Note: Descriptions are shown in the official language in which they were submitted.
._ L ' ~ '
2171407
~ --1--
ANIONIC POLYMER MIXTURES HAVING
REDUCED FOAM FORMATION IN WATER
Background of the Invention
Polymer mixtures containing acid groups which are
5 used as binders for coatings, especially also for water-
borne print coatings, are described many times in the
literature. Such polymer mixtures contain anionic
polymer resins which are prepared, for example, by
copolymerization of non-polar and acid-group-containing
10 monomers by bulk polymerization in continuously operating
plants (EP 0 068 024 and DE-A 32 25 876) or by batch
processes using solvents (EP-A 0 129 913).
A disadvantage of high-viscosity polymer resins which
are obtained via continuous processes is that residual
15 amounts of monomers, solvents or additives remaining in
the resin are unavoidable, because otherwise plugging or
channeling of the reactor occurs (G.E.H. Joosten, H.W.
Hoogstraten, C. Ouwerkerk; Ind. Eng. Chem. Process Des.
Dev. 1981, 20, 177). These residues adversely affecting
20 the product properties cannot generally be completely
.- removed afterwards or can only be removed afterwards by
means of greater technical resources, for example in a
plurality of degassing stages.
Solvent-free resin systems have also been developed,
25 for example by sequential emulsion polymerization of
carboxyl-group-containing monomer mixtures and non-polar
monomer mixtures (WO-A 91 049 90) or by bulk polymeriz-
ation of carboxyl-group-containing monomer mixtures with
a simultaneous "in situ" condensation reaction with mono-
30 hydroxyl compounds and subsequent emulsion polymerizationof non-polar monomers (EP-A 0 643 080).
A specific disadvantage of the resin systems which
have been prepared by the processes described emerges
when they are used as binders in print coatings, for
35 example in overprinting varnishes and printing inks.
Thus the printing industry requires that water-borne
systems be equivalent to or better than solvent-based
2171407
-2-
systems, particularly with respect to drying rate. A
central problem which occurs here with said resin systems
is an undesirable foam formation by the neutralized
macromolecules containing acid groups on printing, so
that they must be employed with the addition of consider-
able amounts of defoamer. This procedure is occasionally
successful, but on high-speed printing machines it is
usually not satisfactory, since a reduction in quality of
the printed image must frequently be accepted.
Summary of the Invention
It was therefore an object of the present invention
to develop polymer mixtures containing acid groups as
binders for printing inks which give no, or at least
lower, foam formation in printing in comparison to
synthetic resins known from the prior art.
It was also an object of the invention to provide
methods for preparing such mixtures and methods of using
them.
In accordance with these objectives, there has been
provided an anionic polymer composition having reduced
foam formation in water, containing (a) an acid-group-
containing polymer A, completely or partially
neutralized, prepared by polymerization of carboxyl-
group-containingethylenicallyunsaturated compounds with
other ethylenically unsaturated compounds in the presence
of one or more volatile basic neutralization reagents,
and optionally (b) a water-insoluble polymer B in the
form of latex particles which is prepared by emulsion
polymerization of ethylenically unsaturated compounds in
the presence of polymer A.
In accordance with the invention there is also
provided a process for the preparation of a polymer
composition as described above, which comprises (a)
preparing an acid-group-containing polymer A by
polymerizationofcarboxyl-group-containingethylenically
unsaturated compounds with other ethylenically unsatur-
ated compounds in the presence of volatile basic
2171407
-3-
neutralization reagents and optionally (b) preparing a
water-insoluble polymer B in the form of latex particles
by emulsion polymerization of ethylenically unsaturated
compounds in the presence of the neutralized or partially
neutralized polymers A.
In accordance with other aspects of the invention,
there have been provided coating compositions such as
printing inks or varnishs containing the above polymer
compositions and substrates coated with such
compositions.
Further objects, features, and advantages of the
present invention will become apparent from the detailed
description of preferred embodiments that follows.
. ~
Detailed DescriPtion of the Preferred Embodiments
It has now been found that polymer compositions which
contain a polymer A prepared by polymerization of
carboxyl-group-containing ethylenically unsaturated
compounds with other ethylenically unsaturated compounds
exhibit particularly low foam formation in the neutral-
ized state in water if the synthesis of the polymer A was
carried out in the presence of volatile basic neutraliz-
ation reagents.
The invention relates to anionic polymer compositions
having reduced foam formation in water, containing (a) an
acid-group-containingpolymer A, neutralizedorpartially
neutralized as appropriate, prepared by polymerization of
carboxyl-group-containing ethylenically unsaturated
compounds with other ethylenically unsaturated compounds
in the presence of volatile basic neutralization reagents
with or without "in situ" condensation with monohydroxyl
compounds, and, optionally (b) a water-insoluble
polymer B in the form of latex particles which may be
prepared by emulsion polymerization of ethylenically
unsaturated compounds in the presence of polymer A.
The invention further relates to a process for the
preparation of anionic polymer compositions having
2171407
.
