U.S. patent application number 11/905751 was filed with the patent office on 2008-02-07 for method for preparing latex containing pigment copolymerized with a crystalline polymer.
This patent application is currently assigned to Samsung Electronics Co. of Republic of Korea. Invention is credited to Sang-woo Kim, Jun-Young Lee, Kyung-yol Yon.
Application Number | 20080032227 11/905751 |
Document ID | / |
Family ID | 34909913 |
Filed Date | 2008-02-07 |
United States Patent
Application |
20080032227 |
Kind Code |
A1 |
Lee; Jun-Young ; et
al. |
February 7, 2008 |
Method for preparing latex containing pigment copolymerized with a
crystalline polymer
Abstract
A method of preparing a latex that includes pigments
copolymerized with a crystalline polymer includes: dispersing a
pigment and a dispersing agent in water having an ultra-high purity
to obtain a pigment dispersion; dissolving a crystalline monomer in
a basic monomer mixture to obtain an organic phase; dissolving
while heating the dispersing agent in water having an ultra-high
purity, and then mixing the solution with the pigment dispersion to
obtain an aqueous phase; mixing and agitating the organic phase and
the aqueous phase to obtain a homogenized solution; agitating and
heating the homogenized solution; adding a polymerization initiator
to the homogenized solution to be reacted; and cooling the reaction
solution to room temperature.
Inventors: |
Lee; Jun-Young; (Seoul,
KR) ; Kim; Sang-woo; (Seoul, KR) ; Yon;
Kyung-yol; (Seongnam-si, KR) |
Correspondence
Address: |
STAAS & HALSEY LLP
SUITE 700
1201 NEW YORK AVENUE, N.W.
WASHINGTON
DC
20005
US
|
Assignee: |
Samsung Electronics Co. of Republic
of Korea
|
Family ID: |
34909913 |
Appl. No.: |
11/905751 |
Filed: |
October 3, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11037068 |
Jan 19, 2005 |
7307129 |
|
|
11905751 |
Oct 3, 2007 |
|
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|
Current U.S.
Class: |
430/137.15 |
Current CPC
Class: |
G03G 9/08708 20130101;
G03G 9/08702 20130101; G03G 9/09 20130101; G03G 9/08795 20130101;
G03G 9/08726 20130101; G03G 9/08722 20130101; G03G 9/0806
20130101 |
Class at
Publication: |
430/137.15 |
International
Class: |
G03G 9/13 20060101
G03G009/13 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 20, 2004 |
KR |
2004-4418 |
Claims
1. A method of preparing a latex, comprising: copolymerizing
pigments with a crystalline polymer in one process in a reaction
solution without a separate aggregation process to facilitate
control of amounts and aggregation of each component in the latex
and provide the latex with a minimized particle size distribution,
wherein the crystalline polymer material acts as a mold release
agent and has a lower melting point than a melting point of the
latex, when prepared; and cooling the reaction solution.
2. The method of preparing a latex of claim 1, wherein a pigment
and a dispersing agent are dispersed in water having an ultra-high
purity to obtain a pigment dispersion and the dispersing agent used
in the dispersing the pigment and the dispersing agent in water is
an anionic surfactant selected from the group consisting of a
carboxylate, an ester sulfate and a sulfonate; or a non-ionic
surfactant selected from the group consisting of a polyoxyethylene
alkylether, a polyoxyethylene alkylphenylether, a polyoxyethylene
fatty acid ester, a sorbitan fatty acid ester, a polyoxysorbitan
fatty acid ester, a polyoxyethylene alkylamine and an
oxyethyleneoxypropylene block copolymer.
3. The method of preparing a latex of claim 2, wherein the pigment
dispersion in the dispersing the pigment and the dispersing agent
in water is prepared by agitating at a speed of 2,000 to 10,000 rpm
for 1 to 5 hours.
