Process for producing a material plate

Abstract

Shown and described is a method for producing a material board, in particular a wood-based board, from a material according to patent claim 1.

Description

[0001] The invention relates to a method for producing a material board, in particular a wood-based panel, from a material, comprising the following steps: a) providing at least one layer of a material, in particular a material containing wood chips and / or wood fibers, b) providing a press, comprising: an upper pressing device and a lower pressing device, between which a gap is formed to receive the material, wherein the upper pressing device and / or the lower pressing device has hydraulic pressing cylinders that can change the gap width between the upper pressing device and the lower pressing device and can transmit pressing forces to the material, and wherein the upper pressing device and / or the lower pressing device has a heating device, in particular a heating plate, that can at least indirectly transfer heat to the material,c) pressing the material in the gap between the upper pressing device and the lower pressing device, d) heating the material in the gap between the upper pressing device and the lower pressing device, wherein steps c) and d) take place at least partially simultaneously.

[0002] Material boards, especially wood-based panels, are known in various designs and have a wide range of uses – for example, in the construction of furniture. Wood-based panels are produced by joining shredded wood materials, with the size and shape of the wood particles determining the properties of the wood material and the resulting wood-based panels. The wood materials can be, for example, wood chips (fine chips and / or coarse chips) or wood fibers. Accordingly, the material boards made from these wood materials can also be classified as particleboard, particleboard ("OSB board"), medium-density fiberboard ("MDF board"), or high-density fiberboard ("HDF board").

[0003] The joining of the shredded wood materials usually takes place under the influence of pressure and / or temperature, which is why presses are often used in the manufacturing process. The bonding of the chips or fibers achieved during production is partly based on properties inherent in the chips or fibers (e.g., the properties of lignins, the natural "glue" in wood). In addition, the bonding between the chips or fibers can be achieved or enhanced by a binder added to the wood materials. However, for cost reasons and for health protection reasons (e.g., reduction of harmful fumes), the general aim is to minimize the use of binders.

[0004] In addition to the wood-based materials used, manufacturing processes can also be differentiated based on other criteria, such as the moisture content of the wood-based materials being processed. Accordingly, a distinction is made between dry-process and wet-process processes. In the DIN EN 316 standard, a wet-process board is defined as a "fiberboard with a moisture content of more than 20% at the board-forming stage," while a dry-process board is defined as a "fiberboard with a moisture content of less than 20% at the board-forming stage."

[0005] Moisture content (often referred to as "wood moisture content" or "wood moisture content") is a quantity defined as the ratio of the water mass contained in the wood to the dry mass of the wood, expressed as a percentage. It is to be distinguished from the water content of the wood, which represents the ratio of the water mass contained in the wood to the total mass of the (moist) wood, expressed as a percentage. Moisture content is expressed as a percentage (%) ATRO (absolutely dry).

[0006] In practice, the dry process is often carried out with moisture contents of 10% and below, while the wet process is often carried out with moisture contents significantly higher than 20%, for example, around 100% (due to the previously mentioned definition of ATRO moisture content, values ​​above 100% are also possible). However, the initial moisture content is significantly reduced in the wet process by mechanically pressing out the moisture in the first step and then evaporating it. Therefore, in the wet process, a mesh screen is arranged on the underside of the chipboard or fiber mat. This facilitates drainage and steam escape, but often leaves an undesirable grid-like imprint on the underside of the board.

[0007] While the wet process often eliminates the need for binding agents such as glue, the dry process typically uses binding agents. Therefore, the challenge of reducing the use of binding agents is particularly important in dry processes.

[0008] Against this background, the object of the invention is to provide a method for producing a material board, in particular a wood-based board, with which boards with good mechanical and optical properties can be produced even if binders are partially or completely omitted.

[0009] This object is achieved in a method according to the preamble of patent claim 1 in that during step d) the temperature (T) in the material is increased to at least 130°C, in particular at least 150°C, preferably at least 180°C.

