U.S. patent application number 14/328625 was filed with the patent office on 2016-01-14 for magnetic actuated-milled pigment dispersions and process for making thereof.
This patent application is currently assigned to XEROX CORPORATION. The applicant listed for this patent is XEROX CORPORATION. Invention is credited to SANDRA J. GARDNER, HARRY LATCHMAN, Frank Ping Hay Lee, YULIN WANG, KE ZHOU.
Application Number | 20160008820 14/328625 |
Document ID | / |
Family ID | 55066758 |
Filed Date | 2016-01-14 |
United States Patent
Application |
20160008820 |
Kind Code |
A1 |
ZHOU; KE ; et al. |
January 14, 2016 |
MAGNETIC ACTUATED-MILLED PIGMENT DISPERSIONS AND PROCESS FOR MAKING
THEREOF
Abstract
The disclosure provides pigment dispersions having an average
particle size of from about 10 nm to about 500 nm prepared by
employing a magnetic actuated milling process and system. In
embodiments, the pigment dispersions have an average particle size
of less than 100 nm.
Inventors: |
ZHOU; KE; (Oakville, CA)
; Lee; Frank Ping Hay; (Oakville, CA) ; LATCHMAN;
HARRY; (Mississauga, CA) ; WANG; YULIN;
(Oakville, CA) ; GARDNER; SANDRA J.; (Oakville,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
XEROX CORPORATION |
NORWALK |
CT |
US |
|
|
Assignee: |
XEROX CORPORATION
|
Family ID: |
55066758 |
Appl. No.: |
14/328625 |
Filed: |
July 10, 2014 |
Current U.S.
Class: |
106/496 ;
241/30 |
Current CPC
Class: |
C09D 17/001 20130101;
C09D 17/003 20130101; B02C 17/005 20130101 |
International
Class: |
B02C 17/00 20060101
B02C017/00; C09D 17/00 20060101 C09D017/00 |
Claims
1. A pigment dispersion comprising a milled pigment having an
average particle size of from about 10 nm to about 500 nm dispersed
in an aqueous medium, wherein the pigment dispersion is prepared
from the method comprising: contacting a pigment with magnetic
particles and non-magnetic abrasive particles; agitating the
pigment, and non-magnetic abrasive particles; applying a constant
magnetic field to the magnetic particles; milling the pigment with
the magnetic and the non-magnetic abrasive particles until the
average particle size is within the desired range of from about 10
nm to about 500 nm.
2. The pigment dispersion of claim 1, wherein the pigment
dispersion has a viscosity of from about 0.1 cP to about 100,000 cP
at 25.degree. C.
3. The pigment dispersion of claim 1, wherein the magnetic
particles are selected from the group consisting of a paramagnetic
material, ferromagnetic material, antiferromagnetic material and
mixtures thereof.
4. The pigment dispersion of claim 1, wherein the non-magnetic
abrasive particles have a particle diameter size of less than 1
mm.
5. The pigment dispersion of claim 1, wherein the non-magnetic
abrasive particles are selected from the group consisting of
aluminum oxide, SiC, cerium oxide, zirconium oxide, ferric oxide,
bauxite, cubic zirconia powder, diamond powder, and mixtures
thereof.
6. The pigment dispersion of claim 1, wherein the non-magnetic
abrasive particles have a nano indentation hardness value of at
least 4.9 GPa.
7. The pigment dispersion of claim 1, wherein the weight ratio of
magnetic particles to non-magnetic abrasive particles is in a range
of from about 0.5:10 to about 10:0.5.
8. The pigment dispersion of claim 1, wherein the volume ratio of
the magnetic particles and non-magnetic abrasive particles to the
pigment is in a range of from about 0.5:10 to about 10:0.5.
9. The pigment dispersion of claim 1, wherein the weight of the
milled pigment is from about 1 to about 50% by weight of the
pigment dispersion.
10. The pigment dispersion of claim 1, wherein the pigment
dispersion comprises water.
11. The pigment dispersion of claim 1, wherein the magnetic field
has a strength of from about 10 Gauss to about 50,000 Gauss.
12. The pigment dispersion of claim 1, wherein the magnetic field
is applied through one or more electromagnets.
13. The pigment dispersion of claim 1, wherein the magnetic field
is applied through a permanent magnet.
14. A pigment dispersion comprising a milled yellow pigment having
an average particle size of from about 10 nm to about 100 nm
dispersed in an aqueous medium, wherein the pigment dispersion is
prepared from the method comprising: contacting a yellow pigment
with magnetic particles and non-magnetic abrasive particles;
applying a constant magnetic field to the magnetic particles;
milling the yellow pigment with the magnetic and the non-magnetic
abrasive particles until the average particle size is less than 100
nm, wherein the milled yellow pigment has an average particle size
of from about 50 nm to about 95 nm.
