Note: Descriptions are shown in the official language in which they were submitted.
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WATER-BASED OFFSET LITHOGRAPHIC NEWSPAPER PRINTING INK
This application is a Continuation-In-Part of
Application Serial No. 08/978,804, filed November 26,
1997, which is a Continuation-In-Part of Application
Serial No. 08/614,587, filed March 3, 1996, now U.S.
Patent No. 5,725,646.
Field of the Invention
The invention relates to water-based offset
lithographic newspaper printing ink.
Description of Related Art
In an attempt to eliminate volatile organic
compounds (VOCs) in the pressroom, water-ba~Pr~
alternatives are being sought for ink formulations.
Water-based printing inks for use in flexographic
printing processes are known in the prior art. This type
of printing process utilizes printing plates wherein the
printing images stand up in relief, i.e. the areas to be
printed are raised above the non-printing areas.
Printing by the flexographic process requires relatively
low pressure while sufficient pressure is applied to
transfer the ink from the face of the image carrier to
the surface of the substrate. Examples of useful water-
based flexographic printing inks are disclosed in U.S.
Patent No. 4,173,554 and The Printing Ink Manual, edited
by R.H. Leach and R.J. Pierce, pages 571-576, 5th
edition, (Blueprint, 1993).
Water-based inks for gravure printing are also well
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known. Tn the gravure process, the printing image is
engraved into a cylinder in the form of cells which
become filled with ink. Printing is achieved by passing
the substrate between the gravure cylinder and impression
roller under pressure. Examples of useful water-based
gravure printing inks are disclosed in U.S. Patent Nos.
4,954,556 and 5,098,478.
The offset lithographic printing process presents a
unique challenge to ink formulators since such process
utilizes a planographic printing plate, i.e. the image
and non-image areas are in the same plane on the image
carrier, and two fluids are concurrently utilized.
It is fairly simple to define an image area by
raising it above the background as in the case of the
flexographic printing plate or lowering it as in the case
of the gravure printing plate; avoidance of ink adhering
to the non-image area is not too difficult to achieve.
However, when all areas are on the same level, techniques
must be utilized to insure that ink adheres only to the
image area, and not to the non-image area.
In conventional offset lithographic printing
processes, the plate is damped before it is inked with an
oil-based ink. Typically, the damping process utilizes a
fountain solution such as those described in US patents
3,877,372, 4,278,467 and 4,854,969. Water will form a
film on the hydrophilic areas (i.e. the non-image areas)
of the printing plate, but will contract into tiny
droplets on the oleophilic areas (i.e. the image areas).
When an inked roller containing the oil-based ink is
passed over the damped plate, it will be unable to ink
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3
the areas covered by the water film (the non-image
areas), but will emulsify the droplets on the water-
repellant areas (the image areas) and these will ink up.
Such process is called offset lithography because the
inked image on the plate does not directly print onto the
paper substrate, but is first "offset" onto a rubber
blanket, and transferred therefrom onto the paper
substrate.
As mentioned above, conventional offset lithographic
I5 printing processes entails the use of oil-based inks and
water-based fountain solutions. The ink/water balance is
critical and is quite demanding of the pressman's skills.
This issue is one of the several disadvantages
associated with such printing processes as compared to
flexographic and gravure printing processes. Moreover,
the oil-based inks and aqueous fountain solutions
typically employed in conventional offset lithographic
printing processes contain fairly high levels of
undesirable volatile organic compounds ("VOCs").
U.S. Patent 3,356,030 discloses the use of a water-
based printing ink in respect to a method of planographic
printing utilizing a lithographic printing plate whose
non-image areas are coated with a cured coating of a
thermosetting silicone resin. However, the patented
method also entails the use of a volatile hydrocarbon
fountain solution which will coat the non-image areas and
which is re-applied between successive printings. Of
course, the use of a volatile hydrocarbon fountain
solution undermines the principal purpose of the water-
based ink compositions of the present invention, i.e. the
avoidance of the use of volatile organic compounds
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4
("VOCs") during the printing process. Indeed, the water-
based ink compositions of the present invention may be
used for offset lithographic printing processes without
any fountain solution whatsoever.
