Corrugated cardboard and methods for manufacturing corrugated cardboard

Abstract

The present invention relates to corrugated cardboard (1), comprising pre-treated first and second flat linerboards (2, 3) and a corrugated flute (4) between them, which is composed of an internal flute material (6) and A-sides and B-sides (5a, 5b). The corrugated flute (4) has peaks (7a, 7b) and valleys (8a, 8b) that are arranged on opposite sides. The linerboards (2, 3) have inner surfaces (9a, 9b) and opposite outer surfaces (10a, 10b). The inner surfaces (9a, 9b) are welded to the peaks (7a, 7b) with an adhesive which is a pre-treated polymer coating (11a, 11b) on the inner surfaces (9a, 9b). The peaks (7a, 7b) include bent zones (12a, 12b) having surface openings (13), and the polymer coating (11a, 11b) adheres not only to the internal flute material (6) exposed at the surface openings (13) but also around it.

Description

Technical Field

[0001] The present invention relates to cardboard and a method for manufacturing cardboard.

Background Art

[0002] Cardboard is a kind of packaging material, mainly comprising corrugated flutes and one or two flat liner boards. The corrugated flutes and the flat liner boards are attached to each other by an adhesive applied between the corrugated flutes and the liner boards. Cardboard is generally used for manufacturing boxes of various sizes, shapes, and styles.

[0003] Cardboard is manufactured by a wet process, and during the process, the flutes and liner boards that are made into a waveform arrive at the manufacturing site for cardboard production. What is common is that the materials for cardboard enter large and complex machines. In a general manufacturing process, steam and a starch dispersion liquid manufactured on-site are used. This means that a lot of moisture is added to form the corrugated flutes and the liner boards and bond them to each other, and later, a large dryer is used to dry the increased moisture generated in the assembly process. In such a known manufacturing process, it is generally necessary for the manufactured cardboard to go through a curing process. The curing process is a time-consuming process and may take several hours until the cardboard can proceed to the next processes such as printing, creasing, and cutting. A known drawback in the current manufacturing process is not only that the manufacturing process takes a long time, but also that the manufacturing process including subsequent curing requires a lot of space during the manufacturing of cardboard. Furthermore, these drawbacks are costly because of the high energy consumption in the manufacturing process.

[0004] Another bonding method involves bonding corrugated flutes to flat linerboard with polymer. The problem with current bonding methods is that it is difficult to minimize the amount of adhesive used while simultaneously avoiding negative impacts on strength. Therefore, when using polymer for bonding, the minimization step is generally avoided because it weakens the structure within the corrugated cardboard. If high levels of polymer are used to maintain the strength of the structure, a further problem arising with existing technologies is that the high levels of polymer in the waste require a lot of service and maintenance on the recycling process and machinery. [Overview of the project]

[0005] The objective of this invention is to provide corrugated cardboard that overcomes the above-mentioned problems. In relation to the above objectives, a further objective of the present invention is to provide a method for manufacturing corrugated cardboard in which both the method and the corrugated cardboard are improved compared to those of the prior art. The object of the present invention is achieved by relating to corrugated cardboard comprising a first flat linerboard, a second flat linerboard, and a corrugated flute disposed between the first and second flat linerboards. The corrugated flute comprises an A-side, a B-side, and an internal flute material disposed between the A-side and B-side. The corrugated flute includes A-peaks and A-troughs disposed on opposite sides of each other. Furthermore, the corrugated flute includes B-peaks and B-troughs disposed on opposite sides of each other. The first flat linerboard comprises a first inner surface and a first outer surface disposed on the opposite side. The second flat linerboard comprises a second inner surface and a second outer surface disposed on the opposite side. The first inner surface is connected to the A-peaks with a first reactivating adhesive. The second inner surface is connected to the B-peaks with a second reactivating adhesive. The adhesives described herein may be starch-free. Adhesives containing starch that contains water or moisture are not suitable for the present invention, and such starches are not used in relation to the embodiments presented herein. A polymer-containing starch adhesive, referred to herein as a polymer coating, is the material used to connect the flat liner board to the corrugated flute in the presented embodiments. Furthermore, the first inner surface is pre-treated with a first reactivating adhesive, which is the first polymer coating, and the second inner surface is pre-treated with a second reactivating adhesive, which is the second polymer coating. The A-peak includes a first A-bend zone, and the B-peak includes a first B-bend zone. The A-bend zone and the B-bend zone contain fiber dislocations in the internal flute material. These fiber dislocations may be surface openings. Surface openings may be surface cracks, surface slits, or surface scratches. At the connection between the A-peak and B-peak and the first and second inner surfaces, the polymer coating is bonded to the surface containing the openings and to the internal flute material of the surface openings. Corrugated flutes contain more fiber dislocations in the flute material in the regions that become bend zones compared to the portions of the corrugated flute positioned between bend zones. The effect of the present invention is that the surface openings increase the contact area between the peaks and the inner surface, reducing and optimizing the polymer coating, and improving strength compared to the conventional technology. Corrugated flutes are produced from a substrate that is processed into a corrugated or wave-like shape.What they have in common is that the base material is fed into a machine used for corrugated cardboard manufacturing, and corrugated flutes with A-shaped and B-shaped peaks are produced in the same machine.

[0006] According to one embodiment, the polymer coating adhesive is reactivated by heat. As a result, the corrugated cardboard manufacturing process is moisture-free, and no moisture or water is added.

