EP3433420B1 - Device and method for producing a multiple-layer fibrous web - Google Patents

Description

The invention relates to a device for producing a multi-layer fibrous web, with a wire section for forming a multi-layer fibrous web, a press section for further dewatering of the multi-layer fibrous web, and a drying section for drying the multi-layer fibrous web, the wire section at least one first forming unit for forming a first layer of the multi-layer Fibrous web and at least a second forming unit for forming a second layer of the multilayer fibrous web and a gumming zone and the forming units for forming the multilayer fibrous web are arranged and designed so that the second layer is transferred to the first layer in the gumming zone for forming the multilayer fibrous web is and wherein the press section comprises at least two last press nips, the two last press nips by a first press element and a second press element with a common counter element nt are formed with a smooth surface for smoothing one side of the multilayer fibrous web.

The invention also relates to a method for producing a multilayer fibrous web.

Devices of this type are known from the prior art. The document DE102014210879 A1 describes a paper machine and a method for producing packaging paper. A multi-layer packaging paper web, consisting of a cover layer, a protective layer and a back layer, is produced in a wire section with two forming units and further dewatered in a press section consisting of a compact press with 3 press nips and then fed to a dryer section and further process steps. In the sieve section, the supine position is thickened onto the cover layer and drained through the cover layer. This leads to graying of the usually light-colored cover.

The document WO2010 / 020707 A1 also shows a paper machine for the production of packaging paper, especially white top liner. The wire section also includes two forming units to form two layers of the white top liner. After the individual layers have been crumpled up, the multi-layered fibrous web is transported lying on the drainage screen of the fourdrinier wire to a take-off point and removed from a pick-up press felt and guided to the press section.

In the document US3,915,791 A method for producing a single-layer or multi-layer fibrous web is disclosed. Two individual layers of the multilayer fibrous web are brought together and connected in a twin-wire former between two screens, the middle layer being formed there.

In the document WO01 / 18309 A1 a paper machine for producing liner is also disclosed. This is made from two layers in the wire section. In this case, the lighter top layer is thickened onto the bottom layer and the two-layer fibrous web is fed to a compact press with 3 press nips and then to a dryer section. For the dewatering of the fibrous web and smoothing of the lighter top layer, different press concepts are proposed, such as compact presses, inverted compact presses and a single press with subsequent compact press with two press nips. Furthermore, the alternative possibility of producing the lighter upper layer in such a way that it forms the lower layer of the fibrous web is disclosed, as a result of which the now upper layer of the fibrous web is dewatered through the now lighter lower layer.

Disadvantages of the known solutions are, on the one hand, the impairment of the so-called whiteness or brightness of the cover and, on the other hand, the complex and therefore expensive design of the press section. In addition to high investment costs, operating costs are also considerable due to the use of a large number of fabrics. In addition, the operating behavior of the machine concepts with inverted compact press is problematic.

It is therefore an object of the invention to propose an improved device and an improved method for producing a multi-layer fibrous web, in particular for producing liners with a back layer and a white cover layer, compared to the known solutions.

The object is solved by the features of claim 1. An apparatus for producing a multi-layer fibrous web is proposed, with a wire section for forming a multi-layer fibrous web, a press section for further dewatering of the multi-layer fibrous web and a drying section for drying the multi-layer fibrous web, the wire section at least one first forming unit for forming a first layer of the multilayered fibrous web and at least one second forming unit for forming a second layer of the multilayered fibrous web and a gumming zone and the forming units for forming the multilayered fibrous web are arranged and designed so that each other the second layer is transferred to the first layer in the gumming zone to form the multilayer fibrous web, and the press section comprises at least two last press nips, the last two press nips by a first press element and a second press element with a common counter element with a smooth surface for smoothing one Side of the multilayer fibrous web, are formed. The invention is characterized in that a transfer belt is provided for the direct takeover of the multilayered fibrous web at a takeover point from the first forming unit, that is, from the screen of the first forming unit, and for the further transport of the multilayered fibrous web, and in that a press belt for the direct takeover of the multilayer fibrous web is arranged at a removal point from the transfer belt and for guiding the multilayer fibrous web to the press section, and that the multilayer fibrous web together with the press belt is guided through the penultimate press nip in such a way that the second layer of the multilayer fibrous web comes into contact with the smooth surface of the counter element comes.

This solution has the advantage that the quality, e.g. For example, the whiteness or brightness, the second layer of the multilayer fibrous web in the wire section is not impaired by the drainage and at the same time a conventional, simple press section with a compact press without transfer belts can be used to smooth the side of the second layer of the multilayer fibrous web facing the common counter element , This also improves the operating behavior, in particular with regard to edge folds or edge tears occurring in the fibrous web. In addition, the drainage capacity is sufficient because the press has two press nips, each with at least one water-absorbing felt. Likewise, the smoothness of the second layer is improved by the smoothing effect of two press nips, more precisely by the last two press nips. The multilayered fibrous web formed is transferred by means of the transfer belt on a transport path which extends from the takeover of the multilayered fibrous web from the wire of the first forming unit to the direct takeover of the multilayered fibrous web by the press belt. The transfer belt is preferably arranged so that at least the major part of the transfer belt formed loop and the transport path runs below the wire section.

