EP0909356A1

EP0909356A1 - Method and device for coating a continuous strip of material, specially paper or cardboard, with a liquid or paste-like application medium, method for the production of a coated strip

Info

Publication number: EP0909356A1
Application number: EP98917091A
Authority: EP
Inventors: Wilhelm Gansberger; Ingo Gottwald; Harald Hess; Friedrich Kunz; Martin Kustermann
Original assignee: Voith Sulzer Papiermaschinen GmbH
Current assignee: Voith Patent GmbH
Priority date: 1997-03-27
Filing date: 1998-03-26
Publication date: 1999-04-21
Also published as: WO1998044201A1; JP2000511604A; CA2255656A1

Abstract

The invention relates to a method and a device for coating a continuous strip of material (B), specially paper or cardboard, with a liquid or paste-like application medium. Said pre-dosed application medium is applied (at 240) directly or indirectly to the material strip (B), whereupon final dosing according to the desired weight of application and/or equalization (at 255) is carried out. Final dosing and/or equalization occurs only after a minimum time period (tmin) starting from pre-dosing in order to guarantee the formation of a coating of immobilized solids on the material surface in the application medium. Additionally or alternately, the immobilization of solids can be actively accelerated (by 278, 280, 282, 284). Another aspect of the invention provides for final dosing only after a maximum time period (tmax).

Description

Method and device for coating a running material web, in particular made of paper or cardboard, with a liquid or pasty application medium,

Process for producing a coated web

description

The invention relates to a method for coating a running material web, in particular made of paper or cardboard, with a liquid or pasty application medium, the application medium being applied directly or indirectly, predosed to the material web and then being metered or / and leveled to the desired application weight.

“Paper” and “cardboard” are understood to mean all wood-containing or wood-free, bleached or unbleached fibers or other webs of material with or without waste paper content. In addition to their intended use, these material webs differ mainly in their basis weight. For example, it can be writing paper, drawing paper, printing paper or similar fine paper, packaging paper or cardboard.

In many applications, at least the front, but sometimes also the back, should be provided with characteristic prints or design patterns. For this, the material web must provide a high quality surface. In practice, however, problems arise with all types of material webs with the quality of the covering of the material web surface by the application medium.

To achieve good coverage of the material web, it is necessary that the application medium not only on the tips of the coating "Mountain and valley" structure of the rough fiber structure is deposited, but also penetrates into the "valleys", and thus follows the contour of the material web over its essentially entire surface.

So far, it was assumed that such a contour line character of the coating and thus the desired good coverage of the material web can only be achieved by dosing the application medium with an air knife or an air brush, i.e. a squeegee device which blows the excess application medium away from the material web with compressed air. However, the following disadvantages had to be accepted:

Material web speed at most 400 m / min; Working width at most about 7.0 m; the solids content of the application medium may at most be about 40%, which entails an increased outlay on drying; high tendency to soiling, in particular due to aerosol or / and foam formation; high noise level; - high investment and operating costs.

A coated carton is known from WO 96/28609, which is used for the production of carton molded parts, for example milk containers. The cardboard is formed from one or more layers of fibrous material and coated with a view to printing its surface. After coating and, if desired, also before coating, the cardboard is additionally smoothed, using a heatable or non-heatable calender, which can have both a hard and a soft nip. Details about coating the carton are not disclosed. The object of the invention is to provide a method of the type mentioned at the outset which allows good coverage of the material web to be achieved even at high web speed, large working width and high solids content of the application medium.

According to a first aspect of the invention, this object is achieved by a generic method in which the final metering and / or leveling takes place at the earliest after a time t _min , which is given by the following formula: t _min = k ₀ x (k, x CW + k ₂ ) x CW ² , where

CW denotes the coat weight to be achieved of the applied application medium layer in g / m ² , k _{0 is} a first constant, the value of which is at least 1, preferably at least 1.5, k, is a second constant, the value of which is -0 , 03603 x 10 ^"5 m ⁶ min / g ³ , and k _{22 is} a third constant, the value of which is 1, 206 x 10 ^'5 m ⁴ min / g ² .

According to the invention, the application medium is therefore given a predetermined minimum time to act on the material web. During this time, some of the solids contained in the application medium are immobilized on the surface of the material web. On the one hand, part of the moisture contained in the application medium strikes the material path. In addition, the capillary forces exerted by the material web on the application medium have the effect that the application medium is also sucked into the valleys of the fiber structure. Both effects together lead to a uniform and good coverage of the material web surface. The subsequent final metering preferably does not intervene in the contour line portion formed by the immobilized application medium, but rather doses and equalizes the still liquid or pasty and therefore not yet immobilized part of the application medium.

The immobilization of part of the application medium can be further strengthened in that the value of the first constant k _{0 is} at least 2, preferably at least 3, more preferably at least 4.

In order to achieve the best possible coating result and in particular the best possible degree of coverage, it is proposed in a development of the invention that the time t between pre-metering and finished metering is adjustable. For this purpose, the position of the pre-metering and / or the position of the finished metering can be changed in the running direction of the material web.

Advantageously, at least one property of the finished metered application medium layer, for example the degree of coverage mentioned several times above, can be detected by means of a sensor device and the time between pre-metering and finished metering can be set as a function of the detection result. Of course, in addition or alternatively, other parameters of the finished metered application medium layer can also be taken into account in the setting, for example its smoothness, its gloss, its whiteness and the like.

The degree of coverage or / and the other parameters mentioned above can be determined on the still moist application medium layer or / and during its drying or / and on the dried application medium layer. Detection at the winding device can also be considered.

With sufficient dimensioning of the diameter of a support roller, which is wrapped around at least in sections by the material web, both the pre-metering and the finished metering can be carried out in one of the

Material web wrapped around the circumferential section of the support element When the diameter of the support roller is "sufficient" depends, of course, on the web speed and the like operating parameters. To provide the minimum exposure time according to the invention, however, the material web can also be guided around a support element, preferably a support roller, in the area of the pre-metering and around a further support element, preferably another support roller, in the area of the finished dosage.

In both of the alternatives discussed above, the material web can be deflected between pre-metering and final metering by at least one intermediate guide element, preferably at least one deflection roller. In the case of the first-mentioned alternative, the material web is thus led away from the back-up roll after the pre-metering, runs around the intermediate guide element and back again to the back-up roll, where the finished metering takes place. Thus, even for back-up rolls with a relatively small diameter, both the pre-metering and the finished metering can be carried out on one and the same back-up roll.

According to a further aspect, the above-mentioned tasks are solved by actively accelerating the immobilization of the applied medium on the material web during its movement from the pre-metering to the finished metering. This can also ensure that an immobilized layer of solids contained in the application medium is formed on the surface of the material web, which layer covers the material web surface evenly and well.

The active influence on the formation of the immobilized layer can consist, for example, of heating or / and drying the applied layer. But you can also heat the material web, which in turn indirectly heats up the application layer. For heating, the applied layer or / and the material web can be irradiated with infrared light and / or microwaves, for example. Additionally or alternatively, heated air and / or steam can also be supplied to the applied layer and / or the material web. Finally, it is also possible to heat the material web and / or the applied layer by means of convection heating or to bring it into contact with at least one heatable element, preferably a heatable roller or a heatable belt.

The latter possibility of heating the material web and / or the application medium layer can be realized, for example, by heating a support element, preferably a support roller, around which the material web is guided in the area of the pre-metering. Additionally or alternatively, it is also possible to heat a web guiding or / and treatment element, preferably a roller, provided between pre-metering and finished metering.

Another way of actively accelerating the immobilization process is to apply a vacuum to the material web from the side opposite the order side. For this purpose, for example, a support element, preferably a support roller, around which the material web is guided in the region of the first position, can be equipped with a suction device. It is also possible to provide at least one web guide or / and treatment element equipped with a suction device, preferably a deflection roller with a suction box, between the pre-metering and the finished metering.

In addition or as an alternative to the vacuum solution discussed above, provision can also be made for the material web to be pressurized from the application side. In order to accelerate the immobilization of the application medium, the material web and / or the applied layer can also be exposed to vibrations, for example by irradiating the material web or / and the applied layer with ultrasound or / and by the material web or / and the applied layer being coated with an, brings into contact, preferably high-frequency operable, vibration device.

