Production line for producing fiber webs and methods for producing fiber webs

Abstract

The present invention relates to a production line for producing fiber webs (W), the production line (200) including a forming section (210) including at least one headbox (M10; M20; M30) and a forming unit (220), the forming unit including at least one web (10; 20; 30) and at least one dewatering device (11, 15, 16, 17, 21, 25, 31, 35, 56), and the production line (200) including a sizing section (250) including a sizing machine having a sizing roll gap formed between two sizing rolls (75). The production line (200) includes at least one application device (C10; C20; C30; C50) located in the forming unit (220) and configured to apply sizing agent in foam form for internal sizing of the fiber web (W), and the sizing machine located in the sizing section (250) includes at least one application device (C75) configured to apply sizing agent for surface sizing of the fiber web (W).

Description

Technical Field

[0001] This invention relates generally to the production of fiber webs. Specifically, it relates to a production line for producing fiber webs according to the preamble of the independent claim for a production line, and to a method for producing fiber webs according to the preamble of the independent claim for a method. Background Technology

[0002] As is known in the art, in fiber web machines, particularly in paper and paperboard machines, fiber webs are produced and processed in an assembly formed by multiple devices arranged sequentially on a production line. A typical production line includes a forming section, a pressing section, and subsequent drying sections and a winding unit, the forming section including a headbox and forming unit. The production line and processing line may also include other devices and sections for finishing the fiber web, such as sizing machines, calenders, and coating sections. The production line and processing line typically also include at least one winding machine for forming customer rolls and roll packaging equipment. In this specification and the following claims, fiber web specifically refers to paperboard webs. This invention is particularly applicable to the production of multi-lay fiber webs.

[0003] The headbox's function is to supply the fiber suspension used for fiber web production to the forming unit. In a multi-layer headbox, more than one type of fiber suspension is discharged from the headbox via flow channels for forming one layer of the multi-layer fiber web.

[0004] The task of the forming unit is to remove water from the fiber suspension fed by the headbox. When the web is made from a water-based fiber raw material, water is removed from the raw material in the forming section by one or more forming nets that begin forming the web. Fibers remain on the forming nets or between the forming nets moving together. Different types of raw materials are used depending on the grade of the web being manufactured. The volume of water that can be removed from different raw materials to obtain a high-quality web is influenced by many factors, such as the required web basis weight, the machine's design speed, and the desired fine fiber content, fiber, and filler levels in the finished product. Many types of devices are known on the forming unit, such as foil strips, suction boxes, guide rollers, suction rollers, and rollers with surface openings; these devices are used in many different arrangements and configurations when attempting to optimize the volume, time, and location of water removal during the formation of the fiber web. The manufacture of a high-quality final product of the desired grade is influenced by the dewatering volume, dewatering method, dewatering duration, and dewatering location.

[0005] A common method for manufacturing multiply fiber webs is based on using several separate web forming units, in which different layers of the fiber web are laid on top of each other or on separate webs in a layer-by-layer manner, in which case they are bonded together after partial dehydration. Although the terms "multiply" and "multilayer" are often used synonymously and their differences can only be defined by context, the term "multiply" is generally used in multiply / multilayer fiber web production, i.e., when producing fiber webs with more than one layer, when these layers are formed individually in the forming section, and the term "multilayer" is used when a multilayer headbox is used to feed the suspension layer to the forming section. In this application, the term "multiply" is interpreted as synonymous with "multilayer".

[0006] In the production of fiber webs, such as paper webs or paperboard webs, sizing is used to modify the properties of the fiber webs by adding sizing agents (such as starch or other sizing agents). Sizing can be divided into internal sizing and surface sizing. In internal sizing (sometimes called raw material sizing), the sizing agent is added to the pulp at the wet end of the fiber web machine before forming. In surface sizing, the sizing agent is typically added to the surface of the fiber web at the dry end of the fiber web machine. Surface sizing of fiber webs typically utilizes an application device—a sizing machine—which usually includes two sizing rollers forming a sizing roller gap, wherein the sizing agent applied directly or indirectly to the fiber web via the surfaces of the sizing rollers is pressed onto the fiber web on one or both sides. The sizing machine, together with the drying equipment following the sizing machine, forms the sizing section of the fiber web production line. In conjunction with sizing machines, existing technologies employ various application techniques for applying sizing agents to fiber webs, such as curtain application, doctor blade application, film transfer application, rod application, air brush application, spray application, or pool application. Sizing aims to improve the properties of paper webs, particularly water resistance, water absorption, strength, internal strength, and flexural stiffness. Furthermore, running performance and dust resistance are also positively affected. It is well known that for the production of multi-layer fiber webs, sizing can also be performed in the forming section by spraying or foaming the sizing agent between the layers of the multi-layer fiber web.

[0007] Foam application systems typically include mixing devices, pumping devices, foaming devices, piping systems, and application units. Foaming is based on the vigorous mixing of air into a liquid-based material with surfactant additives, resulting in a significant increase in specific volume and thus making the material easier to handle and apply with a smaller dry weight. Foam application devices typically include an application head with a grooved nozzle for extruding foam onto the web. Shortly after application, the foam structure breaks down, absorbs, and diffuses into the surface structure of the web, leaving a wetted layer of material.

[0008] The object of the present invention is to provide a production line for producing fiber webs and a method for producing fiber webs, wherein the disadvantages and problems of the prior art are eliminated or at least minimized.

[0009] A specific object of the present invention is to provide an improved production line and an improved method for producing fiber webs, which improve sizing results, particularly in terms of increasing strength, reducing drying requirements and energy consumption, and achieving optimal use of sizing agents. Summary of the Invention

[0010] To achieve the above objectives, the main features of the production line for producing fiber webs according to the invention are those of the characterizing portion of the independent claim for the production line, and the main features of the method for producing fiber webs according to the invention are those of the characterizing portion of the independent claim for the method. Advantageous embodiments and features are disclosed in the dependent claims.

[0011] According to the present invention, the production line for producing fiber webs includes a forming section comprising at least one headbox and a forming unit comprising at least one net and at least one dewatering device, and the production line includes a sizing section comprising a sizing machine having a sizing roll gap formed between two sizing rolls, wherein the production line includes at least one application device located in the forming unit and configured to apply sizing agent in foam form for internal sizing of the fiber web, and the sizing machine located in the sizing section includes at least one application device configured to apply sizing agent for surface sizing of the fiber web.

[0012] According to an advantageous feature of the invention, the production line is used to produce a multiply-laid fiber web having at least two layers, and the forming unit of the production line includes at least one double-web forming component that forms between a web for a first layer of the multiply-laid fiber web and a web for a second layer of the multiply-laid fiber web, wherein the double-web components for each layer of the multiply-laid fiber web are engaged and the processed layers are combined, and the forming unit includes at least one application device for applying an sizing agent in foam form between at least two layers of the multiply-laid fiber web.

[0013] According to an advantageous feature of the invention, the production line is used to produce multi-lay fiber webs having at least three layers, wherein at least one application device is used to apply sizing agent in foam form to the top of a filler layer, which will be bonded to the top and back layers in the double-web component.

[0014] According to an advantageous feature of the invention, the application device located in the forming unit is a curtain application device, which is configured to apply the sizing agent in foam form.

[0015] According to an advantageous feature of the invention, the application device located in the sizing section is a curtain-type application device, which is connected and positioned to the sizing roller and is configured to apply the sizing agent indirectly in foam or liquid form via the surface of the sizing roller to the fiber web in the gap of the sizing roller.

[0016] According to an advantageous feature of the invention, the application device located in the forming unit is configured to apply the sizing agent in foam form according to the solid content, preferably 0.5%-20%, and the application device located in the sizing section is configured to apply the sizing agent with a high solid content, preferably 10%-60%, more preferably 20%-40%.

[0017] According to an advantageous feature of the invention, the application roller in the application section is a hard roller.

[0018] According to an advantageous feature of the invention, the forming unit of the production line includes a suction or negative pressure device located on the opposite side of the fiber web and its support mesh relative to the application device.