For example, the essential part can be more than 50%. This enables a compact design. This makes it possible to retrofit existing devices, for example paper machines, without significantly increasing the overall length. In addition, the arrangement has the advantage that the multilayer fibrous web is transported lying on the transfer belt and gravity presses the multilayer fibrous web onto the transfer belt.

When the multilayer fibrous web is taken over by the transfer belt from the screen of the first forming unit, the multilayer fibrous web is completely formed, that is to say neither an additional layer nor a further layer is added to the multilayer fibrous web.

In a practical example, the length of the transport route is more than 4 m, in particular more than 6 m, preferably more than 8 m or very preferably more than 10 m.

In a possible embodiment of the invention, the at least one first and / or the at least one second forming unit are designed as a wire.

In a further development, it is possible to equip the fourdrinier wire of the at least one first and / or the at least one second forming unit with a top wire in order to drain the respective layer on both sides. This can serve the purpose of increasing the drainage capacity and increasing the quality.

In a practical case, the at least one first and the at least one second forming unit are assigned a headbox for loading the corresponding forming unit with a fiber suspension.

In one possible practical embodiment, the fibrous suspension for the first forming unit has a different composition than the fibrous suspension for the second forming unit. For example, the fibrous suspension for the first forming unit can at least partially contain unbleached cellulose and / or waste paper and the fibrous suspension for the second forming unit contain a lighter fiber than for the first forming unit. The term "light" is to be understood to mean that the cover layer is optically lighter than the supine position.

In a preferred embodiment, the device is designed to produce a fibrous web from the group of liner, white top testliner, white top kraft liner or white lined chipboard. The first layer forms the darker back layer and the second layer the lighter layer with a higher whiteness of the multi-layer fibrous web. The weight per unit area of the multilayer fibrous web is preferably in the range from 70 to 250 g / m ² .

In a further possible embodiment, the device can comprise at least one further forming unit for forming at least one further layer of the multilayer fibrous web, the device being designed and arranged such that the further layer is arranged between the cover layer and the back layer of the multilayer fibrous web. The further forming unit can be assigned to the first and / or the second forming unit. The further layer generated on the at least one further forming unit is transferred to the first and / or the second forming unit to form the first and / or second layer. In the production of liners, the at least one further layer can form the protective layer and / or interlayer.

In an advantageous embodiment, the headbox assigned to the first forming unit is designed as a multi-layer headbox.

According to a practical further development, the first forming unit and / or the second forming unit is assigned a secondary stock head for applying a further fibrous stock suspension to a pre-dewatered fibrous web of the respective forming unit. The secondary headbox is arranged in the running direction after the headbox of the respective forming unit at a point at which the fibrous stock suspension applied by the headbox is partially dewatered.

In a further advantageous embodiment, the headbox assigned to the second forming unit is designed as a multi-layer headbox.

A short design in the machine running direction can be achieved by arranging the second forming unit above the first forming unit.

In certain cases, it is advantageous if the second forming unit is arranged essentially at the same level next to, ie in the machine running direction, upstream of the first forming unit. This is particularly advantageous for conversions or new systems in existing buildings with a low maximum crane hook height.

In a practical case, the common counter element is designed as a smooth roller. This is a compact, inexpensive and reliable solution.

It is also conceivable if a roller wrapped around by a belt with a smooth surface for smoothing the fibrous web is provided as a common counter element. This solution can be advantageous if a fully supported web transfer without free train to the subsequent dryer section is desired. This can be advantageous, for example, in the production of fibrous webs with low wet strength and / or at high speeds of more than 1600 m / min.

Furthermore, it is also possible if, seen in the machine running direction, a further press nip is arranged in front of the penultimate press nip.

In an advantageous practical embodiment, the further press nip is formed by the first press element and a counter roller, the multilayer fibrous web being guided through the further press nip lying between the press belt and a felt belt. The counter roll can be designed as a press roll with a smooth or grooved and / or blind drilled surface. The press belt can be designed as a felt belt. The counter roll is preferably arranged below the first press element. In this case, the press belt forms the upper felt of the double felted further press nip.

The transfer belt is advantageously designed to be permeable. It can be designed without a seam as well as with a seam.

It is also possible to design the transfer belt as a woven sieve or as a belt made of a cast plastic matrix with integrated reinforcing threads or as a metal belt. The metal strip can be heated.

It is possible to change the transfer belt if the chairs are equipped with a cantilever. However, the less expensive solution without a cantilever is also conceivable. In this case, the transfer belt is designed with a seam or the vertical chair supports are on the operating side (driver's side) with known insertion devices for the automatic passage of the transfer belt through the loaded vertical chair supports.

