nanoparticles, comprising
a supply line, which is used to transport the gas flow into the
device, a particle producing and charging area in order to produce
and charge nanoparticles at essentially the same time, and an
evacuation line which is used to transport the charged
nanoparticles from the particle producing and charging area.
[0018] Japanese Patent Application Publication No. JP 2005238342 A2
discloses irradiating ultrashort pulsed laser to organic bulk
crystals dispersed in poor solvents to induce ablation by nonlinear
absorption for crushing the crystals and recovering the resulting
dispersions of scattered particles. The particles with average size
approximately 10 nm are obtained without dispersants or grinding
agents for contamination prevention and are suitable for pigments,
pharmaceuticals, etc.
[0019] U.S. Patent Application Publication No. 2003/0199608
discloses a functional material comprising fine coloring particles
having an average primary particle diameter of 1 to 50 nm in a
dried state, and having a BET specific surface area value of 30 to
500 m.sup.2/g and a light transmittance of not less than 80%. The
functional material composed of fine coloring particles, exhibits
not only an excellent transparency but also a high tinting strength
and a clear hue.
[0020] U.S. Pat. No. 6,837,918 discloses a process and apparatus
that collects pigment nanoparticles by forming a vapor of a pigment
that is solid at room temperature, the vapor of the pigment being
provided in an inert gaseous carrying medium. At least some of the
pigment is solidified within the gaseous stream. The gaseous stream
and pigment material is moved in a gaseous carrying environment
into or through a dry mechanical pumping system. While the
particles are within the dry mechanical pumping system or after the
nanoparticles have moved through the dry pumping system, the
pigment material and nanoparticles are contacted with an inert
liquid collecting medium.
[0021] U.S. Pat. No. 6,537,364 discloses a process for the fine
division of pigments which comprises dissolving coarsely
crystalline crude pigments in a solvent and precipitating them with
a liquid precipitation medium by spraying the pigment solution and
the precipitation medium through nozzles to a point of conjoint
collision in a reactor chamber enclosed by a housing in a microjet
reactor, a gas or an evaporating liquid being passed into the
reactor chamber through an opening in the housing for the purpose
of maintaining a gas atmosphere in the reactor chamber, and the
resulting pigment suspension and the gas or the evaporated liquid
being removed from the reactor through a further opening in the
housing by means of overpressure on the gas entry side or
underpressure on the product and gas exit side.
[0022] U.S. Pat. No. 5,679,138 discloses a process for making ink
jet inks, comprising the steps of: (A) providing an organic pigment
dispersion containing a pigment, a carrier for the pigment and a
dispersant; (B) mixing the pigment dispersion with rigid milling
media having an average particle size less than 100 .mu.m; (C)
introducing the mixture of step (B) into a high speed mill; (D)
milling the mixture from step (C) until a pigment particle size
distribution is obtained wherein 90% by weight of the pigment
particles have a size less than 100 nanometers (nm); (E) separating
the milling media from the mixture milled in step (D); and (F)
diluting the mixture from step (E) to obtain an ink jet ink having
a pigment concentration suitable for ink jet printers.
[0023] Japanese Patent Application Publications Nos. JP 2007023168
and JP 2007023169 discloses providing a pigment dispersion compound
excellent in dispersibility and flowability used for the color
filter which has high contrast and weatherability. The solution of
the organic material, for example, the organic pigment, dissolved
in a good solvent under the existence of alkali soluble binder (A)
which has an acidic group, and a poor solvent which makes the phase
change to the solvent are mixed. The pigment nanoparticles
dispersed compound re-decentralized in the organic solvent
containing the alkali soluble binder (B) which concentrates the
organic pigment nanoparticles which formed the organic pigment as
the particles of particle size less than 1 .mu.m, and further has
the acidic group.
[0024] Kazuyuki Hayashi et al., "Uniformed nano-downsizing of
organic pigments through core-shell structuring," Journal of
Materials Chemistry, 17(6), 527-530 (2007) discloses that
mechanical dry milling of organic pigments in the presence of
mono-dispersed silica nanoparticles gave core-shell hybrid pigments
with uniform size and shape reflecting those of the inorganic
particles, in striking contrast to conventional milling as a
breakdown process, which results in limited size reduction and wide
size distribution.
[0025] U.S. Patent Application Publication No. 2007/0012221
describes a method of producing an organic pigment dispersion
liquid, which has the steps of: providing an alkaline or acidic
solution with an organic pigment dissolved therein and an aqueous
medium, wherein a polymerizable compound is contained in at least
one of the organic pigment solution and the aqueous medium; mixing
the organic pigment solution and the aqueous medium; and thereby
forming the pigment as fine particles; then polymerizing the
polymerizable compound to form a polymer immobile from the pigment
fine particles.
[0026] The appropriate components and process aspects of each of
the foregoing may be selected for the present disclosure in
embodiments thereof, and the entire disclosure of the
above-mentioned references are totally incorporated herein by
reference.
SUMMARY
[0027] The present disclosure addresses these and other needs, by
providing nanoscale pigment particle compositions, and methods for
producing such nanoscale pigment particle compositions.
[0028] In an embodiment, the present disclosure provides a
nanoscale pigment particle composition, comprising:
[0029] an organic monoazo laked pigment including at least one
functional moiety, and
[0030] a sterically bulky stabilizer compound including at least
one functional group,
[0031] wherein the functional moiety associates non-covalently with
the functional group; and
[0032] the presence of the associated stabilizer limits the extent
of particle growth and aggregation, to afford nanoscale-sized
pigment particles.
[0033] In another embodiment, the present disclosure provides a
process for preparing nanoscale-sized monoazo laked pigment
particles, comprising:
[0034] preparing a first reaction mixture comprising: (a) a
diazonium salt including at least one functional moiety as a first
precursor to the laked pigment and (b) a liquid medium containing
diazotizing agents; and
[0035] preparing a second reaction mixture comprising: (a) a
coupling agent including at least one functional moiety as a second
precursor to the laked pigment and (b) a sterically bulky
stabilizer compound having one or more functional groups that
associate non-covalently with the coupling agent; and (c) a liquid
medium
[0036] combining the first reaction mixture into the second
reaction mixture to form a third solution and
[0037] effecting a direct coupling reaction which forms a monoazo
laked pigment composition wherein the functional moiety associates
non-covalently with the functional group and having nanoscale
particle size.
[0038] In still another embodiment, the disclosure provides ink
compositions, such as an aqueous or non-aqueous ink composition, an
ink jet ink composition, a solid phase change ink composition, a
radiation-curable ink composition, or the like, generally
comprising at least a carrier and the above nanoscale pigment
particle composition.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] FIG. 1 shows a two-dimensional b*a*Gamut for pigmented
coatings according to embodiments.
[0040] FIG. 2 shows a relationship between hue angle and normalized
light scatter index (NLSI) for pigmented coatings prepared
according to embodiments.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0041] Embodiments of the present disclosure provide nanoscale
pigment particle compositions, and methods for producing such
nanoscale pigment particle compositions. The nanoscale pigment
particle compositions generally comprise an organic monoazo laked
pigment including at least one functional moiety that associates
non-covalently with a functional group from a sterically bulky
stabilizer compound. The presence of the associated stabilizer
limits the extent of particle growth and aggregation, to afford
nanoscale particles.
[0042] Organic monoazo "laked" pigments are the insoluble metal
salt colorants of monoazo colorants which can include monoazo dyes
or pigments, and in certain geographic regions these pigments have
been referred to as either "toners" or "lakes". The process of ion
complexation with a metal salt, or "laking" process, provides
decreased solubility of the non-laked non-ionic monoazo pigment,
which can enhance the migration resistance and thermal stability
properties of a monoazo pigment, and thereby enable the
applications of such pigments for extreme performance, such as
colorizing plastics and heat-stable paints for outdoor use. The
monoazo laked pigments are structurally comprised of a diazo
component (DC) and a coupling component (CC) that are linked
together with a single azo (N.dbd.N) functional group as in the
figure below, wherein either or both of the DC and CC contain one
or more ionic functional moieties, such as sulfonate or carboxylate
anions or the like, and the structure of the ionic pigment also
comprises a counteraction, which is typically a metal
counteraction, (M.sup.n+).
##STR00001##
[0043] As an example, the organic pigment PR 57:1 ("PR" refers to
Pigment Red) has two functional moieties of two different types, a
sulfonate anion group (SO.sub.3.sup.-M.sup.n+) and carboxylate
anion group (CO.sub.2.sup.-M.sup.n+), wherein M.sup.n+ represents a
countercation typically chosen from Group 2 alkaline earth metals
such as Ca.sup.2+, but other monoazo laked pigment compositions
exist that can have a metal counteraction from either Group 2,
Group 3, Group 1, the d-block transition metal cations, and others.
Further, the azo group in the compounds can generally assume two
different tautomer forms, such as the "azo" form which has the
(N.dbd.N) linkage, and the "hydrazone" form which has the
(C.dbd.N--NH--) linkage that is stabilized by an intramolecular
hydrogen bond, where the hydrazone tautomer is known to be the
preferred structural form for PR 57:1.
##STR00002##
Due to the structural nature of monoazo laked pigments being ionic
salts, it is possible to have compounds that associate
non-covalently with the pigment, such as organic or inorganic ionic
compounds that can associate with the metal cation through ionic or
coordination-type bonding. Such ionic compounds are included in a
group of compounds which herein are referred to as "stabilizers",
and that function to reduce the surface tension of the pigment
particle and neutralize attractive forces between two or more
pigment particles or structures, thereby stabilizing the chemical
and physical structure of the pigment.
[0044] The "average" particle size, which is typically represented
as d.sub.50, is defined as the median particle size value at the
50th percentile of the particle size distribution, wherein 50% of
the particles in the distribution are greater than the d.sub.50
particle size value and the other 50% of the particles in the
distribution are less than the d.sub.50 value. Average particle
size can be measured by methods that use light scattering
technology to infer particle size, such as Dynamic Light
Scattering. The term "particle diameter" as used herein refers to
the length of the pigment particle as derived from images of the
particles generated by Transmission Electron Microscopy (TEM). The
term "nanosized", "nanoscale", or "nanosized pigment particles"
refers to for instance, an average particle size, d.sub.50, or an
average particle diameter of less than about 150 nm, such as of
about 1 nm to about 100 nm, or about 10 nm to about 80 nm.
[0045] The term "complementary" as used in complementary functional
moiety of the stabilizer indicates that the complementary
functional moiety is capable of noncovalent chemical bonding with
the functional moiety of the organic pigment and/or the functional
moiety of the pigment precursor.
[0046] The term "precursor" as used in "precursor to the organic
pigment" can be any chemical substance that is an advanced
intermediate in the total synthesis of a compound (such as the
organic pigment). In embodiments, the organic pigment and the
precursor to the organic pigment may or may not have the same
functional moiety. In embodiments, the precursor to the organic
pigment may or may not be a colored compound. In still other
embodiments, the precursor and the organic pigment can have
different functional moieties. In embodiments, where the organic
pigment and the precursor have a structural feature or
characteristic in common, the phrase "organic pigment/pigment
precursor" is used for convenience rather than repeating the same
discussion for each of the organic pigment and the pigment
precursor.
[0047] The functional moiety of the organic pigment/precursor can
be any suitable moiety capable of non-covalent bonding with the
complementary functional moiety of the stabilizer. Illustrative
functional moieties of the organic pigment/precursor include (but
are not limited to) the following: sulfonate/sulfonic acid,
(thio)carboxylate/(thio)carboxylic acid, phosphonate/phosphonic
acid, ammonium and substituted ammonium salts, phosphonium and
substituted phosphonium salts, substituted carbonium salts,
substituted arylium salts, alkyl/aryl(thio)carboxylate esters,
thiol esters, primary or secondary amides, primary or secondary
amines, hydroxyl, ketone, aldehyde, oxime, hydroxylamino, enamines
(or Schiff base), porphyrins, (phthalo)cyanines, urethane or
carbamate, substituted ureas, guanidines and guanidinium salts,
pyridine and pyridinium salts, imidazolium and (benz)imidazolium
salts, (benz)imidazolones, pyrrolo, pyrimidine and pyrimidinium
salts, pyridinone, piperidine and piperidinium salts, piperazine
and piperazinium salts, triazolo, tetraazolo, oxazole, oxazolines
and oxazolinium salts, indoles, indenones, and the like.
[0048] Pigment precursors for making monoazo laked nanopigments
consist of the aniline precursor, which leads to the diazonium
component (denoted "DC"), a nucleophilic basic coupling component
(denoted "CC"), and a metal cation salt (denoted "M").
Representative examples of the aniline precursor (DC) of laked
monoazo pigments that have the functional moiety capable of
non-covalent bonding with a complementary functional group on the
stabilizer, include (but are not limited to) the following
structures in Table 1 (with the functional moiety "FM" encircled,
if applicable):
TABLE-US-00001 TABLE 1 Examples of types of aniline precursors
(diazo component, DC) that are used to make monoazo laked pigments.
