EP2576900B1 - Method for producing a coated multilayer fibrous web - Google Patents

Description

The invention relates to a method for producing a coated, multi-layer fibrous web, in particular packaging paper or board web, in which first a stream is produced, which successively at least one headbox, at least one wire section to form a multilayer fibrous web, a press section, a dryer section with dryer groups and then fed to a reel.

The document WO2006 / 024695A1 discloses a process unit with metal strip for smoothing paper webs.

The multilayer coating of paper or cardboard is the subject of the document EP1249533A1 ,

Cardboard and packaging papers are usually dried in their production in the paper machines with drying cylinders of a single-row and / or double-row dryer section. In this case, optional suction elements, especially for web stabilization available. A disadvantage is the high space requirement for such dryer sections and also to view the limited drying capacity. Especially with regard to the required, ever-increasing machine speeds, the drying zones must be formed longer based on the total machine length.

The smoothness of the paperboard or packaging paper to be produced is usually produced in the production of paperboard using conventional calenders, such as hard-nip calenders with high maximum pressures and short residence times of the fibrous web in the nip. A disadvantage of this technology, the thickness loss of the web affects. For other conventional smoothing processes with SoftNip calenders soft roll covers are used to increase the residence time in the nip. This is disadvantageous, the slight increase in smoothness and the volume loss. Other conventional smoothing methods, such as nip calendering or shoe straightening, use soft covers of the unheated roll. The disadvantage here is also a slight increase in smoothness with simultaneous loss of volume.

In most cases, the fibrous web or packaging paper or board web is also painted with a pigment coating. This achieves whiteness, smoothness, gloss and opacity of the web. Also, the printability of the web material is thereby increased, whereby it can serve as an information and advertising medium.

The printing is done in addition to digital printing, especially in the form of offset printing and gravure printing.

The fibrous web is painted on the cover side at least once. The reverse side may remain uncoated, or will also be painted at least once. In this case, coating amounts per side of up to 80g / m ^{2 are} applied. The application has hitherto been carried out with conventional coating units, such as film presses, coaters with roller application (LDTA applicators with long exposure time of the coating medium), coater with free-jet nozzles, or with commissioned work with a short residence time of the medium on the web (so-called Short Dwell Time Applicators or SDTA ).

The disadvantage is that only a limited application capacity and thus poor coverage and opacity of the fibrous web or packaging paper and board web can be achieved with these mentioned conventional order types.

It is therefore an object of the invention to provide a method for producing a coated, multi-layer fibrous web, in particular packaging paper or board web, which does not have the disadvantages of the prior art.

The object of the invention is achieved by a method according to the features of claim 1.

According to the invention, the multi-ply fibrous web is pre-smoothed with a belt calender within or after a post-dryer section and then the top layer of the fibrous web is coated with a white pigmented coating layer by means of a curtain applicator and then dried and that in the press section (II ) At least a smooth roller is used, at least on the top layer acts.

The inventors have found that with the specified pre-smoothing method,

i.e. With a belt calender a smoother paper is produced than before, so what was done either without pre-smoothing or with other calenders. Strip smoothing according to the invention leads to better coverage of the white line layer subsequently applied with the curtain applicator. Due to the high smoothness of the web there is a much lower risk of demolition of the curtain during coating, even with low coating weights or low viscosity of the application medium used in curtain coating and high web speeds. This is considered a particular advantage of the invention. Incidentally, the smoothness of the web need only be present on one side before the coating, because the product resulting from the fibrous web produced is preferably only printed on one side.

The band used in the pre-smoothing of the fibrous web consists of more than 70% of plastic. There is a temperature of more than 80 ° C. at the strip surface in contact with the fibrous web.

Another advantage is that due to the white pigment-containing curtain coat, which is indeed very uniform and well-covering, only a low basis weight of the white and expensive fiber layer (top layer) is needed. This saves expensive raw materials without the lower fiber layers showing through and without the print quality deteriorating.