In a practical embodiment, within the loop of the screen of the first forming unit in the area and / or after the gumming zone, there is at least one suction element to improve the contact and the cohesion of the first and second layers of the multilayer fibrous web, and to increase the dry content of the multilayer fibrous web , arranged. Due to the action of the at least one suction element, the second layer is thus further dewatered by the first layer. The negative pressure in the at least one suction element is more than 30 kPa, preferably in the range between 30 kPa and 60 kPa, in particular between 40 kPa and 50 kPa.

A suction element is expediently arranged within the loop of the transfer belt in the region of the takeover point of the multilayer fibrous web from the first forming unit. The suction element can be designed as a suction box or as a suction roller. This enables a reliable takeover of the multilayer fibrous web from the wire of the first forming unit to the transfer belt. The action of the suction element is carried out in such a way that essentially no dewatering of the fibrous web takes place, but only the acceptance of the fibrous web is improved. The vacuum of the suction element is less than or equal to 30 kPa, preferably equal to or less than 20 kPa. The loop of the transfer belt is preferably free of drainage elements.

In a further possible embodiment, the multilayer fibrous web is crimped onto the transfer belt in front of the suction element in the region of a suction roller arranged within the loop of the first forming unit. Advantageously, the suction roll is immersed in the transfer belt. This ensures reliable transfer of the fibrous web to the transfer belt.

To stabilize the web run of the multilayer fibrous web on the transfer belt, at least one stabilizer is arranged as a stabilizing device within the loop of the transfer belt with respect to the fibrous web. The stabilization device can be vacuumed or non-vacuumed. It can be designed as a box and / or as a suction roll and / or as a support strip. To improve the guidance of the multilayer fibrous web, it is advantageous if the web guide is straight, that is to say without deflections on the transfer belt until it is accepted or taken over by the press belt. The take-off point or take-over point is preferably in front of a deflection roller for deflecting the transfer belt. As a result, the fibrous web is guided in a straight and stable manner on the transfer belt.

The use of stabilizing devices is particularly advantageous because, on the one hand, the contact of the fibrous web to the transfer belt is low, since there is no significant dewatering of the fibrous web by means of underpressure or pressing pressures before and during the continuation, as is the case, for example, on the forming fabric. There the dewatering process creates a certain form fit of the fibrous web with the surface structure of the forming fabric. On the other hand, forces occur, such as gravity when the web is guided at the bottom and air friction forces, which can have a particularly disruptive effect due to the lack of positive locking of the fibrous web with the transfer belt surface.

This advantageous solution counteracts these interferences. The fibrous web lies between the transfer point and the delivery point of the fibrous web above the transfer belt and the stabilizing devices. The influence of gravity thus acts stabilizes the web and presses the fibrous web onto the transfer belt. It also supports the stabilizing effect of the stabilizing devices. These have, for example, support strips which are in contact with the inside of the transfer belt. The course of the transfer belt is thus stabilized, which also makes the running behavior of the fibrous web more stable and thus edge lifting, edge folds and edge tears are avoided. The stabilizing devices can work advantageously both with and without the use of negative pressure. Another advantage is the essentially straight course of the transfer belt between the takeover point and the takeoff point. Although due to the action of the support strips, the course is not exactly straight, but the course on the support strips can experience minor deflections of less than 1 °, this course should also be understood as straight in the sense of the invention up to a total deflection of approximately 10 ° , The support strips can therefore be pressed somewhat into the loop of the transfer belt, so that a polygonal course of the transfer belt is created.

In a practical possible embodiment, the angle of a change in direction on the support strips of the essentially straight course of the transfer belt is a maximum of 0.6 °.

It is also possible to use support strips which lie flat against the inside of the loop formed by the transfer belt.

It is also conceivable to use foil-like support strips which rest with the front edge on the inside of the loop formed by the transfer belt. Such support strips, also called foil strips, have, viewed in the machine running direction, a surface after the front edge which extends at an angle away from the inside of the transfer belt. Such foils are known in paper technology and are usually used in the forming area for dewatering the fibrous web. There, the fibrous web has enough water to fill the wedge-shaped gap with water and thus to generate a significant negative pressure. In the present application, however, the dry content of the fibrous web is too low to achieve this effect. However, the inventor recognized that even without resulting white water creates a negative pressure, which can be sufficient for stabilizing the fibrous web.

In a possible practical embodiment, the transfer belt is arranged below at least part of the wire section. This reduces the length of the paper machine and reduces building costs. Another advantage is the possibility of installing the paper machine concept in existing production halls. Conversions can thus also be implemented inexpensively.

In a preferred embodiment, a plurality of support strips are arranged one behind the other in the machine direction and preferably at a distance of 0.5 m to 3 m, in particular from 1.0 m to 2.2 m, and extend transversely to the machine direction. This version is particularly inexpensive.

Furthermore, the support strips on strip holders can preferably be connected via a T-connection or dovetail connection, with strip holders in turn being mounted on strip bodies. This structure, which is known per se, has the advantage that the support strips can be exchanged easily and quickly.

The material of the support strips can be selected from the following group: ceramic, plastic, coated metal strips.

In a practical embodiment, support strips extend at least over the entire width of the fibrous web.

