EP2118365A2

EP2118365A2 - Water-soluble binders for paper coating slips

Info

Publication number: EP2118365A2
Application number: EP08708608A
Authority: EP
Inventors: Robert Feuerhake; Dirk Lawrenz; Hans-Joachim HÄHNLE; Jürgen Schmidt-Thümmes
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2007-02-08
Filing date: 2008-02-04
Publication date: 2009-11-18
Also published as: CA2673457A1; US20100010153A1; CN101605940B; WO2008095878A2; CN101605940A; WO2008095878A3

Abstract

Disclosed are paper coating slips containing a) one or more binders, b) an optional thickener, c) an optional fluorescent or phosphorescent ink, particularly as an optical brightening agent, d) pigments or fillers, and e) additional auxiliary agents, e.g. auxiliary flowing agents or other inks. Said paper coating slips are characterized in that at least 40 percent by weight of the total amount of binders a) are provided in the form of a synthetic, water-soluble, anionic polymer while less than 50 percent by weight of the total amount of binders a) are provided in the form of emulsion polymers.

Description

Water-soluble binders for paper coating slips

description

The invention relates to paper coating compositions containing

a) one or more binders

b) optionally a thickener

c) optionally a fluorescence or phosphorescent dye, in particular as optical brightener

d) pigments or fillers

e) other auxiliaries, for. B. leveling agents or other dyes,

wherein at least 40% by weight of the total amount of the binders a) is a synthetic, water-soluble, anionic polymer (short anionic polymer) and less than 50% by weight of the total amount of the binders a) are emulsion polymers.

Paper coating slips usually contain polymeric binders and pigments, usually white pigments. With paper coating slips, base papers receive the desired mechanical and optical properties. The binder is intended to fix the pigments on the paper and to ensure cohesion in the resulting coating. The papers coated with the paper coating slips should in particular be printable.

When printing z. B. in an offset printing press, act due to the high viscosity of the ink strong tensile forces on the coated paper (paper coating). The resistance that the paper line exerts against these forces is called pick resistance. A distinction is made between dry picking strength and wet picking strength. The wet-rupture strength is particularly important in aqueous offset printing, as in the second printing unit, ink strikes a water-damp paper, and the paper coating must have sufficient binding force under these conditions.

As binders usually emulsion polymers are used. In addition to the pigments and emulsion polymers, paper coating slips may contain other constituents. It is known z. B. the concomitant use of additional binders, so-called co-binders. EP-A-19 170, EP-A 343 007, DE-A 103 42 517 and US 2005/0261394 describe water-soluble polymers as cobinders. However, the amount of cobinder is in each case significantly lower than that of the emulsion polymers. In addition, water-soluble polymers are also constituents of pigment-free compositions for further paper finishing. In WO 03/021041 z. B. describes the use of cationic polymers to increase the whiteness of paper

In the field of paper coating slips, there is generally a need for new, if appropriate also less expensive, binders which can optionally replace the emulsion polymers. However, the optical and mechanical properties of the coated papers should as far as possible not be impaired by the use of the novel binders.

The object of the invention was therefore new binders for paper coating slips.

According to the invention, the paper coating slip contains

a) one or more binders

b) optionally a thickener

d) pigments or fillers

e) other auxiliaries, for. B. flow control agents or other dyes.

To the anionic polymers as binders

An essential feature is that at least 40% by weight of the total amount of the binders a) is a synthetic, water-soluble, anionic polymer (short anionic polymer) and less than 50% by weight of the total amount of the binders a) are emulsion polymers is.

Anionic polymers are those which have attached to the polymer backbone anionic groups, eg. As carboxylate groups, phosphonate groups or sulfonate groups. The associated cation is z. B. a metal cation not bound to the polymer. The anionic polymer may also contain cationic groups attached to the polymer backbone, but overall the polymer is anionic, ie the anionic groups must predominate. The anionic polymer preferably contains at least 0.01 mol, particularly preferably at least 0.05 mol and very particularly preferably at least 0.1 mol of acid groups per 100 g of anionic polymer; the content of the acid groups is generally not greater than 1.4 mol, in particular not greater than 1.2 mol, or not greater than 1 mol of acid groups / 100 g of anionic polymer.

As acid groups come z. As sulfonic acid groups, Phosphonsäuregrupen or Carbonsäuregrupen into consideration. Preferred are carboxylic acid groups.

