Method for producing a wood panel and wood panel production device

Abstract

The invention relates to a method for producing a wooden composite board, comprising the steps: producing of a raw wooden composite board which has a first side surface, a second side surface which runs parallel to the first side surface, and edge surfaces which connect the side surfaces to one another; applying of a flame retardant-containing liquid at least to the first side surface; and applying of a negative pressure to the second side surface, with the result that the flame retardant-containing liquid is sucked into an edge zone of the raw wooden composite board; and / or applying of a positive pressure to the first side surface, with the result that the flame retardant-containing liquid is pressed into an edge zone of the raw wooden composite board, with the result that the wooden composite board is produced.

Description

[0001] The invention relates to a method for producing a wood-based panel according to the preamble of claim 1. According to a second aspect, the invention relates to a wood-based panel manufacturing apparatus according to the preamble of claim 11.

[0002] Such processes and wood-based panel manufacturing equipment are known and used for the production of wood-based panels. In order to use renewable raw materials such as wood as building materials, it is often required that these materials be flame-retardant.

[0003] The production of flame-retardant wood-based panels has been known for several decades. In this process, the raw materials, such as wood chips, wood fibers, or coarse shavings, are treated with a flame-retardant liquid before the pre-product layer is formed. This is done by spraying the raw materials in mixers, coils, or blow lines. The raw materials are then spread onto a conveyor belt to create at least one pre-product layer. This layer is then pressed to form the wood-based panel.

[0004] A disadvantage of this approach is that it results in a comparatively high amount of waste, as the flame retardant content in the wood-based panel is often not high enough, especially at the beginning of production.

[0005] The EP 3 388 213 A2 ,The preamble of claim 1 describes a method for producing a flame-retardant and / or hardened wood fiberboard. The process begins with arranging a cut-to-size wood fiberboard on a processing device.

[0006] Flame retardant and / or strengthening agent is then applied to one side of the wood fiberboard. The applied agent is drawn or forced into the wood fiberboard by applying negative pressure to the underside and / or positive pressure to the top side.

[0007] The EP 3 127 670 A2 ,The preamble of claim 11 describes a method for impregnating wood fiberboards, where the boards are mounted as an endless strand on a transport device. The strand is continuously fed through an impregnation station to introduce an impregnating medium into the wood fiberboard from above. The impregnating medium is applied by means of a plurality of application devices, which are arranged in at least one row across the full width of the individual boards or the continuous strand of boards and are individually controllable, in a time-controlled manner during the continued transport of the individual boards of the strand or the continuous strand of boards. The impregnated boards exhibit the impregnation only in the areas where it is necessary to achieve the desired performance properties.

[0008] EP 2168 738 A1 describes a method for producing a wood fiberboard, comprising the steps of: pressing a fiber fleece into a raw wood fiberboard, applying an aqueous liquid at least to parts of a top surface of the raw wood fiberboard and applying a vacuum at least to parts of the underside by means of a suction table, so that the aqueous liquid is drawn into and / or through the raw wood fiberboard.

[0009] CN 112440347 A, which discloses the preamble of claim 15, describes a wood-based panel containing magnesium hydroxide as a flame retardant, which is added to the chips before pressing. The invention is based on the objective of improving the production of flame-retardant wood-based panels.

[0010] The invention solves the problem by means of a method having the features of claim 1. The invention also solves the problem by means of a wood-based panel manufacturing device having the features of claim 11. According to a third aspect, the invention solves the problem by means of a wood-based panel having the features of claim 15.

[0011] By introducing the flame retardant using the flame-retardant-containing liquid after pressing, the flame retardant content in the wood-based panel can often be adjusted with a high degree of process reliability. This reduces rejects compared to state-of-the-art methods.

[0012] A further advantage of the invention is that the consumption of flame retardants can generally be reduced. In the known method of manufacturing flame-retardant wood-based panels, flame retardant is lost during the spraying of the pre-products and during the subsequent transport of the sprayed pre-products. Losses of more than 20% of the flame retardant are common.

[0013] This applies particularly to wood-based panels that do not consist of defined face and core layers and are also manufactured separately. In these cases, all the wood material used to manufacture the panel must be treated with flame retardant. Since the face layers typically only make up 30 to 40% of the wood-based panel, 60 to 70% of the flame retardant is wasted. This is especially true for MDF and HDF panels.

[0014] Another advantage is that adding the flame retardant generally does not increase the moisture content of the shredded raw materials. High moisture content can lead to so-called steam cracks in the press, which is undesirable. A steam crack is an area where the wood-based panel has cracked due to evaporating water.

[0015] It is also generally unnecessary to increase the binder content, i.e., the binder and / or adhesive content in the precursor layer, when flame retardants are added. Many binders, for example, polymeric diphenylmethane diisocyanate, react with some flame retardants. Therefore, in prior art processes, more binder must be added when flame retardants are used than when a wood-based panel is produced without flame retardants. This disadvantage is generally eliminated in the production process according to the invention.

[0016] A further advantage is that – unlike prior art processes – the press speed generally does not need to be reduced. Since, in prior art, the flame retardant is introduced in a liquid before pressing, the moisture content of the pre-product layer often increases. To prevent vapor splitting, the press speed and / or the pressing temperature usually have to be reduced. This is unnecessary with a process according to the invention.

[0017] The method according to the invention can also be carried out, at least in principle, independently of the time and place of production of the raw wood-based panel. This makes it possible to retrospectively render previously produced, non-flame-retardant raw wood-based panels flame-retardant. In particular, the flame retardant is applied to the already pressed raw wood-based panel. Thus, it is possible, and according to a preferred embodiment of the invention, for the raw wood-based panel to be stored and / or moved for an extended period of time after pressing, in particular for at least one minute, and in particular for at least 10 minutes, before the flame-retardant liquid is applied. For example, the raw wood-based panels are stored in a cooling star turner. This allows for flexible production of flame-retardant wood-based panels, especially in small quantities.However, it is also possible, and encompassed by the invention, that the liquid application device is arranged near the press. Preferably, the distance between the liquid application device and the press is at most 100 m, or at most 50 m, and in particular at most 30 m.