4-
reduced foam formation in water, by (a) preparing an
acid-group-containing polymer A by polymerization of
carboxyl-group-containing ethylenically unsaturated
compounds with other ethylenically unsaturated compounds
in the presence of volatile basic neutralization
reagents, with or without "in situ" condensation with
monohydroxyl compounds, at least partially removing the
volatile basic reagents, and subsequently neutralizing or
partially neutralizing the polymer with further basic
lo reagents, as appropriate, and, if appropriate, (b)
preparing a water-insoluble polymer B in the form of
latex particles by emulsion polymerization of ethylenic-
ally unsaturated compounds in the presence of the poly-
mer A which is completely neutralized or partially
neutralized as appropriate.
The present invention also relates to the acid-group-
containing polymers A prepared by polymerization of
carboxyl-group-containing ethylenically unsaturated
compounds with other ethylenically unsaturated compounds
in the presence of volatile basic neutralization reagents
and, if appropriate, "in situ" condensation with mono-
hydroxyl compounds in the presence of basic neutraliz-
ation reagents, salts thereof, and solutions thereof in
water.
The novel polymers A can, in at least partially
neutralized state, be classified with the group of
polymer surfactants. In water they have an effective
absorption capacity for pigments and fillers. This
behavior, which is desirable for print coatings and other
specific properties, is determined by the molecular size
and by the molecular architecture, that is by the type,
amount and distribution of charged, polar and non-polar
portions.
In addition to the numerical ratios of the comonomer
units, the content and type of side chains, the acid
numbers, molar masses and molar mass distributions, glass
transition temperatures (T9) and, in particular, also the
reaction conditions in the synthesis are important for
2171407 `
5-
the properties of the polymers A according to the
invention.
The acid numbers (mass of KOH, in mg, required for
neutralizing 1 g of polymer) of the polymers A are
preferably in the range from 90 to 400 mg/g, in
particular 170 to 275 mg/g. The content of hydroxyl
compounds bound in ester groups is preferably between 0
and 25% in particular between 0 and 18~ by weight.
Preferably, a weight-average molar mass of 300 to 100,000
10g/mol, in particular 800 to 40,000 g/mol, particularly
preferably 1,000 to 25,000 g/mol, is obtained. The glass
transition temperatures of the polymers A are preferably
between 0 and 180 C, in particular 30 and 160 oc, and
particularly preferably 50 and 150 oc.
15According to the present invention, at least partial
neutralization of the acid-group-bearing monomers with
volatile basic compounds is necessary during the
polymerization to give the polymers A according to the
invention. The carboxyl-group-containing monomers are
stronger acids than the carboxyl-group-containing poly-
mers prepared therefrom, so that the monomers displace
the polymers from their salts. Therefore, during the
overall polymerization, a sufficient amount of neutral-
ized carboxylate-group-containing monomers is always
available for the polymerization. In this manner,
presumably, a polar-interaction-related local
accumulation of the polar monomers during the
macromolecule formation is prevented, so that the
monomers can be incorporated into the macromolecule
essentially randomly.
To introduce carboxylic acid groups into the polymer
of the type A, any monomer containing one or more acid
groups can be used. For example, any desired unsaturated
mono- or dicarboxylic acids or mixtures thereof can be
used. Unsaturated monocarboxylic acids which can be used
include acrylic acid, methacrylic acid and/or crotonic
acid, individually or in a mixture. These also include
monoesters of maleic and fumaric acid with saturated
alcohols which contain 1 to 10 carbon atoms. Unsaturated
21 71 407
~ -6-
dicarboxylic acids which may be mentioned include
dicarboxylic acids which contain 4 to 6 carbon atoms, for
example maleic acid, itaconic acid, mesaconic acid,
fumaric acid, methylenemalonic acid, citraconic acid,
salts thereof or, if appropriate ,anhydrides thereof.
The content of carboxyl-group-containing monomers is
preferably 5 to 70% by weight, in particular 15 to 55% by
weight, based on the total amount of the monomers in
polymer A.
Comonomers for the carboxylic acid-group-containing
monomers which are suitable to prepare polymer A are in
principle all ethylenically unsaturated compounds which
can be polymerized by a free radical mechanism. Use is
preferably made of hydrophobic monomers, for example
- 15 vinylaromatics or open-chain conjugated dienes. Those
which may be mentioned by way of example include styrene,
vinyltoluene, ~-methylstyrene, ethylstyrene, isopropyl-
styrene,tert-butylstyrene,2,4-dimethylstyrene,diethyl-
styrene, o-methyl-p-isopropylstyrene, halostyrenes such
as chlorostyrene, fluorostyrene and iodostyrene, 2,4-
cyanostyrene, hydroxystyrene, nitrostyrene, aminostyrene
and/or phenylstyrene. Preference is given in particular
to styrene, vinyltoluene and ~-methylstyrene.