15. The pigment dispersion of claim 14, wherein the pigment
dispersion has a viscosity of from about 0.1 cP to about 100,000
cP.
16. The pigment dispersion of claim 14, wherein the pigment
comprises
2-((2-methoxy-4-nitrophenyl)azo)-n-(2-methoxyphenyl)-3-oxo-butanamid.
17. (canceled)
18. The pigment dispersion of claim 14, wherein the weight of the
milled pigment is from about 1 to about 50% by weight of the
pigment dispersion.
19. The pigment dispersion of claim 14, wherein the constant
magnetic field has a strength of from about 10 Gauss to about
50,000 Gauss.
20. The pigment dispersion of claim 14, wherein the constant
magnetic field is applied through a permanent magnet.
Description
BACKGROUND
[0001] Pigments are typically the more costly components of ink and
toner. The cost of the conventional pigment dispersion process, in
some instances, can reach as high as about 50% of the total cost of
the pigment dispersion. Conventional pigment dispersion processes
are very costly and energy intensive, which is time consuming and
require frequent parts replacement and instrument maintenance.
[0002] The disclosure provides a cost effective process to prepare
pigment dispersion by employing a method and system for magnetic
actuated mixing which use magnetic particles and electromagnetic
field to facilitate milling of different materials. In embodiments,
the magnetic actuated mixing method can prepare ultrafine pigment
dispersions having a pigment particle size of less than 100 nm.
[0003] It is known in the pigment art that the smaller the pigment
particle size, the higher the color strength is produced. The color
strength is an essential property of pigments. It defines the
amount of pigment necessary to obtain a desired color shade. To
reduce cost, the industry tends to achieve the most color strength
from using the least possible amount of pigments. Thus, pigment
loading can be reduced by using smaller particles pigment. Smaller
pigment particles also provide better saturation, gloss, hiding
power, dispersion, flow, and help prevent print head congestion.
Thus, it is desirable to reduce the size of the pigment
dispersions.
[0004] In the present embodiments, the mixing of materials uses the
step of milling. Milling is the process of breaking down material
and thus involves particle size reduction. The magnetic particles
act as milling media. The system includes non-magnetic abrasive
particles in the milling media to facilitate the milling. The
present embodiments may be used in many different applications,
including for example, preparing toners, inks, wax, pigment
dispersions, paints, photoreceptor materials and the like. The
present embodiments may be used for any application that requires
the preparation of small-sized particles at either the micro or
nano scale.
[0005] In many batch processes, the milling step is one of most
critical steps to determine the overall performance of the process.
For example, in applications where small-sized particles are
produced, achieving the small scale and uniform distribution of the
particles is determined by the milling step.
SUMMARY
[0006] The present disclosure provides a pigment dispersion
comprising a milled pigment having an average particle size of from
about 10 nm to about 500 nm dispersed in an aqueous medium, wherein
the pigment dispersion is prepared from the method comprising
contacting a pigment with magnetic particles and non-magnetic
abrasive particles; agitating the pigment, and non-magnetic
abrasive particles; applying a constant magnetic field to the
magnetic particles; milling the pigment with the magnetic and the
non-magnetic abrasive particles until the average particle size is
within the desired range of from about 10 nm to about 500 nm.
[0007] In certain embodiment, the disclosure provides a pigment
dispersion comprising a milled yellow pigment having an average
particle size of from about 10 nm to about 100 nm dispersed in an
aqueous medium, wherein the pigment dispersion is prepared from the
method comprising contacting a yellow pigment with magnetic
particles and non-magnetic abrasive particles; applying a constant
magnetic field to the magnetic particles; milling the yellow
pigment with the magnetic and the non-magnetic abrasive particles
until the average particle size is less than 100 nm.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] For a better understanding of the present embodiments,
reference may be made to the accompanying figures.
[0009] FIG. 1 is a diagram of a magnetic actuated mixing system in
accordance with the present embodiments;
[0010] FIG. 2 is a graph illustrating the particle size and
particle size distribution of a pigment dispersion prior to
magnetic milling in accordance with the present embodiments;
[0011] FIG. 3 is a Transmission Electron Microscopy (TEM) image of
a pigment dispersion prior to magnetic milling in accordance with
the present embodiments;
[0012] FIG. 4 is a graph illustrating the change of particle size
of a pigment dispersion during the magnetic milling in accordance
with the present embodiments;
[0013] FIG. 5 is a graph illustrating the particle size and
particle size distribution of a pigment dispersion after the
magnetic milling in accordance with the present embodiments;
[0014] FIG. 6 is a TEM image of a pigment dispersion after the
magnetic milling in accordance with the present embodiments;
[0015] FIG. 7 is a graph illustrating the particle size and
particle size distribution of a pigment dispersion (scale up) after
the magnetic milling in accordance with the present embodiments;
and
[0016] FIG. 8 is a graph illustrating the particle size and
particle size distribution of a two-month old pigment dispersion
(scale up) after the magnetic milling in accordance with the
present embodiments.
