U.S. patent application number 14/527750 was filed with the patent office on 2016-05-05 for preparing latex using a biosolvent.
This patent application is currently assigned to Xerox Corporation. The applicant listed for this patent is Xerox Corporation. Invention is credited to Chieh-Min Cheng, Shigeng Li.
Application Number | 20160122506 14/527750 |
Document ID | / |
Family ID | 55754579 |
Filed Date | 2016-05-05 |
United States Patent
Application |
20160122506 |
Kind Code |
A1 |
Li; Shigeng ; et
al. |
May 5, 2016 |
Preparing Latex using a Biosolvent
Abstract
A process for making a latex emulsion, where the process
involves dissolving resin in a biosolvent that hydrolyzes on
exposure to water.
Inventors: |
Li; Shigeng; (Penfield,
NY) ; Cheng; Chieh-Min; (Rochester, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Xerox Corporation |
Norwalk |
CT |
US |
|
|
Assignee: |
Xerox Corporation
|
Family ID: |
55754579 |
Appl. No.: |
14/527750 |
Filed: |
October 29, 2014 |
Current U.S.
Class: |
524/158 |
Current CPC
Class: |
G03G 9/08755 20130101;
C08K 5/42 20130101; G03G 9/08797 20130101; C09D 5/027 20130101;
C09D 5/022 20130101; C08J 3/12 20130101; C08J 3/095 20130101; C08K
5/101 20130101; C08J 3/05 20130101 |
International
Class: |
C08K 5/101 20060101
C08K005/101; C08K 5/42 20060101 C08K005/42 |
Claims
1. A method for preparing a latex emulsion from a resin comprising:
a) combining a surfactant with a lactate ester to form a
dispersion, wherein said lactate ester is biodegradable; b) mixing
the dispersion with a resin until a homogenous mixture forms; and
c) combining the homogenous mixture with water to hydrolyze said
lactate ester and to form a latex emulsion.
2. The method of claim 1, wherein said resin comprises a polyester
polymer.
3. The method of claim 1, wherein said ester is lactic acid ethyl
ester.
4. The method of claim 1, wherein said resin comprises an amorphous
resin or a crystalline resin.
5. The method of claim 1, wherein following (c), said resin of said
latex emulsion is isolated by centrifugation, filtration,
distillation or spray drying.
6. The method of claim 1, wherein said surfactant is selected from
the group consisting of an anionic surfactant, a cationic
surfactant, a non-ionic surfactant and combinations thereof.
7. The method of claim 1, wherein said surfactant comprises an
alkyldiphenyloxide disulfonic acid or salt thereof.
8. The method of claim 1, wherein said surfactant comprises
alkyldiphenyloxide disulfonate.
9. The method of claim 1, wherein water is added at a ratio of from
about 1:6 to about 1:2 relative to said ester.
10. The method of claim 1, wherein said lactate ester hydrolyzes to
an organic acid and an alcohol after mixing with water.
11. The method of claim 1, wherein surfactant is added in an amount
from about 5 wt % to about 7.5 wt % relative to said ester.
12. The method of claim 1, wherein resin is added in an amount from
about 3 wt % to about 4.5 wt % relative to said ester.
13. A method for preparing resin particles comprising: a) combining
an alkyldiphenyloxide disulfonate with lactic acid ethyl ester to
form a solution; b) mixing the solution with a resin until a
homogenous mixture forms; c) combining the homogenous mixture with
water to hydrolyze said lactic acid ethyl ester and to form resin
particles in an emulsion; and d) separating the resin particles
from said emulsion.
14. The method of claim 13, wherein said resin comprises a
polyester polymer.
15. The method of claim 13, wherein said resin comprises an
amorphous resin or a crystalline resin.
16. The method of claim 13, wherein said resin particles are
isolated by centrifugation, filtration, distillation or spray
drying.
17. The method of claim 13, wherein water is added at a ratio of
from about 1:6 to about 1:2 relative to said ester.
18. (canceled)
19. The method of claim 13, wherein surfactant is added in an
amount from about 5 wt % to about 7.5 wt % relative to said
ester.
20. The method of claim 13, wherein resin is added in an amount
from about 3 wt % to about 4.5 wt % relative to said ester.
Description
FIELD
[0001] The present disclosure relates to producing resin emulsions
useful for producing toner where the resin is dissolved in a
biosolvent that hydrolyzes on exposure to water.
BACKGROUND
[0002] Resin emulsions can be produced using phase inversion
emulsification (PIE). PIE typically includes use of organic
solvents, such as, methyl ethyl ketone (MEK) and isopropyl alcohol
(IPA), to dissolve the resin and then adding water to produce
polyester latexes via phase change. Most organic solvents are
hazardous and have to be removed from the latexes and then disposed
of properly to meet environmental standards,
[0003] It would be advantageous to provide an improved process for
preparing, "green," latex without using organic solvents.