Preferably, at least 20 mol%, particularly preferably at least 40 mol%, very particularly preferably at least 60 mol%, in a particular embodiment, 100 mol% of the acid groups in anionic form, d. H. as a salt.

The cationic counterion to the anionic acid groups may be a monovalent or polyvalent, e.g. B. be two or trivalent counterion, preferably monovalent cationic counterions. In consideration come z. As the cations of the alkali metals, especially of sodium or potassium. Also suitable are nitrogen compounds, for. As the ammonium cation and its derivatives, preferred are the sodium and potassium cation.

The solubility of the anionic polymer in water is preferably greater than 50 g, particularly preferably greater than 100 g, very particularly preferably greater than 150 g of anionic polymer / 1 liter of water (21 ^° C., 1 bar).

As anionic polymer are any polymers, for. As polyadducts, polycondensates or polymers obtainable by free-radical polymerization into consideration.

The anionic polymers contain the acid or salt groups z. B. in that either a component already has these groups in the production or in that subsequent chemical transformations are carried out on the polymer.

The anionic polymer is preferably a polymer obtainable by free-radical polymerization of ethylenically unsaturated compounds (monomers).

The anionic polymer preferably contains the acid or salt groups by copolymerization with suitable monomers which contain such groups or contain groups which can be converted into such groups. Suitable monomers are monomers having an acid or salt group derived therefrom. In consideration but z. As well as monomers with an acid anhydride group, which can be easily converted later into acid groups and their salts, as a result, in the latter then after the conversion is also a monomer having an acid or salt group. Monomers having an acid or salt group are referred to hereinafter as acid monomers

In particular, it is at least 5 wt .-%, preferably at least 10 wt .-%, more preferably at least 20 wt .-% and most preferably at least 30 wt .-% of the monomers of which the anionic polymer is composed, to acid monomers.

Preferred acid monomers are, for. B. monomers having a carboxylic acid group, a sulfonic acid group or a phosphonic acid group; particularly preferred are monomers having a carboxylic acid group.

Called z. As acrylic acid, methacrylic acid, maleic acid or itaconic acid as monomers having a carboxylic acid group, and vinylphosphonic acid, acrylamidosulphonic acids, in particular acrylamido-2-methyl-propanesulfonic acid.

The anionic polymer may contain other monomers in addition to the acid monomers.

Suitable further monomers are monomers selected from C 1 -C 20 -alkyl (meth) acrylates, vinyl esters of carboxylic acids containing up to 20 carbon atoms, vinylaromatics having up to 20 carbon atoms, vinyl halides, aliphatic hydrocarbons having 2 to 8 carbon atoms and one or two double bonds, monomers containing ether groups, in particular vinyl ethers of alcohols containing 1 to 10 carbon atoms (short ether monomers) and monomers having at least one nitrogen atom in the molecule (short nitrogen monomers) or mixtures of these monomers.

As nitrogen monomers, in particular vinylcarboxamides may be mentioned. Preferred vinylcarboxamides are those of the formula (I):

In formula (I), R ¹ and R ² independently of one another are hydrogen or C ¹ to C 20 -alkyl, where the alkyl radical may be straight-chain or branched.

Preferably, R ¹ and R ^{2 are} independently hydrogen or C ¹ to C 10 alkyl, more preferably hydrogen or C ¹ to C ⁴ alkyl, most preferably hydrogen or methyl and especially hydrogen.

R ¹ and R ² can also together form a straight-chain or branched chain containing 2 to 8 carbon atoms, preferably a chain containing 3 to 6 and more preferably a chain containing 3 to 5 carbon atoms, so that a ring is formed. Optionally, one or more carbon atoms can be replaced by heteroatoms, such as. As oxygen, nitrogen or sulfur, be replaced.

Examples of the radicals R ¹ and R ² are methyl, ethyl, isopropyl, n-propyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-hexyl, n-heptyl, 2-ethylhexyl, n-octyl, n-decyl, n-undecyl, n-dodecyl, n-tetradecyl, n-hexadecyl, n-octadecyl or n-eicosyl.

Examples of radicals R ¹ and R ² which together form a chain are 1, 2-ethylene, 1, 2-propylene, 1, 3-propylene, 2-methyl-1, 3-propylene, 2-ethyl-1, 3-propylene, 1,4-butylene, 1,5-pentylene, 2-methyl-1,5-pentylene, 1,6-hexylene or 3-oxa-1,5-pentylene.

