EP1132521A2 - Paper coating colour based on slightly crosslinked binders - Google Patents

Abstract

The present invention provides paper coating slips comprising a low-crosslink copolymer as their binder.

Description

The present invention relates to paper coating slips containing a copolymer composed of 45 to 74.8% by weight at least one monomer, the homopolymer of which has a glass transition temperature <20 ° C. (monomers A), 25 to 54.8% by weight at least one monomer whose homopolymer has a glass transition temperature> 50 ° C (monomers B), 0.001 to 1.0% by weight at least one crosslinking monomer with at least two non-conjugated vinyl groups (monomers C), and optional 0 to 10% by weight at least one monomer containing acid groups (monomers D) and 0 to 10% by weight at least one further monomer (monomers E).

The invention further relates to papers which contain these paper coating slips are coated and processes for printing of these papers.

Paper coating slips essentially consist of a polymer Binder and a white pigment. By coating with Paper coating slips get raw papers a smooth, white surface. In particular, paper coating slips are said to be an improvement printability.

The binders used in paper coating slips are it is usually an acrylate or styrene / butadiene copolymer. Corresponding paper coating slips are, for example, in the WO 97/00776.

The object of the present invention was to make paper coating slips with improved properties or alternative paper coating slips with a new raw material base.

Accordingly, paper coating slips containing a copolymer as a binder are built up from 45 to 74.8% by weight at least one monomer, the homopolymer of which has a glass transition temperature <20 ° C. (monomers A), 25 to 54.8% by weight at least one monomer whose homopolymer has a glass transition temperature> 50 ° C (monomers B), 0.001 to 1.0% by weight at least one crosslinking monomer with at least two non-conjugated vinyl groups (monomers C), and optional 0 to 10% by weight at least one monomer containing acid groups (monomers D) and 0 to 10% by weight at least one further monomer (monomers E), made available.

With the glass transition temperature (T _g ), the limit value of the glass transition temperature is meant, which, according to G. Kanig (Kolloid-Zeitschrift & Zeitschrift fur Polymer, Vol. 190, page 1, equation 1) strives with increasing molecular weight. The glass transition temperature is determined by the DSC method (differential scanning calorimetry, 20 K / min, midpoint measurement, DIN 53765). The T _g values for the homopolymers of most monomers are known and are listed, for example, in Ullmann's Encyclopedia of Industrial Chemistry, VCH Weinheim, 1992, 5th edition, vol. A21, p. 169; further sources of glass transition temperatures of homopolymers are, for example, J. Brandrup, EH Immergut, Polymer Handbook, 1 ^st Ed., J. Wiley, New York, 1966, 2 ^nd Ed., J. Wiley, New York, 1975, and 3 ^rd Ed ., J. Wiley, New York, 1989.

C ₁ to C ₁₀ alkyl groups in the following are linear or branched alkyl radicals having 1 to 10 carbon atoms, for example methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, iso-butyl, tert -Butyl, n-pentyl, isopentyl, tert-pentyl, n-hexyl, 2-ethylhexyl, n-nonyl or n-decyl. C ₅ to C ₁₀ cycloalkyl groups are preferably cyclopentyl or cyclohexyl groups which are optionally substituted by 1, 2 or 3 C ₁ to C ₄ alkyl groups.

According to the invention, a copolymer is used as the binder, 45 to 74.8% by weight, preferably 50 to 65% by weight, each based on the copolymer, at least one monomer A in copolymerized Contains form. The copolymer is accordingly obtained by polymerizing a mixture of monomers which at least one monomer A to 45 to 74.8% by weight, preferably to 50 to 65% by weight, based in each case on the total amount of the monomer mixture, contains. At this point it should be noted that the in the description percentages in the Copolymer copolymerized monomers A to E generally the Quantities of these monomers in the monomer mixture to be polymerized should correspond and vice versa.

Suitable monomers A are preferably vinyl ethers of C ₃ to C ₁₀ alkanols, branched and unbranched C ₃ to C ₁₀ olefins, C ₁ to C ₁₀ alkyl acrylates, C ₅ to C ₁₀ alkyl methacrylates, C ₅ to C ₁₀ cycloalkyl acrylates and methacrylates, C ₁ to C ₁₀ dialkyl maleinates and / or C ₁ to C ₁₀ dialkyl fumarates. Monomers A whose homopolymers have T _g values of <0 ° C. are particularly preferred. Particularly preferred as monomers A are ethyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, di-n-butyl maleate and / or di n-butyl fumarate or mixtures thereof.

