WO2007033930A1

WO2007033930A1 - Paper coating materials comprising terpinolene-containing binder for curtain coating processes

Info

Publication number: WO2007033930A1
Application number: PCT/EP2006/066340
Authority: WO
Inventors: Oliver Birkert; Christoph Hamers; Erich Krumbacher; Martin Schachtl
Original assignee: Basf Se
Priority date: 2005-09-22
Filing date: 2006-09-14
Publication date: 2007-03-29
Also published as: DE102005045444A1; DE112006002316A5

Abstract

Disclosed is a method for coating substrates with paper coating materials. Said method is characterized in that the coating process is performed using curtain coating while the paper coating material contains an aqueous polymer dispersion as a binder, said aqueous dispersion being obtained by emulsion-polymerizing radically unsaturated compounds (monomers) in the presence of at least two different polymerization regulators A) and B). A) represents a compound selected among hydrocarbons which form a pentadienyl radical or 1-phenyl allyl radical when a hydrogen atom is abstracted while B) represents a compound comprising a mercapto group. A) amounts to 0.01 to 1 parts by weight while B) amounts to more than 0.1 parts by weight per 100 parts by weight of monomers.

Description

Paper coating slips with terpinolene-containing binder for curtain coating

description

The invention relates to a method for coating substrates with paper coating slips, characterized in that

the coating is carried out by the curtain coating method, the paper coating slip contains an aqueous dispersion of a polymer as binder and this aqueous dispersion is obtainable by emulsion polymerization of free-radically unsaturated compounds (monomers) in the presence of at least two different polymerization regulators A) and B) , where it is

A) a compound selected from hydrocarbons which form a pentadienyl or 1-phenylallyl radical upon abstraction of a hydrogen atom and B) a compound having a mercapto group

and the amount of A) is 0.01 to 1 part by weight and B) more than 0.1 part by weight to 100 parts by weight of monomers. Furthermore, the invention relates to dispersions which are suitable for such a process.

The curtain coating method is a coating method known from the prior art, in which the mass to be coated is coated continuously as a freely falling curtain on a web-shaped carrier. This coating method offers the particular advantage that high coating speeds are possible, but the coatings obtained at the same time have a high quality. For high coating qualities, however, it is necessary that the compositions of the coating compositions are adapted to the requirements of the process.

From the German patent applications DE-A-102004045172.9 and DE-A-

102004045171.0 and J P-A-2004124312 disclose paper coating slips for the curtain coating process.

Paper coating slips are coating compositions which contain as essential constituents binders and pigments. Papers and paperboard are generally coated with such paper coating slips to improve their printability and optical properties such as gloss, whiteness and opacity. The binder in the paper coating slips serves to anchor the individual pigment particles to one another and to the paper surface and thus to form a closed pigment layer. An important property is in particular the stability of the coating against mechanical stresses. Especially in offset printing must a high mechanical stability can be ensured, since the surface is subjected to mechanical stress due to the tack of the printing inks used. Due to the wiping water used in offset printing, this mechanical strength must be guaranteed even when wet. The mechanical resilience of a paper coating is also referred to as pick resistance, the mechanical load capacity in the wet state also as wet pick resistance.

The Rupffestigkeit of the coated papers achieved so far in curtain coating is not yet sufficient.

Paper coating slips containing styrene / butadiene copolymers as binders z. From DE-A-10046930, DE-A-10148497, DE-A-10148494, DE-A-10148496, DE-A-1014851 1 and EP-A-496925. In particular in the above EP-A-496925 and DE-A-10046930, mixtures of terpinols and mercapto-group-containing regulators are used in the preparation of the copolymer by emulsion polymerization. The amount of the mercapto-group-containing regulator amounts to a maximum of 2 parts by weight per 100 parts by weight of polymer.

The present invention is therefore based on the object of providing paper coating slips which can be coated well in a curtain coating process and which, in the case of this coating process, give papers having good performance properties, in particular a high pick resistance.

Accordingly, the method defined above was found. Polymer dispersions and paper coating slips which are suitable for these processes have also been found.

The aqueous dispersion of the polymer is available by emulsion polymerization and is preferably prepared by emulsion polymerization.

