WO2005028750A1

WO2005028750A1 - Method and device for producing decorative paper and the use thereof

Info

Publication number: WO2005028750A1
Application number: PCT/EP2004/052146
Authority: WO
Inventors: Christoph Henninger; Martin Tietz; Volker Fäthke; Stefan Reich; Uwe Fröhlich; Gerold Bausch; Gunter Nink; Albert Sester; Rolf Weil; Nikolaus Grainer
Original assignee: Voith Paper Patent Gmbh; Papierfabrik August Koehler Ag
Priority date: 2003-09-16
Filing date: 2004-09-13
Publication date: 2005-03-31
Also published as: PL1664432T3; EP1664432B1; EP1664432A1

Abstract

The invention relates to a method for producing a decorative pigment coated paper. For this purpose, a white pigment-, in particular titanium dioxide-containing aqueous colour coating which is optionally filled with pigments is deposited on a coating base paper by means of a curtain-coating contactless process. The substance of the coating base paper ranges from 28 to 65 g/m<2>. The solid content in the applied aqueous colour coating ranges from 30 to 75 weight percent. After application, the aqueous colour coating is normally dried. The advantageous use of a product produced by the inventive method for decorating coating materials is also disclosed. Said method is economically used for producing an advantageous product.

Description

Method and device for producing a decorative paper and its use

The invention relates to a method for producing a decorative paper with a pigment coating and the advantageous use of such decorative paper for decorative coating purposes.

The invention also relates to a device for producing the decorative paper.

Previously, when filling the base base paper, mainly titanium-white pigments were used, possibly with pigment blends. The base paper had, for example, a basis weight of about 75 g / m ² . In order to achieve the necessary opacity with respect to the various applications in decorative paper, it has been customary to adjust the amount of titanium white pigment to about 40% by weight. Usually short fibers (for example about 80%, for example eucalyptus pulp) and long fibers (for example about 20%, usually softwood pulp) were predominantly used in the production of the base paper. This is usually followed by an equilibrium impregnation, ie, about 75 g / m ^{2 of} impregnating resin were applied. The production of such decorative paper was carried out in a paper machine, but no coating device was integrated. The impregnation could be done in a variety of ways, for example, with in-line or off-line processes by soaking, dipping or coating.

From the above descriptions, it becomes clear that it was difficult to produce lightweight papers. Here are certain limits, since the necessary to opacity required titanium dioxide pigment content due to the low pulp mass was not easy to incorporate. In the method described above, further disadvantages occur. Thus, in the production of the raw paper, a not inconsiderable proportion of the titanium white pigment enters the wastewater. This is economically disadvantageous because titanium white pigments are very expensive. Although the titanium white pigment can be circulated in the case of an optimal procedure. However, this means an extra effort and often leads to an undesirable circulation load.

The problems raised are partly solved by a proposal of the state of the art, which is based on the publication of the Paper Technology Foundation (PTS), Munich, entitled "The Saving of Titanium Dioxide Filler by Optimizing the Pigment Distribution in the Paper", (see ISSN0937-2091, 1st edition 1998, December 1998 edition). This results in a reduction of the mass of titanium dioxide in the base paper. This reduction is compensated by a coating color with an adjusted content of titanium white pigment. The application of the coating color e takes place here after the film press process.

The principle of the film press job is to apply a coating of paint film to a roller. There is a predosing with a doctor device, often grooved or smooth rods are used. It is usually applied on both sides. This process has significant disadvantages, especially at high speeds due to high mechanical wear of the application, metering and leveling elements (rollers, doctor blade, metering application) due to the abrasiveness of the pigments. In addition, by opening the nip often paint mist, filament formation (threads or thread pull) and drop formation. This results in unpleasant machine fouling, line defects and unwanted irregularities in the coating surface. It occurs the so-called "orange peel effect". These adverse effects occur especially at high order speed in appearance. Another disadvantage of this method is that the paper web is so strongly mecha- It is claimed that breaks often occur in the film press coating system, which has a particularly disadvantageous effect on on-line operation.

The decorative papers produced by the known processes show no ²U peace-satisfying printability. Desirable high retention of the pigments is achieved only incompletely. The dry application of the coating color is about 3 to 30 g / m ² , preferably 8 to 20 g / m ² .