Suitable monomers B are vinyl aromatic monomers, C ₁ -C ₄ -alkyl methacrylates and / or α, β-unsaturated carboxylic acid nitriles or carboxylic acid dinitriles. They are used in amounts of 25 to 54.8% by weight and preferably 35 to 50% by weight, based in each case on the total amount of the monomer mixture, for the polymerization. Accordingly, 25 to 54.8% by weight and preferably 35 to 50% by weight of the copolymer used according to the invention is composed of at least one monomer B in copolymerized form. Vinylaromatic monomers are understood to mean, in particular, derivatives of styrene or of α-methylstyrene in which the phenyl nuclei are optionally substituted by 1, 2 or 3 C ₁ to C ₄ alkyl groups, chlorine and / or methoxy groups. Monomers B whose homopolymers have a glass transition temperature> 80 ° C. are preferred. Particularly preferred monomers B are styrene, α-methylstyrene, o- or p-vinyltoluene, methyl methacrylate, acrylonitrile, methacrylonitrile, maleic acid dinitrile, fumaric acid dinitrile or mixtures thereof.

The at least one monomer C is obtained in the monomer mixture on their total amount, 0.001 to 1 wt .-% used. Accordingly, the copolymer is 0.001 to 1 wt .-% built up at least one monomer C in polymerized form. The copolymer preferably contains 0.001 to 0.5% by weight. or copolymerized 0.001 to 0.1 wt .-% of monomers C. The Copolymer often contains ≥ 0.001% by weight, ≥ 0.002% by weight, ≥ 0.003% by weight, ≥ 0.004% by weight, ≥ 0.005% by weight, ≥ 0.006% by weight, ≥ 0.007% by weight, ≥ 0.008% by weight, ≥ 0.009% by weight, ≥ 0.01% by weight, ≥ 0.02% by weight, ≥ 0.03% by weight, ≥ 0.04% by weight, ≥ 0.05% by weight, ≥ 0.06 % By weight, ≥ 0.07% by weight, ≥ 0.08% by weight, ≥ 0.09% by weight, ≥ 0.1 % By weight, ≥ 0.2% by weight, ≥ 0.3% by weight, ≥ 0.4% by weight, ≥ 0.5% by weight, ≥ 0.6% by weight, ≥ 0.7% by weight, ≥ 0.8% by weight, ≥ 0.9% by weight and 1% by weight or at <1% by weight, ≤ 0.9% by weight, ≤ 0.8% by weight, ≤ 0.7% by weight, ≤ 0.6 wt%, ≤ 0.5 wt%, ≤ 0.4 wt%, ≤ 0.3 wt%, ≤ 0.2 % By weight, ≤ 0.1% by weight, ≤ 0.09% by weight, ≤ 0.08% by weight, ≤ 0.07 % By weight, ≤ 0.06% by weight, ≤ 0.05% by weight, and all values in between, at least one monomer C in polymerized form. As at least a monomer C are monomers with at least two non-conjugated ethylenically unsaturated double bonds. Examples of this are two monomers containing vinyl residues, two Monomers containing vinylidene residues and two alkenyl residues Monomers. The di-esters are particularly advantageous dihydric alcohols with α, β-monoethylenically unsaturated monocarboxylic acids among which acrylic and methacrylic acid are preferred are. Examples of such two non-conjugated ethylenic Monomers containing unsaturated double bonds are alkylene glycol diacrylates and dimethacrylates, such as ethylene glycol diacrylate, 1,2-propylene glycol diacrylate, 1,3-propylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,4-butylene glycol diacrylates and ethylene glycol dimethacrylate, 1,2-propylene glycol dimethacrylate, 1,3-propylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate as well as divinylbenzene, vinyl methacrylate, vinyl acrylate, Allyl methacrylate, allyl acrylate, diallyl maleate, diallyl fumarate, Methylene bisacrylamide, cyclopentadienyl acrylate, triallyl cyanurate or triallyl isocyanurate.