##STR00003## DC label FM R.sub.1 R.sub.2 R.sub.3 DC1 SO.sub.3H
CH.sub.3 H NH.sub.2 DC2 SO.sub.3H CH.sub.3 Cl NH.sub.2 DC3
SO.sub.3H Cl CH.sub.3 NH.sub.2 DC4 SO.sub.3H Cl CO.sub.2H NH.sub.2
DC5 SO.sub.3H Cl CH.sub.2CH.sub.3 NH.sub.2 DC6 SO.sub.3H Cl Cl
NH.sub.2 DC7 SO.sub.3H H NH.sub.2 H DC8 SO.sub.3H H NH.sub.2
CH.sub.3 DC9 SO.sub.3H NH.sub.2 H Cl DC10 SO.sub.3H H H NH.sub.2
DC11 SO.sub.3H H NH.sub.2 H DC12 SO.sub.3H NO.sub.2 NH.sub.2 H DC13
##STR00004## NH.sub.2 CH.sub.3 H DC14 CO.sub.2H H H NH.sub.2 DC15
Cl H H NH.sub.2 DC16 NH.sub.2 CH.sub.3 H H DC17 NH.sub.2 H CH.sub.3
H DC18 ##STR00005## NH.sub.2 CH.sub.3 H DC19 ##STR00006## H
NH.sub.2 H DC20 NH.sub.2 H H H DC21 ##STR00007##
[0049] Representative examples of the nucleophilic coupling
component precursor of laked monoazo pigments that have the
functional moiety capable of non-covalent bonding with a
complementary functional group on the stabilizer, include (but are
not limited to) the following structures in Tables 2-6 (with the
functional moiety "FM" encircled, if applicable:
TABLE-US-00002 TABLE 2 Examples of types of coupling component
precursors (CC) based on .beta.-naphthol and derivatives, that are
used to make monoazo laked pigments. ##STR00008## CC Class of
Coupling label Component (CC) FM CC1 .beta.-Naphthol H CC2
.beta.-oxynaphthoic acid CO.sub.2H ("BONA") CC3 Naphthol
ASderivatives ##STR00009## CC6 Benzimidazolone ##STR00010## * =
point of coupling to diazo component
TABLE-US-00003 TABLE 3 Examples of types of coupling component
precursors (CC) based on naphthalene sulfonic acid derivatives,
that are used to make monoazo laked pigments. ##STR00011## Class of
Coupling CC label Component (CC) FM R.sub.3 R.sub.4 CC4a
Naphthalene Sulfonic SO.sub.3H H H Acid derivatives CC4b
Naphthalene Sulfonic SO.sub.3H SO.sub.3H H Acid derivatives * =
point of coupling to diazo component
TABLE-US-00004 TABLE 4 Examples of types of coupling component
precursors (CC) based on naphthalene sulfonic acid derivatives,
that are used to make monoazo laked pigments. ##STR00012## Class of
Coupling CC label Component (CC) FM R.sub.1 R.sub.2 R.sub.3 R.sub.4
CC5 Naphthalene SulfonicAcid derivatives SO.sub.3H ##STR00013## H H
SO.sub.3H * = point of coupling to diazo component
TABLE-US-00005 TABLE 5 Examples of types of coupling component
precursors (CC) based on pyrazolone derivatives, that are used to
make laked pigments. ##STR00014## Class of Coupling CC label
Component (CC) G R.sub.1' R.sub.2' R.sub.3' R.sub.4' CC7 Pyrazolone
deriv. CO.sub.2H H H SO.sub.3H H CC8 Pyrazolone deriv. CH.sub.3 H H
SO.sub.3H H CC9 Pyrazolone deriv. CH.sub.3 H SO.sub.3H H H CC10
Pyrazolone deriv. CH.sub.3 Cl H SO.sub.3H Cl * = point of coupling
to diazo component
TABLE-US-00006 TABLE 6 Examples of types of coupling component
precursors (CC) based on acetoacetic arylide derivatives, that are
used to make laked pigments. ##STR00015## Class of Coupling CC
label Component (CC) R.sub.1' R.sub.2' R.sub.a R.sub.b R.sub.c CC11
Acetoacetic arylide CH.sub.3 ##STR00016## H H H CC12 Acetoacetic
arylide CH.sub.3 ##STR00017## CH.sub.3 H H CC13 Acetoacetic arylide
CH.sub.3 ##STR00018## Cl H H CC14 Acetoacetic arylide CH.sub.3
##STR00019## H OCH.sub.3 H CC15 Acetoaceticbenzimidazolone CH.sub.3
##STR00020## -- -- -- * = point of coupling to diazo component
[0050] The organic pigment, and in some embodiments, the organic
pigment precursor, also generally includes a counterion as part of
the overall structure. Such counterions can be, for example, any
suitable counterion including those that are well known in the art.
Such counterions can be, for example, cations or anions of either
metals or non-metals that include N, P, S and the like, or
carbon-based cations or anions. Examples of suitable cations
include ions of Ba, Ca, Cu, Mg, Sr, Li, Na, K, Cs, Mn, Cu, Cr, Fe,
Ti, Ni, Co, Zn, V, B, Al, Ga, and the like.
[0051] Representative examples of monoazo laked pigments comprised
from a selection of diazo component (DC) and coupling component
(CC) and metal cation salt (M) are listed in Table 7, and other
laked pigment structures may arise from other combinations of DC
and CC and metal cation salt (M) that are not shown in Table 7.
TABLE-US-00007 TABLE 7 Examples of monoazo laked pigments.
##STR00021## Color Index # Color Index DC CC Metal Salt (C.I.)
(C.I.) Name Laked Pigment Class precursor precursor M 15500:1 Red
50:1 .beta.-Naphthol Lakes DC14 CC1 1/2 Ba 15510:1 Orange 17
.beta.-Naphthol Lakes DC7 CC1 Ba 15510:2 Orange 17:1
.beta.-Naphthol Lakes DC7 CC1 2/3 Al 15525 Red 68 .beta.-Naphthol
Lakes DC4 CC1 2 Ca 15580 Red 51 .beta.-Naphthol Lakes DC8 CC1 Ba
15585 Red 53 .beta.-Naphthol Lakes DC3 CC1 2 Na 15585:1 Red 53:1
.beta.-Naphthal Lakes DC3 CC1 Ba 15585:3 Red 53:3 .beta.-Naphthol
Lakes DC3 CC1 Sr 15602 Orange 46 .beta.-Naphthol Lakes DC5 CC1 Ba
15630 Red 49 .beta.-Naphthol Lakes DC21 CC1 2 Na 15630:1 Red 49:1
.beta.-Naphthol Lakes DC21 CC1 Ba 15630:2 Red 49:2 .beta.-Naphthol
Lakes DC21 CC1 Ca 15630:3 Red 49:3 .beta.-Naphthol Lakes DC21 CC1
Sr 15800 Red 64 .beta.-oxynaphthoic acid (BONA) Lakes DC20 CC2 1/2
Ba 15800:1 Red 64:1 .beta.-oxynaphthoic acid (BONA) Lakes DC20 CC2
1/2 Ca 15800:2 Brown 5 .beta.-oxynaphthoic acid (BONA) Lakes DC20
CC2 1/2 Cu 15825:2 Red 58:2 .beta.-oxynaphthoic acid (BONA) Lakes
DC9 CC2 Ca 15825:4 Red 58:4 .beta.-oxynaphthoic acid (BONA) Lakes
DC9 CC2 Mn 15850:1 Red 57:1 .beta.-oxynaphthoic acid (BONA) Lakes
DC1 CC2 Ca 15860:1 Red 52:1 .beta.-oxynaphthoic acid (BONA) Lakes
DC3 CC2 Ca 15860:2 Red 52:2 .beta.-oxynaphthoic acid (BONA) Lakes
DC3 CC2 Mn 15865:1 Red 48:1 .beta.-oxynaphthoic acid (BONA) Lakes
DC2 CC2 Ba 15865:2 Red 48:2 .beta.-oxvnaphthoic acid (BONA) Lakes
DC2 CC2 Ca 15865:3 Red 48:3 .beta.-oxynaphthoic acid (BONA) Lakes
DC2 CC2 Sr 15865:4 Red 48:4 .beta.-oxvnaphthoic acid (BONA) Lakes
DC2 CC2 Mn 15865:5 Red 48:5 .beta.-oxynaphthoic acid (BONA) Lakes
DC2 CC2 Mg 15867 Red 200 .beta.-oxynaphthoic acid (BONA) Lakes DC5
CC2 Ca 15880:1 Red 63:1 .beta.-oxynaphthoic acid (BONA) Lakes DC21
CC2 Ca 15880:2 Red 63:2 .beta.-oxynaphthoic acid (BONA) Lakes DC21
CC2 Mn 15892 Red 151 Naphthol AS Lakes DC10 CC3 Ba (R.sub.2' = H,
R.sub.4' = SO.sub.3H) 15910 Red 243 Naphthol AS Lakes DC2 CC3 1/2
Ba (R.sub.2' = OCH.sub.3, R.sub.4' = H) 15915 Red 247 Naphthol AS
Lakes DC13 CC3 Ca (R.sub.2' = H, R.sub.4' = OCH.sub.3) 15985:1
Yellow 104 Naphthalene Sulfonic Acid Lakes DC7 CC4a 2/3 Al 15990
Orange 19 Naphthalene Sulfonic Acid Lakes DC15 CC4a 1/2 Ba 16105
Red 60 Naphthalene Sulfonic Acid Lakes DC14 CC4b 3/2 Ba 18000:1 Red
66 Naphthalene Sulfonic Acid Lakes DC16 CC5 1/2 Ba, Na
[0052] The complementary functional group of the stabilizer can be
one or more of any suitable moiety capable of non-covalent bonding
with the functional moiety of the stabilizer. Illustrative
complementary functional groups on the stabilizer include the
following: sulfonate/sulfonic acid,
(thio)carboxylate/(thio)carboxylic acid, phosphonate/phosphonic
acid, ammonium and substituted ammonium salts, phosphonium and
substituted phosphonium salts, substituted carbonium salts,
substituted arylium salts, alkyl/aryl(thio)carboxylate esters,
thiol esters, primary or secondary amides, primary or secondary
amines, hydroxyl, ketone, aldehyde, oxime, hydroxylamino, enamines
(or Schiff base), porphyrins, (phthalo)cyanines, urethane or
carbamate, substituted ureas, guanidines and guanidinium salts,
pyridine and pyridinium salts, imidazolium and (benz)imidazolium
salts, (benz)imidazolones, pyrrolo, pyrimidine and pyrimidinium
salts, pyridinone, piperidine and piperidinium salts, piperazine
and piperazinium salts, triazolo, tetraazolo, oxazole, oxazolines
and oxazolinium salts, indoles, indenones, and the like.
[0053] The stabilizer can be any compound that has the function of
limiting the extent of pigment particle self-assembly to produce
nanoscale-sized pigment particles. The stabilizer compound should
have a hydrocarbon moiety that provides sufficient steric bulk to
enable the function of the stabilizer to regulate pigment particle
size. The hydrocarbon moiety in embodiments is predominantly
aliphatic, but in other embodiments can also incorporate aromatic
groups, and generally contains at least 6 carbon atoms, such as at
least 12 carbons or at least 16 carbons, and not more than about
100 carbons, but the actual number of carbons can be outside of
these ranges. The hydrocarbon moiety can be either linear, cyclic
or branched, and in embodiments is desirably branched, and may or
may not contain cyclic moieties such as cycloalkyl rings or
aromatic rings. The aliphatic branches are long with at least 2
carbons in each branch, such as at least 6 carbons in each branch,
and not more than about 100 carbons.
[0054] It is understood that the term "steric bulk" is a relative
term, based on comparison with the size of the pigment or pigment
precursor to which it becomes non-covalently associated. In
embodiments, the phrase "steric bulk" refers to the situation when
the hydrocarbon moiety of the stabilizer compound that is
coordinated to the pigment/precursor surface, occupies a
3-dimensional special volume that effectively prevents the approach
or association of other chemical entities (e.g. colorant molecules,
primary pigment particles or small pigment aggregate) toward the
pigment/precursor surface. Thus, the stabilizer should have its
hydrocarbon moiety large enough so that as several stabilizer
molecules become non-covalently associated with the chemical entity
(pigment or precursor), the stabilizer molecules act as surface
barrier agents for the primary pigment particles and effectively
encapsulates them, and thereby limits the growth of the pigment
particles and affording only nanoparticles of the pigment. For
example, for the pigment precursor Lithol Rubine and for the
organic pigment Pigment Red 57:1, the following illustrative groups
on a stabilizer are considered to have adequate "steric bulk" so as
to enable the stabilizer to limit the extent of pigment
self-assembly or aggregation and mainly produce pigment nano-sized
particles:
##STR00022##
[0055] Representative examples of stabilizer compounds that have
both the functional group that non-covalently associates with the
pigment and the sterically bulky hydrocarbon moiety, include (but
are not limited to) the following compounds:
##STR00023## ##STR00024##
[0056] In additional embodiments, other stabilizer compounds having
different structures that those described previously may be used in
addition to sterically bulky stabilizer compounds, to function as
surface active agents (or surfactants) that either prevent or limit
the degree of pigment particle aggregation. Representative examples
of such surface active agents include, but are not limited to,
derivatives of rosin natural products, acrylic-based polymers,
styrene-based copolymers, copolymers of .alpha.-olefins such as
1-hexadecene, 1-octadecene, 1-eicosene, 1-triacontene and the like,
copolymers of vinyl pyridine, vinyl imidazole, and vinyl
pyrrolidinone, polyester copolymers, polyamide copolymers,
copolymers of acetals and acetates such as the copolymer
poly(vinylbutyral)-co-(vinyl alcohol)-co-(vinyl acetate).