[0010] The method is a method for producing a material board, in particular a wood-based panel, from a material. The method initially comprises step a), the provision of at least one layer of a material, in particular a material containing wood chips and / or wood fibers. The provision of the (wood) material can be carried out in different ways. For example, if it is a dry, free-flowing material, the (wood) material can be scattered in one or more layers onto a conveyor belt in order to be fed to a press (usually in dry processes). Alternatively to scattering, the material can also be placed on a conveyor belt, for example in the form of a pulp (usually in wet processes). The method additionally comprises step b), the provision of a press.The press can, for example, be a continuously operating press or an intermittently operating press. In the case of intermittently operating presses, presses with one "stage" or with multiple "stages" can be used. The press used in the process initially comprises an upper pressing device and a lower pressing device, between which a gap is formed to hold the material. In the gap ("press gap"), the material can be processed into a plate under the influence of pressure and / or heat. The upper pressing device and / or the lower pressing device have hydraulic pressing cylinders that can change the gap width between the upper pressing device and the lower pressing device (i.e., reduce or increase it) and can transfer pressing forces to the material. In practice, it has proven advantageous to assign the hydraulic pressing cylinders to the upper pressing device.The upper pressing device and / or the lower pressing device additionally has (at least) one heating device, in particular (at least) one heating plate, which can transfer heat directly or indirectly to the material. Preferably, both the upper pressing device and the lower pressing device have a heating plate so that the material can be heated from the top and from the bottom. The method further comprises step c), pressing the material in the gap between the upper pressing device and the lower pressing device and step d), heating the material in the gap between the upper pressing device and the lower pressing device. Steps c) and d) can partially or completely overlap, i.e. take place at least partially simultaneously.

[0011] According to the invention, during step d), the temperature (T) in the material is increased to at least 130°C, in particular at least 150°C, preferably at least 180°C. Due to the unusually high temperatures in the center of the board—significantly above 100°C—for the production of wood-based panels, the natural constituents of the wood (e.g., lignin, starch, sugar) can be activated and utilized particularly effectively. Passing through a high-temperature phase can therefore make a significant contribution to improving the mechanical properties of the panels to be produced.

[0012] One embodiment of the method provides that during step d), the temperature in the material increases strictly monotonically for at least 20 seconds, in particular for at least 30 seconds. By continuously increasing the temperature over a minimum period during step d) – i.e., while the material is being heated – the thermal and / or chemical processes occurring in the material can proceed without interruption, thus reliably achieving the desired results.

[0013] According to a further embodiment of the method, the temperature in the material is 150°C or more, in particular 180°C or more, for at least 10 seconds, in particular for at least 20 seconds. By maintaining a minimum duration for the high-temperature phase, it is ensured that the thermal and / or chemical processes occurring in the material can proceed as completely as possible.

[0014] According to a further embodiment of the method, during step c) the contact pressure acting on the material is reduced, whereby the contact pressure is reduced by at least 50 N / cm 2 , in particular by at least 100 N / cm 2 , preferably by at least 200 N / cm 2 The pressure reduction should take place "during step c), i.e. during the pressing process. A distinction must be made between the (specific) pressure acting on the material (unit used here: N / cm 2 ) and the hydraulic pressure prevailing in the press cylinders (unit used here: bar). The beginning and end of the pressing process can be defined in relation to both of the pressures mentioned: The pressing process begins at a point in time at which the specific pressure acting on the material first increases measurably and / or reaches a value of 1 N / cm 2The pressing process ends at a point in time when the specific pressure acting on the material reaches a value of 1N / cm 2 falls below and / or below the measurable limit. Alternatively and / or additionally, the pressing process begins at a point in time at which the pressure in the pressing cylinders first increases measurably and / or exceeds a value of 1 bar. The pressing process ends at a point in time at which the pressure in the pressing cylinders falls below a value of 1 bar.

[0015] Since the pressure reduction occurs during this pressing process, it differs from a (complete) pressure reduction, which typically occurs at the end or after the end of the pressing process by fully opening the press. The contact pressure acting on the material can be reduced, for example, by reducing the pressure in the press cylinders. Due to the different effective areas, the contact pressure can differ quantitatively from the pressure in the press cylinders by a system-specific factor.