The following information on the amount of monomers relate both to the amounts used in the polymerization and, correspondingly, to the content of the monomers in the polymer (in copolymerized form).

At least 40% by weight, preferably at least 60% by weight, particularly preferably at least 80% by weight of the monomers are the following main monomers, ie. Accordingly, main monomers are used in these amounts in the emulsion polymerization. In the resulting emulsion polymer, the main monomers are then contained in the appropriate amount.

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, Atoms, ethylenically unsaturated nitriles, vinyl halides, vinyl ethers of alcohols containing 1 to 10 carbon atoms, aliphatic hydrocarbons having 2 to 8 carbon atoms and one or two double bonds or mixtures of these monomers.

These include, for example, (Meth) acrylic acid alkyl esters 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 e.g. 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 (short (meth) acrylonitrile).

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

As vinyl ethers, there are e.g. 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, vinylaromatics, in particular styrene, hydrocarbons having 2 double bonds, in particular butadiene, ethylenically unsaturated nitriles, in particular (meth) acrylonitrile and any desired mixtures of these main monomers.

Particular preference is given to mixtures of main monomers which necessarily contain aliphatic hydrocarbons having 2 double bonds, in particular butadiene. The content of such monomers is preferably at least 10, preferably at least 30, particularly preferably at least 40,% by weight, based on the total sum of all monomers.

Particularly suitable are mixtures of aliphatic hydrocarbons having 2 double bonds (in particular butadiene) and vinylaromatics (in particular styrene), mixtures of aliphatic hydrocarbons having 2 double bonds (in particular butadiene) with (meth) acrylonitrile) or mixtures of aliphatic hydrocarbons having 2 double bonds (in particular butadiene) ) with vinyl aromatics (styrene) and meth (acrylonitrile). For the mixtures, the weight ratio of aliphatic hydrocarbons (in particular butadiene) to the total of vinyl aromatics (in particular styrene) and (meth) acrylonitrile in particular 10:90 to 90:10, in particular 20:80 to 80:20.

In addition to the major monomers, the polymer may contain other monomers, e.g. Monomers with carboxylic acid, sulfonic acid or phosphonic acid groups. Preferred are carboxylic acid groups. Called e.g. Acrylic acid, methacrylic acid, itaconic acid, maleic acid or fumaric acid or mixtures of these monomers; In particular, mixtures of itaconic acid and (meth) acrylic acid are suitable. Such monomers with acid groups, in particular carboxylic acid groups, can be present in the polymer in particular in amounts of from 0.05 to 10% by weight.

Other monomers are e.g. also hydroxyl-containing monomers, in particular Ci-Cio-hydroxyalkyl (meth) acrylates, or amides such as (meth) acrylamide.

In a preferred embodiment, the polymer contains at least 0.1% by weight, in particular at least 0.3% by weight, of further monomers, in particular monomers with acid groups (see above).

The proportion of the further monomers is generally less than 20% by weight, in particular less than 10% by weight.

All wt.% Information is based on the polymer.

Preferred polymers are composed of:

10 to 100% by weight of butadiene

10 to 70% by weight of styrene

0 to 30% by weight of C1 to C20 alkyl (meth) acrylates 0 to 20% by weight of (meth) acrylonitrile

0 to 20% by weight of other monomers

The polymers are produced in a preferred embodiment by emulsion polymerization, which is therefore an emulsion polymer.

However, the preparation may be e.g. also by solution polymerization and subsequent dispersion in water.

In the emulsion polymerization, ionic and / or nonionic emulsifiers and / or protective colloids or stabilizers are used as surface-active compounds, preferably emulsifiers are used. The surface-active substance is usually used in amounts of from 0.1 to 40% by weight, preferably in amounts of from 0.1 to 10% by weight, based on the monomers to be polymerized.

Water-soluble initiators for emulsion polymerization are e.g. Ammonium and alkali metal salts of peroxodisulfuric acid, e.g. Sodium peroxodisulfate, hydrogen peroxide or organic peroxides, e.g. tert-butyl hydroperoxide.

Also suitable are so-called reduction-oxidation (red-ox) -lititiator systems.