Examples of such N-vinylcarboxamides of the formula (I) are N-vinylformamide, N-vinylacetamide, N-vinylpropionamide, N-vinylbutyramide, N-vinylisobutyric acid amide, N-vinyl-2-ethylhexanoic acid amide, N-vinyldecanoic acid amide, N-vinyldodecanoic acid amide, N- Vinylstearic acid amide, N-methyl-N-vinylformamide, N-methyl-N-vinylacetamide, N-methyl-N-vinylpropionamide, N-methyl-N-vinylbutyramide, N-methyl-N-vinylisobutyric acid amide, N-methyl-N-vinyl 2-ethylhexanoic acid amide, N-methyl-N-vinyldecanoic acid amide, N-methyl-N-vinyldodecanoic acid amide, N-methyl-N-vinylstearamide, N-ethyl-N-vinylformamide, N-ethyl-N-vinylacetamide, N-ethyl-N- Vinylpropionic acid amide, N-ethyl-N-

Vinyl butyramide, N-ethyl-N-vinylisobutyric acid amide, N-ethyl-N-vinyl-2-ethylhexanoic acid amide, N-ethyl-N-vinyldecanoic acid amide, N-ethyl-N-vinyldodecanoic acid amide, N-ethyl-N-vinylstearic acid amide, N- iso-propyl-N-vinylformamide, N-iso-propyl-N-vinylacetamide, N-isopropyl-N-vinylpropionamide, N-isopropyl-N-vinylbutyramide, N-isopropyl-N-vinylisobutyric acid amide, N- iso-propyl-N-vinyl-2-ethylhexanoic acid amide, N-isopropyl-N-vinyldecanoic acid amide, N-isopropyl-N-vinyldodecanoic acid amide, N-isopropyl-N-vinylstearic acid amide, Nn-butyl-N-vinylformamide, Nn-butyl-N-vinylacetamide, Nn-butyl-N-vinylpropionamide, Nn-butyl-N-vinylbutyramide, Nn-butyl-N-vinylisobutyric acid amide, Nn-butyl-N-vinyl-2-ethylhexanoic acid amide, Nn-butyl-N- Vinyl decanoic acid amide, Nn-butyl-N-

Vinyldodecanoic acid amide, Nn-butyl-N-vinylstearic acid amide, N-vinylpyrrolidone or N- Vinylcaprolactam.

Preference is given to N-vinylformamide, N-vinylacetamide, N-methyl-N-vinylformamide, N-methyl-N-vinylacetamide, N-vinylpyrrolidone or N-vinylcaprolactam; N-vinylformamide (VFA) is particularly preferred.

The vinylcarboxamides can cleave carboxylic acid groups under hydrolysis conditions and are then present as vinylamines. Under appropriate pH conditions, amines form cationic groups. Cleavage of the carboxylic acid groups from the vinylcarboxamides is therefore not preferred in the context of this invention. Insofar as such cleavage occurs, the number of amino groups that are cationic or can be adjusted should be less than the number of anionic groups, more preferably less than half the number of anionic groups.

It is preferred that the vinylcarboxamides to more than 50 mol%, in particular more than 80 mol%, most preferably more than 95 mol%, or 100 mol% in the polymer as Vinylcarbonsäureamide, d. H. are copolymerized without cleavage of the carboxylic acid group

In addition to the vinylcarboxamides, methacrylamide and acrylamide are furthermore preferred as nitrogen monomers.

Also preferred is vinylimidazole.

Preference is given to anionic polymers which contain, in addition to acid monomers (ether monomers) and / or or (nitrogen monomers).

Particularly preferred are nitrogen monomers, very particularly preferred are vinylcarboxamides, in particular vinylformamide, and also (meth) acrylamide or vinylimidazole.

In particular, nitrogen monomers selected from vinylformamide or (meth) acrylamide or vinylimidazole may be mentioned.

Vinylformamide is most preferred.

The anionic polymers may consist exclusively of the acid monomers, preference being given to anionic polymers which, in addition to the acid monomers, comprise at least 5% by weight of further monomers selected from monomers having at least at least one ether group (ether monomers) or monomers having at least one nitrogen atom (nitrogen monomers) are constructed

The anionic polymers are particularly preferably made up of

From 5 to 95% by weight of acid monomers

From 5 to 95% by weight of further monomers, in particular nitrogen monomers

0 to 30 wt .-% auxiliary monomers.