[0018] For the purposes of this description, a raw wood-based panel is understood to mean, in particular, a panel made of a wood-based material that can be processed into a wood-based panel by incorporating the flame retardant.

[0019] The application of the liquid is understood to mean, in particular, bringing the liquid into contact with the first side surface. Preferably, a liquid film forms on the side surface.

[0020] The term "edge zone" refers to an area of ​​the raw wood-based panel that is bounded by a side surface and does not extend to the center of the panel. The characteristic that the liquid is absorbed into the edge zone means, in particular, that it is possible, but not necessary, for the liquid to be absorbed exclusively into the edge zone.

[0021] Applying the liquid to the raw wood-based panel means, in particular, bringing the liquid into contact with a surface of the raw wood-based panel. The liquid can be applied to the raw wood-based panel from above or from below.

[0022] According to a preferred embodiment, the liquid application device is designed and / or arranged to apply the liquid from below onto the raw wood-based panel.

[0023] In this case, it is advantageous if the suction device for automatically applying the negative pressure is arranged from above.

[0024] Examples of raw wood-based panels include medium-density fiberboard (MDF), high-density fiberboard (HDF), oriented strand board (OSB), particleboard, plywood, soft fiberboard, hard fiberboard, flexible plywood, multiplex, blockboard, stripboard, glued laminated timber, low-density fiberboard (LDF), and insulation boards.

[0025] The thickness of the wood-based panel is preferably at least 6 mm, in particular at least 10 mm, in particular at least 15 mm, in particular at least 20 mm. Alternatively or additionally, the thickness of the wood-based panel is preferably at most 50 mm, in particular at most 30 mm, in particular at most 28 mm, in particular at most 25 mm.

[0026] The flame-retardant liquid contains a flame retardant. Preferably, the liquid is aqueous. It is advantageous if the flame retardant contains phosphorus. The flame retardant may comprise organic and / or inorganic phosphorus compounds, for example, phosphate, polyphosphate, phosphonate, and / or a guanidine salt. It is possible that the flame retardant is based on melamine or melamine derivatives, aluminum hydroxide, or alkali sulfates. However, it is preferred that the boron content of the flame retardant is at most one percent by weight. Preferably, the flame retardant contains ammonium.

[0027] The manufactured wood-based panel is flame-retardant according to DIN EN 13501-1:2010.

[0028] It is advantageous if the bulk density of the raw wood-based panel and / or the wood-based panel is at least 550 kg / m³, and particularly at least 600 kg / m³. Preferably, the bulk density of the raw wood-based panel and / or the wood-based panel is at most 1000 kg / m³, and particularly at most 800 kg / m³. However, it can also be advantageous if the bulk density of the raw wood-based panel is below 350 kg / m³, for example, below 300 kg / m³. This is particularly the case if the raw wood-based panel is an insulating panel.

[0029] The application of the flame-retardant liquid and / or the creation of the vacuum can be carried out on both moving and stationary raw wood-based panel panels.

[0030] Preferably, the overpressure is applied locally, and the flame-retardant liquid is introduced within the area of ​​overpressure. Local application of the overpressure means that the overpressure is not applied to the entire surface of the wood-based panel. For example, the area to which the overpressure is applied is smaller than half the total surface area of ​​the wood-based panel.

[0031] Preferably, an applicator is pressed against the raw wood-based panel, creating an injection chamber between the applicator and the panel, which is sealed by a gasket on the applicator. This reduces leakage of pressurized fluid, which would otherwise build up pressure in the injection chamber.

[0032] The applicator is preferably part of the liquid application device.

[0033] To maintain the seal, the applicator is pressed against the raw wood-based panel. This is preferably done from below. Alternatively, the applicator is pressed against the raw wood-based panel from above.

[0034] Preferably, the flame-retardant liquid is injected or injected into the injection chamber. It is advantageous if, during injection, the flame-retardant liquid fills at least half, preferably at least 75%, of the injection chamber's volume. This keeps the gas volume in the injection chamber low and allows the injection pressure to be quickly built up and released. After the flame-retardant liquid has been injected into the injection chamber and thus into the raw wood-based panel, the injection pressure is reduced, particularly to ambient pressure.

[0035] Preferably, after reducing the application pressure, the applicator is moved relative to the raw wood-based panel. The applicator is then pressed against the raw wood-based panel again, and more flame-retardant liquid is injected into the application chamber. The application pressure is then reduced, and these steps are repeated until the raw wood-based panel is coated with flame retardant on all specified surfaces.

[0036] To facilitate the introduction of the flame-retardant liquid into the raw wood-based panel, a vacuum is applied to the panel, preferably from above, or alternatively from below. This is preferably done in the area where positive pressure is applied from the opposite side of the panel. In other words, a vacuum is applied to a side surface that corresponds to a pressure surface against which the flame-retardant liquid is injected. The vacuum is applied using a suction device.

[0037] It is possible, but not necessary, for the applicator to be moved relative to the raw wood-based panel when applying the flame-retardant liquid. It is also possible for the raw wood-based panel and the applicator to be moved simultaneously, so that the applicator remains stationary relative to the raw wood-based panel but is moved within the space.

[0038] Preferably, the suction device has a suction bell that can be automatically positioned at a predetermined location. The suction device is preferably designed to position the suction bell always opposite the applicator. For this purpose, a drive for the suction bell, which can also be referred to as a positioning drive, is controlled by a control unit of the wood-based panel manufacturing device. A suction bell is understood to be a component which, when it rests against the raw wood-based panel, forms a sealed cavity against which a vacuum can be applied. It is possible, but not necessary, for the walls of the suction bell to be elastic, in particular entropically elastic; however, they can also be rigid. Preferably, the suction bell has a seal with which it rests against the wood-based panel.