In the 1980s, a resurgence of interest occurred in
respect to "waterless" lithographic printing processes.
Both positive and negative waterless planographic
printing plates are commercially available from Toray
Industries of Japan. The image area of a waterless
planographic plate is a photopolymer similar to that
employed for the image area of a conventional plate.
However, the non-image area is coated with a polymer such
as a silicone which is ink repellant. Further
information about waterless printing plates and processes
may be found in U.S. Patents 5,370,906 and 5,417,749.
The waterless printing process solved two issues:
VOCs emanating from the fountain solutions and control of
the ink/water balance by the pressman. However, the
difference in surface energy between the image and non-
image areas of the conventional offset lithographic
printing plate is typically 40 dynes/cm is dramatically
reduced to 20 dynes/cm in the case of the waterless
printing plate. Therefore the latitude between scumming
and poor print density is considerably narrowed and the
issue of VOCs (emanating from the oil-based ink) still
remains in respect to waterless printing.
German Offenlegungsschrift DE 41 19 348 A1 pertains
to a moistureless offset printing method and a water-
based printing ink. The ink described therein is one
which will adhere to hydrophilic materials, but not to
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5 hydrophobic materials, and contains a dye, water, 5-50%
water-soluble macromolecular binder and a hygroscopic
liquid, preferably a multihydric alcahol.
It is an object of the present invention to
eliminate the principal disadvantages of conventional
offset lithographic printing inks, viz, high levels of
VOCs emanating from the oil-based ink and the aqueous
fountain solution and the difficulty in controlling the
ink/water balance, while preserving the principal
advantage of the conventional lithographic printing
process, i.e. high surface energy differential between
the image and non-image areas of the printing plate.
Such object has been achieved by means of the
present invention which comprises a water-based printing
ink that is to be used in offset lithographic newspaper
printing processes without the need for any accompanying
fountain solutions.
Summary of the Invention
The invention is a water-based single fluid fountain
solution free offset lithographic news ink comprising:
(a) water;(b) a macromolecular resin binder comprised
of: (i) resin soluble in water regardless of the pH of
the water,(ii) resin rosin salts soluble in water at a pH
ranging from about 7.5 to about 20, and (iii) aqueous
emulsions resins; (c) a soybean oil based resin; (d)
pigment; and (e)a hydroxyethylethylene urea rewetting
agent.
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Detailed Description of the Invention
The discovery of a highly compatible soya resin
system has enabled us to formulate a waterbased offset
lithographic ink for newspaper printing that has low and
stable tack and sustains runnability. Once printed on
the newspaper the ink has good rub resistance and a cost
comparable to conventional oil-based newspaper inks.
Currently, all lithographic offset newspaper
printing is done with inks which contain mineral oil or
soy bean oils. These inks are also used in conjunction
with a fountain solution which typically contains a
desensitizer, a salt, and glycol. In order to prevent the
evaporation of water from the printing rollers it was
desirable to have constant humidity. This provided
advantages over existing compositions, mainly zero
V.O.C., water washability, and fast drying. It has now
been found that the use of a certain soybean oil modified
resins enable us to eliminate the humidity control
requirement and use the existing multiple roller press
set-up to print.
The printing plates for use with the newspaper
printing ink of the present invention should be such that
the image areas thereof are hydrophilic in nature, while
the non-image areas are hydrophobic in nature. An
example of a suitable printing plate is the "waterless"
Toray type discussed above. However, the image area of
the plate need not contain a photopolymer. The image
area of the plate may comprise, e.g. a grained aluminum
surface which has no coating thereon, but is hydrophilic
in nature. The~non-image area of the plate must, of
course, be hydrophobic in nature. However, the non-image
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7
area may be covered with any type of hydrophobic
material, provided that such hydrophobic material adheres
to the non-images area of the plate during the printing
process.
Examples of suitable macromolecular binders which
are soluble in the water phase of the ink regardless of
the pH of the water phase include: carboxymetnyl-
cellulose, hydroxyethylcellulose, hydroxypropyl-
cellulose, hydroxybutylmethylcellulose, poly(C1-C4)
alkylene oxides, polyethyleneimine, polyvinyl alcohol,
polyvinyl acetate, polyvinylpyrollidone, polyvinyl-
oxazolidone and polyacrylamide polymers.