DETAILED DESCRIPTION
[0017] In the following description, reference is made to the
accompanying drawings, which form a part hereof and which
illustrate several embodiments. It is understood that other
embodiments may be utilized and structural and operational changes
may be made without departure from the scope of the present
disclosure. The same reference numerals are used to identify the
same structure in different figures unless specified otherwise. The
structures in the figures are not drawn according to their relative
proportions and the drawings should not be interpreted as limiting
the disclosure in size, relative size, or location.
[0018] The term "D50" used herein refers to the 50th percentile of
the particle size distribution, wherein 50% of the particles in the
distribution are greater than the D50 particle size value and the
other 50% of the particles in the distribution are less than the
D50 value. Average particle size data can be measured by methods
that use light scattering technology to infer particle size, such
as Dynamic Light Scattering.
[0019] The present embodiments provide pigment dispersions prepared
by employing a magnetic actuated milling process and system which
use magnetic particles, non-magnetic abrasive particles and a
magnetic field to facilitate the milling.
[0020] The magnetic actuated milling process and system of the
embodiments employ a constant magnetic field across a mixing vessel
that contains pigments, magnetic particles, and non-magnetic
abrasive particles in a medium (e.g., solvents) with agitation.
[0021] In embodiments, as shown in FIG. 2, there is provided a
mixing system 45 comprising magnetic particles 50 and non-magnetic
abrasive particles 75 loaded in a solution containing pigments 55
which is moved to actuate milling by a constant magnetic field 60
applied to the magnetic particles 50. The magnetic particles may be
pre-loaded or filled into the milling vessel 70 when milling is
needed. A constant magnetic field 60 may be applied through one or
more electromagnets, or a permanent magnet 65 on either side of the
milling vessel 70. The magnetic fields may be stationary or moving.
The magnetic field may have a strength of from about 10 Gauss to
about 50,000 Gauss, or from about 50 Gauss to about 20,000 Gauss,
from about 100 Gauss to about 15,000 or from about 200 Gauss to
about 10,000 Gauss. The pigment and the non-magnetic abrasive
particles 75 may be agitated during parts of or during the entire
milling process. During agitation, the magnetic particles 50 may be
relatively stationary due to the influence of the constant magnetic
field 60. However, the magnetic particles 50 may be bounced and
moved slightly by the motion of the other particles in the
solution. The magnetic particles 50 may collide with the pigment
particles 55 and the non-magnetic abrasive particles 75. The mixing
system 45 achieves intense micro mixing zone 75 uniformly
throughout the mixing vessel 70. The agitation may be performed in
any suitable agitating means. For example, the vessel 70 may be
spun or shaken, or a stirrer may be added to the vessel 70 to mix
the pigment dispersion. The agitation may be performed in the range
of from about 50 to about 10,000 rpm, or from about 100 to about
5,000 rpm. The magnetic particles can be successfully collected and
recycled by electromagnets for subsequent applications. The
non-magnetic particles may be removed by any method including
filtering, centrifuging, and the like.
[0022] The magnetic particles may be include diamagnetic,
paramagnetic, ferrimagnetic, ferromagnetic or antiferromagnetic
materials such that the overall magnetic particle is paramagnetic,
ferrimagnetic, ferromagnetic or antiferromagnetic. In some
exemplary embodiments, the magnetic particles may comprise Fe,
Fe.sub.2O.sub.3, Ni, CrO.sub.2, or Cs. In specific embodiments, the
magnetic particles include carbonyl iron and carbonyl nickel. In
embodiments, the magnetic particles may have a non-magnetic
coating. In other embodiments, the magnetic particles can also be
encapsulated with a shell, for example, a polymeric shell
comprising, in embodiments, polystyrene, polyvinyl chloride,
TEFLON.RTM., PMMA, and the like and mixtures thereof. The magnetic
particles may have a diameter of from about 5 nm to about 1000
.mu.m, or from about 10 nm to about 500 .mu.m, or from about 100nm
to about 100 .mu.m. The size of magnetic particles can be chosen
based on different applications or processes. In embodiments, the
volume percentage of magnetic particles used for mixing may also
vary depending on the different application or process for which
the particles are being used. For example, from about 5% to about
80%, or from about 10% to about 50%, or from about 15% to about 25%
magnetic particles may be added to the vessel.