In one possible development, the support strips extend in sections transversely to the machine direction, wherein the support sections of the support strips adjacent in the machine direction can be arranged in alignment or offset. Transversely to the machine running direction, that is to say in the transverse direction, a plurality of support strip sections are arranged next to one another at a distance, so that gaps arise between the support strips. These gaps allow air to escape in the machine direction. It can thus be avoided or reduced dynamic pressures caused by drag air of the transfer belt. Dynamic pressures can promote or even generate a disruptive detachment of the fibrous web from the transfer belt. This possible solution is particularly advantageous for paper machine speeds of over 800 m / min. The division in the transverse direction of the support strip sections is preferably constant. In the case of the aligned support sections, it is possible that the transfer ribbon guide is designed to be oscillatable in the transverse direction. This minimizes wear and makes it more even.

In a possible further embodiment, a plurality of support strips are arranged next to one another transversely to the machine direction and preferably at a distance of 0.3 m to 1.5 m, in particular from 0.9 m to 1.2 m, and extend along the machine direction. This has the advantage of avoiding back pressure formation. The strips can extend between the takeover point and the takeoff point in a one-piece or multi-part design.

The transfer belt can be provided such that it can be oscillated transversely to the machine direction, preferably with an amplitude of -20 mm to +20 mm. This minimizes wear on the support strips and makes them more uniform.

In one possible development, the support strips are arranged within a closed box which is sealed with respect to the transfer belt and can be subjected to a vacuum of preferably 20 to 200 Pa, in particular 50 Pa to 120 Pa. The seal to the transfer belt can be designed in the form of all-round ceramic strips forming the edge of the box.

In a further embodiment, at least one longitudinal edge suction device for stabilizing the web edges can be arranged on each of the two edge regions of the multilayer fibrous web on the side of the transfer belt opposite the, in particular multilayer, fibrous web.

In a practical embodiment variant, the multilayer, fibrous web is transferred directly from a forming fabric of the wire section to the transfer belt at the take-over point and in the area of the take-over point there is a suction slit within the loop formed by the transfer belt Transfer suction device or a transfer suction roller and preferably a fixing suction device arranged downstream of the suction suction device. The transfer suction device or the transfer suction roll improves the transfer of the fibrous web to the transfer belt. The fixing suction device stabilizes the contact between the fibrous web and the transfer belt.

In a specific example, a vacuum of 6 kPa to 25 kPa, preferably 10 kPa to 15 kPa, can be applied to the transfer suction device or the transfer suction roll and / or the preferably downstream suction device. If the vacuum is too high below the ambient pressure, the wear on the support strips and the transfer belt will increase. On the other hand, if the vacuum is too low, there is a risk that the suction slots of the transfer suction device or the fixing suction device will become blocked or that the fibrous web will lift off.

Furthermore, the device can be designed to produce a multilayer fibrous web from the group of liner, white top testliner, white top kraft liner or white lined chipboard, comprising a light-colored cover layer and a back layer. The light-colored cover preferably comes into direct contact with the transfer ribbon. The term "light" is to be understood to mean that the cover layer is optically lighter than the supine position. The advantage of this design variant lies in a positive effect on the overall process and in particular in an improvement in the quality of the, in particular multilayer, fibrous web. These types of paper place high demands on the light-colored cover, since it is printed and forms the outside of packaging and must therefore have good optical properties. With this design variant, the properties of the surface of the cover layer can be positively influenced by the design of the transfer belt surface.

Advantageously, the transfer belt is assigned a moistening unit for moistening the paper-contacted surface of the transfer belt with a fluid, preferably with water. As a result, the web run can be stabilized by increasing the adhesion of the fibrous web to the transfer belt surface.

The moistening unit is designed to apply 1 g / m ² to 8 g / m ² , in particular 3 g / m ² to 5 g / m ^{2, of} the fluid to the paper-contacted surface of the transfer belt.

To stabilize the web run of the multilayer fibrous web on the transfer belt, it is also possible if the multilayer fibrous web between the transfer point through the transfer belt and the transfer point through the press belt is guided at least in sections in a sandwich guide between the transfer belt and a guide belt. This is particularly advantageous at higher speeds of the paper machine, in particular at a speed of more than 1200 m / min.

In one possible embodiment, the guide band is formed at least in sections by the screen of the first forming unit. The transfer belt and the guide belt are guided on the sandwich guide route via guide elements, such as guide rollers, strips. In this section they run parallel to each other and have the same course.

However, it is also conceivable for the guide band to be formed at least in sections by an additional further band forming a loop. This solution is advantageous if the fibrous web has to be transported over longer distances.

Furthermore, it is possible if in a first section the guide band is formed by the screen of the first forming unit and in a second section the guide band is formed by an additional, further band forming a loop

In one possible embodiment, the middle course of the sandwich guide is essentially straight and is determined by the alternating arrangement of at least one support roller arranged in the loop formed by the transfer belt and at least one support roller arranged in the loop formed by the guide belt. Zigzag-shaped sections can also be superimposed on the straight middle course result from the arrangement of the mentioned support rollers to each other. This guide offers advantages in tight spaces.

