Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: USE OF SURFACTANTS IN PASTE PRINTING INK
FIELD OF THE INVENTION
The present invention relates to paste printing
inks for use in lithographic printing processes in which
the printing inks may be cleaned by an aqueous cleaning
solution. The invention also relates to aqueous washing
solutions for cleaning such inks from the printing units
and the preferred method of cleaning.
BACKGROUND OF THE INVENTION
A wide variety of printing processes are in general
use, of which, one of the most common is the lithographic
printing process. Lithography is a method of printing
which relies on differences in solubility and surface
wetability between an oil based component, generally the
ink, and an aqueous based component, generally the fountain
solution, to transfer the printing ink to the desired image
area and prevent the ink from transferring to the non-image
area. Lithography commonly utilizes a printing plate which
is treated to provide an oleophilic or hydrophobic ink
accepting image area and an oleophobic or hydrophilic ink
repelling non-image area. During the lithographic printing
process, an oil based or water insoluble ink composition
and an aqueous fountain solution are applied to the
printing plate. The fountain solution is attracted to and
preferentially wets the oleophobic or hydrophilic non-image
areas while the ink is attracted to and wets the oleophilic
or hydrophobic image areas. Lithographic printing requires
inks which are water insoluble under the conditions
utilized by aqueous fountain solutions, which are generally
acidic in nature. If the ink does not have this water
insolubility, then there will be some bleeding of the ink
into the fountain solution which will result in poor print
quality, poor edge definition, dot gain and other various
print deficiencies. Thus, the lithographic inks are
generally formulated to remain stable, cohesive and
insoluble when in contact with aqueous solutions under the
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conditions commonly employed in the lithographic printing
process.
The ink composition and fountain solutions are
applied to the printing plate through a variety of methods
and roller configurations common in the art. Once applied
to the printing plate they are distributed to their
respective areas and transferred either directly to the
paper or an intermediate blanket cylinder which then
transfers the ink to the paper. The now obsolete direct
transfer of the ink from the printing plate to the paper is
known as direct lithographic printing while the transfer
going through the intermediate blanket cylinder is
generally referred as offset lithography. In offset
lithography, the blanket cylinder is covered with a
transfer substrate, typically rubber, which receives the
ink from the printing plate and transfers it to the print
substrate.
When a printing job is completed, the printing
plates are changed and the print train, especially the
transfer cylinder in an offset process, must be cleaned to
remove the ink residues which are present from the job. In
addition, during the printing job if a change of ink is
required, then the entire print train including application
rollers, print plates and the transfer cylinder must be
cleaned. In the past, such cleaning has generally been
accomplished using an appropriately formulated organic wash
solvent. It was necessary to use organic wash solvents to
effectively dissolve or sufficiently disperse the ink as
the inks themselves are oil based, water insoluble
compositions. In recent years, there have been pressures
to diminish the use of organic solvents in all printing
processes as such solvents are generally based upon
petroleum distillates. Inks and wash solvents produced
utilizing petroleum distillates suffer from a number of
major drawbacks. Petroleum is a non-renewable resource; an
organic solvent which gives rise to employee safety
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concerns as well as being a source of air and water
pollution since volatile organic compounds (VOCs) are
dispersed into the atmosphere or disposal system.
There have been attempts in the past to develop
water based wash or cleaning solutions in order to reduce
the presence of VOCs emitted during the washing process.
To date, the closest to achieving this goal has been the
processes and products developed by the Deluxe Corporation
as described in U.S. Patents 5,308,390, 5,382,282,
5,354,366 and 5,388,351. These patents describe ink
compositions incorporating a water reducible resin which is
water insoluble under certain conditions and selectively
water washable under other conditions. The resins are
selected to be water insoluble under the conditions
employed in fountain solutions, i.e. at acidic pHs, and
water washable under alkaline pHs. This is achieved by
utilizing a water reducible acid functional resin having an
acid number such that the resin is water insoluble at an
acidic pH level while being water soluble or water washable
at an alkaline pH level. The resin is preferably selected
to have acid numbers in the range of from about 25 to 200
and most preferably between 25 and 100. A surfactant may
be employed in the ink to reduce the amount of water
reducible resin needed to render the ink or varnish water
washable. The use of the water reducible resins have the
drawbacks of not being suitable for use in all printing
processes and not producing a higher quality print job as
compared to a ink formulated using a traditional hard
resin.