Preferably, the macromolecular resin rosin salt
binders present in the ink are only those resin rosin
salt binders which are soluble in the water at pH ranging
from about 7.5 to about 10. Suitable examples of such
resin rosin salt binders include methacrylic resins;
styrene-acrylic resins; rosin salts; and polystyrene-
sulfonic acid and their salts. Ammonia or an organic
amine such as monoethanolamine or N,N-diethanolamine may
be added to the water phase in order to adjust the pH to
the preferred value (a mineral acid or an organic acid
such as acetic acid may be used to adjust the pH to a
value in the range of about 2.5 to about 6.5).
Suitable examples of the macromolecular resin
binders comprising aqueous emulsions include acrylic or
vinyl emulsion polymers prepared from monomers selected
from the group consisting of acrylic acid esters,
methacrylic acid esters, acrylic acid esters of
polyhydric alcohols, methyl methacrylate, styrene, vinyl
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styrene and vinyl acetate.
The offset lithographic news ink formula in the
present invention employs a soybean oil based modified
resin. Examples of soybean oil based systems suitable
for use in the present invention are described in U.S.
Patent Nos. 5,167,704 and 4,419,132 which describe, inter
alia, non-petroleum soybased news inks. Resins
modifiable with soybean oils suitable for use in the
present invention include Fancol VB and Gilsonite.
The pigment may be any of those which are suitable
for formulating offset lithographic printing inks such as
CI Pigment Yellows 1, 3, 4, 5, 12, 13, 14, 17, 55, 65,
73, 83, 97 and 98; CI Pigment Oranges 13, 16 and 46; CI
Pigment Reds 2, 3, 4, 10, 12, 48, 48:1, 48:2, 53, 57:2,
81, 104, 146, 170 and 176; CI Pigment Greens 2, ? and 36;
CI Pigment Blues 1, 15:1, 15:2, 15:3, 15:6, 16, 29, 56
and 61; CI Pigment Violets 3, 23 and 37; CI Pigment
Blacks 6 and 7; and CI Pigment Whites 6, 7, 18 and 26.
The rewetting agent is hydroxyethylethylene urea.
In the water-based offset lithographic news ink of
the present invention the water is present in amounts of
25 to 60 wt.%; and more preferably 35 to 50 wt.%. It is
also preferred that the macromolecular resin binder be
present in amounts of 10 to 70 wt.%; and more preferably
30 to 60 wt.%; and most preferably the macromolecular
resin binder is a composite having up to 5 wt.% of a
resin binder soluble in water regardless of the pH of the
water; l0 to 70 wt.% of a resin binder soluble in water
at a pH ranging~from 7.5 to 10; and up to 20 wt.% of an
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aqueous emulsion resin binder. The pigment is preferably
present in amounts of 2 to 30 wt.% and the soybean oil
based modified resin is present in amounts of 15 to 35
wt%. Finally, the hydroxyethyl ethylene urea rewetting
agent is preferably present in amounts from 0.5 to 10
wt.~.
If desired, the usual adjuvants such as waxes, anti-
foam agents, biocides, surfactants, corrosion inhibitors,
etc. may be incorporated in the inks of the present
invention.
In a preferred embodiment of the water-based offset
lithographic printing ink of the present invention a non-
ionic surfactant is employed in the amount of up to 5
wt.~. Suitable examples of the surfactant include
acetylenic glycols, ethoxylated glycols and sorbitan
esters.
The water-based news ink of the present invention
are further illustrated by the following non-limiting
examples in which all parts and percentages are by
weight, unless otherwise indicated.
Examgle 1
A water-based news ink was prepared from the
components indicated below. The water phase of the ink
was supplied by the water present in the acrylic resin
latex, hydroxypropyl cellulose, hydroxyethyl ethylene
urea and the maleated rosin ester.
