Note: Descriptions are shown in the official language in which they were submitted.
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FOUNTAIN SOLUTIONS
Field of the Invention
This invention relates to fountain solutions,
more specifically to fountain solutions which contain
or are used with alcohol substitutes.
Backaround of the Invention
The offset lithographic printing process
employs planographic plates which transfer ink to a
blanket roll which, in turn, then transfers the ink ~o
a substrate thereby forming the printed images. The
plates are referred to as planographic since the image
and non-image areas are in the same plane. The plates
are constructed so that with proper treatment the
images are hydrophobic and oleophilic and thereby
receptive to inks. The non-image areas are hydrophilic
and are water receptive. In order to maintain the
hydrophilic characteristics on the non-image areas, and
to prevent ink from accumulating on the non-image
areas, it is necessary to continuously treat the plate
with a water based fountain solution.
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The aqueous fountain solution is used to
maintain the non-image areas of a lithographic printing
plate insensitive to ink. While an offset printing
press is running, fountain solution is continuously
applied to the printing plate just before the
application of the printing ink, or as a water in ink
emulsion. The fountain solution has an affinity for
the non-image, hydrophilic areas of the plate and
immediately wets these areas. A complete and uniform
film of fountain solution prevents the subsequent
application of ink from covering the plate in the non-
image areas. The fountain solution and ink on the
plate are then both transferred to the blanket and then
to the printing substrate and the process begins again.
Lithographic printing plates are developed to
expose metal surface in the non-image areas while image
areas are left coated with a hydrophobic polymer.
There are many fountain solutions which contain highly
polar liquids which will wet and coat the exposed metal
surface of the non-image area of the plate. Plain
water may temporarily perform fairly well, although
various aqueous electrolytes, surfactants and water
soluble polymers are generally required for good
continuous performance. These additives promote plate
wetting and fountain solution uniformity, as well as
controlling the interaction of the fountain solution
with the ink and the substrate.
Acid fountain solutions are the most widely
used in commercial printing. Alkaline fountain
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solutions are primarily used for newspaper printing.
While there is a trend toward more neutral pH fountain
solutions, acidic solutions continue to be widely used
because of the proven effectiveness of gum arabic, a
water soluble polymer. Gum arabic is a protective
colloid that desensitizes the non-image areas of the
plate. Since gum arabic is best solubilized and most
effective under acidic conditions, acidic fountain
solutions continue to be preferred.
Many lithographic presses have a fountain
solution distribution system that is separate from the
ink distribution system. Generally, the conventional
fountain solution distribution system includes a ductor
roller which has intermittent or interrupted flow of
the fountain solution from the reservoir to the
dampening form rollers that contact the printing plate.
Often these conventional dampening systems use paper or
molleton ~cloth) covered rollers or specially treated
rollers in the dampening system roller train to act as
intermediate fountain solution reservoirs. Alternately
brushes can flick droplets of water onto form rollers
or directly onto the plate or nozzles can similarly
spray a fine-mist.
A growing number of lithographic presses are
equipped with a continuous feed dampening sy~tem sold
A by Dahlgren Mfg. Co., Dallas, TX, under the t~a~cn-~mc
Dahlgren. Other dampening systems of the direct
continuous type include the system sold by Miehle-
Gross-Dexter, Chicago, IL, under the trademark
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Miehlematic, and by Harris Corp., Cleveland, OH, under
the trademarks Duo-Trol and Microflow and by Miller
Western Mfg. Co., Pittsburgh, PA, under the trademark
Millermatic.
In the Dahlgren system, the printing plate is
contacted only by inked rollers~ that is, the fountain
solution must be carried from the dampening unit
rollers by means of one or more inked rollers, usually
one of the form rollers, to the printing plate. This
type of system requires the assistance of a water
transport additive such as a water soluble glycol as
disclosed in U.S. Patent No. 3,625,715 or an alcohol
such as disclosed in U.S. Patent No. 3,168,03?, with
isopropyl alcohol being almost universally used. The
excellent and more independent control of ink and water
delivery to the printing plate accounts for the ever
increasing use of this type of dampening system in
lithographic printing. This, in turn, accounts for the
extensive use of isopropyl alcohol in Dahlgren
continuous dampening systems. Typically, the fountain
solution will contain between about 10 to 30 percent
isopropyl alcohol depending upon the specific press,
speed, type of form and substrate being printed. The
use of isopropyl alcohol is the best compromise between
good press and printing performance and cost of the
fountain solution.