SUMMARY OF THE INVENTION
The present invention is based in part upon the
finding that the incorporation of a small amount of
surfactant in a typical paste printing ink renders the
paste printing ink water washable on clean-up without
requiring the addition of water reducible resins.
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In a preferred embodiment, the present invention
provides for a paste printing ink containing a suitable
solvent, a hard resin, pigment and other typical additives,
the improvement comprising the addition of a small amount
of at least one surfactant to the printing ink to enable
the ink to be water washable on clean-up.
In an aspect of the invention, there is provided a
method for cleaning the printing apparatus with an aqueous
cleaning solution, the method comprises utilizing a
conventional printing ink, to which a small amount of
surfactant has been added, in combination with an acidic
fountain solution and washing the printing apparatus with a
aqueous washing solution at a pH of between about 8.5 and
13.5, the washing solution containing some detergent and a
small amount of surfactant.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention is directed to a paste
printing ink for use in the lithographic printing process,
the paste ink being washable with aqueous wash solutions
during the clean-up, thus eliminating the need for wash
solutions based upon volatile organic compounds (VOCs).
The inks of the present invention are suitable for
use in a wide range of printing ink systems including
business forms inks, sheetfed inks, heatset inks, small
offset duplicator inks, coldset offset news inks, W inks
and metal decorating inks.
The inks of the present invention are based on
typical printing inks commonly utilized in lithographic
processes. Such printing inks contain a suitable pigment
in a printing ink vehicle. The insoluble pigment is a
colourant material which provides the colour and desired
level of transparency and is selected not to bleed into the
fountain solution. The printing ink vehicle carries the
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pigment and also holds it by binding to the substrate.
Such vehicles should be resistant to excessive
emulsification and must dry as required. The vehicle is the
medium in which the pigments and other additives are
suspended and is typically made up of hard resin, alkyd,
vegetable oil, petroleum distillate or other solvents, co-
solvent, rheological modifier and/or anti-oxidants in
certain ratio and provides the required gloss, film
integrity, suitable shelf life and end use requirements.
The hard resins of the ink contributes most to such
properties as setting, film integrity, hardness and gloss
of the film, the adhesion to the substrate and rub
resistance. The resins are selected based on properties
such as viscosity, solubility, compatibility, tack,
molecular weight, polarity, reactivity, colour and acid
value, which is preferred to be relatively low.
Preferably, the acid value of the resin will be less than
35 and generally on the order of 15 to 25. Types of resins
commonly utilized in printing inks include rosin
derivatives, specifically gum rosin, wood rosin and tall
oil resin with gum rosin being the most preferred.
Amongst conventional ink resins are rosin derived
resins, in particular, esters of rosin and modified rosin,
synthetic rosin modified hydrocarbon resins and cyclized
rubber. As will be readily appreciated by those of skill
in the art, the choice of the particular resin to be
utilized in the printing ink vehicle will be made on the
basis of the desired properties of the finished product,
namely the printed material.
Preferred hard resins for the printing ink vehicles
of the present invention are those derived from rosin, in
particular, esters of rosin, more particularly, esters of
phenolic modified rosin, esters of rosin adducts and esters
of dimerized rosin, most particularly esters of phenolic
modified rosin. All of these resins are commercially
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available for example, esters of phenolic modified rosin
are available under the trademarks PENTREX 1200 (Hercules
Inc.), KRUMBHAAR K-2300 (Lawter International, Inc.) and
FILTREZ 682 (Akzo Coatings Inc.). Esters of rosin adducts
are available under the trademarks PENTALYN G, PENTALYN X
and PENTREX 816 (all from Hercules Inc.) and KRUMBHAAR K-
333 (Lawter International, Inc.), while an ester of
dimerized rosin is available under the trademark PENTALYN K
(Hercules Inc.)
The vehicle may also optionally include synthetic
hydrocarbon resins including functional hydrocarbon resins
and non-functional hydrocarbon resins. The functional
hydrocarbon resins are resins which contain functional
groups and are utilized to increase the unsaturation for
inks which dry by oxidation such as sheetfed inks. Such
resins may also increase the acidity required for gelation.
