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Claims  |
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What is claimed is:
1. A process for preparing an ink composition comprising a vehicle and a
dye having associated therewith at least one sulfonate group with which a
first cation species is associated, said ink composition suitable for use
in ink-jet printing, said process comprising:
(a) replacing at least a portion of said first cation species on said dye
with a preselected second cation species comprising at least one member
selected from the group consisting of alkali metals, alkaline-earth
metals, quaternary amines, protonated primary, secondary and tertiary
amines and ammonium, employing an ion exchange resin, to form an
ion-exchanged dye; and
(b) admixing said ion-exchanged dye with said vehicle to form said ink.
2. The process of claim 1 wherein said dye containing said first cation
species is purified prior to said cation-replacing.
3. The process of claim 2 wherein said dye is purified by reverse osmosis.
4. The process of claim 1 wherein said first cation species consists
essentially of sodium.
5. The process of claim 1 wherein at least a portion of said first cation
species on said dye is replaced with hydrogen cations by passing an
aqueous solution of said dye through the hydrogen form of a strong acid
ion exchange resin.
6. The process of claim 5 wherein at least a portion of said hydrogen
cations on said dye are subsequently replaced by said preselected second
cation species by neutralizing said dye in a base comprising said
preselected cation species and hydroxide anions.
7. The process of claim 6 wherein said hydrogencontaining dye is
neutralized to a pH ranging from about 4 to 10.
8. The process of claim 1 wherein at least a portion of said first cation
species on said dye are replaced with said preselected second cation
species by passing an aqueous solution of said dye through an ion exchange
resin loaded with said preselected second cation species.
9. The process of claim 1 wherein said preselected second cation species
comprises at least one member selected from the group consisting of
lithium, potassium, tetramethyl amine, triethanol amine, diethylene amine,
and ammonium.
10. The process of claim 1 wherein following said ion exchange, said dye
solution is concentrated to a desired concentration.
11. The process of claim 10 wherein said dye solution is concentrated using
reverse osmosis.
12. The process of claim 1 wherein said vehicle comprises at least one
component selected from the group consisting of glycols, glycerol, half
ethers and ethers of propylene glycols, ethers of glyceryl, alcohols,
esters, polymeric glycols, and water.
13. The process of claim 12 wherein said at least one component comprises a
member selected from the group consisting of ethylene glycol, diethylene
glycol, triethylene glycol, tetraethylene glycol, propylene glycol,
dipropylene glycol, tripropylene glycol, 1,3-butanediol, 1,4-butanediol,
1,5-pentanediol, 1,6-hexanediol, 2,5-hexanediol, hexylene glycol,
propylene glycol monomethyl ether, propylene glycol isopropyl ether,
propylene glycol n-butyl ether, propylene glycol ethyl ether, dipropylene
glycol monomethyl ether, dipropylene glycol ethyl ether, dipropylene
glycol n-butyl ether, dipropylene glycol iso-propyl ether, tripropylene
glycol monomethyl ether, tripropylene glycol ethyl ether, tripropylene
glycol n-butyl ether, tripropylene glycol, glyceryl .alpha.-monmethyl
ether, glyceryl .alpha.,.gamma.-dimethyl ether, glyceryl
.alpha.-mono-n-butyl ether, secbutyl alcohol, tert-amyl alcohol,
cyclohexyl alcohol, secoctyl alcohol, diacetone alcohol, benzyl alcohol,
isopropanol, n-propanol, methanol, ethanol, butyl lactate, ethyl lactate,
n-butyl propionate, PEG 200, PEG 300, PEG 400, and PPG 400.
14. A process for preparing an ink composition comprising a vehicle and a
dye having associated therewith at least one sulfonate group with which
sodium cations are associated, said ink composition suitable for use in
ink-jet printing, said process comprising:
(a) replacing at least a portion of said sodium cations on said dye with
hydrogen cations to form a dye containing hydrogen cations by passing an
aqueous solution of said dye through the hydrogen form of a strong acid
ion exchange resin;
(b) neutralizing said dye containing said hydrogen cations by adding a base
comprising a preselected cation species comprising at least one member
selected from the group consisting of alkali metals, alkaline-earth
metals, quaternary amines, protonated primary, secondary and tertiary
amines and ammonium and an anion species comprising hydroxide to form a
dye solution containing said preselected cations and having a pH ranging
from about 4 to 10; and
(c) admixing said neutralized dye solution with said vehicle to form said
ink.
15. The process of claim 14 wherein said dye containing said sodium cations
is purified prior to said cationreplacing.