[0007] No moisture is added to the pre-treated linerboard before or during the corrugated cardboard manufacturing process. The moisture level of the pre-treated linerboard and corrugated flutes should be 15% or less, preferably 10% or less. If the moisture level exceeds 15%, it negatively affects the adhesion between the linerboard and the corrugated flute material. This is because, in the process, thermal energy is used to remove moisture from the material rather than to bond the polymer coating so that the pre-treated linerboard and corrugated flute material adhere to each other. If the moisture level exceeds 15%, a further problem arises: the surface of the linerboard, i.e., the outer surface, becomes uneven and wavy. Such a surface becomes wavy because the moisture affects the linerboard material. Such an uneven surface makes printing and writing difficult. To smooth an uneven surface, an additional process is required after the manufacturing process to smooth the corrugated cardboard surface, which is time-consuming and negatively impacts costs.

[0008] According to one embodiment, the internal flute material contains fibers, and at the surface opening, the fiber ends extend outward from the inner surface of the surface opening. As a result, the surface area of ​​the fiber ends at the surface opening and the surface opening itself combine to increase the total surface area.

[0009] Surface openings are formed in the ridges of the corrugated flute material during the manufacturing process when the flute material is formed into corrugated flute material by a corrugated wheel. Since the moisture level of the flute material is low, 15% or less, preferably 10% or less, the surface openings are formed as cracks by the corrugated wheel when the ridges are formed. If the flute material has a moisture level of more than 15%, there is a risk that the material properties of the flute material will become too flexible and soft, and when the ridges are formed by the corrugated wheel, there will be no cracks or surface openings at all, or only very few, or the ridges will be too small. If the cracks or surface openings are too small, the internal fibers will not be exposed.

[0010] According to one embodiment, the fiber ends extending away from the inner surface combine with the polymer coating to form a fiber-reinforced connection between the peaks and the inner surface. As a result, a strong and durable bond is created between the peaks and the inner surface.

[0011] According to one embodiment, the thickness of the polymer coating on each inner surface is 1 to 10 μm. This allows for optimization of the layer of polymer coating to be applied. To facilitate the recycling of corrugated cardboard, it is necessary to make the polymer coating as thin as possible. In the recycling process, the corrugated cardboard is mixed with a liquid to form a slurry. In the slurry stage, the polymer coating is released and separated from the used corrugated cardboard. After a short time, the equipment used in the recycling process needs to be cleaned to remove the separated polymer coating. Therefore, the less polymer coating there is on the corrugated cardboard, the more cardboard can be recycled before the recycling process is stopped for maintenance, cleaning, and removal of the separated polymer coating.

[0012] According to one embodiment, the polymer coating on each inner surface of the liner has a surface weight of 0.5 to 10 g / m². 2This is (GSM). This is because the polymer coating is involved in capillary surface tension and diffusion processes, resulting in the effect that the liquid polymer coating is drawn into or absorbed by two adjacent surfaces, the inner surface and the ridge, which face each other in the connecting phase.

[0013] According to one embodiment, the inner surface includes a fibrous structure which is bonded to a polymer coating in a previous step. A flat liner board having an inner surface is pre-treated with a polymer coating so that each inner surface becomes adhesive.

[0014] According to one embodiment, the polymer coating applied to the inner surface is capable of diffusion through the polymer coating. As a result, by applying a coating that allows diffusion, the amount of polymer coating used for the surface coating can be reduced.

[0015] According to one embodiment, the inner surface is pre-treated with a polymer coating, while the outer surface is not coated. This effect facilitates printing and other surface treatments. In this context, "not coated" means that there is no polymer coating actively applied to the surface. Furthermore, the term "coating" refers to a polymer coating intended to change from a solid phase to a liquid phase or a sticky reactivating phase, weld to the corrugated flute, and then return to a solid phase due to heat loss.

[0016] The polymer coating may contain polyvinyl acetate components, namely PVA or PVA-C. The advantage of PVA or PVA-C is that these components can be reactivated when exposed to heat and pressure (i.e., welding). Pre-treated linerboard is pre-treated with a polymer coating consisting of PVA or PVA-C before being sent to the corrugated cardboard manufacturing process. During the corrugated cardboard manufacturing process, the heat generated during the process reactivates the PVA or PVA-C polymer coating, causing the coating to adhere and weld to the corrugated flutes, thus bonding the linerboard to the corrugated flute material.

[0017] In one embodiment, first and second bellows are formed on both sides of the peak at the connection between the peak and the inner surface. In a further embodiment, the first bellows positioned on both sides of peak A are larger than the second bellows positioned on both sides of peak B. This effect makes the surface, for example, intended for use in graphic illustrations with printed text or images, flatter and smoother, and therefore more suitable for text and images.

[0018] According to one embodiment, on the pre-treated inner surface, the first polymer coating includes a first coating surface, which has a smoother surface than the second coating surface placed on the second polymer coating. The difference in surface smoothness is due to how heat is applied to the first and second liner boards during the corrugated cardboard manufacturing process. The first flat liner board is affected by first heat applied to its outer surface and which may have a direction passing through the first flat liner board. The second flat liner board is affected by second heat having a direction toward the inner surface of the second flat liner board. Heating allows the corrugated flutes to be directly positioned on their respective inner surfaces. Furthermore, compared to existing technologies, this method reduces waste in the manufacturing process and eliminates the need for curing after the assembly process.