SUMMARY
[0004] A process is disclosed for preparing latexes using a
biosolvent which is 100% biodegradable and has 100% biobased
content, including that there is no environmentally hazardous
ingredient used during the process. The disclosed process is more
simple than current PIE processes, leading to shorter cycle time
and lower production costs. The latexes prepared by the method as
disclosed are useful, for example, in making emulsion aggregation
toner.
[0005] In embodiments, a method for preparing a latex emulsion from
a resin is disclosed including combining a surfactant with a
lactate ester, such as, ethyl lactate, to form a dispersion,
wherein said lactate ester is biodegradable; mixing the dispersion
with a, resin until the resin dissolves to form a homogenous
mixture; and combining the homogenous mixture with water to
hydrolyze the lactate ester and to form a latex emulsion.
DETAILED DESCRIPTION
[0006] Latex emulsions of resins commonly are produced using PIE in
which resins first are dissolved in an organic solvent, which may
be a mixture of solvents, such as, methyl ethyl ketone (MEK) and
isopropyl alcohol (IPA), then optionally neutralized with an
appropriate base, and then some water (such as, deionized water
(DIW) or (DI water)) may be introduced into the mixture to create a
homogeneous water-in-oil (W/O) dispersion (water droplets dispersed
in continuous oil). Subsequently, additional water is added to
invert the phase of the dispersion into an oil-in-water (O/W) latex
emulsion. Energy intensive processing of the latex, such as
distillation, is used to remove organic solvents and finally,
surfactant and other preservatives may be added to the latex. The
latex can be used for a variety of purposes including in emulsion
aggregation (EA) methods for the production of toner particles.
[0007] A solvent of interest is a biodegradable lactate ester which
dissolves a resin. The lactate ester is an ester of lactic acid of
the formula. CH.sub.3--CH(OH)--COOR, where R can comprise a variety
of hydrocarbon groups, including alkyl, either linear or branched,
saturated or not, or cyclic, from C.sub.1 to about C.sub.10. Hence,
examples include, methyl, ethyl, propyl, including n-propyl,
isopropyl and cyclopropyl, butyl, including n-butyl, sec-butyl,
isobutyl and tert-butyl, and so on A cyclic compound may be
substituted, may contain a heteroatom and may comprise more than
one ring, which may be fused, and so on. Examples include aryl,
phenyl, cycloalkyl and so on. On exposure of the lactate ester to
water and acid or base, which H.sup.+ ion can be contributed by the
resin or by an acid or buffer, the biosolvent lactate ester
hydrolyzes into one or more products. The resin is not soluble in
the product(s) of the hydrolyzed biosolvent. Hence, as the
effective concentration of biosolvent decreases with continuing
hydrolysis, the one dissolved resin forms particles. Hydrolysis can
continue until biosolvent is depleted, H amounts are depleted,
particle formation ceases or any other milestone as a design
choice. Acid may be added to drive the hydrolysis to completion.
The stage of the reaction can be assessed by monitoring the levels
of the reagents or products using materials and methods known in
the art, such as, a chromatography. The resin particles can be
isolated or separated from the emulsion using methods known in the
art. The biosolvent can be regenerated by combining the hydrolysis
product(s) practicing, for example, an esterification reaction,
using known materials and methods.
[0008] Ethyl lactate (EL), also known as lactic acid ethyl ester,
is an example of a biosolvent of interest and is totally
biodegradable. EL is found naturally in small quantities in a wide
variety of foods including wine, chicken and various fruits. Due to
low toxicity, EL is used in pharmaceutical preparations, food
additives (approved by FDA) and fragrances. In addition, EL can be
produced from biological and industrial sources. EL hydrolyzes in
the presence of water and H.sup.+ to form lactic acid and ethanol
(EtOH). Lactic acid and EtOH each has use in the food,
pharmaceutical and cosmetic industries.
[0009] Therefore, in the latex-forming process of interest, the
biosolvent hydrolysis reaction is not reversible due to, for
example, the waning concentration of H.sup.+ from the limiting
levels of dissolved resin, waning concentration of dissolved resin,
waning concentration of biosolvent, excess levels of H.sup.+ and so
on to ensure maximal particle formation. The resulting resin
particles are stable, which may benefit from presence of surfactant
in and/or on the particle.
[0010] The level of biosolvent remaining or hydrolysis product(s)
produced in the latex emulsion may be monitored during the reaction
using materials and methods known in the art, such as, a
chromatography, such as, as or liquid chromatography for biosolvent
level or hydrolysis product(s) level.