16. The process of claim 15 wherein said dye is purified by reverse
osmosis.
17. The process of claim 14 wherein said amine comprises at least one
member selected from the group consisting of tetramethyl amine, triethanol
amine, and diethylene amine.
18. The process of claim 14 wherein said following said neutralizing, said
dye solution is concentrated to a desired concentration.
19. The process of claim 18 wherein said dye solution is concentrated using
reverse osmosis.
20. The process of claim 14 wherein said vehicle comprises at least one
glycol.
21. The process of claim 20 wherein said glycol comprises a member selected
from the group consisting of diethylene glycol, triethylene glycol, and
polyethylene glycol.
22. A process for preparing an ink composition comprising a vehicle and a
dye having associated therewith at least one sulfonate group with which
sodium cations are associated, said ink composition suitable for use in
ink-jet printing, said process comprising:
(a) forming an aqueous dye solution of said dye;
(b) purifying said dye solution to remove chloride ions, excess sodium ions
and impurities;
(c) replacing at least a portion of said sodium cations on said dye with
hydrogen cations to form a dye containing hydrogen cations by passing said
aqueous solution of said dye through the hydrogen form of a strong acid
ion exchange resin;
(d) neutralizing said dye containing said hydrogen cations by adding a base
comprising a preselected cation species comprising at least one member
selected from the group consisting of alkali metals, alkaline-earth
metals, quarternary amines, protonated primary, secondary and tertiary
amines and ammonium and an anion species comprising hydroxide to form a
dye solution containing said preselected cations and having a pH ranging
from about 6 to 7;
(e) concentrating said dye solution to achieve a desired concentration; and
(f) admixing said ion-exchanged dye with said vehicle to form said ink,
said vehicle comprising at least one glycol.
23. The process of claim 22 wherein said amine comprises at least one
member selected from the group consisting of tetramethyl amine, triethanol
amine, and diethylene amine.
24. The process of claim 20 wherein said glycol comprises a member selected
from the group consisting of diethylene glycol, triethylene glycol, and
polyethylene glycol. |
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Claims |
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Description |
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TECHNICAL FIELD
The present invention is directed to preparation of inks employed in
ink-jet printing, and, more particularly, to an improved process for
preparing ink compositions used in thermal ink-jet printing.
BACKGROUND ART
In a modern thermal ink-jet printhead device, resistors used to propel
bubbles of ink toward the paper substrate must be able to fire for
millions of times without failure. In thermal printhead printing, the
purity and chemical structure of the dye in the ink can radically affect
the printhead operation, resulting in resistor failure or nozzle clogging.
Changing the cation of the dye molecule improves the solubility of the dye
molecule in the solvent, which prevents crusting (clogging of the
printhead nozzle from dye precipitation during storage). Selection of the
proper cation can also significantly improve resistor life of the
printhead. Substitution of FD&C Blue Dye #1 improves resistor life from
about 13 million firings to about 25 million firings by changing the
cation associated with the dye from sodium to triethanol amine.
In one process developed by the assignee of the present application, such
cation substitution is achieved by reverse osmosis (ultrafiltration). The
process is quite useful for purification of the dye. However, while
producing highly acceptable dyes (in which the extend of cation
substitution is controlled), reverse osmosis requires an expenditure of
processing time operating at pressures of about 100 to 300 psi that may be
unacceptable for some manufacturing processes.
Accordingly, a need remains for a more rapid process for improving the
properties of dyes used in ink-jet printing.
DISCLOSURE OF INVENTION
It is an object of the present invention to provide a process for reducing
crusting of dyes used in ink-jet printing.
It is another object of the present invention to provide a process for
improving the properties of dyes used in ink-jet printing by cation
substitution.
It is yet another object of the present invention to provide a process for
increasing the efficiency of cation substitution, as measured by a
decrease in processing time, on dyes used in ink-jet printing.
It is a further object of the present invention to provide a process for
the controllable and facile substitution of cations on dyes used in
ink-jet printing.
These and further objects of the invention will become more readily
apparent upon a consideration of the following commentary.
Briefly, a process is provided for the fabrication of ink compositions used
in ink-jet printing. The process is suitably employed for dyes employed in
such inks having at least one negatively charged functional group, such as
a sulfonate group, with which sodium or other cations are associated.
The process comprises dissolving the dye in water to form a dye solution,
replacing the cations with hydrogen cations by ion exchange, and replacing
the hydrogen ions by preselected cations which impart certain desired
properties, such as reduced crusting, to the ink. The cation-exchanged dye
solution is then blended with one or more glycols or other components to
formulate the desired ink composition.
