Note: Descriptions are shown in the official language in which they were submitted.
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PAT 84 040
07.08.1984
BASF Farben + Fasern Aktiengesellschaft, Hamburg
Rapidly absorbed printing inks and their use
The invention relates to printing inks ~hich con-
tain, as the binder, phenolic resin-modified rosin in a
proportion of 60 to 90% by weight and an alkyd resin in a
proportion of 10 to 40X by weight, the sum of phenolic
resin-moaifie~ rosin and alkyd resin giving 100% by weight.
The alkyd resin has been prepared from
a) an unsaturated fat~y acid having 6 to 20 carbon atoms
or a mixture of such acids or their triglycerides,
b~ a polyol and
c) a dScarboxylic acid.
The printing inks also contain pigments, if appro-
priate further binders and further conventional constitu-
ents, such as lubricants, soLvents, thickeners and thixo-
~ropic agen~s.
German Patent Specification 3,023,118 has disclosedpaper printing inks of this type for graphical purposes.
These consis~ of pigments, an alkyd resin binder which has
been modified by long-chain fatty acids having an iodine
number of less than 20 (determined according to DIN 53,241)
and which has an acid number of preferably 6 to lZ and an
hydroxyl number of preferably greater than 15 (determinea
according to DXN 53,241), in particular from 20 to 35, and,
if appropriate, further conventional constituents, such
Z5 as lubricants, solvents and a viscosity control agent.
Depending on the field of application, printin~
inks must meet a large number of requirements. For example,
printing inks should have a high abrasion resistance and,
in many cases, good re-release properties. As far as pos-
sible, they should also be free from yellowing, have aneutral odor and be fast-drying. To prepare the printing
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ink, the various resins are first dissolved at an elevated
temperature in mineral oil, and the pigments are then in-
troduced. Subsequently, the printing inks of the compo-
sition described above cure by oxidation
When the printing inks described in German Patent
Specification 3,023,118 and aLso other printing inks are
used for the sheet-fed offset and the letterpress process
the problem of setting off arises, i.eO printing inks which
are well compatible ~ith mineraL oil reLease the ~atter
only slo~-y, and consequently the prints remain ~et and
therefore require Powdering~ The Powder serves as a
spacer for the wet prints in the pile and also allows
better access of oxygen for the oxidative drying. How-
ever, po~dering has an adverse effect on the quality of
the prints and the further processing steps.
The disadvantages of powdering comprise poor abra-
sion resistance of the prints, complications in downstream
processes, such as varnishing and cellophaning, and con-
tamination of the machine.
A review of the disadvantages of powdering in off-
set printing is given by W. Walenski in "Der Polygraph",
volwme 5, 1984, pages 435-36. This review demonstrates
the urgency of the demand for a rapidly absorbed printing
ink.
The object of the invention is therefore to avoid
these disadvantages of the state of the art and to provide
a printing ink which is rapidly absorbed and therefore
does not require powdering.
Surprisingly, it has been found that this o~ject is
achieved by a printing ink which~ as the binder, contains
an alkyd resin having a high hydroxyl number, a lo~ acia
number and a high iodine num~er of the fatty acids, in com-
bination with a phenol resin-modified rosin. The inven-
tion therefore relates to a printing ink of the type des-
cribed at the outset, wherein the unsaturated fatty acidshave an iod;ne number of 120 to Z80 (9 of I2/100 9), pre-
ferably 120 - 200 (9 of I2/100 9), particularly preferably
120 - 190 (9 of Iz/100 9), and the alkyd resin has an
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acid number of less than 11 and a hydroxyl number of 40 to
2~0 (mg of KOH/g of resin).
