EP1792009A2

EP1792009A2 - Method for producing single or multiply coated substrates with the aid of a coloured coating composition comprising a binding agent for adhesion

Info

Publication number: EP1792009A2
Application number: EP05787450A
Authority: EP
Inventors: Erich Krumbacher; Oliver Birkert; Martin Schachtl; Christoph Hamers; Martin Tietz; Uwe Froehlich
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2004-09-17
Filing date: 2005-09-16
Publication date: 2007-06-06
Also published as: CA2580255A1; AU2005284219A1; AU2005284219B2; BRPI0515410A; JP2008513617A; CN101057035A; US20070212532A1; WO2006029883A3; US20100080919A1; DE102004045172A1; WO2006029883A2

Abstract

The invention relates to a coloured coating composition which can be applied to substrates which are to be coated, for example, base paper or cardboard, for the application in the curtain coating method. The substrate, which can be cardboard or base paper, is coated with one or several free-falling liquid curtains. The binding agent is added to the coating fluid. The binding agent is selected from the group containing styrol-butadiene latex binders, styrol-acrylate-latex binders, styrol-butadiene-acrylnitrile latex binders, styrol-maleic acid anhydride binders and styrol-acrylate-maleic acid anhydride binders. The binding agent has a particle size of < 130 nm.

Description

Process for the preparation of single or multiple coated substrates with a coating composition comprising a binder before adhesion

The invention relates to a process for the production of single and / or multi-coated substrates, such as paper or cardboard, excluding photographic papers and self-adhesive label papers, which are especially suitable for printing, packaging and labeling, wherein the substrate is coated in particular with one or more free-falling liquid curtains, wherein the free-falling liquid curtains are formed by a coating composition comprising a binder having a particularly high binding force.

State of the art

In the photographic industry, curtain coating is a well known process for coating substrates. However, the emulsions or liquids used so far as coating have a low solids content and a low viscosity; In addition, the speed of application is very low, which is currently below 600 m / min. In contrast, in the production of graphic papers, in contrast to the suspensions used in the photographic industry, pigmented suspensions with a high solids content are obtained and high viscosities used. Furthermore, graphic papers are mostly produced by blade coating or film presses at speeds significantly above 1000 m / min.

Both the blade application method and the film press application method each have specific disadvantages that affect the quality of the resulting coated substrates, such as base paper or paperboard. In the case of the blade application process, the aggregation of particles, induced by the high shear rates under the blade, can lead to streaks on the paper coating which worsen the paper or board surface quality obtained. Furthermore, the coating colors used in the graphic arts industry require the blade to be strong enough to require frequent replacement to ensure consistent line quality.

In addition, the line distribution on the paper or board surface is influenced by the unevenness of the substrate. An uneven line

B04 / 0441 PC Distribution on the paper or substrate surface leads to poor printing results, such as mottling phenomena (cloudy print).

The film press application method hitherto used for the production of graphic papers requires a narrowly dimensioned operation window, which is essentially determined by the factors substrate surface property, substrate porosity (Wegschlag¬ behavior) and coating color solid content. This narrow operating window is for each web speed, i. for each job speed and for each stroke weight. Non-optimized coating color receptors used in the film press application process can result in an uneven film splitting pattern on the surface of the substrate, be it paper or cardboard, which in turn has poor printability. Furthermore, in the film press application method, small drops can dissolve when painted and thus lead to quality losses. In contrast to the blade application method, the maximum achievable application weight by means of the film application method is significantly lower. This limitation of the maximum coating weight is particularly pronounced at high application speeds.

Both of the outlined methods of application, both the film press application method and the blade application method, suffer from the disadvantage that the application weight is distributed unevenly between ridges and valleys (mountains and valleys) which has the surface of the paper substrate, so that the ink acceptance is also uneven spread, which can lead to the above-mentioned Mottling effect (cloudiness of the pressure).

However, since both methods provide a relatively high application speed, well above 600 m / min, both the film press application method and the blade application method are very widely used in the production of graphic papers.