The change in direction of the course of the sandwich guide through the support rollers is preferably in the range from 10 ° to 20 °. The change in direction can be designed alternately and forms a straight line on average.

In a further embodiment, the course of the sandwich guide is essentially polygonal and is determined by the arrangement of at least two support rollers arranged in the loop formed by the transfer belt. The support rollers can be arranged on an imaginary arc line, in particular on a circular arc line. Back-up rollers are preferably used as guide elements from a paper machine speed of more than 1300 m / min. Below 1300 m / min, support strips or support foils can also be used, the surface of which facing the transfer belt has an angle to the transfer belt in the machine running direction to form a negative pressure.

Guide elements, such as guide rolls, support rolls, support strips, support foils within the loop of the transfer belt are preferably at a distance of greater than 1.5 m in the area of the sandwich guide, and preferably less than or equal to 3 m.

According to a possible practical embodiment, at the end of the sandwich guide, the guide belt is guided away from the multilayer fibrous web in a region of a suction roller arranged in the loop formed by the transfer belt. This ensures that the fibrous web runs securely with the transfer belt. Preferably, the guide belt, together with the transfer belt, partially wraps around the suction roll, so that the negative pressure applied to the suction roll presses the fibrous web onto the transfer belt.

In a further embodiment, at the end of the sandwich guide, the guide belt is guided away from the multilayer fibrous web in front of a suction roll arranged in the loop formed by the transfer belt, wherein in the loop formed by the transfer belt, suction elements, in particular a transfer suction device and / or a flat suction device, are arranged to support the transfer of the multi-layer fibrous web by the transfer belt, the flat suction device — if present — preferably being arranged downstream of the transfer suction device. The level of the vacuum applied to the separating suction device and the flat suction device is in each case more than 10 kPa, in particular more than 12 kPa, preferably more than 15 kPa.

In a possible development of the invention, the dryer section comprises a pre-dryer section and a dryer section. After the pre-dryer section, a size press can be provided to apply starch, for example. A smoothing unit can be arranged after the drying section.

Furthermore, a tension of the transfer belt in the range between 6 kN / m and 12 kN / m, preferably 8 kN / m, is advantageous.

In an advantageous embodiment, a dryer fabric of the dryer section is provided directly after the last press nip arranged on the common counter element for taking over the multilayer fibrous web and for transporting the fibrous web into the dryer section. The fibrous web is thus transferred directly to the dryer section.

In a possible development of the invention, a smoothing unit is arranged after the dryer section.

The object is also achieved by a method for producing a multilayer fibrous web according to claim 14. The multilayer fibrous web is formed in a wire section and passed through a press section for further dewatering of the multilayer fibrous web, and through a drying section for drying the multilayer fibrous web. In the wire section, a first layer of the multilayer fibrous web is produced in a first forming unit and a second layer of the multilayered web in a second forming unit, and the second layer is transferred to the first layer in a gumming zone and the multilayer fibrous web is guided through at least two last press nips of the press section , the last two Press nips are formed by a first press element and a second press element with a common counter element with a smooth surface and one side of the multilayer fibrous web is smoothed by the smooth surface. According to the invention, it is provided that the multilayer fibrous web is taken over by a transfer belt directly from the first forming unit and transported further, and that the multilayer fibrous web is taken over directly from the transfer belt by a press belt and guided to the press section and is guided together with the press belt through the penultimate press nip and the second layer of the multilayer fibrous web is smoothed by the smooth surface of the counter element.

Further features and advantages of the invention result from the following description of preferred exemplary embodiments with reference to the drawings.

Figur 1

eine erste Ausführungsform einer erfindungsgemäßen Vorrichtung in vereinfachter Darstellung;

Figur 2

eine zweite Ausführungsform einer erfindungsgemäßen Vorrichtung in vereinfachter Darstellung;

Figur 3

eine alternative Ausführung der Übernahmestelle der mehrlagigen Faserstoffbahn von der ersten Formiereinheit auf das Transferband

Show it

Figure 1

a first embodiment of a device according to the invention in a simplified representation;

Figure 2

a second embodiment of a device according to the invention in a simplified representation;

Figure 3

an alternative embodiment of the transfer point of the multilayer fibrous web from the first forming unit to the transfer belt