In contrast to German Patent Specification 3,023,118,
a type of ~ast-drying oils or fatty acids, ~hich are dis-
tinguished by a hi~h iodine number, are used for modifyingthe alkyd resin. The oxidative drying via the double bonds
of the highly unsaturated fatty acids or oils is respon-
sible for the chemical drying of the printing ink. Good
chemical drying is supplemented by physical drying of the
printing ink, which car, be determined by the absorption
properties. Good physical drying is obtained by the print-
ing ink according to the invention. The alkyd resins used
as the binders have hydroxyl numbers which are in the range
from 40 ~o 260. These hydroxyl numbers~ which are high in
comparison with German Patent Specification 3,023,118, cause
an increased polarity of the alkyd resin binders. These po~ar
alkyd resins have only a limited solubility in mineral oils,
which has the resuLt ~hat printing inks containing polar
alkyd resins and mineral oil show good a~sorption. Hydroxyl
numbers of at least 40 are necessary in order to obtain the
polarity required for rapid absorption; the OH number range
from 11û to 180 can be indicated as par~icular~y advantageous
for the absorption properties. If an a~kyd resin OH number of
260 is exceeded, the poLar alkyd resin is then hardly solub~e
in the mineral oil which is the conventional solvent for
printing inks.
Refined linseed oil, soya oil or dehydrated castor oil
and the fatty acids obtained from these have proved suitable
as the unsaturated fatty acids or oils. Trimethy~o~propane,
glycerol and/or pentaerythritol are particularly suitable as
the po~yol components. The pre~erred dicarboxy~ic acids are
phthalic acid, isophtha~ic acid, adipic acid or te~rahydro-
phthalic acid, their anhydrides being employed in practice,
uhere these exist.
The invention a-so relates to a process ~or pre-
paring a printing in~.
A ~atty acid-modified alkyd resin is first prepared
from
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a~ an unsaturated fatty acid having 6 to 20 carbon atoms
or a mixture of such acids or their triglycerides,
b) a polyol and
c) a dicarboxlyic acid.
S This resin is combined with phenolic resin-modified rosin
and a mineral oil to give a binder mixture, the proportion
of alkyd resin being 10 to 40% by weight and that of the
modified rosin being 60 to 90% by weight, based on the
total weight of alkyd resin and rosin. This binder mix-
ture is dispersed, together with pigments, if appropriatefurther bin~ers and further conventional constituents,
such as lubricants, thickeners and thixotropic agents, by
means of a dispersing device, for example a three-roll mill,
a sand nill or a ba~l mill. The distinctive feature here
is that the unsaturated fatty acids have an iodine number
from 120 to ~80 ~9 of I2/100 9), preferably 120 to 200 (9
of I2/100 g), particularly preferably 120 to 190 (9 of
I2/100 9), and the alkyd resins have a hydroxyl number
from 40 to 26Q and an acid number of less than ~1. Refined
linseed oil, soya oil or dehydrated castor oil or the fatty
acids obtained from these can advantageously be used for
modifying the alkyd resins. Suitable polyol components are
trimethyLoLpropane, glycerol and/or pentaerythritol, an~
phthalic acid, isophthalic acic~, adipic acid or
tetrahydrophthalic acid or their anhydrides, ~here these
exist, can be used as the dicarboxylic acid component~
Surprisingly, the printing ink according to the in-
vention is also suitable for use in the letterpress process.
The printing inks according to the invention can be
used for ~he sheet-fed offset printing process, in which
the print is set do~n first on a rubber blanket and from
the lat~er to the paper or another printing substrate.
In the sheet-fed offset printing process, cut sheets are
printed.
Since the printing inks according to the invention
also show good physical drying, in addition to the oxidative
drying, in other words are rapidly absorbed, the otherwise
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required powdering can be omitted. This is a great
advaneage, since the powder adversely affects the quality of
the prints and makes the further processing steps more
difficult.
S With respect to the printing inks according to the
invention~ the com~ination of good chemical and physical
drying as the result of suitable iodine numbers and hydr-
oxyl numbers can be regarded as novel and advantageous.
Measurements of the absorption properties show that
the printing inks according to the invention are absorbed
more rapidly than the printing inks described in German
Patent Specification 3,023,118.
The invention is describe~ in more detail ~elow by
reference to illustrative examples~
EXAMPLE 1
1,508 par~s by weight of linseed oil fatty acid,
523 parts hy weight of pentaerythritol and 479 parts by
weight of isophthalic acid are heated to 250C in a reac-
tor under a slow stream of blanketing gas. This temperature
ZO is maintained until the hot mixture is clear. The tempera-
ture is then aLlowed to drop to 210C, and this tempera-
ture is maintained untiL an acid number of Less than 9 has
been reached and ~he viscosity is 60 - 70 dPa.s (80~. in
bu~yldiglycolj. The OH number of the resin is 111. The
resin obtained is dissolved in a mineral oil having a boil-
ing range from Z80 to 310C, such that a 70% solution
is formed.