[0019] According to an advantageous feature of the invention, the fiber web production line includes an air guide located before the application device, the air guide preferably being an air curtain and / or reversing blades, for redirecting the boundary airflow away from the running direction of the fiber web before applying the sizing agent in a curtain-like manner in foam form.

[0020] According to an advantageous feature of the invention, the production line includes a metal strip calender or heat treatment device located in or after the sizing section.

[0021] According to the present invention, in a method for producing a fiber web having at least one layer, in a production line including a forming section, the forming section includes at least one headbox and a forming unit, in which the fiber web is supported by at least one net and water is removed from the fiber web by at least one dewatering device; the fiber web is sizing in a sizing section, the sizing section including a sizing machine having a sizing roll gap formed between two sizing rolls, wherein the interior of the fiber web is sizing by at least one application device located in the forming section and configured to apply sizing agent in foam form for interior sizing of the fiber web, and the fiber web is surface sizing by at least one application device located in the sizing section and configured to apply sizing agent for surface sizing of the fiber web.

[0022] According to an advantageous feature of the invention, in this method, a multi-layered fiber web having at least two layers is sizing by: applying the sizing agent in foam form for internal sizing of the fiber web, and applying the sizing agent by at least one application device located in the sizing section of the production line for surface sizing of the fiber web.

[0023] According to an advantageous feature of the invention, in this method, the sizing agent used for the internal sizing is applied in the form of a curtain foam.

[0024] According to an advantageous feature of the invention, in this method, the surface of the fiber web is sizing followed by heat treatment of the fiber web.

[0025] According to an advantageous feature of the invention, the sizing agent used for the surface sizing is applied with a high solids content, preferably 10%-60%, more preferably 20%-40%.

[0026] According to a key advantage of the invention, in the production of the fiber web, the sizing of the fiber web is carried out in at least two main sizing stages, including internal sizing of the fiber web and surface sizing of the fiber web. The term "internal sizing of the fiber web" refers to the sizing agent penetrating into the interior of the fiber web, particularly in the thickness direction of the web, while "surface sizing" refers to the main components of the sizing agent remaining near the surface of the fiber web.

[0027] Internal sizing of the fiber web provides internal strength and, in the case of a multi-ply fiber web, also improves the interlayer bond strength between the layers. Furthermore, internal sizing of the fiber web, by applying the sizing agent in foam form, can at least partially replace internal sizing in the headbox. Compared to applying the sizing agent by liquid dispersion, internal sizing of the fiber web in the forming section by applying the sizing agent in foam form improves the penetration and sizing effect of the sizing agent. Applying the sizing agent in foam form also allows for the use of a higher dosage of the sizing agent compared to internal sizing in the headbox. When the sizing agent is applied in foam form, the foam structure breaks down, absorbs, and diffuses into the surface structure of the web shortly after application, providing the possibility of using a large dosage of the sizing agent for faster absorption into the fiber web. Therefore, applying the sizing agent in foam form internally provides the possibility of using a smaller amount of sizing agent for surface sizing. Therefore, drying capacity needs to be reduced after surface sizing. The solution according to the invention provides optimal z-direction strength for the fiber web because internal sizing increases internal strength, allowing for concentrated sizing during surface sizing to create a rigid surface layer.

[0028] Surprisingly, the solution according to the invention has been found to form fiber webs with higher stiffness and strength. It has a so-called I-beam structure, where the surface is rigid, thus resulting in good flexural stiffness of the web. Furthermore, in the case of hard-roll gap sizing with high solids content in surface sizing, the requirement for drying capacity is reduced, and the fiber web surface becomes smoother, which reduces the need for calendering and thus preserves the fiber web mass. In general, the invention improves the stiffness of the board, interlayer bond strength, internal strength, and surface strength, and has better pre-coating properties.

[0029] This surface sizing stage improves the strength and impermeability of the fiber web surface. Furthermore, hydrophobic sizing can improve the flexural stiffness and moisture resistance of the fiber web.

[0030] Advantageously, the amount of sizing agent applied in the internal sizing stage is greater than that in the surface sizing stage.

[0031] Advantageously, the surface sizing agent has a higher solids content than the internal sizing agent.

[0032] Since internal sizing is performed first during surface sizing, high penetration is not required, and therefore a high-viscosity sizing agent can be used to effectively reinforce the surface of the fiber web. The possibility of using a high-viscosity sizing agent also reduces wet addition, thereby reducing the need for drying. Advantageously, the fiber web is sizing with a sizing agent with a viscosity of 5 cP (centipoise) or higher (preferably 5 cP-1000 cP, more preferably 20 cP-200 cP).

[0033] According to an advantageous aspect of the invention, the internal sizing of the fiber web is performed in the forming section of the fiber web production line by applying the sizing agent in foam form to the surface of the fiber web. Due to the suction of the dewatering device used in the forming section, the sizing agent is absorbed into the interior of the fiber web, which is further affected by the pressure of the press rolls in the pressing section of the fiber web production line. Therefore, an improved sizing effect is provided particularly inside the fiber web.

[0034] According to an advantageous aspect of the invention, internal sizing of the multiply fiber web is performed in the forming section of the fiber web production line by applying the sizing agent in foam form to the surface of at least one layer of the multiply fiber web and / or between at least two layers of the multiply fiber web. This provides a sizing effect particularly within the multiply fiber web and improves the interlayer bond strength between the layers of the multiply fiber web. Particularly in fiber webs with at least three layers, this improves the properties of the filler layers, such as internal strength and interlayer bond strength between the filler layers and the back and top layers.

[0035] Advantageously, the application device for internal sizing is a coater that forms a curtain-like sizing film, such as a trough-type or sliding curtain-type application device. The trough-type curtain-type application device is advantageous because it minimizes the residence time from the nozzle to the fiber web. Furthermore, the impact angle of the curtain jet can be more easily controlled by adjusting the tilt angle of the coater.

[0036] According to an advantageous aspect of the invention, surface sizing of the fiber web is performed after internal sizing of the fiber web, advantageously in a subsequent production section of the fiber web production line, i.e., in a section after the forming section of the fiber web production line. Advantageously, surface sizing of the fiber web is performed in a sizing machine in the sizing section of the fiber web production line after the pre-drying section. The sizing agent is applied directly or indirectly in the sizing machine using curtain technology, spraying technology, film transfer technology, or pool technology. Preferably, the sizing agent is applied using curtain technology. Advantageously, the fiber web is sizing with a high-solids-content sizing agent, preferably with a solids content of 10%-60%, more preferably with a solids content of 20%-40%. More preferably, the fiber web is sizing with a high-solids-content sizing agent using curtain technology. Advantageously, the sizing agent is starch.

[0037] Surface application in this sizing machine is advantageously performed using a hard-gap sizing machine, which includes a hard-gap sizing gap formed between two hard sizing rollers. Advantageously, rollers made of hard materials or rollers with hard coatings or covers are used as hard rollers. Advantageously, ceramic or metal rollers are used as hard rollers, or advantageously, rollers with hard polymer roller covers (rubber, polyurethane, or composite materials) having a surface hardness of 60 Shore D (Shore D) to 100 Shore D (advantageously 80 Shore D to 95 Shore D) are used. The hard-gap enhances the strength of the fiber web. Advantageously, the linear load in the sizing gap is 5 kN / m to 450 kN / m, more preferably 5 kN / m to 200 kN / m.

[0038] This surface sizing can be performed by applying the sizing agent in liquid or foam form using a foam application technique.

[0039] According to an advantageous aspect, the production line for the fiber web includes heat treatment of the fiber web in a metal strip calender or in the heat treatment zone of a heat treatment apparatus. When this heat treatment is performed in addition to surface sizing, the heat treatment enhances the effect of the sizing agent.