Another variety of a continuous contact
dampening system is the Millermatic type wherein the
fountain solution is applied to the printing plate by
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means of a dampener form roller that is not part of the
inking system. With such an arrangement it would be
expected that isopropyl alcohol would not be required
because the inked form roller is not used to distribute
the aqueous fountain solution. Because, however, of
the excellent ink and water balance control, it is also
common to use isopropyl alcohol as a constituent in the
dampening solution used with the Millermatic type of
dampener.
The typical fountain solution is made up from
a fountain solution concentrate, water and an alcohol
or alcohol substitute. The fountain solution
concentrate generally includes buffering salts,
protective colloids, i.e. water-soluble resins or gums
such as gum arabic or cellulose gum and frequently a
surfactant (wetting agent). The preferred fountain
solutions are generally acidic and include acidic
components such as phosphoric or citric acid to
maintain a pH value between about 3.5 and 5.5, although
neutral and basic fountain solutions are also useful.
Alcohol (isopropanol) and alcohol substitutes
are commonly added to fountain solutions. These
additions are required with certain types of continuous
dampening systems (Dahlgren, Duo-Trol, Miehlematic,
etc.). Even with conventional systems, smaller amounts
of alcohol have proven to be beneficial. Generally
speaking, alcohol will make a borderline dampening
solution work better by solubilizing the surfactant and
lowering the surface tension of the water, thereby
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increasing the wetting action of the dampeninq
solution. Also, it minimizes the fountain solution use
while maintaining moisture on the plate surface.
Reduced water pickup makes it easier for the pressman
to maintain the correct ink/water balance. Also, the
rapid evaporation of the alcohol from the film of
fountain solution on the blanket and printed sheet
helps to minimize the paper's tendency to curl.
Generally about 10 to 30% of a fountain solution can be
isopropanol.
Environmental concerns about press room
emissions as well as the cost of alcohol have led to
the use of alcohol substitutçs. These can perform
some, but generally not all, of the functions of
isopropanol. Because of these concerns for isopropyl
alcohol, a number of materials have been suggested as
replacements in fountain solutions. Additives such as
2-butoxy ethanol and ethylene glycol have been used as
substitutes for isopropyl alcohol. U.S. Patent
3,877,372 discloses a fountain solution which includes
2-butoxy ethanol and at least one o~ hexylene glycol
and ethylene glycol, a silicone glycol copolymer and a
defoamer type surfactant. U.S. Patent 4,278,467
discloses an isopropyl alcohol-free fountain solution
which includes an additive having a surface tension
less than about 50 dynes/cm such as n-he~xoxydiethylene
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glycol (n-hexyl cell~oso~lve)~, n-)hexoxydiethylene glycol
(n-hexyl carbitol)~, 2-ethyl-1,3-hexanediol,
n-butoxyethylene glycolacetate, n-butoxydiethylene-
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- glycolacetate, 3-butoxy-2-propanol and mixtures
thereof. U.S. Patent 4,560,410 discloses a fountain
solution containing a mixture of a polyol and/or glycol
ether partially soluble in water with a polyol and/or
glycol ether completely soluble in water.
- The use of higher boiling solvents such as
glycols, glycol ethers and glycol ether acetates as
alcohol substitutes in fountain solutions has resulted
in a higher dynamic surface tension because of the
limited solubility of the surfactants in these systems.
The higher dynamic surface tension reduces the
performance and effectiveness of the fountain solution
due to decreased wetting action at press speeds. In
addition certain fountain solution concentrate systems
containing alcohol substitute systems cannot be
supplied in a one step form because of precipitation of
one or more components when mixed with the alcohol
substitutes. This type of one-step fountain solution
concentrate is desirable because of the simplicity of
metering it on existing dilution equipment.