Open-chain dienes to be mentioned include 1,3-
butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-
butadiene, pentadiene, 2-neopentyl-1,3-butadiene and
substituted 1,3-butadienes, such as 2-chloro-1,3-
butadienej 2-cyano-1,3-butadiene, substituted straight-
chain conjugated pentadienes, straight-chain and branched
conjugated hexadienes, other straight-chain or branched
conjugated dienes generally having 4 to 9 carbon atoms
and mixtures thereof.
The content of these comonomers is preferably 30 to
95% by weight, in particular 45 to 85% by weight, based
on the total amount of the monomers in polymer A.
To achieve specific properties in polymer A, further
starting monomers, for example esters of acrylic,
methacrylic and crotonic acid with saturated alcohols
which contain 1 to 12 carbon atoms in the alcohol radical
.
21 71 407
_ 7
; can also optionally be used individually or in a mixture.
Examples which may be mentioned include methyl
methacrylate, ethyl acrylate, butyl acrylate and 2-
ethylhexyl acrylate. The content of these comonomers is
preferably 0 to 10% by weight, in particular 0 to 5% by
weight, based on the total amount of the monomers in
polymer A.
other comonomers which can be used to prepare polymer
A include acrylamide, methacrylamide, 2-acrylamido-2-
methylpropanesulfonic acid, acrylamidosulfonic acid,vinyl acetate, vinylsulfonic acid, allylsulfonic acid,
vinylphosphonic acid, allylphosphonic acid, acrylo-
nitrile, methacrylonitrile, dimethylaminoethyl acrylate,
diethylaminoethyl acrylate, diethylaminoethyl meth-
acrylate, N-vinylpyrrolidone, N-vinylformamide, N-
vinylimidazole, N-vinylimidazoline, 1-vinyl-2-methyl-2-
imidazoline and/or mixtures thereof. Those monomers of
this group which contain acid groups can be used in the
copolymerization in the form of the free acid or in the
form partially or completely neutralized with alkali
metal bases or ammonium bases. The basic acrylates, for
example diethylaminoethyl acrylate, are generally
neutralized or quaternized with acid and then supplied to
the copolymerization. In addition, vinyl esters of ~
dialkylalkanemonocarboxylic acids, for example vinyl
esters of Versatic acid, and also vinyl acetate and vinyl
propionate can be used. These modifying monomers merely
serve to achieve specific properties and participate in
the structure of the copolymer A generally at 0 to 10% by
weight, preferably 0 to 4% by weight.
"In-situ" condensation refers to another embodiment
wherein monohydroxy compounds are added to the monomers
before, during or after the polymerization. Esterifica-
tion between these monohydroxy compounds and the acid
monomers thus occurs before, simultaneously with or,
preferably, after the polymerization. A catalyst
(usually an acid) may be added to accelerate the
reaction.
z - 21 71 407
-8-
The monohydroxy compounds include monoalcohols and
monoetherified polyalkylene oxide compounds. Monoalco-
hols are those having alkane or cycloalkane radicals,
preferably (C8-C32)-alcohols and isomers thereof, for
example 2-ethylhexanol, octanol, nonanol, decanol,
dodecanol and in addition stearyl alcohol, cetyl alcohol,
ceryl alcohol, myricyl alcohol, TCD~ alcohol M (Hoechst,
molar mass: 166 g/mol, OH number: 327 mg/g), wool wax
alcohols, cholesterols, borneols, isoborneols, or tall
oil fatty alcohols.
Optionally, to modify the properties, (C1-C6)-
alcohols having alkane and cycloalkane chains can also be
used in amounts of 0 to 35% by weight based on the amount
of monohydroxyl compounds, for example butanol, hexanol,
-; 15 cyclohexanol and/or mixtures thereof.
Useful monoetherified polyalkylene oxide compounds
include polyalkylene oxide compounds of the formula I
R1-(o-CHR2-CHR3)n-oH formula I.
In this formula, R1 is an alkyl, cycloalkyl or phenyl
radical, preferably an alkyl radical having 1 to 12, in
particular 1 to 4, carbon atoms, R2 and R3 are hydrogen
or alkyl radicals having 1 to 4 carbon atoms and n is 1
to 10, preferably 1 to 4. Examples of such compounds
which may be mentioned include methyl glycol, ethyl
glycol, butyl glycol, methyl diglycol, ethyl diglycol,
butyl diglycol, methyl triglycol, ethyl triglycol, butyl
triglycol, methyl tetraglycol, ethyl tetraglycol, butyl
tetraglycol, Polyglykol-M-250~ (Hoechst, molar mass: 260-
275 g/mol, hydroxyl number: 204-215), Polyglykol-M-350
(Hoechst, molar mass: 335-265 g/mol, hydroxyl number:
154-167), propylene glycol methyl ether, dipropylene
glycol methyl ether, tripropylene glycol methyl ether,
propylene glycol n-butyl ether, dipropylene glycol n-
butyl ether, tripropylene glycol n-butyl ether and
propylene glycol phenyl ether.