[0039] The negative pressure is applied such that the internal concentration of flame retardant in an inner thickness quintile extending from the first to the second side surface of the wood-based panel is at most 0.7 times the external concentration in a first outermost thickness quintile extending to the first side surface. It is advantageous if the internal concentration is at most 0.6 times, preferably 0.5 times, particularly preferably 0.4 times, especially 0.3 times, particularly preferably 0.2 times, for example, at most 0.1 times the external concentration.

[0040] To determine the internal concentration of flame retardant, a cuboid with a base measuring 5 cm x 5 cm is first cut from the wood-based panel. The base is parallel to the first side face. Subsequently, slices are cut from both sides, parallel to the side face, each slice being 0.2 times the thickness of the wood-based panel. The mass of flame retardant in the resulting sample is determined and divided by the total mass of the sample. This yields the internal concentration.

[0041] The external concentrations are obtained by analyzing the material of a disc with a thickness 0.2 times that of the wood-based panel, where one side of the disc is the first side surface.

[0042] If the wood-based panel is an oriented strand board (OSB), the concentration of flame retardant in at least one face layer is at least 65% higher, preferably at least 50% higher, and particularly at least 100% higher, than the concentration of flame retardant in a core layer. The core layer is positioned between the two face layers. The face layer is formed from a layer of pre-products that was spread separately from another layer, from which the core layer is formed during pressing.

[0043] It is advantageous if the liquid is applied in such a way that at least 80%, and preferably at least 90%, of the surface area of ​​the wood-based panel's edge zone contains flame retardant. In other words, this means that at most 10% of the wood-based panel's edge zone should not contain flame retardant. This reduces the amount of panel that has to be discarded because it does not contain a sufficient amount of flame retardant.

[0044] In particular, the flame retardant is also applied outside the edge area of ​​the wood-based panel. The edge area includes all points on the wood-based panel whose distance to the edge of the panel is no more than 10 cm.

[0045] The liquid can be applied by spraying, rinsing, spreading, rolling, pouring, or other methods. Spraying can be done, for example, using overpressure, where the liquid is forced through a nozzle. Alternatively, spraying can be done by atomization. In particular, the liquid can be applied to a moving, especially rotating or vibrating, body so that droplets form.

[0046] It is advantageous if the concentration of flame retardant in the liquid corresponds to at least half, and in particular at least 65%, of the flame retardant's solubility. At the temperature at which the liquid comes into contact with the raw wood-based panel, the flame retardant has a solubility that can be measured, for example, in grams per liter. This solubility is the maximum mass of flame retardant that can be dissolved per unit volume of liquid. The concentration of the flame retardant in the liquid is at least half of this solubility. This means that only a small amount of liquid needs to be applied to the raw wood-based panel. In other words, the ratio of the actual concentration of the flame retardant according to DIN 1310 to its solubility is at least 0.5, in particular at least 0.65, and preferably at least 0.75.

[0047] Preferably, the concentration of flame retardant in the liquid is at least 30% by weight, in particular at least 40% by weight, preferably at least 50% by weight.

[0048] The liquid is preferably a solution, particularly aqueous, or a suspension, particularly aqueous.

[0049] Preferably, the liquid contains at least one dye. The dye is preferably selected such that the flame retardant content, in particular spatially resolved, can be determined from the color of a cross-section of the wood-based panel.

[0050] For example, the dye is a fluorescent dye, so the flame retardant content can be determined by irradiating the cross-section of the wood-based panel with excitation light and spatially resolving the intensity of the resulting fluorescent radiation. This allows for particularly simple quality control.

[0051] Preferably, the liquid temperature when applied to the surface is at least 40°C, particularly at least 50°C, and most preferably at least 60°C. At higher temperatures, the solubility of flame retardants generally increases. Therefore, a higher temperature means that less liquid is required to apply a given amount of flame retardant. It is advantageous if the temperature is less than 100°C, particularly less than 90°C.

[0052] According to a preferred embodiment, the surface temperature of the first side surface is at least 30°C, and in particular at least 40°C, when the liquid is applied. Alternatively or additionally, the surface temperature is preferably at most 65°C, and in particular at most 50°C. It is advantageous if the surface temperature is at most 20°C, and in particular 10°C, lower than the liquid temperature. Preferably, the surface temperature is at least as high as the liquid temperature. In this case, the flame retardant does not precipitate out of the liquid and can be drawn into the edge zone.

[0053] Preferably, the surface temperature of the first side surface at the location where the flame-retardant liquid is applied is lower than the liquid temperature. For example, the difference between the surface temperature and the liquid temperature is preferably at least 5 Kelvin, and more particularly at least 10 Kelvin. Flame-retardant solutions generally dissolve poorly in solvents, especially water. However, solubility increases with temperature. To minimize the amount of water introduced into the raw wood-based panel, the temperature of the flame-retardant liquid is chosen to be higher than the surface temperature. Upon penetration into the raw wood-based panel...

[0054] The incorporation of the flame retardant into the raw wood-based panel according to the invention is particularly effective when the concentration of flame retardant in the liquid, at the surface temperature of the first side surface at the point where the flame retardant-containing liquid is applied, is above a saturation concentration of the flame retardant in the liquid. In this case, the flame retardant precipitates from the solution shortly after contact of the flame retardant-containing liquid with the raw wood-based panel, resulting in a particularly high concentration of flame retardant in the outer areas of the raw wood-based panel. The application rate per unit area is preferably at least 0.3 kg / m² and / or at most 5 kg / m².