[0057] The types of non-covalent chemical bonding that can occur
between the functional moiety of the precursor/pigment and the
complementary functional group of the stabilizer are, for example,
van der Waals' forces, ionic or coordination bonding, hydrogen
bonding, and/or aromatic pi-stacking bonding. In embodiments, the
non-covalent bonding is predominately ionic bonding, but can
include hydrogen bonding and aromatic pi-stacking bonding as
additional or alternative types of non-covalent bonding between the
functional moieties of the stabilizer compounds and the
precursor/pigment.
[0058] The method of making nano-sized particles of the monoazo
laked pigments such as those listed in Table 7 is a process that
involves at least one or more reaction steps. A diazotization
reaction is a key reaction step for synthesis of the monoazo laked
pigment, whereby a suitable aniline precursor (or diazo component
DC, such as those listed in Table 1), is either directly or
indirectly converted first to a diazonium salt using standard
procedures, such as procedures that include treatment with a
diazotizing agent such as nitrous acid HNO.sub.2 (for example,
generated in situ by mixing sodium nitrite with dilute hydrochloric
acid solution) or nitrosyl sulfuric acid (NSA), which is
commercially available or prepared by mixing sodium nitrite in
concentrated sulfuric acid. The resulting acidic mixture of
diazonium salt is either a solution or a suspension and in
embodiments is kept cold, to which can optionally be added an
aqueous solution of the metal salt (M.sup.n+) that will define the
specific composition of the desired monoazo laked pigment product,
such as those listed in Table 7. The diazonium salt solution or
suspension is then transferred into a solution or suspension of a
suitable coupling component (CC, such as those listed in Tables
2-6) that can be either acidic or basic in pH and generally contain
additional buffers and surface active agents, including the
sterically bulky stabilizer compounds such as those described
earlier, to produce a solid colorant material suspended as an
aqueous slurry.
[0059] The solid colorant material may be the desired monoazo laked
pigment product, or it may be an advanced synthetic intermediate
for making the monoazo laked pigment product. In the case of the
latter, a two-step process is required for preparing the nanosized
particles of monoazo laked pigment, whereby the second step
involves rendering the advanced synthetic intermediate of the first
step above (the pigment precursor) into homogeneous liquid solution
by treatment with either strong acid or alkaline base, treating
this solution with one or more surface active agents in addition to
sterically bulky stabilizer compounds, as described earlier,
followed lastly by treatment with the required metal salt solution
to provide the required laked pigment composition as a solid
precipitate, said metal salt solution effectively functioning as a
pigment precipitating agent. Several chemical as well as physical
processing factors can affect the final particle size and
distribution of the monoazo laked pigment, including
stoichiometries of the DC and CC reactants, metal salt, surface
active agents, and stabilizer compounds, concentration of chemical
species in the liquid medium, pH of liquid medium, temperature,
addition rate, order of addition, agitation rate, post-reaction
treatments such as heating, isolation and washing of particles, and
drying conditions.
[0060] In embodiments is disclosed a two-step method of making
nanosized monoazo laked red pigments, for example Pigment Red 57:1,
wherein the advanced pigment precursor Lithol Rubine is first
synthesized as a potassium salt and is a water-soluble orange dye.
The first step involves the diazotization of
2-amino-5-methylbenzenesulfonic acid (DC1 in Table 1) by first
dissolving the DC in dilute aqueous potassium hydroxide solution
(0.5 mol/L) and cooling to a temperature of about -5.degree. C. to
about 10.degree. C., and then treating the solution with an aqueous
solution of sodium nitrite (20 wt %), following with slow addition
of concentrated hydrochloric acid at a rate that maintains the
internal reaction temperature between -5.degree. C. and +5.degree.
C. The resulting suspension that forms is stirred for additional
time at cool temperature, so as to ensure completeness of
diazotization, and then the suspension is carefully transferred to
a second solution containing 3-hydroxy-2-naphthoic acid dissolved
in dilute alkaline solution (0.5 mol/L potassium hydroxide) using
vigorous agitation as the colorant product is produced in the
aqueous slurry. After stirring for additional time of at least 1
hour at room temperature, the colorant product (Lithol
Rubine-potassium salt) is isolated by filtration as an orange
dyestuff and washed with deionized water to remove excess acid and
salt by-products.
[0061] The second step of this process involves redispersing the
orange Lithol Rubine-potassium salt dyestuff in deionized water to
a concentration that can range from about 0.5 wt % to about 20 wt
%, such as from about 1.5 wt % to about 10 wt % or from about 3.5
wt % to about 8 wt %, but the concentrations can also be outside of
these ranges. The colorant solids in the slurry is then dissolved
completely into liquid solution by treatment with aqueous alkaline
base, such as sodium hydroxide or potassium hydroxide or ammonium
hydroxide solution, until the pH level is high, such as above pH
8.0 or above pH 9.0 or above pH 10.0. To this alkaline solution of
dissolved Lithol Rubine colorant can be optionally added a surface
active agent as described earlier, in particular embodiments
surface active agent such as rosin soaps, delivered as an aqueous
solution in the amount ranging from 0.1 wt % to 20 wt % based on
colorant solids, such as in an amount ranging from 0.5 wt % to
about 10 wt %, or in an amount ranging from 1.0 wt % to about 8.0
wt % based on colorant solids, but the amount used can also be
outside of these ranges.
[0062] In embodiments, the preparation of ultrafine and nanosized
particles of the monoazo laked Pigment Red 57:1 was only enabled by
the additional use of a stabilizer compound having a functional
moiety that could non-covalently bond to the complementary
functional moiety of the pigment as well as branched aliphatic
functional groups that could provide steric bulk to the pigment
particle surface. In embodiments, particularly suitable sterically
bulky stabilizer compounds are branched hydrocarbons with either
carboxylate or sulfonate functional groups, compounds such as
di[2-ethylhexyl]-3-sulfosuccinate sodium or sodium
2-hexyldecanoate, and the like. The stabilizer compound is
introduced as a solution or suspension in a liquid that is
predominantly aqueous but may optionally contain a polar,
water-miscible co-solvent such as THF, iso-propanol, NMP, Dowanol
and the like, to aid dissolution of the stabilizer compound, in an
amount relative to colorant moles ranging from about 5 mole-percent
to about 100 mole-percent, such as from about 20 mole-percent to
about 80 mole-percent, or from about 30 mole-percent to about 70
mole-percent, but the concentrations used can also be outside these
ranges and in large excess relative to moles of colorant.
[0063] Lastly, the metal cation salt is added to transform the
pigment precursor (Lithol Rubine-potassium salt in embodiments)
into the desired monoazo laked pigment (Pigment Red 57:1 in
embodiments) as a precipitated pigment. The aqueous solution of
metal salt (calcium chloride in embodiments) with concentration
ranging anywhere from 0.1 mol/L to about 2 mol/L, is slowly added
dropwise in nearly stoichiometric quantities such as amounts
ranging from 1.0 molar equivalents relative to about 2.0 molar
equivalents, or from 1.1 to about 1.5 molar equivalents, or from
1.2 to about 1.4 molar equivalents relative to moles of colorant,
however the amounts used can also be outside of these ranges and in
large excess.
[0064] The type of metal salt can have an impact on the degree of
formation of nanosized pigment particles of monoazo laked pigments,
in particular the type of ligand that is coordinated to the metal
cation in the raw material and the relative ease with which it is
displaced by a competing ligand from either the pigment functional
moiety or the complementary functional moiety of the stabilizer
compound, or both. In embodiments for monoazo laked Pigment Red
57:1, the nanosized particles are formed using calcium (II) salts
with ligands such as chloride, sulfate, acetate, and hydroxide;
however a particularly desirable metal salt is calcium chloride for
fastest reactivity.
[0065] The rates of addition of metal salt solution can also vary.
For example, the slower the rate of addition, the more controlled
is the rate of pigment crystal formation and particle aggregation,
and therefore the smaller the pigment particles become.
[0066] Also important is the agitation rate and mixing pattern as
the pigment formation/precipitation step is occurring. The higher
the agitation rate and the more dynamic or complex is the mixing
pattern (i.e. with baffles to prevent dead mixing zones), the
smaller is the average particle diameter and the more narrow is the
particle size distribution, as observable by Transmission Electron
Microscopy (TEM) imaging.
[0067] Temperature during the pigment precipitation step using the
metal salt solution is also important. In embodiments, lower
temperatures are desired, such as from about 10.degree. C. to about
50.degree. C., or from about 15.degree. C. to about 35.degree. C.,
but the temperature can also be outside of these ranges.
[0068] In embodiments, the slurry of pigment nanoparticles is not
treated nor processed any further, such as additional heating, but
instead is isolated by vacuum filtration through membrane filter
cloth having average pore size of 0.45 micron or 0.8 micron
diameter. The pigment solids can be washed copiously with deionized
water to remove excess salts or additives that were not being
non-covalently bound to the pigment particles, as intended by the
stabilizer compounds. The pigment solids are subsequently dried by
freeze-drying under high vacuum to afford high quality,
non-agglomerated pigment particles that when imaged by TEM,
exhibited primary pigment particles and small aggregates ranging in
diameters from about 30 nm to about 150 nm, and predominantly from
about 50 nm to about 125 nm. (Here, it is noted that average
particle size d.sub.50 and particle size distributions are measured
by Dynamic Light Scattering, an optical measurement technique that
estimates the hydrodynamic radius of non-spherical pigment
particles gyrating and translating in a liquid dispersion via
Brownian motion, by measuring the intensity of the incident light
scattered from the moving particles. As such, the d.sub.50 particle
size metric obtained by DLS technique is always a larger number
than the actual particle diameters observed by TEM imaging.)
[0069] Characterization of the chemical composition of washed and
dried nanosized pigment particles are performed by NMR spectroscopy
and elemental analysis. In embodiments, the composition of the
monoazo laked pigment Red 57:1 indicated that the nanosized
particled prepared by the method described above, using
di[2-ethylhexyl]-3-sulfosuccinate sodium as the sterically bulky
stabilizer, retained at least 80% of the sterically bulky
stabilizer that was loaded into the process of making the
nanoparticles, even after copious washing with deionized water to
remove excess salts. Solid state .sup.1H- and .sup.13C-NMR
spectroscopic analyses indicated that the steric stabilizer
compound was associated non-covalently with the pigment as a
calcium salt, and the chemical structure of the pigment adopted the
hydrazone tautomer form, as shown in Figure below.
##STR00025##
[0070] Pigment particles of monoazo laked pigments such as PR 57:1
that have smaller particle sizes could also be prepared by the
above two-step method with the use of surface active agents alone
depending on the concentrations and process conditions employed,
but the pigment product did not predominantly exhibit nano-sized
particles nor did the particles exhibit regular morphologies. By
comparison, in the absence of using the sterically bulky stabilizer
compound, the two-step method described above typically produced
rod-like particle aggregates, ranging in average particle diameter
from 200-700 nm and with wide particle distribution, and such
particles were difficult to disperse into a polymer coating matrix
and gave poor coloristic properties. In embodiments, the combined
use of a suitable sterically bulky stabilizer compound, such as
branched alkanesulfonates or alkylcarboxylates, with a minor amount
of suitable surface active agent such as derivatives of rosin-type
natural products, by the two-step process would afford the smallest
fine pigment particles in the nanometer-scale diameters, more
narrow particle size distribution, and low aspect ratio. Various
combinations of these compounds, in addition to variations with
process parameters such as stoichiometry of reactants,
concentration, addition rate, temperature, agitation rate, reaction
time, and post-reaction product recovery processes, enables the
formation of pigment particles with tunable average particle size
(d.sub.50) from nanoscale sizes (about 1 to about 100 nm) to
mesoscale sizes (about 100 to about 500 nm) or larger. The
dispersion ability and coloristic properties (L*, a*, b*, chroma,
hue angle, light scatter index) of the pigment particles in a thin
polymer binder coating were directly correlated to the average
pigment particle size, which in turn was impacted by the structural
type and amount of sterically bulky stabilizer compound that was
employed in the synthesis process.
[0071] The advantages of this process include the ability to tune
particle size and composition for the intended end use application
of the monoazo laked pigment, such as toners and inks and coatings,
which include phase-change, gel-based and radiation-curable inks,
solid and non-polar liquid inks, solvent-based inks and aqueous
inks and ink dispersions. For the end-use application in
piezoelectric inkjet printing, nanosized particles are advantageous
to ensure reliable inkjet printing and prevent blockage of jets due
to pigment particle agglomeration. In addition, nanosized pigment
particles are advantageous for offering enhanced color properties
in printed images, since in embodiments the color properties of
nanosized particles of monoazo laked pigment Red 57:1 were tunable
with particle size, whereby as average particle size was decreased
to nanometer-scale, the hue angles were shifted from yellowish-red
hues to bluish-red hues by an amount ranging from about 5 to about
35.degree. in the color gamut space.