The object of the invention has been found to remedy the above-mentioned disadvantages of the method of the prior art, in particular to ensure trouble-free operation and a reduction in the cost of raw material to a large extent exclusion of retention problems, in particular a fastest possible process control is provided.

This object is achieved in that an aqueous coating color is applied contactlessly to a coating paper filled with pigments by means of the curtain-coating method, wherein a basis weight of about 28 to 65 g is obtained from a base paper optionally filled with pigments / m ² and an aqueous coating of a solids content of about 30 to 70 wt .-% is assumed, and dried.

After application of the coating color, the paper web is dried in the usual way. This is generally carried out in a temperature range of about 70 to 450 ° C, in particular from about 80 to 250 ° C, wherein in most cases contactless drying units, such as infrared and air dryers are first directed to the freshly coated web surface and then a Cylinder contact drying takes place.

The core idea of the process according to the invention is the curtain coating process with the significant advantage that the aqueous coating color can be applied without contact to the respective base paper, in the present case optionally filled with pigments. The order can be advantageous in the 1: 1 ratio. This means that the amount of coating that is applied will remain on the surface of the paper without being scratched. In this case, no squeegee devices with squeegee elements, such as squeegee blades or squeegee blades, which are heavily subject to wear, need not be used. This and also due to the low circulation amount of coating color can save costs. In addition, the running properties of the decorating and / or finishing machines for the decorative paper web are improved. The curtain-coating process is particularly advantageous where it depends on a wear-free application of abrasive pigments. The curtain application unit consists essentially of a container having a slot nozzle, from which the coating compound or coating to be applied in free fall under the influence of gravity, but also under the influence of electrostatic forces on the respective paper web or their surface to be coated is applied. In particular, the following parameters can be varied: application quantity, web width, nozzle gap opening and selected pressure which acts, curtain fall height and, if necessary, the angle of the running paper web to the horizontal or to the curtain. The curtain delivered by the curtain applicator deposits on the surface of the paper web as a contour line and ensures a surface with high quality finishing.

The aqueous coating color used can be advantageously designed as follows: The solids content of the coating composition is preferably about 40 to 60% by weight. If the value falls below 40 wt .-%, then the order weights to be achieved are too low. A value of more than 60% by weight means that, especially when this amount of the solid is substantially due to the pigment content, the continuity of the curtain film is impaired. In such cases, it can happen that the curtain tears or tears off. In the case of the curtain coating method, the drop height of the coating color is preferably set to about 5 to 35 cm, in particular about 8 to 20 cm. Compliance with these basic conditions means that the curtain is maintained continuously even at high speeds. The same applies to the following physical information, which is an advantageous embodiment viscosity of about 150 to 1500 mPas (Brookfield, 100 rpm, 25 ° C.), in particular about 250 to 900 mPas, surface tension between about 25 and 60 mN / m, in particular from about 27 to 40 mN / m (static ring method according to Du Noüy).

In individual cases, it is expedient if the coating color contains processing aids, in particular surface-active substances, retention aids, surfactants, CMC, calcium stearate and / or (meth) acrylic acid / (meth) acrylamide copolymers. To promote opacity, the coating color is generally incorporated into titanium dioxide as a particularly effective opacity-increasing white pigment, in particular in the form of rutile, if appropriate in admixture with anatase.

In order to set a desirably high printability, further additives can be incorporated into the coating dye, such as, in particular, conventional inorganic extender pigments, such as clays, calcined clays, sodium aluminosilicate, aluminum oxide, silicic acids, diatomaceous earth and / or magnesium silicates, both of synthetic and natural origin. In addition, it is advantageous in individual cases to incorporate light-stable, aging-resistant colorants, in particular color pigments, into the coating color, in particular color pigments in the form of metal oxides, in particular iron oxides, and / or lightfast organic pigments.

It is furthermore preferred if the pigments of the coating color and / or of the coating base paper fakiitatively filled with pigments have a particle size of about 0.1 to 10 μm, in particular of about 0.1 to 2.0 μm. This range guarantees optimum properties, especially with regard to a desirable degree of opacity.

In selecting the coating paper optionally filled with pigments, the invention is not subject to any significant restriction. It has been shown that particularly good results are achieved when the coating color is applied to a paste. pier or cardboard web is applied, in particular a Bekk smoothness measured according to DIN 53101, from about 150 to 2000 s, in particular about 200 to 1000 s, set.