[0040] The heat treatment zone is advantageously formed between heated belt rings (particularly metal belt rings) and rolls (advantageously, hard rolls), or between two belt rings (particularly metal belt rings), at least one of which is advantageously heated. Advantageously, the length of the heat treatment zone is 0.2m-15m, advantageously 0.2m-5m. Advantageously, the surface temperature in the heat treatment zone is 100°C-250°C. Advantageously, the pressure in the heat treatment zone is 0.1MPa-30MPa, advantageously 0.1MPa-5MPa. This pressure includes at least one low basic pressure in the heat treatment zone, but in addition, the pressure in the heat treatment zone can be varied, for example, by using at least one high-pressure pulse generated by at least one additional roll gap (heat treatment roll gap) placed at a location in the heat treatment zone. Alternatively, a loading portion formed by a loading element located in the heat treatment zone can be used to change the pressure in the heat treatment zone. Advantageously, the residence time of the fiber web in the heat treatment zone is at least 20 ms, and advantageously 100 ms to 10,000 ms.

[0041] According to one embodiment of the invention, the internal sizing of the fiber web is carried out in the forming section by applying the sizing agent in foam form, while the surface sizing of the fiber web is carried out in a sizing machine, advantageously in a hard-gap sizing machine.

[0042] According to another embodiment of the invention, the internal sizing of the fiber web is carried out in the forming section by applying the sizing agent in foam form, while the surface sizing of the fiber web is carried out in a sizing machine, advantageously in a hard-gap sizing machine by using a curtain application of the sizing agent with a high solids content.

[0043] According to another embodiment of the invention, the internal sizing of the fiber web is carried out in the forming section by applying the sizing agent in foam form, while the surface sizing of the fiber web is carried out in a sizing machine, advantageously in a hard-gap sizing machine by curtain application using the sizing agent with a high solids content, and is carried out as heat treatment in the heat treatment zone of a heat treatment apparatus, advantageously by heat treatment of a metal strip.

[0044] Advantageously, the fiber web production line includes a final calendering stage in a final calender after the surface sizing stage.

[0045] The fiber web production line may also include a coating section with a coating machine and drying equipment.

[0046] According to an advantageous aspect of the invention, the sizing agent applied in foam form during internal sizing penetrates deeply into the structure of the fiber web, and advantageously, the delivery and penetration of the sizing agent in foam form is guided to the desired direction and depth by means of a dehydration device and by controlling the amount and viscosity of the foam, and sizing in the boundary region between these layers to be joined is effective by delivering the sizing agent to two layers on each side of the boundary of the web layers to be joined.

[0047] According to an advantageous aspect of the invention, the multi-layered fiber web is paperboard, such as folding boxboard (FBB), white-lined cardboard (WLC), solid bleached board (SBS), or liquid packaging board (LPB). Furthermore, the multi-layered paperboard is advantageously boxboard, such as pure kraft paper (KL), imitation kraft paper (TL), or white board (WTL). Attached Figure Description

[0048] The invention will be described in detail below with reference to the accompanying drawings, but the invention is not limited thereto.

[0049] Figure 1 An advantageous example of a production line for producing fiber webs according to the present invention is illustrated schematically.

[0050] Figure 2 Another advantageous example of a production line for producing fiber webs according to the present invention is illustrated schematically.

[0051] Figure 3 Another advantageous example of a production line for producing fiber webs according to the present invention is illustrated schematically.

[0052] Figure 4 Another advantageous example of a production line for producing fiber webs according to the present invention is illustrated schematically. Detailed Implementation

[0053] In the course of the following description, similar numbers and symbols are used to identify similar elements according to different views illustrating the invention and its advantageous examples. In the accompanying drawings, some repeated reference numerals have been omitted for clarity.

[0054] Figure 1 An example of a production line 200 for producing two-layer fiber webs W is shown. In this example, the production line 200 includes a forming section 210, a pressing section 230, and a subsequent drying section 240 and a winding unit 280. The forming section includes two headboxes M10 and M20 and a forming unit 220. In this example, the production line 200 also includes a sizing section 250, which has a drying unit 260 and a calender 105.

[0055] In this example, the forming section 210 is used to produce multi-lay fiber webs, specifically, to produce double-layer W10, W20 fiber webs W. The forming section includes headboxes M10 and M20 for each layer W10, W20. A raw material suspension is fed from the headboxes to a forming unit 220, which initially consists of a single-web component comprising a web 10 for the first layer W10 of the multi-lay fiber web W and a web 20 for the second layer W20 of the multi-lay fiber web W. Each web 10, 20 includes rollers 12, 22 for guiding, tensioning, and / or driving the web 10, 20 to form an endless loop. The raw material suspensions M10, M20 are first fed onto the webs 10, 20, and then the material on the web is guided through dewatering devices 11, 21, 15, 25 located within the loops of the webs 10, 20. At least one suction device 15, 25 is located within the loops of the webs 10, 20. During operation of the single-web unit, the dehydration from the web is substantially horizontal. Curtain application devices C10 and C20 are located on the running path of the raw material layer. This single-web unit is used to apply sizing agent in foam form to the pre-dehydrated fiber web and between the layers of the multi-lay fiber web in the forming section via the curtain application devices. The curtain application devices C10 and C20 are advantageously positioned such that suction devices 15 and 25 are located on opposite sides of the multi-lay fiber web within the rings of the webs 10 and 20. Additionally, air guides 14 and 24 (preferably air curtains and / or reversing blades) are positioned above the respective webs 10 and 20 prior to the curtain application devices C10 and C20 to redirect the boundary air layer and thus prevent the boundary air layer from interfering with the curtain of sizing agent applied in foam form by the curtain application devices C10 and C20.

[0056] Alternatively, only one foam application device C10 or C20 can be used, with device C10 advantageously applying the foam to the fiber web layer on the lower web 10. Foam application device C20 can also be used only on the fiber web on the upper web 20. As shown in the example, two application devices C10 or C20 can also be used. Furthermore, more than one application device C10 or C20 can be used continuously on a single fiber web layer.

[0057] After the single-web component is guided downward to the first web 10, the raw material for forming the second layer W20 of the multi-layer fiber web W is guided onto the web 20. The running paths of the first layer W10 web 10 and the second layer W20 web 20 are joined by the connecting roller 23 to form a double-web component, and the web material for the first layer W10 and the second layer W20 is guided into the gaps formed between the webs 10 and 20. These webs form the double-web component of the forming unit. The web layers W10 and W20 have been joined together at the beginning of the double-web forming component by the connecting roller 23. The connecting roller 23 is located in the second web ring 20. Therefore, the sizing agent applied in foam form to each layer W10 and W20 of the web W by the curtain application devices C10 and C20 is guided between the layers. Advantageously, after the sizing agent is applied in foam form via the curtain application device C10, its delivery and penetration into the web layer are assisted, allowing the sizing agent to be pushed deeper into the web layer on which the sizing agent was applied in foam form by guiding the foam in the desired direction. In the example of the accompanying drawings, suction devices 15, 25 are disposed inside the web rings 10, 20, which assist in delivering and penetrating the sizing agent into the web layer during and after the application of the sizing agent in foam form via the curtain application devices C10, C20, but before the web layer is joined at the beginning of the double-web forming member by the joining roller 23. Furthermore, double-sided dehydration can be used in one or more forming units before the application of the sizing agent, which is achieved by using a separate web ring on top of the single-web member.

[0058] After layers W10 and W20 are joined, the multiply fiber web W is guided onto the web 10, which serves as a single-web component supporting the first side of the multiply fiber web W. During this operation, a support foil 16 is located within a loop of the web 10. The support foil 16 does not deflect the running path of the web 10, but only removes water from the first surface of the web 10, and supports the operation of the web 10 as the multiply fiber web is guided via suction roller 13 to pick-up roller 41 to transfer the multiply fiber web to the first press fabric 40 of the press section 230. The press section also includes a second press fabric 50 with rollers 51. The press fabrics 40 and 50 include rollers 42 and 52 for guiding, tensioning, and / or driving the fabrics 40 and 50 to form an endless loop. In this press section, the multiply fiber web W is guided between the first press fabric 40 and the second press fabric 50 into a press roll gap formed between the first press roller 45 and the second press roller 55. In this example, the press section 230 includes two sets of press fabrics 40, 50, each set having rollers 42, 52 for guiding, tensioning, and / or driving the fabrics 40, 50 to form endless loops, and a press roll gap formed between a first press roller 45 and a second press roller 55. The absorption of sizing agent into the interior of the fiber web W is further influenced by the pressure of the press roll gap between the press rollers 45, 55 in the press section 230. After the press section, the fiber web is guided to the drying section 240.