The copolymer can optionally be obtained by polymerizing a monomer mixture which comprises up to 10% by weight or 0.1 to 7% by weight or 0.5 to 5% by weight, based in each case on the total amount of monomers, of at least one monomer D. contains. Accordingly, the copolymer can contain up to 10% by weight or 0.1 to 7% by weight or 0.5 to 5% by weight of at least one monomer D in copolymerized form. It is favorable if the copolymer contains 1 to 4% by weight of monomer D in copolymerized form. The monomers D are ethylenically unsaturated monomers which can form anionic groups. These groups are preferably carboxylate, phosphonate or sulfonate groups, but in particular carboxylate groups. Particularly preferred monomers D are monoethylenically unsaturated alkyl or arylsulfonic acids, such as vinylsulfonic acid, methallylsulfonic acid, vinylbenzenesulfonic acid, acrylamidoethanesulfonic acid, acrylamido-2-methylpropanesulfonic acid, 2-sulfoethylacrylate, 2-sulfoethyl methacrylate, 3-sulfopropylacrylate, 3-sulfo-methacrylate, and 3-sulfo-methacrylate, ₃ - to C ₆ -carboxylic acids, α, β-ethylenically unsaturated C ₄ - to C ₈ -dicarboxylic acids or their anhydrides, such as acrylic acid, methacrylic acid, crotonic acid, fumaric acid, maleic acid, maleic anhydride, itaconic acid and itaconic anhydride as well as the alkali metal or ammonium salts of the above Monomers, especially their sodium salts.

The monomer mixture can optionally also contain up to 10% by weight, based on its total amount, of at least one monomer E. Accordingly, the copolymer optionally contains up to 10% by weight of at least one monomer E in copolymerized form. The content of monomer E copolymerized in the copolymer can, however, also be 0.1 to 8% by weight, 0.2 to 4% by weight but also 0.5 to 2% by weight or 0.5 to 1.5% by weight .-%. Suitable monomers E are monomers with conjugated vinyl groups, such as 1,3-butadiene or isoprene, and free-radically polymerizable monomers with at least one epoxy group, such as glycidyl acrylate and glycidyl methacrylate, N-alkylol group, such as N-methylolacrylamide and N-methylolmethacrylamide, N-alkyloxy group , such as N- (methoxymethyl) acrylamide and N- (methoxymethyl) methacrylamide and diacetone acrylamide, 2- (1-aziridinyl) ethyl methacrylate and also amides α, β-ethylenically unsaturated C ₃ - to C ₆ -carboxylic acids, n-hydroxy-C ₂ -C ₆ alkyl esters of α, β-ethylenically unsaturated C ₃ to C ₆ carboxylic acids and / or N-vinyl lactams, such as, for example, methacrylic acid and acrylic acid C ₁ -C ₆ hydroxyalkyl esters, such as 2-hydroxyethyl, 3- Hydroxypropyl or 4-hydroxybutyl acrylate and methacrylate, as well as acrylamide and methacrylamide. Suitable monomers E are also monomers with SiR ¹ R ² R ³ groups in which R ¹ , R ² and R ³ independently of one another are C ₁ to C ₄ alkyl or alkoxy groups, such as vinyltrialkoxysilanes, for example vinyltrimethoxysilane, vinyltriethoxysilane, or acryloxy and methacryloxysilanes, for example γ-methacryloxypropyltrimethoxysilane and β-methacryloxyethyltrimethylsilane. The copolymer preferably contains no monomer E in copolymerized form.

The monomers can preferably be free radical or as far as possible can also be polymerized anionically or cationically. Both the radical as well as ionic polymerization are more common Polymerization methods known to the person skilled in the art.

The radical polymerization can, for example, in solution, e.g. in water or an organic solvent (solution polymerization), in aqueous dispersion (emulsion polymerization or suspension polymerization) or in bulk, i.e. essentially in the absence of water or organic solvents (Bulk polymerization) are carried out.

The copolymer used according to the invention is advantageous by radically initiated aqueous emulsion polymerization manufactured.

The free-radically initiated aqueous emulsion polymerization can for example discontinuously, with or without the use of Seed latices, with presentation of all or individual components of the Reaction mixture, or semi-continuously, preferably under partial Submission and subsequent dosing of the or individual components of the reaction mixture, or according to the dosing process without submission be performed. The polymerization can also be carried out in stages be carried out, the monomer composition differentiate between the individual levels.