In the context of this invention, monohydroxyl
compounds also include cyclic esters having preferably
21 71 407
g
four or more carbon atoms in the ring, in which the ring
carbon atoms can also bear other substituents such as
alkyl, cycloalkyl, aryl, aralkyl or alkoxy instead of
hydrogen. Those which may be mentioned include mono-
alkyl-substituted ~-capro-lactones such as monomethyl-,
monoethyl-,monopropyl-,monoisopropyl-,monoethylhexyl-,
monodecyl-, monododecyl-~-caprolactone; in addition
dialkyl-~-caprolactones in which the two alkyl groups are
situated on the same carbon atom or on two different
;O Câr~On â-OmS bu~ nGt both on ~he c-carbon ator; n
addition trialkyl-~-caprolactones in which two or three
carbon atoms in the ring are substituted, as long as two
substituents are not located on the ~-carbon atom; in
addition alkoxy-~-caprolactones such as methoxy- and
- lS ethoxy-~-caprolactone; in addition cycloalkyl-, aryl- and
aralkyl-~-caprolactones such as cyclohexyl-, phenyl- and
benzyl-~-caprolactone. Preference is given to
unsubstituted ~-caprolactone.
other cyclic esters which can be used in the context
of the invention and contain at least one internal ester
able to undergo ring opening are y-butyrolactone, y-
valerolactone, ethylene carbonate, tetramethylene carbon-
ate, 2,2-dimethyl-4-phenyl-1,3-dioxolan-5-one, ~-n-
propyl-~-valerolactone, ~,~-dimethyl-~-valerolactone, 3-
ethyl-1,4-dioxan-2-one, 3,3,6-trimethyl-1,4-dioxan-2-one,
tetramethylglycolide, tetraphenylglycolide, 3-oxa-~-
caprolactone, ~-propiolactone, a,~-~is(chloromethyl)-
propiolactone, ~-butyrolactone, pivalolactone ~PVL),
thiobutyrolactone (TBL), ~-valerolactone (DVL), ~,~,y-
trimethoxy-~-valerolactone, 1,4-dithiane-2,5-dione,
trimethylene carbonate, neopentyl carbonate, ethyleneoxo-
lane, ~-methyl-~-isopropyl-~-caprolactone, propyleneoxo-
lane, 4-hydroxycyclohexanecarboxylic lactone, cis-di-
salicylide and trisalicylide and mixtures thereof.
Preferred compounds arey-butyrolactone, ~-valerolactone,
pivalolactone, thiobutyrolactone, ~-butyrolactone, ~-
caprolactone and mixtures thereof.
The amount of substance of these monohydroxy
compounds or cyclic esters which are added for the "in-
2171407
- ' --10--
situ" condendation embodiment is governed by the amount
of acid monomers. Generally, the amount of monohydroxy
compounds or cyclic esters is chosen such that for 1 mol
each of acid monomer, the amount of these modifiers is
5 between 0.1 and 0.9 mol, preferably between 0.2 and 0.8
mol, and most preferably between 0.3 and 0.7 mol.
In the context of the invention, volatile neutrali-
zation reagents which are useful are basic compounds
which do not form a covalent bond with the carboxyl
iv groups under the reac'~ion conditions. ~y such basic
compound or mixture thereof can be used. Preferred basic
compounds are amines, in particular tertiary amines,
amides, and in addition heterocycles, in particular
electron-deficient heteroaromatics, forexample pyridine,
15 pyridazine, pyrimidine, pyrazine, quinoline or isoquino-
line. Particularly preferred volatile basic neutrali-
zation reagents are represented by formula II,
r
Z ~ N ~ R formula II
R5
in which
20 R4 is alkyl or cycloalkyl, preferably having l to 8
carbon atoms, methyl, ethyl, propyl, butyl and
cyclohexyl being particularly preferred,
R5 is (CHz)l,
Z is (CH2)m or 0,
25 l is 0 to 5 and
m is 1 to 5.
Examples which may be mentioned include N-methyl-2-
piperidine,N-ethyl-2-piperidine,N-methylpyrrolidone,N-
ethylpyrrolidone, N-methylcaprolactam, 2,5-piperazine-
30 dione and N-methyl-2-oxazolidone. Particular preference
is given to N-methylpyrrolidone (N-methyl-2-pyrro-
lidinone).
- 2171407
The volatile basic neutralization reagents are added
in a proportion which permits sufficient neutralization
of the carboxyl-group-containing monomers before their
incorporation into the growing macromolecule. For
polymerization under standard conditions, this means that
an amount of volatile basic neutralization reagents of
preferably at least 10 mol%, in particular 20 to 70 mol%,
based on the amount of the carboxyl-group-containing
monomers, is sufficient.
;0 Poiymer A may be prepared using any desired reaction
conditions. The synthesis of the polymers A is usually
carried out at temperatures of 20 to 400 C, preferably
at 80 to 300 C, in particular at 100 to 230 C.
