Note: Descriptions are shown in the official language in which they were submitted.
.
FOUNTAIN SOLUTION FOR OFFSET PRINTING
Back~round of the Invention
The present invention relates to a fountain
solution and a fountain solution concentrate for use
in offset printing.
In offset printing, plates and foils of
metal, usually of aluminum, or of paper or
; synthetics, which have a hydrophilic surface in the
non-printing areas and an oleophilic layer in the
image areas or printing areas, are clamped to a
printing cylinder. The hydrophilic and oleophilic
areas are located in one plane, in a process known
as planographic printing. For printing, in addition
to the ink, which is oil-based, a so-salled fountain
solution is required which maintains the image-free
areas hydrophilic, so that the ink is accepted only
by the oleophilic image areas and transferred via
the rubber blanket to the paper.
In the simplest case, water or dilute acid
can ~e used as the fountain solution. In this case,
however, it is difficult to maintain the ink/water
--1--
2 0 ~1~16
balance. Difficulties arise on printing, for
exampler by ink being transferred to the non-image
areas, a phenomenon known as scumming, or by the
paper being over-moistened, which results in
- 5 consequential damage such as press stops, poor
drying and waviness of the printing paper.
To improve printing~ substances are usually
added to the fountain solution which are intended,
for example, to optimizP the pH and the
compatibility with the printing ink and to
counteract interference which can be caused by the
regionally differing water, the paper or by
microorganisms.
In addition to buffer mixtures which are
intended to regulate the pH, additives for keeping
the printing plate moist are especially used. In
addition, che~ate formers, organic solvents,
preservatives, occasionally surfactants, corrosion
inhibitors and antifoams are used.
Nowadays, isopropanol in a concentration from
8 to 20% by volume is widely added to tha fountain
solution. This addition e:Efects a lowering of the
surface tension and a reduction in water transfer.
The results are a more brilli~nt printed image and
less thorough moistening of the printed paper. The
advantages of the use of isopropanol are to be
compared with the followiny disadvantages:
- ready evaporation and ignitability of
the isopropanol used for dilution,
- pollution of the breathing air, and
- high costs caused by the large quantity
required in use.
--2--
Attempts have therefore been made to replace
isopropanol.
In US 3,877,372, the use of a solution of
butylglycol, hexylene glycol and ethylene glycol in
conjunction with a silicone/glycol copolymer and an
antifoam is described. However, butylglycol is not
toxicologically safe.
US 4,234,443 discloses a powder which is to
be used in aqueous solution as a fountain solution.
It is prepared from phosphate, metasilicate,
tetrapotassium pyrophosphate and dialkylpoly-
siloxane, as well as reaction products of
alkylphenol or aliphatic alcohols with ethyl~ne
oxide in a molar ratio of l:9 to 1:50. However, the
aqueous solution of this powder shows an alkaline
reaction, a property which can adversely affect the
positive printing plate layers which are alkali
soluble under the action of light. A fountain
solution working in the alkaline pH range requires
more isopropanol or an appropriate su~stitute, in
order to maintain the water absorption within a
range favorable for printing (Braun, American Ink
Maker, 1985, Fig. 16). A further disadvantage of
the powder described is that reaction products of
alkylphenol with ethylene oxide are not adequately
biodegradable.
EP 336,673 describes a fountain solution for
offset printing which, in addition to other surface-
active agents such as anionic or nonionic agents,
contains 0.1 to 5% by weight of a monohydric alcohol
or diol of alkanes or alkenes, to which 1 to 10 mol
of ethylene oxide and/or propylene oxide per mol have
2 ~ 4 ~
- been added. A preferred embodiment of this fountain
solution comprises not less than 1% by weight of the
surface-active agent. The disadvantage of this
fountain solution is that the surface-active agent
in the disclosed quantity cannot be incorporated
into a concentrate. Solutions more concentrated
than the ready-to-use solution exhibit undesirable
effects, such as insolubility of the surfactant
due to the very high concentration thereof that
would be present in a fountain solution concen-
trate~ Therefore, either a relatively expensive
two-stage preparation method must be applied by
the user, or ready-to-use solutions, i.e., solu-
tions which have already been diluted to the end
concentration, must be marketed, and this means
transporting a hundred times the quantity.