The monomers can be in the radically initiated aqueous Emulsion polymerization as usual in the presence of a water-soluble Initiator and an emulsifier are polymerized.

Suitable initiators are, for example, sodium, potassium and Ammonium peroxodisulfate, tert-butyl hydroperoxide, water soluble Azo compounds such as 2,2'-azobis (isobutyronitrile), 2,2'-azobis (2,4-dimethylvaleronitrile) and 2,2'-azobis (amidinopropyl) dihydrochloride or redox initiators, such as Hydrogen peroxide / ascorbic acid. The initiators become frequent in amounts of 0.1 to 3 wt .-%, based on the total amount of Monomers A to E used.

Suitable emulsifiers are, for example, alkali metal salts of longer-chain ones Fatty acids, alkyl sulfates, alkyl sulfonates, alkylated Aryl sulfonates or alkylated bisphenyl ether sulfonates. Furthermore come as emulsifiers reaction products of alkylene oxides, especially ethylene oxide and / or propylene oxide with fatty alcohols or acids or phenols, or alkylphenols and their sulfated derivatives. Emulsifiers are commonly used in Amounts of up to 5% by weight based on the total amount of monomers A to E, used.

In addition to or alternatively to emulsifiers, natural ones can also be used and / or synthetic protective colloids, such as, for example Starch, casein, gelatin, alginates, hydroxycellulose, methylcellulose, Carboxymethyl cellulose or polyvinyl alcohols are used come.

In the case of aqueous secondary dispersions, the copolymer first by solution polymerization in an organic solvent prepared and then the solution polymer with or dispersed in water without emulsifier. The organic solvent can then be distilled off. The production of aqueous Secondary dispersions are known to the person skilled in the art and for example described in DE-A 37 20 860.

To adjust the molecular weight of the copolymers so-called regulators in the polymerization in amounts of up to 2 wt .-%, based on the total amount used for the polymerization Monomers A to E can be used. For example, are suitable Compounds containing thiol groups, such as Mercaptoethanol, mercaptopropanol, thioglycerin, thioglycolic acid ethyl ester, Thioglycolic acid methyl ester and tert-dodecyl mercaptan as well as trichlorobromomethane and allyl alcohols.

Polymerization pressure and polymerization temperature are of minor importance Importance. Generally one works at temperatures between 20 and 200 ° C, preferably at temperatures of 50 to 120 ° C and particularly preferably between 60 and 90 ° C. Advantageous becomes the radically initiated aqueous emulsion polymerization at atmospheric pressure (1 bar absolute) under an inert gas atmosphere, such as carried out under nitrogen or argon.

Following the actual polymerization reaction, it is in usually required odorants, such as residual monomers and others organic volatile constituents from the invention used to remove aqueous polymer dispersion. This can in a manner known per se physically by distillation Removal (especially by steam distillation) or by Stripping can be achieved with an inert gas. The lowering the residual monomers can also be chemically obtained by radical postpolymerization, especially under the influence of redox initiator systems, such as in DE-A 44 35 423, DE-A 44 19 518 and are listed in DE-A 44 35 422, before, during or after the distillative treatment. As an oxidizing agent for Redox-initiated post-polymerization are particularly suitable for hydrogen peroxide, tert-butyl hydroperoxide, cumene hydroperoxide or Alkali peroxodisulfates. Suitable reducing agents are sodium disulfite, Sodium bisulfite, sodium dithionite, sodium hydroxymethanesulfinate, Formamidine sulfinic acid, acetone bisulfite (= sodium bisulfite addition product on acetone), ascorbic acid or reducing sugar compounds. Postpolymerization with the redox initiator system in the temperature range from 10 to 100 ° C, preferably at 20 to 90 ° C. The redox partners can the aqueous polymer dispersion independently completely, in portions or continuously over a period of time from 10 minutes to 4 hours. For improvement the post-polymerization effect of the redox initiator systems can also change the dispersion of soluble salts of metals Values such as iron, copper or vanadium salts added become. Complexing agents, the metal salts, are also frequently added keep in solution under the reaction conditions.