Japanese Patent Applications JP 94-89437, JP 93-311931. JP 03-177816, JP 93-131718, JP 92-298683, JP 92-51933, JP 01-298229, JP 90-217327, JP 8-310110 and EP-A 517 223 and EP-A 1 249 533 already disclose the Use of the existing coating method to coat a substrate with one or more pigmented coating colors. The use of the curtain coating for finishing substrates such as paper and board, as already disclosed in the abovementioned documents, leads to an improvement in the quality of the coated surface structure in comparison to previously used application methods such as the film press method or the blade order process. However, a curtain coating method is disadvantageous because at elevated application speeds and low application weights the applied liquid tends to instability. Added to this is the fact that when coating the coating composition applied by curtain coating on the surface of the paper substrate, the coating color is deflected from the free fall by approximately 90 ° and thereby accelerated to the substrate speed, which is too local very high shear and strain rates in the coating fluid. The fluid can be stressed too much in extreme cases that tearing of the film may occur due to cavitation bubbles. The risk of rupture of the applied coating color curtain increases with increasing speed of the substrate and represents the upper operating limit for the curtain application method.

Another critical parameter in the course of the curtain coating process on a substrate surface aufzustreichende coating composition represents the anchoring of the copy stroke on the surface of the paper substrate. Under certain circumstances, an insufficient anchoring of the paper coating on the surface of Substra¬ tes lack of print quality in web offset or Sheetfed offset printing process lead.

In view of the disadvantages of the prior art solutions, it is an object of the present invention to provide a coating composition which can be applied by the curtain coating method and which has a significantly improved binding power of the pigmented coating compositions.

Presentation of the invention

Following the present invention, a coating composition which can be applied by curtain coating is added to a styrene-butadiene based binder. The binder is selected on the basis of styrene-butadiene latex binder, styrene-acrylate latex binder, styrene-butadiene-acrylonitrile latex binder, styrene-maleic acid hydride binder and styrene-acrylate maleic anhydride binder having a particle size <130 nm. Synthetic polymers are, of course, suitable as binders admixed with the coating composition according to the invention. Starch may be mentioned as the natural polymer, and synthetic polymers are, in particular, those polymers which are obtained by free-radical polymerization of ethylenically unsaturated compounds (monomers).

The binder is preferably a polymer which consists of at least 40% by weight, preferably at least 60% by weight, and particularly preferably at least 80% by weight, of 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 of 1 alcohols containing up to 10 carbon atoms, aliphatic hydrocarbon having 2 to 8 carbon atoms and one or two double bonds or mixtures of these monomers. Mention may be made, for example, of alkyl (meth) acrylates having a C 1 -C 6 -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 may also be suitable. Furthermore, vinyl esters of carboxylic acids having 1 to 20 carbon atoms, for example vinyl laurate, vinyl stearate, vinyl propionate, versatic acid vinylester and vinyl acetate.

Suitable vinylaromatic compounds are vinyltoluene, α- and p-methylstyrene, α-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene and preferably styrene. As examples of nitriles, mention may be made of acrylonitrile and methacrylonitrile.

Vinyl halides are ethylenically saturated compounds substituted by chlorine, fluorine or bromine, vinyl chlorite and vinylidene chloride in particular being mentioned.

As vinyl ethers, mention may be made of e.g. Vinyl ethyl ether and vinyl isobutyl ether. Preference is given to using vinyl ethers containing alcohols having from 1 to 4 carbon atoms.

Suitable hydrocarbons having 2 to 8 carbon atoms and one or two olefinic double bonds are ethylene-propylene butadiene isopropene and chloropropene.

Preferred principal monomers are C ₁ -C ₁ o-alkyl (meth) acrylates and mixtures of the alkyl (meth) acrylates with vinyl aromatics, particularly styrene or hydrocarbons with double bonds, especially butadiene or mixtures of such hydrocar- sererstoffen with vinylaromatics, in particular styrene. In the case of mixtures of aliphatic hydrocarbons (in particular butadiene) with vinylaromatics (in particular styrene), the ratio may be, for example, between 10:90 to 90:10, in particular 20:80 to 80:20.