In order to achieve the desired quality of the application medium layer, the intensity of the active influencing of the immobilization of the applied layer on the material web can be adjustable, for example depending on the result of the detection of at least one parameter of the completely dosed application medium layer. Again, the covering quality of the application medium layer, its smoothness, its gloss, its degree of whiteness and the like can be used to determine the intensity of influence required in each case.

The final metering can be carried out either by means of a smooth doctor rod or by means of a profiled doctor rod or by means of a doctor blade. A "profiled" doctor rod is understood to mean a perforated, etched, engraved, grooved or wire-wound doctor rod. Experiments have shown that a contour stroke effect can be achieved primarily by volumetric dosing with a profiled doctor rod as a doctor element.

So that profile grooves do not remain on the coated material web when using a grooved doctor rod, it can be advantageous to reduce the solids content of the application medium compared to the usual value (application with roller applicator and subsequent doctor blade) so that the application medium can flow again after doctoring . In other words, the application medium should be so fluid that the grooves created can flow again after metering and leveling. When using a smooth doctor rod, the contour stroke effect described above is less pronounced when dosing. However, due to the scooping effect of the smooth rod, satisfactory results can still be achieved, especially from the valleys of the railway. The application medium can be somewhat more viscous and does not need to be as fluid as with the profiled doctor rod, because there is no risk of grooves forming here.

According to a further aspect, the above-mentioned tasks are solved in that the final dosing and / or leveling takes place at the latest after a time t _max , which is given by the following formula: t _max = A (CW / K) ² - A 'where

CW denotes the coat weight to be achieved of the applied application medium layer in g / m ² ,

K denotes the solids content of the application medium in%,

A is a first constant, the value of which is 9.28 m% ² sg ^"2 for the profiled doctor rod and ² is 8.86 m% ² sg ^{" 2} for the smooth doctor rod and the doctor blade 1, A 'is a second constant, the Value for the profiled

Doctor blade 21, 4 x 1 0 ^"3 s and for the smooth doctor blade and the doctor blade is 24.0 x 10 ^'3 s, and the formula being only for

CW / K> / A7A "is valid. In this way it can be ensured in particular that the metering element only moves in the still liquid or pasty part of the application medium layer and does not interfere with the already immobilized solids when finished metering. Thus, the occurrence of line defects is avoided as well as good coverage of the surface of the material web. Another advantage is that there is a better rinsing effect in the area of the doctor element, through which particles or deposits that come out of the paper or cardboard can be removed.

The final metering or / and leveling can preferably take place at the latest after a time t for which 0.1 t _max <t <0.8 t _max , preferably 0.1 t _max <t <0.5 t _max .

In order to be able to further improve the quality of the coated material web, it is proposed to apply a plurality of application layers to the material web. For example, the top side, often also called the top side, can be coated a second time after drying and, if necessary, pre-smoothing. Most of the time, however, a pre-coat, a middle coat and a top coat are applied to the material web to achieve good coverage.

The individual lines can be applied, for example, by means of a roller applicator. These belong to the group of so-called LDTA (Long Dwell Time Applicator) and include a scoop roller that scoops the application medium from a storage container. According to the invention, however, other types of commissioned works can also be used, as will be explained in more detail below.

Following the respective coating, the excess application medium is then scraped off the material web. A doctor blade or a smooth doctor rod is used for the primer. The doctoring serves to level the surface both in the micro and in the fiber flake area.

The second coat, the middle coat, usually has a higher coat weight than the pre-coat. According to the state of the

Technology became the excess application medium to achieve good ones

Cover the material web surface with an air knife or a Air brush scraped. However, a doctor blade, a smooth or a profiled doctor rod can now be used in the method according to the invention.

Finally, a slightly lower coat weight can be applied to the top coat than to the middle coat, roughly corresponding to the upper limit of the coat weight for the primer. The excess medium is removed with a doctor blade, as this ensures better smoothness of the application layer.

According to the invention, it is therefore possible, for example, to scrape off or meter the precoat and the middle coat with the smooth or profiled doctor blade rod and the remaining coat or coats with a doctor blade. However, all applied strokes can also be doctored or dosed with a doctor bar.

It is particularly advantageous if the predosing, i.e. the excess application takes place in at least one of the lines with a so-called free jet application unit (this is a nozzle application unit with a fountain or free jet acting on the web). With free jet application there is less - and almost negligible - pressure penetration than, for example, with a roller applicator. This means that the stroke is deposited more on the surface of the material web during free-jet application, whereas with the roller applicator with its significantly higher penetration pressure in the nip between application and counter-roller, the application media penetration and absorption varies due to the given raw paper formation in the sheet plane. Therefore, the contour line character of the line portion immobilized up to the doctor element is less pronounced than in the case of the free jet application.

In the case of free jet applicators, the liquid portion of the medium applied to the surface of the web that contributes to the coat weight is larger than with the roller applicator, which means that doctor blades can be used advantageously for dosing. Squeegee strips are thus largely avoided. In addition, better smoothness values can be achieved due to less fiber swelling and back-roughening in paper or cardboard.

In addition, there is less thickening of the application medium, so that higher solids contents of the application medium can be used, which is advantageous for achieving good coverage of the material web surface. The result is a more compact stroke with higher gloss and smoothness. Another advantage is the fact that the drying device manages with lower drying performance.

So-called SDTA orders (Short Dwell Time Applicator) can also be used as order books. These are contract works in which the application medium can only act on the material web for a relatively short time until metering by means of the doctor element. Finally, the application medium can also be applied to the surface of the material web using the film coating method.

The method according to the invention shows the advantage discussed above regardless of the structure of the base paper fed to the coating station, ie regardless of how it was produced in the wet area of the paper machine. The paper or cardboard may have been produced in one or more layers or also in one or more layers, ie it may have been worked with one or more headboxes and screens or also with one primary headbox and, if desired, several secondary headboxes or corresponding combinations thereof. The base paper can at least be glued to the mass in one of the layers or layers or else have already contained starch in the raw mass. Depending on the requirements placed on the covering quality of the coated material web, it can be provided according to the invention, at a desired location within the paper machine in addition to the coating, impregnating agents and / or strengthening agents, such as starch, synthetic glue with or without pigments, on the surface of one or both sides of the Apply material web. This application of impregnation or strengthening agent can serve to prepare for the coating and / or to aftertreat the applied layer.

The treatment with impregnating or strengthening agent can take place, for example, in the wire section or / and between the wire section and press section or / and in the press section or / and between the press section and dryer section and / or after the dryer section with or without post-drying or / and in front of the winding device . In the case of multiple coatings, it can also be carried out between successive partial coatings.

In a further development of the invention, the material web can be smoothed before or after the coating or between successive partial coatings. Pre-smoothing before the application of the coating or the first partial coating, i.e. of the primer. Post-smoothing is particularly advantageous if very high smoothness and gloss values are to be achieved. To further increase the quality, smoothing between the individual partial coatings is also possible.

The smoothing can be done with hard nips, with soft nips or with a wide nip. It is advantageous for high smoothness and gloss values if at least one of the two smoothing surfaces forming the respective nip can be heated. Smoothing devices are known per se. For example, they include at least two opposing smoothing surfaces, for example roller surfaces, between which the material web is subjected to a smoothing treatment. Also known are Brettnip smoothing units, for example shoe smoothing units or roller smoothing units with a large roller diameter, which have a longer nip. This increases the length of time the web stays in the nip, which results in better smoothing. Breitnip smoothing units can be used with advantage both for pre-smoothing and for post-smoothing.

Nip combinations of hard rolls, soft rolls or hard and soft rolls can be used. Furthermore, such nip combinations can also be arranged in a row. For example, a device with two separate nips, each with a heatable hard and a soft roller, is conceivable. The combinations mentioned above are not intended to limit the scope of protection. Rather, other combinations are also conceivable, in particular devices with three and more rollers per unit.

A so-called water scraper smoothing unit can also be used as a smoothing device. Finally, it is also possible to smooth the application medium layer using a blowing device.

In the case of pre-smoothing in particular, it can be advantageous if the material web is moistened with water or steam before smoothing in order to achieve even better smoothing results, for example leveling the surface while protecting the volume at the same time.