Summary of the Invention
It is therefore an object of the present
invention to provide a fo-mtain solution which is
marketed as a liquid concentrate and is diluted
merely by addition of water to give a ready-to-use
fountain solution, which does not require
isopropanol as a further aclditive, and in which the
application values with respect to surface tension
and water consumption are not inferior as compared
with the state of the art.
These and other objects according to the
invention are provided by a fountain solution for
offset printing comprising water containing about
0.001 to 0.08% by weight of at least one polyether
surfactant selected from the group consisting of
ethoxylated and propoxylated alkanols, alkenols,
2 ~
alkanediols and alkenediols having 5 to 15 carbon
atoms, the polyether surfactant having 3 to 12 units
selected from the group consistlng of ethylene oxide
units and propylene oxide units. A fountain
solution concentrate is also provided, which can be
diluted with water to produce a ready-to-use
fountain solution. It comprises water containing
the polyether surfactant in a concentration that is
30 to lOO times, preferably 40 to 70 times, the
concentration of a ready-to-use fountain solution.
A method of preparing a fountain solution is
also provided according to the invention, which
comprises the steps of providing a fountain solution
concentrate; and diluting the fountain solution
concentrate with an amount of water that is 30 to
100 times, preferably 40 to 70 times, the amount of
water contained in the concentrate.
Other objects, features and advantages of the
present invention will become apparent from the
following detailed description. It should be
understood, however, that the detailed description
and the specific examp:Les, while indicating
preferred embodiments of the invention, are given by
way of illustration only, since various changes and
modifications within the spirit and scope of the
invention will become apparent to those skilled in
the art from this detailed description.
Detailed Description of the Preferred Embodiments
According to the present invention, a ready-
39 to-use fountain solution comprises about 0.001 to
2~51~
0.08~ by weight, preferably about 0.003 to 0.05% by
weight, of at least one alkanol or alkenol or of an
alkanediol or alkenediol having 5 to 15 carbon
atoms, which has been converted into a polyether
structure having 3 to 12, especially 6 to 8,
ethylene oxide units and/or propylene oxide units.
The surfactant has the advantage that, even
in th~ low concentration according to the invention,
it causes a surface tension of about 30 to 45 mN/m
in the fountain solution, which is achievable only
at a concentration of 3 to 20% by weight when
isopropanol is used.
It is completely surprising that the fountain
solution according to the invention, as compared
with fountain solutions according to EP 336,673,
shows comparable values with regard to the surface
tension, in spite of the lower concentration of the
surfactant, and at the same time displays
substantially better ~alues in water absorption and
better behavior on the printing press in the scum
cycle test. The lower concentration of the ready-
to-use solution means that the fountain solution can
be marketed and transported in a concentrated form,
and then diluted by the user.
Both straight-chain and branched alkanols and
alkenols or alkanediols and alkenediols can be used.
Preferred compounds include n-pentanol, 2-
methylbutanol, 1-penten-3-olj 1-hexanol, 3-hexanol,
4-methyl-2-pentanol, 2-ethylbutanol, 5-hexen-1-ol,
1-heptanol, heptenol, n-octanol, 1-octen-3-ol, 2-
ethylhexanol, nonanol, 2,6-dimethyl-4-heptanol, n-
decanol, decenol, sec.-undecanol, substituted and
2 ~ 6
unsubstltuted cyclohexanol, 1,5-pentanediol, 2,4-
pentanediol, 2,5-hexanediol, 1,6-hexanediol, 1,7-
heptanediol, 2,4-heptanediol, 2-methyl-2,4-
pentanediol,2-ethyl-1,3-hexanediol,1,8-octanediol,
1,9-nonanediol, 1,10-decanediol, cyclopentane-1,2-
diol, cyclohexane-1,2~diol, dodecanol and dodecenol.
Alkanols and alkanediols are particularly preferred
and, among these, alkanols having 10 to 15 carbon
atoms are especially preferred.
The surfactants according to the invention
contain polyether structures having 3 to 12 ethylene
oxide units and/or propylene oxide units. These
surfactants are prepared by adding 3 to 12 and
especially 6 to 8 mol units of ethylene oxide and/or
propylene oxide per mol of alcohol. When both
ethylene oxide and propylene oxide are to be reacted
with the alcohol, they are preferably employed in an
equimolar ratio. In this case, the mole fraction of
the individual components is 3 to 6 mol.