Preferred main monomers are butadiene and the above mixtures of butadiene and styrene (polystyrene butadiene for short) or C 1 -C ₁₀ -alkyl (meth) acrylates or mixtures thereof with styrene (polyacrylates for short).

In addition to the major monomers, the polymer may contain other monomers, e.g. Monomers with carboxylic acid, sulfonic acid or phosphonic acid groups. Preferably, carboxylic acid groups are used. Called e.g. 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 .-%.

Further monomers are, for example, hydroxyl containing monomers, in particular C ₁ - C ₁ o-hydroxyalkyl (meth) acrylates and (meth) acrylamide.

The preparation of the polymers is carried out according to a preferred embodiment by emulsion polymerization, therefore, it is an emulsion polymer. However, the preparation can also be carried out 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. The surfactant is usually used in amounts of 0.1 to 10 wt .-% based on the monomers to be polymerized. Water-soluble initiators for the emulsion polymerization are two ammonium and alkali metal salts of peroxydisulphuric acid, e.g. Sodium peroxidisulfate peroxide or organic peroxides e.g. TERT-butyl hydroperoxide. Also suitable are so-called reduction-oxidation (redox) initiator systems.

The amount of initiators is generally 0.1 to 10%, 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. In the polymerization, it is possible to use regulators, for example in amounts of from 0 to 0.8 part by weight, based on 100 parts by weight of the monomers to be polymerized, which reduce the molecular weight. Suitable compounds are, for example, compounds with a thiol group such as tert-butylmercaptan, thioglycolic acid ethylacrylic ester, mercaptoethynol, mercaptopropyltrimethoxylane or tert-dodecylmercaptan.

¹ emulsion polymerization is generally carried out at 30 ⁰ C to 130 ⁰ C, preferably 50 ⁰ C to 90 ⁰ C. The polymerization medium may be composed either of water alone or of mixtures of water and water-miscible liquids such as methanol. Preferably, however, 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 Stufen¬ or gradient mode. However, the feed process, in which part of the polymerization batch is initially introduced, is preferably heated to the polymerization temperature, then polymerized, and then the remainder of the polymerization batch, usually via a plurality of spatially separate feeds, one or more of the monomers or in emulsified form Containing form, continuously feeding stepwise or under siege of a concentration gradient while maintaining the polymerization of the polymerization. In the polymerization, it is also possible, for example for the purpose of better adjustment of the particle size, to initially introduce a polymer.

The manner in which the initiator is added to the polymerization vessel in the course of the free-radical aqueous emulsion polymerization is known. It can be introduced either 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 detail, this depends on the chemical nature of the initiator system and on the polymerization temperature. Preferably, a part is initially charged and the remainder is fed in accordance with the consumer in the polymerization zone.

In order to remove the residual monomers, it is customary to continue even after the end of the actual emulsion polymerization, i. after a conversion of the monomers of at least 95%, an initiator is added. The individual components can be added to the reactor in the feed process from above, from 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 from 15% by weight to 75% by weight, preferably from 40% by weight to 75% by weight.

The binder composition added to the coating composition based on styrene-butadiene latex binder, styrene-acrylate latex binder, styrene-butadiene-acrylonitrile-latex binder, styrene-maleic anhydride binder, styrene-acrylate maleic anhydride binder, polyvinyl acetate has a particle size of <130 nm.

drawing

FIG. 1 shows a diagram which shows the dependence of the binding force on the particle size and FIG

Figure 2 shows the influence of the particle size of the binder on the color density after a defined period of time.

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 composition is mixed with different binders A, B, C, D, E, F, G, H, I in the following examples.

These were in detail:

Binder A was styrene-butadiene latex (Styronal D 536 from BASF AG) with a particle size of 130 nm, Tg 0 ⁰ C and 50% in water. Tg was the glass transition temperature, the gel content was 83%.