[0055] It is advantageous if the application rate of liquid, measured, for example, in liters per square meter, is selected so that the moisture content of the surface layer of the wood-based panel deviates from the core moisture content by no more than 30% after the liquid has been absorbed into the edge zone. When at least one pre-product layer is pressed to form the raw wood-based panel, the panel loses water in the edge zone through evaporation. This creates a moisture gradient within the panel, which is undesirable. Applying the flame-retardant liquid can at least partially compensate for this moisture loss in the edge zone. This generally eliminates the need for any subsequent treatment that might otherwise be necessary, such as in a climate chamber.

[0056] Preferably, the negative pressure is at least 100 hPa, more preferably at least 150 hPa, more preferably at least 200 hPa, and most preferably at least 300 hPa. This means that the pressure deviates from the ambient pressure by at least 300 hPa. It is advantageous if the negative pressure is at least 400 hPa. For example, the pressure is at least 50 hPa and / or at most 700 hPa.

[0057] According to a preferred embodiment, the method comprises the steps of: (a) after drawing the liquid into the edge zone of the first side surface, rotating the raw wood-based panel, (b) applying the liquid to the second side surface, and (c) applying a vacuum to the first side surface so that the liquid is drawn into the edge zone of the second side surface of the raw wood-based panel, thus forming the wood-based panel. In other words, the treatment with the flame-retardant solution is carried out from both sides.

[0058] It is advantageous if the process includes the steps (a) spreading a first surface chip layer, (b) spreading at least one middle chip layer arranged on it, (c) spreading a second surface chip layer arranged on the middle chip layer, and (d) pressing the layers together to form the raw wood-based panel, which has a first surface layer formed from the first surface chip layer, a middle layer formed from the middle chip layer, and a second surface layer formed from the second surface chip layer.

[0059] Preferably the method comprises step (d1) applying the flame-retardant liquid with an area-specific application quantity of liquid that corresponds to at least 10 weight percent of an area-specific mass of the first cover layer.

[0060] Alternatively or additionally, the method preferably comprises step (d2) applying the flame-retardant-containing liquid with an area-specific application rate of flame retardant that corresponds to at least 10 percent by weight of the area-specific mass of the surface layer. It has been found that this generally results in a flame-retardant wood-based panel.

[0061] It is advantageous if the first and / or second surface layer of chipboard consists of coarse chips. Alternatively or additionally, at least one surface layer can consist of fine chips.

[0062] Alternatively or additionally, the middle layer of particleboard consists of coarse wood chips. However, the first and / or second outer layers of particleboard do not necessarily have to consist of coarse wood chips; they can also consist of other wood-containing pre-products. The same applies to the middle layer of particleboard.

[0063] Preferably, the coarse chips are not flame retardant or contain flame retardants in a concentration so low that the proportion of the flame retardant introduced into the wood-based panel via the coarse chips corresponds to at most 50 percent by weight, in particular at most 30 percent by weight, preferably at most 10 percent by weight, of the total flame retardant contained in the wood-based panel.

[0064] A wood-based panel manufacturing device according to the invention preferably has a pressure application device for applying overpressure to a pressure surface. The pressure surface is the surface that can be pressurized by means of the pressure application device. The pressure surface preferably, but not necessarily, comprises at most 50% of the surface area of ​​the wood-based panel.

[0065] The wood-based panel manufacturing device preferably has a control unit designed to control components of the wood-based panel manufacturing device so that a generic process is automatically carried out.

[0066] Preferably, the wood-based panel manufacturing device has an applicator with a seal. The applicator is designed to press against the raw wood-based panel, creating an insertion space between the applicator and the raw wood-based panel, which is sealed by the seal.

[0067] Preferably, the applicator has an actuator, for example a hydraulic cylinder, a pneumatic cylinder, or an electric drive, for pressing against the raw wood-based panel. The wood-based panel manufacturing device may have a positioning device, for example a robot, for positioning the applicator.

[0068] In a wood-based panel according to the invention, the internal concentration of flame retardant in an inner thickness quintile extending from the first side surface to the second side surface is at most 0.7 times, in particular at most 0.6 times, more preferably at most half, in particular at most 0.4 times, more preferably at most 0.3 times, and most preferably at most 0.1 times, of the external concentration in a first outermost thickness quintile extending to the first side surface. In other words, the internal concentration of flame retardant is significantly lower than the concentration of flame retardant in the edge zone adjacent to the side surface. It has been found that the flame retardant is particularly effective at this location.

[0069] It is advantageous if the second-decile concentration of flame retardant according to the invention in the second thickness decile is at least 0.1 times the first-decile concentration in the first outermost thickness decile. In other words, flame retardant is not only present in the outermost deciles, but is also introduced further into the interior of the raw wood-based panel.

[0070] If the wood-based panel according to the invention is a oriented strand board (OSB), as provided in a preferred embodiment, it is preferably a fire-resistant building panel. In particular, this OSB is designed for use in buildings. If the wood-based panel according to the invention is an HDF panel, it can be used, for example, as floor, wall, or ceiling cladding.

[0071] A wood-based panel according to the invention in the form of an MDF panel is suitable, for example, as a door leaf or as a furniture front.

[0072] According to the invention, an insulating element, for example a facade insulating element, has at least one layer made of a wood-based panel according to the invention.

[0073] The invention will now be explained in more detail with reference to the accompanying drawings. These drawings show Figure 1 shows a schematic view of a wood-based panel manufacturing device according to the invention for carrying out a method according to the invention for producing a wood-based panel according to the invention. Figure 2 shows a schematic cross-sectional view of a suction device of the wood-based panel manufacturing device according to the invention. Figure 1Figure 3, in sub-figures 3a, 3b and 3c, each a schematic cross-section through a wood-based panel according to the invention, which was produced according to the invention; Figure 4 a section of a wood-based panel manufacturing device according to a second embodiment according to the invention; Figure 5 a schematic representation of two applicator rounds of the wood-based panel manufacturing device according to the invention. Figure 4 Figure 6 shows in sub-figures 6a and 6b two views of a part of a wood-based panel manufacturing device according to a third embodiment and in sub-figure 6c a cross-sectional view of a part of a wood-based panel manufacturing device according to a third embodiment.