The amount of initiators is generally 0.1 to 10 wt .-%, preferably 0.5 to 5 wt .-%, based on the monomers to be polymerized. It is also possible to use a plurality of different initiators in the emulsion polymerization.

The emulsion polymerization is generally carried out at 30 to 130, preferably 50 to 100 ⁰ C. The polymerization medium can consist of water only, as well as mixtures of water and thus miscible liquids such as methanol. Preferably, only water is used. The emulsion polymerization can be carried out both as a batch process and in the form of a feed process, including a stepwise or gradient procedure. Preferably, the feed process, in which one submits a portion of the polymerization, heated to an elevated temperature, polymerized and then the remainder of the polymerization mixture, usually via a plurality of spatially separate feeds, one or more of which contain the monomers in pure or in emulsified form, continuous, stepwise or with the addition of a concentration gradient while maintaining the polymerization of the polymerization zone supplies. In the polymerization, it is also possible, for example for the purpose of better adjustment of the particle size, to introduce a polymer seed.

The manner in which the initiator is added to the polymerization vessel in the course of the free radical aqueous emulsion polymerization is known to one of ordinary skill in the art. It can be introduced both completely into the polymerization vessel, or used continuously or in stages according to its consumption in the course of the free radical aqueous emulsion polymerization. In particular, this depends on the chemical nature of the initiator system as well as on the polymerization temperature. Preferably, a part is initially charged and the remainder supplied according to the consumption of the polymerization.

The same applies to the polymerization regulators A) and B); they can be presented in the polymerization or during the polymerization, for. B. continuous loan or in individual portions, are fed; A combination of these measures is also possible, a preferred embodiment being that described in DE-A-10046930. To remove the residual monomers is usually after the end of the actual emulsion polymerization, ie added after a conversion of the monomers of at least 95%, initiator.

The individual components can be added to the reactor in the feed process from above, in the side or from below through the reactor bottom.

In the emulsion polymerization, aqueous dispersions of the polymer are generally obtained with solids contents of 15 to 75 wt .-%, preferably from 40 to 75 wt .-%.

The polymers obtainable by the process according to the invention generally have a weight-average particle diameter below 1000 nm. The dw value of the particle size is defined as usual as the weight average particle size as determined by means of an analytical ultracentrifuge according to the method of W. Scholtan and H. Lange, Kolloid-Z. and Z.-Polymere 250 (1972) pages 782 to 796. Ultracentrifuge measurement provides the integral mass distribution of the particle diameter of a sample. From this it can be seen how many percent by weight of the particles have a diameter equal to or below a certain size.

In the context of the present invention, the weight-average particle diameter is preferably less than 150 nm, in particular less than 130 nm, particularly preferably less than 120 nm and very particularly preferably less than 100 nm and in a particularly preferred embodiment less than 90 nm; it is preferably greater than 40 nm or greater than 60 nm.

Methods for adjusting the polymer particle size of an aqueous polymer dispersion are known from the prior art. Preferably, the emulsion polymerization is carried out to adjust a defined polymer particle size by the seed latex method or in the presence of a seed latex prepared in situ. Methods for this are known and can be taken from the prior art (see EP-B 40419 and Εncyclopedia of Polymer Science and Technology ', Vol. 5, John Wiley & Sons Inc., New York 1966, p. 847).

The emulsion is carried out according to the invention in the presence of at least two different polymerization regulators A) and B).

Regulator A) is selected from the group of hydrocarbon compounds comprising Compounds that form a pentadienyl or 1-phenylallyl radical upon abstraction of a hydrogen atom. These are compounds which either have a 1, 4 pentadiene structure of the formula A1) with one or two hydrogen atoms on the C3 atom (average C atom in the formula below)

or a 1, 3 pentadiene structure of the formula A2) having one or two hydrogen atoms on the C5 atom (last C atom in the formula below)

have, wherein one of the double bonds may also be part of a phenyl ring. In the structures A1 and A2, the vertical bars indicate open valences without, however, providing any information about the stereochemistry of the double bonds. The open valences may be saturated with hydrogen, an alkyl group or a phenyl group, or any two open valencies may form a 5- or 6-membered carbocycle. Valences on two carbon atoms linked together via a double bond together with the carbon atoms of the double bond may represent a phenyl ring.