Alternatively, the desired cation species may be loaded onto a resin in an
ion-exchange column, and the sodium or other cations replaced directly
with the desired cation species if the proper affinity of the dye to resin
can be chosen.
Ion exchange is a very fast and efficient process for replacement of one
cation species by another. Further, certain cations, such as divalent
cations, that cannot be substituted onto the dye molecule by other
processes, such as reverse osmosis, can be substituted by ion exchange.
BEST MODES FOR CARRYING OUT THE INVENTION
Commercially prepared dyes are presently available complexed with sodium
cations. Thus, it will be appreciated that the discussion which follows is
given in terms of partially or totally replacing sodium cations with
certain desirable cations; the resulting modified dye evidences improved
properties over the sodium form. However, it should be understood that the
process of the invention may be used to replace any cation on a dye
molecule with another cation.
In the practice of the process of the invention, it is preferred that the
dye first be purified. While not essential to the practice of the
invention, the purification step improves the efficiency of the ion
exchange process.
Dye purification is best accomplished by reverse osmosis. In this process,
chloride, excess sodium, and impurities, which are present in the dye as
received from the manufacturer, are removed from the dye.
In the purification of the dye, the dye is first dissolved in water in an
amount ranging from about 8 to 15 wt %, or up to the solubility limit of
the dye, to form a dye solution. The lower concentration is constrained by
economic considerations, with the overall process consuming too long a
period of time at concentrations much below about 8 wt %. The upper
concentration is constrained by the presence of too much dye clogging the
membrane in reverse osmosis purification.
The dye solution is then purified by reverse osmosis, using spiral wound,
plate and frame or open tubular type systems or variations thereof. For a
spiral wound system, for example, the pressure may range from about 100 to
300 psi and the flow (which is a function of the membrane employed) is
typically maintained in the range of about 1 to 3 gal/min per pressure
vessel of 100 to 200 ft.sup.2 of membrane area.
While the reverse osmosis process is ordinarily operated at room
temperature, it may be operated at an elevated temperature, limited only
by the composition of the membrane or the boiling point of the solution.
In practice, the temperature may range from about 0.degree. to 100.degree.
C. It is possible to utilize several pressure vessels in parallel, which
provides a corresponding increase in surface area. Further, series
configurations may be employed; such configurations are also well-known.
As is well-known, the feed stock in the pressure vessel is separated by the
membrane into a concentrate (which contains the dye) and the permeate
(which contains impurities and a small amount of the dye).
The reverse osmosis process is used to remove chloride ions, excess sodium
ions and other impurities and to provide a dye that has a purity of about
99.9%. The conductivity of the concentrate is monitored, conveniently
using a chloride electrode, until a substantially constant reading is
achieved and equilibrium is reached, which indicates that no more
purification is taking place. The purified dye still has sodium cations
associated with the sulfonate groups on the dye. In accordance with one
embodiment of the invention, the sodium ions are replaced, first with
hydrogen cations, then replacing the hydrogen ions with the desired cation
species.
The replacement with hydrogen ions is accomplished by ion exchange,
involving passing an aqueous solution of the dye through the hydrogen form
of a strong acid ion exchange resin. The sodium cations from the dye
molecule are retained on the ion exchange resin and the solution passing
through the resin becomes the acid form of the dye. Suitable ion exchange
resins are so-called strong acid ion exchange resins, such as Dowex 50X-8,
available from Dow Chemical Company (Midland, MI), Duolite Cation Resin
225X 10H, available from Rohm & Haas (Philadelphia, Pa.), and Amberlite CG
120, also available from Rohm & Haas. Many other strong acid ion exchange
resins are also commercially available.
In order to obtain the desired free acid form of the dye, the amount of
resin to be used must be determined. This is conveniently done by
determining the milliequivalents of H.sup.+ per milliliter of wet resin.
Knowing the concentration of the dye and the number of sulfonate groups on
the dye (for example, for Food Black 2 there are four such groups), one
can easily determine the theoretical amount of resin required from
literature values.
Next, the free acid form of the dye, which has a pH of less than 1 to about
2, depending on the ratio of dye to resin, is neutralized with a base
which includes the desired cation species, thereby replacing at least a
portion of the hydrogen ions with the preselected cation species. Suitable
cation species include mono- and divalent cations, such as alkali and
alkaline-earth cations, ammonium cations, quaternary ammonium salts,
protonated primary, secondary and tertiary amines and the like. Preferred
examples of such cations include lithium and potassium, tetramethyl amine
((CH.sub.3).sub.4 N.sup.+), triethanol amine (C.sub.2 H.sub.5 OH).sub.3
NH.sup.+) and diethylene amine ((C.sub.2 H.sub.5).sub.2 HNH.sup.+).