When using a profiled doctor rod, the application medium can have a viscosity of <500 mPas, preferably 30 mPas to 250 mPas

Using a smooth doctor rod, a viscosity of <2500 mPas, preferably 300 mPas to 1000 mPas, or when using a doctor blade blades have a viscosity of <4000 mPas, preferably 300 mPas to 1 500 mPas, these viscosity values to be determined according to Brookfield 100. Furthermore, the application medium can contain 4 to 20 (or 25) parts of binder per 100 parts of pigments, at least some of which contain plastic binders and / or starch. Often the application medium contains - partly also for the top coat - titanium dioxide (Ti0 ₂ ), since this pigment has a favorable effect on the coverage and whiteness that can be achieved.

In the case of a multiple coating, at least two of the application layers can be formed from application medium of different composition. However, it is also possible for at least two of the application layers to be formed from application medium of the same composition.

At least one of the application layers can be formed from an application medium which has a solids content that is at least 2% to 5% lower than at least one other application layer, the solids content of this at least one other application layer being approximately 50% to 73%.

In order to be able to achieve the best possible covering quality and / or the best possible application result, it is proposed that the composition and / or the temperature of the application medium and / and the temperature of the material web be set, for example by at least one property of the finished dosage Application medium layer, such as covering quality, smoothness, gloss, whiteness and the like, is detected and the composition and / or the temperature of the application medium and / or the temperature of the material web is set as a function of the detection result. According to further aspects, the invention relates to various devices for coating a running material web, in particular made of paper or cardboard, with a liquid or pasty application medium. Details and advantages of these devices have already been explained above with reference to the discussion of the methods according to the invention, to which express reference is hereby made.

The advantages of the method (s) according to the invention and the device (s) according to the invention can be seen above all in the following points: In some cases, lower application weights can be achieved. Higher solids contents of the application medium can be used. In some cases, the Ti0 ₂ content in the application medium can be reduced. The material webs can be coated at higher web speeds of over 600 m / min over larger working widths.

Experiments have shown that with the methods according to the invention a satisfactory covering quality can be achieved even with a line application of 9 g / m ² . With an application of 15 g / m ² , it was possible to achieve a coverage quality which even exceeded the coverage quality of a coating which, with a comparable coat weight, was metered in by means of an air knife using a method of the prior art.

According to a further aspect, the invention relates to a method for producing a coated fabric web, in particular from paper or cardboard, according to the preamble of claims 82 and 85.

The terms "paper" and "cardboard" are to be understood to mean all wood-containing and wood-free, bleached or unbleached fibers, and also other types of fibers containing waste paper and non-waste paper. This can be paper per se, packaging paper or, as already mentioned, cardboard, these types being mentioned in addition to their intended use, they also differ in terms of their basis weight.

With all of these types, problems with the covering quality on at least one side (mostly the top, sometimes also the back) occur again and again when these are deleted.

As a rule, the painted page should be provided with distinctive imprints or design samples. For this, it must provide a good basis.

There are still no satisfactory solutions for this.

WO 96/28609 discloses a coated cardboard for shaped articles, e.g. B. milk container known.

From this laid-open specification it can be seen that the cardboard has one or more layers of fibrous material and the surface of the cardboard, in order to be suitable for printing, is coated and subsequently, and alternatively also smoothed before coating.

Smoothing is done with a heatable or non-heatable calender, which has a hard or soft nip.

Details about painting the carton are not disclosed.

Up to now, in practice, cardboard has been coated at least twice after drying and possibly pre-smoothing, for example the top, often also called the top side. Most of the time, however, in order to achieve good coverage, it was painted three times with a pre-coat, a middle coat and a top coat. Roller coaters and air knife coaters, which belong to the group of the so-called LDTA (Long Dwell Time Applicator), were primarily used for the individual lines.

A scoop roller was used in each case for the roller applicator, which scoops the application medium from a storage container. After the respective coating, excess medium was scraped off the web. This was done when priming with a blade or a smooth squeegee. This serves to level the surface both in the micro and in the fiber flake area.

In the second coat (middle coat), which was usually applied with a higher coat weight than the first coat, the excess medium was blown away with an air knife or air brush. A fairly good coverage of the fibrous web was thereby achieved (which is the advantage of the air knife coating method), but the following disadvantages, for example, had to be accepted:

Speed limit of the web at approx. 400 m / min - production-related limit of the working width up to approx. 7.0 m,

Manufacturing-related limit of the solids content of the application medium of approx. 40%, as a result of which a higher outlay in line drying had to be carried out.

For the third stroke, which was executed as a top coat, a slightly lower stroke weight was usually applied than for the middle stroke (corresponding approximately to the upper limit of the first stroke). The excess medium was scraped off here with a doctor blade, because this usually produces better smoothness. In some cases, the last stroke was carried out as an air knife stroke. Previously, it was believed that only an order leveled with an air knife would give the best results in terms of coverage, and therefore accepted the disadvantages listed above.

The corresponding coating (i.e. the application medium) - sometimes also the top coating - often contain titanium dioxide (Ti0 ₂ ) in order to make a further contribution to coverage and whiteness via this pigment.

The object of the invention is to provide a method with which it is possible to produce coated papers, in the manufacture of which higher web speeds, larger web widths and higher solids contents of the application medium can be driven and yet coverage, gloss and smoothness can be achieved in the same way or better than before .

According to the invention the object is achieved by the characterizing features of claim 82 and the independent claim 85.

Appropriate embodiments of the method according to the invention result from the dependent claims 83, 84 and 86 to 1 02.

It has been found that the desired properties of the paper or cardboard can be achieved with a first method if the metering of the corresponding line, ie the line ensuring the covering, for example pre-and / or middle line, is not done with an air knife as in the prior art. or air brushing unit at an inevitably lower speed, but with a smooth or profiled (for example perforated, etched, engraved, grooved or wire-wound) doctor rod. Even lower coating coat weights are sufficient and, in addition, even higher web speeds, higher solids contents of the coating color and also lower Ti0 ₂ contents can be achieved. It has been shown that a contour stroke effect can be achieved primarily by volumetric dosing with the profiled doctor rod as a doctor element.

Contour stroke is to be understood to mean that the application medium matches the contours, i.e. follows the mountains and valleys of the fibrous web so that the contour of the paper or cardboard web is completely and evenly covered.

Up to the squeegee element, only so much of the application medium offered is immobilized that there is still enough liquid coating color on the immobilized portion of the coating to contribute to the desired coating weight in order to Enable effect.

So that profile grooves in the grooved doctor rod do not form on the coated web, it can be advantageous to reduce the solids content of the application medium compared to the usual value (application with roller applicator and subsequent doctor blade) so that the application medium flows again after doctoring (metering) can.

In other words, the liquid ink portion is correspondingly large and the application medium (coating color) is still so liquid that the grooves produced can flow well after leveling (metering, doctoring).

If a smooth doctor rod is used, the contour effect described above is less evident when dosing. However, satisfactory results can still be achieved due to the scooping effect of the smooth rod, especially from the valleys of the railway.

The application medium can be somewhat more viscous and does not need to be as fluid as with the profiled doctor rod, because there is no risk of grooves forming here. Sufficient liquid medium is available in the area of the smooth or profiled doctor rod, which means that it does not loll in the so-called solid coat portion.

Another advantage is that there is a better rinsing effect in this area, by means of which particles or deposits can be removed from the paper or cardboard.

According to the invention, it is possible, for example, to scrape or dose the pre-coat and middle coat with the smooth or profiled doctor blade and the rest of the strokes with a doctor blade.

However, it is also possible to scrape or dose all the applied lines with the doctor rod.

It has also been found that the good covering quality can be achieved if the doctoring or metering takes place in a time t since the transfer of the medium to the web which is equal to or less than a time t ₀ .

Here, t ₀ results empirically as: t ₀ = A (CW / K) ² -A 'In the case of a profiled doctor rod:

A = 9.28 m% ² sg ² and A '= 21, 4 x 10 ^"3 s and with a smooth doctor rod or a doctor blade: A = 1 8.86 m ⁴ % ² sg ^{' 2} and A '= 24 , 0 x 1 0 ^"3 s, where

CW = line weight or line application in g / m ²

K = solids content of the application medium in%.

