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Description  |
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BACKGROUND OF THE INVENTION
List of the Prior Art
The prior art appears to be best exemplified by the following patents:
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Banczak 4,021,252 May 3, 1977
Wachtel 4,024,096 May 17, 1977
Parkinson 4,045,397 Aug. 30, 1977
Hwang 4,070,322 Jan. 24, 1978
Parkinson (Germany) October 28, 1976
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Field of the Invention
This invention relates to jet ink compositions suitable for ink jet
printing on a variety of substrates including metal, synthetic polymers
and glass.
Ink jet printing techniques, although of comparatively recent development
in the art of applying decorative and identifying indicia to a substrate,
are of increasing importance. In general such techniques impose rigid
requirements on the ink compositions. To be suitable for use as a jet ink,
the compositions must meet rigid requirements of viscosity and
resistivity, solubility, compatibility of components, wettability of
substrate, must be quick drying and smear resistant without clogging the
ink jet nozzle and must permit rapid clean-up of the machine components
with minimum effort. At the same time, such compositions must also be
adapted for satisfactory performance in the particular end use
application.
To date, where the end use requirements have necessitated
abrasion-resistance, resistance to weathering and fade-resistance together
with suitability for use on a variety of substrates such as, for example,
polymeric surfaces, metal surfaces or glass surfaces, ink jet compositions
have not been satisfactory since no ink offering such versatility has been
available. Jet inks possess numerous advantages over those inks applied by
conventional techniques such as letter press, gravure, silk-screen or
other similar conventional techniques. Such conventional inks are not
suitable for jet ink printing because they frequently contain pigments
which cause clogging problems in the ink jet equipment. Additionally,
conventional inks generally require curing at elevated temperatures for
extended periods of time. Moreover, their use in printing polymer coated
surfaces, etc. has not been particularly efficacious primarily because the
means of applying such inks have not been conducive to high speed
techniques.
It is an object of this invention to provide ink compositions, suitable for
use in ink jet printing techniques, that exhibit excellent characteristics
of fade-resistance, abrasion-resistance, and weathering.
It is another object of this invention to provide jet ink compositions
suitable for application to a variety of surfaces including polymer
substrates, metal substrates and glass substrates. Yet another object of
this invention is to provide jet ink compositions suitable for application
to polymer coated wires.
Another object of the invention is to provide substrates bearing
identifying indicia, derived by application of said jet ink compositions
employing an ink jet printing technique.
Another object is to provide indicia-containing polymer coated wires that
are suitable for use in aircraft and that, when heated at temperatures of
about 300.degree. F., are characterized by resistance to hydraulic fluids
commonly employed.
These and other objects of the invention will be apparent from the
description of the invention which follows:
SUMMARY OF THE INVENTION
This invention relates to jet ink compositions comprising at least one
colorant, a binder resin and a solvent blend consisting essentially of
from about 25 to 40% of a lower aliphatic alcohol having 1 to 3 carbon
atoms and mixtures thereof, from about 0 to 40% of an organic compound
selected from the group consisting of aliphatic ketones having 3 to 8
carbon atoms, 0-20% of a lower alkylene glycol ethers and 5 to 15% water.
Such compositions are characterized by excellent fade-resistance,
abrasion-resistance and, resistance to weathering and are especially
suitable for forming identifying indicia on a variety of substrates
including glass, ceramics, polymeric resins, polymer coated wire and
coated and uncoated aluminum and steel.
DETAILED DESCRIPTION OF THE INVENTION
The above-described jet ink compositions contain a colorant, a solvent
blend, a resinous component and other optional ingredients, all of which
must be in carefully balanced proportion to achieve (1) successful
operation of the ink in a jet printing apparatus and (2) suitable
properties for use in coating the particular substrate.