4. The method of preparing a latex of claim 3, wherein a
crystalline monomer is dissolved in a basic monomer mixture to
obtain an organic phase and the basic monomer mixture is a mixture
of an aromatic-based vinyl monomer selected from the group
consisting of a styrene, an o-methyl styrene, an m-methyl styrene,
a p-methyl styrene, a p-methoxy styrene, a p-phenyl styrene, a
p-chloro styrene, a p-ethyl styrene, a p-n-butyl styrene, a
p-tert-butyl styrene, a p-n-hexyl styrene, a p-n-octyl styrene, a
p-n-nonyl styrene, a p-n-decyl styrene, a p-n-dodecyl styrene, a
2,4-dimethyl styrene, a 3,4-dichloro styrene and their derivatives;
a (meth)acrylic acid ester-based monomer selected from the group
consisting of an acrylic acid methyl, an acrylic acid ethyl, an
acrylic acid butyl, an acrylic acid-2-ethyl hexyl, an acrylic acid
cyclohexyl, an acrylic acid phenyl, a methacrylic acid methyl, a
methacrylic acid ethyl, a methacrylic acid butyl, a methacrylic
acid hexyl, a methacrylic acid-2-ethyl hexyl, .beta.-hydroxy
acrylic acid ethyl, .gamma.-amino acrylic acid propyl, a
methacrylic acid stearyl, a methacrylic acid dimethyl amino ethyl,
a methacrylic acid diethyl amino ethyl and their derivatives; a
vinyl ester-based monomer selected from the group consisting of an
acetic acid vinyl, a propionic acid vinyl, a benzoic acid vinyl and
their derivatives; a vinyl ether-based monomer selected from the
group consisting of a vinyl methyl ether, a vinyl ethyl ether, a
vinyl isobutyl ether, a vinyl phenyl ether and their derivatives; a
monoolefine-based monomer selected from the group consisting of an
ethylene, a propylene, an isobutylene, a 1-butene, a 1-pentene, a
4-methyl-1-pentene and their derivatives; a diolefine-based monomer
selected from the group consisting of a butadiene, an isoprene, a
chloroprene and their derivatives; and a halogenated olefine-based
monomer selected from the group consisting of a vinyl chloride, a
vinylidene, chloride, a vinyl fluoride and their derivatives.
5. The method of preparing a latex of claim 4, wherein the
crystalline monomer has 18 to 32 carbon atoms, and a melting point
of 30.degree. C. to 70.degree. C.
6. The method of preparing a latex of claim 4, wherein the
crystalline monomer forms a crystalline polymer by copolymerization
with the basic monomer, and the amount of the crystalline polymer
in the latex is 1 to 50 parts by weight based on 100 parts by
weight of the latex.
7. The method of preparing a latex of claim 4, wherein the basic
monomer forms a polymer material having a glass transition
temperature of 40.degree. C. to 100.degree. C. by polymerization,
and the crystalline monomer forms a crystalline polymer material
having a melting point of 30.degree. C. to 80.degree. C. by
copolymerization with the basic monomer.
8. The method of preparing a latex of claim 4, wherein a dispersing
agent is dissolved, while heating, in water having an ultra-high
purity to form a solution, and then the solution is mixed with the
pigment dispersion to form an aqueous phase, wherein the dispersing
agent is a non-ionic surfactant selected from the group consisting
of a polyoxyethylene alkyl ether, a polyoxyethylene alkyl phenyl
ether, a polyoxyethylene fatty acid ester, a sorbitan fatty acid
ester, a polyoxy sorbitan fatty acid ester, a polyoxyethylene alkyl
amine and an oxyethyleneoxypropylene block copolymer.
9. The method of preparing a latex of claim 8, wherein the organic
phase and the aqueous phase are mixed and agitated to achieve
homogenization, and the mixing and agitation is carried out at an
agitation speed of 1,000 to 7,000 rpm for 1 to 60 min.
10. The method of preparing a latex of claim 9, wherein the
agitation speed in the agitating and heating the homogenized
solution is 100 to 800 rpm, and the heating temperature is
50.degree. C. to 80.degree. C.
11. The method of preparing a latex of claim 10, wherein a
polymerization initiator is added to the homogenized solution and
is a water-soluble polymerization initiator selected from the group
consisting of a persulfate, an azo based compound and a peroxide
compound.
12. The method of preparing a latex of claim 11, wherein the
polymerization initiator is used in 1 to 5 parts by weight based on
100 parts by weight of the homogenized solution.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of U.S. patent
application Ser. No. 11/037,068 filed Jan. 19, 2005, which has been
allowed. This application is based upon and claims priority form
U.S. patent application Ser. No. 11/037,068, filed Jan. 19, 2005,
the contents being incorporated herein by reference, and claims
priority based on Korean Patent Application No. 2004-4418, filed on
Jan. 20, 2004, in the Korean Intellectual Property Office, the
disclosure of which is incorporated herein in its entirety by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a method for preparing a
latex containing pigments copolymerized with a crystalline polymer,
and more particularly, a method for preparing a latex containing
pigments copolymerized with a crystalline polymer by which a latex
containing pigments copolymerized with a crystalline polymer is
prepared in one process without requiring a separate aggregation
process, and a low fusing temperature is implemented by
substituting a crystalline polymer material having a low melting
point of the prepared latex for a mold release agent.
[0004] 2. Description of the Related Art
[0005] A conventional toner used in an electrophotographic imaging
apparatus comprises a resin, a pigment, a charge control agent and
a mold release agent. Of these components, the resin constitutes
about 90% by weight of the total weights of a toner, and plays a
role in attaching a toner particle to paper, and the like. A
pigment embodies a color, and a charge control agent controls the
charges of a toner to assist a toner particle in forming an image
efficiently. Finally, a mold release agent enhances the release
between a roller and a toner on fusing a toner to prevent an offset
and or paper jam.