Further, fountain solutions contain alcohol
and alcohol substitutes to dissolve surfactants in an
a~ueous system. It would be desirable to be able to
dissolve surfactants in an aqueous system while
eliminating or reducing alcohol or alcohol substitutes
to avoid the environmental problems they cause as well
as the lithographic problems caused by their
evaporation.
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SummarY of the Invention
Briefly, this invention involves the use of a
hydrotrope to increase the solubility of a surfactant
in an aqueous fountain solution or fountain solution
concentrate. The hydrotrope is added to an aqueous
fountain solution or fountain solution concentrate ~
containing a surfactant. By this invention the use of
alcohol or alcohol substitutes can be eliminated or
reduced and if used in combination with an alcohol
substitute system, performance and effectiveness of the
fountain solution can be enhanced.
Detailed Description of the Invention
It has now been found that when a hydrotrope
is added with a surfactant to a fountain solution or
fountain solution concentrate, the solubility of the
surfactant is increased thus lowering the dynamic
surface tension and enhancing the wetting action and
performance of the fountain solution during the
;~ lithographic printing process.
The hydrotrope is a salt of a hard acid-soft
~ase or soft acid-hard base and is an electrolyte
generally with an inorganic and an organic ion.
Descriptions of hard and soft acids and bases are
contained in Survey Of Progress In Chemistry (edited by
A. Scott, Academic Press, Vol 5, 1969, pp. 1-52). The
action of the hydrotrope is to assist in the
solubilization of an insoluble phase (i.e. a
surfactant) in a second phase (i,e. water). Preferaoly
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the hydrotropes selected in addition do not increase
the hydrophilic-lypophilic balance (HLB Value) of the
fountain solution which would interfere with the
lithographic printing process. Suitable hydrotropes
include, but are not limited to, sodium toluene
sulfonate, sodium xylene sulfonate, sodium cumene
sulfonate, ammonium xylene sulfonate, tetrabutyl
ammonium bromide, cetyl trimethyl ammonium bromide and
sodium thiocyanate. Mixtures of hydrotropes may also
be used.
The hydrotrope is used in an amount effective
to increase the solubility of the surfactant,
preferably to maintain the surfactant dissolved in the
fountain solution and fountain solution concentrate.
Generally the amount of hydrotrope to surfactant is
within the range of 1:1 to 10:1 by weight, preferably
4:1 to 6:1 by weight.
The use of the hydrotrope to increase the
solubility of a surfactant reduces the dynamic surface
tension of the fountain solution, thus enhancing its
performance during lithographic printing. In general
the addition of an effective amount of hydrotrope will
reduce the dynamic surface tension of the fountain
solution by at least 5 dynes/cm, preferably at least
10 dynes/cm, as measured at a surface age of 200
milliseconds with a Sensadyne (TM) Surface Tensiometer
5000 manufactured by Chem-Dyne Research Corporation,
Milwaukee, Wisconsin. The resultant fountain solution
will generally have a dynamic surface tension of less
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than 40 dynes/cm, preferably 28 to 35 dynes/cm, as
measured above. Common commercial dampening solutions
containing alcohol replacements generally have dynamic
surface tensions in the range of from greater than 35
to 65 dynes/cm, as measured above.
- The fountai~ solution or fountain solution
concentrate contains surfactants or wetting agents
which are added in amounts effective to lower the
surface tension and to control emulsification ability
and capacity thus ma~ing the fountain solution more
efficient in dampening the lithographic plate. A wide
range of surfactants can be used, even surfactants
which were previously unsuitable because of their low
; solubility in aqueous fountain solutions. Suitable
surfactants include non-ionic and/or ionic surfactants
such block copolymers, aikyl phosphates, ethoxylated
alcohols, fatty acids, amines, amides, fatty esters,
alkanol amides, glycol esters, sorbitan fatty acid
esters, ethoxylated alkyl phenols and ethoxylated
acetylenic glycols, as well as mixtures thereof. In
general, the amount of surfactant will range from 0.05
to 20% by weight of the fountain solution concentrate
and from 0.001 to 1% by weight of the fountain
solution.
