METHOD FOR PRODUCING A FIBERBOARD

Description

[0001] The present invention relates to a fiberboard and a method for its production.

[0002] Furthermore, the invention discloses a device for producing corresponding fiberboards.

[0003] Fibreboards made of lignocellulose-containing fibres, in particular wood fibres, as such and processes for their production are well known from the state of the art, so that a separate printed reference is not required at this point.

[0004] Medium-density fiberboard, or MDF for short, is typically a board made of wood fiber material. According to the relevant European standard, the average density of an MDF board is between 650 kg / m3 and 800 kg / m3. Boards with an average density of over 800 kg / m3 are referred to as high-density fiberboard (HDF), and those with an average density of less than 650 kg / m3 are referred to as lightweight MDF. Those with an average density of less than 550 kg / m3 are referred to as ultralight MDF.

[0005] The production of medium-density fiberboard and ultra-light MDF boards typically takes place using a so-called dry process. Then, in the so-called blow-line gluing process, glued and dry fibers are produced, which have a moisture content of less than 12% dry matter. Alternative gluing methods are known from the state of the art. Alternative gluing methods include mixer gluing and dry fiber gluing. After the fibers have been glued, a further drying process is carried out alternatively or optionally. The use of so-called multi-component fibers, such as bico fibers, is also known from the state of the art. These are fibers with different glue components that can be activated, for example, by temperature.

[0006] The dried and glued or mixed fibers are then spread into a mat using a spreader, for example. Typically, a conveyor belt is used for this purpose, onto which the spreader spreads the fibers.

[0007] In a final process step, the mat is compressed, and the binder cures through heat input. This usually takes place on continuous or discontinuous hot presses.

[0008] The panel strand produced in the manner described above can then be trimmed and cut to length as required to form individual panels.

[0009] The above-described method implementation is well known from the state of the art.

[0010] A further developed process implementation has become known from EP 1 110 687 B2. The process described here relates to the production of lightweight fiberboards with an average bulk density of 60 to 350 kg / m3, which are used as thermal insulation boards in construction. The special feature of the process described here is that a bulk density profile is formed, resulting in an edge increase in the bulk density compared to the average bulk density of the fiberboard of at least 20%. This is achieved in terms of process technology by spraying the top side of the scatter mat with water before pressing. The result is a lightweight fiberboard which, due to its large surface area, has edge regions whose density is at least 20% higher than the average bulk density. These edge regions typically have a thickness of approximately 0.2 mm to 0.5 mm.

[0011] It is also known to produce corresponding panels, particularly ultralight MDF panels, as sandwich panels. Outer layers are made from a first fiber / binder system, and intermediate areas are made from a second fiber / binder system. This allows panels to be produced that are easier to handle, process, and further fabricate.

[0012] The various types of panels known to date are used for a wide variety of purposes: mats as insulation materials, HDF panels for infill, cladding, covering, and the like. However, due to their different densities and manufacturing parameters, the known mats and panels have very different mechanical properties. There is a need for panels that are as light as possible and yet extremely stable, but this demand has not yet been satisfactorily met. Either the panels are mechanically very resistant, in which case they are usually provided with a full bulk density due to high compaction, and thus heavy, or they are correspondingly lighter and less stable. Attempts have been made to remedy this by combining materials. However, limitations due to process technology and production machinery must also be accepted.

[0013] Based on the above-described prior art, the invention is based on Task The aim is to provide a process for producing a deformed fiberboard which enables the production of an industrially reproducible deformed wood fiberboard in a continuous process.

[0014] For technical Solution The invention proposes a method having the features of patent claim 1. Further advantages and features emerge from the subclaims.

[0015] According to the invention, a process is proposed in which a wood fiber mat with defined properties is first produced, preferably in a continuous process.

[0016] Wood fiber mats are preferably made from wood chips, especially softwood chips. These have a grain size of approximately 40 x 40 x 5 mm and primarily consist of pine and spruce. The wood chips are provided without bark and typically have a water content of approximately 50%. To shorten the required storage time in outdoor weather conditions, it is advantageous if the wood chips are delivered from a local area. After approximately 4 to 5 days of outdoor storage, they are cleaned using a disc separator or dry cleaning.

