Method for producing a wood material board and wood material board production device

Abstract

The invention relates to a method for producing a wood-based panel (54), comprising the steps of producing a raw wood-based panel (16) which has a first side surface (S1), a second side surface (S2) which runs parallel to the first side surface (S1), and edge surfaces which connect the side surfaces (S1, S2) to one another, applying a liquid (34) containing a flame retardant at least to the first side surface (S1) and applying a negative pressure to the second side surface (S2) so that the liquid (34) containing a flame retardant is sucked into an edge zone (50) of the raw wood-based panel (16), so that the wood-based panel (54), wherein the liquid (34) is an aqueous solution or a suspension,a concentration of flame retardant in the liquid (34) corresponds to at least half the solubility of the flame retardant and the flame retardant comprises phosphonate and / or a guanidine salt and / or is a flame retardant based on aluminum hydroxide or alkali sulfates.

Description

[0001] The invention relates to a method for producing a wood-based panel. Also disclosed is a wood-based panel production device comprising (a) a press, in particular a belt press, for pressing at least one precursor layer into a raw wood-based panel, (b) a liquid application device for applying a liquid to the raw wood-based panel, and (c) a suction device configured to apply a negative pressure to a side surface of the raw wood-based panel.

[0002] Such processes and wood-based panel manufacturing equipment are well known and are used to produce wood-based panels. In order to use renewable raw materials such as wood as building materials, they are often required to be flame-resistant.

[0003] The production of flame-resistant wood-based panels has been known for several decades. The precursors, such as wood chips, wood fibers, or coarse shavings, are treated with a flame-retardant liquid before the precursor layer is formed from the precursors. This is done by spraying the precursors in mixers, gluing drums (coils), or blow lines. The precursors are then spread onto a belt to create at least one precursor layer. The precursor layer is then pressed into the wood-based panel.

[0004] The 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] EP 3388213A2 discloses the preamble of claim 1

[0006] The invention is based on the object of improving the production of flame-retardant wood-based panels.

[0007] The invention solves the problem by a method for producing a wood-based panel with the steps according to claim 1.

[0008] Also disclosed is a generic wood-based panel manufacturing device in which the liquid contains a flame retardant and in which the suction device is designed to automatically apply the negative pressure for such a suction time that the liquid containing the flame retardant is sucked into an edge zone of the raw wood-based panel, but not through the raw wood-based panel.

[0009] Also disclosed is a wood-based panel which has a, in particular continuous, concentration gradient of flame retardant, wherein the flame retardant concentration decreases with increasing distance from a surface to a center of the wood-based panel. It is advantageous if the wood-based panel is flame-retardant according to the requirements standard DIN EN 13501-1:2010 and the test standard DIN EN 13823:2015. It is particularly advantageous if the wood-based panel is a wood-based panel of class B, in particular B -s1 or B -s1 d0, or C, in particular C-s1, C-s1 d0, or B fl , in particular B fl -s1 or B fl -s1 d0, or C fl , in particular C fl -s1, C fl -s1 D0, or in class B1, B2 or B3.

[0010] By incorporating the flame retardant using a flame-retardant-containing liquid after compression, the flame retardant content in the wood-based panel can often be adjusted with high process reliability. This reduces waste compared to state-of-the-art processes.

[0011] Another advantage of the invention is that the consumption of flame retardants can generally be reduced. In the conventional method of producing flame-resistant wood-based panels, flame retardant is lost during the spraying of the precursors and during subsequent transport of the sprayed precursors. Losses of more than 20% of flame retardant often occur.

[0012] This is especially true for wood-based panels that do not consist of defined top and middle layers and are also manufactured separately. In these cases, all wood material used to manufacture the panel must be treated with flame retardants. Since the top 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.

[0013] Another advantage is that the addition of the flame retardant generally does not increase the moisture content of the shredded precursors. High moisture content can lead to undesirable steam cracking in the press. A steam crack is an area where the wood-based panel has cracked due to evaporating water.

[0014] Increasing the binder content, i.e., the binding agent and / or glue content of the precursor layer, can generally be omitted if flame retardants are added. Many binders, such as polymeric diphenylmethane diisocyanate, react with some flame retardants. Therefore, in state-of-the-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.