The Figure 1 shows a first embodiment of a device 1 according to the invention for producing a multilayer fibrous web 11 in a simplified representation. In this example, the paper type liner is produced as a multi-layer fibrous web 11. The liner has at least two layers. The first layer 9 forms the darker back or the back layer and the second layer 10 forms the lighter cover or the cover layer of the fibrous web 11. The basis weight of the liner is in a range from 70 to 250 g / m ^2. The device 11 comprises a wire section 6 to form a multilayer fibrous web, a press section 7 for further dewatering and a drying section 8 for drying the multilayer fibrous web, which is only partially shown here. The wire section 6 comprises a first forming unit 2 for forming a first layer 9 of the multilayer fibrous web 11 and a second one Forming unit 3 for forming a second layer 10 of the multi-layer fibrous web 11, and and a gumming zone 37. The forming units 2, 3 are arranged and designed so that the second layer 10 is on top of the first layer 9 in the gumming zone 37 for forming the multi-layer fibrous web 11 is transmitted. In this example, the first and second forming units 2, 3 are designed as four-wire. One or both forming units 2, 3 can be adjusted with a top wire Figure 2 be equipped for bilateral drainage. The back layer is thus formed on the sieve 35 of the first forming unit 2 and the cover layer on the sieve 36 of the second forming unit 3. The running direction in the sheet formation zone of the screen 35 of the first forming unit 2 is opposite to the machine running direction 22. After the formation of the multilayer fibrous web 11, the latter is conveyed to a permeable transfer belt 20 lying on the wire 35 of the first forming unit 2 and taken over directly by the permeable transfer belt 20 at the transfer point 34. The fibrous web 11 is transported in the machine direction 22 by the transfer belt 20 and is removed directly from a press belt 19 at a take-off point and guided to the press section 7. The transfer belt 20 thus transfers the multi-layer fibrous web 11 on a transport route from the takeover of the multi-layer fibrous web 11 to the direct takeover of the multi-layer fibrous web 11 by the press belt 19. The transfer belt is arranged such that the essential part of the loop and formed by the transfer belt 20 so that the transport route runs below the wire section. This enables a compact design. In addition, the arrangement has the advantage that the multilayer fibrous web 11 is transported lying on the transfer belt 20 and gravity presses the multilayer fibrous web onto the transfer belt 20. The length of the transport route is 7 m.

Alternatively to that in Figure 1 shown embodiment of the removal of the fibrous web 11 from the transfer belt 20 at the removal point by the press belt 19, it is also possible to arrange the removal point in front of the deflection roller instead of after the deflection roller. As a result, the fibrous web 11 is guided in a straight and stable manner on the transfer belt 20. This type of decrease and guidance of the fibrous web is also according to the embodiment of the device Figure 2 applicable.

The press section 7 comprises two last press nips 12, 13, the two last press nips 12, 13 being formed by a first press element 15 and a second press element 16 with a common counter element 18 designed as a roller with a smooth surface for smoothing one side of the multilayer fibrous web 11 are. The multilayer fibrous web 11 is guided together with the press belt 19 through the penultimate press nip 12 such that the second layer 10, in this example the cover layer, of the multilayer fibrous web 11 comes into contact with the smooth surface of the counter element 18.

This solution has the advantage that the quality, e.g. For example, the brightness of the cover layer of the multilayer fibrous web 11 in the wire section 6 is not impaired by the drainage and at the same time a conventional, simple press section 7 with a compact press without transfer belts can be used to smooth the side of the cover layer of the multilayer fibrous web facing the common counter element 18 , This also improves the operating behavior, in particular with regard to occurring edge folds or edge tears in the fibrous web 11. In addition, the drainage capacity is sufficient since the press has two press nips 12, 13, each with at least one water-absorbing felt 19, 26. Likewise, the smoothness of the cover layer is improved by the smoothing effect of two press nips, more precisely by the last two press nips 12, 13.

In a further development, not shown, the two layers 9, 10 or just one of the two layers can also be constructed in multiple layers. In this case, the first and second forming units 2, 3 or possibly only one forming unit are assigned a further forming unit to form a further layer. The multilayer backing and / or the multilayer lid layer are then, as described above, brought together to form the multilayer fibrous web 11 on the wire of the first forming unit. In this case, the fibrous web 11 is composed of more than two layers, the further layer or the further layers being arranged between the outer layers of the multilayer fibrous web 11.

The forming units 2, 3 are each assigned a headbox 4, 5 for feeding a fiber suspension. One or both of the headboxes can also be designed as a multi-layer headbox, the composition of the fiber suspensions in the different layers of a headbox being different. In this case, the first layer 9 and / or the second layer 10 of the fibrous web have several layers. This makes it possible to specifically influence the composition and quality of the individual layers in the thickness direction.

In the device after Figure 1 is, seen in the machine direction 22, another press nip arranged to increase the dewatering performance before the penultimate press nip 12. This further press nip 14 is felted twice and is formed by the first press element 15, here exemplified as a suction press roll, and a counter roll 17 designed as a press roll. The fibrous web 11 passes through the further press nip, lying between the press belt 19, which is designed as a felt belt, and a felt belt 25. The counter roll 17 is arranged below the first pressing element 15. In this case, the press belt 19 forms the upper felt of the double felted further press nip.

The forming units 2, 3 are arranged one above the other and above the transfer belt 20. This enables a short design. Support rollers 24 and / or static support strips for supporting the transfer belt 20 are arranged in the loop of the transfer belt. Additionally or alternatively, stabilizers as in Figure 2 shown and described.

Immediately after the last press nip 13 arranged on the common counter element 18, a dryer fabric 27 of the dryer section 8 is provided for the direct takeover of the multilayer fibrous web 11 and for the transport of the fibrous web into the dryer section 8. The fibrous web is thus transferred directly into the dryer section. The fibrous web 11 is guided through the dryer fabric 27 via the drying cylinders 28 and suction deflecting rollers 29 of the first dryer group of the dryer section 8.