Most preferably, the anionic polymers are composed of

15 to 85% by weight of acid monomers

15 to 85 wt .-% further monomers, in particular nitrogen monomers 0 to 20 wt .-% auxiliary monomers.

In a particular embodiment, the anionic polymers consist of

From 25 to 75% by weight of acid monomers

From 25 to 75% by weight of further monomers, in particular nitrogen monomers from 0 to 20% by weight of auxiliary monomers.

In a very particular embodiment, the anionic polymers consist of

35 to 65% by weight of acid monomers 35 to 65% by weight of further monomers, in particular nitrogen monomers 0 to 20% by weight of auxiliary monomers.

The proportion of the auxiliary monomers in the above compositions may also be 0 to 10% by weight, in particular 0 to 5% by weight, or 0% by weight.

The preparation of the anionic polymers is known to the person skilled in the art; in particular, it can be carried out by solution polymerization in water.

The production is z. B. also described in WO 03/021041.

The polymerization temperatures are usually in the range of 30 to 200, preferably 40 to 110, particularly preferably 40 to 100 ⁰ C, optionally at reduced or elevated pressure. Suitable initiators are, for example, azo and peroxy compounds and the usual redox initiator systems, such as combinations of hydrogen peroxide and reducing compounds, for. Sodium sulfite, sodium bisulfite, sodium formaldehyde sulfoxilate and hydrazine. These systems can optionally additionally contain small amounts of a heavy metal salt.

The anionic polymers are preferably prepared by solution polymerization in water. The polymerization initiator used is preferably water-soluble azo compounds, such as 2,2'-azobis (2-methylpropionamidine) dihydrochloride, 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis ( 2-methyl-N-phenylpropionamidine) dihydrochloride, 2,2'-azobis (isobutyronitrile), 2,2'-azobis (2-amidinopropane) hydrochloride or 4,4'-azobis (4'-bis (isobutyronitrile) cyanopentanoic acid).

The amount of initiators is generally from 0.1 to 10 wt .-%, preferably 0.5 to 5 wt .-%, based on the (co) polymerizing monomers. It is also possible to use a plurality of different initiators in (co) polymerization.

As a solvent or diluent for the polymerization z. For example, water, alcohols, such as methanol, ethanol, n- or iso-propanol, n- or iso-butanol, or ketones, such as acetone, ethyl methyl ketone, diethyl ketone or isobutyl methyl ketone.

To produce low molecular weight polymers, the polymerization can be carried out in the presence of a regulator. Suitable regulators are, for example, secondary alcohols, such as isopropanol and sec-butanol, hydroxylamine, formic acid and mercapto compounds, such as mercaptoethanol, mercaptopropanol, mercaptobutanol, thioglycolic acid, thiolactic acid, tert-butylmercaptan, octylmercaptan and dodecylmercaptan. The regulators are usually used in amounts of 0.01 to 5 wt .-%, based on the monomers used. If secondary alcohols are used as regulators, the (co) polymerization can also be carried out in the presence of substantially larger amounts, e.g. in amounts up to 80 wt .-%, based on the monomers. In these cases, the secondary alcohols are also solvents for the monomers.

The polymers obtainable in this way generally have K values of 20 to 300, preferably 50 to 250. The K values indicated in this document are determined according to H.Fikentscher in 5% strength aqueous sodium chloride solution at pH 7.25 ° C. and a polymer concentration of 0.1% by weight.

The pH of the resulting aqueous solution or later the paper coating slip is preferably adjusted to values of 6 to 10, in particular 7 to 9. The acid groups are then present as salt groups. To the binders in total

In addition to the anionic polymer, the paper stock may contain other binders.

Particularly suitable are emulsion polymers or natural binders such as starch.

Suitable and commonly used emulsion polymers are preferably at least 40% by weight, preferably at least 60% by weight, particularly preferably at least 80% by weight, of so-called main monomers.

The main monomers are selected from C 1 -C 20 -alkyl (meth) acrylates, vinyl esters of carboxylic acids containing up to 20 carbon atoms, vinylaromatics having up to 20 carbon atoms, ethylenically unsaturated nitriles, vinyl halides, vinyl ethers having from 1 to 10 carbon atoms Alcohols, aliphatic hydrocarbons having 2 to 8 carbon atoms and one or two double bonds or mixtures of these monomers.