Binder B was styrene-butadiene-acrylonitrile latex (Styronal D 627 from BASF AG) having a particle size of 140 nm, Tg 13 ° C., 50% in water. Tg indicated the glass transition temperature, the gel content was 80%.

The binder C used was styrene-butadiene latex (Styronal D 808 from BASF AG) with a particle size of 160 nm, Tg 22 ° C. and 50% in water. Tg denoted the glass transition temperature, the gel content was 72%. Styrene-butadiene latex having a particle size of 130 nm, Tg 0 ⁰ C, 50% in water was used as a further binder, namely binder D, neutralized in sodium hydroxide solution. Tg indicated the glass transition temperature, the gel content was 82%. Styrene-butadiene latex with a particle size of 165 nm was used as binder E, a Tg of 16 ° C., 50% in water. Tg denotes the glass transition temperature.

Another binder, binder F, was prepared by styrene-butyl acrylate latex, which presented a particle size of 175 nm, a Tg of 20 ⁰ C and 50% in water dar¬.

Another binder, Binder G, was represented by styrene-butadiene latex, which had a particle size of 115 nm, a Tg O ⁰ C, a solids content of 50%, the gel content was 85%.

Another binder, binder H, was represented by styrene-butadiene latex, which had a particle size of 100 nm, a Tg 0 ⁰ C, a solids content of 50%, the gel content was 76%.

Another coating composition contained a binder I, namely styrene-butadiene-acrylonitrile latex having a particle size of 80 nm, glass transition temperature Tg of -12 ° C and 50% in water, the gel content being 86%.

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

The pH of the pigmented coating compositions was adjusted to 8.7 by 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 9 of the coating color composition each differ from one another by the added binders A, B, C, D, E, F, G, H, I.

The Brookfield viscosity of Formulations 1-9 was measured using a Brookfield RVT Viscometer (available from Brookfield Engineering Laboratories, USA) at room temperature of 25 ° C. For the measurement, 600 ml of the dispersion were placed in a 1 1 beaker and the viscosity was measured at a spindle No. 4 at a conversion rate of 100 n ^-1 . The coating composition according to Formulations 1 to 9 were coated on substrates according to the examples given below. The properties of the contained substrates, whether paper or cardboard, were determined by the following test protocols.

Paper shine

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

Particle size The particle size of the dispersions was determined according to DEST ISO 13321.

Glass transition temperature Tg

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

Prüfbau Offset (PBt

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 0.001 ml dispenser can be dosed, as well as a long-run sample holder 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 ml were cut out to 46 ml in the longitudinal direction. Samples were stored separately in a climate room for at least 15 hours prior to testing.

To carry out the test, the device was switched on, wherein 0.3 ml of the printing ink was applied to one of the inking rollers and then a run of one minute took place. Then a pressure disk was inserted into a holder provided for this purpose and inked for 30 seconds. For each additional printing plate, 0.03 ml of the ink was 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 was set to 800 Newton (= 200 Newton / cm), the printing speed was 1 m / s. A strip of paper was stretched on a print sample carrier and placed in the channel all the way to the right printing unit. The inked pressure disk was placed on the right-hand printing core and actuated by the operation of the Start button was the start of the printing process. If the coverage point was not reached with the above-listed amount of printing ink, the quantity of printing ink and its supplement of 0.4 and 0.04 ml or 0.5 and 0.05 ml had to be increased. Only when the cover point was reached with the paper strip, was the continuation of the test. The print sample carrier was brought to the starting position with the printed paper strip. Care must be taken that the strip is not touched with fingers or other objects. After a fixed period of time, generally 10 seconds, the printing process was restarted without replacing the pressure disk. This was repeated a total of five times.