[0015] Another advantage is that, unlike with prior art processes, the press speed generally does not need to be reduced. Since the flame retardant is introduced in a liquid prior to pressing in the prior art, the moisture content of the precursor layer often increases. To prevent steam cracking, the press speed and / or the pressing temperature usually have to be reduced. This can be eliminated with a process according to the invention.

[0016] 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 subsequently make already 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. It is thus possible, and according to a preferred embodiment of the invention, provided, that the raw wood-based panel is stored and / or moved for a longer period of time after pressing, in particular at least one minute, in particular at least 10 minutes, before the liquid containing the flame retardant is applied. For example, the raw wood-based panels are stored in a cooling star turner. This allows flexible production of flame-retardant wood-based panels, especially even in small quantities.However, it is also possible, and encompassed by the invention, for the liquid application device to be 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, in particular at most 30 m.

[0017] In the context of the present description, a raw wood-based panel is understood to mean in particular a panel made of a wood-based material which can be processed into a wood-based panel by incorporating the flame retardant.

[0018] Applying the liquid means, in particular, bringing the liquid into contact with the first side surface. In doing so, a liquid film preferably forms on the side surface.

[0019] The edge zone is understood to be an area of the raw wood-based panel that is, on the one hand, delimited by a side surface and, on the other hand, does not extend to the center of the panel. The feature that the liquid is sucked into the edge zone is understood in particular to mean that it is possible, but not necessary, for the liquid to be sucked exclusively into the edge zone.

[0020] The raw wood-based panel is, for example, a medium-density fiberboard (MDF), a high-density fiberboard (HDF), a coarse particle board (OSB), a chipboard, a plywood board, a soft fiberboard, a hard fiberboard, a bent plywood board, a multiplex board, a blockboard, a stickboard, a glued wood board, a low-density fiberboard (LDF) or an insulation board.

[0021] The thickness of the wood-based panel is preferably at least 6 mm, in particular at least 10 mm, particularly preferably at least 15 mm, particularly preferably 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, preferably at most 25 mm.

[0022] The flame retardant-containing liquid contains a flame retardant. The liquid is preferably an aqueous liquid. It is advantageous if the flame retardant contains phosphorus. The flame retardant can comprise organic and / or inorganic phosphorus compounds, for example, phosphate, polyphosphate, phosphonate, and / or a guanidine salt. It is possible for the flame retardant to be based on melamine or melamine derivatives, aluminum hydroxide, or alkali metal sulfates. However, it is preferred that the boron content of the flame retardant be at most one percent by weight. The flame retardant preferably contains ammonium.

[0023] Preferably, the manufactured wood-based panel is flame-retardant according to DIN EN 13501-1:2010. In particular, the manufactured wood-based panel has the properties of a disclosed wood-based panel.

[0024] It is advantageous if the raw density of the raw wood-based panel and / or the wood-based panel is at least 550 kg / cubic meter, in particular at least 600 kg / cubic meter. Preferably, the raw density of the raw wood-based panel and / or the wood-based panel is at most 1000 kg / cubic meter, in particular at most 800 kg / cubic meter. However, it can also be advantageous if the raw density of the raw wood-based panel is below 350 kg / cubic meter, for example, below 300 kg / cubic meter. This is particularly the case if the raw wood-based panel is an insulation board.

[0025] The application of the liquid containing flame retardant and / or the application of the negative pressure can be carried out both when the raw wood-based panel is moving and when it is stationary.

[0026] Preferably, the negative pressure is applied such that an internal concentration of flame retardant in an inner thickness quintile of a thickness extension from the first side surface to the second side surface of the wood-based panel is at most 0.8 times an external concentration in a first outermost thickness quintile extending to the first side surface. It is advantageous if the internal concentration is at most 0.7 times, in particular 0.6 times, preferably 0.5 times, particularly preferably 0.4 times, in particular 0.3 times, particularly preferably 0.2 times, for example at most 0.1 times the external concentration.

[0027] To determine the internal flame retardant concentration, a cuboid with a base area measuring 5 cm by 5 cm is first cut from the wood-based panel. The base area runs parallel to the first side surface. Subsequently, slices are cut from both sides parallel to the side surface, each slice having a thickness 0.2 times the thickness of the wood-based panel. The mass of flame retardant is determined from the resulting sample and divided by the total mass of the sample. This yields the internal concentration.