The coating color contains, in addition to the mentioned pigments or further additives, a binder, preferably in the form of homopolymers and / or copolymers. There are no significant restrictions here. It is of advantage if the homopolymers and / or copolymers are based on (meth) acrylic acid, (meth) acrylamide, styrene-acrylamide, melamine resins and / or urea resins. The (meth) acrylic polymers guarantee a high bond strength of the finished pigment coating at a relatively low content, so that it is not torn or damaged by occasional attack forces.

The base paper used in the context of the invention or provided with a pigment coating by the curtain-coating method may optionally be filled with pigments. With regard to the pigment content, it is advantageous for the décor paper obtained according to the invention if the total content of pigment (in the surface coating and also in the optionally coated with pigment base paper) is less than about 60 wt .-%, in particular less than about 40 wt .-%. If the content of pigment is too high, the desirable physical properties such as wet and dry breaking load and the like are not obtained to the extent required. The minimum content is measured by the opacity requirement.

In addition to the optional pigments, further materials can be incorporated into the coated base paper according to the invention, such as synthetic fibers for dimensional stabilization in addition to natural fibers. It is preferred if the long fiber content to about 0 to 50%, in particular about 5 to 50%, and the short fiber content is set to about 50 to 100%, in particular about 50 to 95%. In the composition of the present invention desired white decorative paper, it is particularly advantageous if the main components of the base paper represent a pulp mixture of eucalyptus short fibers and softwood long fibers, the white pigment is titanium dioxide. There may be small amounts of color pigments for shading next to also minor amounts of kaolin. Another component is preferably a wet strength agent, which is to ensure the fiber cohesion in the subsequent impregnation process.

In general, the coating base paper, optionally filled with pigments, is not provided with a pigment coating in the completely dry state by the curtain coating method. Conveniently, the moisture content of the coating base paper to be coated is between about 1 and 15% by weight, in particular about 2 to 8% by weight. Too dry a base paper would disadvantageously become electrostatically charged too highly in individual cases and impair overall production safety or running safety. Too high a moisture content of the base coating base paper would not have sufficient mechanical strength or dimensional stability.

The coating weight of the coating is not subject to any critical limitation. Preferably, this is at one-sided application to up to about 40 g / m ² , in particular up to about 3O g / m ² , and with two-sided application to each up to about 30 g / m ² , in particular up to about 25 g / m ² , discontinued. Preferably, the application amount is set at one-sided application between about 5 and 20 g / m ² and with two-sided application in each case to 5 to 12 g / m ² .

After application of a first pigment coat on the basis of the described coating color and subsequent drying, one or more further pigment strokes can be formed. As a result, a thicker pigment coating can be obtained, which would be cumbersome in a single order.

Although the coating can be operated off-line as well as on-line, it is still generally advantageous, especially for larger production facilities to run the operation on-line. In smaller installations, the off-line process can be advantageous in individual cases.

A particular advantage of the method according to the invention is that the process is possible at very high speeds. Thus, the process speed can be easily adjusted to at least about 500 m / min, in particular more than 750 m / min. However, it is also possible to set the speed to at least about 1000 m / min, in particular at least about 1500 m / min. These values can be exceeded with appropriate adjustment of coating color, coating weight and base paper, for example, be more than 1750 m / min. In this case, it is also possible without restriction to use pigments having a disadvantageously abrasive effect, since the abrasive coating composition according to the invention is applied contactlessly to the surface of the respective substrate.

With regard to the width of the curtain that falls freely or, for example, drawn with electrostatic forces in a certain direction, the curtain of the coating color in the curtain coating process has advantageous flexibility. Thus, in individual cases, if desired, the width of the curtain can be adjusted to more than the width of the raw paper web, in particular a paper or board web. Here, in contrast to known coating methods, the disadvantages associated with the uncoated edge of the coating base paper are remedied (edge relief, corrugation, uneven application weights on the edge and the like). The width of the base paper web can be up to more than 10 m, which places particularly high demands on the uniformity of the application in the curtain coating process.

The base paper web is advantageously coated with the curtain if it already has a solids content of about 65%, in particular more than 75% and preferably more than 95%. In this way, a particularly good coverage of the surface of the base paper web is ensured. The base paper can be used on one side smooth or preinsatinized. Here, the expert can therefore make an advantageous choice.