After a first drying step, the fibrous web 11 can be provided with a starch screed on one or both sides in an application unit. A pigment coat can be applied to improve the quality of the cover 10. After the subsequent after-drying section, a smoothing unit can be provided.

At least one suction element 38 for improving the contact and the cohesion of the first and second layers 9, 10 of the multilayer fibrous web 11 are arranged in the area and / or after the gumming zone 37 within the loop of the sieve 35 of the first forming unit. Due to the action of the at least one suction element 38, the second layer is thus further dewatered by the first layer. The negative pressure in the at least one suction element is more than 30 kPa, preferably in the range between 30 kPa and 60 kPa, in particular between 40 kPa and 50 kPa.

The Figure 2 shows a further possible design of the wire section 6. The second forming unit 3 is arranged essentially on the same level next to, ie in front of the first forming unit 2 in the machine direction 22. This is particularly advantageous for conversions or new systems in existing buildings with a low maximum crane hook height. An upper wire 30 is assigned to the four wire of the first forming unit 2. As a result, the first layer 9 that forms is drained on both sides. The sheet structure is symmetrical and the drainage capacity is increased. It is also possible to equip the second forming unit 3 with a top wire.

In order to improve the quality, in particular the formation and the splitting strength of the higher-quality cover layer 10, it is also possible to equip the forming unit 3 with an egoutteur.

A suction element 21 is arranged within the loop of the permeable transfer belt 20 in the region of the takeover point 34 of the multilayer fibrous web 11 from the first forming unit 2. The suction element 21 can be designed as a suction box or as a suction roller. In front of the suction element 21, the multilayer fibrous web 11 is crimped onto the transfer belt 20 in the area of a suction roller 32. The suction roller 32 advantageously dips in the transfer belt. This ensures reliable transfer of the fibrous web 11 to the transfer belt 20. To stabilize the web run of the fibrous web 11 on the transfer belt 20, at least one stabilizer 31 is arranged within the loop of the transfer belt 20 with respect to the fibrous web 11. The stabilizer 31 can be vacuumed or non-vacuumed. It can be designed as a box or as a suction roller or as a supporting foil plate. Support rollers 24 can optionally be provided between the stabilizers 31. The further course of the fibrous web 11 and the configuration of the press section 7 and the dryer section 8 correspond to the embodiment of FIG Figure 1 , Corresponding element of the exemplary embodiments in the Figure 1 and Figure 2 are provided with the same reference numerals.

At least one suction element 38 for improving the contact and the cohesion of the first and second layers 9, 10 of the multilayer fibrous web 11 are arranged in the area and / or after the gumming zone 37 within the loop of the sieve 35 of the first forming unit. Due to the action of the at least one suction element 38, the second layer is thus further dewatered by the first layer. The negative pressure in the at least one suction element is more than 30 kPa, preferably in the range between 30 kPa and 60 kPa, in particular between 40 kPa and 50 kPa.

In the Figure 3 An alternative embodiment of the transfer point 34 of the multilayer fibrous web from the first forming unit 2 to the transfer belt 20 is shown. In the loop of the transfer belt 20, a takeover suction roll 33 is arranged to support the takeover of the multi-layer fibrous web 11 from the first forming unit 2, that is to say from the wire 35 of the first forming unit 2. The transfer suction roll 33 dips into the screen 35 of the first forming unit 2. After the takeover, the screen 35 of the first forming unit 2 is guided away from the multi-layer fibrous web 11. The fibrous web is thus on the upper side of the transfer belt 20. The vacuum in the suction zone of the suction roller 33 is in the range of less than 30 kPa. This ensures that the multilayer fibrous web 11 is no longer dewatered. This does not affect the white of the ceiling.

LIST OF REFERENCE NUMBERS

1

contraption

2

first forming unit

3

second forming unit

4

headbox

5

headbox

6

Wire section

7

press section

8th

drying section

9

first layer of the fibrous web

10

second layer of the fibrous web

11

Fibrous web

12

penultimate press nip

13

last press nip

14

another press nip

15

first pressing element

16

second pressing element

17

backing roll

18

common counter element

19

press belt

20

transfer tape

21

suction

22

Machine direction

23

Direction of travel of the first forming unit

24

supporting roll

25

Filzband

26

Filzband

27

dryer

28

drying cylinders

29

suction turning roll

30

top wire

31

stabilizers

32

suction roll

33

Übernahmesaugwalze

34

over location

35

Sieve of the first forming unit

36

Sieve of the second forming unit

37

Vergautschungszone

38

suckers

Claims (14)