The equation is applicable for (CW / K)>

It has proven to be advantageous if t <0.1 to 0.8 t ₀ , but in particular t <0.1 to 0.5 t ₀ . This thus ensures that a sufficiently large amount of liquid coating color applied remains on the surface of the immobilized layer in order to achieve a further good contour stroke effect when metering by means of a profiled or smooth doctor rod. Overall, this results in good coverage without the risk of squeegee strips. In particular, as already described above, it is avoided that the doctor elements have to intervene in a region of the coating color layer in which the line is already immobilized, so that line defects are avoided.

The invention can be configured particularly advantageously if a pre-metering (excess application) can produce a first immobilized line portion with a contour character in at least one of the lines with a so-called free-jet application unit (nozzle application unit with fountain or free jet acting on the web), whereby the immobilized portion of the application medium follows the contours of the paper or cardboard web.

With the free jet application there is a lower and almost negligible pressure penetration than e.g. in the case of a roller applicator, so that the relevant line is thereby deposited more on the surface of the web, whereas in the roller applicator, due to the significantly higher penetration pressure in the nip between the applicator and counter-roller, the application medium penetration and absorption is different due to the given raw paper formation in the sheet plane. As a result, the contour-line character of the line portion immobilized up to the squeegee element is less pronounced than in the free-jet application unit.

With the free jet applicator, the liquid portion of the applied coating medium, which contributes to the coat weight, is greater than with the roller applicator, which means that the doctor blades described above can be used advantageously for metering. This will make squeegee strips largely avoided. Due to less fiber swelling and back-roughening in paper or cardboard, better smoothness values can be achieved.

There is also less thickening of the coating medium. This means that the medium can be used with higher solids contents (i.e. coating color), which results in a more compact stroke and a higher gloss and smoothness. Another advantage is the lower drying capacity.

In an alternative feasible method (according to claim 85) it is provided that at least one line is metered with a free-jet nozzle application unit instead of a roller application unit and the metering (as a rule final metering) is carried out with a doctor blade.

When metering with the doctor blade, the first contour stroke effect is also provided by the immobilization of the coating medium, but the second contour effect is, as in the first method, according to. Claim 82 provided, not generated. However, a very good leveling effect is achieved. However, the use of the free jet application mechanism favors the contour line character by the uniform immobilization to a considerable extent.

The inventive method according to claim 82 and claim 85 are characterized in that the air knife or air brush known from the prior art can be dispensed with when metering (wiping off an excess amount of the applied medium to the desired coating weight). As a result, all of the associated limits of use described above can be overcome, especially since such aggregates no longer withstand the accuracy requirements with regard to the web widths that are to be produced with ever increasing dimensions. An additional advantage is that higher solids contents of the application medium can be used (for better covering of the web). If air knives were used, the momentum of the outflowing air would be too small to be able to really knife off the corresponding quantities with a high solids content.

In the methods according to claim 82 and claim 85, it does not matter what structure the base paper has, i. H. as it was generated in the wet area of the paper machine.

The paper or cardboard can have been produced in one or more layers (several headboxes and screens or with one or more secondary headboxes or corresponding combinations) or also in one or more layers.

The base paper can be sized at least in one of the layers or layers or contain starch in the mass.

Depending on the requirements placed on the covering quality of the coated material web, according to the invention, impregnating agents and / or strengthening agents (for example starch, synthetic glue with or without pigments) on the surface in addition to the pigment-containing application can be provided at a selectable location within the paper machine to be applied to one or both sides of the web.

This can be done both in the wire section and / or between the wire section and the press section in the press section and / or between the press section and the drying section and / or after this with or without post-drying and / or in front of a winding device as well before the first pigmented stroke application and / or between these in several pigmented applications.

The pigment-containing application according to the invention is to be understood as meaning such a line coating in which the medium per 100 parts of pigments accounts for 4 to 20 (or 25) parts of binder and at least some of which contains plastic binders and / or starch. The pigment-containing application takes place with a relatively high application weight and solids contents. Sizing or impregnation is to be understood as one with starch and / or synthetic glue.

It is particularly advantageous if the web is still smoothed.

As a rule, pre-smoothing will be carried out before the first pigment-containing application (primer) is applied.

Post-smoothing after the top coat is particularly advantageous if very high smoothness and gloss values are to be achieved.

The smoothing itself can be carried out with hard nips, with soft nips or with a wide nip.

For high smoothness and gloss values, it is advantageous if at least one of the two smoothing surfaces that form the nip can be heated.

To further influence the quality, smoothing between the individual order steps is also possible.

The smoothing devices are known per se and consist of at least two opposing smoothing surfaces such. B. Rolling where the web is treated in the nip between two smoothing surfaces. Nip combinations consisting of hard rolls, hard and soft rolls, or only soft rolls can be used.

Such nip combinations can also be arranged in a row. For example, a device with two separate nips, each with a heatable hard and a soft roller, is conceivable.

The combinations mentioned are not intended to limit the scope of protection; further combinations, in particular devices with three or more rollers per unit, are also conceivable. A so-called water scraper smoothing unit can also be used as a smoothing device.

In the case of pre-smoothing in particular, it can be advantageous if the web surface is moistened with water or steam before smoothing in order to achieve even better smoothing effects, e.g. To level the surface and to save volume.

It is also useful as a smoothing device so-called, known Breitnipglättwerke z. B. shoe smoothing or large rollers to ensure a longer nip. As a result, the dwell time of the web in the nip is longer and therefore there is a higher smoothing potential. Wide nip smoothing units can be used advantageously for both pre-smoothing and post-smoothing.

The advantage of the inventions (according to claims 82 and 85) is in summary, in some cases lower application weights, higher solids contents of the application medium, in some cases lower TiO ₂ content in the application medium - speeds of over 600 m / min and higher, treatable

Web widths can be seen as before. Experiments have shown that, with the methods according to the invention, very good covering quality has already been achieved with a line application of 9 g / m ² .

With an application of 15 g / m ² , the coverage was even better than with the air knife coating according to the prior art, which was applied with a similar coating weight.

The invention will be explained in the following using exemplary embodiments with reference to the accompanying drawings. It shows:

1 to 5 different embodiments of systems for

Coating a material web with a primer, a middle coat and a top coat; and

6 to 10 representations of different embodiments of individual devices for coating a material web, in which the application medium forms an immobilized layer between pre-metering and finished metering.

The invention according to claim 82 will be explained below using an example (FIGS. 1 and 2):

In a process for the production of coated folding boxboard, the web B is pre-smoothed in a calender 5 following a drying section not shown in FIG. The web B is then over guide rollers 20 of a first coating station 30 for applying a primer (pigment-containing application) on one side 2, z. B. the bottom of the web B.

The coating station 30 comprises a counter roller 35 which supports the web B. The counter roller 35 is an application unit in the form of a free jet nozzle application unit 40 for direct (directly on the web B) application of the Assigned to the primer. The pre-coat applied in excess is subsequently doctored off with a doctor bar 45, in particular a profiled bar, which is also assigned to the counter roller 35.

The web B is then fed via further guide rollers 20 to a second coating station 30 'for applying the middle coat (pigment-containing application) to the underside of the web (in a direct manner).

Analogously to the coating station 30, the coating station 35 'is constructed and comprises a counter roller 35', free jet applicator 40 'and doctor bar 45'. A top coat (also a pigment-containing application) is applied in a subsequent third coating station 30 "with counter roller 35", free jet applicator 40 "and doctor bar 45". The top coat is also applied directly to the web. Subsequently, the web B is finally smoothed in a further calender 50. The doctor blades 45 'and 45 "are advantageously profiled for volumetric metering.

The doctor rod 45 could also be smooth. Instead of the doctor rod 45, a blade could also advantageously be used, since this ensures high gloss and smoothness.

The coating (also by means of pigmented application) of the other side of the web 3 z. B. Top of the web, as shown in Figure 2, in the same order, also in a direct manner and with identical coating stations, which is why the same reference numerals have been used in the figure.

A further possibility for coating the web 3 instead of the possibility shown in FIG. 2 can also be that a so-called DuoCoater 60, 60 'and 60 "is used. Such a DuoCoater, which is indicated by dashed lines in FIG. 1, is already known from DE G 9409820.4. The DuoCoater is an application device for the indirect application of the medium to the other side of the web (here side 3). The medium is applied to the outer surface of the roller 35, 35 'or 35 ". The applied film is then transported by rotating the roller to a delivery point at which the web to be coated removes the film (ie the application medium).