The curtain coating process has already been described in detail above. In addition, the following should also be stated: The clear outlet gap width of the curtain coating head of the coating unit is expediently set to about 0.1 to 1 mm, in particular to about 0.2 to 0.6 mm. It is advantageous if the nozzle throughputs for the specific coating color are set to about 0.3 to 15.0 cm ³ / (cm working width xs), in particular about 0.5 to 5.0 cm ³ / (cm xs) , In principle, the curtain coating head can be set to a single or multiple slit.

The papers or decorative papers with a pigment coating obtained according to the invention can advantageously be used for decoration of coating materials. Here are the advantages listed below in detail in appearance. It is particularly preferred if the decorative paper used is characterized by:

a coating base paper optionally filled with pigments having a weight per unit area of about 28 to 65 g / m ² , a content of less than about 60% by weight of pigment,

- A wet strength (wet tear length), according to DIN ISO 3781 of more than 4.5 N, preferably more than 6.5 N

- A dry fracture load, measured according to DIN ISO 1924-2, of more than 25 N, wherein the decorative paper has a pigment coating thickness of about 1 to 30 microns with a pigment content of about 50 to 90 wt .-% and a binder content of max. 50 wt .-%, each based on the total dry content of the coating color having.

A decor paper which is particularly preferably used for this purpose is characterized by a dry breaking load of about 30 to 35 N, a pigment coating having a thickness of about 2 to 15 μm, in particular 3 to 10 μm, a pigment content of 70 to 85% by weight. and a binder content of max. 30% by weight. A particular advantage of the method according to the invention over the prior art, as already mentioned, is that the applied coating color then need not be metered or smoothed with a doctor element. In individual cases, it is expedient to apply two or more strokes successively on the base paper. It is possible that the following line is applied to the dried pigment coating. But there is also the possibility of the "wet-in-wet" order. In addition, there is the possibility that a simultaneous application takes place, so with a cascade nozzle, with the same or different strokes can be applied.

It is in the aspect of "printability" possible to determine the most suitable amount of binder, which allows easy impregnation with constant product quality and also minimizes the dust propensity at low binder shares. It is also possible here to influence this by using different binders or binder mixtures. Among other things, the skilled person will consider further aspects as follows: Prevention of a dusty surface, increase of the binder content and prevention of a gluing effect with "mottling" effect (knock-out effect).

As a rule, a base pressure is applied by the customers of the decor paper obtained according to the invention, ie a full-surface coloring of the surface. Such imprinting is costly because at least about 2 to 3 g / m ^{2 of} job is required in a separate printing press. This can be avoided according to the invention by incorporating into the applied pigment coating, eg titanium white coating, the desired color pigments, resulting in a homogeneous full-surface coloring.

It is possible to form the pigment coating as a partial impregnation filling. This means that the pigment coating on the one hand fulfills the function of the surface coating and on the other hand as impregnation filling for the Raw paper comes to fruition. By reducing the pigment content in the base paper, which is desirable according to the invention, the decorative paper obtains a higher strength and also has a higher dimensional stability. The decorative paper is thus particularly well suited for use in the area of furniture decor as well as panels for floor laminates or tile imitations.

The pigment coating obtained according to the invention has a particularly advantageous printability or paintability for aqueous gravure printing systems or ink-jet coating systems. The paints are acid-curing or UV-curable paints. The printing can be carried out by various printing processes, in particular based on aqueous and partially solvent-containing gravure printing systems or ink-jet systems.

In addition to the above-mentioned advantages, the invention also offers the following advantages:

The curtain coating method used is advantageously controllable with regard to various properties, as already partially mentioned above, with regard to an adapted viscosity behavior, in particular extensibility, characterized by a sufficient internal cohesion, which is characterized by a pronounced thread length and Surface tension of the coating color shows. The usual characterization of coating colors is not sufficiently describable for the curtain coating process by known physical parameters such as surface tension, viscosity and the like. The forming within the scope of the invention, liquid curtain can be stabilized by a sufficient internal cohesion, otherwise he would tear off and at least cause a significant procedural disturbance. This property, which can be described as "extensional viscosity behavior", can be controlled or dimensioned in the form of the thread length of the liquid thread emerging from the Ford cup. The inventive method then leads to particularly desirable properties of the process product or can solve the stated problem particularly favorable when the thread length between 70 and 130 cm, in particular between 80 and 120 cm, preferably between 90 and 110 cm.