Conveniently, the anion of the base is hydroxide, which combines with the
hydrogen cations on the dye to form water.
Desirably, the base is added until the pH of the dye solution is in the
mildly acidic to mildly basic range, about 4 to 10. Preferably, the base
is added to obtain a dye solution of a mildly basic pH, such that upon
subsequent addition of components to form the ink, the requisite final pH
is achieved. This eliminates an extra pH adjustment step. A pH meter is
conveniently employed to monitor the pH of the dye solution during the
neutralizing process.
During the foregoing ion exchange and neutralizing steps, the dye solution
has been diluted from its initial concentration. The dye solution is next
concentrated to return the concentration to a desired level. Reverse
osmosis is again advantageously employed to remove excess water, and
requires about one-half the time of the purification process. UV/visible
spectrophotometry is employed to monitor the concentration.
Finally, the vehicle is added to the dye solution to form the ink. The
vehicle may comprise any of, or a mixture of two or more of, the following
components: glycols such as ethylene glycol, diethylene glycol,
triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene
glycol, tripropylene glycol, 1,3-butanediol, 1,4-butanediol,
1,5-pentanediol, 1,6-hexanediol, 2,5-hexanediol, hexylene glycol,
glycerol, half ethers and ethers of propylene glycols such as propylene
glycol monomethyl ether, propylene glycol isopropyl ether, propylene
glycol n-butyl ether, propylene glycol ethyl ether, dipropylene glycol
monomethyl ether, dipropylene glycol ethyl ether, dipropylene glycol
n-butyl ether, dipropylene glycol isopropyl ether, tripropylene glycol
monomethyl ether, tripropylene glycol ethyl ether, tripropylene glycol
n-butyl ether, tripropylene glycol, ethers of glyceryl such as glyceryl
.alpha.-monomethyl ether, glyceryl .alpha.,.gamma.-dimethyl ether,
glyceryl .alpha.-mono-n-butyl ether, alcohols such as sec-butyl alcohol,
tert-amyl alcohol, cyclohexyl alcohol, sec-octyl alcohol, diacetone
alcohol, benzyl alcohol, iso-propanol, n-propanol, methanol, ethanol,
esters such as butyl lactate, ethyl lactate, n-butyl propionate, polymeric
glycols such as PEG 200, PEG 300, PEG 400, PPG 400, and water.
Further, the vehicle may include any of the additives used in ink-jet
compositions, such as surfactants to improve the wettability of the ink on
paper, polymers to help control bubble formation of inks in thermal
ink-jet printers, fungicides, and bactericides. The purity of the
components used in preparing the inks of the invention is that found in
normal commercial practice.
The ion-exchange resin may be regenerated for treating another dye
solution. The regeneration is conveniently done by passing hydrochloric
acid or sulfuric acid through the column and then washing with water until
the pH of the rinse is approximately neutral. This process leaves behind
only H.sup.+ on the resin.
It is well-known that sodium cations associated with a dye such as Food
Black 2 cause crusting. The process of the invention provides a dye having
a cation species, such as one listed above, which has been found to reduce
crusting of the ink.
Yet, sodium-containing dyes often have better kogation properties than many
of the cation-substituted dyes. Kogation is a coined term, unique to
thermal ink-jet printing, which describes the extent of decomposition of
the ink on the resistors of thermal ink-jet printers as a consequence of
heating. Such heating is used to form droplets of ink, which are propelled
toward the substrate.
Often, a balance between the desirable low crusting properties of the
cation-substituted dye and the desirable low kogation properties of the
sodium-containing dye may be achieved by blending the cation-exchanged dye
with sodium-containing dye, the latter possibly purified by the reverse
osmosis process described above to remove excess sodium.
In formulating such a blend, many factors will ordinarily be considered,
such as the construction of the ink pen, that is, the resistor design, how
hot the resistors are fired, the character of the surface (the extent of
carbon sticking from the decomposition of the ink, or kogation), the
thickness of layers for heat transfer, and so forth.