[0059] The drying section 240 includes apparatus for drying the fiber web W. In this example, only the beginning of the drying section is shown, where drying is achieved by a single-web drying cylinder assembly, which includes a drying web 60 with a pick-up roller 61, rollers 62 for guiding, tensioning, and / or driving the drying web 60, a reversing roller 63, and a drying cylinder 64. The drying section 240 typically includes several drying assemblies with single or double web traction. Alternatively, other types of drying apparatus may be used. Following the drying section 240 is the sizing section 250 with drying units 260.

[0060] In the sizing section of this example, the fiber web travels from the guide roller 72 in a substantially vertically downward direction. Indirect sizing of the fiber web W is performed by two curtain-type application devices C75, each located at the sizing roller 75, by first applying the sizing agent to the surface of the respective rotating sizing roller 75 and then guiding the sizing agent into the sizing gap formed between the sizing rollers 75. Air guides 74 (preferably air curtains and / or reversing blades) are provided in the rotation direction of the sizing rollers 75 to redirect the boundary air layer and thus prevent the boundary air layer from interfering with the curtain of sizing agent applied by the curtain-type application devices C75. In this example, the fiber web W is sizing on both sides, but it is also possible to sizing only one side of the fiber web W, in which case only one roller of the sizing rollers 75 is provided with a curtain-type application device C75 and an air guide 74. Advantageously, the sizing rollers 75 are hard rollers, i.e., they are provided with hard-gap sizing machines. Advantageously, ceramic or metal rollers are used as hard rollers, or advantageously, rollers with a hard polymer roller cover (rubber, polyurethane, or composite material) having a surface hardness of 60 shoreD-100 shoreD (advantageously 80 shoreD-95 shoreD) are used. The hardened roller gap enhances the strength. Advantageously, the linear load in the sizing roller gap is 5 kN / m-450 kN / m, more preferably 5 kN / m-200 kN / m. Advantageously, the sizing agent is a high-solids sizing agent, which advantageously comprises a fiber suspension, preferably with a solids content of 10%-60%, more preferably 20%-40%. The viscosity of the sizing agent is advantageously 5 cP or higher, preferably 5 cP-1000 cP, more preferably 20 cP-200 cP. One of the rollers in the hardened sizing rollers 75 is a deflection compensation roller, thus forming a vertical sizing roller gap. A curtain-type application device, positioned and connected to each application roller 75, applies sizing agent to the surface of the application roller 75, and applies sizing agent to the fiber web W indirectly. The sizing agent is then guided from the surface of the application roller 75 to the surface of the fiber web W, such that it is squeezed onto the fiber web surface within the gap between the application rollers. After sizing, the fiber web W is guided via an air-support drying device 87 of the drying unit 260, which first dries the sizing agent to prevent it from adhering to the subsequent drying cylinder 84 in the drying unit 260. The fiber web W is further dried in the drying unit 260, in this example including single-web drying and double-web drying. In single-web drying, the fiber web W is supported and operated by a drying web 80 via a drying cylinder 84 and a reversing roller 83. The drying web 80 operates as a supported closed loop and is provided with rollers 82 for guiding, tensioning, and / or driving the drying web 80. The drying unit 260 also includes a double-net dryer, wherein the fiber web W is dried by drying cylinders 94U and 94L arranged in two rows.Each row has its own drying net 90U, 90L and rollers 92U, 92L for guiding, tensioning and / or driving the corresponding drying net 90U, 90L. Between rows, the fiber web W has free traction.

[0061] After the sizing section 250 with drying unit 260, the fiber web is guided to the calendering section 270, which in this example includes a calendering roll gap formed between calendering rolls 105 and 106. A coating section with a coater and drying equipment can be provided after the pre-calender, and a final calender (not shown) can also be provided after the coating section. The fiber web W is then guided to the paper winding unit 280, in which the fiber web W is wound onto the master roll 115 by the winding drum 116.

[0062] Figure 2 An example of a production line 200 for producing two-layer fiber webs W is shown. In this example, the production line 200 includes a forming section 210, a pressing section 230, and a subsequent drying section 240 and a winding unit 280. The forming section includes two headboxes M10 and M20 and a forming unit 220. In this example, the production line 200 also includes a sizing section 250, which has a drying unit 260 and a calender 105.

[0063] In this example, the forming section 210 is used to produce multi-lay fiber webs, specifically, to produce double-layer W10, W20 fiber webs W. The forming section includes headboxes M10 and M20 for each layer W10, W20. A raw material suspension is fed from the headboxes to a forming unit 220, which initially consists of a single-web component comprising a web 10 for the first layer W10 of the multi-lay fiber web W and a web 20 for the second layer W20 of the multi-lay fiber web W. Each web 10, 20 includes rollers 12, 22 for guiding, tensioning, and / or driving the web 10, 20 to form an endless loop. The raw material suspensions M10, M20 are first fed onto the webs 10, 20, and then the material on the web is guided through dewatering devices 11, 21, 15, 25 located within the loops of the webs 10, 20. At least one suction device 15, 25 is located within the loops of the webs 10, 20. During operation of the single-web unit, the dehydration from the web is substantially horizontal. Curtain application devices C10 and C20 are located on the operating path of the single-web unit, which applies sizing agent in foam form to the pre-dehydrated fiber web and between the layers of the multi-lay fiber web in the forming section. The curtain application devices C10 and C20 are advantageously positioned such that suction devices 15 and 25 are located on opposite sides of the multi-lay fiber web within the rings of the webs 10 and 20. Additionally, air guides 14 and 24 (preferably air curtains and / or reversing blades) are positioned above the respective webs 10 and 20 prior to the curtain application devices C10 and C20 to redirect the boundary air layer and thus prevent the boundary air layer from interfering with the curtain of sizing agent applied in foam form by the curtain application devices C10 and C20.

[0064] After the single-web component is guided downward to the first web 10, the raw material for forming the second layer W20 of the multi-layer fiber web W is guided onto the web 20. The running paths of the first layer W10 web 10 and the second layer W20 web 20 are joined by the connecting roller 23 to form a double-web component, and the web material for the first layer W10 and the second layer W20 is guided into the gaps formed between the webs 10 and 20. These webs form the double-web component of the forming unit. The web layers W10 and W20 have been joined together at the beginning of the double-web forming component by the connecting roller 23. The connecting roller 23 is located in the second web ring 20. Therefore, the sizing agent applied in foam form to each layer W10 and W20 of the web W by the curtain application devices C10 and C20 is guided between the layers. Advantageously, after the sizing agent is applied in foam form via the curtain application devices C10, C20, it is assisted in being transported and penetrated into the web layer, such that the sizing agent is pushed deeper into the web layer on which the sizing agent was applied in foam form by guiding the foam in the desired direction. In the example of the accompanying drawings, suction devices 15, 25 are disposed inside the web rings 10, 20, which assist in transporting and penetrating the sizing agent into the web layer during and after the application of the sizing agent in foam form via the curtain application devices C10, C20, but before the web layer is joined at the beginning of the double-web forming member by the joining roller 23. Furthermore, double-sided dehydration can be used in one or more forming units before the application of the sizing agent, which is achieved by using a separate web ring on top of the single-web member.

[0065] After layers W10 and W20 are joined, the multiply fiber web W is guided onto the first side of the web 10, which serves as a single-web component supporting the multiply fiber web W. During this operation, a support foil 16 is located within the loop of the web 10. The support foil 16 does not deflect the running path of the web 10, but only removes water from the first surface of the web 10, and supports the operation of the web 10 as the multiply fiber web W is guided forward onto it. In conjunction with this operation of the web 10, another curtain-type application device C50 is provided for applying sizing agent to the surface of the multiply fiber web W. This curtain-type application device C50 is advantageously positioned such that a suction device 56 is located on the opposite side of the multiply fiber web W within the loop of the web 10. Additionally, an air guide 54 (preferably an air curtain and / or a reversing blade) is positioned above the corresponding net 10 at a location prior to the curtain application device C50 to redirect the boundary air layer and thus prevent the boundary air layer from interfering with the curtain of the sizing agent applied in foam form by the curtain application device C50.