[0028] The external concentrations are determined by analyzing the material of a slice with a thickness of 0.2 times the thickness of the wood-based panel, with one side of the slice being the first side surface.

[0029] If the wood-based panel is a particle board (OSB), the flame retardant concentration in at least one cover layer is at least 65% higher, preferably at least 50% higher, and in particular at least 100% higher, than the flame retardant concentration in a middle layer. The middle layer is arranged between the two cover layers. The cover layer is formed from a layer of precursors that was spread separately from another layer, from which the middle layer is formed during pressing.

[0030] It is advantageous if the liquid is applied in such a way that the edge zone of at least 80%, in particular at least 90%, of the side surface area of the wood-based panel contains flame retardant. In other words, this means that no more than 10% of the wood-based panel contains any flame retardant in its edge zone. This reduces the amount of material that must be discarded because it does not contain sufficient flame retardant.

[0031] 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 that are within 10 cm of the edge of the panel.

[0032] The liquid can be applied by spraying, rinsing, spreading, rolling, pouring, or other means. For example, spraying can be done using overpressure, forcing the liquid through a nozzle. Alternatively, spraying can be done by atomization. In particular, the liquid can be applied to a moving, particularly rotating or vibrating, body, so that droplets form.

[0033] It is advantageous if the concentration of flame retardant in the liquid corresponds to at least half, in particular at least 65%, of the solubility of the flame retardant. 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 quotient of the actual concentration of the flame retardant according to DIN 1310 and the solubility is at least 0.5, in particular at least 0.65, preferably at least 0.75.

[0034] Preferably, a concentration of flame retardant in the liquid is at least 30 percent by weight, in particular at least 40 percent by weight, preferably at least 50 percent by weight.

[0035] The liquid is preferably a solution, in particular an aqueous solution, or a suspension, in particular an aqueous one.

[0036] The liquid preferably contains at least one dye. The dye is preferably selected such that the flame retardant content can be determined, particularly spatially resolved, from the color of a cross-section of the wood-based panel.

[0037] 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 measuring the intensity of the resulting fluorescent radiation. This allows for particularly simple quality control.

[0038] The liquid temperature of the liquid when applied to the side surface is preferably at least 40°C, in particular at least 50°C, and particularly preferably at least 60°C. At high temperatures, the solubility of flame retardants generally increases. A higher temperature therefore results in less liquid being required to apply a given amount of flame retardant. It is advantageous if the temperature is below 100°C, in particular below 90°C.

[0039] According to a preferred embodiment, the surface temperature of the first side surface during application of the liquid is at least 30°C, in particular at least 40°C. Alternatively or additionally, the surface temperature is preferably at most 65°C, in particular at most 50°C. It is advantageous if the surface temperature is at most 20°C, 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 from the liquid, and the flame retardant can be absorbed into the edge zone.

[0040] The area-specific application rate of liquid is preferably at least 0.3 kg / square meter and / or at most 5 kg / square meter.

[0041] It is advantageous if the area-specific application quantity of liquid, measured, for example, in liters per square meter, is selected such that the moisture content of a top 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 into the raw wood-based panel, the raw wood-based panel loses water in the edge zone through evaporation. This creates an undesirable moisture gradient in the raw wood-based panel. By applying the liquid containing flame retardant, the moisture loss in the edge zone can be at least partially compensated. Any post-treatment that would otherwise be necessary, for example in a climate chamber, can generally be omitted.

[0042] Preferably, the negative pressure is at least 100 hPa, in particular at least 150 hPa, preferably at least 200 hPa, and particularly 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.

[0043] According to a preferred embodiment, the method comprises the steps: (a) after the liquid has been sucked 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 negative pressure to the first side surface so that the liquid is sucked 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-containing solution is carried out on both sides.

[0044] It is advantageous if the method comprises the steps of (a) spreading a first cover chip layer, (b) spreading at least one middle chip layer arranged thereon, (c) spreading a second cover chip layer arranged on the middle chip layer, and (d) pressing the layers to form the raw wood-based panel, which has a first cover layer formed from the first cover chip layer, a middle layer formed from the middle chip layer, and a second cover layer formed from the second cover chip layer.

[0045] Preferably, the method comprises step (d1) applying the flame retardant-containing liquid with an area-specific application quantity of liquid which corresponds to at least 10 percent by weight of an area-specific mass of the first cover layer.