[0016] The pressure reduction takes place actively and is achieved by opening the press gap, allowing the compressed material to expand slightly and thus be geometrically relieved. This pressure reduction also differs from the naturally occurring pressure drop during the pressing of wood-based materials. This well-known pressure drop occurs over the course of the pressing process, while the distance of the press gap is kept essentially constant. The material plasticizes due to the existing moisture and temperature, so that the counterpressure that the compressed material exerts against the press decreases. In fact, the restoring forces of the material still present at the time of the active pressure reduction can be used (in particular before the plasticization of the material described above, or before the curing of anyused binders) to allow the material to breathe and thus enlarge the existing pores between the particles.

[0017] During the geometric release period, the moisture flows out of the material very quickly as steam through the now open pores. This causes the gas phase (steam-air mixture) to expand. The escape of steam allows any remaining liquid water to evaporate. Both effects (expansion of the gas phase and evaporation of water) extract energy from the environment, which immediately leads to rapid cooling inside the material sheet. In addition, drying occurs quickly, so that only a small amount of residual moisture remains in the sheet at the end of the pressing process. With conventional processes, the material evaporates slowly over the entire pressing process and, if necessary, a controlled, slow release of pressure (and thus slow cooling) only takes place at the end of the pressing process to prevent the sheet, which is still quite soft during this phase, from cracking.However, it has been recognized that rapid steam release is also possible without damaging the board if it occurs at an early stage of the pressing process, i.e., if the pressing process continues during and after the strong steam release (at reduced pressure), and the board is thus still "held in shape" by the press during the steam release. In this way, the board can be "stabilized" to such an extent that significantly less binder can be used, or even omitted altogether.

[0018] Essentially, pressure and gap width are two variables that can be directly related and mutually influence each other during a pressing process. A change in one of these two variables can therefore also change the other. For example, if a "pressure reduction" occurs, this can be accompanied by a geometric opening of the press gap (= increase in the gap width); regardless of whether this process is pressure-controlled or distance-controlled.

[0019] According to one embodiment of the method, during step c) the contact pressure acting on the material is reduced at a rate of at least 100 N / cm 2 s, in particular at least 200 N / cm 2s occurs. According to this design, during step c) – i.e., during the pressing process – a rapid reduction in the contact pressure acting on the material occurs. The minimum pressure reduction rates to be maintained here ensure very rapid cooling and drying, which, on the one hand, triggers the previously described processes and, on the other hand, can reduce the process duration and thus increase productivity.

[0020] According to a further embodiment of the method, during step c), the pressure of the press cylinders is reduced from a working pressure to a holding pressure, wherein the pressure of the press cylinders is reduced by at least 15 bar, in particular by at least 30 bar, preferably by at least 60 bar. As already explained above, the contact pressure acting on the material can be reduced, for example, by correspondingly reducing the pressure prevailing in the press cylinders, thereby achieving the same effects described above.

[0021] In a further embodiment, the method provides that during step c), the pressure of the press cylinders is reduced at a rate of at least 10 bar / s, in particular at least 15 bar / s. The aforementioned rapid reduction of the contact pressure acting on the material can be achieved, for example, by a correspondingly rapid reduction of the pressure in the press cylinders.

[0022] According to a further embodiment of the method, during step c) the gap width is increased to a range between +2% and +20%, in particular between +4% and +15% of the gap width. The gap width can increase during step c) - i.e. during the pressing process - because the contact pressure acting on the material is reduced. The reduced pressure and the increased gap width mean that the compressed material can expand again somewhat. Since the increase in the gap width is limited, contact between the material and the two pressing devices - i.e. the upper and lower pressing devices - is maintained even with an increased gap width, so that the pressing process can be continued or does not have to be interrupted.

[0023] A further embodiment of the method provides that during step c) the temperature in the material is reduced by at least 20°C, in particular at least 30°C, preferably at least 40°C. The temperature in the material is measured in the middle of the plate, i.e. for a plate thickness of 10 mm it is measured at a "height" of 5 mm. This can be done, for example, by a measuring wire inserted into the material for testing purposes. Because the material is significantly cooled and dried by the escape of steam in step c) - i.e. during the pressing process - the time required after completion of the pressing process to further reduce the temperature and dry the material is shortened.

[0024] In a further embodiment of the method, during step c), the temperature in the material is reduced at a rate of at least 10°C / s, in particular at least 20°C / s, preferably at least 30°C / s. According to this embodiment, during step c)—i.e., during the pressing process—a rapid reduction in the material temperature is achieved. The minimum cooling rates to be observed here ensure that the process duration can be reduced, thus increasing productivity.