Non-functional hydrocarbon resins, specifically aromatic
hydrocarbon resins or aliphatic hydrocarbon resins, are
generally utilized in heatset inks and may be used in
letterpress and web offset inks and news inks as well.
The printing vehicles may also contain oils of
various types, of which, vegetable oils are the most
commonly used. Oils are generally used according to their
drying property and may be divided into drying oils, semi-
drying oils or non-drying oils. Linseed oil is the most
commonly used drying oil. Alkali refined linseed oil is
preferred as it has a lower acid value than acid refined
linseed oil and gives good flow, quick setting, good
durability, color retention and water resistance. A small
percentage of such oil may be used when minimum penetration
is required as it can lead to reducing problems such as
chalking or piling.
Alkyd, namely, polymeric esters resulting from the
condensation of a polyhedric alcohol or polyol with a
dibasic acid or a monobasic fatty acid derived from
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triglycerides and vegetable oils may be employed in the
printing ink vehicles. Alkyds generally are utilized for
the provision of oxidative drying sites for fast drying
active sites for gelation. They also increase the
solubility of the system utilizing insoluble esters of
phenolic modified rosin and improved pigment wetting.
Alkyds may also increase the adhesion or binding to the
substrate and increase the percent solids of the vehicle.
Alkyds present in the vehicle result in a dried film of
increased toughness, mar resistance and durability.
A major proportion of the vehicle is generally the
solvent component. In many cases, the solvents utilized
are petroleum derived, however, there may also be other
organic compounds which will act as a solvent such as, for
example vegetable oil fatty acid esterified with a simple
alcohol or glycol as is described in commonly assigned U.S.
Patent 5,178,672. When utilizing a petroleum distillate as
a solvent, properties such as boiling range, aromatic
content, viscosity and chemical composition are important
and affect the properties of the vehicle formulated. As
the boiling point of a petroleum distillate increases, the
solvency power decreases. For heatset inks and vehicles, a
solvent volatile enough to evaporate at the required oven
temperature is selected to provide the most consistent and
quickest drying. The aromatic contents and chemical make-
up of the solvent affects the solvent and vehicle
properties and its viscosity. For example, large amounts
of aromatics in a solvent increases the solvency and
dilutability of the vehicle but decreases the tack and
viscosity. In contrast, isoparafins have low solvency and
dilutability with high tack and tack stability. These
properties are taken into account depending upon the type
of ink to be manufactured and the inks' desired properties.
The vehicle may also contain rheological modifiers
such as gelling agents to help lower the misting properties
of a printing ink and to contribute to a faster setting
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printing ink as well as controlling the flow properties of
the ink. Such gelling agents are typically organometallic
compounds of aluminum or polyamide resins. Preferred
gelling agents for the vehicle of the present invention are
the organometallic compounds of aluminum, in particular,
aluminum soaps, aluminum alkoxides or oxyaluminum acylates,
most preferably, oxyaluminum acylates such as oxyaluminum
octoate. V,~hen utilizing a gelling agent in the vehicle,
proper manufacturing considerations should be followed.
Such considerations include manufacturing under an inert
atmosphere, pre-dilution of the gelling agent with the
solvent and slow addition of the pre-diluted gelling agent
to the agitating vehicle.
Anti-oxidants may be added to the vehicles to
retard auto-oxidation to prevent premature skinning of both
the vehicle and the printing ink. Preferred such anti-
oxidants are butylated hydroxy toluene (BHT) or
hydroquinone.
One or more driers may also be added to aid in the
oxidation drying of the ink film. Such Briers are
preferably metal salts of acylates, more preferably cobalt
and manganese metal salts of octoates.
With respect to an individual printing ink
vehicle to be utilized in formulating the paste printing
ink, the solvent, in particular, the petroleum solvent or
esterified vegetable oil fatty acids will generally
comprise about 20 to 80~ of the printing ink vehicle, more
preferably about 30 to 70~, most preferably about 40 to
60~. The hard resin will generally be present in
concentrations from about 15 to 65~, most preferably about
30 to 60~. The printing ink vehicle may also include other
solvents such as, for example, vegetable oils. Such
vegetable oils may be present in concentrations up to about
20~, most preferably up to about 10~. Liquid resins,
called alkyds, may also be present in the printing ink
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vehicle. These liquid resins are vegetable oil modified
polyesters which may be used to help improve film
flexibility and durability. Such alkyds may be present in
concentrations up to about 25~, most preferably up to about
10~. Then a gelling agent is present in the vehicle, the
gelling agent is provided in concentrations up to about 2~,
most preferably about 0.5 to 1.5~ of the composition.