To name a few are z. B. (meth) acrylic acid alkyl ester having a Ci-Cio-alkyl radical, such as methyl methacrylate, methyl acrylate, n-butyl acrylate, ethyl acrylate and 2-ethylhexyl acrylate.

In particular, mixtures of (meth) acrylic acid alkyl esters are also suitable.

Vinyl esters of carboxylic acids having 1 to 20 carbon atoms are, for. As vinyl laurate, stearate, vinyl propionate, vinyl versatate and vinyl acetate.

Suitable vinylaromatic compounds are vinyltoluene, α- and p-methylstyrene, α-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene and preferably styrene. Examples of nitriles are acrylonitrile and methacrylonitrile.

The vinyl halides are chloro, fluoro or bromo substituted ethylenically unsaturated compounds, preferably vinyl chloride and vinylidene chloride.

To name as vinyl ethers are, for. As vinyl methyl ether or vinyl isobutyl ether. Vinyl ether is preferably from 1 to 4 C-containing alcohols.

As hydrocarbons having 2 to 8 carbon atoms and one or two olefinic double bonds may be mentioned ethylene, propylene, butadiene, isoprene and chloroprene.

Preferred main monomers are C 1 -C 10 -alkyl (meth) acrylates and mixtures of the alkyl (meth) acrylates with vinylaromatics, in particular styrene, or hydrocarbons with 2 double bonds, in particular butadiene, or mixtures of such hydrocarbons with vinyl aromatics, in particular styrene.

For mixtures of aliphatic hydrocarbons (especially butadiene) with vinyl aromatics (especially styrene), the ratio z. B. between 10:90 to 90:10, in particular 20:80 to 80:20.

Particularly preferred major monomers are butadiene and the above mixtures of butadiene and styrene.

In addition to the main monomers, the polymer may contain other monomers, for. As monomers with carboxylic acid, sulfonic acid or phosphonic acid groups. Preferred are carboxylic acid groups. Called z. For example, acrylic acid, methacrylic acid, itaconic acid, maleic acid or fumaric acid. The content of ethylenically unsaturated acids in the emulsion polymer is generally less than 5 wt .-%.

Other monomers are z. As well as hydroxyl-containing monomers, in particular Ci-Cio-hydroxyalkyl (meth) acrylates, or amides such as (meth) acrylamide.

The polymers are prepared by emulsion polymerization, which is therefore an emulsion polymer.

An essential feature of the present invention is that emusional polymers are not required as binders and can be replaced by the anionic polymers.

It is therefore preferable that less than 30% by weight, more preferably less than 20% by weight, particularly preferably less than 10% by weight, of the binders a) are emulsion polymers.

In a particular embodiment, the paper coating composition contains no emulsion polymers.

Natural binders such as starch can also be used, but are not absolutely necessary.

Strength in this context should be understood as meaning any native, modified or degraded starch. Native starches may consist of amylose, amylopectin or mixtures thereof. Modified starches may be oxidized starch, starch esters or starch ethers. Hydrolysis can reduce the molecular weight of the starch (degraded starch). The degradation products are oligosaccharides or dextrins into consideration.

Preferred starches are corn, corn and potato starch. Particularly preferred are corn and corn starch, most preferably cereal starch.

Preferably, the proportion of the anionic polymer to the binders a) at least 50 wt .-%, more preferably at least 60 wt .-% and in particular at least 70 wt .-% (solid, ie without water or other at 21 ⁰ C, 1 bar liquid solvents).

In a particular embodiment, the proportion of the anionic polymer in the binders a) is at least 80 wt .-% or 95 wt .-%. In particular, the binders a) may also be exclusively the anionic polymer.

The amount of the binder a) in total is preferably 1 to 50 parts by weight, more preferably 1 to 20 parts by weight per 100 parts by weight of pigment or filler (solid, ie without water or other at 21 ⁰ C, 1 bar of liquid solvent). An advantage of the invention is that the proportion of binder can be reduced overall, so the amount of the binder a) in particular less than 10, even less than 8 or less than 7 parts by weight per 100 parts by weight of pigment or Filler be, at least it is generally 1 or 2 parts by weight per 100 parts by weight of pigment or filler, (all data are based on solids, ie without water or other at 21 ⁰ C, 1 bar liquid solvents).

To the other components of the paper coating

Suitable thickeners b) are, in addition to synthetic polymers, in particular cellulose, preferably carboxymethylcellulose.