1. Device (1) for producing a multiple-layer fibrous web, having a screen section (6) for forming a multiple-layer fibrous web (11), a press section (7) for further dewatering the multiple-layer fibrous web (11), and a drying section (8) for drying the multiple-layer fibrous web (11), wherein the screen section (6) comprises at least one first forming unit (2) for forming a first layer (9) of the multiple-layer fibrous web (11), and at least one second forming unit (3) for forming a second layer (10) of the multiple-layer fibrous web (11), and a compression zone (37), and the forming units (2, 3) for configuring the multiple-layer fibrous web (11) are mutually disposed and configured such that the second layer (10) is transferred onto the first layer (9) in the compression zone (37) so as to configure the multiple-layer fibrous web, wherein the press section (7) comprises at least two last press nips (12, 13), wherein the two last press nips (12, 13) for smoothing one side of the multiple-layer fibrous web (11) are formed by a first press element (15) and a second press element (16) having a common counter element (18) with a smooth surface, and wherein the multiple-layer fibrous web (11) conjointly with a press belt (19) is guided through the last-but-one press nip (12) in such a manner that the second layer (10) of the multiple-layer fibrous web (11) contacts the smooth surface of the counter element (18),
   characterized in that
   a transfer belt (20) is provided for directly acquiring the multiple-layer fibrous web (11) at an acquisition location (34) from the first forming unit (2) and for the onward transportation of the multiple-layer fibrous web (11), and in that the press belt (19) guided conjointly with the multiple-layer fibrous web (11) through the last-but-one press nip (12) is disposed for directly acquiring the multiple-layer fibrous web (11) at a retrieval location from the transfer belt (20) and for guiding the multiple-layer fibrous web (11) to the press section (7).
2. Device (1) according to Claim 1,
   characterized in that
   the device is configured for producing a fibrous web from the group of liner, white top testliner, white top kraftliner, or white lined chipboard, and in that the first layer (9) comprises the rear layer, and the second layer (10) comprises the cover layer of the multiple-layer fibrous web (11).
3. Device (1) according to one of the preceding claims,
   characterized in that
   the headbox (4) assigned to the first forming unit (2) is embodied as a multiple-layer headbox.
4. Device (1) according to one of the preceding claims,
   characterized in that
   the headbox (5) assigned to the second forming unit (3) is embodied as a multiple-layer headbox.
5. Device (1) according to one of the preceding claims,
   characterized in that
   the second forming unit (3) is disposed above the first forming unit (2).
6. Device (1) according to one of Claims 1 to 4,
   characterized in that
   the second forming unit (3) in the machine running direction is disposed so as to be substantially at the same level ahead of the first forming unit (2).
7. Device (1) according to one of the preceding claims,
   characterized in that
   the common counter element (18) is embodied as a smooth roller.
8. Device (1) according to one of the preceding claims,
   characterized in that,
   when viewed in the machine running direction (22), a further press nip (14) is disposed ahead of the two last press nips (12, 13).
9. Device (1) according to Claim 8,
   characterized in that
   the further press nip (14) is formed by the first press element (15) and a counter roller (17), and in that the multiple-layer fibrous web (11) is guided through the further press nip (14) so as to lie between the press belt (19) and a felt belt (25) .
10. Device (1) according to one of the preceding claims,
    characterized in that
    the transfer belt (20) is embodied so as to be permeable.
11. Device (1) according to one of the preceding claims,
    characterized in that
    a suction element (21) is disposed within the loop of the transfer belt (20), in the region of the acquisition location of the multiple-layer fibrous web (11) from the first forming unit (2).
12. Device (1) according to one of the preceding claims,
    characterized in that
    a drying screen (27) of the drying section (8) for acquiring the multiple-layer fibrous web (11) is provided directly after the last press nip (13) disposed on the common counter element (18).
13. Device (1) according to Claim 12,
    characterized in that
    a smoothing unit is disposed after the drying section (8).
14. Method for producing a multiple-layer fibrous web (11), wherein the multiple-layer fibrous web (11) is formed in a screen section (6) for further dewatering of the multiple-layer fibrous web (11) is guided through a press section (7), and for drying the multiple-layer fibrous web (11) is guided through a drying section (8), wherein, in the screen section (6), a first layer (9) of the multiple-layer fibrous web (11) is produced in a first forming unit (2), and a second layer (10) of the multiple-layer fibrous web (11) is produced in a second forming unit (3), and the second layer (10) is transferred onto the first layer in a compression zone (37), and the multiple-layer fibrous web (11) is guided through at least two last press nips (12, 13) of the press section (7), wherein the two last press nips (12, 13) are formed by a first press element (15) and a second press element (16) having a common counter element (18) with a smooth surface, wherein one side of the multiple-layer fibrous web (11) is smoothed by the smooth surface, and wherein the multiple-layer fibrous web (11), conjointly with a press belt (19), is guided through the last-but-one press nip (12) and the second layer of the multiple-layer fibrous web (11) herein is smoothed by the smooth surface of the counter element (18),
    characterized in that
    the multiple-layer fibrous web (11) by a transfer belt (20) is acquired directly from the first forming unit (2) and transported onwards, and in that the multiple-layer fibrous web (11) by the press belt (19) that, conjointly with the multiple-layer fibrous web (11), has been guided through the last-but-one press nip (12) is directly acquired by the transfer belt (20) and guided to the press section (7).

Images