The paste printing ink according to the
invention is prepared in a conventional manner by mixing
one or more individual printing ink vehicles and other
components in suitable percentages.
More particularly, the printing ink vehicle of
the formulated printing ink will preferably contain the
solvent in a concentration range of 15 to 40~, more
preferably 20 to 35~, hard resins in a range of 15 to 25~,
other solvents such as vegetable oil in a range of 0 to
15~, more preferably 5 to 10~, gelling agents in a range of
0 to 1~, more preferably 0.5 to 1.0~, waxes in a
concentration of up to about 5~, more preferably up to 3~
Briers in a concentration of up to 5~, more preferably 1 to
3~ and the surfactant in an amount sufficient to render the
ink washable with an aqueous solution on clean-up. The
concentration of pigment in the printing ink will generally
be in the range of 10 to 30~, more preferably 15 to 20~.
The printing inks of the present invention include
a surfactant present in an amount sufficient to render the
ink washable with an aqueous solution on clean-up. The
surfactant may be non-ionic, catonic or anionic with non-
ionic surfactants to be preferred. The preferred non-ionic
surfactants are Cg to C14 acetylinic diols or glycols,
alkoxy polyethoxyethanol, the ethylene oxide addux of
primary or straight chain alcohols. Types of non-ionic
surfactants are block copolymer surfactants (PluronicTM and
TetronicTM), polyether surfactants (PluradotTM),
polyethylene glycols (Pluracol E1'M), polypropylene glycols
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( Pluracol PTM) , polyalkoxylated polyethers ( Pluracol V~TrM) ,
linear alcohol alkoxylates (PlurafacTM), alkylphenol
ethoxylates (IconolTM), alcohol alkoxylates (IconolTM Decyl
and Tridecyl), fatty alcohol ethoxylates (IndustrolTM),
fatty amine ethoxylates (IcomeenTM), polyethylene glycol
fatty acid esters (IndustrolTM), castrol oil ethoxylates
(IndustrolTM), sorbitan fatty acid esters (KuplurTM),
sorbitan ester ethoxylates (IndustrolTM), phosphate esters
(KlearfacTM and IndoilTM), alkoxylated phenolic compounds
(IconolTM), sorbitol esters (IndustrolTM), sorbitol ester
ethoxylates (Twi~'M), fatty acid alkanolamides (IconolTM)
and fatty amide ethoxylates (IcomidTM). Such surfactants
are commercially available, for example from Air Products
and Chemicals Inc., specifically SurfynolTM 104 or
SurfynolTM 61 as well as other members of the SurfynolTM
series. Other examples of non-ionic surfactants are the
PluronicTM and TetronicTM - Block Copolymer surfactants
available from BASF under the trade names L-61, L-62 and L-
82. All of the surfactants generally have HLB values at
25°C of from 0.5 to 7Ø
In addition to the non-ionic surfactant, cationic
surfactants may also be utilized such as cetyl trimethyl
ammonium salts, in particular, cetyl trimethyl ammonium
chloride. Anionic surfactants may also be utilized
although they do tend to get hydrolized in alkaline
solutions. Anionic surfactants are suitable if used in
moderate quantities of between 0.25 and 1.50 percent. One
example of such an anionic surfactant is sodium dioctyl
sulfo succinate available from Air Products and Chemicals
Inc. under the trade name Aerosol - OT.
The surfactant is generally present in a range from
about 0.25 percent to about 8.0 percent, more preferably
0.5 to 2.5 percent, most preferably about 2.0 percent.
Another aspect of the present invention relates to
the aqueous clean-up of the print train utilizing the
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printing ink of the present invention. The aqueous clean-
up is accomplished utilizing an aqueous based cleaning
solution at a pH of between about 8.5 and about 13.5, most
preferably at a pH of 10 ~ 1Ø The washing solution
utilizes a detergent cleaner preferably a non-halogen
biogradable cleaner utilizing a terpene such as d-limonene.