The invention will be explained in more detail below with reference to various examples:

Examples

The application of an aqueous coating color took place by means of the curtain coating process. The clear exit gap width of the curtain coating head was 0.3 mm (single brush). The curtain coating head was operated at a die throughput for the coating color of about 0.5 cm ³ / (cm working width xs). The viscosity of the coating color was adjusted to 400 to 450 mPas (according to Brookfield, 100 rpm, 25 ° C.). The surface tension of the coating color was 35 mN / m (static ring method). The coating was arranged on-line in the production plant. The application of the coating color was carried out on a paper web of a basis weight of 50 g / m ² (free of filler) and a Bekk smoothness, measured according to DIN 5301, of 200 s. The moisture content of the coating base paper was about 3% (ie dry content of 97%). The drop height of the coating color was set to 12 cm, the surface tension to 31 to 36 mN / m (static). The curtain coating process was operated at a speed of 850 m / min.

Furthermore, the coating color was adjusted with respect to the thread length in the Ford cup (nozzle 4) to a range of about 85 to 125 cm. After application of the aqueous coating color, the drying process of the coated paper web takes place in a customary manner.

On the basis of the above information, a decor paper was produced, wherein in each case the following formulations of coating colors were used to form the pigment coating: Recipe 1:

This is a titanium white or titanium dioxide-containing surface coating whose goal is, in particular, to improve the opacity of the finished product and to reduce the subsequent impregnation requirement.

1% Na polyacrylate (30% aqueous solution, dispersant), 60% titanium dioxide (white pigment, powder), 15% magnesium silicate (extender pigment, powder), 10% plastic pigment (27% aqueous suspension, hollow spheres of polystyrene / extender pigment), 0.5% calcium stearate (50% aqueous suspension, lubricant), 0.5% polyethylene wax (30% aqueous suspension, additive), 0.5% sodium diethylhexyl sulfosuccinate (100% liquid, surfactant), 10 % Styrene acrylate copolymer (50% aqueous dispersion, binder) and 2.5% acrylic acid / acrylamide copolymer (33% aqueous dispersion, thickener / viscosity modifier)

(Note: All above information refers to otro. -Wt .-% (oven-dry))

The lack of water to adjust to a solids content of 50% by weight was presented in liquid form when preparing the coating. The ingredients mentioned were added in the order given, taking into account the quantitative data with stirring.

Other information: Dry content of the aqueous coating color 50%, pH 8.2; Viscosity (according to Brookfield, 100 rpm, spindle 3, 20 ° C) 400 mPas, surface tension (at 20 ° C) 32.3 mN / m and thread length (in Ford cup with nozzle 4) 95 cm. The application was carried out with 25 g / m ² (otro) on the paper web.

Recipe 2: This is a titanium white or titanium dioxide-containing surface coating with which, in particular, the opacity of the finished product and the splitting strength should be improved and the subsequent impregnation requirement should be reduced.

1% Na polyacrylate (30% strength aqueous solution, dispersant), 50% titanium dioxide (white pigment, powder), 10% magnesium silicate (extender pigment, powder 5% plastic pigment (27% aqueous suspension, hollow spheres of polystyrene, extender pigment ), 0.5% o calcium stearate (50% aqueous suspension, lubricant), 0.5% o polyethylene wax (30% aqueous suspension, additive), 0.5%) sodium diethylhexyl sulfosuccinate (100% liquid product , Surfactant), 30%) melamine resin (binder and filling resin) and 2.5% o acrylic acid / acrylamide copolymer (33% aqueous dispersion, thickener / viscosity regulator)

(Note: All the above data are based on otro.% By weight (oven-dried), aqueous fraction analogously to Example 1)

Additional information: Dry content of the aqueous coating color 50%, pH 7.8, viscosity (according to Brookfield, 100 rpm, spindle 3, 20 ° C) 420 mPas, surface tension (at 20 ° C) 33.4 mN / m and thread length (in Ford cup with nozzle 4) 100 cm. The application was carried out with 25 g / m ² (otro) on the paper web.