[0072] The method of making nanosized particles of monoazo laked
pigments can also be performed by a one-step method, wherein a
suitable aniline precursor (or diazo component DC, such as those
listed in Table 1), is either directly or indirectly converted
first to a diazonium salt using standard procedures, such as that
include treatment with a diazotizing agent such as nitrous acid
HNO.sub.2 (for example, generated in situ by mixing sodium nitrite
with dilute hydrochloric acid solution) or nitrosyl sulfuric acid
(NSA), which is commercially available or prepared by mixing sodium
nitrite in concentrated sulfuric acid. The resulting acidic mixture
of diazonium salt is either a solution or a suspension and is
preferably kept cold, to which is added an aqueous solution of the
metal salt (M.sup.n+) that will define the specific composition of
the desired monoazo laked pigment product, such as those listed in
Table 7. The diazonium salt solution or suspension is then
transferred into a solution or suspension of a suitable coupling
component (CC, such as those listed in Tables 2-6) that can be
either acidic or basic in pH and contain additional buffers and
surface active agents, including the sterically bulky stabilizer
compounds such as those described earlier, to produce a solid
colorant material suspended as an aqueous slurry. The solid
colorant material produced is the desired monoazo laked pigment
product suspended in aqueous slurry, which is isolated by vacuum
filtration, washed with copious amounts of deionized water to
remove excess salt by-products, and preferably freeze-dried under
vacuum, affording fine and nanosized particles of the pigment.
[0073] In embodiments, the nanosized pigment particles that were
obtained for monoazo laked pigments can range in average particle
size, d.sub.50, or average particle diameter, from about 10 nm to
about 250 nm, such as from about 25 nm to about 175 nm, or from
about 50 nm to about 150 nm, as measured by either dynamic light
scattering method or from TEM images. In embodiments, the particle
size distributions can range such that the geometric standard
deviation can range from about 1.1 to about 1.9, or from about 1.2
to about 1.7, as measured by dynamic light scattering method. The
shape of the nanosized pigment particles can be one or more of
several morphologies, including rods, platelets, needles, prisms or
nearly spherical, and the aspect ratio of the nanosize pigment
particles can range from 1:1 to about 10:1, such as having aspect
ratio between 1:1 and 5:1; however the actual metric can lie
outside of these ranges.
[0074] The color of the nanosized pigment particles have the same
general hue as is found with larger pigment particles. However, in
embodiments, is disclosed coloristic properties of thin coatings of
the nanosized pigment particles of red monoazo laked pigments
dispersed in a polymer binder (such as of poly(vinyl
butyral-co-vinyl alcohol-co-vinyl acetate)), that exhibited a
significant shift to lower hue angle and lower b* values that
revealed more bluish magenta hues, and having either no change or a
small enhancement of a* value. In embodiments, the hue angles of
the coatings dispersed with the nanosized particles of monoazo
laked pigment such as Pigment Red 57:1 measured in the range from
about 345.degree. to about 5.degree. on the 2-dimensional b*a*
color gamut space, as compared with hue angles ranging from about
0.degree. to about 20.degree. for similarly prepared polymer
coatings dispersed with larger sized particles of Pigment Red 57:1.
In embodiments is disclosed the coloristic properties (hue angle,
a*, b*, and NLSI as measure of specular reflectivity) of nanosized
pigment particles, particularly of monoazo laked red pigment, that
are directly correlated and tunable with the average pigment
particle size, measured by either Dynamic Light Scattering or
electron microscopy imaging techniques, as well as pigment
composition with the non-covalently associated stabilizer, the
latter which enables the control of particle size during pigment
synthesis, and also enables enhanced dispersability within certain
polymer binders for coating or other applications.
[0075] Additionally, the specular reflectivity of the coatings of
the nanosize monoazo lakes red pigment was significantly enhanced
from coatings produced with larger sized pigment particles, which
is an indicator of having very small particles being well-dispersed
within the coating. Specular reflectivity was quantified as the
degree of light scattering for the pigmented coating, a property
that is dependent on the size and shape distributions of the
pigment particles and their relative dispersability within the
coating binder. The Normalized Light Scatter Index (NLSI) was
quantified by measuring the spectral absorbance of the coating in a
region where there is no absorbance from the chromogen of the
monoazo laked pigment, but only absorbance due to light scattered
from large aggregates and/or agglomerated pigment particles
dispersed in the coating binder. The light scattering absorbance
data is then normalized to a lambda-max optical density of 1.5,
resulting in the NLSI value, in order to directly compare the light
scattering indices of several pigmented coatings. The lower is the
NLSI value, the smaller is the pigment particle size within the
dispersed coating matrix. In embodiments, the NLSI value of the
nanosized monoazo laked red pigments can range from about 0.1 to
about 3.0, such as from about 0.1 to about 1.0, as compared to the
NLSI values observed with similarly prepared coatings containing
larger sized monoazo laked red pigments that range anywhere from
about 3.0 to about 75 (a very poorly dispersed coating).
[0076] The formed nanoscale pigment particle compositions can be
used, for example, as coloring agents in a variety of compositions,
such as in liquid (aqueous or non-aqueous) ink vehicles, including
inks used in conventional pens, markers, and the like, liquid ink
jet ink compositions, solid or phase change ink compositions, and
the like. For example, the colored nanoparticles can be formulated
into a variety of ink vehicles, including "low energy" solid inks
with melt temperatures of about 60 to about 130.degree. C.,
solvent-based liquid inks or radiation-curable such as UV-curable
liquid inks comprised of alkyloxylated monomers, and even aqueous
inks. Various types of such compositions will now be described in
more detail.
[0077] In embodiments, these nanoscale-sized pigments can be
dispersed in a variety of media where such high specular
reflectance is afforded. Polymeric binders that aid in the
dispersion and coating ability of nanoscale-sized pigments include,
but are not limited to, derivatives of rosin natural products,
acrylic-based polymers, styrene-based copolymers, copolymers of
.alpha.-olefins such as 1-hexadecene, 1-octadecene, 1-eicosene,
1-triacontene and the like, copolymers of vinyl pyridine, vinyl
imidazole, and vinyl pyrrolidinone, polyester copolymers, polyamide
copolymers, copolymers of acetals. More specific examples of
polymeric binders include, but are not limited to, poly(vinyl
butyral-co-vinyl alcohol-co-vinyl acetate), poly(vinyl acetate),
poly(acrylic acid), poly(methacrylic acid), poly(vinyl alcohol),
poly(methyl methacrylate), polyester, Lexan.RTM., polycarbonate,
poly(styrene-b-4-vinylpyridine) and the like. Suitable mixtures of
at least two polymers can also be used to generate nanoscale-sized
pigments dispersions in liquid media. Suitable carrier solvents
used to disperse the nanoscale-sized pigments with various polymers
where solubility of the polymers is ensured include, but are not
limited to, n-butyl acetate, tetrahydrofuran, n-butanol, methyl
ethyl ketone, isopropyl alcohol, toluene, monochlorobenzene,
methylene chloride, water and the like. It may be desirable to use
suitable mixtures of at least two solvents with one polymeric
binder to effect dispersion of the nanoscale-sized pigments. It may
also be desirable to use suitable mixtures of at least two solvents
with at least two polymeric binders to effect dispersion of the
nanoscale-sized pigments.
[0078] The nanoscale-sized pigments can be formulated into a number
of different coating compositions having various adhesive and
coloristic properties on different media, including paperstock,
cardstock, and flexible substrates such as Melinex.RTM.,
Mylar.RTM., Cronar.RTM. and the like.
[0079] For considerations involving more permanent image
robustness, radiation curable inks can be used. The selection of
monomers for radiation-curable dispersions, and inks made from
them, is based on a number of criteria including the degree of
acrylate functionality and reactivity, viscosity, thermal
stability, surface tension, relative toxicological level, vapor
pressure and other considerations such as relative commercial
abundance and cost. It is desirable to have at least one UV monomer
that is a diacrylate which has a viscosity less than about 15 cP at
room temperature and less than about 3.5 cP at 85 C and which has a
surface tension more than about 30 dynes/cm at room temperature and
more than about 25 dynes/cm at 85 C, although the values can be
outside these ranges. For example, a propoxylated neopentyl glycol
diacrylate (SR-9003, available from Sartomer Company) satisfies
these viscosity and surface tension requirements for
radiation-curable dispersions suitable for preparing a
radiation-curable inkjet ink.
[0080] In embodiments, the use of dyes as colorants in
radiation-curable inks and dispersions containing photoinitiators
is limited and generally not desired as these dyes are generally
not photo-stable during the curing process and can become severely
bleached and washed out resulting in generally poor image quality
and low optical contrast of the image. It is more preferable to
utilize pigments in radiation-curable dispersions and inks due to
their much improved photo-stability over dyes during the curing
process.
[0081] In other embodiments, it is also preferable to utilize
nanoscale-sized pigments in radiation-curable inks and dispersions,
an advantage being due to the smaller particles of nanoscale-sized
pigments compared with larger-sized conventional pigments, whereby
a lesser amount by weight of nanoscale-sized pigment can be
formulated within a radiation-curable ink or dispersion compared
with using conventional pigments, to afford the same optical
density of final cured image.
[0082] In some embodiments, the radiation-curable ink composition
can include a radiation-curable gellant to act as a phase change
agent to gel the UV-curable monomer as it is jetted from the
printhead at elevated temperature and onto a substrate such as
paper at reduced temperature.
[0083] In embodiments, the radiation-curable ink composition can
include a radiation-curable wax, such as an acrylate wax, to act as
a phase change agent in the radiation-curable vehicle.
[0084] In still other embodiments, the radiation-curable ink
composition can include at least one radiation-curable gellant and
at least one radiation-curable wax.
[0085] Ink jet ink compositions according to this disclosure
generally include a carrier, a colorant, and one or more additional
additives. Such additives can include, for example, solvents,
waxes, antioxidants, tackifiers, slip aids, curable components such
as curable monomers and/or polymers, gallants, initiators,
sensitizers, humectants, biocides, preservatives, and the like.
Specific types and amounts of components will depend, of course, on
the specific type of ink composition, such as liquid, curable,
solid, hot melt, phase change, gel, or the like. The formed
nanoscale pigment particle compositions can be used, for example,
in such inks as colorants.
[0086] Generally, the ink compositions contain one or more
colorant. Any desired or effective colorant can be employed in the
ink compositions, including pigment, dye, mixtures of pigment and
dye, mixtures of pigments, mixtures of dyes, and the like. In
embodiments, the colorant used in the ink composition consists
entirely of the formed nanoscale-sized pigment compositions.
However, in other embodiments, the nanoscale-sized pigment
compositions can be used in combination with one or more
conventional or other colorant material, where the nanoscale-sized
pigment compositions can form substantially most of the colorant
material (such as about 90% or about 95% by weight or more), they
can form a majority of the colorant material (such as at least 50%
by weight or more), or they can form a minority of the colorant
material (such as less than about 50% by weight). For the end-use
application in piezoelectric inkjet printing, nanosized pigment
particles are advantageous to ensure reliable inkjet printing and
prevent blockage of jets due to pigment particle agglomeration. In
addition, nanosized pigment particles are advantageous for offering
enhanced color properties in printed images, since in embodiments
the color properties of nanosized particles of monoazo laked
pigment Red 57:1 were tunable with particle size, whereby as
average particle size (d.sub.50) was decreased to nanometer-scale,
the hue angles were shifted from yellowish-red hues to bluish-red
hues by an amount ranging from about 5 to 35.degree. in the color
gamut space. In still other embodiments, the nanoscale-sized
pigment compositions can be included in the ink composition in any
other varying amount, to provide either colorant and/or other
properties to the ink composition.
[0087] The colorant, such as nanoscale-sized pigment compositions
in embodiments, can be present in the ink composition in any
desired or effective amount to obtain the desired color or hue. For
example, the colorant can typically be present in an amount of at
least about 0.1 percent by weight of the ink, such as at least
about 0.2 percent by weight of the ink or at least about 0.5
percent by weight of the ink, and typically no more than about 50
percent by weight of the ink, such as no more than about 20 percent
by weight of the ink or no more than about 10 percent by weight of
the ink, although the amount can be outside of these ranges.
[0088] The ink compositions can also optionally contain an
antioxidant. The optional antioxidants of the ink compositions
protect the images from oxidation and also protect the ink
components from oxidation during the heating portion of the ink
preparation process. Specific examples of suitable antioxidants
include NAUGUARD.RTM. series of antioxidants, such as NAUGUARD.RTM.
445, NAUGUARD.RTM. 524, NAUGUARD.RTM. 76, and NAUGUARD.RTM. 512
(commercially available from Uniroyal Chemical Company, Oxford,
Conn.), the IRGANOX.RTM. series of antioxidants such as
IRGANOX.RTM. 1010 (commercially available from Ciba Geigy), and the
like. When present, the optional antioxidant can be present in the
ink in any desired or effective amount, such as in an amount of
from at least about 0.01 to about 20 percent by weight of the ink,
such as about 0.1 to about 5 percent by weight of the ink, or from
about 1 to about 3 percent by weight of the ink, although the
amount can be outside of these ranges.