[0023] It was discovered that the addition of non-magnetic abrasive
particles to the milling media provided a better actuated milling.
The non-magnetic abrasive particles, like those used as polishing
abrasives in the magnetorheological finishing industry, are hard
micron-sized materials responsible for material size reduction (for
example, see Nanoindentation Hardness of Particles Used in
Magnetorheological Finishing (MRF) Aric B. Shorey, Kevin M. Kwong,
Kerry M. Johnson, and Stephen D. Jacobs Applied Optics, Volume 39,
Issue 28 (2000)). These abrasive particles have hardness values
that exceed those of magnetic particles. When used in conjunction
with the magnetic particles, the non-magnetic abrasive particles
provide even more effective results in solid particle size
reduction, especially in grinding certain pigment particles. The
collision and shearing between the magnetic particles and
non-magnetic abrasive particles and not only achieve the desired
small scale and uniform distribution of the mixed particles, but to
do so quickly. The non-magnetic particles may be later removed by
any method including filtering, screening, centrifuging, and the
like. While the use of the non-magnetic abrasive particles does add
to the system components and process steps, the smaller particle
sizes achieved outweigh any drawbacks.
[0024] The non-magnetic abrasive particles may comprise one or more
of aluminum oxide, silicon carbide, cerium oxide, zirconium oxide,
ferric oxide, bauxite, cubic zirconia and diamond powder, and the
like and mixtures thereof. In embodiments, the abrasive particles
may have a diameter of less than 1 mm. In other embodiments, the
abrasive particles may have a diameter of from about 5 nm to about
1000 .mu.m, or from about 10 nm to about 500 .mu.m, or from about
100 nm to about 100 .mu.m. The size of non-magnetic abrasive
particles can be chosen based on different applications or
processes. The non-magnetic abrasive particles have a nano
indentation hardness value of at least 4.9, or from about 5 to
about 50, or from about 7.5 to about 50 GPa. The non-magnetic
abrasive particles may have any regular or irregular shape
including spherical, cubic, hexagonal, rod-shaped, granular,
elliptical, flake, and the like and mixtures thereof. In
embodiments, the volume percentage of non-magnetic abrasive
particles (based on the total dry volume of the milling media) used
for milling may also vary depending on the different application or
process for which the particles are being used. For example, from
about 5% to about 95%, or from about 10% to about 80%, or from
about 20% to about 70% non-magnetic abrasive particles may be added
to the vessel.
[0025] In specific embodiments, a weight ratio of magnetic
particles to non-magnetic abrasive particles may be in a range of
from about 0.5:10 to about 10:0.5, or from about 1:10 to about
10:1, or from about 2:10 to about 10:2. In further embodiments, a
volume ratio of the total milling media (magnetic particles and
non-magnetic abrasive particles) to the material to be mixed may be
in a range of from about 0.5:10 to about 10:0.5, or from about 1:10
to about 10:1, or from about 2:10 to about 10:2.
[0026] In embodiments, the resulting particles sizes of the pigment
dispersions achieved by the actuated milling are from about 10 nm
to about 500 nm, from about 20 nm to about 400 nm, or from 50 nm to
about 300 nm. In embodiments, certain pigments may achieve even
smaller particles sizes of less than 100 nm, for example, from
about 10 nm to about 100 nm, from about 30 nm to about 95 nm, from
about 40 nm to about 95 nm, or from about 50 nm to about 95 nm.
[0027] If micro sized magnetic particles are used, due to the large
surface contact area between micro magnetic particles and the
solution, micro milling due to enhanced local diffusion
significantly produces homogeneous and global milling. The present
embodiments thus provide small particles on the nano to micro scale
and uniform distribution. The present embodiments also provide for
the potential of higher viscosity (for example, a viscosity of from
about 0.1 cP to about 100,000 cP, from about 0.5 cP to about 50000
cP, or from about 1 cP to about 10000 cP at 25.degree. C.) milling
if the exposed magnetic field is large.
[0028] Another advantage of the present method and system is the
fact that it is free of mechanical components and thus maintenance,
which significantly reduces the cost of the system. The present
embodiments are also free of noise.
[0029] The present embodiments may be used in many different
applications, including solids dispersions for example, preparing
toners, inks, wax, pigment dispersions and the like. The present
embodiments may be used for any application that requires the
preparation of small-sized particles at either the micro or nano
scale.
[0030] Pigment Dispersions
[0031] Pigment dispersions are often used in the preparation of EA
toners or inks. Conventional milling methods used for preparing
pigment dispersions suffer from many drawbacks. In addition, the
use of conventional milling methods consume lengthy periods of time
to prepare the pigment dispersions, often exceeding four hours.