Using this resin solution, a printing ink binder
of the following composition is preparea:
Phenolic resin-modified rosin 300 parts by weigh~
ALkyd resin, 7ûZ in mineral oil 250 parts by weight
Mineral oil, boiling range 280-310C 450 parts by weight
1000 parts by ~eight
The resins are dissolved in mineral oil at 220C~
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~ith stirring. A printing ink of the following composition
is prepared with this binder by means ot a three-roll mi~l:
Blue pigment15 parts by weight
Substrates (inorganic fillers, for
example CaC03~ Alz03)3 parts by weight
Wax 1 part by weight
Binder 72 parts by weight
Mineral oil7 parts by weight
Drier 2 parts by weight
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100 parts by weight
EXAMPLE 2
1,073 parts by weight of refined linseed oil are
heated to 200C in a reactor under a slow stream of
blanketing gas. 418 parts by weight of pentaerythritol
and 2 parts by weight of lithium stearate are then adaed
and the mixture is heated to 260C. Transesterification
takes place at this temperature. The mixture is then
cooled to 210C and S34 parts by weight of isophthalic
acid are added. The mixture is then reheated to 240C
and ~his temperature is maintained until the hot mi~ture
is clear. The temperature is then allowed to drop to
200C and maintained there, until an acid number of less
than 11 is reached and the viscosity is 300 - 400 dPa.s
(80X in butyldiglycol)~ The OH number of the resin is 181.
The resin obtained is dissolved in a mineral oil having a
boiling range from 280 to 310C, such that a oOX so~ution
is formed.
Using this resin solution, a printing ink binder
of the following composition is prepared:
Phenolic resin-modified rosin 300 parts by ~eight
Alkyd resin, 60% in mineral oil 250 parts by weight
Mineral oil, boiling ran0e 280-310C 450 parts by ~eight
1000 parts by weight
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The resins are disso~ved in the mineral oil at
Z20C~ with stirring. A printing ink of the fol~owing
composition is preparea with this ~inder by means of a
three-roll mi~
5 Blue pigment15 parts by weight
Substrates (inorganic fillers) 3 parts by weight
Wax 1 part by weight
~inder 70 parts by weight
Mineral oil9 parts by weight
10 Drier Z parts by weight
100 parts by weight
COMPARATIVE EXAMPLE
For comparison purposes, the printing ink according
to example 1 of German Patent Specification 3,023,118 is
prepared. The modified alkyd resin is prepared from 1~800 9
of coco nut oil, 569 9 of trimethylo~propane and 797 9 of
isophthalic acidO under the conditions indicated therein
with the addition of 0.1 9 of lead monoxide and 7 9 of p-
to~uo~enesulfonic acid as a crosslinking catalyst, anddiluted ~ith 600 9 of minera~ oil thoiling range 2S0 -
2$0C). As described in the exampLe, 10 9 of the aLkyd
resin are then pasted with 10 9 of a pigment, 2 9 of a poLy-
ethylene wax and 76 9 of a binder so~ution consisting of
32 9 of a phenolic resin-modified rosin resin in 44 9 of
mineral oil ~boiling range 270 - 310C).
The absorption properties of the prin~ing inks pre-
pared in examples 1 and Z is compared Wittl the absorption
properties of the printing ink from the comparative example
based on isophthalic acid, coco nut oi~ and trimethy~oL-
propane.
The absorption properties are measured by a densito-
metric determination, as a function of time, of the quan~ity
of ink which is transferred from the printed material to a
reverse-printing materia~. It is found here that, in the
case of the printing ink clescribed in the comparative
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example, the optical density on the re~erse-printing
material after 15 seconds is 8-10 times higher than the
op~ical density oDtained when measuring the printing inks
from examples 1 and 2. This means that the ~atter are
absorbed significantly more rapidly. The optical den-
sities are of comparab~e magnitwde only after abou~ 60
- seconds.