Conventional fluorescence or phosphorescence dyes are in particular stilbenes, they act as optical brighteners.

The pigment or filler d) is generally inorganic solids, in particular white pigments, for. As barium sulfate, calcium carbonate, calcium sulfoaluminate, kaolin, talc, titanium dioxide, zinc oxide, chalk or coating Clay.

It is preferably an aqueous paper coating slip; in particular, it already contains water by the formulation of the constituents (aqueous solution). solution of the anionic polymer, aqueous pigment slurries); the desired viscosity can be adjusted by adding more water.

Typical solids contents of the paper coating slips are in the range of 30 to 60 wt .-%.

Manufacture and use

The preparation of the paper coating slip can be done by conventional methods.

The ingredients are combined and mixed in the usual way.

The paper coating slip is preferably applied to uncoated base papers or uncoated cardboard.

The amount is generally 1 to 50 g, preferably 5 to 30 g (solid, ie without water or other at 21 ⁰ C, 1 bar liquid solvent) per square meter.

The coating can be carried out by conventional application methods, also by curtain coating (curtain coating).

The coated papers and cardboard have good performance properties, in particular a high gloss and a good pick resistance. They are well printable in the usual printing processes, such as high, low and offset printing. The

Total amount of binder can be reduced. There are also fewer thickeners or other Cobinder needed. Even without thickener, the water retention of the paper coating slips is very good.

Examples

Preparation of water-soluble anionic polymers

Abbreviations: N-vinylformamide: VFA

Acrylic acid: AS

Acrylamide: AM

Maleic acid: MS

2,2'-azobis (2-methylpropionamide) dihydrochloride: Wako V 50 The K values were determined according to H. Fikentscher, Cellulose Chemistry, Volume 13, 58-64 and 71-74 (1932) as a 0.1% solution in 5% sodium chloride solution.

The data in% are in wt .-%.

Unless otherwise stated, the solutions are aqueous solutions.

Example 1: VFA: AS = 40:60 (mol%)

Original: 574.8 g of deionised water

1.9 g of phosphoric acid (75%) 3.3 g of sodium hydroxide solution (25%)

Feed 1: 300.00 g demineralized water 400.3 g sodium acrylate solution (32%)

65.2 g VFA (99%)

Feed 2: 68.4 g Wako V 50 solution (1%)

Feed 3: 16.3 g Wako V 50 solution (1%)

Feed 4: 370.0 g of deionised water

Before the reaction, the pH of template and feed 1 are adjusted to 6.5. The original is heated to 76 ^° C. in a 2 L reactor. Then, a vacuum of about 357 mbar is applied to the reaction vessel. At this temperature, feeds 1 and 2 are started simultaneously, feed 1 is added within two hours and feed 2 is added within three hours. After a total of five hours, feed 3 is added within 5 minutes and polymerized for a further two hours.

This gives a clear solution with a solids content of 12.65%. The K value is 107.1.

Example 2: VFA: AS = 60:40 (mol%)

Original: 887.6 g of deionised water

4.3 g phosphoric acid (85%) 6.0 g NaOH (25%)

Feed 1: 571.0 g of sodium acrylate solution (38%) Feed 2: 248.7 g VFA (99%)

Feed 3: 8.24 g Wako V-50 74.2 g deionized water

Before the reaction, the pH of template and feed 1 are adjusted to 6.5. The initial charge is heated to 78 ^° C. in a 2 l reactor under nitrogen. Runs 1-3 are added in parallel within two hours. To complete the reaction is stirred for three hours.

A clear solution having a solids content of 27.68% is obtained. The K value is 53.3.

Example 3: VFA: AS = 50:50

Original: 524.5 g of deionised water

3.8 g of phosphoric acid (75%)

7.4 g sodium hydroxide solution (25%)

Feed 1: 705.1 g sodium acrylate solution (32%) 172.4 g VFA (99%)

Feed 2: 4.3 g Wako V 50 81, 7 g deionized water

Before the reaction, the pH of template and feed 1 are adjusted to 6.5. The original is heated to 74 ^° C. in a 2 l reactor under nitrogen. Inlets 1 and 2 are added at the same time. Feed 1 is metered in within two hours, feed 2 within three hours. To complete the reaction is then stirred for another three hours. Subsequently, 200 g of water are added and distilled off again under vacuum.