Examples of compounds of the formula A1) are 1, 4 dihydrobenzene, γ-terpinene, terpinene nolenium and norbornadiene α lonone. Examples of compounds of the formula A29 are 1,3-cyclohexadiene, α-terpinene and α-phellandrene.

Preferred compounds A) are compounds of the formula A1). Particular preference is given to terpinolene ((4- (2-propylidene) -1-methylcyclohex-1-ene). Terpinolene has the formula:

The amount of regulator A) in the process according to the invention is from 0.01 to 1 parts by weight per 100 parts by weight of monomers; more preferably, the amount is at least 0.02 parts by weight, most preferably at least 0.05 parts by weight, it is preferably at most 0.4 parts by weight. The amount of regulator A) in a preferred embodiment is 0.02 to 0.4 and in a most preferred embodiment 0.05 to 0.3 parts by weight.

Regulator B) is a compound with a mercapto group (SH group). Preferred regulators B), apart from the SH group, consist only of carbon and hydrogen atoms. Suitable compounds B) are C ₄ -Ci β-

Alkylmercaptans such as n-hexylmercaptan, n-octylmercaptan, tert-octylmercaptan, n-decylmercaptan, n-dodecylmercaptan, tert-dodecylmercaptan, n-hexadecylmercaptan and stearylmercaptan called.

Particularly preferred is tert-dodecylmercaptan.

The amount of the polymerization regulator B) is greater than 0.1 parts by weight per 100 parts by weight of monomers, the amount of B) is preferably greater than 0.5 parts by weight, more preferably greater than 1.0 parts by weight or greater than 1 , 2 parts by weight and most preferably more than 2 parts by weight; the amount is in particular not greater than 5 parts by weight, or not greater than 4 or 3.5 parts by weight per 100 parts by weight of monomers.

All parts by weight are based on 100 parts by weight of monomers.

Suitable for the process according to the invention are aqueous dispersion of a polymer obtainable by emulsion polymerization of radically unsaturated compounds (monomers) in the presence of at least two different polymerization regulators A) and B), characterized in that it is at

wherein the amount of A) is 0.01 to 1 part by weight and B) is more than 0.1 parts by weight per 100 parts by weight of monomers and the weight average particle size of the dispersed polymer particles is less than 120, especially less than 100 nm ,

Also suitable for the process according to the invention are aqueous dispersion of a polymer which is obtainable by emulsion polymerization of radically unsaturated compounds (monomers) in the presence of at least two different polymerization regulators A) and B), characterized in that it is at A) a compound selected from hydrocarbons which form a pentadienyl or 1-phenylallyl radical upon abstraction of a hydrogen atom, and

B) to a compound with a mercapto group

wherein the amount of B) is more than 2 parts by weight per 100 parts by weight of monomers.

The paper coating slips contain the above-described aqueous dispersion of the polymer as a binder.

For the process according to the invention, paper coating slips which contain pigments are particularly suitable.

Paper coating slips contain as an essential ingredient further pigments, in particular white pigments such as barium sulfate, calcium carbonate, calcium sulfoaluminate, kaolin, talc, titanium dioxide, chalk or coating Clay, and organic pigments, eg. B. luster pigments may be included.

The paper coating slips contain the above polymer, in particular in amounts of 1 to 50 parts by weight (solid, without water), more preferably 2 to 30 parts by weight and most preferably from 3 to 20 parts by weight per 100 parts by weight of pigment.

In addition to the polymer and pigment, the paper coating composition may contain other ingredients.

Called z. As optical brighteners, leveling agents, rheology additives, z. As thickeners, dispersants, emulsifiers and stabilizers.

The solids content of the paper coating slip is preferably between 30 and 80% by weight, in particular between 40 and 75% by weight, particularly preferably between 50 and 75% by weight.