[0089] The ink compositions can also optionally contain a viscosity
modifier. Examples of suitable viscosity modifiers include
aliphatic ketones, such as stearone, and the like. When present,
the optional viscosity modifier can be present in the ink in any
desired or effective amount, such as about 0.1 to about 99 percent
by weight of the ink, such as about 1 to about 30 percent by weight
of the ink, or about 10 to about 15 percent by weight of the ink,
although the amount can be outside of these ranges.
[0090] Other optional additives to the inks include clarifiers,
such as UNION CAMP.RTM. X37-523-235 (commercially available from
Union Camp); tackifiers, such as FORAL.RTM. 85, a glycerol ester of
hydrogenated abietic (rosin) acid (commercially available from
Hercules), FORAL.RTM. 105, a pentaerythritol ester of hydroabietic
(rosin) acid (commercially available from Hercules), CELLOLYN.RTM.
21, a hydroabietic (rosin) alcohol ester of phthalic acid
(commercially available from Hercules), ARAKAWA KE-311 Resin, a
triglyceride of hydrogenated abietic (rosin) acid (commercially
available from Arakawa Chemical Industries, Ltd.), synthetic
polyterpene resins such as NEVTAC.RTM. 2300, NEVTAC.RTM. 100, and
NEVTAC.RTM. 80 (commercially available from Neville Chemical
Company), WINGTACK.RTM. 86, a modified synthetic polyterpene resin
(commercially available from Goodyear), and the like; adhesives,
such as VERSAMID.RTM. 757, 759, or 744 (commercially available from
Henkel), plasticizers, such as UNIPLEX.RTM. 250 (commercially
available from Uniplex), the phthalate ester plasticizers
commercially available from Monsanto under the trade name
SANTICIZER.RTM., such as dioctyl phthalate, diundecyl phthalate,
alkylbenzyl phthalate (SANTICIZER.RTM. 278), triphenyl phosphate
(commercially available from Monsanto), KP-140.RTM., a
tributoxyethyl phosphate (commercially available from FMC
Corporation), MORFLEX.RTM. 150, a dicyclohexyl phthalate
(commercially available from Morflex Chemical Company Inc.),
trioctyl trimellitate (commercially available from Eastman Kodak
Co.), and the like; and the like. Such additives can be included in
conventional amounts for their usual purposes.
[0091] The ink composition also includes a carrier material, or
mixture of two or more carrier materials. The carrier material can
vary, for example, depending upon the specific type of ink
composition. For example, an aqueous ink jet ink composition can
use water, or a mixture of water and one or more other solvents, as
a suitable carrier material. Other ink jet ink compositions can use
one or more organic solvents as a carrier material, with or without
water.
[0092] In the case of a solid (or phase change) ink jet ink
composition, the carrier can include one or more organic compounds.
The carrier for such solid ink compositions is typically solid at
room temperature (about 20.degree. C. to about 25.degree. C.), but
becomes liquid at the printer operating temperature for ejecting
onto the print surface. Suitable carrier materials for solid ink
compositions can thus include, for example, amides, including
diamides, triamides, tetra-amides, and the like. Suitable triamides
include, for example, those disclosed in U.S. Patent Publication
No. 2004-0261656, the entire disclosure of which is incorporated
herein by reference. Suitable other amides, such as fatty amides
including monoamides, tetra-amides, mixtures thereof, are disclosed
in, for example, U.S. Pat. Nos. 4,889,560, 4,889,761, 5,194,638,
4,830,671, 6,174,937, 5,372,852, 5,597,856, and 6,174,937, and
British Patent No. GB 2 238 792, the entire disclosures of each are
incorporated herein by reference. In embodiments where an amide is
used as a carrier material, a triamide is particularly useful
because triamides are believed to have structures that are more
three-dimensional as compared to other amides such as diamides and
tetraamides.
[0093] Other suitable carrier materials that can be used in the
solid ink compositions include, for example, isocyanate-derived
resins and waxes, such as urethane isocyanate-derived materials,
urea isocyanate-derived materials, urethane/urea isocyanate-derived
materials, mixtures thereof, and the like.
[0094] Additional suitable solid ink carrier materials include
paraffins, microcrystalline waxes, polyethylene waxes, ester waxes,
amide waxes, fatty acids, fatty alcohols, fatty amides and other
waxy materials, sulfonamide materials, resinous materials made from
different natural sources (such as, for example, tall oil rosins
and rosin esters), and many synthetic resins, oligomers, polymers
and copolymers, such as ethylene/vinyl acetate copolymers,
ethylene/acrylic acid copolymers, ethylene/vinyl acetate/acrylic
acid copolymers, copolymers of acrylic acid with polyamides, and
the like, ionomers, and the like, as well as mixtures thereof. One
or more of these materials can also be employed in a mixture with a
fatty amide material and/or an isocyanate-derived material.
[0095] The ink carrier in a solid ink composition can be present in
ink in any desired or effective amount. For example, the carrier
can be present in an amount of about 0.1 to about 99 percent by
weight of the ink, such as about 50 to about 98 percent by weight
of the ink, or about 90 to about 95 percent by weight of the ink,
although the amount can be outside of these ranges.
[0096] In the case of a radiation, such as ultraviolet light,
curable ink composition, the ink composition comprises a carrier
material that is typically a curable monomer, curable oligomer, or
curable polymer, or a mixture thereof. The curable materials are
typically liquid at 25.degree. C. The curable ink composition can
further include other curable materials, such as a curable wax or
the like, in addition to the colorant and other additives described
above.
[0097] The term "curable" refers, for example, to the component or
combination being polymerizable, that is, a material that may be
cured via polymerization, including for example free radical
routes, and/or in which polymerization is photoinitiated though use
of a radiation sensitive photoinitiator. Thus, for example, the
term "radiation curable" refers is intended to cover all forms of
curing upon exposure to a radiation source, including light and
heat sources and including in the presence or absence of
initiators. Example radiation curing routes include, but are not
limited to, curing using ultraviolet (UV) light, for example having
a wavelength of 200-400 nm or more rarely visible light, such as in
the presence of photoinitiators and/or sensitizers, curing using
e-beam radiation, such as in the absence of photoinitiators, curing
using thermal curing, in the presence or absence of high
temperature thermal initiators (and which are generally largely
inactive at the jetting temperature), and appropriate combinations
thereof.
[0098] Suitable radiation, such as UV, curable monomers and
oligomers include, but are not limited to, acrylated esters,
acrylated polyesters, acrylated ethers, acrylated polyethers,
acrylated epoxies, urethane acrylates, and pentaerythritol
tetraacrylate. Specific examples of suitable acrylated oligomers
include, but are not limited to, acrylated polyester oligomers,
such as CN2262 (Sartomer Co.), EB 812 (Cytec Surface Specialties),
EB 810 (Cytec Surface Specialties), CN2200 (Sartomer Co.), CN2300
(Sartomer Co.), and the like, acrylated urethane oligomers, such as
EB270 (UCB Chemicals), EB 5129 (Cytec Surface Specialties), CN2920
(Sartomer Co.), CN3211 (Sartomer Co.), and the like, and acrylated
epoxy oligomers, such as EB 600 (Cytec Surface Specialties), EB
3411 (Cytec Surface Specialties), CN2204 (Sartomer Co.), CN110
(Sartomer Co.), and the like; and pentaerythritol tetraacrylate
oligomers, such as SR399LV (Sartomer Co.) and the like. Specific
examples of suitable acrylated monomers include, but are not
limited to, polyacrylates, such as trimethylol propane triacrylate,
pentaerythritol tetraacrylate, pentaerythritol triacrylate,
dipentaerythritol pentaacrylate, glycerol propoxy triacrylate,
tris(2-hydroxyethyl)isocyanurate triacrylate, pentaacrylate ester,
and the like, epoxy acrylates, urethane acrylates, amine acrylates,
acrylic acrylates, and the like. Mixtures of two or more materials
can also be employed as the reactive monomer. Suitable reactive
monomers are commercially available from, for example, Sartomer
Co., Inc., Henkel Corp., Radcure Specialties, and the like.
[0099] In embodiments, the at least one radiation curable oligomer
and/or monomer can be cationically curable, radically curable, or
the like.
[0100] The radiation curable monomer or oligomer variously
functions as a viscosity reducer, as a binder when the composition
is cured, as an adhesion promoter, and as a crosslinking agent, for
example. Suitable monomers can have a low molecular weight, low
viscosity, and low surface tension and comprise functional groups
that undergo polymerization upon exposure to radiation such as UV
light.
[0101] In embodiments, the monomer is equipped with one or more
curable moieties, including, but not limited to, acrylates;
methacrylates; alkenes; allylic ethers; vinyl ethers; epoxides,
such as cycloaliphatic epoxides, aliphatic epoxides, and glycidyl
epoxides; oxetanes; and the like. Examples of suitable monomers
include monoacrylates, diacrylates, and polyfunctional alkoxylated
or polyalkoxylated acrylic monomers comprising one or more di- or
tri-acrylates. Suitable monoacrylates are, for example, cyclohexyl
acrylate, 2-ethoxy ethyl acrylate, 2-methoxy ethyl acrylate,
2(2-ethoxyethoxy)ethyl acrylate, stearyl acrylate,
tetrahydrofurfuryl acrylate, octyl acrylate, lauryl acrylate,
behenyl acrylate, 2-phenoxy ethyl acrylate, tertiary butyl
acrylate, glycidyl acrylate, isodecyl acrylate, benzyl acrylate,
hexyl acrylate, isooctyl acrylate, isobornyl acrylate, butanediol
monoacrylate, ethoxylated phenol monoacrylate, oxyethylated phenol
acrylate, monomethoxy hexanediol acrylate, beta-carboxy ethyl
acrylate, dicyclopentyl acrylate, carbonyl acrylate, octyl decyl
acrylate, ethoxylated nonylphenol acrylate, hydroxyethyl acrylate,
hydroxyethyl methacrylate, and the like. Suitable polyfunctional
alkoxylated or polyalkoxylated acrylates are, for example,
alkoxylated, such as ethoxylated or propoxylated, variants of the
following: neopentyl glycol diacrylates, butanediol diacrylates,
trimethylolpropane triacrylates, glyceryl triacrylates,
1,3-butylene glycol diacrylate, 1,4-butanediol diacrylate,
diethylene glycol diacrylate, 1,6-hexanediol diacrylate,
tetraethylene glycol diacrylate, triethylene glycol diacrylate,
tripropylene glycol diacrylate, polybutanediol diacrylate,
polyethylene glycol diacrylate, propoxylated neopentyl glycol
diacrylate, ethoxylated neopentyl glycol diacrylate, polybutadiene
diacrylate, and the like.
[0102] In embodiments where the ink composition is a radiation
curable ink composition, the ink composition includes at least one
reactive monomer and/or oligomer. However, other embodiments can
include only one or more reactive oligomers, only one or more
reactive monomers, or a combination of one or more reactive
oligomers and one or more reactive monomers. However, in
embodiments, the composition includes at least one reactive
(curable) monomer, and optionally one or more additional reactive
(curable) monomers and/or one or more reactive (curable)
oligomers.
[0103] The curable monomer or oligomer in embodiments is included
in the ink in an amount of, for example, about 20 to about 90% by
weight of the ink, such as about 30 to about 85% by weight of the
ink, or about 40 to about 80% by weight of the ink. In embodiments,
the curable monomer or oligomer has a viscosity at 25.degree. C. of
about 1 to about 50 cP, such as about 1 to about 40 cP or about 10
to about 30 cP. In one embodiment, the curable monomer or oligomer
has a viscosity at 25.degree. C. of about 20 cP. Also, in some
embodiments, it is desired that the curable monomer or oligomer is
not a skin irritant, so that printed images using the ink
compositions are not irritable to users.
[0104] Also in embodiments where the ink is a radiation curable
ink, the composition further comprises an initiator, such as a
photoinitiator, that initiates polymerization of curable components
of the ink, including the curable monomer and the curable wax. The
initiator should be soluble in the composition. In embodiments, the
initiator is a UV-activated photoinitiator.
[0105] In embodiments, the initiator can be a radical initiator.
Examples of suitable radical photoinitiators include ketones such
as hydroxycyclohexylphenyl ketones, benzyl ketones, monomeric
hydroxyl ketones, polymeric hydroxyl ketones, .alpha.-amino
ketones, and 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone;
benzoins; benzoin alkyl ethers; acyl phosphine oxides,
metallocenes, benzophenones, such as 2,4,6-trimethylbenzophenone
and 4-methylbenzophenone; trimethylbenzoylphenylphosphine oxides
such as 2,4,6-trimethylbenzoyl-diphenylphosphine oxide; azo
compounds; anthraquinones and substituted anthraquinones, such as,
for example, alkyl substituted or halo substituted anthraquinones;
other substituted or unsubstituted polynuclear quinines;
acetophenones, thioxanthones; ketals; acylphosphines;
thioxanthenones, such as 2-isopropyl-9H-thioxanthen-9-one; mixtures
thereof; and the like. One suitable ketone is
1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one.