The following example (Fig. 3 and 4) indicates a possible embodiment of the invention according to claim 85.

Lane 1, i.e. H. Lane side 2 is treated in the same order as given in the first example.

Instead of the doctor rod 45, 45 'and 45 ", a doctor blade 55, 55' and 55" is used here. The remaining components are the same as in FIGS. 1 and 2 and were therefore omitted in FIG. 4 (treatment of the web side 3) for reasons of clarity.

In this example, too, it is possible to coat the other paper side 3 with a DuoCoater, as described in FIG. 1. In Figure 3, the DuoCoater is designated by the reference number 65, 65 ', 65 ".

The coating processes without intermediate drying are shown in FIGS. 1 to 4. However, this should not be a limitation. If necessary, intermediate drying, for example with contactless dryers, can be provided or are interposed in practice.

FIG. 5 shows a further embodiment of a coating system for coating a material web with a primer, a middle coat and a top coat, which essentially corresponds to the embodiment. shapes according to FIGS. 1 and 3 corresponds. Therefore, in FIG. 5, analog parts are provided with the same reference numerals as in FIGS. 1 and 3, but increased by the number 1 00. Furthermore, the embodiment according to FIG. 5 will only be described to the extent that it differs from the embodiment according to FIG. 1 and 3, whose description is otherwise referred to.

The coating system 100 according to FIG. 5 comprises three coating stations or coating devices, namely a coating station 1 30 for applying a primer, a coating station 1 30 'for applying a middle coat and a coating station 1 30 "for applying a top coat.

The material web B entering from the left in the illustration according to FIG. 5 first passes through a smoothing device 105, which in the exemplary embodiment shown is formed by two smoothing rollers. However, other smoothing devices can also be used, for example shoe smoothing units, which have a particularly long nip or action gap for smoothing the material web surface. In order to achieve a better smoothing effect, water or steam D can be sprayed onto the material web B before the smoothing, and preferably on the surface 102 to be coated thereof.

In the area of the first coating station 1 30, the material web is guided around a counter roller 1 35 using web guide rollers 1 20, which is rotatably mounted about its axis A in the direction of arrow P. In the area of the counter roll 1 35, a roll applicator 140 is arranged, which scoops the application medium with a scoop or transfer roller 1 41 from an application medium supply 142 and transports it to the material web surface 102. The application medium is pre-metered in the application gap S formed between the transfer roller 141 and the counter roller 1 35. For the final metering of the application medium, a doctor bar 145 is provided in the first coating station 1 30 according to the invention. It can be both act as a smooth doctor rod as well as a profiled doctor rod.

The structure of the second coating station 1 30 'for applying the middle coat essentially corresponds to that of the first coating station 1 30 for applying the precoat. In contrast to this, however, instead of the roller application unit 140, a free jet application unit 140 'is provided for the pre-metered application of application medium to the surface 102 of the material web B guided around the counter roller 1 35'. The applied application medium is again metered in by means of a doctor rod 145 '.

Also in the third coating station 1 30 "for applying the top coat, the application medium is applied by means of a free jet application unit 140" to the material web B which is guided around the counter roller 1 35 ". In contrast to the pre-and middle coating stations 130 and 130 ' however, in the top coat station, the final metering takes place by means of a doctor blade 1 55 ", since this ensures a particularly high smoothness of the application medium layer.

After leaving the third coating station 1 30 ″, the material web B can again pass through a smoothing device 1 50. Although this is not shown in FIG. 5, the material web B can also be sprayed with water or steam in front of the smoothing device 1 50. It is also possible to heat the smoothing device 1 50, like the rest of the smoothing device 105, to achieve a better smoothing result.

In the three coating stations 1 30, 1 30 'and 1 30 ", application medium of different composition can be used and applied to the material web with different coating weight. However, it is also possible to use application medium of the same composition in at least two of the coating stations. It should also be added that the rear side 1 03 of the material web B can also be coated in the coating stations 1 30, 1 30 'and 1 30 ". For this purpose, for example, application units 1 60, 1 60' and 1 60" can be used for the indirect application of application medium such as are marketed by Voith Sulzer Papiermaschinen GmbH under the name "DuoCoater".

It must also be added that the material web B can be prepared for the application of application medium by applying impregnating agent and / or solidifying agent such as starch, synthetic glue with or without pigments, or can be post-treated after the application medium has been applied. This is only indicated schematically in FIG. 5 for the middle line 1 30 'at 1 38 and 1 39.

6 to 1 0 embodiments of coating stations are shown, on the basis of which various possibilities are to be shown, with which it can be ensured that a layer forms on the material web surface between solids immobilized solids in the application medium applied to the material web surface, which ensures the desired high-quality coverage of the material web. It should be pointed out at this point that the various possibilities described below with reference to FIGS. 6 to 10 can also be used in combination with one another.

6, for example, the distance L which the material web B has to travel between the pre-metering by the free jet applicator 240 around the counter-roller 235 up to the final metering by the doctor blade 255 can be dimensioned so large that the solids of the application medium have sufficient time to form the immobilized layer. For this purpose, the distance L should at least have the value L _min which is given by the following formula: L _min = k ₀ x (k, x CW + k ₂ ) x CW ² xv, where

CW denotes the coat weight to be achieved of the applied application medium layer in g / m ² , v denotes the running speed of the material web in m / min,

k _{0 is} a first constant, the value of which is at least 1, preferably at least 1.5, k, is a second constant, the value of which is -0.03603 x 10 ^"5 m ⁶ min / g ³ , and k _{2 is} a third Is constant, the value of which is 1, 206 x 1 0 ^"5 m ⁴ min / g ² .

In order to optimize the application result, the running distance L between the pre-metering and finished metering can be changed according to FIG. 6, namely by varying the position of the application unit 240 and / or the position of the doctor blade 255 on the circumference of the counter roller 235, which is shown in FIG small arrows V is indicated. This adjustment of the application unit 240 or of the doctor blade 255 can be carried out, for example, under the control of a control unit (not shown) on the basis of detection signals from various sensors. These sensors can be designed to detect line quality parameters such as degree of coverage, smoothness, gloss, degree of whiteness and the like. These parameters can optionally be determined before, during or after the application layer has been dried by a drying device 270 or only in the area of a winding device 272 on the completely coated and dried material web. Accordingly, sensors 274 are provided at four different locations in FIG. 6.

In order to be able to increase the distance L further, according to FIG. 7, a web guide element 320 can be arranged so as to be adjustable in the direction of the double arrow V such that the wrap angle of the material web B is around the opposite roller 335 increased due to this adjustment. In the present case, when the web roller roller 320 is adjusted, the wrap around the counter roller 335 changes in the area of the finished metering by the doctor blade 355. The position of this doctor blade 355 can thus be adjusted over a correspondingly large circumferential angle range.

In the embodiment according to FIG. 8, the material web B wraps around the counter roller 435 in the area of the pre-metering 440 in a first circumferential section, then runs around a deflection roller 476 and finally returns to the counter roller 435 in order to do this in the area of the finished metering 455 in one to wrap around the second circumferential section again. By arranging the deflecting roller 476 at a corresponding distance from the counter roller 435, a sufficient running distance can be provided between pre-metering 440 and finished metering 455 in order to ensure the formation of a layer of immobilized solids on the material web surface. By adjusting the distance of the deflection roller 476 from the counter roller 435, this running distance L can be varied, for example depending on the detection signals of the sensors 274 mentioned above.