For the curtain coating method, the extensional viscosity of the paper coating slip, z. B. by the addition of thickener, in particular to values of 1 to 1000 Pas, measured by the CaBER method at a Hencky strain between 1 and 15; more preferably values between 5 and 500 Pas, with a Hencky strain between 1 and 12 and very particularly preferably between 10 and 100 Pas, with a Hencky strain of between 1 and 8, as in the older application DE-A- 102004045172.9 described. The shear viscosity (100 rpm Brookfield) of the paper coating slip is preferably less than 5000 mPas, more preferably less than 2000 mPas and most preferably less than 1500 mPas, in particular the shear viscosity is at least 20 mPas.

In the method according to the invention, the coating with the paper coating slip takes place by the curtain coating method.

The substrate to be coated is, in particular, base paper or cardboard, prepainted papers or cardboard or satin (smoothed, for example by calendering) papers or cardboard. Preferably, it is a web-shaped carrier (paper web), which is moved according to the coating speed perpendicular or approximately perpendicular to the free-falling curtain of paper to be coated coating.

The coating speed is preferably 200 to 2500 meters / second, more preferably 500 to 2000 meters / second.

The width of the web-shaped carrier and according to the width of the free-falling curtain is z. B. 1 to 20 meters.

The paper coating slip to be coated falls in the form of a curtain on the moving substrate and forms a uniform coating.

After coating, drying takes place to remove the water.

The coating weight of the paper coating slip on the substrate to be coated (dry, without water) is preferably 0.1 to 200 g / m 2, more preferably 0.1 to 50 g / m 2.

The paper coating slips which can be used in the process according to the invention are also suitable for other application processes, such as doctor blade application or film compression processes.

The coatings obtainable by the process according to the invention are very uniform and show little or no defects. The coating speed is very high.

The resulting coated papers have good performance properties, in particular a high wet and dry pick resistance, good printability, especially in the offset process, high rigidity and a good gloss, in particular also print gloss. Examples

Synthesis Example 1 (Inventive: 3 TDMK + 0.2 terpinolene) In a polymerization vessel were placed 248 kg of water, 45 kg of a 15 wt .-% sodium dodecyl sulfate solution, 1, 5 kg of terpinolene, and 6.8 kg of a 10gew. % sodium persulfate before and heated with stirring to 95 ° C.

Then, over two separate feeds, starting at the same time, within 4 h

Monomer emulsion (feed 1) and the initiator solution (feed 2) while maintaining the temperature in the polymerization vessel. After completion of the monomer addition, the temperature was maintained for one hour at 95 ° C and then cooled to 90 ° C from.

Thereafter, feed 4 and feed 5 were fed in simultaneously within 2 hours.

It was then cooled to RT.

Subsequently, 20 kg of a 10 wt .-% sodium hydroxide solution was added.

Feed 1:

309 kg of styrene

288 kg of butadiene

40 kg of acrylonitrile 315 kg of deionized water

20 kg of an aqueous, 50 wt .-% acrylamide solution

18 kg of an aqueous, 15 wt .-% sodium dodecyl sulfate solution.

27 kg of acrylic acid

20.25 kg of tert-dodecylmercaptan 5.4 kg of an aqueous, 25 wt .-% sodium hydroxide solution

Feed 2:

45 kg of an aqueous, 10 wt .-% sodium persulfate solution

Inlet 4:

9 kg of a 10% strength by weight aqueous solution of t-butyl hydroperoxide

Feed 5:

9 kg deionized water 0.9 kg sodium disulfite 0.6 kg acetone

The solids content of the dispersion was 51% by weight. The light transmission was 86%. The weight-average particle size D50 was 89 nm. The pH was 6.2 and the glass transition temperature Tg was 7 ° C. Synthesis Example 2: (not according to the invention: 3 TDMK)

In a polymerization vessel to put 248 kg of water, 45 kg of a 15 wt .-% sodium dodecyl sulfate solution, and 6.8 kg of a 10gew. % sodium persulfate before and heated with stirring to 95 ° C.

The monomer emulsion (feed 1) and the initiator solution (feed 2) were then added over two separate feeds at the same time beginning within 4 h while maintaining the temperature in the polymerization vessel. After completion of the monomer addition, the temperature was maintained for one hour at 95 ° C and then cooled to 90 ° C from. Thereafter, feed 4 and feed 5 were fed in simultaneously within 2 hours. It was then cooled to RT. Subsequently, 20 kg of a 10 wt .-% sodium hydroxide solution was added.