The method according to the invention offers the possibility of producing the fibrous web in at least two layers, preferably at least three layers, namely backsheet, middle layer, top layer, depending on the desired application. For the top layer white or bleached and / or deinked and / or wood-free fibers are provided, which are expensive. It is therefore all the more advantageous to be able to save these substances to a large extent because the described white coating layer is applied to the cover layer with the aid of a curtain coating. In certain cases (eg with white multiple lines) even the white cover layer can be completely replaced with the white line layer.

A curtain coater applies the application medium in a ratio of 1: 1, ie without excess to the moving fibrous web in its production process. On the web so only the amount of coating material or pigment-containing application medium is applied, which should also remain there. This saves the doctoring and the corresponding squeegee devices. The at least one coating layer can be applied with a single- or multi-layered curtain applicator in the form of a slot die or a so-called slide die.

It is expedient if a condensation press drying is provided within the pre-drying section. This could also be done after the drainage in the press section and / or in a post-dryer section. This offers the advantage of an increased evaporation rate of greater than 40 kg / m ² h and the smoothing of the fibrous web. This type of drying, with which conventional drying cylinders can be partially saved, should take place in a range in which the web has a solids content of more than 50% to about 90%, preferably more than 55%. At least such drying should therefore, as stated, preferably be carried out within the pre-drying section, and it is also conceivable to provide this also in the after-dryer section. The mentioned high evaporation rate and smoothness is due to the fact that the fibrous web is guided with its one side via a preferably steam-heated cylinder and with its other side on a sieve and an overlying impermeable fabric. In this case, a contact pressure with respect to the cylinder is exerted in this section with a, a part of the outer circumference of the cylinder overlapping the pressure hood. A particular advantage is to be considered an improved heat transfer from the steam room of the drying cylinder to the fibrous web. In addition, one achieves an increase in the drying speed, without machine extensions are necessary. The paper strength and the surface properties are increased despite the possible savings of raw fibers. Also the order of strength can be reduced, in some cases even completely saved.

The production method according to the invention can be formed even more advantageously by feeding a fines into the headbox at the beginning of the production process for the formation of the cover layer of the multi-ply fibrous web. This achieves a very smooth cover layer, which forms a particularly good basis for later coating layer and which achieves a very uniform coverage of the fibrous web.

Incidentally, the head box can be designed as a perforated roller headbox or as a hydraulic headbox. Optionally, at least one headbox is equipped with dilution water control. The advantage of this is that a basis weight profiling without adjustment of the lip and thus the fiber orientation is achieved. Preferably, the central layer is equipped with a dilution water control with the advantage that the basis weight cross profile of the entire board web can be influenced by the position with the largest proportion of the total weight (center layer) the strongest. It is also conceivable a multi-layer casserole that is fed with different streams.

In the wire section all known form combinations can be used. Preference is given to the use of wire mesh, but also combinations of wire mesh and hybrid formers, such as the marketed by the company of the Applicant Duo D or Duo DK as combinations of at least one Gapformern and at least one wire screen use. It is advantageous if the said former is equipped with a Siebschütteleinrichtung, for example, with the marketed by the company of the Applicant Duo Shake. In the case of multi-layer concepts, this should preferably be provided for the layer with the highest layer basis weight, such as the middle ply.

For example, a tandem NipcoFlex press (TNFP) with offset press, which is quadruple felted and / or a press unit, consisting for example of a suction press roll in the first nip, a NipcoFlex press in the second nip and find an offset press in the third nip use. The press concepts can be designed with closed or open web guide. The stiffening, ie the support frames for the presses can be performed as so-called cantilevers. It is also possible to use seamed or even seamless felts in the press section. Dry contents of up to 57% can be achieved with the mentioned press concepts.

In the context of the invention, at least one smooth roller is used in the press section, which acts at least on the cover layer. This can be done with the help of a known tandem press with three felts and a smooth roller, which is usually arranged below or with a so-called offset press, in which a nip is performed without any clothing. This measure also contributes to a smoother cover layer, which in turn can be coated more uniformly.

To increase the efficiency of the process, it is expedient to carry out a per se known impingement drying directly after the press section and before the first heated drying cylinder of the dryer section. This can increase the dry content of the web and reduce the risk of demolition in the dryer section. Thus, a speed of greater than 1000m / min, in particular greater than 1200m / min is possible.