[0046] Alternatively or additionally, the process preferably comprises step (d2) applying the flame retardant-containing liquid with a surface-specific application rate of flame retardant corresponding to at least 10 percent by weight of the surface-specific mass of the cover layer. It has been found that, as a rule, a flame-resistant wood-based panel can be obtained in this way.

[0047] It is advantageous if the first and / or second chipboard layers consist of coarse chips. Alternatively or additionally, at least one chipboard layer can consist of fine chips.

[0048] Alternatively or additionally, the middle chip layer consists of coarse chips. However, the first top chip layer and / or the second top chip layer do not have to consist of coarse chips; they can also consist of other wood-containing precursors. The same applies to the middle chip layer.

[0049] Preferably, the coarse chips do not contain flame retardants or contain flame retardants in a concentration that is so small that the proportion of flame retardant that is introduced into the wood-based panel via the coarse chips corresponds to a maximum of 50 percent by weight, in particular a maximum of 30 percent by weight, preferably a maximum of 10 percent by weight, of the total flame retardant contained in the wood-based panel.

[0050] In a wood-based panel, the internal concentration of flame retardant in an inner thickness quintile of a thickness extension from the first side surface to the second side surface is preferably at most 0.8 times, in particular at most 0.6 times, particularly preferably at most half, in particular at most 0.4 times, preferably at most 0.3 times, and particularly preferably at most 0.1 times, 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.

[0051] It is advantageous if the second-decile concentration of flame retardant in the second thickness decile of the thickness extension 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 also penetrates further into the interior of the raw wood-based panel.

[0052] If the wood-based panel is a particleboard, it is preferably a fire-resistant construction board. This particleboard is particularly designed for use in buildings.

[0053] If the wood-based panel according to the invention is an HDF panel, it can be used, for example, as floor, wall or ceiling paneling.

[0054] A wood-based panel in the form of an MDF board is suitable, for example, as a door leaf or as a furniture front.

[0055] Also disclosed is an insulating element, for example a facade insulating element, which has at least one layer of a wood-based panel.

[0056] The invention is explained in more detail below with reference to the accompanying drawings. Figure 1 shows a schematic view of a wood-based panel manufacturing device for carrying out a method according to the invention for producing a wood-based panel, Figure 2 shows a schematic cross-sectional view of a suction device of the wood-based panel manufacturing device according to Figure 1 and Figure 3, in sub-figures a, b and c, each shows a schematic cross-section through a wood-based panel produced according to the invention.

[0057] Figure 1schematically shows a wood-based panel manufacturing device 10, which has 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.i, into a raw wood-based panel 16. The at least one pre-product layer 14 is produced by a spreading device 18.

[0058] In the present case, the spreading device 18 comprises a first spreader 20.1 for spreading a first precursor layer 14.1 in the form of a first cover chip layer, a second spreader 20.2 for spreading a second precursor layer 14.2 in the form of a middle chip layer and a third spreader 20.3 for spreading a third precursor layer 14.3 in the form of a second cover chip layer.

[0059] After pressing by means of the press 12, the resulting raw wood-based panel 16 has a first cover layer 22.1, a middle layer 22.2 and a second cover layer 22.3.

[0060] The press 12 is heated, for example, by means of a thermal fluid 24 flowing through heating tubes 26.1, 26.2, ... The heat of the thermal fluid 24 is transferred to a rotating press belt 28, which is pressed onto the pre-product layers 14.i by means of pressure rollers 30.1, 30.2, ...

[0061] In a material flow direction M behind the press 12, a liquid application device 32 is arranged, by means of which a flame retardant-containing liquid 34 can be applied to a first side surface S1 of the raw wood-based panel 16.

[0062] In addition, a suction device 36 is arranged behind the press 12 in the material flow direction M, by means of which liquid 34, which has been applied to the first side surface S1, is sucked into the raw wood-based panel 16.

[0063] 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 under a liquid pressure p 34. The nozzle 41 generates a spray 42 that deposits on the first side surface S1. The nozzle 41 can be part of a nozzle bar 43 having three or more nozzles.

[0064] The liquid application device 32 may have a temperature control device 43 which keeps the liquid 34 at a predetermined temperature T 34.

[0065] Figure 2 shows an enlarged view of the suction device 36, which has a vacuum table 37 with a circumferential seal 44, by means of which the second side surface S2 is sealed against a suction chamber 46. The suction device 36 has supports 48.j , (j = 1, 2, ...) that support the raw wood-based panel 16.