[0074] Figure 1Figure 10 schematically shows a wood-based panel manufacturing device 10, which includes a press 12 in the form of a continuous belt press for pressing at least one pre-product layer 14, in this case three pre-product layers 14, into a raw wood-based panel 16. The at least one pre-product layer 14 is produced by a spreading device 18.

[0075] In the present case, the spreading device 18 comprises a first spreader 20.1 for spreading a first pre-product layer 14.1 in the form of a first top chip layer, a second spreader 20.2 for spreading a second pre-product layer 14.2 in the form of a middle chip layer and a third spreader 20.3 for spreading a third pre-product layer 14.3 in the form of a second top chip layer.

[0076] After pressing using the press 12, the resulting raw wood-based panel 16 has a first top layer 22.1, a middle layer 22.2 and a second top layer 22.3.

[0077] The press 12 is heated, for example, by means of a thermofluid 24 that flows in heating tubes 26.1, 26.2, ... The heat of the thermofluid 24 is transferred to a circulating press belt 28, which is pressed onto the pre-product layers 14.i by means of pressure rollers 30.1, 30.2, ...

[0078] In a material flow direction M behind the press 12, a liquid application device 32 is arranged, by means of which a flame-retardant liquid 34 can be applied to a first side surface S1 of the raw wood-based material plate 16.

[0079] In addition, a suction device 36 is arranged in the material flow direction M behind the press 12, by means of which the liquid 34, which was applied to the first side surface S1, is sucked into the raw wood-based panel 16.

[0080] The liquid application device 32 comprises a liquid reservoir 38 and a pump 40, by means of which the liquid 34 is directed to at least one nozzle 41 at a liquid pressure p 34. The nozzle 41 generates a spray mist 42, which settles on the first side surface S1. The nozzle 41 can be part of a nozzle bar 43, which has three or more nozzles.

[0081] The liquid application device 32 has a temperature control device that keeps the liquid 34 at a predetermined temperature T 34.

[0082] Figure 2 Figure 1 shows an enlarged view of the suction device 36, which has a vacuum table 37 with a circumferential seal 44 that seals the second side surface S2 against a suction chamber 46. The suction device 36 has supports 48j (j = 1, 2, ...) that support the raw wood-based panel 16.

[0083] The suction chamber 46 is connected to a vacuum pump 52 via a vacuum line 49. Preferably, a pressure p 46 of less than p 46 = 500 hPa is applied to the suction chamber. This draws the liquid 34 into a first edge zone 50.1 of the raw wood-based panel. After a predetermined suction time t saug, the suction chamber is vented, the raw wood-based panel 16 is turned over, the pressure p 46 is again applied to the suction chamber, and liquid 34 is applied to the second side surface. After the predetermined suction time t saug, the suction chamber is vented again.

[0084] The liquid application device 32 can, alternatively or additionally to the nozzle 41, for example include an application roller 53 or another device for applying the liquid 34 to the first side surface S1.

[0085] Figure 3aschematically shows a cross-section through a wood-based panel 54 according to the invention, which has a first edge surface K1 and a second edge surface K2.

[0086] In Figure 3b The concentration c F,54 of flame retardant in the wood-based panel 54 is shown as a function of the distance z from the nearest side surface. It can be seen that the concentration is highest at the surface. With increasing distance z from the first side surface S1 of the wood-based panel 54, the concentration decreases until reaching the center of the wood-based panel 54.

[0087] In an inner thickness quintile Q3, the wood-based panel 54 has an inner concentration cF,Q3 of flame retardant. In a first outermost thickness quintile Q1, the wood-based panel 54 has a first outer concentration cF,Q1 of flame retardant. In a second outermost thickness quintile Q5, the wood-based panel 54 has a second outer concentration cF,Q5.

[0088] It can be seen that the external concentration is significantly higher than the internal concentration. In this case, c F,Q3 = 0.25 · c F,Q1 .

[0089] Figure 3c The diagram shows a subdivision into deciles. It can be seen that a second-decile concentration c F,D2 of flame retardant in the second thickness decile of the thickness extent, which lies towards a midpoint of the thickness extent next to the first, outermost thickness decile, is at least 0.1 times a first-decile concentration c F,D1 in the first outermost thickness decile.

[0090] Figure 4Figure 1 shows a liquid application device 32 of a wood-based panel manufacturing device 10 according to the invention, which has a pressure application device 56 that, by means of the pump 40, introduces flame-retardant liquid 34 from the liquid reservoir 38 into an application chamber 58 under an application pressure pe. The application chamber 58 is delimited by a seal 60 of the pressure application device. The pressure application device 56 can be configured to apply the flame-retardant liquid 34 from below or from above.

[0091] By means of the vacuum pump 52 of the suction device 36, a negative pressure can be applied to the raw wood-based panel 16 via the vacuum line 49. For example, a pressure p 46 in the suction chamber 46 is at most p 46 = 700 hPa. This corresponds to a negative pressure of at least 300 hPa.

[0092] Figure 5Figure 1 schematically shows that the suction device 36 can be designed to apply a local negative pressure. In this case, the suction area Fs is smaller than the area of ​​the raw wood-based panel 16. In the present case, the suction area Fs is less than one-tenth the area of ​​the raw wood-based panel 16.

[0093] The wood-based panel manufacturing device can also have a second suction device 36', which is preferably identical in construction to the first suction device 36.

[0094] A pressure surface FD, on which the pressure application device 56 applies the application pressure pe, essentially corresponds to the suction surface F s, i.e., for example, with a deviation of at most a factor of 2, in particular at most a factor of 1.1, in particular at most a factor of 1.25.