; 20 It is also possible to use mixtures of two or
more surfactants in the fountain solution according
i to the invention. In some cases, it is advantageous
additionally to use cationic surfactants.
Furthermore, the fountain solution according to the
invention can contain small quantities of solvents
of low volatility having a boiling point above about
100C and a flash point above about 21C, which
favorably affect the water absorption in the ink,
for example, methylpyrrolidone, glycol ethers,
alcohols or lactones.
As protective film-formers and viscosity
control agents, the fountain solution can contain
2 ~ 6
conventional water-soluble polymers such as
polyglycols, polyacrylic compounds such as
polyacrylamides, polyacrylic acid and copolymers
thereof, polyvinyl alcohols and derivatives ther~of,
polyvinylpyrrolidone, gum arabic, starch, dextrine
and cellulose ethers. In the ready-to-use fountain
solution, the water-soluble polymers are present in
concentrations from about 0.001 to 5% ~y weight,
preferably about 0.005 to 1% by weight.
To adjust the pH range in the fountain
solution according to the invention to ~ to 6,
especially to about 5, organic acids and/or salts
thereof and other usual buffer mixtures are used.
Citric acid, acetic acid, sxalic acid, malonic acid,
p-toluenesulfonic acid, tartaric acid, maleic acid
and the like may be mentioned as organic acids. If
th~ acids are used as such, the desired pH is
ad~usted to the range indicated above by an addition
of al~ali, especially NaOH, or by addition of
phosphates, especially trisodium phosphate.
The fountain solution according to the
inventi~n can also contain humectants, which form a
moisture film on the plate and thus ensure rapid re-
moistening after a press stop. These include, in
particular, glycerol, sugar alcohols, ethylene
glycol, propylene glycol, butylene glycol,
pentanediol, hexanediol, diethylene glycol,
triethylene glycol, tetraethylene glycol,
dipropylene glycol and/or tripropylene glycol. The
compounds can be present in the fountain solution in
a concentration of preferably up to about 1~ by
weight.
--8--
- 2~5~
Chelate formers can also be added to the
fountain solution. Organic amines are particularly
preferred. However, their presence in the fountain
solution is not essential to the invention.
Usually, the fountain solution can contain chelate
formers in concentrations from about 0.001 to 0.5%
by weight, preferably about 0.01 to 0.2% by weight.
Other conventional additives include
preservatives such as the biocides ~Mycostabil
(Druckservice Heliocolor), ~Piror P 840 (Gockel &
Co. G~bH, Munichj or ~FMl (made by Riedel de Haen,
Seelze) for prevention of the growth of fungi,
bacteria and algae. Dyes and antifoams can also be
added.
To obtain a ready-to-use fountain solution,
the constituents in the indicated quantities are
made up with water to 100% by weight. The total
hardness of the water can hexe range from 1 to 40,
and especially from 8 to 25 German hardness. The
carbonate hardness of the added water is especially
3 to 20 German hardness.
- The fountain solution concentrate contains
the particular constituents in concentrations which
correspond to about 30 to 100 times and preferably
about 40 to 70 times the values indicated in the
present description. This concentrate is then
diluted by the user with water of the quality
indicated above to give the ready-to~use fountain
solution.
The examples which follow are intended to
explain the invention in more detail, with~ut having
a restricting effect. In these examples, the g:cm3
_g_
2 ~
ratio is the same as that of parts by weight
(p.b.w.) to parts by volume (p.b.v.).
In the examples, the particular fountain
solution is tested by reference to several measured
parameters: The surface t_nsion (detachment method)
provides information on the extent of the effect of
the surfactant.
The water consumption on the printing press
also provides information on the property of the
surfactant. With optimum effectiveness, the least
possible water is transferred to the paper, and
consequently the consumption is reduced.
The scum cycle test provides information on
the cleaning action of the fountain solution. In
this test, the water supplied during printing is
turned off and printing is continued until the plate
has been blocked with ink. Water is then added
again and the number of sheets is determined, after
which the print is again perfectly clean. This is
a relative comparison.
The water absorption test is carried out in
accordance with "Surland, TAGA PROCEEDINGS, 1983"
and provides numerical information on the printing
behavior. The data are reliable only if the same
ink is used. In the present examples, the LITHO-
SET-SE blacX ink No. 50-940100-6 from Sieqwerk is
used. This again is a relative comparison. If
other inks are used, all the values can be lower or
higher.