With regard to the quality of the packaging paper or board web, it may also be advantageous if, in addition to the strip smoothing, the web is subjected to a condensation press smoothing after the predrying and before a subsequent coating with the at least one white coat layer. This smoothing process leads to even higher smoothness values. The condensation press smoothing works in a similar way to the condensation press drying, whereby the fibrous web is passed over a heated cylinder and brought into direct contact with a metal belt running over the cylinder, above which a pressure hood is located. A sieve or a clothing is hereby not available.

In the condensation press drying and also in the condensation press smoothing preferably the cylinder (drying cylinder or Yankee cylinder) is preferably heated in each case with steam, wherein the cylinder surface reaches a temperature between 60 and 250 ° C, preferably 130 to 190 "C.

The method according to the invention can be further expedient if, following the curtain coating, the same side of the web is coated a second time with a conventional coating unit, such as a directly applied blade coater, then the other side also coated with a conventional coater and then dried with dryers becomes.

With regard to the quality of the fibrous web produced, it is when it is smoothed before reeling, so within a final group of the manufacturing machine.

This calender has a heating roller, which is provided with a plastic jacket which has a metallic coating with a thickness of <200 .mu.m. This achieves an enormous increase in smoothness and an even better gloss.

Subsequently, the fibrous web of a cooling group and then the reeling can be supplied.

With the method according to the invention it is possible a coated board, in particular (FBB or folded box board or chromo or Chromoersatzkarton) or LPB (liquid packaging board or liquid carton) or coated packaging paper, in particular CWTTL (coated white top testliner) or CWTKL (coated white top kraft liner) with at least two layers produce.

According to a first variant, it is possible that the cardboard or the paper three Layers, which consist of a fiber cover layer of bleached pulp, a middle layer of wood-containing raw material and / or recycled paper and a supine layer of bleached pulp or a mixture of bleached pulp with shares of wood-containing raw material, which also shares in waste paper material are added ,

According to a second variant, it is possible that the cardboard or the paper has four layers. In addition, there is a protective layer between the top and middle layers. This protective layer consists either of waste paper pulp or a mixture of waste paper pulp and wood-containing raw material.

The blanket is made of 100% bleached pulp, depending on the quality of the box, and is painted at least once. The insert, i. the middle days are light and consist of either 100% wood-containing raw material or shares of waste paper pulp are added.

The back is bright and consists of either 100% bleached pulp or a blend of bleached pulp with levels of wood-containing raw material. It can also be added to the back shares of waste paper pulp. The back can be optionally painted with at least one stroke. If used paper pulp can be optionally deinked in stock preparation. But there are also machines with four-layer concepts possible. Here, in addition to the three layers described, there is still a protective layer between the in or middle layer and the blanket. This protective layer consists either of waste paper pulp or of a mixture of waste paper pulp and wood-containing raw material.

Depending on the quality of the raw material used and the application rate, a distinction is made between qualities with the following abbreviation, with the number 1 indicating the variety with the highest quality. With the grades GG the coating is enriched with plastics. variety coat weight GC1 Painted > 18 g / m ² Better raw material than GC2 and GC3 GC2 Painted > 12 g / m ² GG1 cast coated Back woodfree GG2 cast coated Back bright

The following table gives an overview of which combinations of raw materials are possible. In proportion, all mixtures are possible. raw material Top Ply Undertop Ply Middle Ply Back Ply recycled OCC X Deinked ONP / OMG X X X White Shavings X X X Virgin Fiber GW, TMP, CTMP, BTCMP X X X LUKP, NUBK X X X LBKP, NBKP X X X