[0011] Because the resulting solution comprises the water soluble
hydrolysis product(s), such as, ethanol (EtOH) and lactic acid when
EL is used as the solvent, separation of the resin particles from
the solvent can be as simple as any separation of an aqueous medium
from a particulate, such as, filtration, centrifugation,
decantation and so on, although other separation methods can be
used including distillation, spray drying and so on. The particles
can be washed any number of times with water to remove any EtOH and
lactic acid, or other products when other lactate esters are used
as biosolvent, The lactic acid and EtOH may be reused to produce EL
where lactic acid and EtOH are reacted to form EL in an
esterification reaction. EtOH may be used for other applications,
including, but not limited to inkjet printing, cosmetics, a solvent
and the like, and lactic acid can be used in the food industry, as
a chemical feed stock and so on.
[0012] Unless otherwise indicated, all numbers expressing
quantities and conditions, and so forth used in the specification
and claims are to be understood as being modified in all instances
by the term, "about." "About," is meant to indicate a variation of
no more than 10% from the stated value. Also used herein is the
term, "equivalent," "similar," "essentially," "substantially,"
"approximating," and, "matching," or grammatic variations thereof,
have generally acceptable definitions or at the least, are
understood to have the same meaning, as, "about."
[0013] As used herein, "biobased," means a product (other than food
or feed) that is composed, in whole or in substantial part (e.g.,
between about 55% to about 80% by weight of the compound or
product, about 70% to about 80% by weight of the compound or
product, of biological products or renewable materials (including
plant, animal and microbial materials).
[0014] As used herein, the prefix, "bio," refers to a method that
incorporates, or to a reagent or to a product that is composed, in
whole or in part, of a biological product, including plant, animal
and microbe materials, or derivatives thereof. Generally, a
biomaterial or bio-based material is biodegradable, that is,
substantially or completely biodegradable, by substantially is
meant greater than 50%, greater than 60%, greater than 70% or more
of the material is degraded from the original molecule or
composition to another form by a biological or environmental
mechanism, such as, action thereon by bacteria, animals, plants,
light, temperature, oxygen and so on, in a matter of days, matter
of weeks, a year or more, but generally no longer than two years.
A, "biosolvent," is a liquid which dissolves a resin, such as, a
polyester. The biosolvent is composed of a bio-based material in
whole or in part and is biodegradable.
[0015] Resins
[0016] Any resin soluble in biosolvent may be utilized in forming a
latex emulsion of the present disclosure. The resins may be an
amorphous resin, a crystalline resin and/or a combination thereof.
The resin may be a polyester resin, including the resins described,
for example, in U.S. Pat. Nos. 6,593,049 and 6,756,176, the entire
disclosure of each of which hereby is incorporated by reference in
entirety. Suitable resins also may include a mixture of an
amorphous polyester resin and a crystalline polyester resin as
described in U.S. Pat. No. 6,830,860, the entire disclosure of
which hereby is incorporated by reference in entirety. Suitable
resins may include a mixture of high molecular and low molecular
weight amorphous polyester resins.
[0017] In embodiments, the resin may be a polyester resin formed by
reacting a polyol with a polyacid in the presence of an optional
catalyst.
[0018] For forming a crystalline or amorphous polyester, suitable
polyols include aliphatic polyols with from about 2 to about 36
carbon atoms selected in an amount of from about 40 to about 60
mole %.
[0019] Examples of polyacids or polyesters include vinyl diacids or
vinyl diesters selected in an amount of for example, from about 40
to about 60 mole %.
[0020] Examples of crystalline resins include polyesters,
polyamides, polyimides, polyolefins, polyethylene, polybutylene,
polyisobutyrate, ethylene-propylene copolymers, ethylene-vinyl
acetate copolymers, polypropylene, mixtures thereof, and the like.
Specific crystalline resins may be polyester based, such as
poly(ethylene-adipate), poly(propylene-adipate),
poly(butylene-adipate), poly(pentylene-adipate),
poly(hexylene-adipate), poly(ethylene-succinate),
poly(propylene-succinate), poly(butylene-succinate),
poly(pentylene-succinate), poly(hexylene-succinate),
poly(octylene-succinate), poly(ethylene-sebacate),
poly(propylene-sebacate), poly(butylene-sebacate),
poly(pentylene-sebacate), poly(hexylene-sebacate),
poly(octylene-schacate), poly(decylene-sebacate),
poly(decylene-decanoate), poly(ethylene-decanoate), poly(ethylene
dodecanoate), poly(nonylene-sebacate), poly(nonylene-decarioate),
copoly(ethylene-fumarate)-copoly(ethylene-sebacate),
copoly(ethylene-fumarate)-copoly(ethylene-decanoate),
copoly(ethylene-fumarate)-copoly(ethylene-dodecanoate)
copoly(2,2-dimethylpropane-1,3-diol-decanoate)-copoly
(nonylene-decanoate), poly(octylene-adipate). Examples of
polyamides include poly(ethylene-adipamide)
poly(propylene-adipamide), poly(butylenes-adipamide),
poly(pentylene-adipamide), poly(hexylene-adipamide),
poly(octylene-adipamide), poly(ethylene-succinimide), and
poly(propylene-sebecamide). Examples of polyimides include
poly(ethylene-adipimide), poll(propylene-adipimide),
poly(butylene-adipimide), poly(pentylene-adipimide),
poly(hexylene-adipimide), poly(octylene-adipimide),
poly(ethylene-succinimide), poly(propylene-succinimide) and
poly(butylene-succinimide).