In an embodiment, the ink contains an .alpha.-amino ketone,
1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one
and 2-isopropyl-9H-thioxanthen-9-one. In another embodiment, the
photoinitiator is one of the following compounds or a mixture
thereof: a hydroxycyclohexylphenyl ketone, such as, for example,
1-hydroxycyclohexylphenyl ketone, such as, for example,
Irgacure.RTM. 184 (Ciba-Geigy Corp., Tarrytown, N.Y.), having the
structure:
##STR00026##
a trimethylbenzoylphenylphosphine oxide, such as, for example,
ethyl-2,4,6-trimethylbenzoylphenylphosphinate, such as, for
example, Lucirin.RTM. TPO-L (BASF Corp.), having the formula
##STR00027##
a mixture of 2,4,6-trimethylbenzophenone and 4-methylbenzophenone,
such as, for example, SARCURE.TM. SR1137 (Sartomer); a mixture of
2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide and
2-hydroxy-2-methyl-1-phenylpropan-1-one, such as, for example,
DAROCUR.RTM. 4265 (Ciba Specialty Chemicals); alpha-amino ketone,
such as, for example, IRGACURE.RTM. 379 (Ciba Specialty Chemicals);
4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, such as, for
example, IRGACURE.RTM. 2959 (Ciba Specialty Chemicals);
2-isopropyl-9H-thioxanthen-9-one, such as, for example,
DAROCUR.RTM. ITX (Ciba Specialty Chemicals); and mixtures
thereof.
[0106] In other embodiments, the initiator can be a cationic
initiator. Examples of suitable cationic photoinitiators include
aryldiazonium salts, diaryliodonium salts, triarysulfonium salts,
triarylselenonium salts, dialkylphenacylsulfonium salts,
triarylsulphoxonium salts and aryloxydiarylsulfonium salts.
[0107] The total amount of initiator included in the ink may be,
for example, about 0.5 to about 15%, such as about 1 to about 10%,
by weight of the ink.
[0108] The ink, such as the radiation curable ink, may also
optionally contain at least one gellant. The gellant can be
included, for example, to control the viscosity of the ink
composition before and/or after jetting. For example, suitable
gellants include a curable gellant comprised of a curable
polyamide-epoxy acrylate component and a polyamide component, a
curable composite gellant comprised of a curable epoxy resin and a
polyamide resin, and the like.
[0109] Suitable curable composite gellants include those described
in U.S. Pat. Nos. 6,492,458 and 6,399,713, and U.S. Patent
Publications Nos. US 2003/0065084, US 2007/0120921, and US
2007/0120924, the entire disclosures of which are incorporated
herein by reference. The ink compositions can include the gellant
in any suitable amount, such as about 1% to about 50% by weight of
the ink. In embodiments, the gellant can be present in an amount of
about 2% to about 20% by weight of the ink, such as about 5% to
about 15% by weight of the ink, although the value can also be
outside of this range.
[0110] In the uncured state, the radiation-curable ink composition
in embodiments is a low viscous liquid and is readily jettable. For
example, in embodiments, the ink has a viscosity of from 8 mPa-s to
15 mPa-s, such as from 10 mPa-s to 12 mPa-s, at a temperature
between 60.degree. C. and 100.degree. C. In embodiments, the ink
has a viscosity of from 10.sup.5 to 10.sup.7 mPa-s at a temperature
of 50.degree. C. or below, specifically at a temperature from
0.degree. C. to 50.degree. C. Upon exposure to a suitable source of
curing energy, e.g., ultraviolet light, electron beam energy, or
the like, the photoinitiator absorbs the energy and sets into
motion a reaction that converts the liquid composition into a cured
material. The monomer and/or oligomer in the composition contain
functional groups that polymerize during exposure to the curing
source to readily crosslink forming a polymer network. This polymer
network provides printed image with, for example, durability,
thermal and light stability, and scratch and smear resistance.
Thus, the composition is particularly well-suited for ink-based
images printed on substrates that may be subjected to heat or
sunlight, because the composition provides a printed image that is
resistant to cracking and fading and provides image permanence.
[0111] In contrast to the curable ink compositions, the solid or
phase change ink compositions typically have melting points no
lower than about 50.degree. C., such as about 50.degree. C. to
about 160.degree. C. or more. In embodiments, the ink compositions
have a melting point of about 70.degree. C. to about 140.degree.
C., such as about 80.degree. C. to about 100.degree. C., although
the melting point can be outside of these ranges. The ink
compositions also generally a have melt viscosity at the jetting
temperature (such as typically about 75.degree. C. to about
180.degree. C., or about 100.degree. C. to about 150.degree. C. or
about 120.degree. C. to about 130.degree. C., although the jetting
temperature can be outside of these ranges) typically of about 2 to
about 30 centipoise, such as about 5 to about 20 centipoise or
about 7 to about 15 centipoise, although the melt viscosity can be
outside of these ranges. Because image hardness tends to drop with
lower viscosities, it is desired in embodiments that the viscosity
be as low as possible while still retaining the desired degree of
image hardness.
[0112] In embodiments, the radiation-curable ink composition can
include a water soluble or dispersable radiation-curable materials,
such as polyethylene glycol diacrylates, ethoxylated
trimethylolpropane triacrylate, ethoxylated bisphenol A
diacrylates, UCECOAT waterborne UV curable resins available from
Cytec Surface Specialties. Water dispersible photoinitiators can
include Esacure DP250 available from Lamberti SpA. Optional
dispersing agents include EFKA 7431 and 7441 available from Ciba
Specialty Chemicals.
[0113] The ink compositions of the present disclosure can also
optionally contain other materials, which may depend upon the type
of printer in which the ink is used. For example, the carrier
composition is typically designed for use in either a direct
printing mode or an indirect or offset printing transfer
system.
[0114] In embodiments, the present invention can include ink
compositions which comprise an aqueous liquid vehicle and the
nanoscale-sized pigment composition disclosed herein. The liquid
vehicle can consist solely of water, or it can comprise a mixture
of water and a water soluble or water miscible organic component,
such as ethylene glycol, propylene glycol, diethylene glycols,
glycerine, dipropylene glycols, polyethylene glycols, polypropylene
glycols, amides, ethers, urea, substituted ureas, ethers,
carboxylic acids and their salts, esters, alcohols, organosulfides,
organosulfoxides, sulfones (such as sulfolane), alcohol
derivatives, carbitol, butyl carbitol, cellusolve, tripropylene
glycol monomethyl ether, ether derivatives, amino alcohols,
ketones, N-methylpyrrolidinone, 2-pyrrolidinone,
cyclohexylpyrrolidone, hydroxyethers, amides, sulfoxides, lactones,
polyelectrolytes, methyl sulfonylethanol, imidazole, betaine, and
other water soluble or water miscible materials, as well as
mixtures thereof.
[0115] In other embodiments encompassing non-aqueous inks, the
nanoscale-sized pigment composition can be used as colorants for
solvent-borne inks such as petroleum-based inks which can include
aliphatic hydrocarbons, aromatic hydrocarbons, and mixtures
thereof, environmentally friendly soy and vegetable oil-based inks,
linseed oil-based inks and other ink-based vehicles derived from
natural sources. Other examples of ink vehicles for nanopigment
particles include isophthalic alkyds, higher order alcohols and the
like. In still other embodiments, the present invention of
nanopigment particles can be applied towards inks used in relief,
gravure, stencil, and lithographic printing.
[0116] The ink compositions of the present disclosure can be
prepared by any desired or suitable method. For example, in the
case of solid or phase change inks, or even curable inks, the ink
ingredients can be mixed together, followed by heating, typically
to a temperature of from about 100 to about 140.degree. C.,
although the temperature can be outside of this range, and stirring
until a homogeneous ink composition is obtained, followed by
cooling the ink to ambient temperature (typically from about 20 to
about 25.degree. C.). In the case of liquid ink compositions, the
ink ingredients can simply be mixed together with stirring to
provide a homogeneous composition, although heating can also be
used if desired or necessary to help form the composition.
[0117] In addition to ink compositions, the nanoscale-sized pigment
composition can be used in a variety of other applications, where
it is desired to provide a specific color to the composition. For
example, the nanoscale-sized pigment composition can also be used
in the same manner as conventional pigments in such uses as
colorants for paints, resins, lenses, filters, printing inks, and
the like according to applications thereof. By way of example only,
the nanoscale-sized pigment composition of embodiments can be used
for toner compositions, which include polymer particles and
nanoscale pigment particles, along with other optional additives,
that are formed into toner particles and optionally treated with
internal or external additives such as flow aids, charge control
agents, charge-enhancing agents, filler particles,
radiation-curable agents or particles, surface release agents, and
the like. The toner composition of the present invention can be
prepared by a number of known methods including extrusion melt
blending of the toner resin particles, nanoscale pigment particles
and other colorants and other optional additives, followed by
mechanical comminution and classification. Other methods include
those well known in the art such as spray drying, melt dispersion,
extrusion processing, dispersion polymerization, and suspension
polymerization. Further, the toner compositions can be prepared by
emulsion/aggregation/coalescence processes, as disclosed in
references U.S. Pat. No. 5,290,654, U.S. Pat. No. 5,278,020, U.S.
Pat. No. 5,308,734, U.S. Pat. No. 5,370,963, U.S. Pat. No.
5,344,738, U.S. Pat. No. 5,403,693, U.S. Pat. No. 5,418,108, U.S.
Pat. No. 5,364,729, and U.S. Pat. No. 5,346,797. The toner
particles can in turn be mixed with carrier particles to form
developer compositions. The toner and developer compositions can be
used in a variety of electrophotographic printing systems.
[0118] An example is set forth herein below and is illustrative of
different compositions and conditions that can be utilized in
practicing the disclosure. All proportions are by weight unless
otherwise indicated. It will be apparent, however, that the
disclosure can be practiced with many types of compositions and can
have many different uses in accordance with the disclosure above
and as pointed out hereinafter.
EXAMPLES
Examples of Compositions and Method of Making Nanosized Monoazo
Laked Red Pigment
Comparative Example
[0119] Synthesis of Pigment Red 57:1 by a two-step method (Expt.
#30176-50)
[0120] Synthesis of Lithol Rubine-Potassium Salt Dye, a precursor
to making Pigment Red 57:1 (Expt. # 30176-17)
[0121] Diazotization Step: Into a 500 mL round bottom flask
equipped with a mechanical stirrer, thermometer, and addition
funnel was dissolved 2-amino-5-methylbenzenesulfonic acid (8.82 g)
into 0.5M KOH aqueous solution (97.0 mL). The resulting brown
solution was cooled to 0.degree. C. A 20 wt % aqueous solution of
sodium nitrite (NaNO.sub.2; 3.28 g dissolved into 25 mL water) was
added slowly to the first solution while maintaining the
temperature below 3.degree. C. To the red-brown homogeneous mixture
was added dropwise concentrated HCl (10M, 14.15 mL) over 1 hour,
maintaining the internal temperature below 2.degree. C. The mixture
formed a pale brown suspension, and following complete addition of
conc. HCl, the suspension was stirred an additional 30 min.
[0122] Coupling Step: In a separate 2-L resin kettle was dissolved
3-hydroxy-2-naphthoic acid (8.86 g) into an aqueous solution of KOH
(8.72 g) in water (100 mL). An additional 250 mL of water was
added, and the light-brown solution was then cooled to 15.degree.
C. while stirring vigorously. The cold suspension of the diazonium
salt suspension was then added slowly to the coupling solution
while mixing vigorously. The color changed immediately to a dark
red solution, and ultimately to a yellowish-red (orange) slurry of
precipitated dyestuff. The mixture was stirred for 2 hours while
warming up to room temp, then filtered and diluted with about 500
mL of deionized water to produce an orange aqueous slurry of Lithol
Rubine-Potassium salt dye having solids content of about 1.6 wt
%.
Laking of Lithol Rubine-Potassium Salt Dye to Produce Pigment Red
57:1
[0123] Into a 500 mL round bottom flask equipped with mechanical
stirrer and condenser was charged 126 g of aqueous slurry of Lithol
Rubine-Potassium salt dye from above (Comparative Example) having
about 1.6% wt solids content. The pH of the slurry was adjusted to
at least 9.0 or higher by addition of 0.5 M KOH solution, after
which the dyestuff was fully rendered into homogeneous solution
that was dark black-red in color. An aqueous solution of calcium
chloride dihydrate (0.5 M solution, 13 mL) was added dropwise to
the slurry while stirring vigorously. A red precipitate formed
immediately, and after addition was completed, the slurry was
stirred for an additional 1 hour. The red slurry was then heated to
about 75.degree. C. for 20 min, then cooled to room temp. The
slurry was filtered under high vacuum through a 1.2 .mu.m Nylon
membrane cloth, then reslurried twice with 200 mL portions of
deionized water. The pH and conductivity of the filtrates after
each filtration were measured and recorded, with the final wash
filtrate having nearly neutral pH of 6.2 and conductivity of about
13.5 .mu.S/cm, indicating low residual salts. The red pigment
filtercake was reslurried into about 200 mL of DIW and freeze-dried
for 48 hours, to afford a red colored powder (1.95 grams).