In the exemplary embodiment according to FIG. 9, the sufficient running distance between the pre-metering 540 and the finished metering 555 is achieved in that the pre-metering is carried out on a first counter roll 535 and the finished metering 555 on a second counter roll 535 ₂ . The running distance L can be varied by changing the distance between the two rollers 535 and 535 ₂ . Additionally or alternatively, it is possible according to FIG. 10 to provide a web deflection element 676 between the two counter-rollers 635 and 635 ₂ , on which the pre-metering 640 and the final metering 655 take place, the relative position of which can be changed with respect to the two counter-rollers. In order to be able to ensure that not too much of the solids of the application medium are immobilized on the surface of the material web, more precisely to ensure that the smooth or profiled doctor rod or the doctor blade does not interfere with the immobilized layer during the final metering, which results in line defects would, it is further provided according to the invention that the running distance L between pre-metering and finished metering is smaller than a predetermined maximum distance L _max , the value of which is given by the following formula:

L ",, _x = vx [A (CW / K) ² - A '] where v denotes the running speed of the material web in m / min,

CW denotes the coat weight to be achieved of the applied application medium layer in g / m ² , K denotes the solids content of the application medium in%,

A is a first constant, the value of which is 9.28 m% ² sg ^'2 for the profiled doctor rod and is 8.86 m% ² sg ^"2 for the smooth doctor rod and the doctor blade 1, A' is a second constant, the Value for the profiled doctor rod 21, 4 x 10 ^"3 s and for the smooth doctor rod and the doctor blade is 24.0 x 10 ^{" 3} s, and the formula being only for is valid.

Furthermore, various possibilities are shown in FIGS. 6 to 10 to actively accelerate the immobilization of the solids on the surface of the material web. A first possibility consists in heating or / and drying the application medium applied to the material web or the material web itself. For this purpose, for example, the counter roller can be designed to be heatable. This is indicated roughly schematically in FIG. 6 on the counter roller 235 by a heating coil 278. Heated rollers are known in various designs in the prior art. A detailed discussion of heatable rollers is therefore not provided here.

In addition, the heating or drying can be accomplished by irradiation with infrared light or with microwaves. These two types of heating are summarized in FIG. 6 by the serpentine arrows 280. In addition, the material web can be blown with warm air by means of a blower 282 or it can be treated with superheated steam by means of a device 284.

9 also shows various possibilities of immobilization acceleration between pre-metering 540 and finished metering 555, namely a device 586 which treats the material web or application layer with ultrasound, a device 588 which brings the material web B into contact with a high-frequency oscillator, and a device 590, which may correspond to one of the devices 280, 282 and 284 discussed above. A special feature of the devices 586, 588 and 590 is that they can treat the material web B from both of their surfaces simultaneously.

Another group of immobilization accelerators aims to drive the solids contained in the application medium to the surface of the material web by applying pressure. For this purpose, the counter roller 335 according to FIG. 7 is designed as a suction roller with a suction box 392. The effect of this suction box is based on the fact that moisture is removed from the material web on the side facing away from the application layer, so that its capillary suction effect is increased on the application side of the material web. The effect of the suction box 392 can be further enhanced by providing an overpressure box 394 on the order side of the material web B. 10, the deflection roller 676 can also be formed with a suction box 692, and a suction box corresponding to the suction box 394 can also be provided. It must also be added that the operation of the immobilization acceleration devices explained above can also be controlled by the control unit (not shown) on the basis of the detection signals from the sensors 274 according to FIG. 6.

It should also be added that when using a profiled doctor rod for the final metering, the risk that imprints of the profile remain in the final metered application layer can be reduced by using a blowing device which smoothes the surface of the material web. For this purpose, for example, a so-called "air turn" 494 can be used, i.e. a deflection device, which deflects the material web B without contact on a compressed air cushion. However, it is also conceivable to use an air brush or an air knife, which is only used to smooth the surface of the material web. In any case, the blowing device should follow the finished dosage as closely as possible.

In addition to the above-mentioned possibilities of controlling the running distance L and / or the operation of one of the immobilization acceleration devices 278, 280, 282, 284, 392, 394, 586, 588, 590, 692 depending on the detection results of the sensors 274, the temperature and / or the composition of the application medium can also be influenced as a function of these detection results.

Claims

claims

1 . Process for coating a running material web (B), in particular made of paper or cardboard, with a liquid or pasty application medium, the application medium being applied directly or indirectly, pre-metered to the material web (B) and then being metered or / and leveled to the desired application weight , characterized in that the final dosing and / or leveling takes place at the earliest after a time t _min , which is given by the following formula: t _min = k ₀ x (k, x CW + k ₂ ) x CW ² , where

CW denotes the coat weight to be achieved of the applied application medium layer in g / m ² , k _{0 is} a first constant, the value of which is at least 1, preferably at least 1.5, k, is a second constant, the value of which is -0.03603 x 1 0 ^{"is 5} m ⁶ min / g ³ , and s _{2 is} a third constant, the value of which is 1, 206 x 1 0 -5 m min / g ² .

2. The method according to claim 1, characterized in that the value of the first constant k _{0 is} at least 2, preferably at least 3, more preferably at least 4.

3. The method according to claim 1 or 2, characterized in that the time t between pre-metering and finished metering is adjustable.

4. The method according to claim 3, characterized in that one detects at least one property of the finished metered application medium layer, such as covering quality, smoothness, gloss, whiteness and the like (by 274) and the time t between pre-metering and finished metering depending on the

Results of acquisition.

5. The method according to claim 4, characterized in that one detects the at least one property of the metered application medium layer on the still moist application medium layer.

6. The method according to claim 4, characterized in that one detects the at least one property of the finished metered application medium layer during its drying.

7. The method according to claim 4, characterized in that the at least one property of the metered application medium layer is detected on the dried application medium layer.

8. The method according to claim 4, characterized in that one detects the at least one property of the finished metered application medium layer on the winding device (272).

9. The method according to any one of claims 1 to 8, characterized in that the material web (B) wraps around a support element, preferably a support roller (235; 435), at least on part of its circumference and that both the pre-metering (240; 440) as also the finished dosing (255; 455) in one of the material web (B) wrapped circumferential portion of the support element (235; 435).

0. The method according to any one of claims 1 to 8, characterized in that the material web in the area of the pre-metering (540; 640) around a support element, preferably a support roller (535 ^ 635,), and in the area of the finished metering (555; 655) is guided around a further support element, preferably a further support roller (535 ₂ ; 635 ₂ ).

1 . Method according to claim 9 or 10, characterized in that the material web (B) is deflected between pre-metering (440; 640) and final metering (455; 655) by at least one intermediate guide element, preferably at least one deflecting roller (476; 676).

2. The method according to the preamble of claim 1 and, if desired, the characteristic of one of claims 1 to 1 1, characterized in that the immobilization of the medium applied to the material web (B) during its movement from the

Pre-dosing actively accelerated for final dosing.

3. The method according to claim 12, characterized in that the applied layer is heated and / or dried (by 280, 282, 284).

4. The method according to claim 1 2 or 1 3, characterized in that the material web is heated (by 278).

1 5. The method according to claim 1 3 or 1 4, characterized in that the applied layer or / and the material web is irradiated with infrared light (280).

1 6. The method according to any one of claims 1 3 to 1 5, characterized in that the applied layer or / and the material web is irradiated with microwaves (280).

1 7. The method according to any one of claims 1 3 to 1 6, characterized in that heated air (282) is supplied to the applied layer and / or the material web.

1 8. The method according to any one of claims 1 3 to 1 7, characterized in that steam (284) is fed to the applied layer and / or the material web.

1 9. The method according to any one of claims 1 3 to 1 8, characterized in that the material web and / or the applied layer is brought into contact with at least one heatable element, preferably a heatable roller (235/278) or a heatable belt .

20. The method according to claim 1 9, characterized in that one has a support element, preferably a support roller (235) around which the material web (B) in the region of

Predosing (240) is guided around, heated (278).

21. Method according to claim 1 9 or 20, characterized in that a web guiding or / and treatment element (676), preferably a roller, provided between pre-metering (640) and finished metering (655) is heated (678).

22. The method according to any one of claims 1 2 to 21, characterized in that the material web (B) from the opposite side of the order side with a vacuum (392).

23. The method according to claim 22, characterized in that a support element (335), preferably a support roller, around which the material web (B) is guided in the region of the pre-metering (340), is equipped with a suction device (392).

24. The method according to claim 22 or 23, characterized in that between the pre-metering (640) and the final metering (655) at least one with a suction device (692) equipped web guide or / and treatment element (676), preferably a deflection roller a suction box.

25. The method according to any one of claims 1 2 to 24, characterized in that overpressure (394) is applied to the material web (B) from the order side.

26. The method according to any one of claims 1 2 to 25, characterized in that the material web and / or the applied layer is exposed to vibrations (586, 588).

27. The method according to claim 26, characterized in that the material web and / or the applied layer is irradiated with ultrasound (586).

