CA2171407A1 - Anionic polymer mixtures having reduced foam formation in water - Google Patents

Abstract

Anionic polymer compositions of (a) an acid-group-containing polymer A which was obtained 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, (b) a water-insoluble polymer B in the form of latex particles, which can be prepared by emulsion polymerization of ethylenically unsaturated compounds in the presence of the polymer A, have reduced foam formation as binders in water-borne printing varnishes and printing inks.

Description

._ L ' ~ ' ~ --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 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 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 .

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 `

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 ~ -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 .

_ 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 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 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-- ' --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

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).

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.

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 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 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.

~_ -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 .

-- -~ 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 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 carried out under protective gas, preferably nitrogen.
The examples are for illustrative purposes only and do not limit the invention.

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.

_ 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.

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 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 ~ -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.

Claims (21)

1. 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 one or more carboxyl-group-containing ethylenically unsaturated compounds with one or more other ethylenic-ally 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.

2. A polymer composition as claimed in claim 1, wherein the polymer A has an acid number in the range from 90 to 400 mg/g.

3. A polymer composition as claimed in claim 1, wherein the glass transition temperature of the polymer A
is between 0 and 180 °C.

4. A polymer composition as claimed in claim 1, wherein polymer B is present.

5. A polymer composition as claimed in claim 1, wherein polymer A contains 5 to 70% by weight of carboxyl-group containing compounds and 30 to 95% by weight of the other ethylenically unsaturated compounds.

6. A polymer composition as claimed in claim 1, wherein in polymer A, the content of hydroxyl compounds bound in ester groups is between 0 and 25% by weight.

7. A polymer composition as claimed in claim 1, wherein polymer A has a weight-average molar mass of 300 to 100,000 g/mol.

8. A polymer composition as claimed in claim 1, wherein the other ethylenically unsaturated compound comprises one or more of vinyl aromatics or open-chain conjugated dienes.

9. A polymer composition as claimed in claim 1, wherein polymer A is prepared in the presence of one or more monohydroxyl compounds such that an in situ conden-sation with these monohydroxyl compounds takes place.

10. A polymer composition as claimed in claim 9, wherein the monohydroxyl compound comprises one or more monoalcohols or monoetherified polyalkylene oxide compounds or cyclic esters.

11. A polymer composition as claimed in claim 1, wherein the volatile basic neutralization reagent comprises one or more amines.

12. A polymer composition as claimed in claim 1, wherein the volatile basic neutralization reagent comprises a compound having the formula (II) (II) in which R4 is alkyl or cycloalkyl, R5 is (CH2)l, Z is (CH2)m or O, l is 0 to 5 and m is 1 to 5.

13. A polymer composition as claimed in claim 4, which comprises 4 to 56% by weight of polymer A based on the weight of polymers A and B.

14. A polymer composition as claimed in claim 4, wherein polymer B is formed from one or more vinyl compounds, styrenes, and acrylates.

15. A process for the preparation of a polymer composition as claimed in claim 1, which comprises (a) preparing an acid-group-containing polymer A by polymerization of one or more carboxyl-group-containing ethylenically unsaturated compounds with one or more other ethylenically unsaturated compounds in the presence of one or more volatile basic neutralization reagents, at least partially neutralizing polymer A 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 at least partially neutralized polymers A.

16. A process for the preparation of a polymer composition as claimed in claim 15, wherein the volatile neutralization reagents comprise basic compounds which do not form a covalent bond with the carboxyl groups under the reaction conditions.

17. A process for the preparation of a polymer composition as claimed in claim 15, wherein the volatile basic neutralization reagents comprise one or more compounds of formula (II), (II) in which R4 is alkyl or cycloalkyl, R5 is (CH2)l, Z is (CH2)m or O, l is 0 to 5 and m is 1 to 5.

18. A process for the preparation of a polymer composition as claimed in claim 15, wherein the volatile basic neutralization reagents are used in an amount of 20 to 70 mol%, based on the carboxyl-group-containing monomers.

19. A process for the preparation of a polymer composition as claimed in claim 15, wherein, during the polymerization of the carboxyl-group-containing ethylen-ically unsaturated compounds, an in situ condensation with monohydroxyl compounds is carried out.

20. A binder for water-borne printing varnish or printing ink comprising a polymer composition as claimed in claim 1.

21. A substrate coated with a coating comprising a binder as claimed in claim 20.