Example 1
Synthesis of Lithol Rubine-Potassium Salt Dye, a Precursor to
Making Pigment Red 57:1
[0124] Diazotization Step: Into a 500 mL round bottom flask
equipped with a mechanical stirrer, thermometer, and addition
funnel was dissolved 2-amino-5-methylbenzenesulfonic acid (8.82 g)
into 0.5M KOH aqueous solution (97.0 mL). The resulting brown
solution was cooled to 0.degree. C. A 20 wt % aqueous solution of
sodium nitrite (NaNO.sub.2; 3.28 g dissolved into 25 mL water) was
added slowly to the first solution while maintaining the
temperature below 3.degree. C. To the red-brown homogeneous mixture
was added dropwise concentrated HCl (10M, 14.15 mL) over 1 hour,
maintaining the internal temperature below 2.degree. C. The mixture
formed a pale brown suspension, and following complete addition of
conc. HCl, the suspension was stirred an additional 30 min.
[0125] Coupling Step: In a separate 2-L resin kettle was dissolved
3-hydroxy-2-naphthoic acid (8.86 g) into an aqueous solution of KOH
(8.72 g) in water (100 mL). An additional 250 mL of water was
added, and the light-brown solution was then cooled to 15.degree.
C. while stirring vigorously. The cold suspension of the diazonium
salt suspension was then added slowly to the coupling solution
while mixing vigorously. The color changed immediately to a dark
red solution, and ultimately to a yellowish-red (orange) slurry of
precipitated dyestuff. The mixture was stirred for 2 hours while
warming up to room temp, then filtered and reslurried with about
500 mL of deionized water to produce an orange aqueous slurry of
Lithol Rubine-Potassium salt dye having solids content of about 1.6
wt %.
Example 2
Synthesis of Lithol Rubine-Potassium Salt Dye, a Precursor to
Making Pigment Red 57:1
[0126] Diazotization Step: Into a 500 mL round bottom flask
equipped with a mechanical stirrer, thermometer, and addition
funnel was dissolved 2-amino-5-methylbenzenesulfonic acid (12.15 g)
into 0.5M KOH aqueous solution (135 mL). The resulting brown
solution was cooled to 0.degree. C. A 20 wt % aqueous solution of
sodium nitrite (NaNO.sub.2; 4.52 g dissolved into 30 mL water) was
added slowly to the first solution while maintaining the
temperature below -2.degree. C. Concentrated HCl (10M, 19.5 mL) was
then slowly added dropwise over 1 hour while maintaining the
internal temperature below 0.degree. C. The mixture formed a pale
brown suspension and following complete addition of conc. HCl, the
suspension was stirred an additional 30 min.
[0127] Coupling Step: In a separate 2-L resin kettle was dissolved
3-hydroxy-2-naphthoic acid (12.2 g) into an aqueous solution of KOH
(12.0 g) in water (130 mL). An additional 370 mL of water was
added, and the pale brown solution was then cooled to about
15.degree. C. while stirring. The cold suspension of the diazonium
salt solution was then added slowly to the coupling solution while
mixing vigorously. The color change was immediate to dark black-red
solution, and ultimately to a yellowish-red (orange) slurry of
precipitated dyestuff. The mixture was stirred for at least 2 hours
while warming up to room temp, then filtered and reslurried with
about 600 mL of deionized water to produce an orange-colored slurry
of Lithol Rubine-Potassium salt dye having solids content of about
3.6%-wt.
Example 3
Preparation of Nanosized Particles of Pigment Red 57:1
[0128] Into a 500 mL round bottom flask equipped with mechanical
stirrer and condenser was charged 126 g of aqueous slurry of Lithol
Rubine-Potassium salt dye from above (Example 1) having about 1.6%
wt solids content. The pH of the slurry was adjusted to at least
9.0 or higher by addition of 0.5 M KOH solution, after which the
dyestuff was fully rendered into homogeneous solution that was dark
black-red in color. An aqueous solution 5 wt % Dresinate X (4.0 mL)
was added, followed by a solution containing sodium dioctyl
sulfosuccinate (0.96 g) dissolved in 100 mL of 90:10 deionized
water/THF mixture. No visible change was observed. An aqueous
solution of calcium chloride dihydrate (0.5 M solution, 13 mL) was
added dropwise to the slurry while stirring vigorously. A red
precipitate formed immediately, and after complete addition of the
calcium chloride solution, the slurry was stirred for an additional
1 hour. The red slurry was then heated to about 75.degree. C. for
20 min, then cooled to room temp. The slurry was filtered under
high vacuum through a 0.45 .mu.m Nylon membrane cloth, then
reslurried twice with 75 mL portions of DIW. The pH and
conductivity of the final wash filtrate was 7.4 and about 110
.mu.S/cm, respectively, indicating that residual acids and salt
by-products were removed. The red pigment filtercake was reslurried
in about 250 mL of DIW and freeze-dried for 48 hours to afford a
dark red colored powder (2.65 grams). Transmission electron
microscopy images of the powder revealed platelet-like particles
with particle diameters ranging from 30-150 nm. .sup.1H-NMR
spectroscopy analysis (300 MHz, DMSO-d.sub.6) of the pigment
indicated that the pigment adopted the hydrazone tautomer form, and
that the dioctyl sulfosuccinate stabilizer compound was present at
approximately 40 mol % and associated with a calcium cation
(determined by ICP spectroscopy).
Example 4
Preparation of Nanosized Particles of Pigment Red 57:1
[0129] The procedure of Example 3 was reproduced. Into a 500 mL
round bottom flask equipped with mechanical stirrer and condenser
was charged 126 g of aqueous slurry of Lithol Rubine-Potassium salt
dye from above (Example 1) having about 1.6% wt solids content. The
pH of the slurry was adjusted to at least 9.0 or higher by addition
of 0.5 M KOH solution, after which the dyestuff was fully rendered
into homogeneous solution that was dark black-red in color. An
aqueous solution 5 wt % Dresinate X (4.0 mL) was added, followed by
a solution containing sodium dioctyl sulfosuccinate (0.96 g)
dissolved in 100 mL of 90:10 deionized water/THF mixture. No
visible change was observed. An aqueous solution of calcium
chloride dihydrate (0.5 M solution, 13 mL) was added dropwise to
the slurry while stirring vigorously. A red precipitate formed
immediately, and after complete addition of the calcium chloride
solution, the slurry was stirred for an additional 1 hour. The red
slurry was then heated to about 75.degree. C. for 20 min, then
cooled to room temp. The slurry was filtered under high vacuum
through a 0.45 .mu.m Nylon membrane cloth, then reslurried twice
with 75 mL portions of DIW. The pH and conductivity of the final
wash filtrate was 7.15 and about 155 .mu.S/cm, respectively. The
red pigment filtercake was reslurried in about 250 mL of DIW and
freeze-dried for 48 hours to afford a dark red-colored powder (2.62
grams). Transmission electron microscopy images of the powder
revealed platelet-like particles with particle diameters ranging
from 50-175 nm.
Example 5
Preparation of Nanosized Particles of Pigment Red 57:1
[0130] Into a 1-L resin kettle equipped with mechanical stirrer and
condenser was charged 265 g of aqueous slurry of Lithol
Rubine-Potassium salt dye prepared from Example 2, having
approximately 3.75%-wt solids content). The pH of the slurry was
adjusted to at least 9.0 or higher by addition of 0.5 M KOH
solution, after which the dyestuff was fully rendered into
homogeneous solution that was dark black-red in color. An aqueous
solution 5 wt % Dresinate X (20.0 mL) was added while stirring,
followed by a solution containing sodium dioctyl sulfosuccinate
(4.8 g) dissolved in 220 mL of 90:10 deionized water/THF mixture
was slowly added to the mixture with stirring. An aqueous solution
of calcium chloride dihydrate (0.5 M solution, 65 mL) was added
dropwise to the slurry while stirring vigorously. A red precipitate
formed immediately, and after complete addition of the calcium
chloride solution, the slurry was stirred for an additional 1 hour.
The red slurry was then heated to about 60.degree. C. for 30 min,
then cooled immediately in a cold water bath. The slurry was
filtered under high vacuum through a 0.8 micron Versapor membrane
cloth (obtained from PALL Corp.), then reslurried twice with about
750 mL portions of DIW, and filtered once more. The pH and
conductivity of the final wash filtrate was 7.5 and about 208
.mu.S/cm, respectively. The red pigment filtercake was reslurried
in about 600 mL of deionized water and freeze-dried for 48 hours,
to afford a dark red-colored powder (12.75 grams). Transmission
electron microscopy images of the powder revealed predominantly
platelet-like particles with particle diameters ranging from 50-150
nm.
Example 6
Preparation of Nanosized Particles of Pigment Red 57:1
[0131] Into a 250 mL round bottom flask equipped with mechanical
stirrer and condenser was charged 10 g of aqueous slurry of Lithol
Rubine-Potassium salt dye prepared as in Example 2 but having a
solids concentration in the aqueous slurry of about 10.0 wt %. The
pH of the slurry was adjusted to at least 9.0 or higher by addition
of 0.5 M KOH solution, after which the dyestuff was fully rendered
into homogeneous solution that was dark black-red in color. An
aqueous solution 5 wt % Dresinate X (1.0 mL) was added, followed by
a 0.05 mol/L solution (34.5 mL) containing sodium dioctyl
sulfosuccinate dissolved in 90:10 deionized water/THF. No visible
change was observed. An aqueous solution of calcium chloride
dihydrate (1.0 M solution, 2.15 mL) was added dropwise by syringe
pump to the slurry while stirring vigorously. A red precipitate
formed immediately, and then the slurry was stirred at room
temperature for an additional 30 min. The red slurry was then
filtered under high vacuum through a 0.8 .mu.m Versapor membrane
cloth (obtained from PALL Corp.), then reslurried twice with 50 mL
portions of deionized water and filtered each time after
reslurrying. The pH and conductivity of the final wash filtrate was
7.5 and about 135 .mu.S/cm, respectively, indicating that residual
acids and salt by-products were removed. The red pigment filtercake
was reslurried in about 30 mL of deionized water and freeze-dried
for 48 hours to afford a dark red colored powder (1.32 grams).
Transmission electron microscopy images of the powder revealed very
small platelet-like particles with particle diameters ranging from
50-175 nm. .sup.1H-NMR spectroscopy analysis (300 MHz,
DMSO-d.sub.6) of the material indicated that the pigment adopted
the hydrazone tautomer form, and that the dioctyl sulfosuccinate
stabilizer compound was present at a level ranging from
approximately 50-75 mol %.
Example 7
Preparation of Fine and Nanoscale Particles of Pigment Red 57:1
[0132] Into a 500 mL round bottom flask equipped with mechanical
stirrer and condenser was charged 126 g of aqueous slurry of Lithol
Rubine-Potassium salt dye from above (Example 1) having about 1.6%
wt solids content. The pH of the slurry was adjusted to at least
9.0 or higher by addition of 0.5 M KOH solution, after which the
dyestuff was fully rendered into homogeneous solution that was dark
black-red in color. An aqueous solution 5 wt % Dresinate X (4.0 mL)
was added, followed by a solution containing sodium dioctyl
sulfosuccinate (1.92 g) dissolved in 100 mL of 90:10 deionized
water/THF mixture. No visible change was observed. An aqueous
solution of calcium chloride dihydrate (0.5 M solution, 13 mL) was
added dropwise to the slurry while stirring vigorously. A red
precipitate formed immediately, and after complete addition of the
calcium chloride solution, the slurry was stirred for an additional
1 hour. The red slurry was then heated to about 75.degree. C. for
20 min, then cooled to room temp. The slurry was filtered under
high vacuum through a 0.45 .mu.m Nylon membrane cloth, then
reslurried twice with 75 mL portions of DIW. The pH and
conductivity of the final wash filtrate was 7.75 and conductivity
of about 500 .mu.S/cm. The red pigment filtercake was reslurried in
about 250 mL of DIW and freeze-dried for 48 hours to afford a dark
red-colored powder (2.73 grams). Transmission electron microscopy
images of the powder showed a wide distribution of particle sizes,
ranging from 50 to 400 nm and having particle morphologies that
were predominantly platelets.
Example 8
Preparation of Fine and Nanosized Particles of Pigment Red 57:1
[0133] The sterically bulky stabilizer compound used was potassium
salt of 2-hexyldecanoic acid, prepared by treatment of
2-hexyldecanoic acid with potassium hydroxide dissolved in THF,
after which the THF solvent was removed. Into a 500-mL round-bottom
flask equipped with condenser and mechanical stirrer was charged
126 g of aqueous slurry of Lithol Rubine-Potassium salt from above
(Example 1) having about 1.6% wt solids content. The pH of the
slurry was adjusted to at least 9.0 or higher by addition of 0.5 M
KOH solution, after which the dyestuff was fully rendered into
homogeneous solution that was dark black-red in color. An aqueous
solution 5 wt % Dresinate X (4.0 mL) was added, followed by a
solution containing potassium 2 hexyldecanoate (1.28 g) dissolved
in 100 mL of 80:20 deionized water/THF mixture, added dropwise
while stirring vigorously. An aqueous solution of calcium chloride
dihydrate (0.5 M solution, 13 mL) was added to the slurry while
stirring vigorously causing a bluish-red pigment precipitate to
form. The slurry was stirred for 1 hour, heated to about 75.degree.