~- The fountain solution or fountain solution
' concentrate generally contains several other
; ingredients. These can include protective colloids,
i.e. water-soluble polymers, in particular water-
~ soluble gums which contain carboxyl and hydroxyl
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groups. Gum arabic is the oldest and most widely used
polymer and is typically added as a 14 Baume'
solution. Carboxvmethyl cellulose, hydroxyethyl
cellulose as well as styrene maleic anhydride
copolymers, polyvinyl, pyrrolidone, and the like, may
also be used. These polymers are g~nerally used to
protect the non-image areas of a plate from
contamination from ink and to maintain the area
hydrophilic. In general, the amount of protective
colloid will range from 5 to 25% by weight of the
fountain solution concentrate and 0.1 to 2% by weight
of the fountain solution. The protective colloids are
generally added to acidic fountain solutions.
The fountain solution or fountain solution
concentrate can also contain buffering salts effective
to maintain a desired pH. The fountain solutions are
preferably used as aqueous acidic solutions having a pH
of about 3.5 to 5.5. Phosphoric acid is a preferred
acid for use in acidifying the formulation. Other
acids which can be used include inorganic as well as
organic acids, such as acetic acid, nitric acid,
hydrochloric acid, citric acid and the like. The
buffering salts can include ammonium acetate, magnesium
nitrate, zinc nitrate, sodium sulfate and disodium
hydrogen phosphate. The fountain solution can also be
neutral or alkaline as desired and contain suitable
buffering salts to maintain a desired pH such as sodium
hydrogen phthalate, potassium hydrogen phosphate and
sodium or potassium silicates.
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Other additives which may be used in the
fountain solution or fountain solution concentrate
include preservatives such as dimethoxane, phenol,
sodium salicylate, and the like; corrosion inhibitors
such as ammonium bichromite, magnesium nitrate and the
like; anti-foaming agents; and dyes, as welL as other
additives which are common in the art.
The fountain solution or fountain solution
concentrate can also contain an alcohol or alcohol
substitute. While an alcohol such as isopropanol or
alcohol substitutes can be used, the hydrotrope in
combination with the surfactant reduces the dynamic
surface tension sufficiently to be able to reduce or
eliminate their use. Preferably alcohol comprises less
than 5% by volume of the fountain solution.
Advantageously the addition of hydrotrope increases the
efficiency of fountain solutions containing alcohol
substitutes and also eliminates precipitation problems
~' allowing the use of one step formulations which contain
alcohol substitutes. Generally alcohol replacements
can comprise up to 75~ by volume,of a fountain solution
concentrate and up to 10% by volume of a fountain
solution. Typical alcohol replacements include
2-butoxy ethanol, n-hexoxyethanol, ethylene glycol,
2-ethyl-1,3-hexanediol and mixtures thereof.
Typically, the fountain solution contains 1
to 10% by volume of the fountain solution concentrate
(or etch). The fountain solution concentrate is
diluted with water, with additional dilution with an
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alcohol or alcohol replacement if desired to obtain the
fountain solution which is ready for lithographic
printing.
The addition of hydrotrope to the fountain
solution resulting in increased solubility of the
surfactant and a reduction in the dynamic surface
tension at press speeds has resulted in a number of
major advantages including a wider latitude with
regards to the amount of water use (i.e. wider water
balance) and the ability to greatly reduce the water
ùsage. In addition, other advantages which have been
observed include faster clean-up of the lithographic
plates, reduced and more easily removed pilings on the
non-image area of the blanket and cleaner fountain
solution sumps due to reduced ink feedback.
Exam~le 1
The addition of a hydrotrope allows one to
prepare a composite one step fountain solution
concentrate without precipitation of solids occurring.
The following fo~mulation was prepared. A
fountain solution concentrate was prepared containing
77% by weight water, 11% by weight gum arabic, 7% by
weight magnesium nitrate, 1.4% by weight citric acid,
1.3% by weight phosphoric acid (85% solution), 1.2% by
weight disodium hydrogen phosphate and 0.25% by weight
block copolymer of ethylene oxide/propylene oxide plus
0.2% by weight preservatives and anti-foaming agents.