[0006] Such a toner particle may be largely categorized into a
pulverized toner prepared by a pulverizing method and a polymerized
toner prepared by polymerization. The former is a classical method,
and a coloring agent, a charge control agent (CCA) and a mold
release agent are melted and dispersed uniformly in a binder resin
to obtain a mixture. The mixture is pulverized to a size of a few
.mu.m to several tens of .mu.m by a mechanical method, such as an
airflow type or a mechanical pulverizer, and the resulting product
is classified by size, and then to impart mobility, charge
stability, cleanability, and the like, an external additive is
added and applied uniformly on a surface.
[0007] However, the method of preparing a toner by a pulverizing
method has the following disadvantages:
[0008] i) the size of the prepared toner particle is difficult to
control,
[0009] ii) toner particles are very coarse and irregular, and thus,
contacting faces between the toner particles becomes larger, thus
decreasing mobility, since the shape of the pulverized toner
particles is uncontrolled,
[0010] iii) the yield is low since size distribution of toner
particles is very large, and thus, only toner particles within a
specific size range are selected and used,
[0011] iv) it is difficult to impart and control electrical
properties of the surfaces, due to irregularity of the
surfaces,
[0012] v) a transferring property and developing property are
degraded since the weight distribution of each particle is high,
and
[0013] vi) a dispersion between a binder resin and an internal
additive is difficult.
[0014] Alternatively, the method of preparing a toner by
polymerization is a superior method over the pulverizing method.
The toners prepared by this method are classified into a
suspension-polymerized toner, an emulsion-polymerized toner, and
the like. For the emulsion-polymerized toner, which has a particle
size of 5 to 15 .mu.m, which is a general size of toner particles,
is prepared by preparing an emulsion comprising a resin having a
particle size less than 1 .mu.m, a pigment, a mold release agent,
and the like, and then adding an aggregating agent thereto to
aggregate the emulsion. As described above, a mold release agent is
a component of toner particles essential in preventing an offset or
paper jam.
[0015] Referring to FIG. 1 and FIG. 2, a method of preparing an
emulsion-polymerized toner is schematically shown, according to
U.S. Pat. Nos. 6,120,967 and 5,863,696.
[0016] In FIG. 1, the method includes the operations of preparing
an emulsion of mold release agent comprising a polyethylene mold
release agent, an anionic dispersing agent, water, and emulsifying
the mold release agent using a homogenizer (102); preparing a latex
by combining a monomer (styrene plus butyl acrylate plus acrylic
acid), an anionic surfactant and a polymerization initiator and
polymerizing at 70.degree. C. (104); mixing a pigment and emulsion
of the mold release agent and the latex (106); adding an
aggregating agent (polyammonium chloride) and aggregating for 30
minutes at 48.degree. C. (108); and melting the aggregated
particles by allowing to stand for an hour at 90.degree. C.
(110).
[0017] In FIG. 2, the method includes the operations of dispersing
a pigment by combining the pigment, a dispersing agent (sodium
dodecyl sulfate), and distilled water and dispersing for one hour
using an ultrasonic homogenizer (202); mixing the pigment
dispersion and a monomer by combining the monomer (styrene, butyl
acrylate, and methacrylic acid), the pigment dispersion and a
dispersing agent (204); polymerizing by agitating for 7 hours at a
speed of 500 rpm and 70.degree. C. (206); and filtering and drying
(208).
[0018] U.S. Pat. No. 6,120,967 recites that an emulsion of a mold
release agent is separately prepared, the emulsion is mixed with a
latex and a pigment, and an aggregating agent such as a
polyammonium chloride is added to a mixture, thus binding together
a pigment, emulsion particles of a mold release agent and a
latex.
[0019] Alternatively, U.S. Pat. No. 5,863,696 describes a process
in which a pigment dispersion is first prepared, mixed with a
monomer, and then polymerization is performed, thus binding a
pigment and a latex without an aggregating agent. However, even in
this case, if one is to include a mold release agent, a procedure
of aggregating a mold release agent by an aggregating agent by
using a separate emulsion of a mold release agent is required.
[0020] However, in conventional techniques, when a latex, a pigment
and an emulsion of a mold release agent are bound together by use
of an aggregating agent, binding even between the same types of
particles as well as between different types of particles occurs,
and the amounts of a pigment and a wax are difficult to control.
Even when a mold release agent is included by using a separate
emulsion of a mold release agent, the selection of a dispersing
agent that may influence the physical properties of a toner is
limited, and preparation of particles less than 1 .mu.m in diameter
is difficult.