[0017] The wood chips must be preprocessed before being shredded. They are preheated using steam and then cooked for a specified time at a specified pressure and temperature. This process takes between one and four minutes and occurs at temperatures between 160°C and 200°C.

[0018] Subsequently, fiberization preferably takes place via refiners. This results in fiber lengths of 2 mm to 30 mm and thicknesses of 0.2 mm to 1.5 mm, although fiber lengths of over 10 mm may be advantageous for the present invention.

[0019] The material is then dried using a burner or hot air in special drying tubes. This results in an initial moisture content of between 6% and 15%.

[0020] Subsequent gluing is achieved by blowing glue into a fiber bed. The mixture is then spread onto a forming line and mechanically leveled to a uniform height, thereby adjusting the desired basis weight.

[0021] Pre-compaction and side trimming take place in a pre-press.

[0022] The pre-press is operated with a hydraulic pressure of 150 bar to 200 bar and the throughput time of a mat is between 30 seconds and 120 seconds. The final mat temperature is between 18°C ​​and 22°C with a residual moisture content of 6% to 15%.

[0023] At a steam temperature between 100°C and 110°C and a steam pressure between 0.1 bar and 8 bar, a steam flow of approximately 60 kg / h to 500 kg / h is passed through the wood fiber mat, which then passes through a steaming device. The steam can flow into the fiber mat from above or below, or from both directions.

[0024] According to an advantageous feature of the invention, the fiber mat can then be sprayed or coated. Additionally, hardeners can be added. The spraying is primarily carried out with a release agent to prevent adhesion between the fiber material and the adjacent roller surfaces. Amounts of between 10 g / m² and 100 g / m² of fiber mat are used here. The release agent and / or hardener can also be introduced through an additional steam burst.

[0025] The wood fiber mat, with a surface weight of 1.0 kg / m² to 3.0 kg / m² and a thickness of 10 mm to 30 mm, is then passed through at least one pair of rollers at a pressure of between 150 N / m² and 250 N / m², a temperature of 100°C to 350°C, and speeds of 0.5 m / min to 120 m / min. With an initial thickness of the wood fiber mat of 10 mm to 30 mm, the resulting board has a material thickness of 0.5 mm to 2 mm, which can achieve a three-dimensional wave-like deformation of 6.5 mm to 50 mm.

[0026] At least one or more pairs of calender rolls are used, which may also include corrugated rolls or combinations thereof.

[0027] Advantageously, after the deformation, an additional heat supply can be carried out, for example by microwaves, infrared technology or the like.

[0028] The deformed plate is then cured or cooled, which can take between 2 and 5 minutes.

[0029] The result of this process is a fiberboard made of lignocellulose-containing fibers, in particular wood fibers, and binders, which has an inherently stable, periodically recurring three-dimensional deformation running in at least one direction.

[0030] The fiberboard is a plate-shaped molded body made of lignocellulose-containing fibers. It is essentially plate-shaped. While a conventional board can essentially be described as a cuboid with flat surfaces, defined by side edges and two outer surfaces, which surfaces lie in a plane defined by the side edges, three-dimensional deformation in the sense of the present invention means that the board itself is deformed in a direction perpendicular to the side edges, with surfaces that are essentially parallel to one another. In the simplest conceivable case, these can be simple structures, for example pyramids. However, three-dimensional deformation includes kinks, angles, pores, and the like.

[0031] Intrinsically stable within the meaning of the present invention means that the plate remains mechanically rigid in its deformed state after its manufacture, i.e., it is not flexible in the sense that the deformation can be removed. It may exhibit a certain degree of elasticity, but is sufficiently rigid to retain its deformed shape.

[0032] However, "running in at least one direction and periodically recurring" means that the deformation continues and repeats continuously along one of the plate's directions. For example, a plate can be produced in a wave-like pattern, it can have angles, or something similar. If a cross-section is taken along one plate direction so that the deformation can be viewed from the side, it will show a kind of wave, a sawtooth, a rectangular profile, or something similar.

[0033] The deformation can be diagonal to the side edges. It can also be essentially parallel to one of the side edges.