[0032] The present embodiments provide for the use of magnetic
actuating motion of magnetic particles to prepare pigment
dispersions as provided by milling capabilities at nano or micro
scale. These embodiments apply a constant magnetic field to align
the magnetic particles. The magnetic particles may be agitated by
moving the magnetic field, where the magnetic source may be
arranged in a movable manner (e.g., rotatable or tiltable manner)
The motion of pigment particles and non-magnetic abrasive particles
may be driven by agitation via, for example, stirring or
homogenizing the solution, spinning or shaking of the vessel.
[0033] In one embodiment, the pigment particles and the
non-magnetic abrasive particles may be agitated, while the magnetic
particles may be stationary. In one embodiment, the pigment
particles and the non-magnetic abrasive particles may be
stationary, while the magnetic particles may be agitated. In one
embodiment, the pigment particles and the non-magnetic abrasive
particles may be agitated (by sirring or homogenize the solution,
or spinning or shaking motion of the vessel), while the magnetic
particles may be agitated (by influence of the movement of the
magnetic field). Different motions of magnetic particles and
non-magnetic particles, including the pigment particles and the
non-magnetic abrasive particles, provide consistent nano or micro
scale collision and shearing throughout the entire vessel, thus
providing uniform dispersion of materials within a very short time
frame (e.g., minutes).
[0034] In embodiments, a dry pigment may be loaded in a solvent
(i.e., pigment/solvent mixture), such as water, an organic solvent,
or mixtures thereof, into the vessel. In embodiments, the pigment
may include a blue pigment, a black pigment, a cyan pigment, a
brown pigment, a green pigment, a white pigment, a violet pigment,
a magenta pigment, a red pigment, an orange pigment, a yellow
pigment, or mixtures thereof.
[0035] Suitable pigments include those comprising carbon black,
such as, REGAL 330.RTM. and Nipex 35. Colored pigments, such as,
cyan, magenta, yellow, red, orange, green, brown, blue or mixtures
thereof can be used. The additional pigment or pigments can be used
as water-based pigment dispersions.
[0036] Examples of pigments include SUNSPERSE 6000, FLEXIVERSE and
AQUATONE, water-based pigment dispersions from SUN Chemicals;
HELIOGEN BLUE L6900.TM., D6840.TM., D7080.TM., D7020.TM., PYLAM OIL
BLUE.TM., PYLAM OIL YELLOW.TM. and PIGMENT BLUE I.TM. available
from Paul Uhlich & Company, Inc.; PIGMENT VIOLET I.TM., PIGMENT
RED 48.TM., LEMON CHROME YELLOW DCC IO26.TM., TOLUIDINE RED.TM. and
BON RED C.TM. available from Dominion Color Corporation, Ltd.,
Toronto, Ontario; NOVAPERM YELLOW FGL.TM. and HOSTAPERM PINK E.TM.
from Hoechst; CINQUASIA MAGENTA.TM. available from E.I. DuPont de
Nemours & Co., and the like.
[0037] Examples of magenta pigments include
2,9-dimethyl-substituted quinacridone, an anthraquinone dye
identified in the Color Index as CI 60710, CI Dispersed Red 15, a
diazo dye identified in the Color Index as CI 26050, CI Solvent Red
19 and the like.
[0038] Illustrative examples of cyan pigments include copper
tetra(octadecylsulfonamido) phthalocyanine, a copper phthalocyanine
pigment listed in the Color Index as CI 74160, CI Pigment Blue,
Pigment Blue 15:3, Pigment Blue 15:4, an Anthrazine Blue identified
in the Color Index as CI 69810, Special Blue X-2137 and the
like.
[0039] Illustrative examples of yellow pigments are diarylide
yellow 3,3-dichlorobenzidene acetoacetanilide, a monoazo pigment
identified in the Color Index as CI 12700, CI Solvent Yellow 16, a
nitrophenyl amine sulfonamide identified in the Color Index as
Foron Yellow SE/GLN, CI Disperse Yellow 3,
2,5-dimethoxy-4-sulfonanilide phenylazo-4'-chloro-2,5-dimethoxy
acetoacetanilide and Permanent Yellow FGL.