• LUKP unbleached hardwood kraft pulp / ungebleichter Kurzfaser-Kraftzellstoff
• NUKP unbleached softwood kraft pulp / ungebleichter Langfaser-Kraftzellstoff
• LBKP bleached hardwood kraft pulp / gebleichter Kurzfaser-Kraftzellstoff
• NBKP bleached softwood kraft pulp / gebleichter Langfaser-Kraftzellstoff
• OCC old corrungated container / alte Wellpapier-Verpackungen
• GW ground wood / Holzschliff
• TMP thermo mechanical pulp / thermo-mechanischer Holzstoff
• CTMP chemical thermo mechanical pulp / chemisch vorbehandelter thermo-mechanischer Holzstoff
• BCTMP bleached chemical thermo mechanical pulp / gebleichter chemisch vorbehandelter thermo-mechanischer Holzstoff
• ONP old news print / alte Zeitungen
• OMG old magazines / alte Zeitschriften
• Deinked / so aufbereitet, dass Druckfarben und andere Störstoffe entfernt sind
• White shavings / weiße Späne, d.h. unbedruckte Papierabfälle zum Beispiel Randbeschnitt aus Druckereien
• MW mixed waste paper / gemischtes Altpapier
• Virgin Fibre / Frischfaser
• Recycled / Altpapier
• Top Ply / Decklage oder Decke
• Undertop Ply / Schonschicht
• Middle Ply / Mittellage oder Einlage
• Back Ply / Rückenlage oder Rücken

Where:

• LUKP unbleached hardwood kraft pulp / unbleached short fiber kraft pulp
• NUKP unbleached softwood kraft pulp / unbleached long fiber kraft pulp
• LBKP bleached hardwood kraft pulp / bleached short fiber kraft pulp
• NBKP bleached softwood kraft pulp / bleached long fiber kraft pulp
• OCC old corrungated container / old corrugated paper packaging
• GW ground wood / groundwood
• TMP thermo mechanical pulp / thermo-mechanical pulp
• CTMP chemical thermo mechanical pulp / chemically pretreated thermo-mechanical pulp
• BCTMP bleached chemical thermo mechanical pulp / bleached chemical pretreated thermo-mechanical pulp
• ONP old news print / old newspapers
• OMG old magazines / old magazines
• Deinked / processed so that printing inks and other contaminants are removed
• White shavings / white shavings, ie unprinted paper waste, for example, edge trim from printing shops
• MW mixed waste paper / mixed waste paper
• Virgin fiber / fresh fiber
• Recycled / waste paper
• Top Ply / top layer or blanket
• Undertop Ply / Schonschicht
• Middle Ply / middle layer or insert
• Back Ply / supine or back

As standard for recycled paper, the following are eligible: MW OCC NP White Shavings American Standard (ISRI) ISRI 1,2 ISRI 11:12 ISRI 6,7 ISRI 28,30,31 European Standard (CEPAC) A2, A4 A5 E12 C15, C16, C17 DIN / ISO / ONORM B12, B19 W52, W41 R12, O14, Q14

Folding boxboard is cardboard with a grammage in the range of 160 - 500 g / m ² with the following characteristics carton features unit values measurement method Specific bending stiffness CD Nmm until 100 L & M DIN 53121, 1996-1912; DIN 53121, 1996 to 12) Specific bending stiffness MD Nmm up to 200 Roughness blanket microns <10 PPS-10S ISO 8791-4, 1992-04 Roughness back microns <15 Gap strength MD Y / m ² up to 800 J / m ² Scott slump strength tester TUM 403, 1991 Splitting resistance CD Y / m ² up to 800 J / m ²

It has to be added that five layer concepts are also suitable, each with a protective layer between the insert and the outer layers.

The protective layer can consist of 100% recovered paper or optionally with shares of wood pulp. In principle, any mixing ratio is conceivable.

Depending on the quality of the box, the top layer may consist of 100% bleached pulp or 100% recycled paper pulp. But it is also possible the Make cover layer of a mixture of bleached pulp and waste paper pulp. The top layer can also be only slightly woody, although the wood pulp may be bleached or may be wood-free. The ceiling should always be painted.

The insert usually consists of mixed waste paper pulp or optionally with proportions of mechanical pulp. Each mixing ratio is conceivable.