[0034] According to an advantageous proposal, the board is designed as an HDF board in terms of bulk density. It preferably contains long fibers, for example, 15 to 20 mm.

[0035] The formation of the fiberboard creates a board that fills a large volume in relation to its bulk density. Spatial volume in the sense of the present invention refers to the essentially cuboid-shaped space filled by the board. While bulk density or board volume itself refers to the solid region of the board, the spatial volume is formed by flat surfaces on the uppermost and lowermost projections of the deformed board being supplemented by circumferential side edges to form a cuboid that completely encloses the board. This cuboid has a volume that is significantly larger than the volume formed by the solid region of the board itself. According to an advantageous proposal of the invention, the board thickness is exceeded by the volume height by at least a factor of 3.

[0036] The panel offers a particular advantage in that it combines enhanced mechanical properties with a low density. The deformation process makes the panel inherently more mechanically stable. It is well known that bent or folded elements are particularly stable under compressive loads along the bending axis. In this case, however, the panel is also extremely stable and fracture-resistant due to its bulk density in the direction of deformation.

[0037] The advantage of this panel is that it significantly expands the range of applications for such panels. Due to its low weight relative to the volume of the room, such a panel can be used, for example, as a filling. Such applications arise, for example, in the manufacture of doors and wall elements. Due to its mechanical strength, the surface can be drilled and can hold screws.

[0038] It can hold nails.

[0039] It can be directly fitted with edge banding, i.e., strips that are glued or otherwise attached to the side edges. Due to its three-dimensional deformation, the board offers a significant mounting surface along the side edges.

[0040] The panels can also be used in sandwich structures. They can be connected to similar, three-dimensionally deformed panels by placing them on top of each other and securing them in any way. It is advantageous if the three-dimensional deformations are arranged at an angle to each other. If two identical panels are connected with a wave contour, for example, they can be placed on top of each other at right angles. This creates a multitude of contact points, a considerable volume, and a very low panel weight. The mechanical stability is immense.

[0041] According to a further advantageous proposal of the invention, flat panels can be placed on the surface of three-dimensionally formed panels according to the invention. This results in panels that are very light in relation to their volume but extremely stable, for example, if the flat cover panels are very thin HDF panels.

[0042] Rollers according to the invention can be designed on their surfaces in such a way that they deform the fiber cake accordingly. The rollers are heated, for which a wide variety of methods can be used. The rollers can be electrically heated, filled with hot oil, or combinations thereof, and they can be combined with additional external treatment sources such as UV radiation, IR radiation, and the like, gas burners, etc. It is essential that the deformation is introduced into the activated fiber cake between the rollers and maintained through immediate curing. Depending on the system technology, it may be useful to use release agents to prevent fiber cakes from sticking to processing surfaces.

[0043] According to an advantageous proposal, the production takes place in a continuous process from thinning the fiber cake by spreading the fiber mixture to curing the board.

[0044] According to an advantageous proposal, assembly then takes place.

[0045] An essential aspect of the present invention is the provision of a novel and inventive forming station for the production of corresponding fiberboards. According to the invention, the forming station comprises a pair of rollers for forming and curing an activated fiber cake. This pair of rollers comprises at least one roller heated as described, with both rollers having surfaces designed to impart the desired deformation to the fiber cake. The term "roller" in the sense of the present invention is to be interpreted broadly, and can also include short belt units.

[0046] The fiberboard hardens after a very short treatment with heat and moisture. Once formed, it remains stable in its shape. It requires no webs and is reproducible at any time. Furthermore, it is resource-efficient and recyclable. More than 80% of its components are organic. It can be manufactured with formaldehyde-free binders and, unlike other lightweight constructions, can be used without a frame due to its high inherent stability. Due to its design, it offers greater stability than comparable solid material products, yet fills a large volume with low weight. Furthermore, it can be provided with a smooth, homogeneous surface, allowing it to be directly coated or laminated with various materials.