[0040] Other known colorants can be used, such as, Levanyl Black
A-SF (Miles, Bayer) and Sunsperse Carbon Black LHD 9303 (Sun
Chemicals), and colored dyes, such as, Neopen Blue (BASF), Sudan
Blue OS (BASF), PV Fast Blue B2G 01 (American Hoechst), Sunsperse
Blue BHD 6000 (Sun Chemicals), Irgalite Blue BCA (CibaGeigy),
Paliogen Blue 6470 (BASF), Sudan III (Matheson, Coleman, Bell),
Sudan II (Matheson, Coleman, Bell), Sudan IV (Matheson, Coleman,
Bell), Sudan Orange G (Aldrich), Sudan Orange 220 (BASF), Paliogen
Orange 3040 (BASF), Ortho Orange OR 2673 (Paul Uhlich), Paliogen
Yellow 152, 1560 (BASF), Lithol Fast Yellow 0991 K (BASF), Paliotol
Yellow 1840 (BASF), Neopen Yellow (BASF), Novoperm Yellow FG 1
(Hoechst), Permanent Yellow YE 0305 (Paul Uhlich), Lumogen Yellow
D0790 (BASF), Sunsperse Yellow YHD 6001 (Sun Chemicals), Suco-Gelb
L1250 (BASF), SUCD-Yellow D1355 (BASF), Hostaperm Pink E (American
Hoechst), Fanal Pink D4830 (BASF), Cinquasia Magenta (DuPont),
Lithol Scarlet D3700 (BASF), Toluidine Red (Aldrich), Scarlet for
Thermoplast NSD PS PA (Ugine Kuhlmann of Canada), E.D. Toluidine
Red (Aldrich), Lithol Rubine Toner (Paul Uhlich), Lithol Scarlet
4440 (BASF), Bon Red C (Dominion Color Company), Royal Brilliant
Red RD-8192 (Paul Uhlich), Oracet Pink RF (Ciba-Geigy), Paliogen
Red 3871 K (BASF), Paliogen Red 3340 (BASF), Lithol Fast Scarlet
L4300 (BASF), combinations of the foregoing and the like. Other
pigments that can be used, and which are commercially available
include various pigments in the color classes, Pigment Yellow 74
(2-((2-methoxy-4-nitrophenyl)azo)-n-(2-methoxyphenyl)-3-oxo-butanamid)-
, Pigment Yellow 14, Pigment yellow 93, Pigment yellow 34, Pigment
yellow 180, Pigment yellow 83, Pigment yellow 139, Pigment yellow
151, Pigment yellow 13, Pigment yellow 191, Pigment Orange 34,
Pigment Red 238, Pigment Red 122, Pigment Red 48:1, Pigment Red
269, Pigment Red 53:1, Pigment Red 57:1, Pigment Red 83:1, Pigment
Violet 23, Pigment Green 7 and so on, and combinations thereof.
[0041] In embodiments, the weight ratio of the pigment to solvent
in the pigment/solvent mixture may be from about 5/95 to about
80/20, from about 10/90 to about 50/50, or from about 15/85 to
about 20/80.
[0042] In embodiments, the weight of the milled pigment is from
about 1 to about 50%, from about 3 to about 45%, from about 5 to
about 40%, by weight based on the pigment dispersion.
[0043] A surfactant may be added to and mixed with the
pigment/solvent mixture in the vessel. In embodiments, the
surfactant can be water-soluble polymers, or water-soluble
surfactants. In embodiments, the surfactant is added in an amount
of from 1% to about 30%, or from about 3% to about 15%, or from
about 5% to about 12% by weight of the total weight of the mixture
in the vessel.
[0044] Any type of surfactant may be used, with anionic, cationic
or nonionic surfactants being utilized in some embodiments.
Examples of nonionic surfactants that can be utilized include, for
example, polyacrylic acid, methalose, methyl cellulose, ethyl
cellulose, propyl cellulose, hydroxy ethyl cellulose, carboxy
methyl cellulose, polyoxyethylene cetyl ether, polyoxyethylene
lauryl ether, polyoxyethylene octyl ether, polyoxyethylene
octylphenyl ether, polyoxyethylene oleyl ether, polyoxyethylene
sorbitan monolaurate, polyoxyethylene stearyl ether,
polyoxyethylene nonylphenyl ether, dialkylphenoxy poly(ethyleneoxy)
ethanol, available from Rhone-Poulenc Industries SA as IGEPAL
CA-21O.TM., IGEPAL CA-520.TM., IGEPAL CA-720.TM., IGEPAL
CO-890.TM., IGEPAL CO-720.TM., IGEPAL CO-290.TM., IGEPAL
CA-210.TM., ANTAROX 890.TM. and ANTAROX .sup.897.TM.. Other
examples of suitable nonionic surfactants include a block copolymer
of polyethylene oxide and polypropylene oxide, including those
commercially available as SYNPERONIC PE/F, in embodiments
SYNPERONIC PE/F 108.