[0021] The crystalline resin may be present in an amount of from
about 1 to about 50 by weight of the toner components. The
crystidline resin may possess various melting points of, for
example, from about 30.degree. C. to about 120.degree. C. The
crystalline resin may have a number average molecular weight (Mn),
as measured by gel permeation chromatography (GPC) of for example,
from about 1,000 to about 50,000 and a weight average molecular
weight (Mw) of, for example, from about 2,000 to about 100,000, as
determined by GPC. The molecular weight distribution (Mw/Mn) of the
crystalline resin may be, for example, from about 2 to about 6.
[0022] Polycondensation catalysts may be utilized in forming either
the crystalline or amorphous polyesters and include tetraalkyl
titanates, dialkyltin oxides, such as, dibutyltin oxide,
tetraalkyltins, such as, dibutyltin dilaurate, and dialkyltin oxide
hydroxides, such as, butyltin oxide hydroxide, aluminum alkoxides,
alkyl zinc, dialkyl zinc, zinc oxide, stannous oxide or
combinations thereof. Such catalysts may be utilized in amounts of,
for example, from about 0.01 mole % to about 5 mole % based on the
starting polyacid or polyester used to generate the polyester
resin.
[0023] Examples of unsaturated amorphous resins that can be used
include those disclosed in U.S. Pat. No. 6,063,827, the entire
disclosure of which is hereby incorporated by reference in
entirety.
[0024] The amorphous resin may be present, for example, in an
amount of from about 30 to about 100% by weight of the toner
components. In embodiments, the amorphous resin or combination of
amorphous resins utilized in the latex may have a glass transition
temperature (Tg) of from about 30.degree. C. to about 80.degree. C.
In embodiments, the combined resins utilized in the latex may have
a melt viscosity of from about 10 to about 1,000,000 Pa*S at about
130.degree. C.
[0025] Other suitable resins that can be used to make toner
comprise a styrene, an acrylate, such as, an alkyl acrylate, such
as, methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl
acrylate, dodecylacrylate, n-octyl acrylate, n-butylacrylate,
2-chloroethyl acrylate; .beta.-carboxy ethyl acrylate (.beta.-CEA)
phenyl actylate, methacrylate, butadienes, isoprenes, acrylic
acids, acrylonitriles, styrene acrylates, styrene butadienes,
styrene methacrylates, and so on, such as, methyl
.alpha.-chloroacrylate, methyl methacrylate, ethyl methacrylate,
butyl methacrylate, hutadiene, isoprene, inethactylonitrile,
acrylonitrile, vinyl ethers, such as vinyl methyl ether, vinyl
isobutyl ether, vinyl ethyl ether and the like; vinyl esters, such
as, vinyl acetate, vinyl propionate, vinyl benzoate and vinyl
butyrate; vinyl ketones, such as, vinyl methyl ketone, vinyl hexyl
ketone, methyl isopropenyl ketone and the like; vinylidene halides,
such as, vinylidene chloride, vinylidene chlorofluoride and the
like; N-vinyl indole, N-vinyl pyrrolidone, methacrylate, acrylic
acid, methacrylic acid, acrylamide, methacrylamide, vinylpyridine,
vinylpyrrolidone, vinyl-N-methylpyridinium chloride, vinyl
naphthalene, p-chlorostyrene, vinyl chloride, vinyl bromide, vinyl
fluoride, ethylene, propylene, butylene, isobutylene and mixtures
thereof.
[0026] One, two or more resins may be used. Where two or more
resins are used, the resins may be in any suitable ratio weight
ratio), such as, of from about 1% (first resin)/99% (second resin)
to about 99% (first resin)/1% (second resin).
[0027] A toner may include two amorphous polyester resins and a
crystalline polyester resin. The weight ratio of the three resins
may be from about 30% first amorphous resin/65% second amorphous
resin/5% crystalline resin, to about 60% first amorphous resin/20%
second amorphous resin/20% crystalline resin.