[0021] Furthermore, in conventional techniques, when using a
commercial emulsion, the free selection of a mold release agent and
an emulsifying agent is limited. Even when using an emulsion of a
mold release agent prepared directly, a temperature that is higher
than a melting point of a mold release agent and a high speed
dispersing apparatus are required, and thus the preparation is
difficult, since a conventional mold release agent in a solid state
should be dispersed in water in particles less than 1 .mu.m in
diameter.
SUMMARY OF THE INVENTION
[0022] The present invention provides a method for preparing a
latex containing pigments copolymerized with a crystalline polymer
by which a latex containing pigments copolymerized with a
crystalline polymer can be prepared in one process without
requiring a separate aggregation process, and a low fusing
temperature can be provided by substituting a crystalline polymer
material having a low melting point of the prepared latex for a
mold release agent.
[0023] According to an aspect of the present invention, a method is
utilized to prepare a latex containing pigments copolymerized with
a crystalline polymer, the method comprising: dispersing a pigment
and a dispersing agent in water having an ultra-high purity to
obtain a pigment dispersion; dissolving a crystalline monomer in a
basic monomer mixture to obtain an organic phase; dissolving while
heating the dispersing agent in water having an ultra-high purity,
and then mixing the solution with the pigment dispersion to obtain
an aqueous phase; mixing and agitating the organic phase and the
aqueous phase to obtain a homogenized solution; agitating and
heating the homogenized solution; adding a polymerization initiator
to the homogenized solution to be reacted; and cooling the reaction
solution to room temperature.
[0024] A method of preparing a latex according to an embodiment of
the present invention may provide a latex that includes pigments
copolymerized with a crystalline polymer in one process without
requiring a separate aggregation process, facilitate control of the
amounts and aggregation of each component in a latex, and provide a
latex having a narrow particle size distribution. Further, a low
fusing temperature may be provided by substituting a crystalline
polymer material having a low melting point of the prepared latex
as a mold release agent, and a melting point of a crystalline
polymer may be controlled by readily controlling the type, the
amount and a polymerization degree of a crystalline polymer.
[0025] Additional aspects and/or advantages of the invention will
be set forth in part in the description which follows and, in part,
will be obvious from the description, or may be learned by practice
of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] These and/or other aspects and advantages of the invention
will become apparent and more readily appreciated from the
following description of the embodiments, taken in conjunction with
the accompanying drawings of which:
[0027] FIG. 1 is a schematic process flow chart of the preparation
of a latex comprising a mold release agent, according to a
conventional technique;
[0028] FIG. 2 is a schematic process flow chart of the preparation
of a latex comprising a mold release agent, according to another
conventional technique;
[0029] FIG. 3 is a schematic process flow chart of the preparation
of a latex that includes pigments copolymerized with a crystalline
polymer, according to an embodiment of the present invention;
and
[0030] FIG. 4 is a schematic process flow chart of the preparation
of a latex that includes pigments copolymerized with a crystalline
polymer, according to another embodiment of the present
invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0031] Reference will now be made in detail to the embodiments of
the present invention, examples of which are illustrated in the
accompanying drawings, wherein like reference numerals refer to the
like elements throughout. The embodiments are described below to
explain the present invention by referring to the figures.
[0032] As illustrated by the operations set forth in FIG. 3, a
method of preparing a latex according to an embodiment of the
present invention comprises, generally: preparation of a pigment
dispersion (302); preparation of an organic phase (304);
preparation of an aqueous phase (306); preparation of a homogenized
solution by mixing and agitating the organic phase and the aqueous
phase (308); agitating and heating the homogenized solution (310);
polymerization of the homogenized solution (312); and cooling to
room temperature (314), as described more fullybelow.
[0033] A dispersing agent used in preparation of a pigment
dispersion may be, but is not limited to, an anionic surfactant
selected from the group consisting of a carboxylate, an ester
sulfate and a sulfonate; or a non-ionic surfactant selected from
the group consisting of a polyoxyethylene alkylether, a
polyoxyethylene alkylphenylether, a polyoxyethylene fatty acid
ester, a sorbitan fatty acid ester, a polyoxysorbitan fatty acid
ester, a polyoxyethylene alkylamine and an oxyethyleneoxypropylene
block copolymer.
[0034] A pigment used in the preparation of the pigment dispersion
may be a pigment known to those skilled in the art. To prepare a
black and white toner, carbon black or aniline black may be used.
To prepare a color toner, carbon black may be used as a black color
of a pigment, and yellow, magenta and cyan pigments may be also be
included.
[0035] The yellow pigment may be a condensed nitrogen compound, an
isoindolinone compound, an anthraquine compound, an azo metal
complex or an allyl imide compound. Specifically, C.I. PIGMENT
YELLOW 12, 13, 14, 17, 62, 74, 83, 93, 94, 95, 109, 110, 111, 128,
129, 147 or 168, or the like, may be used.