[0025] A further embodiment of the method provides that the contact pressure acting on the material during step c) is reduced to a contact pressure in the range between 10 N / cm 2 and 150 N / cm 2 , especially between 30 N / cm 2 and 100 N / cm 2According to this design of the process, the contact pressure during step c) – i.e., during the pressing process – is not completely eliminated (i.e., reduced to ambient pressure), but rather reduced from a higher pressure level ("working level") to a lower pressure level ("holding level") and maintained there for a while. Thus, pressure relief should already take place before the glue sets.

[0026] According to one embodiment of the method, the pressure of the press cylinders is reduced during step c) from a working pressure to a holding pressure in the range between 5 bar and 40 bar, in particular between 10 bar and 30 bar. The previously described reduction of the contact pressure acting on the material during the pressing process from a "working level" to a "holding level" can be achieved, for example, by lowering and maintaining the pressure of the press cylinders accordingly.

[0027] In a further embodiment of the method, the reduced contact pressure and / or the reduced holding pressure are maintained for at least 10 seconds, in particular at least 20 seconds. By maintaining the "holding level" for a sufficiently long time, it is ensured that the still quite soft, unstable material plate is "held in shape" and thus stabilized for a sufficient time before the pressing process is terminated and the material plate is released from the opening press.

[0028] According to a further embodiment of the method, the temperature is reduced from a maximum temperature to a holding temperature in the range between 120°C and 220°C, in particular between 140°C and 180°C. As already described above with regard to printing, the temperature in the center of the plate should not initially be completely reduced (i.e., to ambient temperature), but rather reduced from a higher temperature level ("working level") to a lower temperature level ("holding level") and maintained there for a while.

[0029] In a further embodiment of the process, the holding temperature is maintained for at least 10 seconds, in particular at least 20 seconds. This ensures that the thermal and / or chemical processes occurring in the material can proceed as completely as possible.

[0030] With regard to the press used in the method, it is proposed that in step b) an intermittently operating press be provided, wherein the upper pressing device is formed by several pressing cylinders and an upper heating plate, and wherein the lower pressing device is formed by a lower heating plate. An intermittently operating press is understood to mean a press in which the material to be processed is not moved continuously, but is moved intermittently (i.e., is temporarily stationary). The intermittently operating press is first opened in order to insert the material to be pressed into the press. The press is then closed in order to press the material. The press is then opened again in order to remove the plate just produced from the press. The material for the next plate to be produced can then be inserted into the press, and the aforementioned steps are repeated.Cyclically operating presses can be used with one or more stages. An example of a cyclically operating press is shown in . Fig. 2 and is used in connection with Fig. 2 described.

[0031] With regard to the press used in the method, it is alternatively proposed that in step b) a continuously operating press is provided, wherein the upper pressing device is formed by a plurality of press cylinders, an upper heating plate, an upper steel belt and upper roller bars, wherein the lower pressing device is formed by a lower heating plate, a plurality of pressure distribution plates, a lower steel belt and lower roller bars, wherein the steel belts are mounted so as to rotate around rollers in such a way that the gap for receiving the material is formed between the steel belts, and wherein the roller bars are mounted so as to rotate around rollers in such a way that they are arranged between the steel belts and the heating plates and enable a relative movement between the steel belts and the heating plates.A continuously operating press is one in which the material being processed is continuously moved, meaning it never stops during any process step—not even during pressing. A continuously operating press is described, for example, in . Fig. 1 and is used in connection with Fig. 1 described.

[0032] According to a further embodiment of the method, in step a) the wood-based material is provided in multi-layer form, in particular in 3-layer, 5-layer or 7-layer form, in particular with at least one middle layer, at least one lower cover layer and at least one upper cover layer. The different layers or plies of the material can differ, for example, in the ingredients (chips, fibers), the size of the ingredients (small chips, large chips), the density and / or the moisture content. In this way, the mechanical properties of the board to be produced can be optimized. For example, it can be provided that the middle layer (less relevant for bending strength) is made less dense and thus "lighter" by using coarser chips than the cover layers (more relevant for bending strength), which are made denser by using finer chips.It can also be provided that the moisture content of the outer layers (i.e. the surfaces) is greater than the moisture content of the middle layer.