[0019] According to one embodiment, the A-ridge has a second A-bend zone, with a first extension positioned between the first A-bend zone and the second A-bend zone, and the B-ridge has a second B-bend zone, with a second extension positioned between the first B-bend zone and the second B-bend zone. The effect of the added second A-bend zone and B-bend zone, and the extension described above, is that the surface area between the corrugated flute and the inner surface can be adjusted and controlled as needed. For example, in corrugated cardboard used in environments where high rigidity is required, the rigidity of the corrugated cardboard is improved by adding a second bend zone and connecting the extension to the inner surface.

[0020] According to one embodiment, the first extension between the first A-bend zone and the second A-bend zone includes a third A-bend zone, and the second extension between the first B-bend zone and the second B-bend zone includes a third B-bend zone. According to a further embodiment, the first and second extensions are V-shaped. In a further embodiment, the V-shaped extension is adapted to move elastically toward or away from the inner surface, with at least one of the first or second bend zones not adhered to the inner surface. As an effect of this, the V-shape allows for elastic movement between the first and second flat linerboards. The effect of the corrugated cardboard's elasticity, or flexibility, is that it provides the possibility of dynamic forces being applied to the surface of the corrugated cardboard. With elasticity, the risk of permanent indentations forming on the surface of the corrugated cardboard is reduced.

[0021] The above objectives are further achieved by the present invention by a method for manufacturing corrugated cardboard as described above, the corrugated cardboard comprising a first flat linerboard pretreated with a first polymer coating, a second flat linerboard pretreated with a second polymer coating, and corrugated flutes positioned between the first and second linerboards. This method is carried out in a dry process that does not increase the moisture content of the structure and includes the following steps: - A step of introducing a pre-treated first flat liner board into the method; - A step of feeding flat flute material into the corrugation process; - A step of feeding a corrugated flute having a peak A on one side and a peak B on the other side into the method; - In the first joining step of the method, a pre-treated first flat liner board and a corrugated flute are joined to each other under the influence of a first pressure; - A step of applying first heat to the corrugated flute to liquefy the first polymer coating on the pre-treated first flat liner board; - A step of attaching the A-peaks from the corrugated flutes to the reactivating polymer coating placed on the first inner surface of the first flat liner board; - A step of curing the liquefied first polymer coating; - A step of conveying the corrugated flute attached to the first flat liner board from the first joining step to the second joining step; - A step of introducing the pre-treated second flat liner board into the method; - A step of applying a second heat to the pre-treated second flat liner board to liquefy the second polymer coating on the pre-treated second flat liner board; - A step of joining the pre-treated second flat liner board and the corrugated flute to each other under the influence of a second pressure in the second joining step of the method; - A step of attaching the B ridges from the corrugated flute to the liquefied second polymer coating disposed on the second inner surface of the second flat liner board; - A step of conveying the corrugated flute attached between the first and second flat liner boards from the second joining step to a cooling step for transferring heat to a heating element from the corrugated flute and the first and second flat liner boards.

[0022] The effect of this method is that throughout the process and method of manufacturing cardboard, the cardboard has no warping, and since no moisture is added in the manufacturing process, cardboard can be manufactured without treating the cardboard in a drying process for removing or evaporating liquid. According to this document, the manufacturing of cardboard means that the method and the cardboard have low sensitivity to moisture in the structure. Furthermore, since a liner board pre-treated with a polymer coating is used and no moisture is added in the manufacturing process, there is also an effect that the curing process is unnecessary.

[0023] According to one embodiment, the first heat and the second heat have the same heating direction with respect to the corrugated flute. As an effect of this, the outer surface of the flat liner board has a smoother property compared to the inner surface, and there is no need to perform additional treatment on the outer surface. This can be advantageous when, for example, subsequent processes such as characters, images printed on the outer surface, or other processes depending on the surface roughness or friction are included.

[0024] The first and / or second heat applied can be a welding process in which the temperature of the polymer coating is heated to 80 to 180 °C. In this temperature range, the polymer coating liquefies. When liquefied, the liner board and the corrugated flute material can adhere and weld together.

[0025] According to one embodiment, when laminating each flat liner board and the corrugated flute, the second flat liner board is laminated to the corrugated flute at a pressure lower than the pressure applied when laminating the first flat liner board to the corrugated flute. One effect of this is that a smoother or flatter outer surface is obtained compared to when each flat liner board is laminated to the corrugated flute at the same pressure or when the second flat liner board is laminated to the corrugated flute at a higher pressure. The size of the bellows formed on both sides of each peak in the lamination process determines how smooth or flat the outer surface will be in the connection between the liner board and the corrugated flute. A further aspect that affects the surface characteristics for obtaining a smooth or flat surface is that the lamination process is carried out in a moisture-free process.

[0026] According to one embodiment, the first heat is applied to the valleys and transmitted through the corrugated flutes. As an effect of this, heat can be applied to the tool that directly interacts with the corrugated flutes, enabling the process to be made more compact.

[0027] According to one embodiment, during the lamination process, the first heat and the second heat may have opposite heating directions.

[0028] According to one embodiment, the conveyance time between the first joining step and the second joining step is longer than the conveyance time between the second joining step and the cooling step. This eliminates the need for a curing process after the cooling step. After the cooling step, the cardboard is cut or shaped to the desired length and size.

[0029] According to one embodiment, the web length between the first joining step and the second joining step for manufacturing corrugated cardboard is longer than the cooling web length. The web length is the length of the corrugated flute and at least one flat liner board that moves between the first joining step and the second joining step. The cooling web length is the length of the corrugated cardboard that enters a cooling step after the second joining step in which the polymer coating that joins the corrugated cardboard elements hardens and solidifies. This method and process for manufacturing corrugated cardboard is moisture-free. In this context, moisture-free means that no moisture or water is actively added to the corrugated cardboard manufacturing process. Even if there is moisture or high humidity in the air, for example, during the manufacturing process, it will evaporate due to the heat generated during the manufacturing process.