[0036] The magenta pigment may be a condensed nitrogen compound, an
anthraquine compound, a quinacridone compound, a naphthol compound,
a benzoimidazole compound, a thioindigo compound or a perylene
compound. Specifically, C.I. PIGMENT RED 2, 3, 5, 6, 7, 23, 48:2,
48:3, 48:4, 57:1, 81:1, 144, 146, 166, 169, 177, 184, 185, 202,
206, 220, 221 or 254, or the like, may be used.
[0037] The cyan pigment may be a copper phthalocyanine and its
derivatives, or an anthraquine compound. Specifically, C.I. PIGMENT
BLUE 1, 7, 15, 15:1, 15:2, 15:3, 15:4, 60, 62 or 66, or the like,
may be used.
[0038] Such pigments may be used alone or in a mixture of at least
two types of pigments, and may be selected by consideration of
color, saturation, brightness, weatherability, dispersity in
toners, or the like.
[0039] The pigment dispersion in operation i) may be prepared by
agitating with a glass bead at an agitation speed of 2,000 to
10,000 rpm for 1 to 5 hours using a milling equipment, such as a
DISPEMAT dispersing apparatus.
[0040] The basic monomer mixture used in the preparation of an
organic phase may be a mixture of an aromatic-based vinyl monomer
selected from the group consisting of a styrene, an o-methyl
styrene, an m-methyl styrene, a p-methyl styrene, a p-methoxy
styrene, a p-phenyl styrene, a p-chloro styrene, a p-ethyl styrene,
a p-n-butyl styrene, a p-tert-butyl styrene, a p-n-hexyl styrene, a
p-n-octyl styrene, a p-n-nonyl styrene, a p-n-decyl styrene, a
p-n-dodecyl styrene, a 2,4-dimethyl styrene, a 3,4-dichloro styrene
and their derivatives; a (meth)acrylic acid ester-based monomer
selected from the group consisting of an acrylic acid methyl, an
acrylic acid ethyl, an acrylic acid butyl, an acrylic acid-2-ethyl
hexyl, an acrylic acid cyclohexyl, an acrylic acid phenyl, a
methacrylic acid methyl, a methacrylic acid ethyl, a methacrylic
acid butyl, a methacrylic acid hexyl, a methacrylic acid-2-ethyl
hexyl, .beta.-hydroxy acrylic acid ethyl, y-amino acrylic acid
propyl, a methacrylic acid stearyl, a methacrylic acid dimethyl
amino ethyl, a methacrylic acid diethyl amino ethyl and their
derivatives; a vinyl ester-based monomer selected from the group
consisting of an acetic acid vinyl, a propionic acid vinyl, a
benzoic acid vinyl and their derivatives; a vinyl ether-based
monomer selected from the group consisting of a vinyl methyl ether,
a vinyl ethyl ether, a vinyl isobutyl ether, a vinyl phenyl ether
and their derivatives; a monoolefine-based monomer selected from
the group consisting of an ethylene, a propylene, an isobutylene, a
1-butene, a 1-pentene, a 4-methyl-1-pentene and their derivatives;
a diolefine-based monomer selected from the group consisting of a
butadiene, an isoprene, a chloroprene and their derivatives; and a
halogenated olefine-based monomer selected from the group
consisting of a vinyl chloride, a vinylidene chloride, a vinyl
fluoride and their derivatives.
[0041] Also, the crystalline monomer used in the preparation of an
organic phase may have 18 to 32 carbon atoms, and a melting point
of 30 to 70.degree. C. The crystalline monomer may be, but is not
limited to, a stearyl acrylate, a stearyl methacrylate, a hexadecyl
acrylate, a heptadecyl acrylate, a nonadecyl acrylate, a nonadecyl
methacrylate, an aralkyl acrylate, an aralkyl methacrylate, a
behenyl acrylate, a behenyl methacrylate, a pentacosyl acrylate, a
pentacosyl methacrylate, a heptacosyl acrylate, a heptacosyl
methacrylate, an octadecyl acrylate, an octadecyl methacrylate, or
the like.
[0042] The crystalline monomer forms a crystalline polymer by
copolymerization with the basic monomer. The crystalline polymer,
when the pigment-containing latex is used as a toner for printer
imaging, functions as a mold release agent that plays a role in
preventing an offset or paper jam on fusing a toner. Thus, by the
method of preparing a latex according to an embodiment of the
present invention, a low fusing temperature may be provided by
substituting a crystalline polymer material having a low melting
point for a mold release agent, and the melting point of the
crystalline polymer may be controlled by controlling a type
readily, an amount, a polymerization degree, or the like, of a
crystalline monomer.
[0043] The amount of the crystalline polymer in latex may be 1 to
50 parts by weight based on 100 parts by weight of the latex. When
the amount of the crystalline polymer is less than 1 part by
weight, a mold releasing effect by the crystalline polymer cannot
be obtained. When the amount exceeds 50 parts by weight, a problem
in fusing a toner and imaging may arise.