C. for 20 min, then cooled to room temperature. The slurry was
filtered under high vacuum through a 0.8 .mu.m Nylon membrane
cloth, then reslurried once with 150 mL of DIW and filtered again.
The pH and conductivity of the final wash filtrate was pH 8.38 and
conductivity of about 63 .mu.S/cm. The red pigment 57:1 filtercake
was reslurried into about 150 mL of DIW and freeze-dried for 48
hours to afford a red powder (2.95 grams). TEM micrograph images
showed a wide distribution of particle sizes, ranging from 50 to
400 nm and having particle morphologies that included platelets as
well as rods.
Examples of Pigment Dispersions and Properties
Example 9
Preparation of Liquid Pigment Dispersions and Polymer Coatings
[0134] A series of liquid non-aqueous dispersions were prepared
using a polymeric dispersant and the nanosized PR 57:1 pigments
from Examples 3, 4, 5, 6, 7, and 8; the larger-sized pigment
particles prepared in the Comparative Example; as well as two
commercial sources of PR 57:1 obtained from Clariant (lot #L7B01)
and Aakash. Coatings on clear Mylar film were prepared from these
liquid dispersions, and evaluated in the following manner: Into a
30 mL amber bottle was added 0.22 g of pigment, 0.094 g
polyvinylbutyral (B30HH obtained from Hoescht), 7.13 g n-butyl
acetate (glass-distilled grade, obtained from Calcdon Laboratories)
and 70.0 g of 1/8'' stainless steel shot (Grade 25 440C obtained
from Hoover Precision Products). The bottles were transferred to a
jar mill and were allowed to gently mill for 4 days at 100 RPM. Two
draw-down coatings were obtained for each dispersion using an
8-path gap on clear Mylar.quadrature. film such that the wet
thicknesses for each coating comprised of PR 57:1 pigment sample
were 0.5 and 1 mil. The air-dried coatings on clear
Mylar.quadrature. film were then dried in a horizontal forced-air
oven at 100 .quadrature.C for 20 minutes.
Example 10
Evaluation of Coatings Prepared from Liquid Pigment Dispersions
[0135] The coatings on clear Mylar.quadrature.film prepared as
described in Example 9 were assessed for coloristic and light
scattering properties in the following manner: The UV/VIS/NIR
transmittance spectra of each coating were obtained using a
Shimadzu UV 160 spectrophotometer, and the results showed
dramatically reduced light scattering and remarkable specular
reflectivity for the nanosized PR 57:1 pigment samples described
herein, compared with the spectra of coatings prepared with
commercial PR 57:1 pigment samples obtained from Clariant and
Aakash. The degree of light scattering in a coating is dependent on
both the size and shape distributions of the pigment particles and
their relative dispersability within the coating matrix, and the
Normalized Light Scatter Index (NLSI) was developed to be a measure
of this characteristic for the pigmented coatings. NLSI is
quantified by first measuring the spectral absorbance of the
coating in a region where there is no absorbance from the chromogen
of the monoazo laked pigment (for PR 57:1, a suitable region is
700-900 nm), but only absorbance due to light scattered from large
aggregates and/or agglomerated pigment particles dispersed in the
coating binder. The Normalized Light Scatter Index (NLSI) is then
obtained by normalizing each of the samples' light scattering
indices (from 700 to 900 nm) to a lambda-max optical density=1.5.
In this way, the degree of light scattering for each pigmented
coating could be compared directly against each other. The lower
the NLSI value, the smaller the inferred particle size of the
dispersed pigment in the coating. A relationship between decreasing
average particle size and decreasing NLSI value was found to exist
with the coatings prepared from the example pigments shown in Table
8. In particular, the nanosized monoazo laked pigment PR 57:1 of
Example 3 had by far the lowest degree of light scattering, with an
NLSI value of 0.3. The coloristic properties of the Mylar coatings
were determined using an X-RITE 938 spectrodensitometer. L*a*b* and
optical density (O.D.) values were obtained for each of the
samples, and the L*a*b* were normalized to an optical density of
1.5, and used to calculate the hue angle and chroma (c*), as listed
in Table 8.
TABLE-US-00008 TABLE 8 Normalized Light Scatter Indices (NLSI) and
Coloristic properties of example PR 57:1 pigments, normalized to
O.D. = 1.5 Clariant L7B Aakash Comparative Metric 01 PR57:1 Example
Example 7 Example 3 Example 8 Example 4 Example 5 Example 6 L* 47.9
48.0 44.8 49.9 50.8 49.6 50.6 51.7 53.0 a* 71.1 71.2 71.5 76.7 76.5
73.6 77.2 79.4 78.8 b* 8.7 17.5 34.8 -18.9 -16.4 1.4 -17.4 -18.8
-15.0 Hue Angle (.degree.) 6.6 13.8 28.1 346.1 347.9 0.9 347.1
346.6 349.2 C* 72.6 73.4 78.1 78.9 78.6 73.9 77.5 81.3 80.5
Normalized 5.5 9.9 74.1 0.9 0.3 4.8 1.3 1.0 0.7 Light Scatter
Index
Example 11
b*a* Coloristic Properties of Coatings Prepared from Liquid Pigment
Dispersions
[0136] The graphs in FIGS. 1 and 2 visually illustrate the
tremendous shifts in b*a* gamut observed with coatings prepared
with the nanosized PR 57:1 pigments from Examples 3, 4, 5, 6, and
7, in addition to the extended c* chroma for the nanosized pigment
examples. Furthermore, the graph in FIG. 1 shows a clear
blue-shifting of hue that directly corresponds to decreasing
particle size/particle diameters of the example PR 57:1 pigments, a
relationship which is also inferred from the Normalized Light
Scatter Index (NLSI) values of Table 8. (Note: For ease of
generating the graph, the b* vertical axis shows "negative" hue
angles, which represent the number of degrees <360 degrees.) The
light scattering and coloristic data accumulated provide evidence
for the ability to tune color properties and specular reflectivity
of pigmented coatings with tunable particle size of
surface-enhanced pigment particles, by way of a facile bottom-up
chemical process for making monoazo laked pigments, in particular
Pigment Red 57:1, using sterically bulky stabilizer to limit
particle aggregation and therefore limit particle size as well as
enhance dispersion characteristics. Furthermore, the ability to
easily tune color properties of such monoazo laked pigments
provides a means to control the color quality so that inexpensive
azo laked pigments like PR 57:1 can be used to obtain magenta color
that are normally exhibited by higher cost red pigments, such as
the quinacridone Pigment Red 122 and Pigment Red 202.
Example 12
Composition of UV-Curable Liquid Pigment Dispersion Containing
Nanosized Pigment
[0137] Several dispersions were made using the PR 57:1 example
pigment as described in Example 5. In a 30 mL amber bottle, 0.129 g
Solsperse 34750 (50% active dispersant component in ethyl acetate,
available from Noveon) were added to 8.14 g SR-9003 (propoxylated
neo-pentyl glycol diacrylate, available from Sartomer Corporation)
and mixed to allow dissolution of the dispersant. To the bottle was
added 70.0 g of 1/8'' 440C Grade 25 stainless steel balls
(available from Hoover Precision Products) followed by 0.252 g of
nanosized PR 57:1 pigment as prepared in Example 5. Another
dispersion preparation was prepared in an identical manner except
0.336 g of Solsperse 34750 was used. The bottles were transferred
to a jar mill where they were ball-milled for 4 days at .about.120
RPM. At the end of the milling cycle, aliquots from the resultant
dispersions showed excellent flow behavior and thermal stability at
85.degree. C. where no particle settling was observed for at least
3 weeks.
Example 13
Composition of UV-Curable Liquid Pigment Dispersion Containing
Nanosized Pigment (by Attrition Technique)
[0138] 1800.0 g of 1/8'' 440C Grade 25 stainless steel balls
(available from Hoover Precision products) were added to a jacketed
Szegvari 01 attritor, followed by a prepared solution of 5.52 g
Solsperse 34750 dispersant in 165.83 g SR-9003 monomer. 5.13 g of
the nanosized PR 57:1 pigment as described in Example 5 were then
slowly added to the attritor. The attritor motor speed was adjusted
so that the impeller tip speed was .about.6.5 cm/s. The dispersion
was attrited for 19 hours. The attritor was kept cool at 20.degree.
C. by a recirculating bath. For recovery of the dispersion in the
attritor, a solution of 0.76 g Solsperse 34750 in 27.71 g SR-9003
was slowly added drop-wise to the attritor with the impeller now
turning at 200 RPM. 290.4 g of 1/8'' 440C Grade 25 stainless steel
balls were slowly added to the attritor during this mixing interval
to maintain the same volume of stainless steel balls to liquid
vehicle. The diluted dispersion was allowed to attrite for 3 hours.
178.9 g of the dispersion was recovered from the attritor once
separated from the stainless steel balls.
Example 14
Filtration of Attrited UV-Curable Liquid Pigment Dispersion
[0139] The attrited dispersion from Example 13 was filtered in
order to quantitatively ascertain the degree of dispersion and the
dispersion stability. 150 g of the recovered attrited dispersion
was filtered at 85.quadrature.C past a 2 .mu.m absolute glass fiber
filter (available from Pall Corporation) in a 70 mm Mott filtration
apparatus (available from Mott Corporation) using 2 psid applied
pressure of Nitrogen. The dispersion was then filtered at
85.quadrature.C past a 1 .mu.m absolute glass fiber filter
(available from Pall Corporation) in a 47 mm KST filtration
apparatus (available from Advantec Corporation) using 40 KPa
applied pressure of Nitrogen. The filtration data of permeate
weight over time in 1 second intervals was recorded by computer.
The dispersion permeate past 1 .quadrature.m filter was allowed to
remain standing for 12 days at room temperature upon which time it
was re-filtered past a 1.quadrature.m absolute glass fiber filter
at 85.quadrature.C. The filtration times of the as-prepared and
12-day aged dispersions were 16 and 14 seconds, respectively.
Example 15
Thermal Stability of Attrited UV-Curable Liquid Pigment
Dispersions
[0140] 1 g aliquots of the pigment dispersions prepared in Example
13 were held in an oven at 85.degree. C. and were observed to be
stable for 3 to 4 weeks with no indication of pigment particle
settling nor apparent change in viscosity. 1 g aliquots of the same
pigment dispersions prepared in Example 13 were left to stand at
room temperature, and were observed to be stable beyond 18 months
with no indication of settling or change in viscosity.
Example 16
Composition of UV Curable Ink Containing Nanosized Pigment
[0141] I. Preparation of UV-Curable Liquid Pigment Dispersion by
Attrition
[0142] 1800.0 g 1/8'' 440C Grade 25 stainless steel balls
(available from Hoover Precision products) are added to a jacketed
Szegvari 01 attritor followed by a pre-dissolved solution of 13.40
g Solsperse 34750 in 165.83 g SR-9003 (propxylated neopentyl glycol
diacrylate, available from Sartomer Company). 20.10 g of nanosized
PR 57:1 pigment sample obtained from two replicate batches prepared
as in Example 4 was slowly added to the attritor. The attritor
motor speed is adjusted so that the impeller is turning at 150 RPM.
The attritor is kept cool at 20 C by a recirculating bath, and is
allowed to stir at 150 RPM overnight. For recovery of the
dispersion in the attritor, a solution of 1.47 g Solsperse 34750 in
35.23 g SR-9003 is slowly added dropwise to the attritor with the
impeller now turning at 200 RPM. 308.1 g of 1/8'' 440C Grade 25
stainless steel balls are slowly added to the attritor during this
mixing interval as the solution is added to maintain the same
volume of stainless steel balls to liquid vehicle. The diluted
dispersion is allowed to attrite for 3 hours. The dispersion is
recovered from the attritor and separated from the steel balls.
[0143] II. Preparation of UV-Curable Ink Composition with Nanosized
Pigment
[0144] For the making of a working UV ink, a homogeneous solution
consisting of 20.00 g SR-9003, 10.00 g Xerox-proprietary amide
gallant (U.S. Patent Publication No. 2007/123722, the entire
disclosure of which is incorporated herein by reference), 2.45 g
Darocur ITX, 3.71 g Irgacure 127, 1.21 g Irgacure 819, 3.71 g
Irgacure 379, and 0.24 g Irgastab UV10 (all of which are available
from Ciba Geigy) is made at 85 C. 110.0 g of the dispersion
described above in this example is placed in a 600 mL glass beaker
in an oven at 85.degree. C. and is diluted with 41.32 g of the
UV-curable homogeneous solution in this example and mixed for 2
hours. The resulting UV-curable gel ink composition comprised of
nanosized PR 57:1 pigment shows nearly Newtonian behavior by shear
rate sweep determination using an RFS-3 rheometer from Rheometrics
Scientific, indicating the nanoparticles in the UV ink are properly
dispersed.
[0145] 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.
* * * * *
References