[0028] A toner may include at least two amorphous polyester resins,
a high molecular weight resin and a low molecular weight: resin. As
used herein, a high molecular weight (HMW) amorphous resin may have
an Mw of from about 35,000 to about 150,000 and a low molecular
weight (UMW) amorphous resin may have an Mw of from about 10,000 to
about 30,000.
[0029] The weight ratio of the two resins may be from about 10%
first amorphous resin/90% second amorphous resin to about 90% first
amorphous resin/10% second amorphous resin.
[0030] The resin may possess acid groups which, in embodiments, may
be present at the terminus of a resin molecule. Acid groups, which
may be present, include carboxylic acid groups. The number of acid
groups may be controlled by adjusting the materials utilized to
form the resin and reaction conditions. The resin may have an acid
number from about 2 mg KOH/g of resin to about 200 mg KOH/g of
resin.
Biosolvent
[0031] Any suitable lactate ester may be used to dissolve a resin,
for example, lactic acid ethyl ester (i.e., ethyl lactate). The
amount of resin that is combined with the biosolvent, on a weight
basis, can be from about 3 wt % to about 4.5 wt %, from about 3.25
wt % to about 4.25 wt %, from about 3.5 wt % to about 4 wt %,
although amounts outside of those ranges can be used, so long as
the resin dissolves completely in the biosolvent.
[0032] The biosolvent may or may not be miscible with water and may
have a boiling point of from about 30.degree. C. to about
200.degree. C.
[0033] Surfactant
[0034] The process of the present disclosure includes adding a
surfactant to the btosolvent before or after adding resin to the
biosolvent. In embodiments, surfactant can be mixed with a resin
before adding to the biosolvent.
[0035] One, two or more surfactants can be used in the process of
interest or in other emulsions or mixtures. The surfactants may be
selected from ionic surfactants and nonionic surfactants. Anionic
surfactants and cationic surfactants are encompassed by the term,
"ionic surfactants." The surfactant may be added as a solid or as a
solution with a concentration of from about 5%, to about 100% (pure
surfactant) by weight, from about 10% to about 95% by weight. The
surfactant is present. in an amount of from about 100% to about
250% relative to the weight of the resin, from about 130% to about
210% by weight, from about 150% to about 190% by weight of the
resin.
[0036] Examples of suitable anionic surfactants include, but are
not limited to, sodium dodecylsulfate (SDS), sodium dodecylbenzene
sulfonate, sodium dodecylnaphthalenesulfate, dialkyl benzenealkyl
sulfates and sulfonates, alkyldiphenyloxide disulfonic acids and
salts thereof, abitic acid. NEOGEN R.RTM. and NEOGEN SC.RTM.
available from Kao, Tayca Power.RTM., available front Tayca Corp.,
DOWFAX.RTM., available from Dow Chemical Co., such as, 2A1, which
is alkyldiphyenyloxide disulfonate; sodium dodecyl diphenyl oxide
disulfonate (i.e., CALFAX.RTM., available from Pilot Chemical Co,
Cincinnati, Ohio) and the like, as well as mixtures thereof.
[0037] Examples of suitable cationic surfactants include, but are
not limited to, dialkyl benzenealkyl ammonium chloride, lauryl
trimethyl aminonium 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.RTM. and ALKAQUAT.RTM. (available from Alkaril Chemical
Company), SANIZOL.RTM. (benzalkonium chloride, available from Kao
Chemicals), and the like, as well as mixtures thereof.
[0038] Examples of suitable nonionic surfactants include, but are
not limited to, polyvinyl alcohol, polyacrylic acid, methalose,
methyl cellulose, ethyl cellulose, propyl cellulose, hydroxy ethyl
cellulose, carboxy methyl cellulose, polyoxyethylene cetyl ether,
polyoxyethylene lauryl ether, polyoxyethylene octyl ether,
polyoxyethylene octylphenyl ether, polyoxyethylene oleyl ether,
polyoxyethylene sorbitan monolaurate, polyoxyethylene stearyl
ether, polyoxyethylene nonylphenyl ether,
dialkylphenoxypoly(ethyleneoxy)ethanol (available from sanofi as
ANTAROX 890.RTM., IGEPAL CA-210.RTM., IGEPAL CA520.RTM., IGEPAL
CA-720.RTM., IGEPAL CO-890.RTM., IGEPAL CO-720.RTM., IGEPAL
CO-290.RTM., IGEPAL CA-210.RTM. and ANTAROX 897.RTM.) and the like,
as well as mixtures thereof.
[0039] Processing
[0040] The present process may include forming a mixture,
optionally at an elevated temperature, containing a resin, a
biosolvent, which can be a mixture or two or more biosolvent and a
surfactant to form a resin mixture. Resins may be preblended prior
to forming the mixture. The elevated temperature may be near to or
above the Tg or melting point of the resin(s).