~` -10-
2 ~
Example 1
An electrolytically grained and anodized
aluminum foil is coated with a solution of:
2.17 p.b.w. of 4~ dimethylbenzyl)-phenyl
- 5 1,2-naphthoquinone-diazide-4- sulfonate,
1.02 p.b.w. of the esterification product of 1
mol of 2,2'-dihydroxy-1,1'-
dinaphthylmethane and 2 mol of
1,2-naphthoquinone-diazide-5-
sulfochloride,
0.37 p.b.w. of 1,2-naphthoquinone-diazide-4-
sulfochloride,
0.10 p.b.w. of crystal violet and
s.so p.b.w. of a cresol/formaldehyde novolak
having a softening range from 112
to 118C in
43 p.~.v. of tetrahydrofuran,
p.b.v. of ethylene glycol monomethyl
ether, and
9 p.b.v. of butyl acetate
; and dried. The light-sensitive material obtained is
exposed under a photographic, positive original
which, inter alia, contains a 21-step step wedge
with density increments of 0.15. The exposure time
is selected such that step 9 is fully covered. The
plate is developed with a 5% aqueous sodium
metasilicate solution, rinsed well, fixed with acid
and used for printing in a Heidelberger GTO-VP
--11--
2 ~
printing press with an alcohol fountain unit. The
printing ink used is K+E black 185 W (BASF).
The fountain solution used is a mixture of
0.004 p.b.w. of ethoxylated decyl alcohol
having 7 ethylene oxide units,
0.002 p.b.w. of an ethoxylated and propoxylated
C~0/C~2-alcohol (4 ethoxy units and
4 propoxy units),
0.002 p.b.w. of dialkyldimethylammonium
chloride (alkyl <10 carbon atoms),
0.~6 p.b.w. of citrlc acid,
0.2 p.b.w. of dipropylene glycol,
0.06 p.b.w. of N-methylpyrrolidone,
0.06 p.b.w. of preservative, and
15sufficient NaOH to adjust the pH to 5.0 and
sufficient water of a total hardness of 17
. German hardness and a carbonate
hardness of 11 German hardness to
make up the fountain solution to
100 parts by weight.
The surface tension is determined to be 36
mN/m, the water consumption is determined to be 69%
(Comparison Example 14) as compared with a
: conventional fountain solution with 20% added
isopropanol as 100%, the sheet number up to clean
running (scum cycle test) is determined to be 120
sheets and the water absorption is determined to be
38%.
-12-
2 ~
Exam~les 2 to 9
The following fountain solutions are used for
printing from a printing plate made up according to
Example 1. The fountain solution compositions and
results are compiled in Table 1.
-13-
Table 1
. . . _ _ _ ~ . _
l Elumpb No. rD u in 2 3 4 5 6 7 8 9
.: prubr~ hl) __ _
l Flh~yl-led dr~rl
~hohol (7 EOI 0.0040.002 _ 0.008 _ 0.0015 0.037
Elh~rblod dr~cyl
Irchol (2 EO) . 0.004 .0 004 . 0.004 .
_ _
Elh~rbled nd
Pr~rl-lod C~JCI~.
0 1 ~Ircbol (4 EO ~4PO) o.r~o2 . o.r~o3 . . . 0.008 0.013
_ _ _
Dbl}yl~noni~m
chlorido ~CclO)0.002 _ . 0.008 0.013
Ciuic ~cid 0.160.16 0.016 0.16 OH 6 O. l o 0.16 0.16
Diproprbnr. ;~rcol 0.1 0.2 0.2 0.2 0.l 0.