While the two-step process (ion exchange plus neutralization) described
above may be utilized in the practice of the invention, it may be
desirable to skip the hydrogen cation substitution and go directly to the
exchange of the sodium cations with the cation species of choice. However,
while this approach will certainly work, and the process of the invention
contemplates this alternative approach, the one-step process is not as
efficient as the two-step approach.
The one-step process results in the use of a considerable quantity of
expensive base to effect the ion exchange during regeneration of the
column, with a consequent waste of base. Further, the larger the cation,
the more steric hindrance of the cation plays a role in the ion
substitution process. Finally, the selectivity of the resin for the two
cations (cation on resin, cation on dye) becomes important. This is known
as the partition function of the resin. Use of the two-step process is
preferred, since it is easier to predict results by first preparing the
free acid form of the dye and then neutralizing to obtain the desired
cation-substituted form of the dye.
Ion exchange is a very fast and efficient process for replacement of one
cation species with another. Further, ion exchange can be used to replace
cations on the dye molecules that could not be easily accomplished by
other techniques, such as reverse osmosis.
INDUSTRIAL APPLICABILITY
The process of the invention is useful in the preparation of inks used in
ink-jet printing, and particularly in thermal ink-jet printing.
EXAMPLES
EXAMPLE 1
Substitution of TEA on Food Black 2 Dye Via Ion Exchange
A column containing about 5.3 l of Duolite Cation resin 225X 10H was
regenerated with 2 l of 18% hydrochloric acid. The column was then washed
with deionized (DI) water until the pH was 4.2.
A 20.5 Kg sample of Food Black 2 dye, purified by conventional reverse
osmosis and evidencing by UV/visible spectrophotometry an average
absorption of 0.2518 in a dilution of 1:10,000 over the range of 350 to
700 nm, was passed through the column at a flow rate of 500 ml/min,
followed by DI water until most of the color was collected. With good
column performance, less than 1 l of water should be required for each
liter of dye.
The ratio of dye to resin was chosen so that the dye was partially in the
hydrogen form and had a pH of 1.9. The dye was then neutralized with an
aqueous solution of 1.16 Kg of triethanol amine (TEA) to a pH of 6.5.
The number of moles of sodium per mole of dye prior to the ion exchange
treatment was determined to be 3.20. Following ion exchange, the number of
moles of sodium per mole of dye was determined to be 0.85, while the
number of moles of TEA per mole of dye was determined to be 2.66.
The substituted dye was then concentrated by conventional reverse osmosis
and idethylene glycol added to obtain the final ink composition desired.
The ink comprised 4.2 wt % of the dye (a mixture of treated and untreated
dye to provide 1.78 moles of TEA per mole of dye) in a vehicle comprising
50/50 (by volume) of DEG and water.
EXAMPLE 2
Substitution of TEA on Food Black 2 Dye Via Ion Exchange
The column was prepared as in Example 1. A 10.08 Kg sample of FB2 dye
(absorption by UV/visible spectrophotometry of 0.258 under the conditions
described in Example 1) was ion exchanged using down flow with good column
performance. The solution pH was 1.8 which was neutralized with an aqueous
solution of 0.60 Kg of TEA.
The number of moles of sodium per mole of dye prior to the ion exchange
treatment was determined to be 3.20. Following ion exchange, the number of
moles of sodium per mole of dye was determined to be 0.78, while the
number of moles of TEA per mole of dye was determined to be 2.64.
The resulting product was concentrated by reverse osmosis and formulated
into the final ink composition by the addition of diethylene glycol. The
ink comprised 4.2 wt % of the dye (a mixture of treated and untreated dye
to provide 1.78 moles of TEA per mole of dye) in a vehicle comprising
50/50 (by volume) of DEG and water.
Ink samples from the dyes treated in Examples 1 and 2 were used to fill six
pens from each for testing. The six pens showed no crusting and normal
kogation (low) compared to an ink prepared from sodium-containing dye not
treated in accordance with the invention. The amount of kogation increased
from low to moderate with increasing TEA to dye mole ratio. The optimum
balance of reduced crusting and acceptable kogation occurred with dye
having about 1.8 moles of TEA per mole of dye.
EXAMPLE 3
Ion Exchange of Acid Yellow 23
The cation exchange column contained 1.5 l of resin and was regenerated
with 250 ml of 36% HCl diluted 1:3 and washed with DI water until the pH
was about 5.5. To the column was added 1.0 l Acid Yellow 23 (FD&C Yellow
5) at 10% concentration. The dye was eluted with DI water, and 1600 ml of
a light yellow material was collected, the remainder being discarded.