[0095] Figure 6aFigure 62 shows a positioning device, for example a robot, for positioning an applicator 64 and pressing the applicator 64 against the raw wood-based panel 16. For this purpose, the positioning device 62 has, for example, an arm 66. The arm 66 can have two or more partial arms 68.1, 68.2, which can be articulated together. The applicator 64 can be automatically positioned to a predefinable position relative to the raw wood-based panel 16 by means of a drive 70.

[0096] The applicator 64 is supplied with pressurized liquid 34 via a flexible line 72, which is sprayed onto the raw wood-based panel 16 and / or pressed into the raw wood-based panel 16 under pressure.

[0097] Irrespective of the other features mentioned for the present embodiment, the wood-based panel manufacturing device 10 can have a suction device 36 which includes a suction bell 74 that can be positioned at a predetermined location. The suction device 36 is designed such that the suction bell 74 is always arranged opposite the applicator 64. For this purpose, the drive 70 is controlled by a control unit 76 of the wood-based panel manufacturing device 10. The suction bell 74 is connected to the vacuum pump 52 by means of a flexible vacuum line.

[0098] Figure 6c Figure 1 shows a further embodiment of a pressure application device 56, in which the flame-retardant liquid 34 is introduced into the injection chamber 58 by means of a nozzle 78. The injection pressure pe can be set by means of a pressure source 80, which is connected to the injection chamber 58 via a pressure line 82.

[0099] It is possible to move the applicator 64 and, if applicable, the suction bell 74 while an overpressure and / or underpressure is applied. Alternatively, the pressure in the suction chamber and / or the insertion pressure is brought close to, and in particular completely close to, the ambient pressure before moving the applicator and / or the suction bell. Example 1:

[0100] An unsanded raw wood-based panel 16 in the form of an OSB panel with a thickness d of d = 20 mm was placed on the vacuum table 37. The raw wood-based panel 16, which had been produced with one percent more PMDI (PMDI: polymeric diphenylmethane diisocyanate) as a binder in the surface layers 22.1, 22.3 compared to a non-flame-retardant wood-based panel, was treated with a solution of the flame retardant Ecoaphos MK 68, 60 wt%, from Ecoatech at a quantity of 0.49 kg / m² using a nozzle bar.

[0101] This corresponds to a quantity of 15 percent by weight based on the area-specific weight of the cover layers 22.1, 22.3. The cover layer thickness is d 22.1 = d 22.3 = 3 mm ± 1 mm. A negative pressure of 300 mbar was applied from the underside. Within t saug = 120 s ± 15 s, the liquid 34, i.e., the flame retardant solution, had completely penetrated the raw wood-based panel 16.

[0102] The raw wood-based panel 16 was rotated and the process repeated. Subsequently, raw wood-based panel 16 (base area: DIN A4, sample 1) was extracted from the panel and tested against a conventionally produced flame-retardant OSB panel. The conventionally produced flame-retardant OSB panel had a comparable amount of the aforementioned flame retardant in its surface layer and had been conditioned prior to testing (humidity: approx. 9%). The samples were then exposed to a gas burner, positioned at a defined distance from the surface, for varying durations. After the exposure time, it was noted whether burning / continued burning was observed, and the duration of any continued burning was determined. Example 2:

[0103] An unsanded raw wood-based panel 16 in the form of an OSB panel with a thickness d = 20 mm (bulk density approx. 650 kg / m³) was placed on the vacuum table 37, which was equipped with the circumferential seal 44. The raw wood-based panel 16, which had been produced with one percent more binder (PMDI) in the surface layer, was treated with a solution of a flame retardant from Ecoatech (Ecoaphos MK 68, 60 wt%) at a rate of 0.49 kg / m³ using the nozzle bar 43. To facilitate penetration, the flame retardant solution had been preheated to approximately T34 = 60°C.

[0104] The liquid was applied at a rate of 15 wt% based on the surface layer strands (surface layer thickness approx. 3 mm per side). A vacuum of 150 mbar was applied to the underside. After a suction time of tsuction = 90 seconds, the flame retardant solution had completely penetrated the raw wood-based panel 16. The raw wood-based panel 16 was then turned over and the process repeated.

[0105] Subsequently, 16 samples were cut from this raw wood-based panel (DIN A4, sample 2) and these were also tested for flammability according to DIN EN 13823:2015 using a conventionally produced, flame-retardant OSB panel.

[0106] The conventionally produced OSB board had a comparable amount of the aforementioned flame retardant in the top layer and had been conditioned before testing (humidity: approx. 9%).

[0107] In the flammability test, the samples were exposed to a gas burner positioned at a defined distance from the surface for varying durations, as shown in the left column of the following table. After the specified exposure time, it was noted whether combustion / continued combustion was observed and the duration of any continued combustion. Table 1: Observations after flame treatment Flame duration Reference (conventionally manufactured OSB) Sample 1 Sample 2 2 min no further burning no further burning no further burning 4 min no further burning no further burning no further burning 8 min no further burning no further burning no further burning 12 min no further burning no further burning no further burning 15 min no further burning no further burning no further burning

[0108] As can be seen from the flame tests, the wood-based panels produced according to the inventive method behave exactly as well as the reference panel. Even after 15 minutes of flame exposure, no further burning was observed in any of the samples after the burner was switched off. Subsequent examination revealed that the wood-based panels produced according to the invention still possessed a significantly higher strength after the test. In the reference panel, individual charred strands could easily be mechanically removed from the structure, which was only possible with considerably more force in the two wood-based panels produced according to the invention. Example 3:

[0109] An unpolished raw wood-based panel 16 in the form of an HDF panel with a thickness d = 8 mm (bulk density approx. 850 kg / m³) was placed on the vacuum table 37, which was equipped with the circumferential seal 44. The raw wood-based panel 16, which had been produced with a 1% binder based on a urea-formaldehyde adhesive, was treated with a solution of a flame retardant from Ecoatech (Ecoaphos MK 68, 50 wt%) at a rate of 0.31 kg / m² using the nozzle bar 43. The binder content was also increased in this panel (2% more than in the standard version). To facilitate penetration, the flame retardant solution had been preheated to approximately T34 = 60°C.