[0030] According to one embodiment, heat from the first and second flat liner boards and corrugated flutes is transferred to the heat receiving element via contact between at least one of the flat liner boards and the heat receiving element. This contact can be friction. As a result, corrugated cardboard can be manufactured without a subsequent time-consuming curing process. Conventional corrugated cardboard manufacturing methods typically require several hours, for example, 12 hours, for the subsequent curing process.

[0031] According to one embodiment, heat transfer from the first and second flat liner boards having corrugated flutes to the heat receiving element causes the polymer coating to harden, resulting in a dry connection between the intermediate corrugated flutes and the first and second flat liner boards. This causes the polymer coating to undergo a phase change from a liquid, viscous state to a solid state, resulting in a strong connection between the different layers of the first and second flat liner boards together with the corrugated flutes. [Brief explanation of the drawing]

[0032] The present invention will be described in more detail below with reference to the attached drawings. [Figure 1] Figure 1 shows a corrugated cardboard structure comprising first and second flat liner boards and corrugated flutes positioned between the first and second flat liner boards. [Figure 2] Figure 2 shows a corrugated flute that constitutes a bent zone with an opening. [Figure 3] Figure 3 is a partial cross-sectional view of a corrugated flute. [Figure 4] Figure 4 is a partial cross-sectional view of a corrugated cardboard box. [Figure 5] Figure 5 is a partial cross-sectional view of the corrugated cardboard showing the first bellows. [Figure 6] Figure 6 is a partial cross-sectional view of the corrugated cardboard showing the second bellows. [Figure 7] Figure 7 is a partial cross-sectional view of an embodiment of a corrugated flute. [Figure 8] Figure 8 is a partial cross-sectional view of an embodiment of an elastic corrugated flute. [Figure 9] Figure 9 is a flowchart showing the method for manufacturing corrugated cardboard. [Modes for carrying out the invention]

[0033] Figure 1 shows corrugated cardboard 1. Corrugated cardboard 1 comprises a first flat liner board 2, a second flat liner board 3, and a corrugated flute 4 positioned between the first flat liner board 2 and the second flat liner board 3. The corrugated flute 4 has an A-side 5a and a B-side 5b. Between the A-side and the B-sides 5a and 5b is an internal flute material 6. In corrugated cardboard 1, the A-side 5a faces the first flat liner board 2, and the B-side 5b faces the second flat liner board 3. The corrugated flute 4 has A-peaks 7a and B-peaks 7b. The A-peaks 7a is located on the A-side 5a of the corrugated flute 4, and the B-peaks 7b is located on the B-side 5b. On the opposite side of the A-peaks 7a, the B-side 5b of the corrugated flute 4 has A-troughs 8a. On the opposite side of the B peak 7b, the B valley 8b is located on the A side 5a of the wave flute 4.

[0034] Figure 1 shows a first flat liner board 2 having a first inner surface 9a and a first outer surface 10a. The second flat liner board 3 has a second inner surface 9b and a second outer surface 10b. The first flat liner board 2 is pre-treated with a first coating applied to the first inner surface 9a of the first flat liner board 2. The second flat liner board 3 is pre-treated with a second coating applied to the second inner surface 9b of the second flat liner board 3. Pre-treatment refers to coating the flat liner boards 2 and 3 before entering the manufacturing process of corrugated cardboard 1. The first coating is a first polymer coating 11a, and the second coating is a second polymer coating 11b.

[0035] The second outer surface 10b has smoother properties than the first outer surface 10a (not shown). The reason for the difference in smoothness between the first and second outer surfaces 10a and 10b is the direction of heat required to reactivate the polymer coatings 11a and 11b. Due to the difference in smoothness between the first and second outer surfaces 10a and 10b, the second outer surface 10b can be suitably used for printing text, applying images, or other subsequent processes where a smoother surface is advantageous. Due to its difference in smoothness, the first outer surface 10a can be oriented, for example, toward the inside of a corrugated cardboard box.

[0036] Figure 2 shows a corrugated flute 4. The corrugated flute 4 has a surface A 5a and a surface B 5b located on the opposite side. The corrugated flute 4 has an internal flute material 6. Surface A 5a has a peak 7a. Surface B 5b, opposite to the peak 7a, has a valley 8a. Surface B 5b has a peak 7b. Surface A 5a, opposite to the peak 7b, has a valley 8b.

[0037] Figure 2 shows the A-peak 7a constituting the first A-bend zone 12a and the B-peak 7b constituting the first B-bend zone 12b. Surface openings 13 are located in the A-bend zone 12a and the B-bend zone 12b. These surface openings 13 are located in the bend zones 12a and 12b to increase the surface area of ​​the corrugated flutes 4 used for joining to the first and second flat liner boards 2 and 3.