28. The method according to claim 26 or 27, characterized in that the material web and / or the applied layer is brought into contact with a vibration device (588) which can preferably be operated at high frequency.

29. The method according to any one of claims 1 2 to 28, characterized in that the intensity of the active influence on the immobilization of the applied layer on the material web (B) is adjustable.

30. The method according to claim 29, characterized in that at least one property of the final metered application medium layer, such as covering quality, smoothness, gloss, whiteness and the like, is detected (274) and the influencing intensity is set as a function of the detection result.

31 Method according to one of claims 1 to 30, characterized in that the final metering takes place by means of a smooth or profiled doctor rod (145, 1 45 ') or a doctor blade (1 55 ").

32. The method according to the preamble of claim 1, the characterizing part of claim 31 and, if desired, the characterizing part of one of claims 1 to 30, characterized in that the final dosing and / or leveling takes place at the latest after a time t _max , which is given by the following formula is: t _max = A (CW / K) ² - A 'where CW denotes the coat weight to be achieved of the applied application medium layer in g / m ² , K denotes the solids content of the application medium in%, A is a first constant, the value of which is 9.28 m% ² sg ² for the profiled doctor rod and 8.86 m ⁴ % ² sg ^'2 for the smooth doctor rod and the doctor blade 1, A' is a second constant, the Value for the profiled doctor rod 21, 4 x 10 ^'3 s and for the smooth doctor rod and the doctor blade is 24.0 x 10 ^{~ 3} s, and the formula being only for

CW / K ≥ jÄTA ^{1 is} valid.

33. The method according to claim 32, characterized in that the final metering and / or leveling takes place at the latest after a time t for which 0.1 t _max <t <0.8 t _max , preferably 0.1 t _max <t <0 .5 t _max applies.

34. The method according to any one of claims 1 to 33, characterized in that a plurality of application layers are applied to the material web (B), for example in the form of a pre-coat (1 30), a middle coat (1 30 ') and a top coat (1 30 ").

35. The method according to claim 34, characterized in that at least two of the application layers are formed from application medium of different composition.

36. The method according to claim 34 or 35, characterized in that at least two of the application layers are formed from application medium of the same composition.

37. The method according to any one of claims 34 to 36, characterized in that at least one of the application layers is formed from an application medium which has a solids content which is at least 2% to 5% lower than at least one other application layer, the solids content of these at least one other Application layer is around 50% to 73%.

38. The method according to any one of claims 1 to 37, characterized in that the application medium layer or at least one application layer is formed from an application medium which, when using a profiled doctor rod, has a viscosity of <500 mPas, preferably 30 mPas to 250 mPas, at Using a smooth doctor rod has a viscosity of <2500 mPas, preferably 300 mPas to 1000 mPas, or when using a doctor blade has a viscosity of <4000 mPas, preferably 300 mPas to 1500 mPas, the indicated viscosities according to Brookfield 100 can be determined.

39. The method according to any one of claims 1 to 38, characterized in that the application medium layer or at least one application layer by means of a roller application unit (1 40), by means of an SDTA application unit, by means of a free jet application unit (1 40 ') or by the film coating method is applied.

40. The method according to any one of claims 1 to 39, characterized in that the application medium layer or the last application medium layer (at 1 30 ") is metered in by means of a doctor blade (1 55").

41. Method according to one of claims 1 to 40, characterized in that the material web by adding impregnating agent and / or strengthening agent such as starch, synthetic chemical glue with or without pigments, for which application medium is prepared (1 38).

42. The method according to any one of claims 1 to 41, characterized in that the material web is aftertreated after the application of application medium by adding impregnating agent and / or solidifying agent such as starch, synthetic glue with or without pigments (1 39).

43. The method according to any one of claims 1 to 42, characterized in that the material web is smoothed before the application of application medium (105).

44. The method according to any one of claims 1 to 43, characterized in that the material web is smoothed after the application of application medium (1 50).

45. The method according to claim 43 or 44, characterized in that the smoothing is carried out with hard nips and / or with soft nips and / or with a wide nip.

46. The method according to any one of claims 43 to 45, characterized in that at least one of the two smoothing surfaces forming the respective nip is heatable.

47. The method according to claim 43 or 44, characterized in that the application medium layer is smoothed by means of a blowing device (494).

48. The method according to any one of claims 43 to 47, characterized in that the material web is moistened with water or steam (D) before smoothing.

49. The method according to any one of claims 1 to 48, characterized in that the composition and / or the temperature of the application medium and / or the temperature of the material web is adjusted.

50. The method according to claim 49, characterized in that at least one property of the finished metered application medium layer, such as covering quality, smoothness, gloss, whiteness and the like, is detected (274) and the composition or / and the temperature of the application medium or / and the

Material web temperature depending on the detection result.

51. Device for coating a running material web (B), in particular made of paper or cardboard, with a liquid or pasty one

Medium comprising an applicator (240) for directly or indirectly, pre-dosed application of a layer of the liquid or pasty medium onto the material web, wherein the applicator unit (240) in Laufrich- o tung seen the material web is angeord ^¬ net at a first position, and a device (255) for final metering and / or leveling of the applied layer at a second position downstream of the first position in the running direction of the material web, 5 which has a distance L from the first position, characterized in that the second position from the first position has a minimum distance L _min , which is given by the following formula:

L _min = k ₀ x (k, x CW + k ₂ ) x CW ² xv, 0 where

CW denotes the coat weight to be achieved of the applied application medium layer in g / m ² , v denotes the running speed of the material web in m / min, k _{0 is} a first constant, the value of which is at least 1, preferably at least 1.5, k, is a second constant, the value of -0.03603 × ^{10 5} m ⁶ min / g ³ , and k _{2 is} a third constant whose value is 1, 206 x 10 ^"5 m ⁴ min / g ² .

52. Apparatus according to claim 51, characterized in that the value of the first constant k _{0 is} at least 2, preferably at least 3, more preferably at least 4.

53. Apparatus according to claim 51 or 52, characterized in that the distance of the second position from the first position is adjustable (V).

54. Apparatus according to claim 53, characterized in that for adjusting the distance of the second

Position from the first position, the position of the first position and / or the position of the second position is adjustable (V).

55. Apparatus according to claim 53 or 54, characterized in that a sensor device (274) for

Detection of at least one property of the finished metered application medium layer, such as covering quality, smoothness, gloss, whiteness and the like, is provided, as well as a control unit which adjusts the distance of the second position from the first position as a function of the detection result.

56. Device according to claim 55, characterized in that the sensor device (274) in the running direction of the material web (B) in front of the drying device (270) or in the region of the drying device (270) or after the drying device (270) or on the winding device (272) is arranged.

57. Device according to one of claims 51 to 56, characterized in that the material web (B) a support element (235; 435), preferably a support roller, wraps around at least part of its circumference and that both the first position and the second position are arranged within a circumferential section of the support element which is wrapped by the material web.

58. Device according to one of claims 51 to 56, characterized in that the material web (B) in the region of the first

Position around a support element (535,; 635,), preferably a support roller, and in the region of the second position around a further support element (535 ₂ ; 635 ₂ ), preferably a further support roller.

59. Apparatus according to claim 57 or 58, characterized in that between the first position and the second position at least one intermediate guide element (476; 676), preferably at least one deflection roller, is provided for deflecting the material web.

60. Device according to the preamble of claim 51 and, if desired, according to the characterizing part of one of claims 51 to 59, characterized in that a device for accelerating the immobilization of the applied medium on the material web is provided between the first position and the second position.

61. Device according to claim 60, characterized in that the immobilization acceleration device comprises a device for heating or / and drying the applied layer or / and for heating the material web.

62. Device according to claim 61, characterized in that an infrared radiation device (280) is provided.

63. Apparatus according to claim 61 or 62, characterized in that a microwave heating device (280) is provided.

64. Device according to one of claims 61 to 63, characterized in that a convection heating device (282) is provided.

65. Device according to one of claims 61 to 64, characterized in that a device (284) is provided for heating or / and drying the applied layer or / and the material web by means of steam.

66. Device according to one of claims 61 to 65, characterized in that at least one heatable element (235/278) which can be brought into contact with the material web and / or the applied layer, preferably a heatable roller or a heatable band, is provided.