After each pass, the plucking on the printed side of the paper strip was visually inspected. If no plucking occurred after six printing operations, the determination of the tendency to pluck at longer intervals, e.g. 20 s or 30 s continues. The used pressure disks and the inking rollers were each cleaned with heavy gasoline before the next use and then dried with a Baum¬ wool cloth. The result obtained (passes to fail) was expressed in number of printing operations up to the occurrence of the first picking, the application of ink in ml and the time interval between individual passes in seconds.

Substrate roughness

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

Streak uniformity The substrate sample to be tested was completely immersed in a Neocarmin solution MS "FesagO" (available from Merck, Darmstadt) for one minute, after which the substrate sample to be tested was rinsed under running drinking water until no further staining was discernible sample was then couched between two filter papers and then dried in a laboratory dryer at a temperature of 90 ⁰ C. the appearance of the stained coating surface was assessed visually. Order weight adjustment

The coating weight of the coating material to be spread on the substrate, whether paper or cardboard, by means of the curtain coating method 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 coating determined substrate.

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

Speed: 710 m / min

Line load: 138 N / mm

Surface temperature: 120 ^° C.

Gel content determination

From the dispersion, a film having about 1 to 2 mm film thickness was cast. This film was dried at room temperature for 72 hours. Then, 3 squares of 1 cm side length were cut out from the obtained film and weighed. Each piece was placed in a closed vessel containing 30 ml of THF. The films were freed from solvent after 48 hours on a balanced metal screen. Subsequently, the sieve was dried with the polymer film, which was carried out at 80 ⁰ C for 2 h and the individual films were re-weighed. From the weight quotient (weight after washing / original weight), the gel content was determined.

Color density / penetration behavior

The assessment can also be done by color density measurement. If the ink transfer on a counter-stripe has no cloudy structures, the color density of individual segments on it is measured with the densitometer at 10 points in each case. Optionally, a graphic plot of the color density versus the strike time can be made at a time after printing in which the backsheet has been printed. As a result of evaluation with a densitometer, the relative color density RF in% is obtained. According to the following relationship

RF = 100 DM / DV with

RF = relative color density% DM = mean value of the measured values of the color density on a segment of both test strips

DV = average value of the measured values of the color density of the printed counterstrip. The result is represented by the color density on the printed counterstrip with two decimal places, against the travel time (time interval in s.).

example 1

Formulation 1 with binder A was applied to a wood free, 58 g / m heavy base paper by simple curtain coating on this substrate. The application weight was 15 g / m ² at a substrate web speed of 1,000 m / min.

Example 2 Formulation 2 of the coating composition with binder B was applied to a wood-free substrate weighing 58 g / m ² by simple curtain coating on its surface at a coating weight of 15 g / m ² at a paper web speed of 1,000 m / min.

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 Vorvorstrei¬ Chen on its surface. The application weight was 15 g / m ² at a paper speed of also 1,000 m / min.

Example 4

According to this example, a coating composition according to Formulation D was applied by simple curtain coating on a wood-free, 58 g / m ² heavy Rohsub¬ strat with an application weight of 15 g / m ² , wherein the Substratbahnge- speed was also 1,000 m / min.

Example 5

According to this example, a coating composition of Formulation F according to Table 1 was applied to a wood-free, 58 g / m ² heavy raw substrate by means of simple curtain coating on the surface of the binder E, wherein a coating weight of 15 g / m ^{2 was} set and the substrate web speed was 1,000 m / min. Example 6

In Example 7, a coating composition according to Formulation 7 with binder F was applied to a wood-free, 58 g / m ² heavy raw substrate by means of simple curtain coating on the surface, wherein a coating weight of 15 g / m ^{2 was} set and the substrate web speed also 1,000 m / min fraud.

Example 7

According to this example, a coating composition according to Formulation 8 with binder G was applied to a wood-free, 58 g / m ² heavy crude substrate by means of ein¬ fold curtain coating on the surface, the Auftragge¬ weight to 15 g / m ² at a substrate web speed of 1,000 m / min was set.