Recipe 3:

Here, a kaolin line was formed on the designated coating base paper based on the above procedure. This is intended to improve the printability and the paint level. It was used as base paper, a standard standard decorative paper, the mass in the titanium dioxide content of about 30%. The composition of the coating color for the surface coating was as follows:

1% Na polyacrylate (30% aqueous solution, dispersant), 60% aluminum silicate (white pigment, powder), 10% magnesium silicate (white pigment, powder), 10% o plastic pigment (27% aqueous suspension, hollow spheres of polystyrene, extender pigment) , 0.5% calcium stearate (50% aqueous suspension, lubricant), 0.5% polyethylene wax (30% aqueous suspension, additive), 0.5% sodium diethylhexyl sulfosuccinate (100% liquid, surfactant) , 15% styrene acrylate copolymer (50% aqueous dispersion, binder) and 2.5% acrylic acid / acrylamide copolymer (33% aqueous dispersion, thickener / viscosity regulator)

(Note: All the above data refer to otro.-wt .-% (oven-dry), aqueous portion as in Example 1).

Additional information: Dry content of the aqueous coating color 40%, pH 8.5, viscosity (according to Brookfield) (100 rpm, spindle 3, 20 ° C.) 420 mPas, surface tension (at 20 ° C.) 34.0 mN / m and thread length (in Ford cup with nozzle 4) 115 cm. The order was carried out with 5 g / m ² (otro) on the paper web.

Recipe 4:

Here, a kaolin line was formed on the designated base paper on the basis of the above procedure. This is to improve the printability and the gap strength. As base paper, a standard standard decorative paper was used, which in the mass has a titanium dioxide content of about

20%. The composition of the coating color for the surface coating was as follows: 1% Na polyacrylate (30% aqueous solution, dispersant), 50%) aluminum silicate (white pigment, powder), 7% magnesium silicate (white pigment, powder), 8%> plastic pigment (27% aqueous suspension, hollow spheres of polystyrene, Extender pigment), 0.5% o calcium stearate (50% aqueous suspension, lubricant), 0.5% polyethylene wax (30% aqueous suspension, additive), 0.5%) sodium diethylhexyl sulfosuccinate (100% liquid product , Surfactant), 30%> melamine resin (binder and filling resin) and 2.5%) acrylic acid / acrylamide copolymer (33% aqueous dispersion, thickener / viscosity regulator)

Additional information: Dry content of aqueous coating color 40%, pH 7.6, viscosity (according to Brookfield, 100 rpm, spindle 3, 20 ° C) 450 mPas, surface tension (at 20 ° C) 34.5 mN / m and thread length (in Ford cup with nozzle 4) 115 cm. The job was carried out with 21 g / m ² (otro) on the paper web.

The invention will be further explained with reference to an exemplary embodiment.

Show it:

Figure 1: a schematic representation of a method according to the invention with inventive device with which or within a paper machine a decorative paper web to be produced.

Figure 2: a schematic diagram of the device according to the invention with a curtain applicator In both figures, the same reference numerals are chosen for the same components.

In FIG. 1, first of all a pulp bin B can be seen, which contains a pulp mixed with water to produce a wood-free raw paper web 1. The pulp in the example consists of 25% to 50% long fibers and, accordingly, 75% to 50% short fibers. To this fiber blend, no pigments and o-pazitätsfördernden substances were added in the existing outside of the paper machine Stoffbütte B. The mixture of substances is thus fed to the paper machine P in a quasi-simple manner, the mixture of substances initially arriving in a headbox 2 and then being formed on screens 3 as a web. Thereafter, the dewatering takes place within the press section 4, which is followed by the drying section 5a consisting of single-row drying cylinders. After reaching a dry content of at least 65%, in particular of at least 75%, preferably of more than 92%>, the paper web 1 is deleted. Thus, this paper web is suitable as decorative paper web and therefore should not be translucent, now opacitätsfördernde and whitening pigments and fillers are applied to the paper web 1. This is done with formulations that have been described in the previous examples. Since the opacifying and whitening additives have an extremely abrasive effect, a contactless curtain applicator unit 7 is integrated into the paper machine as an order unit. (Also possible as an offline coater).

With this commissioned work 7, it is possible that this amount of ink produced by the curtain 7a in the specified size can also remain on the paper without having to be stripped off.

The job, which is referred to as a 1: 1 job, takes place without pressing pulses and without suction on the paper web 1. As a result, the coating film sets on the paper surface, without penetrating into the paper web and affecting their further path within the paper machine P. , The binders contained in the application medium ensure good anchoring to the paper web. Depending on the setting of the chemical and physical properties of the Application medium can also be effected a targeted penetration of the application medium into the paper, for example, to increase the gap strength.