In addition, the aqueous copolymer dispersions can be customary Excipients such as alkali hydroxide, ammonia or ethanolamine as neutralizing agent, silicone compounds as defoamers, Biocides as well as silicone oils or waxes to reduce stickiness contain.

The solids content of the aqueous copolymer dispersion obtained is preferably 30 to 80% by weight, particularly preferably 45 to 75% by weight.

The determined via quasi-elastic light scattering (ISO standard 13 321) number average particle diameters of those in the aqueous polymer dispersions contained polymer particles is preferably in the range from 50 to 300 nm, particularly preferably in Range from 100 to 200 nm. The polymer particles have in the Rule up a monomodal particle size distribution.

Solution polymerization can be continuous, discontinuous as a batch process or preferably semi-continuously in the feed process be performed. In the latter case, a Part of the monomers A to E presented in the polymerization vessel the polymerization temperature is heated and the rest of the monomers be fed continuously.

Can be used as a solvent for radical solution polymerization for example water, alcohols, such as iso-propanol or iso-butanol, aromatics, such as toluene or xylene, Ethers, such as, for example, tetrahydrofuran or dioxane, ketones, such as acetone or cyclohexanone and esters such as Ethyl acetate or n-butyl acetate can be used.

Preferred initiators are dibenzoyl peroxide, tert-butyl perpivalate, tert-butyl-2-ethylhexanoate, tert-amyl-2-ethylhexyl peroxide, Di-tert-butyl peroxide, cumene hydroperoxide, dilauroyl peroxide, Didecanoyl peroxide, methyl ethyl ketone peroxide, 2,2'-azobis (isobutyronitrile), 2,2'-azobis (2,4-dimethylvaleronitrile) and 2,2'-Azobis (2,3-dimethylbutyronitrile) to name.

In bulk polymerization, part of the polymerization batch is generally presented from monomers and radical initiators, heated to the polymerization temperature and then the rest fed continuously.

However, the copolymer is preferred by a free radical initiated aqueous emulsion polymerization produced and in Form used its aqueous copolymer dispersion.

The glass transition temperature of the copolymer is usually -40 to + 50 ° C, preferably 0 to + 30 ° C and particularly preferred +5 to + 15 ° C.

The paper coating slips contain the copolymer as a binder preferably in amounts of 1 to 50% by weight, in particular 5 to 20 wt .-%, based on the amount of pigment (solid / solid).

The pigments are usually the main component of the paper coating slips Commonly used pigments are, for example natural or precipitated calcium carbonate, kaolin, calcined or aggregated clay, talc, gypsum, titanium dioxide, Zinc oxide, barium sulfate and satin white. Together with one or Several of these inorganic pigments can also be plastic pigments be used.

Furthermore, the paper coating slips can be conventional dispersants contain. Suitable dispersants are, for example, polyanions, for example of polyphosphoric acids or of polyacrylic acids (Polysalts), which are usually present in amounts of 0.1 to 3 wt .-%, based on the amount of pigment, are included.

In addition, the paper coating slips so-called "cobinder" contain. Starch, casein and gelatin are natural cobinders and alginates, as modified natural products, hydroxyethyl cellulose, Methyl cellulose and carboxymethyl cellulose as well as cationic modified starch mentioned. But it can also be conventional synthetic Cobinder, for example based on vinyl acetate or acrylate, be used. The amount of cobinder is usually 0.1 to 10 wt .-%, based on the amount of pigment.

To produce the paper coating slip, the components in mixed in a known manner, the copolymer in general is used in the form of an aqueous dispersion.

The water content in the paper coating slip is usually to 40 to 75% by weight, based on the solids of the paper coating slip, set.

The paper coating slip can be applied to the coating papers are applied (see Ullmann's Encyclopedia der Technische Chemie, VCH Weinheim, 1979, 4th edition, Vol. 17, pages 603 to 609).

Papers come in a wide variety of types as papers to be coated Thick, also cardboard, etc. into consideration.

The papers are preferably coated with 2 to 50 g / m ^{2 of} the paper coating slip (calculated dry).

The coated with the paper coating slips according to the invention Papers show good printability. The papers are special also for offset printing, gravure printing or flexographic printing suitable.