[0044] The basic monomer in the organic phase prepared as above
then forms a polymer material having a glass transition temperature
of 40 to 100.degree. C. by polymerization, and the crystalline
monomer forms a crystalline polymer material having a melting point
of 30 to 80.degree. C. by copolymerization with the basic
monomer.
[0045] An aqueous phase is prepared for mixing with an organic
phase that is prepared as described above to obtain a homogenized
solution, and the aqueous phase is prepared by heat-dissolving a
dispersing agent in water having an ultra-high purity, and then
mixing with a pigment dispersion prepared in the operation
(302).
[0046] A dispersing agent used in preparing an aqueous phase may
be, but is not limited to, a non-ionic surfactant selected from the
group consisting of a polyoxyethylene alkyl ether, a
polyoxyethylene alkyl phenyl ether, a polyoxyethylene fatty acid
ester, a sorbitan fatty acid ester, a polyoxy sorbitan fatty acid
ester, a polyoxyethylene alkyl amine and an oxyethyleneoxypropylene
block copolymer. Herein, water having an ultra-high purity may be
obtained by foaming with a nitrogen gas to remove any oxygen.
[0047] After preparing the organic phase and the aqueous phase, the
organic phase and the aqueous phase are mixed in a reactor, and
homogenized by using a homogenizer such as IKA ULTRA TURREX. For
example, homogenization may be carried out at an agitation speed of
1,000 to 7,000 rpm for 1 to 60 min.
[0048] Then, the solution homogenized by the homogenization process
may be heated to 50 to 80.degree. C. at an agitation speed of 100
to 800 rpm to carry out polymerization.
[0049] After agitating and heating the homogenized solution, the
polymerization reaction is carried out by adding a polymerization
initiator to the homogenized solution, and the inside of the
reactor is purged with nitrogen gas. A polymerization initiator may
be, but is not limited to, a water-soluble polymerization initiator
selected from a group consisting of a persulfate, an azo-based
compound and a peroxide compound. A persulfate polymerization
initiator may be a potassium persulfate, an ammonium persulfate, or
the like, and an azo based compound polymerization initiator may be
a 4,4'-azobis-4-cyano valeric acid and its salt, and a
2,2'-azobis(2-amidino propane) salt, or the like. The amount of the
polymerization initiator may be 1 to 5 parts by weight based on 100
parts by weight of the homogenized solution. When the amount of the
polymerization initiator is less than 1 part by weight of the
homogenized solution, a sufficient polymerization initiating effect
cannot be obtained. When the amount of the polymerization initiator
exceeds 5 parts by weight of the homogenized solution, problems of
a runaway reaction and generation of a low molecular weight body
may arise.
[0050] A polymerization time may be 5 to 24 hours. When the
polymerization time is less than 5 hours, a sufficient
polymerization cannot be performed.
[0051] After performing polymerization as described above, a latex
containing pigments copolymerized with a crystalline polymer may be
prepared a final operation of cooling the reaction solution to room
temperature.
[0052] The present invention will now be described in greater
detail with reference to the following examples. The following
examples are for illustrative purposes only, and are not intended
to limit the scope of the invention.
EXAMPLE 1
1) Preparation of a Pigment Dispersion
[0053] A cyan pigment dispersion was prepared by agitating 30 g of
PB15:3, a cyan pigment, 100 g of water having an ultra-high purity
and 3 g of DOWFAX, an anionic surfactant with 200 g of a glass bead
in a DISPERMAT dispersing apparatus at an agitation speed of 3,000
rpm for 3 hours. The volume average particle size of the pigment
dispersion was 110 nm.
2) Preparation of an Organic Phase
[0054] An organic phase was prepared by adding 10 g of an octadecyl
acrylate as a crystalline monomer to 100 g of a basic monomer
mixture comprising a styrene, a butyl acrylate and an acrylic acid
(mixed weight ratio of 7:2:1 to 7.5:1:0.5) to be dissolved.
3) Preparation of an Aqueous Phase
[0055] An aqueous phase was prepared by dissolving 5 g of the
pigment dispersion prepared in above 1), 3 g of DOWFAX, an anionic
surfactant, and 3 g of TRITON, a non-ionic surfactant, in 200 g of
water having an ultra-high purity.
4) Preparation of a Homogenized Solution
[0056] The organic phase prepared in operation 2) above and the
aqueous phase prepared in operation 3) above were mixed in 1 l
reactor, and then homogenized using an IKA ULTRA TURREX at 7,000
rpm for 30 min. Then, the homogenized solution was poured into a
reaction bath, and heated to 75.degree. C. while agitating at 100
rpm.