[0110] A quantity of flame retardant equal to 15% by weight of the surface layer (surface layer thickness approximately 1.2 mm per side) was introduced into the wood-based panel using the liquid. A vacuum of 150 mbar was applied to the underside. After a suction time of tsuction = 120 seconds, the flame retardant solution had completely penetrated the raw wood-based panel 16. The raw wood-based panel 16 was then turned over, and the process was repeated.

[0111] Subsequently, 16 samples were cut from this wood-based panel (DIN A4, sample 2) and these were also tested for flammability according to DIN EN 13823:2015 with a conventionally produced, flame-retardant HDF.

[0112] The conventionally produced wood-based panel had a comparable amount of the aforementioned flame retardant in the panel and had been conditioned before testing (humidity: approx. 9%).

[0113] The flammability tests were conducted in the same way as the OSB samples. The results regarding flammability and strength after the fire test were comparable to those obtained with the OSB. Example 4:

[0114] The steps carried out for embodiment 3 were performed for an unsanded raw wood-based panel 16 in the form of an MDF panel with a thickness d = 8 mm (bulk density approx. 750 kg / m 3< ).

[0115] In the flammability tests, the samples were tested exactly like a conventionally manufactured MDF board. The MDF board produced according to the invention achieved or exceeded the results regarding flammability and strength compared to the conventionally manufactured MDF board. Example 5:

[0116] The steps carried out for embodiment 3 were performed for an unsanded raw wood-based panel 16 in the form of a chipboard with a thickness d = 8 mm (bulk density approx. 650 kg / m 3< ).

[0117] In the flammability tests, the samples were tested exactly like a conventionally manufactured particleboard. The particleboard produced according to the invention achieved or exceeded the results regarding flammability and strength compared to the conventionally manufactured particleboard. Example 6:

[0118] The steps carried out for embodiment 3 were performed for an unpolished raw wood-based panel 16 in the form of an insulation panel with a thickness d = 20 mm (bulk density approx. 250 kg / m 3< ).

[0119] In the flammability test, the samples were tested exactly like a conventionally manufactured insulation board. The insulation board produced according to the invention achieved or exceeded the results with regard to flammability and strength compared to the conventionally manufactured insulation board. Reference symbol list 10 Wood-based panel manufacturing device 50 Edge zone 12 press 52 vacuum pump 14 intermediate product location 53 Application roller s14.1 first top layer of chipboard 54 Wood-based panel 14.2 Middle chip layer 56 Pressure application device 14.3 second top layer of chipboard 58 Entry space 16 Raw wood-based panel 18 Spreading device 60 seal 62 Positioning device 20 Spreader 64 Applicator 22.1 first top layer 66 arm 22.2 middle class 68 Partial arm 22.3 second top layer 24 Thermofluid 70 drive 26 heating pipe 72 Line 28 Press band 74 suction cup 76 control unit 30 pressure roller 78 nozzle 32 Liquid application device 34 liquid 36 Suction device 37 Vacuum table c F Flame retardant content 38 liquid reservoir c F,D1 First decile concentration 40 pump c F,D2 Second decile concentration 41 nozzle CF, Q1 first external concentration 42 Spray mist c F,Q3 Inner concentration 43 nozzle bar c F,Q5 second external concentration 44 seal 46 Suction chamber d thickness 48 support D Thickness decile 49 Vacuum line D1 first outermost decile of thickness D10 second outermost decile of thickness F s suction surface FD Print area i Run index of the intermediate product layers j Running index of the supports K Edge surface M Material flow direction p 46 Pressure in the suction chamber pe Application pressure S1 first side surface S2 second side surface Q Thickness quintile Q1 first outermost quintile of thickness Q3 Inner thickness quintile Q5 second outermost quintile of thickness t suck Suction time T temperature Z distance from the surface of the wood-based panel

Claims

1. A method for producing a wood-based material panel (54), comprising the steps: (a) producing a raw wood-based material panel (16) that comprises a first lateral surface (S1), a second lateral surface (S2) that extends parallel to the first lateral surface (S1), and edge surfaces that connect the lateral surfaces (S1, S2) to each other, (b) applying a liquid containing a flame retardant (34) to at least the first lateral surface (S1) and (c) applying a negative pressure to the second lateral surface (S2) so that the liquid (34) containing flame retardant is sucked into a subsurface (50) of the raw wood-based material panel (16) and / or applying an overpressure to the first lateral surface (S1) so that the liquid containing flame retardant (34) is pressed into a subsurface (50) of the raw wood-based material panel (16), resulting in the wood-based material panel (54), characterised in that the concentration of the flame retardant in the liquid (34) at the surface temperature of the first side surface (S1) at the point where the flame-retardant-containing liquid (34) is applied is above a saturation concentration of the flame retardant in the liquid (34).

2. The method according to claim 1, characterised by the following steps (a) pressing an applicator (64) against the raw wood-based material panel so that an introduction chamber (58) forms between the applicator (64) and the raw wood-based material panel that is sealed by a seal (60) of the applicator (64), (b) pressing liquid (34) containing flame retardant into the introduction chamber (58) and (c) then reducing an introduction pressure (pe), in particular to ambient pressure.

3. The method according to claim 2, characterised in that the applicator (64) is pressed against the raw wood-based material panel from below.

4. The method according to claim 2 or 3, characterized by the steps: (d) moving the applicator (64) relative to the raw wood-based material panel after a introduction pressure (pe) has been reduced, (e) pressing the applicator (64) against the raw wood-based material panel once again, (f) pressing liquid (34) containing flame retardant into the introduction chamber (58), (g) reducing the introduction pressure (pe) in the introduction chamber (58), in particular to ambient pressure, and (h) repeating the aforementioned steps until the raw wood-based material panel has been provided with flame retardant.