[0047] Depending on the application, fiberboard is particularly suitable for the construction of sandwich products. Similar fiberboards can be placed on top of one another. If these are arranged at an angle to one another, a very large composite is created with two lightweight, deformed fiberboards. Flat panels can also be placed on top. This type of paneling results in very stable elements. These can be used, for example, as door leaves and the like. While in the prior art, honeycomb structures and the like usually involve applying glue over the entire surface to produce sandwich composites, because the glue is usually sprayed on, the invention proposes applying glue only in a minimal contact area between adjacent panels.It is conceivable to grind the corrugation tips flat and then apply glue to the corrugation crests using a roller, a slim syringe, a mask, or similar method, to then bond them to another corrugated board or a flat board. This minimal application of glue means that the entire board is not covered with a film. This results in less evaporation, lower weight, and the material properties of the fiberboard material are fully utilized.

[0048] The invention provides a novel manufacturing process that enables the production of fiberboards with exceptional mechanical stability and low weight relative to volume using a novel manufacturing unit with manageable economic expenditure. Further advantages and features of the invention will become apparent from the following description based on the figures. In the figures: Fig. 1A schematic side view of a fiberboard according to the invention; Fig. 2A perspective partial view of a fiberboard according to the invention; and Fig. 3A schematic side view of a sandwich panel.

[0049] Figure 1 shows a fiberboard 1, which in the illustrated embodiment has a progressive rectangular wave structure. For illustrative purposes, the dimensions of the board thickness 2 and the board height 3 are shown. The board height, together with the board circumference, is the measurement used to calculate the board's volume. It can be seen that a very large volume can be achieved with a very inherently stable, thin board 1, which has a thickness of only 2.

[0050] Figure 2 shows schematically a plate 4 with an essentially synus-shaped deformation curve.

[0051] It is quite obvious that these panels, in a sandwich but also on their own, offer high mechanical strength with a low density.

[0052] Like the Figure 3 As shown in the illustration of a sandwich panel, for example, a corrugated and deformed panel 5 according to the invention is covered with two flat panels 6 and 7 on both surfaces. This results in contact lines along the wave groups. The areas indicated by 8 are connection areas in which adhesive is applied. The tips of the panels 5 can be leveled beforehand, for example by grinding. The adhesive can be applied in the connection areas 8 by means of a roller, by linear spraying, by means of a mask or the like. The sandwich composite is created by subsequent pressing. In the area of ​​the lower flat panel, corresponding connection areas are formed in the same way.

[0053] The described embodiments are for illustrative purposes only and are not restrictive. List of reference symbols

[0054] 1Plate 2Thickness 3Height 4Plate 5Deformed plate 6Flat plate 7Flat plate 8Connection areas

Claims

1. Method for producing a fiberboard panel from wood fibers and binding agents, wherein a wood fiber mat comprising a binding agent and having a predetermined thickness and moisture content as well as a predetermined basis weight is subjected to steam in a continuous process in a steaming unit, wherein binding agents are activated, and is then three-dimensionally shaped between at least one pair of rollers.

2. Method according to claim 1, characterized in that the wood fiber mat is provided in a continuous process.

3. Method according to one of the preceding claims, characterized in that the steam temperature is between 100°C and 110°C.

4. Method according to one of the preceding claims, characterized in that the steam pressure is between 0.1 and 8 bar.

5. Method according to one of the preceding claims, characterized in that the steam quantity is between 60 and 500 kg / h.

6. Method according to one of the preceding claims, characterized in that before the wood fiber mat enters the at least one pair of rollers, it is coated with a separating agent.

7. Method according to claim 6, characterized in that the separating agent is selected so that it promotes the setting time of the binding agent.

8. Method according to one of the preceding claims, characterized in that the pressure in the pair of rollers is in the range from 150 N / mm2 to 300 N / mm2.

9. Method according to one of the preceding claims, characterized in that the temperature in the pair of rollers is between 100°C and 350°C.

10. Method according to one of the preceding claims, characterized in that the wood fiber mat is passed through the pair of rollers at a speed of 0.5 n / min to 120 m / min.

11. Method according to one of the preceding claims, characterized in that the wood fiber mat is treated with an additional temperature supply after leaving the roller pairs.

12. Method according to one of the preceding claims, characterized in that the deformed wood fiber mat is cured for between 2 and 5 minutes.