Following this, the coated paper web 1 is dried contactlessly and / or via contact release web guiding elements, such as e.g. led a so-called Air turn 8, further dried with floating dryers 9 and passed to subsequent (here double-row) drying cylinders, where in the Nachtock- game 5b the finished drying of the paper web 1 takes place. Finally, the paper web is rolled up in a winding machine 10 and is available for further processing, for example printing.

Alternatively, it is possible to smooth the paper web prior to its winding with calenders 11.

The decor paper web thus produced is characterized by high strength, ane constant and homogeneous coating and is almost opaque light.

It should be mentioned that both sides of the web can be painted one or more times with the given parameters. That depends on the particular intended use of decorative paper.

In Figure 2, the coating head 7.1 of the curtain applicator 7 is shown schematically and in section. The spreading head extends essentially over the entire machine width or width of the paper web 1 running in the running direction L. A slit nozzle or an exit slit 7.3 branches off from an inner ink chamber 7.2, which is adjusted by adjusting one or both of the lips 7, 4 and 7 forming the exit slit 7.5 in its gap width s, also seen in zones across the width of the entire curtain application unit 7, is adjustable. This adjustability is indicated by the two force arrows F. The gap width s is between 0.1 and 0.6 mm, whereby nozzle throughputs for the coating color to about 0.3 to 15 cm ³ / cm working width and second can be achieved. From the nip, the coating color in the desired coating composition according to the examples described above emerges in the form of a curtain 8 running in the direction of gravity and deposits in a contour line 7b as a cover layer on the base paper web 1.

Claims

claims

1 . A process for producing a decorative paper with a pigment coating, characterized in that an aqueous coating color is applied without contact to a coating base paper optionally filled with pigments by means of the curtain-coating process, wherein coating paper of a basis weight of about 28 to 15% filled with pigments optionally filled with pigments 65 g / m ² and an aqueous coating color of a solids content of about 30 to 70 wt .-% is assumed and dried.

2. The method according to claim 1, characterized in that the solids content of the coating color is between about 40 and 60 wt .-%.

3. The method according to claim 1 or 2, characterized in that the drop height of the coating color in the implementation of the curtain coating method to about 5 and 35 cm, in particular between about 8 and 20 cm, is set.

4. The method according to any one of claims 1 to 3, characterized in that the coating color has a viscosity of about 150 to 1500 mPas (Brookfield, 100 rev / min, 25 ° C), in particular from about 250 to 900 mPas.

5. The method according to any one of claims 1 to 4, characterized in that the surface tension of Streichfa rbe between about 25 to 60 mN / m, in particular between about 27 and 40 mN / m (static ring method according to Du Noüy) is set.

6. The method according to any one of claims 1 to 5, characterized in that the coating color is applied to a paper or board web, in particular to set a Bekk smoothness, measured according to DIN 53101, of about 150 to 2000 s.

7. The method according to at least one of the preceding claims, characterized in that the coating color processing aids are incorporated, in particular, for example, surface-active substances, retention aids, surfactants, CMC, starch, calcium stearate (meth) acrylic acid / (meth) acrylamide copolymers.

Method according to at least one of the preceding claims, characterized in that in the coating color to promote the opacity titanium dioxide, in particular in the form of rutile, optionally in admixture with anatase, is used.

9. The method according to claim 8, characterized in that the coating color to adjust a raw printability of the finished product customary inorganic extender pigments are added, in particular in the form of clays, calcined clays, sodium aluminosilicate, alumina, silicic acids, diatomaceous earth and / or magnesium silicates , both synthetic and natural origin.

10. The method according to at least one of the preceding claims, characterized in that the pigments of the coating color and / or optionally filled with pigments coating base paper has a particle size of about 0.1 to 10 .mu.m, in particular from about 0.1 to 2.0 microns, respectively.

11. The method according to at least one of the preceding claims, characterized in that the coating color light-stable, aging-resistant colorants, in particular color pigments, are incorporated.

12. The method according to claim 11, characterized in that the color pigments are present in the form of metal oxides, in particular iron oxides, and / or in the form of lightfast organic pigments.

13. The method according to at least one of the preceding claims, characterized in that the coating color is a binder in the form of homo- and / or copolymers based on (meth) acrylic acid, (meth) acrylamide, styrene acrylamide, melamine resins and / or urea resins, is incorporated.