[0066] Alternatively, only one foam application device C10, C20, or C50 can be used, which advantageously applies the foam to the fiber web layer on the lower web 10. The foam application device C20 can also be used only on the fiber web on the upper web 20. As shown in the example, three application devices C10, C20, or C50 can also be used. Furthermore, two application devices C10, C20, or C50 can also be used. Additionally, more than one application device C10, C20, or C50 can be used continuously on a single fiber web layer.

[0067] Following the forming section 210, the fiber web W is guided via the suction roller 13 of the forming unit 220 to the pick-up roller 41 for transferring the multiply fiber web to the first press fabric 40 of the press section 230. This press section also includes a second press fabric 50 with rollers 51. The press fabrics 40 and 50 include rollers 42 and 52 for guiding, tensioning, and / or driving the fabrics 40 and 50 to form endless loops. In this press section, the multiply fiber web W is guided between the first press fabric 40 and the second press fabric 50 to a press roll gap formed between the first press roller 45 and the second press roller 55. In this example, the press section 230 includes two sets of press fabrics 40, 50, each set having rollers 42, 52 for guiding, tensioning, and / or driving the fabrics 40, 50 to form endless loops, and a press roll gap formed between a first press roller 45 and a second press roller 55. The absorption of sizing agent into the interior of the fiber web W is further influenced by the pressure of the press roll gap between the press rollers 45, 55 in the press section 230. After the press section, the fiber web is guided to the drying section 240.

[0068] The drying section 240 includes apparatus for drying the fiber web W. In this example, only the beginning of the drying section is shown, where drying is achieved by a single-web drying cylinder assembly, which includes a drying web 60 with a pick-up roller 61, rollers 62 for guiding, tensioning, and / or driving the drying web 60, a reversing roller 63, and a drying cylinder 64. The drying section 240 typically includes several drying assemblies with single or double web traction. Alternatively, other types of drying apparatus may be used. Following the drying section 240 is the sizing section 250 with drying units 260.

[0069] In the sizing section of this example, the fiber web travels from the guide roller 72 in a substantially vertically upward direction. Indirect sizing of the fiber web W is performed by two curtain-type application devices C75, each located at the sizing roller 75, by first applying the sizing agent to the surface of the respective rotating sizing roller 75 and then guiding the sizing agent into the sizing gap formed between the sizing rollers 75. Air guides 74 (preferably air curtains and / or reversing blades) are provided in the rotation direction of the sizing rollers 75 to redirect the boundary air layer and thus prevent the boundary air layer from interfering with the curtain of sizing agent applied by the curtain-type application devices C75. In this example, the fiber web W is sizing on both sides, but it is also possible to sizing only one side of the fiber web W, in which case only one roller of the sizing rollers 75 is provided with a curtain-type application device C75 and an air guide 74. Advantageously, the sizing rollers 75 are hard rollers, i.e., they are provided with hard-gap sizing machines. Advantageously, ceramic or metal rollers are used as hard rollers, or advantageously, rollers with a hard polymer roller cover (rubber, polyurethane, or composite material) having a surface hardness of 60 shoreD-100 shoreD (advantageously 80 shoreD-95 shoreD) are used. The hardened roller gap enhances the strength. Advantageously, the linear load in the sizing roller gap is 5 kN / m-450 kN / m, more preferably 5 kN / m-200 kN / m. Advantageously, the sizing agent is a high-solids sizing agent, which advantageously comprises a fiber suspension, preferably with a solids content of 10%-60%, more preferably 20%-40%. The viscosity of the sizing agent is advantageously 5 cP or higher, preferably 5 cP-1000 cP, more preferably 20 cP-200 cP. One of the rollers in the hardened sizing rollers 75 is a deflection compensation roller, thus forming a vertical sizing roller gap. A curtain-type application device, positioned and connected to each application roller 75, applies sizing agent to the surface of the application roller 75, and applies sizing agent to the fiber web W indirectly. The sizing agent is then guided from the surface of the application roller 75 to the surface of the fiber web W, such that it is squeezed onto the fiber web surface within the gap between the application rollers. After sizing, the fiber web W is guided via an air-support drying device 87 of the drying unit 260, which first dries the sizing agent to prevent it from adhering to the subsequent drying cylinder 84 in the drying unit 260. The fiber web W is further dried in the drying unit 260, in this example including single-web drying and double-web drying. In single-web drying, the fiber web W is supported and operated by a drying web 80 via a drying cylinder 84 and a reversing roller 83. The drying web 80 operates as a supported closed loop and is provided with rollers 82 for guiding, tensioning, and / or driving the drying web 80. The drying unit 260 also includes a double-net drying system, wherein the fiber web W is dried by drying cylinders 94U and 94L arranged in two rows.Each row has its own drying web 90U, 90L and rollers 92U, 92L for guiding, tensioning and / or driving the corresponding drying web 90U, 90L. Between rows, the fiber web W has free traction. Drying unit 260.

[0070] After the sizing section 250 with drying unit 260, the fiber web is guided to the calendering section 270, which in this example includes a calendering roll gap formed between calendering rolls 105 and 106. A coating section with a coater and drying equipment can be provided after the pre-calender, and a final calender (not shown) can also be provided after the coating section. The fiber web W is then guided to the paper winding unit 280, in which the fiber web W is wound onto the master roll 115 by the winding drum 116.

[0071] Figure 3 An example of a production line 200 for producing single-layer fiber webs W using a single-layer headbox or for producing multi-layer fiber webs W using a multi-layer headbox is shown. In this example, the production line 200 includes a forming section 210, a pressing section 230, a subsequent drying section 240, and a reel assembly 280. The forming section includes a headbox M10 and a forming unit 220. In this example, the production line 200 also includes a sizing section 250, which has a drying unit 260 and a calender 105.

[0072] In this example, the forming section 210 for producing the fiber web W may include one or more fiber web layers. The forming section 210 includes a headbox M10 from which a raw material suspension is fed to a forming unit 220, which initially consists of a single-web component including a web 10 for single-web operation and a web 20 for double-web operation, for forming the fiber web W. In the case of manufacturing a single-layer fiber web, only one type of raw material suspension is fed to the headbox M10; however, in the case of manufacturing a multi-layer fiber web, two or more of the same or different types of raw material suspensions are fed to the headbox M10. The raw material suspensions may vary depending on the raw material, fiber length, fiber freeness, or additives. Each web 10, 20 includes rollers 12, 22 for guiding, tensioning, and / or driving the web 10, 20 to form an endless loop. First, the raw material suspension M10 is fed onto the web 10, and then the raw material on the web is guided through dewatering devices 17, 11 located in the loops of the web 10, 20. The first dewatering device 17 is advantageously a forming shoe 17, which is advantageously under pressure and can have a configured surface such that the forming shoe 17 does not generate a large number of pressure pulses; that is, the forming shoe 17 can be a so-called non-pulsating forming shoe 17. The non-pulsating forming shoe 17 can be formed by strips transverse to the machine direction, which are arranged sequentially at small intervals in the machine direction, and the forming shoe cover is straight. During operation on the web 10, the dewatering of the fiber web is substantially horizontal. After the first single-web operation is a double-web operation, during which the fiber web runs between two webs 10, 20. During this double-web operation, water is removed by dewatering devices 18, 19, 16. In this example, the first dewatering device 18 is a suction box 18 with pulsating dewatering, which has optional adjustable loading blades P in the opposing web rings 10, and the second dewatering device in this example is a suction box 19, since the suction box can be used as the third dewatering device 16. The suction box 16 ensures separation of the fiber web from the net 20 and also serves as a support device for the operation of the fiber web W. Following the double-net operation is another single-net operation, in which a curtain application device C50 is positioned to apply the sizing agent to the surface of the fiber web W in foam form. The curtain application device C50 is advantageously positioned such that the suction device 56 is located on the opposite side of the fiber web W within the loop of the net 10. Additionally, an air guide 54, preferably an air curtain and / or reversing blades, is positioned above the corresponding net 10 prior to the curtain application device C50 to redirect the boundary air layer and thus prevent the boundary air layer from interfering with the curtain of sizing agent applied in foam form by the curtain application device C50.