This gives a clear solution with a solids content of 27.80%. The K value is 82.6.

Example 4: VFA: AS = 70:30 (mol%)

Original: 906.1 g of deionised water

4.3 g phosphoric acid (85%) 6.0 g sodium hydroxide solution (25%)

Feed 1: 428.2 g of sodium acrylate solution (38%) Feed 2: 290.1 g VFA (99%)

Feed 3: 8.24 g Wako V 50 74.2 g deionized water

Before the reaction, the pH of template and feed 1 are adjusted to 6.5. The initial charge is heated to 75 ^° C. in a 2 L reactor under nitrogen. Inlets 1 and 2 are started at the same time. Feeds 1 and 2 are metered in within 2 hours, feed 3 within 2.5 hours. To complete the reaction is then stirred for a further 3 hours.

This gives a clear solution with a solids content of 27.85%. The K value is 62.9.

Example 5: VFA: AS = 70:30 (mol%)

Template: 803.00 g deionised water

5.10 g phosphoric acid (75%) 7.6 g sodium hydroxide solution (25%)

Feed 1: 274.75 g DI water 161, 90 g acrylic acid 172.00 g sodium hydroxide solution (50%) 376.90 g VFA

Feed 2: 75.00 g deionised water

16.10 g hypophosphorous acid (50%)

10.50 g sodium hydroxide solution (50%)

Feed 3: 5.35 g Wako V 50 60.00 g deionised water

Before the reaction, the pH of template and feeds 1 and 2 are adjusted to 6.5. The initial charge is heated to 76 ^° C. in a 2 L reactor under nitrogen. At this temperature, the feeds are added in parallel, feed 1 and feed 2 in two hours, and feed 3 added within three hours. The mixture is then polymerized for a further two hours. This gives a clear solution with a solids content of 33.5%. The K value is 37.5. Example 6: VFA: AS = 30:70 (mol%)

Template: 425.00 g of deionised water

4.5 g phosphoric acid (85%) 8.2 g NaOH (25%)

Feed 1: 540.00 g demineralized water 244.85 g acrylic acid 277.00 g sodium hydroxide solution (50%) 105.0 g of VFA

Feed 2: 4.20 g Wako V 50

100.00 g of deionised water

Original adjusted to pH 6.5 (+ -0.3). Under nitrogen gassing heated to 80 ⁰ C. At 80 ⁰ C feed 1 in 2 hours, feed 2 added in 3 hours. Post-polymerized for 3 hours at 80 ⁰ C.

Example 7: VFA / AS 40:60 mol%

The preparation was carried out in a 4 liter stirred vessel.

Procedure:

Template at 74 ⁰ C to heat, gentle reflux (distilled off at 380 mbar)

Start feed 1 + 2. Feed feed 1 in 2 h and feed 2 in 3h evenly. To

Inlet 2 end stirring for another 2h.

Then add feed 3 in 5 min.

Postpolymerize for 2 hours.

Cool and dilute with feed 4.

Distill 330 g during the entire run time.

The preparation was carried out according to the above procedure, the solids content of the resulting solution was 12.5 wt .-%, the K value of 104. The acid groups are present as a salt (sodium acrylate).

Production of paper coating slips

Paper coatings were prepared by stirring the following aqueous components:

Hydrocarb ^® 90-Me aqueous slurry (calcium carbonate from Omya)

Sterocoll ^® FD (commercial thickener)

Styronal D 537 commercial binder for paper coating slips, emulsion polymer based on butadiene and styrene

Anionic polymer from Example 7

The amounts are given in Table 1.

The solids content was adjusted to 52% by weight with water and the pH was between 8.5 and 8.7. The Brookfield viscosity was measured with a No. 4 spindle at 23 ^° C. and two different revolutions (20 and 100 rpm).

The water retention was determined according to Gradek. Good water retention is very important for processing a paper coating on large and fast-running paper coating equipment. For testing, an aqueous paper coating slip is brought into contact with a filter paper layer and gravimetrically It is correct how much water is absorbed by the filter paper layer. The more recorded, the worse the water retention of the paper coating slip, the amount recorded is in g / square meter.