Examples Analytics

The number average particle diameter of the polymer particles was by dynamic light scattering on a 0.005 to 0.01 weight percent aqueous dispersion at 23 ° C using an autosizer IIC from Malvern Instruments, England. Specified becomes the mean diameter of the cumulative evaluation (cumulant z-average) of the measured autocorrelation function (ISO standard 13 321).

The solids levels were determined by an aliquot 6 hours at 140 ° C in a drying cabinet. It two separate measurements were carried out. The one in the The value given in each example represents the mean of two measurement results.

1. Synthesis of the copolymers by radically initiated aqueous emulsion polymerization

General preparation instructions for Examples 1 to 7 and the comparative example.

In a 4 1 polymerization vessel with stirrer and reflux condenser 498 g deionized water and 40 g an aqueous polystyrene seed latex (polymer solids content 33% by weight, number average particle diameter 30 nm) and 90 g from inlet I submitted and heated to 70 ° C with stirring and nitrogen atmosphere. After an internal temperature of 60 ° C. had been reached, 9 g of feed II were added. When the internal temperature of 70 ° C. was reached, while stirring and maintaining the reaction temperature, starting simultaneously, the remainder of feed I and feed II were metered in continuously over two hours into the polymerization batch via two separate feeds. After the end of both feeds, the mixture was left to react for a further 15 minutes at the reaction temperature. 24 g of a 10% strength by weight aqueous solution of tert-butyl hydroperoxide and 34 g of a 12% strength by weight aqueous solution of acetone bisulfite (= addition product of Sodium bisulfite on acetone). The reaction mixture was then cooled to room temperature, adjusted to a pH of 8.4 using a 10% strength by weight aqueous solution of ammonia and filtered through a metal filter with a mesh size of 250 μm. A summary of the process parameters and the characterization of the copolymers obtained with regard to solids content FG and number-average particle diameter D _n can be found in Table 1. Inlet I: 448 g deionized water 40 g a 15% by weight aqueous solution of sodium lauryl sulfate 18.7 g a 45% by weight aqueous solution of Dowfax® 2A1 (trademark of Dow Chemical Company) 660 g n-butyl acrylate (monomer A) 504 g Styrene (monomer B) xg Monomer C 36 g Acrylic acid (monomer D) Inlet II: 4.7 g Sodium peroxodisulfate 62.2 g deionized water Summary representation of Examples 1 to 7 and the comparative example example Monomer C Quantity x [g] FG [% by weight] D _n [nm] Comparison - - 51.4 145 1 1,4-butanediol diacrylate 0.2 51.0 150 2 1,4-butanediol diacrylate 0.4 50.8 146 3rd 1,4-butanediol diacrylate 0.6 50.6 147 4th 1,4-butanediol diacrylate 1.4 50.6 145 5 1,4-butanediol dimethacrylate 0.4 50.5 146 6 Ethylene glycol dimethacrylate 0.4 50.4 148 7 1,4-divinylbenzene 0.4 50.7 141

2. General instructions for the production of the invention Paper coating slips

The paper coating slips of the invention were prepared by mixing the components listed in Table 2 in the order given there using a dissolver. The changing solids content of the copolymer dispersions used was taken into account in the amount used and was such that 10 parts by weight of copolymer (solid, based on 100 parts by weight of the total of the inorganic pigments) were present in the formulation. The pH of the paper coating slips was adjusted to 8.5 to 9 using a 10% strength by weight solution of sodium hydroxide. The solids content of the paper coating slip was then adjusted to 68% by weight by adding deionized water. Formulation of the paper coating slips according to the invention Parts by weight component Partial amount of the deionized water 0.4 the polysodium salt of a polyacrylic acid with a molecular weight of 4000 (polysalt from BASF AG) 0.5 Carboxymethyl cellulose 70 fine chalk 30th fine clay 10 Copolymer (calculated as solid) pH adjustment with 10% by weight solution of sodium hydroxide Residual amount of deionized water to adjust the solids content to 68% by weight

3. General regulations for paper coating

A wood-free coating base paper with a basis weight of 70 g / m ^{2 was} used as the base paper. The coating slip was applied to both sides with 10 g / m ² (calculated as a solid) on a laboratory coating machine (application method: roller, dosing method: blade).

The paper webs were made using an IR drying unit and Air drying dried (8 IR emitters with 650 watts each, Throughput speed 30 m / min).