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Amount
Component wt,%
10 ethylene glycol modified maleated rosin resin 3-10
Pigment Red 57:2 12-20
water 25-35
soybean oil modified resin (Fancol VB)~a~ 20-28
lanolin based surfactant .5-2
hydroxyethylethylene urea 10-25
mineral clay (Laponite RD)~b~ .6-1
Total 100.00
(a) Fancol~ is a trademark of Fanning Corp.
2 0 (b) Laponite~ is a trademark of Southern Clay Products Co.
Example 2
A water-based newspaper printing ink was prepared
according to the following formulation:
Amount
Component wt.%
ethylene gylcol modified maleated rosin resin 3-10
hydroxyethylethleneurea (Sartomer SR-511)~a~ 10-25
mineral clay (Laponite RD)~b~ 0.6-1.0
soybean oil modified resin (Fancol VB)~°? 20-28
lanolin based surfactant 0.5-2
water 25-35
Pigment Red 57:2 12-10
Total 100.00
(a) SR-511 is a trademark of the Sartomer Corp.
(b) Laponite~ is a~trademark of Southern Clay Products.
(c) Fancol~ is a trademark of Fanning Corp.
*rB
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Example 3
A water-based newspaper printing ink was prepared in
accordance with Example 2. The ink was run on a Didde
printing press. The printing plate, obtained from Toray
industries, had an aluminum oxide substrate coated with a
photopolymer whose surface was hydrophilic in nature,
while the non-image area was coated with a silicone
polymer. The press run was carried out at temperatures
ranging from 15-20°C at a press speed of 1,000 feet per
minute (fpm). The print samples obtained from the press
run were clear and sharp with stable tack and were fast
drying. There was no discernible toning in the non-image
area nor observable ink buildup on the rollers, plate or
blanket. The results gave excellent print quality.
Example 4
A black water-based newspaper printing ink was
prepared having the following formulation:
Amount
Component wt.%
ethylene glycol modified maleated rosin resin 8.00
monoethanol amine 2.96
ethoxylated nonionic surfactant(Surfynol 420)~a~ 0.96
carbon black pigment (Regal 400R)~b~ 19.16
water 22.54
hydroxyethylethlene urea (Sartomer SR-511)°~ 11.17
CaC03 4 . 99
soybean oil modified resin (polyester) 26.82
synthetic hectorite mineral resembling clay 1.40
(Laponite RD) ~d~
non-ionic primary water/oil emulsifier
(Fancol VB)~e~ 2.00
Total 100.00
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_______________________________________________________
(a) Surfonyl~ 20 is a trademark of the S.C. Johnson Corp.
(b) Regal~ 400 R is a trademark of Cabot Corp.
(c) SR-511 is a trademark of the Sartomer Corp.
(d) Laponite~ RD is a trademark of Southern Clay Products Co.
1 0 (e) Fancol~ VB is a trademark of Fanning Corp.
The inks were run on a T70 lithographic press manufac-
tured by Goss Graphics at a speed of 50k iph. The
printability and runnability of the inks were very good.
Example 5
A low tack version of the ink prepared in Example 4
was prepared using the following formulation:
Amount
Component wt . ~
carbon black pigment (Regal 400R)~a~ 15.0
nonionic primary water/oil emulsifier g,5
2 5 ( Fancol VB ) ~b~
soybean oil modified resin (polyester) 39.0
monoethanol amine 2.0
hydroxyethylethlene urea (Sartomer SR-511)~~~ 12.6
water 21.7
synthetic hectorite mineral resembling clay
(Laponite RD)~d~ 1.2
Total 100.00
(a) Regal~ 400 R is a trademark of Cabot Corp.
3 5 (b) Fancol~ VB is a trademark of Fanning Corp.
(c) SR-511 is a trademark of the Sartomer Corp.
(d) Laponite~ RD is a trademark of Southern Clay Products Co.
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The ink was run on an offset lithographic printing press
manufactured by Koenig & Bauer of Germany with no
problems. The print samples had a high print quality.
The present invention has been described in detail,
including the preferred embodiments thereof. However, it
will be appreciated that those skilled in the art, upon
consideration of the present disclosure, may make
modifications and/or improvements on the invention that
fall within the scope, and spirit of this invention as set
forth in the following claims.
'B