N-Melbrlprnolid~ 0.06 0.06 0.06 _ _-
~djwlod wilb N~Oil or
l ~iium phl phle lo
i pH: 4.9 5.0 5.3 5.2 4.95.3 5.1 5.1
~ .. ~ _
¦ M.(b up ~o 100 p rb br
2 0 1 ~oi~h wilh ~or Or
i Ir~ rr~ or 17-
Cermlm h-ldnc-~ ~d
c rbrn lc hrdro o8
I l - (icnr~u !I-rdre r _ __ _ __ _
2 5 1 su~r.O~ ~ion
(d~4~r~ melhod)
mNlm 38 32 33 30 45 32 45 30
W~le~ ~ump ior. oo
3 I ~ p u~ pn~
I r~od wllh
I Cempnri~co Er mpb 14
(~ 1001~ 71 ~ 71 ~ ' . 90%83 i _'
I
Scum rycb lul: cb a
¦ runr~ng ~hor rrurnbor Or
3 5 I '~`' . , ,o _ ,oo _ 107 _ 120 _
¦ W~lor ~b~ion
(fb~cnrmed wilh bbc~
oibcl pTinlmg r~ m~b
I br Sb~crl~ No. 50
4 0 1 940100-6)36~: 39~ 37!~ 43% 38% 3~3~ 3S9~ 4
. _ _ . _ _ _ _ = _ _ _
- 2~51~
Example lo
The procedure followed is as in Example 1.
The fountain solution used is a solution prepared
` from:
0.02 p.b.w. of ethoxylated decyl alcohol,
0.16 p.b.w. of citric acid,
0.06 p.b.w. of Piror P 840,
0.3 p.b.w. of dipropylene glycol,
0.06 p.b.w. of N-methylpyrrolidone, and
0.02 p.b.w. of poLyglycol 600
by dissolution in deionized water, so that 100 parts
by weight result after adjustment of the pH to 5.
The solution has a surface tension of 39.5
mN/m. Perfect prints are obtained in the printing
press. As compared with Comparison Example 14, the
water consumption is reduced. The water absorption
of the LITHO-SET-SE black printing ink no. 50 940
100-6 is reduced to 33% as compared with Comparison
;` Example 13, a represenl:ative of isopropanol-
- 20 containing fountain solutions, whereby a brilliant
print with well-covered fu:Ll tones is produced.
Comparison Example 11
The procedure followed is as in Example 1,
with the exception that a surfactant is omitted. A
value of 65 mN/m is determined for the surface
tension. The water consumption on the printing
press as compared with Example 14 is 100%, i.e., the
-15-
2 ~ ?7 16
water consumption cannot be reduced with a fountain
`~ solution without surfactant. The scum cycle test
gives a sheet number of 150, after which perfect
prints can again be obtained. The water absorption
is greater than 45%. This clearly demonstrates the
improvement due to the surfactants according to the
invention.
Comparison Example 12
The procedure followed is the same as in
Example 1, but with the proviso that, in place of
0.004 part by weight of the ethoxylated decyl
alcohol (7 E0) used therein, l.0 part by weight is
employed in accordance with EP 336,673.
As a result, a surface tension of 27 mN/m is
ob~ained, a value which is not significantly lower
than that in Example 1, in which a surfactant
quantity smaller by powers of 10 is employed. The
water consumption was not determined, since the
image was still not clean after lO0 prints; there
was very pronounced scumming, i.e., no useful print
was obtained. The same phenomenon is found in the
scum cycle test; scumming is still present even
after consumption of more than 150 sheets.
comparison Example 13
In this example, the fountain solution used
is a mixture of 10 parts by weight of isopropanol,
0.16 part by weight of citric acid and 0.02 part by
weight of polyglycol 600. The solution is made up
-16-
2 ~
.
to 100 parts by weight with water of a total
hardness of 17 German hardness and a carbonate
hardness of 11~ German hardness and adjusted with
- NaOH to pH 5Ø
This solution has a surface tension of 36.5
mN/m. The LITHO~SET-SE black printing ink made by
Siegwerk absorbs 37% of this fountain solution. The
fountain solution according to the invention has
properties comparable with those of isopropanol but,
in addition, also has the advantages described.
Comparison Example 14
In this example, the fountain solution used
is a mixture of 20 parts by weight of isopropanol,
0.16 part by weight of citric acid and 0.15 part by
weight of glycerol. The solution is made up to 100
parts by weight with water of a total hardness of
30O German hardness and a carbonate hardness of 14
German hardness and adjusted with NaOH to pH 5Ø
This fountain solution serves as a reference
example with isopropanol for the printing tests on
the Heidelberger GTO-VP. The water consumption is
set equal to 100~. The number of sheets up to clean
running is 100. With respect to the water
consumption, this example shows disadvantages as
compared with those according to the invention.
-17-