One example of such a detergent product is that available
under the trade name MAZCLEANTM "W" from PPG. MAZCLEANTM is
present in the washing solution at a concentration of about
10 to 35 percent by volume. In addition, the washing
solution also contains a surfactant, preferably a cationic
surfactant, such as cetyl triethyl ammonium chloride, or an
anionic surfactant such as sodium dioctyl sulfo succinate
available from Air Products and Chemicals Inc. under the
trade name Aeroso l - OT at a ratio of 0.25 to 3.0
percent, preferably 0.5 to 2.0 percent, most preferably
about 2.0 percent. In order to maintain the pH of the
washing solution, a buffer is generally utilized,
preferably a sodium bicarbonate/carbonate buffer at a
concentration of about 1.0 to 2.0 percent. The washing
solution may also contain anti-foaming agents, and
depending upon the detergent utilized, may also contain
masking agents such as #91894 MASKTM from Stanley S.
Schoenmann Inc.
The following examples illustrate preferred
embodiments of the present invention but the invention is
not limited thereto. All percentages are based on weight.
Typical Heatset Lithographic inks formulated in
accordance with the present invention will contain:
Pigment Red 57:1 15 - 20~
Hard Resin* 20 - 15~
Soya Oil Phthalic Alkyd 4 - 6~
Alkali Refined Linseed Oil (A.R.L.O.) 2 - 3~
Polyethylene Wax 2 - 3~
Aluminum Gellant 0.5~
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Antioxidant (eg. BHT) 0.2~
Petroleum Distillate (eg. 470 oil) 35 - 40~
Surfynol 104HTr' ~ 2~
* The resins generally used are neutral and/or
functional hydrocarbon type, malefic and
phenolic modified rosin esters.
A sheetfed lithographic formulation contains:
Pigment Red 57:1 15 20~
-
Hard Resin* 25 30~
-
Linseed Oil Alkyd 20 25~
-
Wax (eg. Polyethylene, PTFE) 2 3$
-
Antioxidant 0.1~
Driers (eg. Cobalt, Manganese type) 0.5 - 1.5~
Aluminum Gellant 0.25 - 0.5~
Petroleum Distillate (eg. 535 type) 35 40~
-
Pluronic L-62TM ~
5~
* The resins generally used are functional
hydrocarbon type, malefic and phenolic
modified rosin esters.
A coldweb news ink formulation according to the
present invention contains:
Pigment Red 57:1 10 - 15~
Neutral Hydrocarbon Resin 15 - 20~
Clay 10 - 15~
Mineral Oil 50 - 60~
Cetyl Trimethyl Ammonium Chloride ~ 2.5~
A small offset/duplicator ink formulation contains:
Mineral Oil 10 - 15~
Hard Resin 20 - 30~
Alkyd 5 - 10~
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Linseed Oil 5 - 10~
Pigment Black 7 25 - 30~
Pigment Blue 61 3 - 6~
BHT 0.2~
Petroleum Distillate 5 - 10~
Pluronic L-62T°' 5 , 0~
A business forms offset ink formulation contains:
Mineral Oil 10 - 15~
Hard Resin 20 - 30~
Alkyd 5 - 10~
Linseed Oil 5 - 10~
Pigment Black 7 25 - 30~
Pigment Blue 61 3 - 6~
BHT 0.2~
Petroleum Distillate 10 -15~
Surfonyl 104HTM 2.0~
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EXAMPLE 1
ACYAN PROCESS PASTE PRINTING INK
30 kg of a functional hydrocarbon resin solution in
mineral oil (33.5 resin solids) was weighed into a pot
along with 20 kg of a linseed oil/rosin modified phenolic
resin body gum vehicle and 5 kg of a linseed oil
isophthalic alkyd. These ingredients were mixed well on a
mixer and 5 kg of 535 type petroleum distillate was added
into the vortex. 28 kg of C.I. Pigment Black 7 along with
4 kg of C.I. Pigment Blue 61 were added slowly into the
vortex and mixed until a temperature of 85°C was achieved.