[0066] The suction chamber 46 is connected to a vacuum pump 52 via a vacuum line 49. Preferably, a pressure p 46 in the suction chamber 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 ventilated, 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 ventilated again.

[0067] The liquid application device 32 may alternatively or in addition to the nozzle 41, for example, comprise an application roller 52 or another device for applying the liquid 34 to the first side surface S1.

[0068] Figure 3ashows schematically a cross section through a wood-based panel 54, which has a first edge surface K1 and a second edge surface K2.

[0069] In Figure 3b The graph shows the concentration c F,54 of flame retardant in the wood-based panel 54 as a function of the distance z from the nearest side surface. It can be seen that the concentration is greatest at the surface. With increasing distance z from the first side surface S1 of the wood-based panel 54, the concentration decreases down to the center of the wood-based panel 54.

[0070] In an inner thickness quintile Q3, the wood-based panel 54 has an internal flame retardant concentration c F,Q3 . In a first outermost thickness quintile Q1, the wood-based panel 54 has a first external flame retardant concentration c F,Q1 . In a second outermost thickness quintile Q5, the wood-based panel 54 has a second external flame retardant concentration c F,Q5 .

[0071] It can be seen that the outdoor concentration is significantly higher than the indoor concentration. In this case, c F,Q3 = 0.25 · c F,Q1 .

[0072] Figure 3c 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 extension, which lies adjacent to the first, outermost thickness decile in the direction of a center of the thickness extension, is at least 0.1 times a first-decile concentration c F,D1 in the first outermost thickness decile. Example 1:

[0073] An unsanded raw wood-based panel 16 in the form of an OSB board 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 binder (PMDI: polymeric diphenylmethane diisocyanate) in the cover layers 22.1, 22.3 compared to a non-flame-retardant wood-based panel, was sprayed with a solution of a flame retardant Ecoaphos MK 68, 60 wt% from Ecoatech in an amount of 0.49 kg / m² using a nozzle bar.

[0074] This corresponds to a quantity of 15 percent by weight based on the specific weight per unit area of the facing layers 22.1, 22.3. The facing layer thickness of the facing layers is d 22.1 = d 22.3 = 3 mm ± 1 mm. A negative pressure of 300 mbar was applied from the underside. Within t suction = 120 s ± 15 s, the liquid 34, i.e., the flame retardant solution, had completely penetrated the raw wood-based panel 16.

[0075] The raw wood-based panel 16 was rotated, and the process was repeated. The raw wood-based panel 16 (base area: DIN A4, sample 1) was then created from the panel, and this panel was tested against a conventionally produced flame-resistant OSB board. The conventionally produced flame-resistant OSB board had a comparable amount of the aforementioned flame retardant in the surface layer and had been conditioned prior to testing (humidity: approximately 9%). The samples were exposed to flames for different lengths of time using a gas burner positioned at a defined distance from the surface. After the flame exposure time, it was noted whether burning / continued burning was observed, and the duration of the continued burning was determined. Example 2:

[0076] An unsanded raw wood-based panel 16 in the form of an OSB board with a thickness d = 20 mm (raw density approx. 650 kg / m 3 ) was placed on the vacuum table 37, which was provided 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 sprayed with a solution of a flame retardant from Ecoatech (Ecoaphos MK 68, 60 wt.%) in a quantity of 0.49 kg / m 2 using the nozzle bar 43. The flame retardant solution had previously been heated to approximately T 34 = 60°C to facilitate penetration.

[0077] The liquid was applied in an amount corresponding to 15 wt% based on the top layer strands (top layer thickness approximately 3 mm per side). A vacuum of 150 mbar was applied from the underside. After a suction time of t suction = 90 seconds, the flame retardant solution had completely penetrated the raw wood-based panel 16. The raw wood-based panel 16 was rotated, and the process was repeated.

[0078] 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 board.

[0079] The conventionally produced OSB board had a comparable amount of the above-mentioned flame retardant in the top layer and had been air-conditioned before testing (humidity: approx. 9%).