[0038] According to one embodiment, the opening 13 can be provided in the corrugated flute material 4 before the material is processed to obtain its corrugated shape. According to a further embodiment, the opening 13 may be provided in the corrugated flute 4 when creating the corrugated shape. According to one embodiment, the surface opening 13 consists of a hole located on the surface of the bending zones 12a and 12b. According to one embodiment, the surface opening 13 may be formed when the bending zones 12a and 12b are formed. According to a further embodiment, the surface opening 13 may be a surface crack in the surface region of the bending zones 12a and 12b. According to a further embodiment, the surface opening 13 may be a notch on the surface of the bending zones 12a and 12b. Notches or cracks may be pre-formed in the corrugated flute, and the notches or cracks in the bending zone may open during the process of forming the peaks 7a and 7b in the corrugated flute 4, thereby exposing the inner surface 6. The surface opening 13 is an opening in the corrugated flute 4 to the internal flute material 6. The surface opening 13 has an inner surface 16 (see Figure 3) located in the internal flute material 6. The effect of the surface opening 13 and its inner surface 16 is that the surface area of ​​the ridges 7a and 7b when joined to the inner surfaces 9a and 9b of the flat liner boards 2 and 3 increases compared to when the surface opening 13 is not formed on their surface. The increase in surface area has the further effect of improving the connection strength between the corrugated flute 4 and the respective flat liner boards 2 and 3.

[0039] Figure 3 shows a cross-sectional view of a portion of the corrugated flute 4. In the cross-sectional view of Figure 3, the corrugated flute 4 is provided with surface A 5a. The internal flute material 6 is arranged on surface A 5a and surface B 5b. In Figure 3, surface A 5a is composed of A peaks 7a. The A peaks 7a have a first A bending zone 12a. Surface openings 13 are located on the surface of the A bending zone 12a (part of surface A 5a). These surface openings 13 extend across the entire A bending zone 12a. The A bending zone 12a is positioned to be joined to a first inner surface 9a, so that the surface openings 13 face toward and apply to the first inner surface 9a to which they are joined. The surface openings 13 have an inner surface 16. The inner surface 16 is located inside the openings 13 of the internal flute material 6. The internal flute material 6 contains fibers 14. Each fiber 14 has its own fiber end 15. Within the opening 13, the fibers 14 extend with one fiber end 15 protruding from the inner surface 16 of the opening 13. The fibers 14 have a mixed orientation within the internal flute material 6. The fiber ends 15 extending outward or outward from the inner surface 16 of each opening 13 may have a mixed orientation and / or divergent orientation, depending on their original position and orientation within the internal flute material 6. This is because, when the material for the corrugated flutes 4 is manufactured, the fibers 14 are mixed into the slurry and become the corrugated flutes 4 during processing.

[0040] Figure 4 shows a cross-sectional view of a portion of corrugated cardboard 1. In the cross-sectional view of Figure 4, the first flat liner board 2 is joined together with a corrugated flute 4 having an internal flute material 6 containing fibers 14. The first flat liner board 2 is pre-treated with a first polymer coating 11a. The corrugated flute 4 has a first A-bend zone 12a having an opening 13. Fiber ends 15 are exposed within the opening 13 and extend outward from the inner surface 16 of the opening 13. In the joining process between the first flat liner board 2 and the corrugated flute 4, the first polymer coating 11a is heated to the liquid phase, so that in the joining process the polymer coating 11a adheres to the first A-bend zone 12a including the surface opening 13. In the joining process, the first polymer coating 11a enters the opening 13 and bonds with the fiber ends 15 of the fibers 14 within the surface opening 13, forming a fiber-reinforced connection portion 17. Because the polymer coatings 11a and 11b are heated to a liquid state, they are drawn into or sucked into the surface openings 13 facing the inner surfaces 9a and 9b by capillary force, diffusion process, and forces fixing the two surfaces together. As a result of the fiber-reinforced connection 17, the strength, rigidity, and stability of the corrugated cardboard 1 structure are improved. Furthermore, because the amount of polymer coating is optimized by capillary force, process waste due to overuse of coating is eliminated, and the recycling process is not negatively affected.

[0041] Figure 5 shows a cross-sectional view of a part of the corrugated cardboard 1. In the joining or connection process between the first flat liner board 2 and the A-ridge portion 7a, first heat is applied to the A-groove portion 8a. The first heat is transferred to the surface of the A-ridge portion 7a through the corrugated flute 4. On the first flat liner board 2, the first heat liquefies the first polymer coating 11a that constitutes the first coating surface 19a. Simultaneously with the liquefaction of the polymer coating 11a due to the first heat, first pressure is applied, pressing the first flat liner board 2 and the flute corrugated cardboard 4 against each other. As the first flat liner board 2 and the flute corrugated cardboard 4 are pressed toward each other, the first heat is transferred from the A-ridge portion 7a to the first polymer coating 11a, so that the first coating surface 19a forms first bellows 18a on both sides of the A-ridge portion 7a at the connection point with the first flat liner board 2. In this context, when we say that the polymer coating has liquefied, been liquefied, or is liquefied, it means that the polymer coating was initially dry or substantially dry and has been reactivated, or has changed state or phase to a viscous or wet phase. During this reactivation stage, the polymer coating adheres to or connects to the corrugated flute 4.

[0042] Figure 6 shows a cross-sectional view of a portion of the corrugated cardboard 1. Figure 5 shows the joining of the first flat linerboard 2 to the corrugated flute 4. Figure 6 shows how the second flat linerboard 3 is connected to the B-peak 7b. In the joining process between the second flat linerboard 3 and the B-peak 7b, a second heat is applied to the second outer surface 10b. The second heat passes through the second flat linerboard 3 to the second polymer coating 11b, and further to the second coating surface 19b of the second polymer coating 11b. The second heat liquefies the second polymer coating 11b toward the second coating surface 19b, so that the liquefaction gradually decreases. In this second joining and heating process, a second pressure is applied to the first flat linerboard 2 and the second flat linerboard 3, with the flute corrugated cardboard 4 placed between them. In the second joining process, the B-shaped peak 7b is pressed toward the liquefied second polymer coating 11b, and the second coating surface 19b forms second bellows 18b on both sides of the B-shaped peak at the connection point with the second flat liner board 3.