In general, suitability of the inks herein for the desired end use is
measured in accordance with the following standards:
(1) Inks must dry instantly or be smear resistant upon application and dry
completely in about 15 seconds without a post cure;
(2) Indicia printed on polymer coated wire must be abrasion-resistant to
the extent that it remains legible at a minimum distance of 15 inches in
minimum daylight (30 foot candles) after 20 rubs with an abrasive felt
employing 2 lb. pressure at a speed of 30 to 60 rubs per minute;
(3) printing does not damage polymer coating wire insulation. When immersed
in a water solution containing 5% NaCl and a potential of 2000 volts rms.
is applied for one minute between the primary conductor and an electrode
in the solution, there is no dielectric breakdown of the primary wire
insulation, and the indicia remains legible thereafter;
(4) an optional requirement, when such compositions are to be employed in
certain specific aircraft is that the characters printed on polymer coated
wire must withstand a 24 hour minimum soak in Skydrol, a hydraulic fluid
containing active tributyl phosphate, (available commercially from
Monsanto as Skydrol LD) at a temperature of 70.degree. C. and, after air
drying at room temperature for 24 hours, the characters remain legible
thereafter;
(5) characters printed on polymer coated wire remain legible after a 24
hour minimum exposure, in a weatherometer, to alternating cycles of
ultraviolet light and tap water spray wherein the cycle periods are about
102 minutes exposure to ultraviolet light followed by about 18 minutes
exposure to both ultraviolet light and tap water spray.
(6) Indicia printed on glass must exhibit ready adhesion to the glass, be
abrasion and fade resistant and have the capability of withstanding
conditions of moisture and elevated temperature normally encountered in
pasteurization when the glass is designed for such use as beer bottles,
etc.
(7) Indicia printed on metal must exhibit ready adhesion to metal or
synthetic polymeric coatings on such metal; exhibit resistance to fading
and capability of maintaining adhesion under typical brewery
pasteurization conditions when immersed in solution for 15 minutes at
150.degree. F.
The above characteristics are indeed stringent requirements for an ink
composition of suitable viscosity, electrical resistivity and surface
tension properties, etc. to render it operable in ink jet printing
apparatus. The ink compositions of this invention meet these requirements.
COMPONENTS OF THE COMPOSITION
The Colorant
The characteristics exhibited by the colorant are of prime consideration to
achieve the stringent resistance properties discussed hereinabove. In
general, suitable colorants are dyes characterized by sufficient
solubility in the solvent mixture to give the desired color intensity and
compatibility with the other components of the compositions. Neozapon
Black RE (available commercially from BASF) is a particularly effective
colorant for conveying light fastness (fade resistance) to the ink while
Hecto Black R (also available from BASF) is most effective to convey
Skydrol resistance for use in printing polymer coated wire. Mixtures of
such colorants may also be used.
It is contemplated that functionally equivalent dyes other than Neozapon
Black RE and Hecto Black R may also be employed. Neozapon Black RE is
believed to be similar to Acid Black 63, Colour Index No. 21295 and
Solvent Black 27.
Such dyes appear to be chromium-complexed azo type dyes. Satisfactory
results have been obtained when employing Neozapon Red BE, Neozapon Red
GE, Neozapon Fire Red G and Neozapon Blue FLE.
In addition to the colorants discussed above, other dyes may be substituted
or utilized in combination therewith.
Suitable Dyes include those of the basic type, for example of the C.I.
Basic Blue, C.I. Basic Black and C.I. Basic Green types including methyl
violet, ethyl violet, crystal blue, chrysoidine, Victoria Blue, rhodamine,
auramine, etc. Mixtures of any of the illustrative dyes mentioned
hereinabove may also be employed. Colorants may be incorporated in the
compositions in amounts up to about 5% by weight of the ink.
The Resin Binder
The resins suitable for use herein are classified as epoxy-phenolic resins
and as especially epoxy ethers of bisphenols. Such resins are well known
in the art and are generally derived from the alkaline catalyzed reaction
of epichlorohydrin with said bisphenols. Such classic epoxy resins known
in the art as DGEBA resins are believed to have the form of a polyglycidyl
or diglycidyl ether of bisphenol A. The structure usually assigned to the
product is
##STR1##
Suitable products vary from epoxy resins of the monomeric diglycidyl ether
of bisphenol A (n=0) or similar materials wherein n=1, 2, 3 etc.
Especially preferred are low molecular weight epoxy-phenolic resins having
viscosities in the range of about 100 to about 500. The prime requirement
of the resin is that it must exhibit suitable solubility and compatibility
for incorporation in the ink compositions of this invention and be of
sufficiently low viscosity so that the viscosity of the ink is not
increased above about 3.0 centipoises. Particularly preferred are such
epoxy-phenolic resins available commercially under the trademark Varcum
from Reichhold Chemicals, Inc.