Advantageously, constant temperature under atmospheric
pressure is employed and if necessary with simultaneous
removal of low-boilers. But superatmospheric pressure,
preferably up to 15 bar, in particular up to 5 bar, may
also be employed.
The polymerizations for the preparation of the
polymers A can be initiated by thermally decomposing
free-radical formers known to those skilled in the art,
such as those selected from the group of the azo
compounds, peroxides, esters of peracids or
hydroperoxides. Organic peroxides are preferentially
used, preferably dialkyl peroxides, in particular di-
tert-butyl peroxide, di-tert-amyl peroxide or cumene
hydroperoxide.
To control the copolymerization, the procedure can
optionally be carried out with addition of a solvent
which is preferably removed in vacuo after the reaction
is completed. The amount of the solvent is generally up
to 50% by weight, preferably up to 20% by weight, and in
particular completely without further solvent, based on
the polymer A. The solvent to be preferably used is 3-
ethoxyethyl propionate, which reacts as a capped ethylacrylate under the reaction conditions. If necessary, to
set the molar mass, regulators generally known to those
skilled in the art can be processed, for example those
based on organic thio compounds.
21 71 407
-12-
After the synthesis is completed, the volatile basic
neutralization reagents can be separated off from the
polymers A, preferably in vacuo, and are then usually
available for reuse without complex purification.
The copolymers A, after at least partial
neutralization with further bases such as ammonia or
amines, preferably tri-, di- or monoalkylamines, for
example triethanolamine, morpholine or alkanolamines such
as 2-amino-1-methyl-1-propanol or alkali metal hydroxides
or alkaiine eartn metai hydroxides or mixtures tnereof,
may be dissolved in water and are then very
advantageously used as binders for aqueous printing inks
or as stabilizers for emulsion polymerization.
Generally, it is sufficient in this case to carry out a
` 15 partial neutralization of 50 to 95%, but preference is
given to excess neutralization to a pH of 7.5 to 11,
preferably 8 to 9.
To prepare the solution of the at least partially
neutralized resin on the manufacturing scale, inverse
dilution has proved to be advantageous, that is the
direct introduction of the resin melt of the copolymer of
type A into water/neutralization medium at a resin
temperature of 100 to 250 C, preferably 150 to 200 C,
and at least at atmospheric pressure. Expediently, the
aqueous mixture is then further kept at least atmospheric
pressure for 30 min to 3 hours at 80-95 C, preferably at
approximately 90 C.
optionally, particularly in the case of high-
viscosity melts of resins having a high glass transition
temperature, low molar mass saturated aliphatic
carboxylic acids and/or glycol ethers can be mixed in so
as to achieve a significant reduction of the melt
viscosity. Amounts of up to 20% by weight of additives
are expedient here, based on the amount of resin.
Carboxylic acids which can be used include formic acid,
lactic acid, malonic acid, succinic acid, tartaric acid
or citric acid, preferably acetic acid. Glycol ethers
which may be mentioned are ethers of ethylene glycol,
propylene glycol, butylene glycol, for example 2-n-
f
21 71 407
-13-
propoxyethanol, 2-(1-methylethoxy)ethanol, 2-n-butoxy-
ethanol, 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxy-
ethoxy)ethanol, 2-(2-butoxyethoxy)ethanol, triethylene
glycol monomethyl ether, tetraethylene glycol monomethyl
ether, 2,5,8,11-tetraoxadodecane, 1-methoxy-2-propanol,
l-ethoxy-2-propanol, tripropylene glycol mono-methyl
ether. Preferably, 2-(2-ethoxyethoxy)ethanol and/or 1-
methoxy-2-propanol is used. However, the inverse
dilution is usually carried out completely without
addition of soivents.
According to the invention, the synthetic resin
composition, in addition to the polymer A, optionally
also contains polymer B. The polymers B are prepared via
emulsion polymerization in the presence of at least
partially neutralized polymer A. The polymers A should
be present in an amount which is sufficient to bring
about the desired emulsifying effects. On the other
hand, both for economic reasons and for reasons of
influencing the application properties of the emulsion
2û polymers to be prepared, the amount of the polymers A
should not be too high. A content of polymers A of 4 to
56% by weight is therefore preferentially used, in
particular 10 to 50% by weight, based on the amount of
the polymers A and B. Very good results are achieved if,
2~ preferably, 12 to 42% by weight of polymers A based on
the sum of A and B are used.
Processes for emulsion polymerization are known to
those skilled in the art. Any such process can be used
to introduce polymer B. Conventionally they feature
carrying out a free-radical polymerization of
ethylenically unsaturated monomers in aqueous phase in
the presence of free-radical initiators and emulsifiers
and protective colloids. Said components can be
introduced in diverse ways into the emulsion polymeri-
zation. When the novel polymers A are used in emulsion
polymerizations, the presence of low molar mass
surfactants and protective colloids can be dispensed
with. Usually, most of the aqueous phase is introduced
in advance, a proportional addition of water during the
- 2171407
-14-
reaction being possible in the form of a free-radical
initiator solution or monomer preemulsion. The
polymers A can be introduced in advance completely or in
part and the rest can be added during the polymerization.