[0043] Figures 5 and 6 show that the first bellows 18a is larger than the second bellows 18b. In this way, the outer surfaces 10a and 10b are smoother than the inner surfaces 9a and 9b, eliminating the need for additional processing of the outer surfaces 10a and 10b during printing.

[0044] Figure 7 shows a part of an embodiment of the corrugated flute 4 in which the A-peak 7a constitutes the second A-bend zone 20a. As shown in Figure 7, the corrugated flute 4 in this embodiment is configured to connect to the first and second flat liner boards 2 and 3, as described above in relation to Figure 1. The A-peak 7a has a first A-bend zone 12a and a second A-bend zone 20a. A first extension 21a is positioned between the two A-bend zones 12a and 20a. Furthermore, the B-peak 7b has a second B-bend zone 20b. The B-peak 7b has a first B-bend zone 12b and a second B-bend zone 20b. A second extension 21b is positioned between the two B-bend zones 12b and 20b. The first and second extensions 21a and 21b are parallel to each other. The bending zones 12a, 20a, 12b, and 20b are configured to have surface openings 13 (not shown in Figure 7), as described above in relation to Figures 2-4, so that each bending zone 12a, 20a, 12b, and 20b has a fiber-reinforced connection portion 17 when connected to the first and second flat liner boards 2 and 3.

[0045] Figure 8 shows a part of a further embodiment of the corrugated flute 4 in which a third A-bend zone 22a is located in the A-peak 7a. The third A-bend zone 22a is located in the first extension 21a between the first and second A-bend zones 12a, 20a. Furthermore, a third B-bend zone 22b is located in the B-peak 7b. The third B-bend zone 22b is located in the second extension 21b between the first and second B-bend zones 12b, 20b. In the embodiment of Figure 8, the first and second extensions 21a, 21b are V-shaped. The third A-bend zone 22a and the third B-bend zone 22b have surface openings 13 (not shown in Figure 8), as described above in relation to Figures 2-4. As a result, each of the third bend zones 22a, 22b has a fiber-reinforced connection 17 when connected to the first and second flat liner boards 2, 3. As a further effect, in the embodiment shown in Figure 8, the first and second A bending zones 12a, 20a, and the first and second B bending zones 12b, 20b can be configured so as not to be connected to the first and second flat liner boards 2, 3 (not shown in Figure 8). As a result, the V-shaped structure of the first and second extensions 21a, 21b allows the corrugated flutes 4 to provide elasticity to the corrugated cardboard 1.

[0046] Although not shown in the figures, various combinations of the A-peak and B-peak 7a and 7b described above are possible in the corrugated flute 4. One embodiment of the corrugated flute 4 may be a corrugated flute 4 comprising the A-peak 7a defined in Figure 1 and the B-peak 7b defined in Figure 7. A further embodiment of the corrugated flute 4 may be a corrugated flute 4 comprising the A-peak 7a defined in Figure 1 and the B-peak 7b defined in Figure 8. Another embodiment of the corrugated flute 4 may be a corrugated flute 4 comprising the A-peak 7a defined in Figure 7 and the B-peak 7b defined in Figure 8.

[0047] Throughout this text, the A and B peaks, A and B valleys, A and B bending zones, surface openings, polymer coatings, fibers, fiber ends, inner surfaces, bellows, and defined fiber reinforcement connections are not only relevant to and connect to the figures mentioned in this text, but are also applicable to figures not mentioned. This is because these features are part of the embodiments of the invention as described in this text.

[0048] Figure 9 is a flowchart of the method and process for manufacturing corrugated cardboard 1. In the flowchart, each step is represented by a Greek numeral. Corrugated cardboard 1 is manufactured at the manufacturing site according to the following method steps:

[0049] I: The first flat liner board 2 is located in the manufacturing area. The first flat liner board 2 has been pre-treated with the first polymer coating 11a. The first flat liner board 2 is guided and introduced into step III of the method.

[0050] II: The corrugated flute 4 is made from the base material. The base material is located at the manufacturing site. The base material is guided into the process and processed by a molding element into a corrugated flute 4 having A-peaks 7a on one side and B-peaks on the other side. This process is continuous, and the base material is formed into corrugated flute 4 and guided into method step III.

[0051] III: The first flat liner board 2 and the corrugated flute 4 are joined in the presence of first heat and pressure. The first heat is supplied from a first rotating element positioned to interact with the corrugated flute 4. The first heat is transferred from the first rotating element to the first surface of the corrugated flute 4. The first heat is further transferred from surface A 5a through the flute 4 to surface B 5b positioned on the opposite side. In this method step III, surface B 5b is positioned toward the first inner surface 9a of the first flat liner board. The first heat that has passed through the material 6 of the corrugated flute 4 liquefies the first polymer coating 11a placed on the first flat liner board 2. Simultaneously with the liquefaction of the first polymer coating 11a, the first pressure is applied to the first outer surface 10a of the first flat liner board 2 and the corrugated flute 4. The connection between the flat liner board 2 and the corrugated flute 4 is instantaneous. After the connection, the flat liner board 2 and the corrugated flute 4 are treated as a single unit and guided into step IV of the method.