The resin component is critical herein since it is believed to convey the
properties permitting the ink compositions to exhibit the excellent
printing and adhesion properties, on a variety of substrates displayed by
the inks of the invention.
The Solvent Blend
Although minor amounts of other solvents may be included if desired, the
primary solvent blend is a mixture of (a) from about 25 to 40% of one or
more lower aliphatic monohydric alcohols such as methanol, ethanol or
propanol, (b) from about 0 to 20% of an organic compound selected from the
group consisting of low molecular weight glycol ethers, including ethylene
glycol monomethyl ether (commonly known as methyl cellosolve), ethylene
glycol monoethyl ether (cellosolve), propylene glycol monomethyl ether and
propylene glycol monoethyl ethers; (c) from about 0 to 40% lower aliphatic
ketones having 3 to 8 carbon atoms including methyl ethyl ketone,
2-heptanone, pentanone, 2-butanone, 2-hexanone and mixtures thereof and
(d) from about 5 to 20% water. All percents are by weight unless otherwise
specified.
The concentration of water in the composition is critical to the successful
practice of the invention since too much water will cause precipitation of
the epoxy-phenolic resin from the ink solution. Conversely, if a
sufficient amount of water is not present, the viscosity of the ink will
be too low and proper functioning of the composition in the ink jet
printing apparatus will be impaired. In general, concentrations of about
5% to about 15% will be satisfactory.
Other optional components may be added to the composition to convey special
characteristics.
A small amount of ammonia or similar alkalizing agent, in the form of
concentrated aqueous solution may be added when necessary to maintain the
system in a pH range of about 7 to 8.5. When used, such ammonia water
(26.degree. Baume) will be present in amounts of about 0 to 0.2% by weight
of the total ink composition.
Electrolytes are conventionally used in jet ink compositions to maintain
the specific resistivity of the ink within desired limits. The ink
compositions herein in most instances will have a specific resistivity
within the operable range without the necessity of adding an electrolyte
for this purpose. In general however, optimum results may be obtained by
addition of electrolytic components that are soluble in the ink medium and
which have no deleterious effect on the printing apparatus or on the
printed substrate. Satisfactory compounds for this use include dimethyl
amine hydrochloride, sodium propionate, sodium acetate, etc. with sodium
propionate being especially preferred. In general, an effective amount of
such electrolytic composition will be in the range of about 0 to about
0.1% of the composition.
The following examples are illustrative of ink compositions meeting the
end-use requirements discussed hereinabove and which are effective in jet
printing operations as herein described.
EXAMPLE 1
The following ink composition was prepared from:
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342 ml. Methanol
342 ml. Methyl Ethyl Ketone
127.3 g. Varcum 29-108 epoxy-phenolic resin
79 ml. Isopropanol
140 ml. Distilled Water
18.6 g Victoria Blue
0.939 g. Sodium Propionate
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The ink had a viscosity of 2.08 centipoises at 74.degree. F. and a
resistivity of 1080 ohm-cm. at 74.degree. F.
The ink was printed on (1) wire samples coated with various polymers (2)
glass and (3) coated and uncoated aluminum and steel using a jet ink
printing operation.
The ink dried within 5 seconds. After drying the printed substrates were
tested for adhesion and abrasion resistance by rubbing with an abrasive
felt employing a 2 lb. pressure at a speed of 30 to 60 rubs per minute.
The results were as indicated in the Table which follows:
Table
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Run No.
Substrate Rub-Resistance
Appearance
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1. Nylon Pass-Excellent
Excellent
2. Black High-Density
Pass Good printing
Polyethylene poor print
contrast on
black sub-
strate.
3. Black Ethylene-
Pass Good printing
Vinyl Acetate Code dif-
ficult to see
but visible
on black
surface.
4. Polyvinyl chloride,
Excellent Excellent;
Gray, yellow, Prints well;
Orange, white visible
5. White Silicone
Moderate Excellent
Rubber
6. Black Moderate Very dif-
Polychloroprene ficult to
see.