The backside is made of recycled paper stock and may contain bleached and / or unbleached pulp. The back can either be painted or uncoated. Depending on the raw material used, a distinction is made between qualities with the following abbreviation, with the number 1 indicating the variety with the highest quality. The total proportion of mixed waste paper pulp can be found in the following table

By way of example, customary used paper pulp fractions based on the total product are indicated therein. variety wastepaper GT1 80% - 100% GT2 80% - 100% GD1 15% - 65% GD2 70% - 90% GD3 80% - 100%

The following table gives an overview by way of example. In proportion, all mixtures are possible.

In any case, this multi-layer fibrous web or packaging paper or board web described above has a "white" fiber cover layer, which is subsequently provided with the white coating layer.

With the present inventive method, for the first time, packaging paper and paperboard of particularly high quality and printing properties can be produced.

The benefits of the process also include energy and resource savings. The process itself is characterized by an improvement in runnability.

The invention will be explained with reference to an embodiment.

Figur 1:

eine Darstellung eines Verfahrensschemas zur Herstellung einer mehrlagigen, gestrichenen Faserstoffbahn

Figur 2 :

eine schematische Darstellung des Konstantteiles zur Herstellung eines Stoffgemischs für die Herstellung einer Faserstoffbahn gemäß Figur 1.

Show it

FIG. 1:

a representation of a process scheme for producing a multi-layer, coated fibrous web

FIG. 2:

a schematic representation of the constant part for the preparation of a mixture for the production of a fibrous web according to FIG. 1 ,

In the FIG. 1 a process schematic of the production of a multilayer, coated paper or board web is shown.

The originating from a stock preparation stream S is supplied from a headbox 1 with a dilution water control a wire section I. The wire section consists of three longitudinal wires 2, 5 and 6 to form a multi-ply web B. The wire 2 is used to form a central layer, the wire 4 of the cover layer and the wire 4 is the back formed. The centerline wire 2 is equipped with a former 3 (traded by the applicant's company under the name DuoFormer D) and with a sieve shaker 4 (traded by the applicant's company under the name Duo Shake).

• Rückenlage, Mittelage, Decklage.
• Die Bahn B wird danach sukzessive durch Entwässerungselemente in der Siebpartie entwässert bis sie am Ende der Siebpartie I einen Trockengehalt von >16% hat.

The substance of the individual layers is sprayed from the corresponding headboxes 1, 1 a onto the respective longitudinal sieves 2, 5, 6 and dewatered thereon. At the points of contact of the Langsiebe the layers are vergautscht together. The layer structure is from bottom to top as follows:

• Supine position, middle position, top layer.
• The web B is then successively dewatered by drainage elements in the wire section until it has a dry content of> 16% at the end of the wire section I.

From the wire section I from the web B is transferred via various acceptance elements presses 7 in the press section II. The press section II with presses 7 consists of a double-felted suction press roller 7.1 in the first nip and a double-felted Nipco Flex press in the second nip and an offset press in the third nip. After press section II, web B reaches dry contents of up to 57%. This press concept can be executed with closed or open web guide. The stasis can also be designed as a cantilever. It is possible to sit in the press section II seamed or seamless felts

After leaving the press section II, or the presses 7, the further drying of the web B takes place by means of conventional drying cylinder groups 8a within a pre-drying section III, which here have two-row drying cylinder arrangements. Subsequent to the drying groups 8a, for example, a drying unit 9 with condensation press drying is installed. Here is a much more intense drying of the paper web and a significant increase in smoothness of the cylinder-contacted web page. Such a drying arrangement is for example from the EP 1586 698 A1 and the EP 0988 417 B1 known. This technology used here is particularly energy-efficient, since in addition to the high specific evaporation of more than 40 kg / m ² h and a significant increase in smoothness of the packaging paper or cardboard takes place within the dryer section hood. Preferred installation position of this condensation press dryer is in a range above 50% to about 90% dry content, but mainly above 55% dry content. The integration of one or more such drying units is preferably carried out in the pre-drying section III, but it is also conceivable to provide such units in a subsequent after-dryer section. Again, the condensation press dryer 9 offers the advantage of increased evaporation rates and paper smoothing.