Feed 1: 309 kg of styrene

288 kg of butadiene

40 kg of acrylonitrile

315 kg of deionized water

20 kg of an aqueous, 50 wt .-% acrylamide solution 18 kg of an aqueous, 15 wt .-% sodium dodecyl sulfate solution.

27 kg of acrylic acid

20.25 kg of tert-dodecylmercaptan

5.4 kg of an aqueous, 25 wt .-% sodium hydroxide solution

Feed 2:

45 kg of an aqueous, 10 wt .-% sodium persulfate solution

Inlet 4:

9 kg of a 10% strength by weight aqueous solution of t-butyl hydroperoxide

Feed 5:

9 kg of deionized water

0.9 kg of sodium disulfite

0.6 kg of acetone

The solids content of the dispersion was 50.4 wt .-%. The light transmission was

87%. The weight-average particle size D50 was 96 nm. The pH was 6.2 and the glass transition temperature Tg was 6 ° C. Synthesis Example 3: (according to the invention: 0.9 TDMK + 0.2 terpinolene)

In a polymerization vessel were placed 248 kg of water, 45 kg of a 15 wt .-% sodium dodecyl sulfate solution, 1, 5 kg of terpinolene, and 6.8 kg of a 10gew. % sodium persulfate before and heated with stirring to 95 ° C.

Feed 1:

353 kg of styrene

289 kg of butadiene

327 kg of deionized water

27 kg of acrylic acid

6.0 kg of tert-dodecylmercaptan (0.9 pphm)

5.4 kg of an aqueous, 25 wt .-% sodium hydroxide solution

Feed 2:

45 kg of an aqueous, 10 wt .-% sodium persulfate solution

Inlet 4:

9 kg of a 10% strength by weight aqueous solution of t-butyl hydroperoxide

Feed 5:

9 kg of deionized water

0.9 kg of sodium disulfite

0.6 kg of acetone

The solids content of the dispersion was 50.7 wt .-%. The light transmission was

82%. The weight-average particle size D50 was 108 nm. The pH was 6.2 and the glass transition temperature Tg was 6 ° C.

Coating paints were produced with these binders and coated on paper with a Curtain Coater 8 curtain coating method). Coating color composition

The coating composition (percentages and parts by weight) proposed according to the invention comprises a slurry of calcium carbonates CaCO 3 having a particle size of 2 μm, which makes up 95% of the slurry (for example Hydrocarb 95 ME available from OMYA, Oftringen, Switzerland) with a dry weight fraction of 77%. and an Amazon Premium clay slurry with a particle size of 2 μm, which makes up 98% of the slurry (eg Amazon Premium available from Kaolin International) with a dry weight fraction of 74.6%.

The coating color composition in the following examples, different binders A, B, C, mixed.

These are:

Binder A is styrene-butadiene latex as described in Synthesis Example 1.

Binder B is styrene-butadiene latex as described in Synthesis Example 2 (for comparison).

Binder C is styrene-butadiene latex as described in Synthesis Example 3.

All coating compositions with the different binders A to C were added as thickener (composition 40 mol% acrylic acid, 60 mol% acrylamide, 44 million molecular weight Mn) and a surfactant, namely an aqueous solution of sodium dialkylsulphosuccinates (Lumitene). DS 3525), available from BASF AG as well as an optical brightener eg Blancophor P available from Bayer AG, Leverkusen, added.

The pH of the pigmented coating compositions was adjusted to 8.7 by the addition of 10% NaOH. Solids content Coating formulations were adjusted by dilution with water.

Table 1 below gives an overview of the formulations. Table 1 Overview of the formulations

It can be seen from Table 1 that the formulations 1 to 3 of the coating composition differ from one another in each case by the added binders A, B, C.

The Brookfield viscosity of Formulations 1-3 was measured using a Brookfield RVT viscometer (available from Brookfield Engineering Laboratories, USA) at room temperature of 25 ° C. For measurement, 600 ml of the dispersion was placed in a 1 liter beaker and the viscosity was measured at a spindle No. 4 at a speed of 100 S " ¹ .