[0080] During the flammability test, the samples were exposed to a flame using a gas burner positioned at a defined distance from the surface for varying lengths of time, as shown in the left column of the following table. After the flame exposure time, the observation of whether burning / continued burning and the duration of continued burning were recorded. Table 1: Observations after flame exposure Flame exposure time reference Sample 1 Sample 2 (OSB conventionally manufactured) 2 minutes no further burning no further burning no further burning 4 minutes no further burning no further burning no further burning 8 minutes no further burning no further burning no further burning 12 minutes no further burning no further burning no further burning 15 minutes no further burning no further burning no further burning

[0081] As can be seen from the flame exposure tests, the wood-based panels produced using the inventive method behaved just as well as the reference panel. Even after 15 minutes of flame exposure, no sample continued to burn after the burner was turned off. Subsequent testing showed that the wood-based panels produced using the inventive method still possessed significantly higher strength after the test. In the reference panel, individual charred strands could be easily mechanically removed from the structure, which was only possible with greater force in the two wood-based panels produced using the inventive method. Example 3:

[0082] An unsanded raw wood-based panel 16 in the form of an HDF board with a thickness d = 8 mm (raw density approx. 850 kg / m³) was placed on the vacuum table 37, which was provided with the circumferential seal 44. The raw wood-based panel 16, which had been produced with a 1% binder based on a urea-formaldehyde glue, was sprayed with a solution of a flame retardant from Ecoatech (Ecoaphos MK 68, 50 wt%) in a quantity of 0.31 kg / m³ using the nozzle bar 43. The binder content of this panel was also increased (2% more than the standard). The flame retardant solution had previously been heated to approximately T 34 = 60°C to facilitate penetration.

[0083] Using the liquid, a quantity of flame retardant was introduced into the wood-based panel, amounting to 15 percent by weight based on the top layer (thickness of the top layer approximately 1.2 mm per side). A vacuum of 150 mbar was applied from the underside. After a suction time of t suction = 120 seconds, the flame retardant solution had completely penetrated the raw wood-based panel 16. The raw wood-based panel 16 was rotated, and the process was repeated.

[0084] 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 using a conventionally produced, flame-retardant HDF.

[0085] The conventionally produced wood-based panel had a comparable amount of the above-mentioned flame retardant in the panel and had been air-conditioned before testing (humidity: approx. 9%).

[0086] The samples were tested for flammability in the same way as the OSB. The results for flammability and strength after the fire test were comparable to those for the OSB. Example 4:

[0087] The steps carried out for the embodiment 3 were carried out for an unsanded raw wood-based panel 16 in the form of an MDF panel with a thickness d = 8 mm (raw density approx. 750 kg / m 3< ).

[0088] In the flammability test, the samples were tested in the same way as a conventionally manufactured MDF board. The MDF board produced according to the invention achieved or exceeded the flammability and strength results compared to the conventionally manufactured MDF board. Example 5:

[0089] The steps carried out for the embodiment 3 were carried out for an unsanded raw wood-based panel 16 in the form of a chipboard with a thickness d = 8 mm (raw density approx. 650 kg / m 3< ).

[0090] In the flammability test, the samples were tested in the same way as a conventionally manufactured particleboard. The particleboard produced according to the invention achieved or exceeded the flammability and strength results compared to the conventionally manufactured particleboard. Example 6:

[0091] The steps carried out for the embodiment 3 were carried out for an unsanded raw wood-based panel 16 in the form of an insulation panel with a thickness d = 20 mm (raw density approx. 250 kg / m 3< ).

[0092] In the flammability test, the samples were tested in the same way as a conventionally manufactured insulation board. The insulation board produced according to the invention achieved or exceeded the flammability and strength results of the conventionally manufactured insulation board. List of reference symbols

[0093] 10 Wood-based panel manufacturing device c F,D1 First decile concentration c F,D2 Second decile concentration 12 press c F,Q1 first external concentration 14 Pre-product position c F,Q3 Internal concentration s14.1 first top layer of chipboard c F,Q5 second external concentration 14.2 Middle chip layer d thickness 14.3 second top layer of chipboard D Fat decile 16 Raw wood-based panel D1 first extreme fat decile 18 Spreading device D10 second extreme fat decile 20 Spreader i Running index of the intermediate product layers 22.1 first top layer j Running index of the supports 22.2 middle class K edge surface 22.3 second top layer M Material flow direction 24 Thermofluid S1 first side surface 26 heating pipe S2 second side surface 28 Press belt Q Thickness quintile 30 pressure roller Q1 first outermost thickness quintile 32 Liquid application device Q3 Inner thickness quintile 34 liquid Q5 second outermost thickness quintile 36 suction device 37 Vacuum table t suction Suction time 38 liquid reservoir T temperature 40 pump z Distance from the surface of the wood-based panel 41 nozzle 42 spray mist 43 nozzle bar 44 seal 46 Suction chamber 48 support 49 vacuum line 50 peripheral zone 52 Application roller 54 Wood-based panel c F Flame retardant content