These drying units 9 can be installed in "line", ie at the level of the conventional dryer section as well as in the machine cellar. The advantage of the installation in the machine cellar is that the drying unit or units 9 can be taken out of line and the drying process can only be carried out with a conventional drying section. Moreover, it is possible for existing machines that are limited in drying to achieve an increase in production through the installation of one or more drying units 9, by replacing conventional drying cylinders.

After this drying unit 9, a further conventional drying cylinder group 8b are present in the example shown.

After the end of the pre-drying section III follows an application of starch. This is done with a film press 10. With the help of this film press in the example, the strength is applied simultaneously on both sides of the web in an indirect manner. That is, the thickness is applied in each case to the circumference of an applicator roll and delivered to the surface of the two web pages in the nip between the two rollers. The advantage of this starch application is that an inferior raw material can be used for the middle ply while still achieving a high strength of the paper or cardboard. It is also conceivable to use a so-called size press instead of the said film press, which, as in the EP 1198643 A1 described, is equipped. Here, specially designed feed nozzles protrude into the gusset to form a coating medium sump in the application rollers forming a gusset and nip between two. This arrangement is referred to by experts as "SizeWings" and has the advantage that a higher exposure time of the application medium (sizing agent) results on the fibrous web and at the same time the formation of turbulence in the sump is avoided. As a result, the risk of the formation of foams, which would have a negative effect on the web properties, avoided.

This is followed by a after-dryer section IV with a conventional drying cylinder group 11, which in the example has a double row. At the end of the after-dryer section IV is a cooling group 12, which consists of two cooling cylinders, the upper cylinder being felted. With the help of these cooling cylinders, the fibrous web B is lowered to below 70 ° C.

This is followed by a pre-smoothing of the raw board or fibrous web B This can also be arranged within the after-dryer section IV, as already described in the explanation of the condensation press drying. In this case, however, no cooling group is provided in front of the unit 13.

In the example, a band calender is used as calender 13. This belt calender has a single-layer or multi-layer belt or belt with coating on the facing fibrous web side. The band consists predominantly, i. more than 70% plastic. The temperature of the calender is more than 80 ° C at the belt surface when the belt is in contact with the fibrous web. This achieves a very volume-saving and excellent smoothness.

In contrast to conventional calenders (Hardnip calender or HNC, softnip calender or SNC, wide-nip calender, shoe caliper), it is also conceivable to use a so-called CeraSoft calender technology and / or Valzone technology. All the calendering technologies described above, in contrast to conventional calenders (HNC, SNC, wide nip, shoe caliper), offer the advantage of particularly high increases in turgidity with a particularly low volume loss. In addition, by using these technologies inferior, cheaper raw material can be used with at the same time very low volume loss and excellent smoothness increase without loss of strength of uncoated board web. Especially with regard to calendering errors, e.g. mottling, with this technology, optimal results can be achieved without risk. It is also conceivable to use the calender 13 for after-smoothing the coated web B. Preferred mounting position of a calender for pre-smoothing is in a range of about 55% to about 90% dry content, but mainly about 60% dry content of the web.

In a coating section V, which follows the pre-smoothing, a white line is first applied to the white cover layer of the fibrous web B. This is done with a non-contact coating unit 14 in the form of a curtain applicator 14.1 (curtain coater), which is a slot (slot) or Gleitschichtdüse (slide the) has. With the curtain coating, coating composition containing particularly high amounts of even very uniformly white pigments is applied even at elevated speeds and a particularly good coverage and thus surface quality are achieved. Another possible execution of a curtain commissioned work goes from the EP A1-1 255 615 and is referred to in professional circles as "slide the", ie sliding layer nozzle.

It can be applied with a coating aggregate amounts up to 60g / m ² , which could otherwise be achieved only with several conventional coating units. There are single-layer application as well as multi-layered curtain applicators into consideration, which reduces the space required in the machine. In the example shown the FIG. 1 a single-layer commissioned work is planned.