5) Polymerization Reaction and Cooling
[0057] When the temperature within the reaction bath reached
75.degree. C., 1 g of potassium persulfate was introduced as a
polymerization initiator, and the inside of the reactor was purged
with nitrogen gas. The polymerization reaction time was 24 hours,
and after completion of the reaction, the reaction solution was
cooled to room temperature.
[0058] On analyzing the latex particle prepared according to
Example 1 by using a differential scanning calorimeter (DSC), the
glass transition temperature and the melting point were,
respectively, 69.degree. C. and 42.degree. C. The volume average
size and the number average size of the latex particle prepared
were, respectively, 170 nm and 130 nm.
EXAMPLE 2
[0059] A latex particle was prepared in the same manner as
described in Example 1, except that a 10:1 mixture of a styrene and
an octadecyl acrylate was used as an organic phase. The glass
transition temperature and the melting point of the prepared latex
particle were, respectively, 96.degree. C. and 40.degree. C. The
volume average size and the number average size of the latex
particle were, respectively, 162 nm and 122 nm.
EXAMPLE 3
[0060] A latex particle was prepared in the same manner as
described in Example 1, except that the amount of the octadecyl
acrylate was 40 g. The glass transition temperature and the melting
point of the prepared latex particle were, respectively, 69.degree.
C. and 42.degree. C. The volume average size and the number average
size of the latex particle were, respectively, 200 nm and 140
nm.
EXAMPLE 4
[0061] A latex particle was prepared in the same manner as
described in Example 1, except that a behenyl acrylate was used
instead of the octadecyl acrylate. The glass transition temperature
and the melting point of the prepared latex particle were,
respectively, 96.degree. C. and 57.degree. C. The volume average
size and the number average size of the latex particle were,
respectively, 190 nm and 144 nm.
EXAMPLE 5
[0062] A latex particle was prepared in the same manner as
described in Example 1, except that a PY180 was used as a pigment
instead of PB15:3. The particle size of the pigment dispersion was
220 nm. The volume average size and the number average size of the
prepared latex particle were, respectively, 370 nm and 230 nm.
EXAMPLE 6
[0063] A latex particle was prepared in the same manner as
described in Example 1, except that a PR122 was used as a pigment
instead of PB15:3. The particle size of the pigment dispersion was
380 nm. The volume average size and the number average size of the
prepared latex particle were, respectively, 491 nm and 310 nm.
EXAMPLE 7
[0064] A latex particle was prepared in the same manner as
described in Example 1, except that carbon black (NIPEX 70,
manufactured by DEGUSSA) was used as a pigment instead of PB15:3.
The particle size of the pigment dispersion was 164 nm. The volume
average size and the number average size of the prepared latex
particle were, respectively, 250 nm and 201 nm.
[0065] A method of preparing a latex according to an embodiment of
the present invention may provide a latex that includes pigments
copolymerized with a crystalline polymer in one process without
requiring a separate aggregation process, facilitate control of the
amounts and aggregation of each component in a latex, and provide a
latex having a narrow particle size distribution. Further, by the
method of preparing a latex according to an embodiment of the
present invention, a low fusing temperature may be provided by
substituting a crystalline polymer material having a low melting
point for a mold release agent, and the melting point of the
crystalline polymer may be controlled by controlling readily a
type, an amount, a polymerization degree, or the like, of a
crystalline monomer.
[0066] As set forth in the operations illustrated in FIG. 4, a
method of preparing a latex in accordance with another embodiment
of the present invention comprises: copolymerizing pigments with a
crystalline polymer in one process in a reaction solution without a
separate aggregation process to facilitate control of amounts and
aggregation of each component in the latex and provide the latex
with a minimized particle size distribution, wherein the
crystalline polymer material acts as a mold release agent and has a
lower melting point than a melting point of the latex, when
prepared (402); and cooling the reaction solution (404). Operation
(402) may include any of the following further sub-operations.
[0067] In the method illustrated in FIG. 4, a pigment and a
dispersing agent may be dispersed in water having an ultra-high
purity to obtain a pigment dispersion and the dispersing agent used
in the dispersing the pigment and the dispersing agent in water may
be an anionic surfactant selected from the group consisting of a
carboxylate, an ester sulfate and a sulfonate; or a non-ionic
surfactant selected from the group consisting of a polyoxyethylene
alkylether, a polyoxyethylene alkylphenylether, a polyoxyethylene
fatty acid ester, a sorbitan fatty acid ester, a polyoxysorbitan
fatty acid ester, a polyoxyethylene alkylamine and an
oxyethyleneoxypropylene block copolymer.
[0068] Further, in the operations illustrated in FIG. 4, the
pigment dispersion in the dispersing the pigment and the dispersing
agent in water may be prepared by agitating at a speed of 2,000 to
10,000 rpm for 1 to 5 hours.