[0045] Anionic surfactants which may be utilized include sulfates
and sulfonates, sodium dodecylsulfate (SDS), sodium dodecylbenzene
sulfonate, sodium dodecylnaphthalene sulfate, dialkyl benzenealkyl
sulfates and sulfonates, acids such as abitic acid available from
Aldrich, NEOGEN R.TM., NEOGEN SC.TM. obtained from Daiichi Kogyo
Seiyaku Co. Ltd., combinations thereof, and the like. Other
suitable anionic surfactants include, in embodiments, DOWFAX.TM.
2A1, an alkyldiphenyloxide disulfonate from The Dow Chemical
Company, and/or TAYCAPOWER BN2060 from Tayca Corporation, which are
branched sodium dodecyl benzene sulfonates. Combinations of these
surfactants and any of the foregoing anionic surfactants may be
utilized in embodiments.
[0046] Examples of the cationic surfactants, which are usually
positively charged, include, for example, alkylbenzyl dimethyl
ammonium chloride, dialkyl benzenealkyl ammonium chloride, lauryl
trimethyl ammonium chloride, alkylbenzyl methyl ammonium chloride,
alkyl benzyl dimethyl ammonium bromide, benzalkonium chloride,
cetyl pyridinium bromide, C.sub.12, C.sub.15, C.sub.17 trimethyl
ammonium bromides, halide salts of quaternized
polyoxyethylalkylamines, dodecylbenzyl triethyl ammonium chloride,
MIRAPOL.TM. and ALKAQUAT.TM., available from Alkaril Chemical
Company, SANIZOL.TM. (benzalkonium chloride), available from Kao
Corporation, and the like, and mixtures thereof.
[0047] In embodiments, an ultrafine pigment dispersions having an
average particle size of less than 100 nm can be prepared using the
magnetic actuated milling method and system of the present
disclosure. A magnetic field can be generated and applied to the
mixture and magnetic particles in the vessel. The magnetic field
for preparing ultrafine pigment dispersions may have a strength of
from about 200 Gauss to about 10,000 Gauss, or from about 100 Gauss
to about 10,000 Gauss. A pigment dispersion with the desired
particle size can be then achieved by different motions of the
magnetic particles nonmagnetic particles under the magnetic field
and agitation. A reduction in pigment particles can be achieved.
The duration and speed of milling may be dependent on the pigment
color and pigment particle size desired. Generally, the duration of
milling may range from about 0.01 to about 5000 hours, from about
0.1 to about 2000 hours, or from about 0.2 to about 1000 hours. A
longer milling may in some cases be necessary or desirable but the
process can in any particular instance be controlled by periodic
examination of a sample to ascertain when a product having the
desired particle characteristics and the like has been obtained. In
embodiments, to achieve the ultrafine pigment dispersions, the rate
of the agitation may range from about 50 to about 20,000 rpm, range
from about 100 to about 10,000 rpm. The magnetic particles and
non-magnetic abrasives abrasive particles can then be collected for
re-use.
[0048] While the description above refers to particular
embodiments, it will be understood that many modifications may be
made without departing from the spirit thereof. The accompanying
claims are intended to cover such modifications as would fall
within the true scope and spirit of embodiments herein.
[0049] The presently disclosed embodiments are, therefore, to be
considered in all respects as illustrative and not restrictive, the
scope of embodiments being indicated by the appended claims rather
than the foregoing description. All changes that come within the
meaning of and range of equivalency of the claims are intended to
be embraced therein.
EXAMPLES
[0050] The example set forth herein below is illustrative of
different compositions and conditions that can be used in
practicing the present embodiments. All proportions are by weight
unless otherwise indicated. It will be apparent, however, that the
embodiments 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. The embodiments will be
described in further detail with reference to the following
examples and comparative examples. All the "parts" and "%" used
herein mean parts by weight and % by weight unless otherwise
specified.
[0051] The example set forth herein below is illustrative of
different compositions and conditions that can be used in
practicing the present embodiments. All proportions are by weight
unless otherwise indicated. It will be apparent, however, that the
embodiments 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. The embodiments will be
described in further detail with reference to the following
examples and comparative examples. All the "parts" and "%" used
herein mean parts by weight and % by weight unless otherwise
specified.
Example 1
[0052] Preparation of Wetted Yellow Pigment Dispersion
[0053] 125.0 g Pigment PY74, 65.93 g surfactant ((18.75 wt %) tayca
power solution from Tayca Corporation), 201.53 g deionized water
(DIW) was mixed together in a 1 L glass bottle and stirred for
about 15 hours. The particle size and particle size distribution of
the wetted yellow pigment dispersion (i.e., the resulting mixture)
are shown in FIG. 2. The TEM image of the wetted yellow pigment
dispersion is shown in FIG. 3. The D50 of the wetted yellow pigment
dispersion was measured to be about 211 nm.