Im in FIG. 1 As shown, the top layer is painted a second time with a conventional coating unit 15. Subsequently, the back of the fibrous web is also coated with a conventional coating unit 16. Conventional coating units 15 and 16 include, for example, a free-jet nozzle assembly, downstream of which a doctoring element or an application unit with a short residence time (SDTA) or otherwise known doctor blade applicator. At one each coating unit close unspecified contactless dryer, ie air dryer and infrared dryer on.

In a subsequent correction group 17, the top side and the bottom side of the web B-ie the top layer and the back-are heated to different degrees, which reduces the curl of the web (curl). This correction group 17 consists of a conventional one or two-row dryer group (in the example, the drying cylinders are arranged in two rows), which are equipped with and without dryer fabrics at the top and bottom. Preferably, the correction group 17 However, equipped with 2 drying screens one for the upper and one for the lower row of drying cylinders. The upper and lower drying cylinders within the correction group are heated so that the cylinder surface temperatures differ by at least 10 ° C.

Subsequently, the web is nachkalandriert in a calender 18. In the example, a Softnipkalander is used to create a particularly high gloss effect of the finished paper or cardboard and the micro-roughness is reduced.

Instead of this Softnipkalanders could also be distributed by the company of the Applicant so-called Terra X calender use. Such a calender has a heated roll with a plastic jacket which is provided with a metallic layer on. The thickness of the plastic sheath is about 5 to 50mm and the metallic layer is about 5 to 100 microns thick.

A cover layer on an elastic roller is for example in the DE 10 2008 037 999 A1 disclosed.

Before the reeling 20 on a scooter without center drive the web B is still cooled with a cooling group 19 to temperatures below 70 ° C.

The cooling group 19 is felted in the example shown below. The advantage of this is that the upper surface of the web B smoothed in the SoftnipKalander 18 no longer comes into contact with the wire and, as a result, the gloss effect is retained.

The arrangement of the cooling group 19 before the reeling 20 - as in FIG. 1 has shown the advantage that the thermal change in length of the web is reduced at the roller, whereby better winding properties are achieved.

For reeling 20 is to be added that also configurations of scooters with center drive are conceivable. Compared to scooters without center drive Finer settings of the winding properties can be achieved.

In the FIG. 2 the production of the mixture for the production of the fibrous web is shown schematically.

The above example sketch refers to a constant part of a web-making machine or system in which the top ply, the middle ply and the back ply consist of 100% virgin fiber. Therefore, a cleaner stage is provided in the respective material strand, since this is not provided in the stock preparation.

The material stream S coming from the stock preparation is premixed in a mixer 30 (ComMix) together with the white water, if appropriate also with additives, for example retention aids. The scrap is preferably mixed into the machine chest of the Middle Ply. It is also conceivable that the committee in the ComMix of Top Ply or Back Ply is led. For further dilution of the amounts of substance, the suspension is mixed with white water in a further mixer 31, a so-called Hydromix. The concentration of the stock suspension after the Hydromix is higher than the concentration of the headbox, with the advantage that a smaller number of assemblies can be selected for the subsequent cleaner 32 (Cleaner or EcoMizer). Small impurities, eg fine sand, are removed in this cleaning device 32. Subsequently, in the mixer 33, a further dilution with white water to the desired headbox concentration and optionally a mixture with additives. Through a headbox 34, the suspension for the destruction of fiber flakes and for final cleaning through a cleaning screen 35 (HB Screen, MSA, MST, MSS) out. In addition, here is a reduction of substance pulsations whereby material fluctuations in the headbox 36 can be avoided in the machine direction. Before the headbox 36 of the stock suspension, the necessary amount of retention agent 37 can be added. The water required for the dilution water control at the headbox 36a of the middle layer (midde ply) is taken from a white water channel and after the preparation in a device 38 in FIG a sifter led to the headbox.