[0069] Also, in the operations illustrated in FIG. 4, a crystalline
monomer may be dissolved in a basic monomer mixture to obtain an
organic phase and the basic monomer mixture may be a mixture of an
aromatic-based vinyl monomer selected from the group consisting of
a styrene, an o-methyl styrene, an m-methyl styrene, a p-methyl
styrene, a p-methoxy styrene, a p-phenyl styrene, a p-chloro
styrene, a p-ethyl styrene, a p-n-butyl styrene, a p-tert-butyl
styrene, a p-n-hexyl styrene, a p-n-octyl styrene, a p-n-nonyl
styrene, a p-n-decyl styrene, a p-n-dodecyl styrene, a 2,4-dimethyl
styrene, a 3,4-dichloro styrene and their derivatives; a
(meth)acrylic acid ester-based monomer selected from the group
consisting of an acrylic acid methyl, an acrylic acid ethyl, an
acrylic acid butyl, an acrylic acid-2-ethyl hexyl, an acrylic acid
cyclohexyl, an acrylic acid phenyl, a methacrylic acid methyl, a
methacrylic acid ethyl, a methacrylic acid butyl, a methacrylic
acid hexyl, a methacrylic acid-2-ethyl hexyl, .beta.-hydroxy
acrylic acid ethyl, .gamma.-amino acrylic acid propyl, a
methacrylic acid stearyl, a methacrylic acid dimethyl amino ethyl,
a methacrylic acid diethyl amino ethyl and their derivatives; a
vinyl ester-based monomer selected from the group consisting of an
acetic acid vinyl, a propionic acid vinyl, a benzoic acid vinyl and
their derivatives; a vinyl ether-based monomer selected from the
group consisting of a vinyl methyl ether, a vinyl ethyl ether, a
vinyl isobutyl ether, a vinyl phenyl ether and their derivatives; a
monoolefine-based monomer selected from the group consisting of an
ethylene, a propylene, an isobutylene, a 1-butene, a 1-pentene, a
4-methyl-1-pentene and their derivatives; a diolefine-based monomer
selected from the group consisting of a butadiene, an isoprene, a
chloroprene and their derivatives; and a halogenated olefine-based
monomer selected from the group consisting of a vinyl chloride, a
vinylidene chloride, a vinyl fluoride and their derivatives.
[0070] Further, in the operations illustrated in FIG. 4, the
crystalline monomer may have 18 to 32 carbon atoms, and a melting
point of 30.degree. C. to 70.degree. C.
[0071] Also, in the operations illustrated in FIG. 4, the
crystalline monomer may form a crystalline polymer by
copolymerization with the basic monomer, and the amount of the
crystalline polymer in the latex may be 1 to 50 parts by weight
based on 100 parts by weight of the latex.
[0072] Further, in the operations illustrated in FIG. 4, the basic
monomer may form a polymer material having a glass transition
temperature of 40.degree. C. to 100.degree. C. by polymerization,
and the crystalline monomer may form a crystalline polymer material
having a melting point of 30.degree. C. to 80.degree. C. by
copolymerization with the basic monomer.
[0073] Also, in the operations illustrated in FIG. 4, a dispersing
agent may be dissolved, while heating, in water having an
ultra-high purity to form a solution, and then the solution may be
mixed with the pigment dispersion to form an aqueous phase, wherein
the dispersing agent may be a non-ionic surfactant selected from
the group consisting of a polyoxyethylene alkyl ether, a
polyoxyethylene alkyl phenyl ether, a polyoxyethylene fatty acid
ester, a sorbitan fatty acid ester, a polyoxy sorbitan fatty acid
ester, a polyoxyethylene alkyl amine and an oxyethyleneoxypropylene
block copolymer.
[0074] Further, in the operations illustrated in FIG. 4, the
organic phase and the aqueous phase may be mixed and agitated to
achieve homogenization, and the mixing and agitation may be carried
out at an agitation speed of 1,000 to 7,000 rpm for 1 to 60
min.
[0075] Also, in the operations illustrated in FIG. 4, the agitation
speed in the agitating and heating the homogenized solution may be
100 to 800 rpm, and the heating temperature may be 50.degree. C. to
80.degree. C.
[0076] Further, in the operations illustrated in FIG. 4, a
polymerization initiator may be added to the homogenized solution
and may be a water-soluble polymerization initiator selected from
the group consisting of a persulfate, an azo based compound and a
peroxide compound.
[0077] Also, in the operations illustrated in FIG. 4, the
polymerization initiator may be used in 1 to 5 parts by weight
based on 100 parts by weight of the homogenized solution.
[0078] Although a few embodiments of the present invention have
been shown and described, it would be appreciated by those skilled
in the art that changes may be made in these embodiments without
departing from the principles and spirit of the invention, the
scope of which is defined in the claims and their equivalents.
* * * * *