Example 8

According to this example, a coating composition according to Formulation 9 with binder H was applied to a wood-free, 58 g / m ² heavy raw substrate by means of simple curtain coating on the substrate surface with a coating weight of 15 g / m ² , wherein a substrate web speed of 1,000 m / min was set.

Example 9

According to this example, a coating composition according to Formulation 10 with binder I was applied to a wood-free, 58 g per square meter raw substrate by simple curtain coating on the substrate surface with a Auftragge¬ weight of 15 g per square meter, with a substrate web speed of 1000 m per min was set.

The substrates coated according to Examples 1 to 9 were then calendered with a Janus calender (Voith) under the following conditions:

Speed: 710 m / min

Line load: 138 N / mm

Surface temperature: 120 ° C. After calendering, the coated substrates coated according to Examples 1 to 9 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 Examples 1 to 9

The results according to Tables 2 and 3 make it clear that in order to obtain high binding forces between the upper side of a substrate to be coated by curtain coating, such as paper or paperboard and a coating composition applied to the upper side, high binding forces are obtained, if especially finely divided binders with a particle size of <130 nm are used.

Comparative Example Binding force in blade application method

Table 4 below gives an overview of a formulation applied to a substrate by the blade coating method.

Table 4 Overview of Blade-coated Formulation (Reference Formulation)

Comparative Example 1 Formulation No. 1 was applied to a wood-free 58 g / m ² raw paper by means of a conventional blade application method to the substrate at a coating weight of 15 g / m at a paper web speed of 1200 m / min ,

The substrates coated according to Reference Example 1 were then calendered with a Janus calender (Voith) under the following conditions:

Speed: 710 m / min Line load: 138 N / mm Surface temperature: 120 ⁰ C.

After calendering, the substrates coated according to Reference Example 1 then had the following paper properties under calendered, coated papers above operating parameter. The resulting results are summarized in Table 5 below.

Table 5 Overview Results Example from reference experiments

The results, which can be seen from Table 5, show that the binding force in the case of blade papers is significantly higher than papers coated by curtain coating, with otherwise good paper properties.

FIG. 1 shows a diagram from which the relationship between particle size and the resulting binding force of a coating composition is obtained.

The ordinate indicates the number of passes of a paper sample in accordance with the test construction offset mentioned above, up to which a first picking occurs. On the X-axis (abscissa) different binder particle sizes are plotted. The illustration according to FIG. 1 shows that the binding force of a coating composition drops with increasing particle size. For example, the coating composition containing a styrene-butadiene-acrylonitrile (SBAN) based binder having a particle size of 80 nm achieves a higher number of passes before plucking occurs (over six passes), while a paint composition containing a stain Binder (SBAN) with a particle size of 140 nm, only four passes (10 s) reached and then begins the plucking. In addition, FIG. 1 shows the number of passes of coating colors. Settlements to which a styrene-butadiene-based binder beige¬ was closed. With a particle size of 100 nm and 115 nm, six passages were possible before plucking occurred, whereas with a particle size of 130 nm only 4.5 passes could be achieved. In a coating composition containing formulation 1 with binder A, the plucking in the case of curtain coating coated papers had already been completed in four passes (10 seconds value), while papers coated with blade had reached five cycles at 30 seconds.

In curtain coating, binders with a small particle size of less than 130 nm can be used because the curtain coating process does not impose a pressure pulse on a substrate, which leads to a migration into the base paper, and thus a poorer binding force and less binding to the substrate Episode has. Due to the absence of a pressure pulse during the curtain coating process, the coating composition is not pressed into the base paper.

From the illustration according to FIG. 2, the influence of the binder on the color density is apparent.

On the y-axis (ordinate) the color density is plotted after 120 s Wegschlagzeit, while on the x-axis (abscissa) the particle sizes of the binder used are plotted. It can be seen from the graph of FIG. 2 that the color density remains substantially below the color density after 120 seconds of strike time in coating compositions containing a binder based on styrene-butadiene-acrylonitrile (SBAN) with a particle size of 140 nm of a coating composition comprising a binder (SBAN) having a particle size of 80 nm. In coating compositions containing a styrene-butadiene (SB) based binder having a particle size of 100 nm and 130 nm, the achievable color density after 120 seconds for the coating composition having a particle size of 100 nm is about 0.3, while the coating composition comprising a SB binder having a particle size of 130 nm, significantly darun¬ ter.