Table 1: Composition of the coating colors S1 to S 6

The figures are parts by weight, fixed (ie without water)

Application testing

The base paper used was a wood-free coating paper with a grammage of 70 g / m 2. The application of the paper coating slip took place on one side with 10 g / m 2 on a laboratory coater. The drying took place with an IR emitter. The papers passed a laboratory calender four times before the performance tests (one roller pair, line pressure: 2000 N / cm).

dry pick

From the papers to be tested strips were cut in the size 33 x 3 cm in the longitudinal direction and these strips stored for 15 hours at 27 ⁰ C with a relative humidity of 50% in the air conditioning room.

The strips were then printed in a printing unit (IGT printability tester AC2 / AIC2) with a standard color (printing ink 3808 from Lorilleux-Lefranc). prints.

The test strips are fed through the printing unit at a continuously increasing speed (maximum speed 200 cm / sec). As a measure of the dry plucking strength, the speed is given in cm / sec at which 10 out breaks from the paper coating slip (picking points) took place after the start of printing.

offset test

Paper:

From the papers to be tested, samples having a size of 240 x 46 mm are cut out in the longitudinal direction.

Carrying out the test: An appropriate amount of the printing ink is added to the inking roller and allowed to run for 1 min. Then a pressure washer is used and colored for 30 s.

The printing speed is 1 m / s. A strip of paper is returned to a print sample carrier with the printed paper strip in the starting position. After a specified period of time, the printing process is restarted without replacing the pressure disk. This process is repeated several times.

After each pass, the plucking on the printed side of the paper strip is visually inspected. The number of passes is indicated until the first time a pluck occurs.

Specification of the result:

Number of prints until the first picking occurs.

Thickener was used only in S1 (see above). Without thickener, the paper slips S2 to S6 achieve values which are just as good and, with a higher proportion of the anionic polymers, better values than paper slips based on emulsion prepolymers.

Claims

1. Paper coating slips containing

a) one or more binders

b) optionally a thickener

d) pigments or fillers

e) other auxiliaries, for. B. leveling agents or other dyes,

characterized in that at least 40% by weight of the total amount of the binders a) is a synthetic, water-soluble, anionic polymer (short anionic polymer) and less than 50% by weight of the total amount of the binders a) Emulsion polymers is.

2. paper coating slip according to claim 1, characterized in that the anionic polymer is at least 0.01 mol of acid groups per 100 g of anionic

Contains polymer and at least 20 mol% of the acid groups are present as a salt.

3. paper coating slip according to claim 1 or 2, characterized in that the solubility of the anionic polymer in water is greater than 50 g polymer / 1 liter of water (21 ⁰ C, 1 bar).

4. paper coating slip according to one of claims 1 to 3, characterized in that it is the anionic polymer is a polymer obtainable by radical polymerization ethylenically unsaturated compounds (monomers).

5. paper coating slip according to one of claims 1 to 4, characterized in that it is at least 10 wt .-% of the monomers of which the anionic polymer is composed of monomers containing acid or salt groups (short acid monomers).

6. paper coating slip according to one of claims 1 to 5, characterized in that it is the acid monomers to acrylic acid, methacrylic acid, maleic acid or itaconic acid.

7. paper coating slip according to one of claims 1 to 6, characterized in that the anionic polymer in addition to at least 5 wt .-% is made up of further monomers selected from monomers having at least one ether group (ether monomers) or monomers having at least one nitrogen atom (nitrogen monomers).

8. Paper coating slip according to one of claims 1 to 7, characterized in that it is the vinyl monomers, vinyl formamide, (meth) acrylamide, vinyl pyrrolidone or vinyl imidazole.

9. paper coating slip according to one of claims 1 to 8, characterized in that it is composed of a polymer of the anionic polymer

5 to 95% by weight of acid monomers 5 to 95% by weight of nitrogen monomers 0 to 30% by weight of auxiliary monomers

is.

10. Paper coating compositions according to any one of claims 1 to 9, characterized in that it is more than 60 wt .-% of the binder a) is an anionic polymer.

1 1. Paper coating compositions according to any one of claims 1 to 10, characterized in that it is less than 20 wt .-% of the binder a) emulsion polymers.

12. Paper coating compositions according to any one of claims 1 to 11, characterized in that they contain no emulsion polymers as binders.

13. Paper coating compositions according to any one of claims 1 to 12, characterized in that the amount of the binder a) 1 to 50 parts by weight per 100 parts by weight of pigments or fillers d).

14. Use of the paper coating slip according to one of claims 1 to 13 for coating paper (base paper) or cardboard.

15. With a paper coating composition according to any one of claims 1 to 13 coated papers or cartons.