The monomers can be introduced in advance completely or
can be added in pure form or as preemulsion with
polymer A in water. The free-radical initiator is
usually partly introduced in advance and partly added as
aqueous solution. The mixture which is introduced into
~ne reactor berore tne reaction temperature or usually 20
to 99 C is set is termed the initial charge.
The polymerization is usually initiated by thermal
decomposition of the free-radical initiators or by redox
systems and can be considered to be completed when the
major part of the monomers which can be reacted by free-
radical chain reaction has been reacted. Usually,
approximately 0.001 to 0.1% by weight of residual mono-
mers remain in this process. Other useful processes or
process variants are described in detail, for example, in
Ullmann, Enzyklopadie der technischen Chemie
[Encyclopedia of Industrial Chemistry], 4th Edition,
Verlag Chemie, Weinheim (1980), Volume 19, pages 132 ff.
and in Encyclopedia of Polymer Science and Engineering,
Volume 6, Wiley & Sons, New York 1986, pages 1-51.
The polymer B of the dispersion is produced by
monomers which at least to a considerable part are
sparingly soluble in water and remain sparingly soluble
even when the pH is changed. Sparingly soluble is taken
to mean a solubility of less than 10% by weight, in
particular less than 5% by weight, at 25 C. The propor-
tion of the sparingly soluble monomers must be at least
sufficient that the resulting emulsion polymer is
insoluble in the aqueous phase under the polymerization
conditions and is present in the form of dispersed
particles. In the context of the invention, preferably,
mixtures are used which comprise at least 70% by weight
and, in particular, at least 90% by weight, of sparingly
soluble monomers.
2171407
~_ -15-
Suitable monomers contain at least one ethylenically
unsaturated group. The terms ethylenically unsaturated,
vinylically unsaturated and ~ unsaturated are used
synonymously. It is known to those skilled in the art
that such monomers may be linked to form polymers under
the conditions of the emulsion polymerization in an
aqueous medium. These include, for example, vinyl com-
pounds, styrenes and acrylates and derivatives thereof.
Suitable vinyl compounds include, for example, vinyl
chloride and vinyl esters such as vinyl acetate, vinyl
propionate, vinyl esters of Versatic acid, and also vinyl
esters of fatty acids such as vinyl laurate.
Suitable styrene compounds include styrene, vinyl-
toluene, ~-methylstyrene, ethylstyrene, iso-propyl-
styrene,tert-butylstyrene,2,4-dimethylstyrene,diethyl-
styrene, o-methyl-p-isopropylstyrene, halostyrenes such
as chlorostyrene, fluorostyrene and iodostyrene, 2,4-
cyanostyrene, hydroxystyrene, nitrostyrene, aminostyrene
and/or phenylstyrene. Preference is given in particular
to styrene, vinyltoluene and ~-methylstyrene.
Suitable acrylates which may be mentioned by way of
example are esters of acrylic acid, methacrylic acid and
crotonic acid, for example also esters which contain
hydroxyl functions, such as hydroxyethyl acrylate and
hydroxyethyl methacrylate.
In the emulsion polymerization, mixtures of such
ethylenically unsaturated monomers can also be
polymerized if they are suitable for the
copolymerization. In order to obtain dispersions having
glass transition temperatures of above 75 C, styrene or
styrene derivatives and/or methacrylates are preferably
used as starting materials.
Suitable initiators are usually water-soluble free-
radical-forming compounds, for example hydrogen peroxide,
peracetic acid, perbenzoic acid and perdisulfates, for
example potassium peroxodisulfate or ammonium peroxodi-
sulfate, perphosphates, peroxycarbonates and hydro-
peroxides, such as tert-butyl hydroperoxide. Suitable
redox catalyst systems include, for example, sodium
.
-- -
- 2171407
~ 16-
- persulfate/sodium formaldehyde sulfoxylate, cumene hydro-
peroxide/sodiummetabisulfite,hydrogenperoxide/ascorbic
acid and sulfur dioxide/ammonium persulfate. Azo
compounds are also suitable, such as 4,4-azo-bis-(cyano-
pentanoic acid). The catalysts are used in conventional
catalytically active concentrations. These are generally
between 0.01 to 4.0% by weight, based on the dispersion.
In particular embodiments, other components conven-
tional in emulsion polymerization can be used. These
are, for example, accelerators, burrers and any otner
constituents which can be used in the emulsion
polymerization reaction mixture in addition to the novel
polymers A and are known from the prior art for emulsion
polymerization processes. These are, for example, Fe2'
salts which effect, e.q., in combination with sodium
formaldehyde sulfoxylates, an acceleration of the free-
radical formation by free-radical initiators, or buffer
salts, for example phosphates, carbonates, citrates,
which can be used to stabilize the pH. Such additives
generally can be present at up to 3% by weight in the
dispersion. When the emulsion polymerization is carried
out, in addition to setting the concentration of the
liquor, it has proved to be particularly expedient to
carry out a prepolymerization of 1 to 15% by weight of
the init-iator and amount of monomer so that the quality
of the dispersion can be controlled more exactly, in
particular with respect to transparency and viscosity.