It can be seen from the illustration according to FIG. 2 that a SBAN binder having a particle size of 80 nm leads to a very high color density, which is considerably higher than that of FIG

Color density according to the reference experiment and a SB binder with a particle size of 100 nm also leads to a good color density which is still above the color density achieved in the reference experiment.

Claims

claims

1. coating composition for the preparation of one and / or multiple ge strichenen substrates except photographic papers and self-adhesive Etikettierpapiere which are suitable for printing, packaging and labeling, and the substrate, in particular raw paper or cardboard, coated with one or more free-falling liquid curtains and the liquid curtains are formed from a coating liquid containing a binder, characterized in that the binder is selected from the group consisting of styrene-butadiene latex binder, styrene-acrylate latex binder, styrene-butadiene acrylonitrile

Latex binder, styrene-maleic anhydride binder, styrene-acrylate-maleic anhydride binder, and having a particle size ≤ 130 nm.

2. coating composition according to claim 1, characterized in that styrene-butadiene and styrene-butadiene-acrylonitrile-containing binder systems ei¬ nen gel content of between 10% and 95%.

3. coating composition according to claim 2, characterized in that styrene-butadiene and styrene-butadiene-acrylonitrile-containing binder systems have a gel content of between 70 and 90%.

4. coating composition according to claim 1, characterized in that it contains organic or inorganic pigments.

5. coating composition according to claim 1, characterized in that it contains polyacrylamides having a molecular weight Mw between 1 and 50 million.

6. coating composition according to claim 1, characterized in that it has a Brookfield viscosity between 20 mPas to 5,000 mPas, more preferably be¬ between 20 mPas and 2,000 mPas, more preferably between 20 and 1,300 mPas.

7. coating composition according to claim 1, characterized in that the coating weight of the coating composition is based on their dry weight on the substrate 0.1 to 50 g / m ²

A coating composition according to claim 4, characterized in that the pigment or pigments are selected from the group comprising clay, kaolin, talc, calcium carbonate, titanium dioxide, satin white, synthetic polymer pigments, zinc oxide, barium sulfate, gypsum, silica, aluminum, trihydrate ,

9. coating composition according to claim 1, characterized in that the binder is selected from the group consisting of styrene-butadiene latex binder, styrene-acrylate latex binder, styrene-butadiene-acrylonitrile latex binder, styrene-maleic anhydride binder, styrene-acrylate maleic anhydride binder, Polysaccharides, proteins, polyvinyl pyrrolidones, polyvinyl alcohols, polyvinyl acetates,

Cellulose and cellulose derivatives.

10. coating composition according to claim 1, characterized in that the coating composition applied in the context of curtain coating improves the printability of a substrate, barrier properties against

Diffusion, the optical properties of the coated substrate ver¬ improved and either have release properties or adhesive properties auf¬.

11. Coating composition according to one or more of the preceding claims, characterized in that the curtain coating composition applied by way of the curtain coating method comprises one or more polymers based on ethylene-acrylic acid waxes, polyethylene-polyester-styrene-butadiene latex binder, styrene-acrylate latex binder, styrene Butadiene alcohol nitrile latex binders, styrene-maleic anhydride binders, styrene-acrylate maleic anhydride binders, polysaccharides, proteins, polyvinylpyrrolidones, polyvinyl alcohols, polyvinyl acetate, cellulose and cellulose derivatives, silicones.

12. A substrate prepared with a coating composition according to one or more of claims 1 to 10 have been prepared.

13. Use of a coating composition according to any one of claims 1 to 11 for coating substrates, base paper or cardboard by way of the curtain coating application method.