The pH of the collected material was about 1.0, and was subsequently
neutralized with TEA. To obtain a pH of about 6.7, 95.1 g of 97% TEA was
required to neutralize the collected material.
The neutralized material was vacuum evaporated to concentrate the dye.
Measurement by UV/visible spectrophotometry of absorption at 426 nm showed
an absorption of 0.8195 at a dilution of 1:10,000, indicating a dye
concentration of 154.6 g/l. The calculated number of TEA moles per mole of
dye was 2.5.
Ink was made from the substituted dye, having the following properties:
dye load: 4% by weight
pH: 6.33
[Cl.sup.- ]: <5 ppm
The ink comprised 4 wt % of the treated dye, having 3 moles of TEA per mole
of dye, in a vehicle comprising 50/50 (by weight) DEG and water.
The ink was evaluated in an ink-jet print head for crusting, kogation and
thin film reliability. Where dye crystals (crusting) would form after two
days at room temperature with sodium-based dye, no crusting was observed
with this ink. Preliminary testing also showed thin film reliability
(resistor life) to increase by a factor of at least 2, while kogation went
from low to moderate (for the life of the pen).
EXAMPLE 4
Ion Exchange of FD&C Blue 1
The cation exchange column was loaded with 1.5 l of resin and was
regenerated. To the column was added 1.0 l of concentrated FD&C Blue 1 in
solution. The column was eluted with DI water, and about 2.5 l of material
was collected. The pH was adjusted with TEA to a value between 6 and 7.
The resulting TEA-substituted dye was concentrated on a spiral wound
reverse osmosis system with cellulose acetate membranes having a pore size
of 11 l at 150 psig and 25.degree. to 30.degree. C.
The absorption by UV/visible spectrophotometry was 1.51 at a 1:10,000
dilution. The dye solution was determined by atomic absorption to have 180
ppm sodium, compared to 1690 ppm for the dye prior to ion exchange at 97.5
g/l dye.
Inks were made comprising a dye mixture of 2.2 wt % of treated FD&C Blue 1,
1.3 wt % of untreated Direct Yellow 86 and 1 wt % of untreated Direct Red
227 in a vehicle of 50/50 (by volume) of DEG and water. The dye mixture
contained 1.8-2 moles of TEA per mole of dye.
Inks based on the substituted blue dye had good thin film reliability. No
resistor failures occurred up to 100 million firings, while inks based on
the sodium form of the dye showed on the average 3 failures per 20 pens at
less than 50 Mdots.
EXAMPLE 5
Carta Black Dye Substituted with Lithium
Carta Black dye was ion exchanged and substituted in a similar way as
described above with lithium cations in an attempt to improve kogation. An
ink was made comprising 2.5 wt % of the treated dye in a vehicle of 50/50
(by volume) of DEG and water. Initial studies did not indicate a
significant improvement in kogation.
EXAMPLE 6
Food Black 2 Dye Substituted with Tetramethyl Ammonium
Food Black 2 dye was ion exchanged and substituted with tetramethylammonium
(TMA) cations, using procedures as set forth in Example 2. The ink made
from this dye comprised 5 wt % treated dye (0.3 moles of sodium per mole
of dye) in a vehicle of 50/50 (by volume) DEG and water. The ink had
excellent crusting properties compared to the sodium form of Food Black 2
dye.
EXAMPLE 7
Direct Red 227 Substituted with TEA
Direct Red 227 dye was ion exchanged and substituted with triethanol amine
cations, using the procedures as in Example 4. An ink was made from 2.9 wt
% of a mixture of treated and untreated Direct Red 227 and 1.1 wt % of
untreated Direct Yellow 86 in a vehicle of 50/50 (by weight) DEG and
water. The dye mixture had 1.8 moles of TEA per mole of dye.
Ink prepared with the treated dye evidence improved reliability of firing
over the untreated dye. EXAMPLE 8
Direct Red 227 Substituted with TMA
Direct Red 227 dye was treated as in Example 7, except that
tetramethylammonium cations were employed as the substituting species. Ink
prepared with the treated dye evidence less viscous plugging of the
orifices and decreased nickel corrosion of the orifice plate than inks
prepared with the untreated dye.
Thus, there has been disclosed a process for reducing the crusting
properties of sodium-containing dyes used in ink-jet printing. The process
includes ion exchange and replaces at least a portion of the sodium
cations with preselected cations. Many changes and modifications will be
readily apparent to those of ordinary skill in the art, and all such
changes and modifications are deemed to be within the scope of this
invention, as defined by the scope of the appended claims.
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Description |
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