The invention further relates to the use of the
polymer mixture discussed above in any desired coating
application, in particular for the preparation of binders
for water-borne printing varnishes and printing inks for
printing paper, cardboard, cardboard packaging, films and
the like, for example with the inking unit of a sheet-fed
or web offset machine, from damping units, separate
varnishing units of sheet-fed or web offset printing
machines, sheet-fed varnishing machines, photogravure
machines and flexographic machines. When the novel resin
solutions and dispersions are used as binder carriers for
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printing varnishes and printing inks, their solids
content is generally 40 to 75% by weight.
The polymers can be used in any desired varnish or
ink. These varnishes and inks preferably contain 1 to
70% by weight of the novel dispersions and/or 1 to 40% by
weight of the novel solid resins and 0 to 60% by weight
of glycols or glycol ethers, 0 to 30% by weight of
wetting agent, 0 to 35% by weight of neutralization agent
(bases), 0 to 30% by weight of natural and/or synthetic
waxes, 0 to 1.5% by weight of defoamer, 0 to 80~ by
weight of water, 0 to 60% by weight of pigments, 0 to 2%
by weight of additives to improve abrasion resistance,
for example Byk~ 301 (Byk-Mallinckrodt), 0 to 3% by
weight of additives to improve scratch resistance, for
example Aqua Polyfluo~ (Micro Powders), o to 1.5% by
weight of leveling agents, for example Triton~ X 200
(Rohm & Haas), and 0 to 5% by weight of softeners, for
example triethyl citrate. The pigment/binder ratio in
grinding operations is generally between 5:95 and 95:5,
preferably 30:70 to 70:30. For use as pigment grinding
components, solids contents of above 30% by weight are
also expedient.
To make up these stock dyes, pigments and printing
inks, mixtures of different types of dispersions or resin
solutions are also expedient. To incorporate pigments
(for example titanium dioxide, colored pigments,
synthetic carbon blacks), fillers (for example talc,
China clay, waxes), dyes and leveling agents into the
solutions and/or dispersions and/or mixtures thereof
and/or dilutions thereof, the generally conventional
milling, mixing, kneading and grinding apparatuses can be
used, optionally in the presence of conventional
dispersant.
The preparation of the novel polymers A and the
preparation of the novel polymer mixtures by emulsion
polymerization and their use in printing inks and print-
ing varnishes is illustrated by the examples below. The
parts and percentages cited in the examples relate to the
weight, unless otherwise noted. All of the examples were
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carried out under protective gas, preferably nitrogen.
The examples are for illustrative purposes only and do
not limit the invention.
EXAMPLE8
Example 1
A monomer mixture comprising acrylic acid (77 g),
styrene (63 g) and ~-methylstyrene (55 g) and, in
parallel thereto, cumene hydroperoxide (8 g) are added
with stirring over the course of approximately 4 hours to
N-methylpyrrolidone (100 g) heated to 225 C at a
pressure of 150 kPa, the pressure increasing to about
200 kPa. After removing N-methylpyrrolidone in vacuo at
230 C, a solid resin is obtained having an acid number
of 222 mg/g, a Tg of 76 oc and a M~ of 1,800.
Example 2
A monomer mixture comprising acrylic acid (37 g),
styrene (30 g) and a-methylstyrene (33 g) and, in
parallel thereto, cumene hydroperoxide (1.7 g) are added
with stirring over the course of approximately 5 hours to
N-methylpyrrolidone (23 g) heated to 200 C and the
mixture is kept for a further hour at this temperature.
After removing N-methylpyrrolidone in vacuo at 220 C, a
solid resin is obtained having an acid number of 235
mg/g, a Tg of 86 C and an M~ of 4,500.
Example 3
A monomer mixture of acrylic acid (40 g) and styrene
(56 g) and, in parallel thereto, cumene hydroperoxide
(1.5 g) are added with stirring over the course of
approximately 5 hours to N-methylpyrrolidone (23 g)
heated to 180 C and the mixture is kept at this tempera-
ture for a further hour. After removing N-methylpyrroli-
done in vacuo at 210 C, a solid resin is obtained having
an acid number of 245 mg/g, a Tg of 103 oC and an M~ of
11, 000.
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_
Example 4
A monomer mixture comprising acrylic acid (36 g),
styrene (27 g) and ~-methylstyrene (31 g) and, in
parallel thereto, cumene hydroperoxide (1.4 a) are added
with stirring over the course of approximately 5 hours to
- N-methylpyrrolidone (23 g) heated to 170 C and the
mixture is kept at this temperature for a further hour.