The product was then milled on a vertical shot mill to
achieve a dispersion of 2/0 or better on an NPIRI Grind
Gauge. The milled product was placed back on the mixer
where 5 kg of 535 type petroleum distallate, 1 kg of 20~
BHT in Linseed Oil and 2 kg of Surfonyl 104H were added to
the vortex. The product was packaged into metal cans by
passing it over a 3-roll mill.
In a similar manner as the above example, the
following inks were prepared.
EXAMPLE 2
A heatset lithographic ink formulation was prepared
containing:
C.I. Pigment Red 57:1 15
Hard Resin 23
Soy Oil Isophthalic Alkyd 5
Alkali Refined Linseed Oil 3
Polyethylene wax 2
Microcrystalline wax 1
Petrolatum 3
OAO Aluminum Gellant 0.5
BHT Antioxidant 0.2
470 Type Petroleum Distillate 27.3
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500 Type Petroleum Distillate 18
Surfonyl 104H 2
EXAMPLE 3
A sheetfed lithographic ink formulation was
prepared containing:
C.I. Pigment Red 57:1 19
Hard Resin 24
Linseed oil Isophthalic Alkyd 12
Polyethylene Wax 2
Polytetrafluoroethylene Wax 1
Hydroquinone antioxidant 0.1
7~ Cobalt Octoate Drier 0.9
6~ Manganese Octoate Drier 0.9
OAO Aluminum Gellant 0.5
535 Type Petroleum Distillate 34.6
Pluronic L-62 5
EXAMPLE 4
A coldset offset news ink formulation was prepared
containing:
C.I. Pigment Red 57:1 13
Neutral Aromatic Hydrocarbon Resin 20
Clay 1g
Mineral Oil 46.5
Cetyl Trimethyl Ammonium Chloride 2.5
EXAMPLE 5
A small offset/duplicator ink formulation was
prepared containing:
Mineral Oil 15
Hard Resin 22
Linseed Oil Isophthalic Alkyd 10
Heat Bodied Linseed Oil (Z Viscosity) 7
C.I. Pigment Black 7 27
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C.I. Pigment Blue 61 4
BHT Antioxidant 0.2
535 Type Petroleum Distillate 9.8
Pluronic L-62 5
EXAMPLE 6
A offset business forms ink formulation was
prepared containing:
Mineral Oil 12
Hard Resin 22
Linseed Oil Isophthalic Alkyd 10
Heat Bodied Linseed Oil (Z Viscosity) 7
C.I. Pigment Black 7 27
C.I. Pigment Blue 61 4
BHT Antioxidant 0.2
535 Type Petroleum Distillate 15.8
Surfonyl 104H 2.0
EXAMPLE 7
A typical aqueous cleaning solution was prepared
containing:
10:1 Sodium Carbonate/Bicarbonate 2~
MAZCLEAN "W" 16$
Sodium Hydroxide (pH 9.5 ~ 0.2) 2~
Surfactant Solution 2~
Water 7g~
The Sodium Hydroxide Buffer Solution was prepared
by adding 51.5 g of Sodium Hydroxide, 18 g of sodium
carbonate and 2 g of sodium bicarbonate to 1 1 of water,
heated to 50°C and mixed well till fully dissolved. The
Surfactant Solution was prepared by adding 25 g of Aerosol
OT to 100 ml of water, mixed and shaken vigorously till
fully dissolved.
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The aqueous cleaning of the print train is
accomplished following a normal run by first disengaging
the rollers from the substrate, the web or the sheet. A
small quantity of washing solution, typically 20 to 50m1
depending upon the length of the roller, is applied to the
roller and the rollers are allowed to rotate for a short
period of time, typically 30 seconds to 2 minutes. During
this time, the ink on the rollers starts to solubilize.
Once the ink is solubilized, the doctor blades are engaged
with the rollers to remove the solubilized ink film.
The printing ink and the method of washing of the
present invention result in a rapid and simple clean-up
operation of a print train which may be accomplished in one
step only without the utilization of any solvent which
contain VOCs. In testing, it has been found that the
method of the present invention utilizing the aqueous
clean-up solution provides a similar degree of wash-up as
that is achieved utilizing the volatile solvents of the
prior art.
Although various preferred embodiments of the
present invention have been described herein in detail, it
will be appreciated by those skilled in the art, that
variations may be made thereto without departing from the
spirit of the invention or the scope of the appended
claims.
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