[0073] Following the forming section 210, the fiber web W is guided via the suction roller 13 of the forming unit 220 to the pick-up roller 41 for transferring the fiber web to the first press fabric 40 of the press section 230. This press section also includes a second press fabric 50 having rollers 51. The press fabrics 40 and 50 include rollers 42 and 52 for guiding, tensioning, and / or driving the fabrics 40 and 50 to form endless loops. In this press section, the fiber web W is guided between the first press fabric 40 and the second press fabric 50 to a press roll gap formed between the first press roller 45 and the second press roller 55. In this example, the press section 230 includes two sets of press fabrics 40 and 50 having rollers 42 and 52 for guiding, tensioning, and / or driving the fabrics 40 and 50 to form endless loops, and a press roll gap formed between the first press roller 45 and the second press roller 55. The sizing agent absorbed into the interior of the fiber web W is further affected by the pressure of the press roll gap between the press rolls 45 and 55 in the press section 230. After the press section, the fiber web is guided to the drying section 240.

[0074] The drying section 240 includes apparatus for drying the fiber web W. In this example, only the beginning of the drying section is shown, where drying is achieved by a single-web drying cylinder assembly, which includes a drying web 60 with a pick-up roller 61, rollers 62 for guiding, tensioning, and / or driving the drying web 60, a reversing roller 63, and a drying cylinder 64. The drying section 240 typically includes several drying assemblies with single or double web traction. Alternatively, other types of drying apparatus may be used. Following the drying section 240 is the sizing section 250 with drying units 260.

[0075] In the sizing section of this example, the fiber web travels from the guide roller 72 in a substantially vertically upward direction. Indirect sizing of the fiber web W is performed by two curtain-type application devices C75, each located at the sizing roller 75, by first applying the sizing agent to the surface of the respective rotating sizing roller 75 and then guiding the sizing agent into the sizing gap formed between the sizing rollers 75. Air guides 74 (preferably air curtains and / or reversing blades) are provided in the rotation direction of the sizing rollers 75 to redirect the boundary air layer and thus prevent the boundary air layer from interfering with the curtain of sizing agent applied by the curtain-type application devices C75. In this example, the fiber web W is sizing on both sides, but it is also possible to sizing only one side of the fiber web W, in which case only one roller of the sizing rollers 75 is provided with a curtain-type application device C75 and an air guide 74. Advantageously, the sizing rollers 75 are hard rollers, i.e., they are provided with hard-gap sizing machines. Advantageously, ceramic or metal rollers are used as hard rollers, or advantageously, rollers with a hard polymer roller cover (rubber, polyurethane, or composite material) having a surface hardness of 60 shoreD-100 shoreD (advantageously 80 shoreD-95 shoreD) are used. The hardened roller gap enhances the strength. Advantageously, the linear load in the sizing roller gap is 5 kN / m-450 kN / m, more preferably 5 kN / m-200 kN / m. Advantageously, the sizing agent is a high-solids sizing agent, which advantageously comprises a fiber suspension, preferably with a solids content of 10%-60%, more preferably 20%-40%. The viscosity of the sizing agent is advantageously 5 cP or higher, preferably 5 cP-1000 cP, more preferably 20 cP-200 cP. One of the rollers in the hardened sizing rollers 75 is a deflection compensation roller, thus forming a vertical sizing roller gap. A curtain-type application device, positioned and connected to each application roller 75, applies sizing agent to the surface of the application roller 75, and applies sizing agent to the fiber web W indirectly. The sizing agent is then guided from the surface of the application roller 75 to the surface of the fiber web W, such that it is squeezed onto the fiber web surface within the gap between the application rollers. After sizing, the fiber web W is guided via an air-support drying device 87 of the drying unit 260, which first dries the sizing agent to prevent it from adhering to the subsequent drying cylinder 84 in the drying unit 260. The fiber web W is further dried in the drying unit 260, in this example including single-web drying and double-web drying. In single-web drying, the fiber web W is supported and operated by a drying web 80 via a drying cylinder 84 and a reversing roller 83. The drying web 80 operates as a supported closed loop and is provided with rollers 82 for guiding, tensioning, and / or driving the drying web 80. The drying unit 260 also includes a double-net drying system, wherein the fiber web W is dried by drying cylinders 94U and 94L arranged in two rows.Each row has its own drying net 90U, 90L and rollers 92U, 92L for guiding, tensioning and / or driving the corresponding drying net 90U, 90L. Between rows, the fiber web W has free traction.

[0076] After the sizing section 250 with drying unit 260, the fiber web is guided to the calendering section 270, which in this example includes a calendering roll gap formed between calendering rolls 105 and 106. A coating section with a coater and drying equipment can be provided after the pre-calender, and a final calender (not shown) can also be provided after the coating section. The fiber web W is then guided to the paper winding unit 280, in which the fiber web W is wound onto the master roll 115 by the winding drum 116.

[0077] Figure 4 An example of a production line 200 for producing three-layer fiber webs W is shown. In this example, the production line 200 includes a forming section 210, a pressing section 230, and a subsequent drying section 240 and a winding unit 280. The forming section includes three headboxes M10, M20, and M30 and a forming unit 220. In this example, the production line 200 also includes a sizing section 250, which has a drying unit 260 and a calender 105.

[0078] In this example, the forming section 210 is used to produce a multi-layer fiber web, specifically a three-layer fiber web W of layers W10, W20, and W30. The forming section includes headboxes M10, M20, and W30 for each layer W10, W20, and W30. A raw material suspension is fed from the headboxes to the forming unit 220, which initially consists of a single-web component including a web 10 for the first layer W10 of the multi-layer fiber web W, a web 20 for the second layer W20 of the multi-layer fiber web W, and a web 30 for the third layer of the multi-layer fiber web W. Each web 10, 20, and 30 includes rollers 12, 22, and 32 for guiding, tensioning, and / or driving the web 10, 20, and 30 to form an endless loop. The first layer W10 can be referred to as the back layer of the multi-ply fiber web W, the second layer W20 can be referred to as the top layer of the multi-ply fiber web W, and the third layer W30 can be referred to as the filler layer of the multi-ply fiber web W. First, the raw material suspensions M10, M20, and M30 are fed onto nets 10, 20, and 30, and then the raw material on the nets is guided through dewatering devices 11, 21, 31, 15, 25, and 35 located in the rings of the nets 10, 20, and 30. At least one suction device 15, 25, or 35 is located in the rings of the nets 10, 20, and 35. During operation of the single-net component, dewatering from the fiber web is substantially horizontal. Curtain application devices C10, C20, and C30 are located on the running path of the raw material layer. This single-net component is used to apply sizing agent in foam form to the raw material layer and between the layers of the multi-ply fiber web in the forming section via the curtain application devices. The curtain application devices C10, C20, and C30 are advantageously positioned such that the suction devices 15, 25, and 35 are located on opposite sides of the multi-layered fiber web within the rings of the nets 10, 20, and 30. Additionally, air guides 14, 24, and 34 (preferably air curtains and / or reversing blades) are positioned above the corresponding nets 10, 20, and 30 prior to the curtain application devices C10, C20, and C30 to redirect the boundary air layer and thus prevent the boundary air layer from interfering with the curtain of sizing agent applied in foam form by the curtain application devices C10, C20, and C30.