The coated paper webs became 35 cm x 20 cm Cut test strips. The test strips were then stored 17 hours at 23 ° C and a relative humidity of 50% (DIN 50014-23 / 50-2). Following that were the test strips using the table laboratory calender K8 / 2, from the company Kleinewefers, Krefeld, at a temperature of 25 ° C calendered. The line pressure between the rollers was 200 kN / cm paper width and the speed 10 m / min. The The process was repeated four times.

4. Application tests

a) Determination of dry pick resistance with the IGT test printing device (IGT dry) The test strips were increasing in speed printed using the offset process. The maximum print speed was 200 cm / s. The paint was applied to one Line pressure of 350 N / cm. In the so-called point evaluation, from the first Pick point (i.e. the first tear from the paper coating slip) the tenth pick point is counted. The dry pick resistance is measured in cm / s, i.e. the tenth pick point given printing speed specified. The suitability of the copolymer as a binder in paper coating slips the better, ever higher this printing speed at the tenth pick point is.

b) Pick resistance with multiple printing (offset test) The test strips were printed with a constant Carried out speed of 1 m / s and took place at a line pressure of 200 N / cm. The printing process was repeated after 30 seconds. As Pick resistance indicates the number of passes until plucking occurs. The suitability of the copolymer the better as a binder in paper coating slips rated, the higher the number of printing processes until first plucking.

Results of the application tests example Monomer C Quantity x [g] IGT dry [cm / s] Offset test [number] Comparison - - 53 2nd 1 1,4-butanediol diacrylate 0.2 64 3rd 2nd 1,4-butanediol diacrylate 0.4 68 3rd 3rd 1,4-butanediol diacrylate 0.6 74 4th 4th 1,4-butanediol diacrylate 1.4 65 3rd 5 1,4-butanediol dimethacrylate 0.4 68 3rd 6 Ethylene glycol dimethacrylate 0.4 62 3rd 7 1,4-divinylbenzene 0.4 64 3rd

As can be seen from the result table 3, lead already small amounts of monomers C to a significant improvement in Dry pick resistance and pick resistance with multiple printing.

Claims (10)

Paper coating slip containing a copolymer as a binder, composed of 45 to 74.8% by weight at least one monomer, the homopolymer of which has a glass transition temperature <20 ° C. (monomers A), 25 to 54.8% by weight at least one monomer whose homopolymer has a glass transition temperature> 50 ° C (monomers B), 0.001 to 1.0% by weight at least one crosslinking monomer with at least two non-conjugated vinyl groups (monomers C), and optional 0 to 10% by weight at least one monomer containing acid groups (monomers D) and 0 to 10% by weight at least one further monomer (monomers E). Paper coating slip according to claim 1, characterized in that the monomer A is selected from at least one C _{1 to} C ₁₀ alkyl acrylate, C ₅ to C ₁₀ alkyl methacrylate, C ₅ to C ₁₀ cycloalkyl acrylate and methacrylate, Ci to C ₁₀ -dialkyl maleate and / or C ₁ - to C ₁₀ -dialkyl fumarate and the monomer B is selected from at least one vinyl aromatic monomer, a C ₁ - to C ₄ -alkyl methacrylate and / or an α, β-unsaturated carboxylic acid nitrile or dinitrile. Paper coating slip according to claim 1 or 2, characterized in that the copolymer contains 0.001 to 0.5% by weight of at least one monomer C in copolymerized form. Paper coating slip according to one of claims 1 to 3, characterized in that the copolymer contains 0.001 to 0.1% by weight of at least one monomer C in copolymerized form. Paper coating slip according to one of Claims 1 to 4, characterized in that the copolymer contains 0.5 to 5% by weight of at least one monomer D in copolymerized form. Paper coating slip according to one of claims 1 to 5, characterized in that the copolymer consists of particles whose number-average diameter is 50 to 300 nm. Paper coating slip according to one of claims 1 to 6, characterized in that the copolymer has a glass transition temperature of -40 to + 50 ° C. Paper coated with a paper coating slip according to one of claims 1 to 7. Method for printing on paper, characterized in that paper according to claim 8 is used for printing. Method according to claim 9, characterized in that it is an offset printing, gravure or flexographic printing process.