[0052] IV: The first heat is discontinued, thereby eliminating the activation heat applied to the flat liner board 2 and corrugated flute 4 in step IV. The flat liner board 2 and corrugated flute 4 are transported together, guided, and introduced into step VI.

[0053] V: The second flat liner board 3 is present in the manufacturing area. The second flat liner board 3 is pre-treated with the second polymer coating 11b. The second flat liner board 3 is guided and introduced into method step VI.

[0054] VI: The second planar linerboard 3 and the corrugated flute 4 connected to the first planar linerboard 2 are joined in the presence of second heat and second pressure. The second heat is supplied from a second heat source positioned to interact with the first planar linerboard 2. The second heat is transferred from the second heat source to the second outer surface 10b of the second planar linerboard 3. The second heat is transferred from the second outer surface 10b through the second planar linerboard 3 to the second inner surface 9b located on the opposite side. In this method step VI, the second inner surface 9a is positioned toward the second surface 5b of the corrugated flute 4. The first heat that has passed through the material of the second planar linerboard 3 liquefies the second polymer coating 11b placed on the second planar linerboard 3. Simultaneously, the second polymer coating 11b liquefies, and a first pressure is applied to the first outer surface 10a of the first flat liner board 2 and the second outer surface 10b of the second flat liner board 3, thereby pushing the corrugated flute 4 between them and connecting it to the second flat liner board 3. The first flat liner board 2, the corrugated flute 4, and the second flat liner board 3 thus connected are formed together into corrugated cardboard 1, which is then guided and introduced into method step VII.

[0055] VII: From step VI of this method, the corrugated cardboard 1 acquires and stores the heat resulting from the liquefaction of the second polymer coating 11a. In step VII of this method, the corrugated cardboard is transported and rubbed against a cooling element. During transport, the heat inside the corrugated cardboard 1 is transferred from the corrugated cardboard 1 to the cooling element by friction. After the corrugated cardboard 1 has passed through the cooling element, the corrugated cardboard 1 is ready and can be cut to the desired length and size for use.

[0056] In the above description, corrugated cardboard is primarily described in relation to corrugated cardboard comprising a first flat linerboard, a second flat linerboard, and corrugated flutes. It will be understood that the principles described above can also be applied to other types of corrugated cardboard and methods for manufacturing corrugated cardboard. [Explanation of Symbols]

[0057] 1. Cardboard 2. First flat liner board 3. Second flat liner board 4. Wave Flute 5a. Side A 5b. Side B 6. Internal flute material 7a. A. Yamabe 7b. B Yamabe 8a. A valley 8b. B Tanibe 9a. First inner surface 9b. Second inner surface 10a. First outer surface 10b. Second outer surface 11a. First polymer coating 11b. Second polymer coating 12a. First A-bend zone 12b. First B-bend zone 13. Surface opening 14. Fibers 15. Fiber ends 16. Inner self 17. Fiber-reinforced connection section 18a. First bellows 18b. Second bellows 19a. First coating surface 19b. Second coating surface 20a. Second A-bend zone 20b. Second B-bend zone 21a. First extension 21b. Second extension 22a. Third A-bend zone 22b. Third B-bend zone

Claims

1. A corrugated cardboard (1) comprising a pre-treated first flat liner board (2), a pre-treated second flat liner board (3), and corrugated flutes (4) disposed between the pre-treated first and second flat liner boards (2, 3), The corrugated flute (4) comprises a surface A (5a), a surface B (5b), and an internal flute material (6) disposed between the surfaces A and B (5a, 5b). The corrugated flute (4) comprises a peak (7a) and a valley (8a) arranged on opposite sides, and a peak (7b) and a valley (8b) arranged on opposite sides, The pre-treated first flat liner board (2) comprises a first inner surface (9a) and a first outer surface (10a) located on the opposite side. The pre-treated second flat liner board (3) comprises a second inner surface (9b) and a second outer surface (10b) located on the opposite side. The first inner surface (9a) is connected to the A-mount (7a) with the first reactivating adhesive. The second inner surface (9b) is connected to the B-ridge portion (7b) with a second reactivating adhesive. The first inner surface (9a) is pre-treated with a first reactivating adhesive, which is a first thermally reactivating polymer coating (11a) coated on the inner surface (9a), and the second inner surface (9b) is pre-treated with a second reactivating adhesive, which is a second thermally reactivating polymer coating (11b) coated on the inner surface (9b), and the polymer coatings (11a, 11b) on each of the inner surfaces (9a, 9b) have a thickness of 1 to 10 μm, and the outer surfaces (10a, 10b) are not coated. The A-peak (7a) has a first A-bend zone (12a), and the B-peak (7b) has a first B-bend zone (12b), and these zones have fiber dislocations which are surface cracks (13) on the A-face and B-face that occurred when the corrugated flute material (6) was corrugated and the A-peak (7a) and B-peak (7b) were formed, and the polymer coating (11a, 11b) has a connection between the inner surface (9a, 9b) and the periphery of the surface crack (13), and Corrugated cardboard (1), characterized in that, within the surface cracks (13) facing the internal flute material (6) of the ridges (7a, 7b), the fiber ends (15) extend outward from the inner surface (16) of the surface cracks (13) in a divergent and mixing direction, and together with the polymer coating (11a, 11b), form a fiber-reinforced connection portion (17) between the ridges (7a, 7b) and the inner surfaces (9a, 9b), and the second outer surface (10b) is smoother than the first outer surface (10a).