[0079] After the single-web component is guided downward to the first web 10, the raw materials for forming the second layer W20 and the third layer W30 of the multi-layer fiber web W are guided onto webs 20 and 30. The running paths of web 10 of the first layer W10, web 20 of the second layer W20, and web 30 of the third layer W30 are joined by a connecting roller 23 to form a double-web component. The webs for the first layer W10, the second layer W20, and the third layer W30 are guided into the gaps formed between webs 10 and 20. These webs form the double-web component of the forming unit. The web layers W10, W20, and W30 have been joined together at the beginning of the double-web forming component by the connecting roller 23. The connecting roller 23 is located in the second web ring 20. Therefore, the sizing agent applied in foam form to each layer W10, W20, and W30 of the web W by the curtain application devices C10, C20, and C30 is guided between the layers. Advantageously, after the sizing agent is applied in foam form via the curtain application devices C10, C20, and C30, its delivery and penetration into the web layer are assisted, allowing the sizing agent to be pushed deeper into the web layer on which the sizing agent was applied in foam form by guiding the foam in the desired direction. In the example of the accompanying drawings, suction devices 15, 25, and 35 are disposed inside the web rings 10, 20, and 30, assisting in the delivery and penetration of the sizing agent into the web layer during and after the application of the sizing agent in foam form via the curtain application devices C10, C20, and C30, but before the web layer is joined at the beginning of the double-web forming member by the joining roller 23. Furthermore, double-sided dehydration can be used in one or more forming units before the application of the sizing agent, which is achieved by using a separate web ring on top of the single-web member. This is particularly advantageous for layers with higher basis weights, such as filler layers that typically have a higher basis weight than the back and top layers.

[0080] Alternatively, only one foam application device C10, C20, C30, or C50 can be used, which advantageously applies the foam to the fiber web layer on the lower web 10. The foam application devices C20 and C30 can also be applied only to the fiber webs on the upper webs 20 and 30. Advantageously, the application device C30 applies the sizing agent in foam form to the top of the filler layer, which will be combined with the top and back layers in the double-web component. As shown in the example, four application devices C10, C20, C30, or C50 can also be used. Furthermore, two or three application devices C10, C20, C30, or C50 can also be used. Additionally, more than one application device C10, C20, C30, or C50 can be used continuously on a single fiber web layer.

[0081] After layers W10, W20, and W30 are joined, the multiply fiber web W is guided onto the web 10, which serves as a single-web component supporting the first side of the multiply fiber web W. During this operation, a support foil 16 is located within the loop of the web 10. The support foil 16 does not deflect the running path of the web 10, but only removes water from the first surface of the web 10, and supports the operation of the web 10 as the multiply fiber web W is guided forward onto it. In conjunction with this operation of the web 10, another curtain-type application device C50 is provided for applying sizing agent to the surface of the multiply fiber web W. This curtain-type application device C50 is advantageously positioned such that a suction device 56 is located on the opposite side of the multiply fiber web W within the loop of the web 10. Additionally, an air guide 54 (preferably an air curtain and / or a reversing blade) is positioned above the corresponding net 10 at a location prior to the curtain application device C50 to redirect the boundary air layer and thus prevent the boundary air layer from interfering with the curtain of the sizing agent applied in foam form by the curtain application device C50.

[0082] Following the forming section 210, the fiber web W is guided via the suction roller 13 of the forming unit 220 to the pick-up roller 41 for transferring the multiply fiber web to the first press fabric 40 of the press section 230. This press section also includes a second press fabric 50 with rollers 51. The press fabrics 40 and 50 include rollers 42 and 52 for guiding, tensioning, and / or driving the fabrics 40 and 50 to form endless loops. In this press section, the multiply fiber web W is guided between the first press fabric 40 and the second press fabric 50 to a press roll gap formed between the first press roller 45 and the second press roller 55. In this example, the press section 230 includes two sets of press fabrics 40, 50, each set having rollers 42, 52 for guiding, tensioning, and / or driving the fabrics 40, 50 to form endless loops, and a press roll gap formed between a first press roller 45 and a second press roller 55. The absorption of sizing agent into the interior of the fiber web W is further influenced by the pressure of the press roll gap between the press rollers 45, 55 in the press section 230. After the press section, the fiber web is guided to the drying section 240.

[0083] The drying section 240 includes apparatus for drying the fiber web W. In this example, only the beginning of the drying section is shown, where drying is achieved by a single-web drying cylinder assembly, which includes a drying web 60 with a pick-up roller 61, rollers 62 for guiding, tensioning, and / or driving the drying web 60, a reversing roller 63, and a drying cylinder 64. The drying section 240 typically includes several drying assemblies with single or double web traction. Alternatively, other types of drying apparatus may be used. Following the drying section 240 is the sizing section 250 with drying units 260.

[0084] In the sizing section of this example, the fiber web travels from the guide roller 72 in a substantially vertically downward direction. Indirect sizing of the fiber web W is performed by two curtain-type application devices C75, each located at the sizing roller 75, by first applying the sizing agent to the surface of the respective rotating sizing roller 75 and then guiding the sizing agent into the sizing gap formed between the sizing rollers 75. Air guides 74 (preferably air curtains and / or reversing blades) are provided in the rotation direction of the sizing rollers 75 to redirect the boundary air layer and thus prevent the boundary air layer from interfering with the curtain of sizing agent applied by the curtain-type application devices C75. In this example, the fiber web W is sizing on both sides, but it is also possible to sizing only one side of the fiber web W, in which case only one roller of the sizing rollers 75 is provided with a curtain-type application device C75 and an air guide 74. Advantageously, the sizing rollers 75 are hard rollers, i.e., they are provided with hard-gap sizing machines. Advantageously, ceramic or metal rollers are used as hard rollers, or advantageously, rollers with a hard polymer roller cover (rubber, polyurethane, or composite material) having a surface hardness of 60 shoreD-100 shoreD (advantageously 80 shoreD-95 shoreD) are used. The hardened roller gap enhances the strength. Advantageously, the linear load in the sizing roller gap is 5 kN / m-450 kN / m, more preferably 5 kN / m-200 kN / m. Advantageously, the sizing agent is a high-solids sizing agent, which advantageously comprises a fiber suspension, preferably with a solids content of 10%-60%, more preferably 20%-40%. The viscosity of the sizing agent is advantageously 5 cP or higher, preferably 5 cP-1000 cP, more preferably 20 cP-200 cP. One of the rollers in the hardened sizing rollers 75 is a deflection compensation roller, thus forming a vertical sizing roller gap. A curtain-type application device, positioned and connected to each application roller 75, applies sizing agent to the surface of the application roller 75, and applies sizing agent to the fiber web W indirectly. The sizing agent is then guided from the surface of the application roller 75 to the surface of the fiber web W, such that it is squeezed onto the fiber web surface within the gap between the application rollers. After sizing, the fiber web W is guided via an air-support drying device 87 of the drying unit 260, which first dries the sizing agent to prevent it from adhering to the subsequent drying cylinder 84 in the drying unit 260. The fiber web W is further dried in the drying unit 260, in this example including single-web drying and double-web drying. In single-web drying, the fiber web W is supported and operated by a drying web 80 via the drying cylinder 84 and a reversing roller 83. The drying web 80 operates as a supported closed loop and is provided with rollers 82 for guiding, tensioning, and / or driving the drying web 80. Drying unit 260 also includes a double-net dryer, wherein the fiber web W is dried by drying cylinders 94U and 94L arranged in two rows.Each row has its own drying web 90U, 90L and rollers 92U, 92L for guiding, tensioning and / or driving the corresponding drying web 90U, 90L. Between rows, the fiber web W has free traction. Drying unit 260.

[0085] After the sizing section 250 with drying unit 260, the fiber web is guided to the calendering section 270, which in this example includes a calendering roll gap formed between calendering rolls 105 and 106. A coating section with a coater and drying equipment can be provided after the pre-calender, and a final calender (not shown) can also be provided after the coating section. The fiber web W is then guided to the paper winding unit 280, in which the fiber web W is wound onto the master roll 115 by the winding drum 116.

[0086] from Figures 1 to 4 As can be understood from the example, in the production of the fiber web W, the sizing of the fiber web is carried out in at least two main sizing stages, including internal sizing of the fiber web W in the forming section 210 and surface sizing of the fiber web W in the advantageously sizing section 250.