[0041] Thus, in embodiments, a process of the present disclosure
may include contacting at least one resin and a surfactant with is
biosolvent to form a resin mixture, optionally heating the resin
mixture to an elevated temperature, optionally adding an acid
forming H.sup.+ to said mixture, optionally stirring or shaking the
mixture, adding water to the mixture to hydrolyze the biosolvent to
induce resin particle formation and. collecting the resin
particles.
[0042] Surfactant can be mixed or dissolved in the biosolvent,
optionally at an elevated Temperature. Surfactant is mixed with
biosolvent, on a weight basis, in an amount from about 5 wt % to
about 7.5 wt %, from about 5.5 wt % to about 7 wt %, from about 6
wt % to about 6.5 wt %. When fully dissolved, resin then is added
to the solution.
[0043] Mixing may be conducted utilizing any means within the
purview of those skilled in the art. For example, mixing may be
conducted in a glass kettle with an anchor blade impeller, an
extruder, i.e., a twin screw extruder, a kneader, such as, a Haake
mixer, a batch reactor or any other device capable of intimately
mixing viscous materials to create near or homogenous mixtures.
[0044] Stirring, although not necessary, can be conducted at a
stirring. speed sufficient to ensure resin dissolution in the
biosolvent and/or a homogeneous preparation is obtained. Lower
speeds can be used. Any stirring can be continued until dissolution
occurs or a homogeneous preparation is obtained.
[0045] Water is added to the mixture to induce biosolvent
hydrolysis and resin emulsion formation in a ratio of biosolvent to
water, either on a weight or volume basis, of from about 1:6 to
about 1:2, from about 115.5 to about 112.5, from about 1:5 to about
1:3. However, water amounts outside of those ratios can be used as
a design choice, an artisan can monitor progress of btosolvent
hydrolysis and/or particle formation.
[0046] Following formation of the emulsion, additional surfactant
or water, or optional neutralizing agent can be added to the
emulsion, although not required.
[0047] When particle formation is completed, for example, no
further change in reactant concentration, hydrolysis product
concentration or solids content is observed, or at any milestone as
a design choice, the resin particles are removed from the
suspension by known methods, such as filtration, decantation,
centrifugation and so on The liquids can be separated, for example,
by distillation, and recycled as taught herein, for example, either
to regenerate biosolvent, or the resulting product(s) of the
degradation of the biosolvent can be used for known purposes.
[0048] The desired properties of the resin (i.e., particle size,
such as, about 200 nm, and low residual biosolvent level) may be
achieved by adjusting the resin, biosolvent, surfactant, process
parameters (i.e., reactor temperature, vacuum and process time) and
so on.
[0049] Toner
[0050] The resulting latex then may be utilized to form a toner by
any method within the purview of those skilled in the art. The
latex emulsion may be contacted with an optional colorant,
optionally in a dispersion, an optional wax and so on as known in
the art to form toner by a suitable process, such as an
emulsion/aggregation (EA) and coalescence process.
[0051] Colorants
[0052] Various known suitable colorants, such as dyes, pigments,
mixtures of dyes, mixtures of pigments, mixtures of dyes and
pigments, and the like, may be included in the toner. In
embodiments, the colorant may be included in the toner in an amount
of, for example, 0 to about 35% by weight of the toner, although
the amount of colorant can be outside of that range.
[0053] As examples of suitable colorants, mention may be made of
carbon black like REGAL 330.RTM. (Cabot), Carbon Black 5250 and
5750 (Columbian Chemicals), Sunsperse Carbon Black LHD 9303 (Sun
Chemicals); magnetites, such as Mobay magnetites MO8029.TM.,
MO8060.TM.; Columbian magnetites; MAPICO BLACKS.TM. and surface
treated magnetites; Pfizer magnetites CB4799.TM., CB5300.TM.,
CB5600.TM., MCX6369.TM.; Bayer magnetites, BAYFERROX 8600.TM.,
8610.TM.; Northern Pigments magnetites, NP-604.TM., NP-608.TM.;
Magnox magnetites TMB-100.TM. or TMB-104.TM.; and the like. As
colored pigments, there can be selected in magenta, yellow, red,
green, brown, blue or mixtures thereof. Generally, cyan, magenta or
yellow pigments or dyes or mixtures thereof, are used. The pigment
generally is used as a water-based dispersion.
[0054] Wax
[0055] Optionally, a wax may also be combined with the resin and a
colorant in forming toner particles. The wax may be provided in a
wax dispersion, which may include a single type of wax or a mixture
of two or more different waxes.
[0056] When included, the wax may be present in an amount of, for
example, from about 1% by weight to about 25% by weight of the
toner particles, although the amount of wax can be outside of that
range. When a wax dispersion is used, the wax dispersion may
include any of the various waxes conventionally used in emulsion
aggregation toner compositions. Waxes that may be selected include
those having, for example, an average molecular weight of from
about 500 to about 20,000.