2. The polymer coating (11a, 11b) on each inner surface (9a, 9b) has a density of 0. to 10 g / m². ２ Corrugated cardboard (1) according to claim 1, having a surface weight of (GSM).

3. The corrugated cardboard (1) according to any one of claims 1 to 2, wherein the inner surfaces (9a, 9b) have a fibrous structure to which the polymer coating (11a, 11b) is bonded.

4. The corrugated cardboard (1) according to any one of claims 1 to 3, wherein the polymer coating (11a, 11b) is coated on the inner surface (9a, 9b), allowing diffusion through the coating (11a, 11b).

5. Corrugated cardboard (1) according to any one of claims 1 to 4, wherein at the connection between the ridge portion (7a, 7b) and the inner surface (9a, 9b), first and second bellows (18a, 18b) are formed on both sides of the ridge portion (7a, 7b).

6. The corrugated cardboard (1) according to claim 5, wherein the first bellows (18a) arranged on both sides of the A-ridge (7a) are larger than the second bellows (18b) arranged on both sides of the B-ridge (7b).

7. Corrugated cardboard (1) according to any one of claims 1 to 6, wherein on the pre-treated inner surfaces (9a, 9b), the first polymer coating (11a) includes a first coating surface (19a) which has a smoother surface than the second coating surface (19b) which is placed on the second polymer coating (11b).

8. Corrugated cardboard (1) according to claims 1 to 7, wherein the A-ridge (7a) has a second A-bend zone (20a), a first extension (21a) is positioned between the first A-bend zone (12a, 20a) and the second A-bend zone (12a, 20a), and the B-ridge (7b) has a second B-bend zone (20b), a second extension (21b) is positioned between the first B-bend zone (12b, 20b) and the second B-bend zone (12b, 20b).

9. The corrugated cardboard (1) according to claim 8, wherein the first extension (21a) between the first A bending zone (12a, 20a) and the second A bending zone (12b, 20b) has a third A bending zone (22a), and the second extension (21b) between the first B bending zone (12b, 20b) and the second B bending zone (12b, 20b) has a third B bending zone (22b).

10. The corrugated cardboard (1) according to any one of claims 8 to 9, wherein the first and second extended portions (21a, 21b) are V-shaped.

11. The corrugated cardboard (1) according to any one of claims 8 to 10, wherein the V-shaped extensions (21a, 21b) are adapted to elastically move towards or away from the inner surface (9a, 9b) at least one of the first or second bending zones (12a, 12b, 20a, 20b) with the third bending zone (22a, 22b) attached to the inner surface (9a, 9b).

12. A method for manufacturing corrugated cardboard (1) according to any one of claims 1 to 11, wherein the corrugated cardboard (1) comprises a first flat liner board (2) pretreated with a first polymer coating (11a), a second flat liner board (3) pretreated with a second polymer coating (11b), and corrugated flutes (4) disposed between the first and second liner boards (2, 3), and the method is moisture-free. The steps include: introducing the pre-treated first flat liner board (2) into the method; A step of introducing the substrate into the method, The process involves processing the base material into a corrugated flute (4) having a peak A (7a) on one side and a peak B (7b) on the other side. In the first joining step of the said method, the first flat liner board (2) and the corrugated flute (4) are joined to each other under the influence of a first pressure, The first step is to apply heat to the corrugated flute (4) to liquefy the first polymer coating (11a) on the pre-treated first flat liner board (2), The steps include attaching the A-peak portion (7a) from the corrugated flute (4) to the liquefied first polymer coating (11a) placed on the first inner surface (9a) of the first flat liner board (2), The steps include curing the liquefied first polymer coating (11a), A step of sending the corrugated flute (4) attached to the first flat liner board (2) from the first joining step to the second joining step, The steps include: introducing the pre-treated second flat liner board (3) into the method; The steps include applying a second heat to the pre-treated second flat liner board (3) to liquefy the second polymer coating (11b) on the pre-treated second flat liner board (3), In the second joining step of the said method, the steps include joining the pre-treated second flat liner board (3) and the corrugated flute (4) to each other under the influence of a second pressure, The process includes the step of attaching the B-peaks (7b) from the corrugated flute (4) to the liquefied polymer coating (11b) disposed on the second inner surface (9b) of the second flat liner board (3), The first heat and the second heat have the same heating direction with respect to the corrugated flute (4). A method characterized by including a step of sending the corrugated flutes (4) attached to the first and second flat liner boards (2, 3) from the second joining step to a cooling step for transferring heat from the corrugated flutes (4) attached to the first and second flat liner boards (2, 3) to a heat receiving element.

13. The method according to claim 12, wherein the first heat is applied to the valleys (8a, 8b) and transmitted through the corrugated flute (4).

14. The method according to claim 12, wherein the transport time between the first joining step and the second joining step is longer than the transport time between the second joining step and the cooling step.

15. The method according to claim 12, wherein the web length between the first joining step and the second joining step for manufacturing the corrugated cardboard (1) is longer than the cooling web length.

16. The method according to claim 12, wherein heat from the first and second flat liner boards (2, 3) and the corrugated flute (4) is transferred to the heat receiving element through contact between at least one of the flat liner boards (2, 3) and the heat receiving element.

17. The method according to claim 16, wherein the transfer of heat from the first and second flat liner boards (2, 3) having the corrugated flutes (4) to the heat receiving element causes the polymer coatings (11a, 11b) to harden, and a dry connection is formed between the corrugated flutes (4) and the first and second flat liner boards.

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