[0087] Internal sizing of the fiber web W is carried out in the forming section 210 of the fiber web production line 200 by applying an sizing agent (advantageously in foam form) to the surface of the fiber web W and / or between at least two layers W10, W20, W30 of the multi-lay fiber web W. The sizing agent is absorbed into the interior of the fiber web W due to the suction of the dewatering devices 11, 15, 17, 21, 25, 21, 35, 56 used in the forming section 210 and subsequent pressing dewatering between the press rolls 45, 55, which is further affected by the pressure of the press roll gaps 45, 55 formed in the pressing section 230 of the fiber web production line 200. The application devices C10, C20, C30, C50 for internal sizing are advantageously trough-type or sliding curtain-type application devices. The trough-type curtain-type application device is advantageous because the residence time from the nozzle to the fiber web is minimized.

[0088] The surface sizing of the fiber web W is performed after the internal sizing of the fiber web W, advantageously in a subsequent production section of the fiber web production line, i.e., in a section after the forming section of the fiber web production line, most advantageously in the sizing section 250 of the fiber web production line 200. The sizing agent is applied directly or indirectly in the sizing machine using curtain technology, spraying technology, film transfer technology, or pool technology. Preferably, the sizing agent is applied using curtain technology via a curtain application device C75. Advantageously, a high-solids-content sizing agent is used to sizing the fiber web W, preferably with a solids content of 10%-60%, more preferably with a solids content of 20%-40%. More preferably, the fiber web W is sizing using a high-solids-content sizing agent via curtain technology by the curtain application device C75. Advantageously, the sizing agent is starch. Surface sizing in this sizing machine is advantageously performed using a hard-gap sizing machine, which includes a hard-gap sizing gap formed between two hard sizing rollers 75. The surface sizing can be performed using foam application technology, applying the sizing agent in liquid or foam form. Advantageously, the fiber web production line 200 includes a final calendering stage in a calendering section 270 following the sizing section 250. Advantageously, the fiber web production line 200 includes a pre-calender after the sizing section 250, a drying unit 260, a coating section with a coating machine and drying equipment following the pre-calender, and a final calendering stage thereafter.

[0089] In the foregoing description, although some functions have been described with reference to certain features, these functions may be performed by other features, whether or not they are described. Although features have been described with reference to certain embodiments or examples, these features may exist in other embodiments or examples, whether or not they are described. The invention has been described above with reference to some advantageous examples, but the invention is not limited to these examples. Many modifications and variations are possible within the scope of the invention as defined in the following claims.

Claims

1. A production line for producing fiber webs (W), the production line (200) comprising a forming section (210) including at least one headbox (M10; M20; M30) and a forming unit (220), the forming unit including at least one web (10; 20; 30) and at least one dewatering device (11, 15, 16, 17, 21, 25, 31, 35, 56), and the production line (200) comprising a sizing section (250) including a sizing machine having a sizing roll gap formed between two sizing rolls (75), characterized in that, The production line (200) includes at least one application device (C10; C20; C30; C50) located in the forming unit (220) and configured to apply sizing agent in foam form for internal sizing of the fiber web (W). The sizing machine located in the sizing section (250) includes at least one application device (C75) configured to apply sizing agent for surface sizing of the fiber web (W). The application device located in the forming unit (220) is configured to apply the sizing agent in foam form with a solid content of 0.5%-20%, and the application device (C75) located in the sizing section (250) is configured to apply the sizing agent with a solid content of 10%-60%, wherein the amount of sizing agent applied in the internal sizing stage is greater than that in the surface sizing stage.

2. The production line according to claim 1, characterized in that, The production line is used to produce multiply laid fiber webs having at least two layers (W10; W20; W30), and the forming unit (220) of the production line (200) includes at least one double-web forming component, which forms between a web (10) for a first layer of the multiply laid fiber web and a web (20; 30) for a second layer of the multiply laid fiber web, wherein the double-web components for each layer of the multiply laid fiber web are joined together and the processed layers are combined, and the forming unit includes at least one application device (C10; C20; C30) for applying an sizing agent in foam form between at least two layers (W10; W20; W30) of the multiply laid fiber web (W).

3. The production line according to claim 1, characterized in that, The application device (C10; C20; C30) located in the forming unit (220) is a curtain application device, which is configured to apply the sizing agent in foam or liquid form.

4. The production line according to claim 2, characterized in that, The application device (C10; C20; C30) located in the forming unit (220) is a curtain application device, which is configured to apply the sizing agent in foam or liquid form.

5. The production line according to any one of claims 1 to 4, characterized in that, The application device (C75) located in the sizing section (250) is a curtain application device, which is connected and positioned to the sizing roller (75) and is configured to apply the sizing agent indirectly in foam form via the surface of the sizing roller (75) to the fiber web (W) in the gap of the sizing roller.

6. The production line according to any one of claims 1 to 4, characterized in that, The application device (C75) located in the sizing section (250) is configured to apply the sizing agent with a solid content of 20%-40%.

7. The production line according to any one of claims 1 to 4, characterized in that, The glue application roller (75) of the glue application section (250) is a hard roller.

8. The production line according to claim 2, characterized in that, The production line is used to produce multi-lay fiber webs having at least three layers (W10; W20; W30), wherein at least one application device is used to apply sizing agent in foam form to the top of a filler layer, which will be bonded to the top and back layers in the double-web component.

9. The production line according to any one of claims 1 to 4, characterized in that, The forming unit (220) of the production line (200) includes a suction or negative pressure device (15; 25; 35) located on the opposite side of the fiber web and its support mesh relative to the application device (C10; C20; C30).

10. The production line according to any one of claims 1 to 4, characterized in that, The fiber web production line includes air guides (14; 24; 34; 54; 74) located before the application device (C10; C20; C30; C75) for redirecting boundary airflow away from the operating direction of the fiber web (W) before applying the sizing agent in a curtain-like manner in foam or liquid form.

11. The production line according to claim 10, characterized in that, The air guides (14; 24; 34; 54; 74) include air curtains and / or reversing blades.

12. The production line according to any one of claims 1 to 4, characterized in that, The production line (200) includes a metal strip calender or heat treatment device located in or after the sizing section (250).

13. A method for producing a fiber web having at least one layer in a production line (200), the production line comprising a forming section (210) including at least one headbox (M10, M20, M30) and a forming unit (220), wherein in the forming unit (220), the fiber web (W) is supported by at least one net (10; 20; 30) and water is removed from the fiber web (W) by at least one dewatering device (11, 15, 16, 17, 21, 25, 31, 35, 56), and wherein in the method, the production line (200) includes a sizing section (250) in which the fiber web is sizing, the sizing section including a sizing machine having a sizing roll gap formed between two sizing rolls (75), characterized in that, In the method, the interior of the fiber web (W) is sizing by at least one application device (C10; C20; C30; C50), the at least one application device being located in the forming unit (220) and configured to apply the sizing agent in foam form for interior sizing of the fiber web (W), and in the method, the fiber web is surface sizing by at least one application device (C75) in the sizing machine, the at least one application device being configured to apply the sizing agent for surface sizing of the fiber web (W), the application device located in the forming unit (220) being configured to apply the sizing agent in foam form with a solid content of 0.5%-20%, and the application device (C75) located in the sizing section (250) being configured to apply the sizing agent with a solid content of 10%-60%, wherein the amount of sizing agent applied in the interior sizing stage is greater than that in the surface sizing stage.

14. The method according to claim 13, characterized in that, In the method, the sizing agent is applied in foam form to a multi-layered fiber web having at least two layers (W10; W20; W30) to perform the internal sizing of the fiber web (W) by applying the sizing agent between the layers (W10; W20; W30).

15. The method according to claim 13 or 14, characterized in that, In the method, the adhesive used for internal sizing is applied in the form of a curtain foam.

16. The method according to claim 13 or 14, characterized in that, In the method, the solids content of the sizing agent used for surface sizing is higher than the solids content of the sizing agent used for internal sizing.

17. The method according to claim 13 or 14, characterized in that, The sizing agent used for the surface sizing is applied at a solids content of 20%-40%.

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