[0057] Neutralizing Agent
[0058] The resin may be mixed with a weak base or buffer to enhance
dissolution in the pre-aggregation mixture. The neutralizing agent
may be used to neutralize acid groups in the resin, so a
neutralizing agent herein may also be referred to as a "basic
neutralization agent." Any suitable basic neutralization reagent
may be used and may include both inorganic basic agents and organic
basic agents. Suitable basic agents may include ammonium hydroxide,
potassium hydroxide, sodium hydroxide, sodium carbonate, sodium
bicarbonate, lithium hydroxide, potassium carbonate, combinations
thereof and the like. Suitable basic agents may also include
monocyclic compounds and polycyclic compounds having at least one
nitrogen atom, which compounds may be substituted at any carbon
position on the ring.
[0059] Utilizing the above basic neutralization agent in
combination with a resin possessing acid groups, a neutralization
ratio of from about 25% to about 300% may be achieved. The
neutralization ratio may be calculated as the molar ratio of basic
groups provided with the basic neutralizing agent to the acid
groups present in the resin multiplied by 100%.
[0060] Toner Preparation
[0061] The toner particles ma be prepared by any method within the
purview of one skilled in the art. Although embodiments relating to
toner particle production are described below with respect to EA
processes, any suitable method of preparing toner particles may be
used, including, chemical processes, such as, suspension and
encapsulation processes disclosed in U.S. Pat Nos. 5,290,654 and
5,302,486, the entire disclosure of each of which hereby is
incorporated by reference in entirety. Toner may be made in a batch
reactor, a microreactor, a continuous reactor, any other method
using any other apparatus, or combination thereof,
[0062] In embodiments, toner compositions may be prepared by EA
processes, such as, a process that includes aggregating a mixture
of an optional colorant, an optional wax and any other desired or
required reagents, and emulsions including a resin made as
described above, optionally with surfactants as described above,
and then coalescing the aggregated particle mixture. The pH of the
resulting mixture may be adjusted by an acid such as, for example,
acetic acid, nitric acid etc., to a pH of from about 2 to about
5.
[0063] Following preparation of a mixture for forming toner
including a resin, optional colorant, optional wax, optional
neutralizing agent and so on, an aggregating agent may be added to
the mixture to enhance particle formation. Any suitable aggregating
agent may be utilized to form a toner particle. Suitable
aggregating agents include, for example, aqueous solutions of as
divalent cation or a multivalent cation material. The aggregating
agent may be, for example, an inorganic cationic aggregating agent,
such as, polyaluminum halides, such as, polyaluminum chloride
(PAC), or the corresponding bromide, fluoride or iodide,
polyaluminum silicates, such as, polyaluminum sulfosilicate (PASS),
and water soluble metal salts, including aluminum chloride,
aluminum nitrite, aluminum sulfate, potassium aluminum sulfate,
calcium acetate, calcium chloride, calcium nitrite, calcium
oxylate, calcium sulfate, magnesium acetate, magnesium nitrate,
magnesium sulfate, zinc acetate, zinc nitrate, zinc sulfate, zinc
chloride, zinc bromide, magnesium bromide, copper chloride, copper
sulfate and combinations thereof. In embodiments, the aggregating
agent may be added to the mixture at a temperature that is below
the Tg of the resin.
[0064] The aggregating agent may be added to the mixture utilized
to form a toner in an amount of, for example, from about 0.1% to
about 10% by weight of the resin in the mixture.
[0065] The particles aggregate until a desired particle size is
obtained. Particle size can be monitored during the growth process,
for example, with a COULTER COUNTER, for average particle size. The
aggregation may proceed by maintaining the elevated temperature, or
slowly raising the temperature to for example, from about
40.degree. C. to about 100.degree. C., and holding the mixture at
that temperature for a time of from about 0.5 hr to about 6 hr
while maintaining stirring, to provide the aggregated
particles.
[0066] Once the desired size of the toner particles is achieved,
the pH of the mixture may be adjusted with base or a buffer to a pH
of from about 3 to about 10 to freeze, that is, to stop, toner
growth. The base utilized may be any suitable base such as, for
example, alkali metal hydroxides, such as, for example, sodium
hydroxide, potassium hydroxide, ammonium hydroxide, combinations
thereof and the like. In embodiments, a chelator, such as, ethylene
diamine tetraacetic acid (EDTA), may be added to help adjust the pH
to the desired value noted above.
[0067] Shell Resin
[0068] In embodiments, after aggregation, but prior to coalescence,
a resin coating may be applied to the aggregated particles to form
a shell thereover. Any resin described above or as known in the art
may be utilized as the shell. A polyester amorphous resin latex as
described above ma be included in the shell, which may be combined
with a different resin, and then added to the particles as a resin
coating to form a shell.