Claims

1. A method for producing a wood-based panel (54), comprising the steps of: (a) producing a raw wood-based panel (16) having a first side surface (S1), a second side surface (S2) running parallel to the first side surface (S1), and edge surfaces connecting the side surfaces (S1, S2) to one another, (b) applying a liquid (34) containing a flame retardant at least to the first side surface (S1), and (c) applying a negative pressure to the second side surface (S2) such that the liquid (34) containing a flame retardant is sucked into an edge zone (50) of the raw wood-based panel (16), thereby producing the wood-based panel (54) characterized in that(d) the liquid (34) is an aqueous solution or a suspension, (e) a concentration of flame retardant in the liquid (34) corresponds to at least half the solubility of the flame retardant and (f) the flame retardant comprises phosphonate and / or a guanidine salt and / or is a flame retardant based on aluminum hydroxide or alkali sulfates.

2. Method according to claim 1, characterized in that the area-specific application quantity of liquid (34) is selected such that a top layer moisture content of a top layer of the wood-based panel (54) deviates by a maximum of 30% from a core moisture content.

3. Method according to one of the preceding claims, characterized in that the negative pressure is applied in such a way that an internal concentration (c F,Q3 ) of flame retardant in an inner thickness quintile (Q3) of a thickness extension from the first side surface (S1) to the second side surface (S2) not more than 0.8 times an external concentration (c F,Q1) in a first outermost thickness quintile (D1) extending to the first side surface (S1).

4. Method according to one of the preceding claims, characterized in that the application of the liquid (34) is carried out in such a way that the edge zone (50) of at least 90% of a side surface area of the wood-based panel (54) contains flame retardant.

5. Method according to one of the preceding claims, characterized in that the application of the liquid (34) comprises spraying, applying, pouring and / or flooding.

6. Method according to one of the preceding claims, characterized in that a concentration of flame retardant in the liquid (34) is at least 50 percent by weight.

7. Method according to one of the preceding claims, characterized in that the liquid (34) contains at least one dye which is selected such that a flame retardant content can be determined from a colour of the wood-based panel (54) in a cross-section.

8. Method according to one of the preceding claims, characterized in that (a) a liquid temperature of the liquid (34) when applied to the side surface is at least 40°C, in particular at least 50°C, and / or (b) a surface temperature of the first side surface (S1) when applying the liquid (34) is at most 50°C.

9. Method according to one of the preceding claims, characterized in that an area-specific application rate of liquid (34) is at least 0.3 kilograms per square meter and / or at most 5 kilograms per square meter.

10. Method according to one of the preceding claims, characterized in that the negative pressure is at least 300 hPa.

11. Method according to one of the preceding claims, characterized bythe steps (a) after introducing the liquid (34) into the edge zone (50) of the first side surface (S1), rotating the raw wood-based panel (16), (b) applying the liquid (34) to the second side surface (S2) and (c) applying a negative pressure to the first side surface (S1) so that the liquid (34) is sucked into an edge zone (50) of the second side surface (S2) of the raw wood-based panel (16), so that the wood-based panel (54) is produced.

12. Method according to one of the preceding claims, characterized bythe steps: (a) spreading a first cover chip layer (14.1), (b) spreading at least one middle chip layer (14.2) arranged thereon, and (c) spreading a second cover chip layer (14.3) arranged on the middle chip layer, (d) pressing the layers to form the raw wood-based panel (16), which has - a first cover layer (22.1) which has been produced from the first cover chip layer (14.1), - a middle layer (22.2) which has been produced from the middle chip layer (14.2), and - a second cover layer (22.3) which has been produced from the second cover chip layer (14.3), (e) applying the liquid (34) containing the flame retardant with a surface-specific application quantity of liquid (34) which corresponds to at least 10 percent by weight of a surface-specific mass of the first cover layer (22.1).

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