The coating composition according to Formulations 1 to 3 was coated on a wood-free base paper (basis weight 58 g / m 2) according to the examples given below. The properties of the contained substrates, be it paper or cardboard, were determined by the following test protocols.

Paper shine

Paper gloss is measured at an angle of incidence of 75 ° according to DIN 54 502

particle size

The particle size of the dispersions was determined in accordance with DIN ISO 13321. IGT - pick resistance

The pick resistance was determined according to ISO 3 783 with an IGT tester.

Specific volume

The specific volume was determined according to DIN EN 20 534.

Glass transition temperature Tg

The glass transition temperature of dispersion films was determined according to DIN ISO 53765.

Test Construction Offset (PB)

The test device includes a MZ II Printability tester, a test-pattern inking roller, metal pressure discs each 40 mm wide, a dispenser with 0.01 ml can be dosed and another order pipette can be dosed with the 0.001 ml and Langdruckprobenenträger and a stopwatch.

The ink used was Novavit 4F 713 Cyan (Käst & Ehinger). From the papers to be tested, samples having a size of 240 mm are cut to 46 mm in the longitudinal direction. Samples are stored separately in a climate room for at least 15 hours prior to testing.

To perform the test, the device is turned on, wherein 0.3 ml of the ink is added to one of the inking rollers and then a run of 1 minute takes place. Then a thrust washer is inserted into a designated holder and inked for 30 seconds. For each additional pressure disk, 0.03 ml of the ink is applied to the inking roller, followed by a 30 second run before staining. The colored inking roller can only be used for a certain period of time. The line pressure is set to 800 Newton (= 200 Newton / cm), the printing speed is 1 m / s. The paper strip is stretched on a print sample carrier and placed in the channel all the way to the right printing unit. On the right printing core, the inked printing plate is placed and with the operation of the start button, the start of the printing process. If the coverage is not achieved with the above listed ink quantity, the amount of ink and its supplement should be increased to 0.4, 0.04, 0.5 and 0.05 ml, respectively. Only when the cover point is reached with the paper strip, the test is continued. The print sample carrier is brought to the starting position with the printed paper strip. It is important to ensure that the strip is not with Touches fingers or other objects. After a specified period of time, typically 10 seconds, the printing process is restarted without replacing the pressure disk. This is repeated a total of five times.

After each pass, the plucking on the printed side of the paper strip is visually inspected. If plucking does not occur after six printing operations, the determination of the plucking tendency at longer intervals, e.g. Continued for 20 s or 30 s. The used pressure discs and the inking rollers are each cleaned with heavy fuel before the next use and then dried with a cotton cloth. The result obtained (passes to fail) is expressed in number of times until the first picking occurs.

Substrate roughness

The roughness of the coated substrates was determined by means of a Parker PrintSurf roughness tester. A sample of coated paper is clamped between a Cork-Melinex plate and a measuring head at a pressure of 1,000 kPa. Compressed air is applied to the substrate at a defined pressure of 400 kPa and then the air leakage between the measuring head and the paper surface is measured. High air leakage indicates high paper roughness of the coated substrate, be it paper or cardboard.

Order weight adjustment

The coating weight of the coating substrate to be spread on the substrate, whether paper or paperboard, was determined by the volume flow of the coating curtain through a curtain coating die nozzle, the paper web speed, the density of the coating composition and the width of the coated substrate at each application run certainly.

The coated substrates were then calendered with a Janus calender (Voith) under the following conditions:

Speed: 1 100 m / min Line load: 350 N / mm

Surface temperature: 1 13/122 ° C.

Curtain Coating Example 1

Formulation 1 with the binder A was applied to a wood-free, 58 g / m ² heavy base paper by simple curtain coating on this substrate. Here, the top OS and then the underside US coated first. The Coating weight per side is 15 g / m ² at a substrate web speed of 1,000 m / min.

Curtain Coating Example 2 (for comparison)

Formulation 2 of the coating composition with Binder B was applied to a woodfree, 58 g / m ² substrate by simple curtain coating on both sides of its surface at a coating weight of 15 g / m ² per side at a web speed of 1,000 m / min.