Upon addition of 2 1/2 oz. (74 ml.) of the concentrate
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to 4 oz. (118 ml.) of alcohol replacement (containing
34% by weight ethylene glycol, 58~ by weight
2-butoxyethanol, ~.6% by weight 3,5-dimethyl-1-hexyn-
3-ol and 2.9% by weight 2,4,7,9-tetramethyl-5-decyne-
4,7-diol) added per gallon (3.8 1) of water a
precipitate was formed. The further addition of 3 ozO
(89 ml.) of ammonium xylene sulfonate (42% by weight
solution in water) led to solution of the precipitate
and a uniform product.
The dynamic surface tension of the diluted
fountain solution containing hydrotrope was 29.5
dynes/cm at a surface renewal rate of 200 milliseconds
as measured with a Sensadyne Surface Tensiometer 5000.
Without the addition of hydrotrope, the fountain
solution had a dynamic surface tension of 35 dynes/cm,
as measured above, despite the fact that the hydrotrope
is not surface active.
In a sheet fed press trial, using a Dahlgren
dampening system the above fountain solution with
hydrotrope ran with a water balance of 15 notches
(70-85) with catchup at 65 notches. A 15 notches water
balance is a wide water balance which allows efficient
lithographic performance.
Exam~le 2
Utilizing a 2-step process (i.e. dilute
concentrate with water then add alcohol replacement) on
a Miehle Press a fountain solution containing 2 1/2
oz./gallon of the fountain solution concentrate of
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Example 1 with 2 1/2 oz./gallon of the alcohol
replacement of Example 1 did not run with any water
control on a Dahlgren dampening unit indicating the ink
would not lithograph with this fountain solution. This
fountain solution had a dyn~mic surface tension of 39
dynes/cm as measured above.
The addition to the fountain solution of
2 1/2 oz./gallon of hydrotrope (an aqueous solution
containing 42% by weight of equal amounts of sodium
cumene sulfonate, sodium toluene sulfonate and ammonium
xylene sulfonate) provided a fountain solution which
ran with a water balance of 5 notches (90-95) and
catchup at 90 notches indicating the press could run.
The fountain solution, containing hydrotrope had a
dynamic surface tension of 32 dynes/cm., as measured
above.
Exam~le 3
In a fountain solution containing
2 oz./gallon of the fountain solution concentrate of
Example 1 and 5% by volume of the fountain solution of
isopropanol, the addition of 4 oz./gallon of an aqueous
solution containing by weight 8.3% 3,5-dimethyl-
l-hexyn-3-ol, 8.3% 2,4,7,9-tetramethyl-5-decyne-
4,7-diol, 17.5% sodium cumene sulfonate, 17.5% ammonium
xylene sulfonate and 48.4% water gave a wide water
balance of 65 notches to 85 notches with a dynamic
surface tension of 28 dynes/cm., as measured above.
Without the addition of hydrotropes the water balance
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was 80 to 90 notches with a dynamic surface tension of
31 dynes/cm., as measured above.
ExamPle 4
A solvent-free fountain solution was prepared
containing 2 1/2 oz./gallon of the fountain solution
concentrate of Example 1 and 4 oz./gallon of an aqueous
solution containing 38.6~ by weight ammonium xylene
sulfonate, 4.5% by weight 3,5-dimethyl-1-hexyn-3-ol and
3.5% by weight of 2,4,7,9-tetramethyl-5-decyne-4,7-diol
and 53.4% by weight water.
The water balance was 75-85 notches with
catchup at 70 on a Dahlgren dampening system. The
dynamic surface tension was 30.5 dynes/cm., as measured
above.
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Exam~le 5
A fountain solution concentrate was prepared
containing 90% by weight of sodium toluene sulfonate
(42% by weight aqueous solution) and 10% by weight
2,4,7,9-tetramethyl-5-decyne-4,7-diol. A fountain
solution containing 3 oz./gallon of the concentrate was
run on a Chambon Press using a Dahlgren type dampening
system. Inks of the various colors ~cyan, magenta,
yellow and black) all ran well on the lithographic
press. The dynamic surface tension of the fountain
solution was 31 dynes/cm as measured above.
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