7. Glass Pass Excellent
8. Metal Pass Excellent
9. Metal Pass Excellent
10. Polyimide Pass Excellent
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EXAMPLE 2
The following ink compositions were prepared from:
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Ink 2A: Methanol 28.5%
Methyl ethyl ketone 29.0%
Varcum 29-108 epoxy-phenolic-resin
13.4%
Isopropyl alcohol 6.5%
Distilled Water 10.5%
Sodium propionate 0.1%
Ethyl Violet Dye 2.0%
Methyl cellosolve 9.8%
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The ink had the following properties at 24.degree. C.:
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Velocity of Sound: 1323 meters/second
Resistivity: 1200 ohm-cm.
Brookfield Viscosity:
2.05 cps.
Ink 2B Methanol 31.65
Methyl ethyl ketone
32.20%
Varcum 29-108 14.89%
epoxy-phenolic resin
Isopropyl alcohol
7.29%
Distilled Water 11.68%
Sodium propionate
0.11%
Victoria Blue FGA dye
2.18%
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The ink had the following properties at 24.degree. C.:
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Velocity of sound: 1319 meters/second
Resistivity: 1200 ohm-cm.
Brookfield Viscosity
2.10 cps.
Surface tension: 28 to 29 dyne-cm.
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The above inks were employed to print indicia on Kapton polyimide polymer
polymer coated wire by jet ink printing. After application, both inks
dried within 5 seconds. After drying, the wire printed with each ink was
tested and found to be abrasion-resistant to the extent that it remained
legible at a minimum distance of 15 inches in minimum daylight after 20
rubs with an abrasive felt employing a 2 lb. pressure at a speed of 30-60
rubs per minute. When the printed wire was immersed in a water solution
containing 5% NaCl and a potential of 2,000 volt rms. applied for one
minute between the primary conductor and an electrode, there was no
dielectric breakdown in the primary wire insulation and the indicia
remained legible. Indicia printed on the polymer coated wire remained
legible after a 24 hour exposure in a weatherometer to alternating cycles
of UV light and tap water spray.
During more than 800 hours of operation of Ink 2-A in the jet printing
units, evaporative losses from the ink supply system were compensated for
by the addition, as needed of a makeup composition containing about 1590
ml. methanol, 1893 ml. methyl ethyl ketone, 167 ml. isopropyl alcohol, 125
ml. distilled water and 11 ml. methyl cellosolve.
The above ink compositions were also employed to print indicia, by jet
printing, on aluminum and steel beer cans as well as on glass bottles.
EXAMPLE 3
The following ink compositions were prepared from:
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Ink 3A: Ethanol 400 ml.
Ethylene glycol monomethyl ether
40 ml.
Distilled water 44 ml.
Varcum 29-108 epoxy-phenolic resin
25 g.
26.degree. Baume ammonia water
2.5 ml.
Victoria Blue 4 gm.
Ink 3B: Ethanol 200 ml.
Methyl Ethyl Ketone 50 ml.
Distilled Water 25 ml.
26.degree. Baume ammonia
1.5 ml.
Varcum 29-108 12.7 g.
Sodium propionate 0.25 g.
Victoria Blue 2.0 g
Neozapon Black 2.0 g
Ink 3C: Methanol 89.5 ml.
Methyl Ethyl Ketone 89.5 ml.
Varcum 29-108 34.1 g.
Distilled Water 17.9 ml.
Isopropanol 21.3 ml.
Victoria Blue 5.0 g
Sodium Propionate 0.25 g
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The inks had the following properties:
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Ink 3A Ink 3B Ink 3C
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Brookfield
Viscosity:
1.80 cps. 1.57 cps. 1.72 cps.
Resistivity:
2600 ohm-cm.
1600 ohm-cm.
1100 ohm-cm.
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The inks 3A to 3C were employed in a jet printing apparatus to print
indicia on glass, Kapton polyimide and nylon/polyvinyl chloride surfaces.
The inks showed excellent adhesion, dried in less than 5 seconds and
exhibited good printability. Resistance to moisture and ultraviolet
radiation was excellent.
The above inks have been found to print on glass having condensed moisture
on its surface with good adhesion.
It will be seen from the aforegoing description of the invention that jet
ink compositions are provided that are characterized by extremely useful
adhesion and resistance properties making them suitable for use in a
variety of applications. As is evident from the examples, jet ink
compositions of the invention are readily suitable for use in printing
polymer coated wire of various types, in printing glass and/or ceramic
surfaces and in printing coated and uncoated metal surfaces.
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