[0054] Magnetic Milling
[0055] Magnetic milling was conducted with magnetic particles and
non-magnetic abrasives. Into a 9 mL glass vial was added 2.66 g of
the wetted pigment dispersion obtained above, and 1.31 mL (3.25 g)
of 35 micron iron oxide magnetic particles and 1.31 mL (1.82 g) of
non-magnetic abrasives Al.sub.2O.sub.3 (<10 micron) at about
50:50 abrasive concentration. The abrasive concentrations were
calculated as follows:
Abrasive concentration = Abrasive Dry Volume Total Dry Volume of
Milling Media ##EQU00001##
[0056] The vial was then spinned using an agitator at 250 rpm
beside a permanent magnet having magnetic field about 400 mT. The
particle size of pigment was then measured at different time
interval. Table 1 summarizes the mean diameter of the yellow
pigment over the duration of the magnetic milling, and FIG. 4 shows
the change of particle size in time over the duration of the
magnetic milling.
TABLE-US-00001 TABLE 1 Time (h) Mean Diameter (micron) 0.0 0.211.1
0.25 0.1889 0.50 0.1758 1.00 0.1421 2.00 0.119 3.00 0.1064 4.50
0.0901 6.00 0.0814 16.00 0.0674
[0057] The particle size and particle size distribution of the
yellow pigment dispersion after magnetic milling is shown in FIG.
5. The TEM image of the yellow pigment dispersion after magnetic
milling is shown in FIG. 6.
Example 2
[0058] Preparation of Yellow Pigment Dispersion (Scale Up)
[0059] Magnetic milling was conducted with magnetic particles and
non-magnetic abrasives. Into a 85 ml glass bottle was added 45.8 g
of the wetted pigment dispersion obtained in Example 1, and 27.28 g
of 35 micron iron oxide magnetic particles and 13.22 g of
nonmagnetic abrasives Al.sub.2O.sub.3 (<10 micron) at about
50:50 abrasive concentration.
[0060] The vial was then spinned using an agitator at 75 rpm beside
a permanent magnet having magnetic field about 400 mT. The particle
size of pigment was then measured after spun overnight. The
particle size and particle size distribution of the resulting
yellow pigment dispersion are shown in FIG. 7. The data indicated
that the D50 of resulting yellow pigment dispersion is 85.9 nm,
with 95% of the particles smaller than 214.1 nm. TEM image also
indicated that the original rod shaped pigment particles were
broken into smaller particles
Example 3
[0061] Stability of Resulting Pigment Dispersion
[0062] After 2 months of storage in a sealed jar at room
temperature, the yellow pigment dispersion of Example 2 was remixed
and measured again. The particle size and particle size
distribution are shown in FIG. 8. The D50 of 2-month old yellow
pigment dispersion was measured to be 93.7 nm and 95% of particles
were smaller than 251 nm, which demonstrates good pigment
stability.
Comparative Example 4
[0063] Preparation of Carbon Black Pigment Dispersion
[0064] Into a 9 mL vial was added 0.85 g of carbon black pigment
powder Regal 330, 1.37 g of DIW, 0.45 g (18.75 wt %) tayca power
and 2.62 mL of 35 micron iron oxide and nonmagnetic abrasives
Al.sub.2O.sub.3 (<10 micron) at different abrasive
concentration.
[0065] The vial was then spun using an agitator at 400 rpm beside a
permanent magnet having magnetic field about 400 mT. The particle
size of pigment was then measured at different time interval until
particle size stabilized.
Comparative Examples 5 and 6
[0066] Comparative Examples 5 and 6 were prepared according to the
method described for Example 4, except that Cyan pigment PB15:3 and
magenta pigment PR122 was used respectively instead of carbon black
pigment. Table 2 shows the
TABLE-US-00002 TABLE 2 Mean Diameter (micron) of pigment
dispersions Time (h) Carbon black (regal 330) Cyan (PB15:3) Magenta
(PR122) 0.00 0.1861 0.2459 0.3150 0.04 0.1588 0.08 0.1411 0.1777
0.2506 0.17 0.1396 0.25 0.1349 0.1626 0.2176 0.33 0.1356 0.42
0.1316 0.50 0.1317 0.1542 0.2001 1.00 0.1333 0.1328 0.1954 1.50
0.1338 2.00 0.1297 0.1349 0.1682 2.50 0.1259 3.00 0.1291 0.1351
0.1756 16.00 0.1883
[0067] It will be appreciated that several 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. Unless specifically recited in a claim, steps or components
of claims should not be implied or imported from the specification
or any other claims as to any particular order, number, position,
size, shape, angle, color, or material.
* * * * *