LIST OF REFERENCE NUMBERS

I

Wire section

II

press section

III

pre-dryer

IV

Afterdryers

V

Coating section

1

headbox

2

wire

3

molder

4

Siebschütteleinrichtung

5

wire

6

wire

7

Press

7.1

suction press

8a

drying group

8b

drying group

9

Drying unit with condensation press drying

10

movie Press

11

drying cylinders

12

cooling group

13

Glättwerk with condensation - press smoothing

14

coater

14.1

Curtain applicator

15

coater

16

coater

17

correction group

18

calender

19

cooling group

20

Reeling

30

mixer

31

mixer

32

cleaning device

33

Headbox pump

34

mixer

35

Reingigungssieb

36, 36a

headbox

37

retention agents

38

conditioning device

Claims (14)

1. Method for producing a coated multilayer fibrous web, in particular a packaging paper or board web, in which first of all a stock stream is produced, which is then successively fed to at least two headboxes (1), at least one wire section (I) for forming a multilayer fibrous web (B), a press section (II), a drying section comprising drying groups (8a, 8b) and then to a reel-up,
   the drying groups (8a, 8b) being located within a pre-dryer section (III) and starch being applied after the end of the pre-dryer section, and an after-dryer section (IV) following, the multilayer fibrous web (B) produced being pre-calendered by a belt calender (13) within or following the after-dryer section (IV) and, after that, the top layer of the fibrous web (B) being coated with a white pigment-containing coating layer with the aid of a curtain applicator (14.1) and then being dried and, in the press section (II), use being made of at least one smooth roll, which acts at least on the top layer.
2. Method according to Claim 1,
   characterized in that
   the fibrous web (B) is produced in at least two layers, preferably three layers, specifically back layer, middle layer, top layer, the top layer containing white or bleached and/or deinked and/or wood-free fibres.
3. Method according to Claim 1 or 2,
   characterized in that
   condensation press drying (9) is carried out following the drying in the drying section (III) or between the individual dryers (8a) or following the dewatering in the press section (II).
4. Method according to at least one of the preceding claims,
   characterized in that
   following a curtain coating (14.1), the same web side is coated a second time with a conventional coating unit (15), such as a direct-application blade coating unit, is dried and, after that, the other web side is likewise coated with a conventional coating unit (16) and then dried by using dryers (17).
5. Method according to at least one of the preceding claims,
   characterized in that
   the coated web is fed to a correction group (17), a following calendering unit (18), a cooling group (19) and then to the reel-up (20).
6. Method according to Claim 1 and 2,
   characterized in that
   for the formation of the top layer of the multilayer fibrous web (B), fines are led into the headbox (1).
7. Method according to Claim 1,
   characterized in that
   the at least one white coating layer is applied by using a curtain applicator (14.1) applying one or multiple layers, in the form of a slot die or slide die.
8. Method according to Claim 5,
   characterized in that
   the calendering unit (18) used in the final group of the production machine has a heated roll with a synthetic material shell, which is provided with a metallic layer.
9. Method according to Claim 8,
   characterized in that
   the thickness of the synthetic material shell is about 5 to 50 mm, and the metallic layer has a thickness between 5 and 100 µm.
10. Method according to at least one of the preceding claims,
    characterized in that
    impingement drying known per se is performed directly after the press section (II) and still before the first heated drying cylinder of the drying section (III).
11. Method according to Claim 1,
    characterized in that
    during the pre-calendering of the fibrous web (B), use is made of a belt of which more than 70% consists of synthetic material and has a temperature of more than 80° C on the belt surface that is in contact with the fibrous web.
12. Method according to at least one of the preceding claims,
    characterized in that
    a coated board, in particular a chromo or chromo-substitute board or liquid board, or coated packaging paper, coated liner with white top layer (CWTTL = coated white top test liner) or coated kraft liner with white top layer (CWTKL = coated white top kraft liner) is produced thereby.
13. Method according to Claim 12,
    characterized in that
    the board or the paper has three layers, which comprise a fibre top layer made of bleached pulp, a middle layer made of wood-containing raw material and/or wastepaper stock, and a back layer made of bleached pulp or a mixture of bleached pulp with proportions of wood-containing raw material, to which proportions of wastepaper stock are also added.
14. Method according to Claim 12 and 13,
    characterized in that
    the board or the paper has four layers, which, in addition to the three layers, also has an underlayer between the top layer and middle layer, this underlayer consisting either of wastepaper stock or a mixture of wastepaper stock and wood-containing raw material.

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