67. Device according to claim 66, characterized in that the material web in the region of the first position is guided around a support element (235), preferably a support roller, which is heatable (278).

68. Apparatus according to claim 66 or 67, characterized in that between the first position and the second position, a web guide or / and treatment element (676), preferably a roller, is provided, which is heatable (678).

69. Device according to one of claims 60 to 68, characterized in that the immobilizing acceleration device comprises a suction device (392; 692).

70. Apparatus according to claim 69, characterized in that the material web is guided in the region of the first position around a support element (335), preferably a support roller, which is equipped with a suction device (392).

71. Apparatus according to claim 69 or 70, characterized in that between the first position and the second position at least one web guide or / and treatment element (676) equipped with a suction device (692), preferably a deflection roller with a suction box, is provided.

72. Device according to one of claims 60 to 71, characterized in that the immobilization acceleration device comprises an overpressure device (394).

73. Device according to one of claims 60 to 72, characterized in that the immobilizing acceleration device comprises a vibration device (586, 588).

74. Device according to claim 73, characterized in that the vibrating device comprises an ultrasonic emitting device (586).

75. Device according to claim 73 or 74, characterized in that the vibrating device is a vibrating device (588) which can be brought into contact with the material web and / or the applied layer, preferably can be operated at high frequency.

76. Device according to one of claims 60 to 75, characterized in that the power of the immobilization acceleration device is adjustable.

77. Apparatus according to claim 76, characterized in that a sensor device (274) is provided for detecting at least one property of the finished metered application medium layer, such as covering quality, smoothness, gloss, whiteness and the like, and a control unit which depends on the performance of the immobilization acceleration device from the detection result.

78. Device according to one of claims 51 to 77, characterized in that a roller applicator (1 40), an SDTA-5 applicator, a free jet applicator (140 ') or a film applicator is provided for applying the application medium to the material web.

79. Device according to one of claims 51 to 78, 0 characterized in that a smooth or profiled doctor rod (1 45) or a doctor blade (1 55 ') is provided for final metering of the application medium layer.

80. Method according to the preamble of claim 1, the characterizing part of claim 79 and, if desired, the characterizing part of one of claims 51 to 78, characterized in that the second position has a maximum distance L _max from the first position, which is given by the following formula :

L _max = vx [A (CW / K) ² - A '] where v denotes the running speed of the material web in m / min,

A is a first constant, the value for the profiled doctor rod is 9.28 m ⁴ % ² sg ^"2 and for the smooth one

Doctor blade and the doctor blade 1 is 8.86 m ⁴ % ² sg ^"2 , A 'is a second constant, the value of which is 21.4 x 10 ^{" 3} s for the profiled doctor rod and 24.0 for the smooth doctor rod and the doctor blade x 10 ^'3 s, and the formula being only for is valid.

81. A method according to claim 80, characterized in that the second position from the first position having a distance L, for the 0, 1, L _max <L <L _max 0.8, preferably 0, 1, L _max <L <0, 5 L _max applies.

82. Method for producing a coated web of material, in particular from paper or cardboard, with the following steps: Production of a fibrous web (hereinafter called web) with a headbox and a subsequent wire section in one

Paper machine

Dewatering by mechanical pressing and thermal drying of the web

Applying liquid or pasty medium to at least one side of the web for sizing or impregnation and / or

Line coating

Winding up the web with a winding device, characterized in that at least one pigment-containing application (line) is applied to the at least one side of the web, this application being metered after a time t since the transfer of the medium with a smooth or profiled doctor rod, where applicable : t ≤ t ₀

Here t ₀ = A (CW / K) ² -A 'with

A = 9.28 m% ² sg ^"2 and A '= 21, 4 x 10 ^{" 3} s for the profiled doctor rod and

A = 1 8.86 m% ² sg ^'2 and A' = 24.0 x 10 ^"3 s for the smooth doctor rod, CW = coating weight in g / m ²

K = solids content of the application medium in% valid for

83. The method according to claim 82, characterized in that the at least one or all (in excess) applied lines are applied with a free jet applicator.

84. The method according to claim 82, characterized in that the last is metered with a doctor blade in several strokes.

85. A process for producing a coated web of material, in particular from paper or cardboard, comprising the following steps:

Production of a fibrous web with a headbox and a subsequent wire section in a paper machine - dewatering by mechanical pressing and thermal

Drying the web

Application of liquid or pasty medium on at least one side of the web for impregnation or sizing and / or pigmentation and / or line coating - winding up the web with a winding device, characterized in that at least one pigment-containing application (line ) is applied, this application being applied with a free jet nozzle applicator and metering with a doctor blade after a time t after transfer of the medium, where: t <to where t ₀ = A (CW / K) ² -A 'with A = 1 8.86 m ⁴ % ² sg- ² and A '= 24.0 x 1 0 ^"3 s CW = coat weight in g / m ²

K = solids content of the application medium in% valid for (CW / K)> A / A '.

86. The method according to claim 82 or 85, characterized in that the pigment-containing application (line) is carried out in the form of a pre-and / or middle line and / or a top coat.

87. The method according to claim 86, characterized in that one of the lines is carried out several times, the application medium having different or the same composition.

88. The method according to claim 82, characterized in that at least one pigment-containing application (line) is applied with a roller applicator.

89. The method according to claim 82 and 85, characterized in that at least one pigment-containing application (line) is applied with an application unit with a short exposure time of the application medium to the web until dosing by means of the doctor element (doctor rod, doctor blade) (SDTA).

90. The method according to one or more of claims 82-89, characterized in that at least one of the coats is applied with such an application medium which has a solids content which is at least 2-5% lower than the one or the other (normally customary) coats, being the solids content of these others

Strokes is around 50 - 73%.

91. Method according to one or more of claims 82-90, characterized in that at least one of the coats is applied with an application medium which has a Brookfield 100 coating color viscosity of <500 mPas, preferably 30-250 mPas, when using a profiled rod, or has a coating color viscosity of <2500 mPas, preferably 300-1000 mPas when using a smooth doctor rod and <4000 mPas, preferably 300-1,500 mPas when using a doctor blade.

92. The method according to any one of claims 82 or 85, characterized in that impregnating agents and / or solidifying agents (for example starch, synthetic glue with or without pigments) are added in bulk before the pigment-containing application.

93. The method according to any one of claims 82 or 85, characterized in that in addition to the pigment-containing application on at least one of the two web sides, a surface treatment in the wire section and / or between the wire section and the press section is carried out with impregnating agent and / or solidifying agent.

94. The method according to any one of claims 82 or 85, characterized in that in addition to the pigment-containing application on at least one of the two web sides, a surface treatment in the press section and / or between the press section and the dryer section is carried out with impregnating agent and / or with hardening agent.

95. The method according to any one of claims 82 or 85, characterized in that in addition to the pigment-containing application on at least one of the two web sides, a surface treatment with impregnating agent and / or with solidifying agent in the dryer section and / or after this is carried out with or without post-drying.

96. The method according to any one of claims 82 or 85, characterized in that in addition to the pigment-containing application on at least one of the two sides, a surface treatment with impregnating agent and / or solidifying agent is carried out before a winding device with or without post-drying.

97. The method according to any one of claims 82 or 85, characterized in that a surface treatment with impregnating agent and / or solidifying agent is carried out before the first pigment-containing application and / or between the individual pigment-containing applications carried out multiple times.

98. The method according to any one of claims 82 or 85, characterized in that the first and / or second and / or a further pigment application (line) in the area of the headbox and / or in the wire section and / or between wire section and press section and / or in the press section and / or between press section and dryer section and / or inside or after the dryer section is applied to the web .

99. The method according to one or more of claims 82-98, characterized in that the web is smoothed before the pigment-containing application, the smoothing being carried out with hard nips and / or with soft nips and / or with a wide nip, and at least one of the two smoothing surfaces forming the respective nip is heatable.

100. The method according to one or more of claims 82-99, characterized in that the web between each pigment-containing

Order and / or after this is smoothed.

1 01. A method according to claim 97 or 98, characterized in that the web is moistened with water or steam before smoothing.

102. The method according to any one of claims 82 or 85, characterized in that t <0, 1 to 0.8 t ₀ , but in particular <0, 1 to 0.5 t ₀ .