[0069] The shell resin may be applied to the aggregated particles
by any method within the purview of those skilled in the art. The
resins utilized to form the shell may be in an emulsion, including
any surfactant described above, an initiator, a branching agent, a
conductive compound and so on as known in the art. The emulsion
possessing the resins may be combined with the aggregated particles
described above so that the shell forms over the aggregated
particles.
[0070] The shell may be present in an amount of from about 10% by
weight to about 40% by weight of the latex particles.
[0071] Coalescence
[0072] Following aggregation to the desired particle size and
application of any optional shell, the particles then may be
coalesced to the desired final shape, the coalescence being
achieved by, for example, heating the mixture to a temperature of
from about 45.degree. C. to about 100.degree. C., which may be at
or above the Tg and/or melting point of the resins utilized to form
the toner particles. Coalescence may be accomplished over a period
of from about 0.01 to about 9 hours.
[0073] After aggregation and/or coalescence, the mixture may be
cooled to room temperature (RT), such as, from about 20.degree. C.
to about 25.degree. C. The cooling may be rapid or slow, as
desired. A suitable cooling method may include introducing cold
water to a jacket around the reactor. After cooling, the toner
particles optionally may be washed with water and then dried.
Drying may be accomplished by any suitable method for drying,
including, for example, freeze-drying.
[0074] Additive
[0075] The toner particles may contain positive or negative charge
control agents, for Example, in an amount of from about 0.1 to
about 10% by weight of the toner. Examples of suitable charge
control agents include quaternary ammonium compounds inclusive of
alkyl pyridinium halides; bisulfates; alkyl pyridinium compounds,
including those disclosed in U.S. Pat. No. 4,298,672, the entire
disclosure of which is hereby incorporated by reference in
entirety; organic sulfate and sulfonate compositions, including
those disclosed in U.S. Pat. No. 4,338390, the entire disclosure of
which is hereby incorporated by reference in entirety; cetyl
pyridinium tetrafluoroborates; distearyl dimethyl ammonium methyl
sulfate; aluminum salts, such as, BONTRON E84.TM. or E88.TM.
(Orient Chemical Industries, Ltd.); combinations thereof and the
like.
[0076] Flow additives also can be blended with the toner particles.
Examples include metal oxides, such as titanium oxide, silicon
oxide, aluminum oxides, cerium oxides, tin oxide, mixtures thereof
and the like; colloidal and amorphous silicas, such as.
AEROSIL.RTM., metal salts and metal salts of fatty acids inclusive
of zinc stearate and calcium stearate, or long chain alcohols, such
as UNILIN 700, and mixtures thereof.
[0077] Each of the external additives may be present in an amount
of from about 0.1% by weight to about 5% by weight of the toner,
although the amount of additives can be outside of those
ranges.
[0078] In embodiments, the dry toner particles having a shell of
the present disclosure may, exclusive of external surface
additives, have the following characteristics:
[0079] (1) volume average diameter (also referred to as "volume
average particle diameter") of from about 3 to about 25 .mu.m;
[0080] (2) number average geometric, size distribution (GSDn)
and/or volume average geometric: size distribution (GSDv) of horn
about 1.05 to about 1.55; and
[0081] (3) circularity of from about 0.93 to about 1, in
embodiments, from about 0.95 to about 0.99 (as measured with, for
example, a Sysmex FPIA 2100 analyzer).
[0082] In embodiments, the final size of the toner particles may be
less than about 8 .mu.m, less than about 7 .mu.m, less than about 6
.mu.m in size.
[0083] The characteristics of toner particles may be determined by
any suitable technique and apparatus, such as, a Beckman Coulter
MULTISIZER 3.
[0084] The toner can be used in an electrophotographic, xerographic
or other imaging device as known in the art.
[0085] The subject matter now will be exemplified in the following
non-limiting examples. Parts and percentages are by weight unless
otherwise indicated.
Example
[0086] Ten grams of DOWFAX.RTM. 2A1 surfactant were dispersed in
160 g ethyl lactate under mechanical mixing for 10 min. Then, 6 g
of an amorphous resin were added to the solution and the mixing was
continued for another 30 min until the resin dissolution became
homogenous. Subsequently, the resin dissolution was mixed with
water at a weight ratio of 1:4 to prepare the latex. The particles
were measured by Nanotrac for size and the D50 was 234 .mu.m with a
monomodal peak
[0087] A control sample was prepared using MEK as the solvent with
the identical procedure. A latex was not produced, the resin
coagulated as a singular yellow mass.
[0088] 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 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.
[0089] All references cited herein are incorporated herein by
reference in entirety.
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