5. The method according to one of the preceding claims, characterised in that the negative pressure is applied in such a way that an inner concentration (cF,Q3) of flame retardant in an inner thickness quintile (Q3) of a thickness expansion from the first lateral surface (S1) to the second lateral surface (S2) is at most 0.8 times an outer concentration (cF,Q1) in a first outermost thickness quintile (D1) that extends to the first lateral surface (S1).

6. The method according to one of the preceding claims, characterised in that the liquid (34) contains at least one colouring agent which is selected in such a way that a flame retardant content can be determined from a colour of the wood-based material panel (54) in a cross-section7. The method according to one of the preceding claims, characterised in that (a) a liquid temperature of the liquid (34) during application onto the lateral surface is at least 40°C and / or (b) a surface temperature of the first lateral surface (S1) during application of the liquid (34) is at most 50°C.

8. The method according to one of the preceding claims, characterised in that (a) an area-specific application amount of liquid (34) is at least 0.3 kilogram per square metre and / or at most 5 kilogram per square metre and / or (b) an area-specific application amount of liquid (34) is selected in such a way that a surface layer moisture level of a surface layer of the wood-based material panel (54) deviates from the core moisture level by at most 30%.

9. The method according to one of the preceding claims, characterised by the steps (a) rotating the raw wood-based material board (16) after the liquid (34) has been introduced into the subsurface (50) of the first lateral surface (S1), (b) applying the liquid (34) to the second lateral surface (S2) and (c) applying a negative pressure to the first lateral surface (S1) so that the liquid (34) is sucked into a subsurface (50) of the second lateral surface (S2) of the raw wood-based material panel (16), resulting in the wood-based material panel (54).

10. The method according to one of the preceding claims, characterised by the steps: (a) scattering a first surface chip layer (14.1), (b) scattering at least one middle chip layer (14.2) arranged on the first surface chip layer (14.1), and (c) scattering a second surface chip layer (14.3) arranged on the middle chip layer, (d) pressing the layers to form the raw wood-based material panel (16), which comprises - a first surface layer (22.1) resulting from the first surface chip layer (14.1), - a middle layer (22.2) resulting from the middle chip layer (14.2), and - a second surface layer (22.3) resulting from the second surface chip layer (14.3), (e) applying the liquid containing flame retardant (34) with an area-specific application amount of liquid (34) that corresponds to at least 10 percent by weight of an area-specific mass of the first surface layer (22.1).

11. A wood-based material panel production device (10) with (a) a press (12), especially a belt press, for pressing at least one primary product layer (14) to produce a raw wood-based material panel (16), (b) a liquid application device (32) for applying a liquid (34) to the raw wood-based material panel (16) and (c) a suction device (36) that is designed to apply a negative pressure to a lateral surface (S) of the wood-based material panel (16), (d) wherein the liquid (34) contains flame retardant and (e) wherein the suction device (36) is designed to automatically apply the negative pressure for such a suction time (tsaug) that the liquid (34) containing the flame retardant is sucked into a subsurface (50) of the raw wood-based material panel (16) but not through the raw wood-based material panel (16) and / or wherein the wood-based material panel production device (10) has a pressure application device (56) for applying an overpressure to the first lateral surface so that the liquid containing the flame retardant is pressed into a subsurface of the raw wood-based material panel, characterized in that (f) the liquid application device (32) comprises a temperature control device (43), which is set up to keep the liquid (34) at a given temperature (T34), wherein the wood-based production device is designed to introduce the flame retardant into the raw wood-based material panel such that the concentration of the flame retardant in the liquid at the surface temperature of the first side surface at the point where the flame-retardant-containing liquid is applied is above a saturation concentration of the flame retardant in the liquid (34).

12. The wood-based material panel production device (10) according to claim 11, characterized by (a) an applicator (64) designed to press against the raw wood-based material panel so that an introduction chamber (58) forms between the applicator (64) and the raw wood-based material panel that is sealed by a seal (60) of the applicator (64), and (b) a control unit (76) that configured to automatically carry out a method comprising the steps of controlling the applicator (64) (i) so that the applicator (64) presses liquid (34) containing flame retardant into the introduction chamber (58) and (ii) then reduces an introduction pressure (pe) in the introduction chamber (58) to ambient pressure.

13. The wood-based material panel production device (10) according any of claims 11 to 12, characterized in that the applicator (64) comprises an actuator for pressing the applicator (64) against the raw wood-based material panel.

14. The wood-based material panel production device (10) according to any of claims 11 to 12, characterized in that the suction device (36) is arranged to apply a negative pressure to a suction surface (Fs) that corresponds to the pressure surface (FD).

15. A wood-based material panel (54) which is (a) flame-retardant in accordance with the specification standard DIN EN 13501-1: 2010 and the test standard DIN EN 13823:2015, especially in Class B (B -s1 or B - s1 d0), or C (C-s1, C-s1 d0) or Bfl (Bfl -s1 or Bfl -s1 d0), or Cfl (Cfl-s1, Cfl-s1 D0), or Class B1, B2 or B3, especially d0 characterized in that (a) the wood-based material panel (54) has a concentration gradient of flame retardant, wherein the flame retardant concentration reduces as the distance from a surface to a centre of the wood-based material panel (54) increases, (b) an inner concentration of flame retardant in an inner thickness quintile (Q) of a thickness expansion from the first lateral surface (S1) to the second lateral surface (S2) is at most 0.7 times an outer concentration in a first outermost thickness quintile (D1) that extends to the first lateral surface (S1) and (c) a second-decile concentration (cF,D2) of flame retardant in the second thickness decile of the thickness expansion, which lies next to the first outermost thickness decile (D1) in the direction of a centre of the thickness expansion, is at least 0.1 times a first-decile concentration (cF,D1) in the first outermost thickness decile (D1).

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