Curtain Coating Example 3

The coating composition according to Formulation 3 with binder C was also applied to a wood-free, 58 g / m ² heavy substrate by means of simple Vorhangstrei- chen on its surface. The application weight was 15 g / m ² per side at a paper speed of 1,000 m / min.

After calendering, the coated substrates coated according to Examples 1 to 3 and subsequently calendered under the above operating parameters had the following properties:

Table 2 Overview of paper properties of the calendered papers

Table 3 Overview Results Curtain Coating Examples 1 to 3

The following data was determined on the coated papers:

With comparable gloss and comparable roughness, Examples 1 and 3 according to the invention show better dry and wet plucking and improved offset printability.

Claims

claims

1. A method for coating substrates with paper coating slips, characterized in that

the coating is carried out by the curtain coating method, the paper coating slip contains an aqueous dispersion of a polymer as binder and - this aqueous dispersion is obtainable by emulsion polymerization of free-radically unsaturated compounds (monomers) in the presence of at least two different polymerization regulators A) and B), where it is

and the amount of A) is 0.01 to 1 part by weight and B) is more than 0.1

Parts by weight per 100 parts by weight of monomers.

2. The method according to claim 1, characterized in that it is at least 40 wt.% Of the monomers to so-called main monomers selected from C1 to C20 alkyl (meth) acrylates, vinyl esters of carboxylic acids containing up to 20 carbon atoms, vinyl aromatics with up to 20 carbon atoms, ethylenically unsaturated nitriles, vinyl halides, vinyl ethers of alcohols having 1 to 10 C atoms, aliphatic hydrocarbons having 2 to 8 C atoms and one or two double bonds or mixtures of these monomers.

3. Process according to claim 1 or 2, characterized in that at least 60% by weight of the monomers are butadiene, mixtures of butadiene and styrene, mixtures of butadiene and (meth) acrylonitrile or mixtures of butadiene, styrene and (meth) acrylonitrile acts.

4. The method according to any one of claims 1 to 3, characterized in that the weight ratio of butadiene to the total weight of styrene and (meth) acrylonitrile can be 10:90 to 90:10.

5. The method according to any one of claims 1 to 4, characterized in that it is from 0.05 to 10 wt.% Of the monomers are ethylenically unsaturated carboxylic acids.

6. The method according to any one of claims 1 to 5, characterized in that it is terpinols in the polymerization regulator A).

7. The method according to any one of claims 1 to 6, characterized in that the amount of A) is 0.02 to 0.4 parts by weight per 100 parts by weight of monomers.

8. The method according to any one of claims 1 to 7, characterized in that the weight-average particle size of the dispersed polymer particles is less than 120, in particular less than 100 nm.

9. The method according to any one of claims 1 to 8, characterized in that it is the substrates to raw paper, coated paper, calendered paper or cardboard.

10. Aqueous dispersion of a polymer obtainable by emulsion polymerization of radically unsaturated compounds (monomers) in the presence of at least two different polymerization regulators A) and B), characterized in that it is at

A) a compound selected from hydrocarbons which form a pentadienyl or 1-phenylallyl radical upon abstraction of a hydrogen atom, and

B) to a compound with a mercapto group

1 1. Aqueous dispersion of a polymer obtainable by emulsion polymerization of radically unsaturated compounds (monomers) in the presence of at least two different polymerization regulators A) and B), characterized in that it is at

A) a compound selected from hydrocarbons which form a pentadienyl or 1-phenylallyl radical upon abstraction of a hydrogen atom and B) a compound having a mercapto group wherein the amount of A) is 0.01 to 1 part by weight and B) is more than 0.1 parts by weight per 100 parts by weight of monomers and the weight average particle size of the dispersed polymer particles is less than 130 nm.

12. Paper coating slip, comprising an aqueous dispersion according to any one of claims 10 or 1 1.

13. Coated substrates, in particular coated papers obtainable by a process of claims 1 to 9.

14. coated with a paper coating composition according to claim 12 substrates.

15. Use of papers according to one of claims 13 or 14 in a printing process.