14. The method according to at least one of the preceding claims, characterized in that the optionally filled with pigments coated base paper for dimensional stabilization contains synthetic fibers in addition to natural fibers.

15. The method according to claim 14, characterized in that the long fiber content of optionally filled with pigments coating base paper to about 0 to 50%, in particular about 5 to 50%, and the short fiber content of the coating base paper to about 50 to 100%, in particular to about 50 to 95% o, is set.

16. The method according to at least one of the preceding claims, characterized in that the application weight of the coating color in one-sided application to up to about 40 g / m ² , in particular up to about 30 g / m ² , and with two-sided application to each up to about 30 g / m ² , in particular up to about 25 g / m ² , is set.

17. The method according to claim 16, characterized in that the application amount of the coating color is adjusted at one-sided application to about 5 and 20 g / m ² and with two-sided application in each case to about 5 to 12 g / m ² .

18. The method according to at least one of the preceding claims, characterized in that after forming a first pigment coating one or more further pigment strokes are formed.

19. The method according to at least one of the preceding claims, characterized in that the optionally filled with pigments coated base paper has a moisture content of about 1 to 25 wt .-%, in particular from about 2 to 8 wt .-% having.

20. The method according to at least one of the preceding claims, characterized in that the coating is operated on-line.

21. The method according to at least one of the preceding claims, characterized in that the curtain coating process at a speed of at least about 500 m / min, in particular more than 750 m / min, operated.

22. The method according to claim 21, characterized in that the speed is set to at least about 1000 m / min, in particular at least about 1500 m / min.

23. The method according to at least one of the preceding claims, characterized in that the width of the curtain in the curtain coating process is set to more than the width of the base paper web, in particular a paper or board web.

24. The method according to claim 23, characterized in that the gap length of the curtain coating head is adjusted when brushing to about 15 to 25 cm above the respective substrate web edge addition.

25. The method according to at least one of the preceding claims, characterized in that the filler paper optionally filled with pigments is used on one side smooth or prussatinized.

26. The method according to at least one of the preceding claims, characterized in that the clear outlet gap width of the curtain coating head in the curtain-coating method to about 0.1 to 1 mm, in particular to about 0.2 to 0.6 mm, and / or the Nozzle throughputs for the coating color to about 0.3 to 15.0 cm ³ / (cm working width xs), in particular about 0.5 to 5.0 cm ³ / (cm xs) are set, the curtain coating head to a simple or multiple gap is adjustable.

27. Use of a obtained by the process according to any one of the preceding claims paper with pigment coating for decorative coating serkstoffe.

28. Use according to claim 27, characterized in that the paper is characterized by pigment coating for decorative coating materials by: - an optionally filled with pigments base paper of a basis weight of about 28 to 65 g / m ² , - a content of less than about 60 wt .-% pigment, - a wet strength (wet tear length), according to DIN ISO 3781, of more than 6.5 N, - a dry breaking load, measured according to DIN ISO 1924-2, of more than 25 N, wherein the decorative paper has a pigment coating thickness of about 1 to 30 microns with a pigment content of about 50 to 90 wt .-% and a binder content of max. 50 wt .-%, each based on the total dry content of the coating color having.

29. Use according to claim 28, characterized by a dry breaking load of about 30 to 35 N, a pigment coating having a thickness of about 2 to 15 microns, in particular from 3 to 10 microns, a pigment content of 70 to 85 wt .-% and a binder content of Max. 30% by weight>.

30. A device for producing a decorative paper with a pigment coating, characterized in that a contactless curtain applicator (curtain coater) (7) for applying the pigment coating (7b) to a substantially dried in the running direction (L) by a paper manufacturing and / or finishing machine (P) running base paper web (1) is provided.

31. The device according to claim 30, characterized in that the curtain application unit (7) has a coating head (7.1) with an outlet gap (7.3) whose clear outlet gap width (s) to about 0.1 - 1 mm, in particular is set to about 0.2 to 0.6 mm, wherein one or more exit gaps (7.2) for applying a single or multiple stroke (7b) are adjustable.

32. Apparatus according to claim 30 or 31, characterized in that the coating head (7.1) to the running base paper web (1) is adjustable so that the fall height of the curtain Application unit (7) delivered curtain (7a) is about 5 to 35 cm, in particular about 8 to 20 cm.