After removing N-methylpyrrolidone in vacuo at 230 C, a
solid resin is obtained having an acid number of 243
mg~g, a Tç of 141 C and an M~ of 13,000. If 1-methoxy-2-
propanol (11.5 g) and acetic acid (100%, 9.4 g) are added
to the still liquid polymer before solidification and
this mixture is introduced into water (143 g)/ammonia
(25% strength, 36 g), a resin solution having a solids
- 15 content of 33.5%, a p~ of 9.1 and a viscosity of
1521 mPa s (Ubbelohde) is obtained.
Comparison:
25% strength solutions in water/ammonia are prepared
from solid resins of the Examples 2 and 3 and the resins
of the prior art below, 110% neutralization of the acid
groups being performed (i.e., the amount of substance of
basic reagents corresponds to 110 % of the amount of
substance of acid present). The solutions are shaken for
2 minutes in the Skandex mixer and the density is deter-
mined.
Test series I contains small amounts of defoamer,test series II contains a standard amount of a commercial
defoamer, test series III corresponds to test series II
after storage for 2 days.
Test I: addition of 0.2% (based on resin solution)
of Surfinol~ 104 (defoamer, Air Products)
Test II: addition of 1.5% (based on resin solution)
of Surfinol~ 104
Test III: resin solution from test II after storage
for 2 days.
- 2171407
- 20 -
Fo~ E~mple 2 C~ R~ E~mple 3 C~ t;~_ R~ 2
~ml 1
Mw 4,5~ M~ a~x.4,2~ Mw app~x. ll,~ M~ a~rox. lO,~
~l g/mol g/mol ~mol
T~t 1 0.76 0.65 0.79 0.7l
T~t n 0.87 0.78 0.88 0.77
T~t ~I 0.83 0.69 0.85 0.74
standard resin frGm acry~i~ a~id a~d s~yr~ne
according to EP-A 0 068 024 or EP-A 0 129 913 ~
both documents are hereby incorporated by
reference.
In this test, higher density is related to less
foam.
Example 5
A resin solution from Example 4 diluted with water
to a solids content of 25% iS heated under nitrogen to 90
C (600 g). After 90 C is reached, styrene (10 g) and,
in parallel thereto, ammonium peroxodisulfate (0.4 g) in
water (5 g) are added and the mixture is stirred for
20 minutes at 90 C. In the course of approximately
3 hours, styrene (440 g) is then added and, in parallel
thereto, ammonium peroxodisulfate (2 g) in water (200 g).
The mixture is allowed to react further for
approximately 1 hour, if appropriate with addition of a
redox system, the mixture is cooled and thus a fleck-free
dispersion is obtained having a solids content of
- 25 approximately 47.8%, a pH of 8.7 and a viscosity of
approximately 1,230 mPa s (Ubbelohde).
Example 6
73 parts of a 43% strength ammoniacal resin solution
(110% neutralization) of Example 1 are admixed with
70 parts of the dispersion from Example 5 adjusted to 43%
solids, 1 part of water and 2 parts of butyl diglycol and
0.8 parts of Surfinol 104. This high gloss overprinting
-21-
varnish is adjusted with water to a DIN runout time of
50 s (4 mm/23 C) t41% solids content).
Example 7
67 parts by weight of a 40% strength aqueous
ammoniacal solution of resin from Example 1 are shaken
with glass balls in the paint shaker together with
16 parts of Permanent Gelb GRX~ (yellow pigment,
Hoechst), 0.7 parts of Surfinol 104 and 0.9 parts of
water for 30 minutes at room temperature. After
screening off the mixture through a 100 ~m screen, a
stock ink is obtained which, after dilution to 7% pigment
content with dispersions of Example 5, gives a suitable
printing ink.
85 g of an overprinting varnish from Example 6 or a
printing ink according to Example 7 are shaken in the
Skandex mixer for 5 minutes in a 100 ml flask and then
the density is determined.
Foam volume = tl.05: density x 100) - 100.
Comparative foam test on overprinting varnishes and
printing inks:
Test I: overprinting varnish/printing ink made up
freshly
Test II: overprinting varnish/printing ink after storage
for 2 days
Foam volume o~ e co~p~:on P~ting ink G~ on
(1.05: density x 100) vamish ~ il]g Example 7 printing ink
-100 Example 6 varnish
Tcst series 1 7.4 14.3 9.6 15.2
Test series 11 9.4 17.3 11.6 20.2
overprinting varnish, produced similarly to
Example 6 with a resin of acrylic acid and
styrene according to EP-A 0 068 024 or
EP-A 0 129 913 and a dispersion according to
21 7 1 407
~ -22-
WO-A 91/04 990, which is incorporated by
reference.
printing ink produced similarly to Example 7
with a resin of acrylic acid and styrene
according to EP-A 0 068 024 or EP-A 0 129 913
and a dispersion according to WO 91/04 990,
which is incorporated by reference.
Although only a few exemplary embodiments of this
invention have been described in detail above, those
skilled in the art will readily appreciate that many
modifications are possible in the exemplary embodiments
without materially departing from the novel teachings and
advantages of this invention. Accordingly, all such
modifications are intended to be included within the
scope of this invention.