[0033] According to a further embodiment of the process, in step a), a wood-based material with a moisture content in the range between 2% and 40%, in particular between 5% and 30%, particularly preferably between 10% and 25%, is provided. Optimal results have been achieved with a moisture content within the stated limits.

[0034] According to a further embodiment of the process, it is provided that in step a) a wood-based material with a binder content of less than 15%, in particular less than 10%, preferably in the range between 0% and 6%, is provided. This process makes it possible to produce wood-based panels with a very low binder content (“low-glue” panels) or even free of binders (0% binder content: “glueless” panels). This is possible through the combination of several measures, in particular the use of high temperatures (utilizing the properties of lignins, the natural “adhesives” in wood), as well as rapid cooling and stabilizing holding pressure. For this embodiment, it is further proposed that glue and / or bio-glue be used as the binder. Glues and bio-glues are very proven and high-performance binders for wood-based materials.

[0035] A further embodiment of the process provides that, in step a), fine wood chips are provided for the production of flat-pressed boards and / or long chips for the production of coarse particle boards or OSB boards. By selecting the type of chips and their length, the type of board to be produced and its mechanical properties can be determined.

[0036] According to a further embodiment of the method, it is provided that in step a) wood fibers for the production of wood fiber boards, for example medium-density wood fiber boards (MDF) or high-density wood fiber boards (HDF) are provided, wherein the produced wood fiber boards preferably have smooth surfaces on both sides. The type of board to be produced and its mechanical properties can also be determined by the selection of the type of fibers and their length. The wood fiber boards produced in this way differ from wood fiber boards produced using a wet process in that they have smooth surfaces on both sides, since such wood fiber boards do not have smooth surfaces but rather have a grid-like imprint caused by the screen mesh.

[0037] The invention is explained in more detail below with reference to a drawing which merely represents a preferred embodiment. The drawing shows: Fig. 1: a continuously operating press known from the prior art for producing a wood-based panel for carrying out the method according to the invention, Fig. 2: a cyclically operating press known from the prior art for producing a wood-based panel for carrying out the method according to the invention, and Fig. 3: a diagram with the parameters of the method according to the invention.

[0038] Fig. Figure 1 shows a continuously operating press 1 known from the prior art for producing a wood-based panel for carrying out the method according to the invention. The press 1 is a continuously operating press which has two endlessly circulating steel belts 2, namely an upper steel belt 2A and a lower steel belt 2B. The steel belts 2 are guided around several rollers 3, of which at least one roller 3A per steel belt 2 has a drive 4 (e.g. an electric motor) to drive the rollers 3 and the steel belts 2 (the direction of movement of the steel belts 2 is Fig. 1 marked with arrows). The steel belts 2 are arranged in such a way that a gap 5 is formed between the upper steel belt 2A and the lower steel belt 2B, which gap extends from the inlet 6 of the press 1 to the outlet 7 of the press 1. The gap 5 has a variable gap width 8 and serves to receive the wood material to be processed and to guide it along a transport direction TR through the press 1. The gap 5 can be divided along the transport direction TR into a narrowing section (“inlet” of the press, gap width 8 decreases), a parallel section (gap width 8 remains approximately constant) and a widening section (“outlet” of the press, gap width 8 increases).

[0039] The press 1 has several vertically extending frame elements 9, which are connected to one another via stiffening beams 10 running along the transport direction TR. The frame elements 9 have recesses 11 through which the steel belts 2 can be guided. The press 1 also has several hydraulic press cylinders 12 in its upper area, which can transmit pressing forces to the material via the steel belts 2. The press cylinders 12 are mounted on the frame elements 9, for example in the recesses 11 of the frame elements 9. Numerous press cylinders 12 are provided along the transport direction TR, whereby the pressure can be adjusted very precisely - and differently along the transport direction TR. In addition, it can be provided that several press cylinders 12 are arranged next to one another (in Fig. 1 concealed) are arranged to achieve an even pressure distribution in the transverse direction. Fig. In the press 1 shown in Figure 1, only press cylinders 12 are arranged above the gap 5; below the gap 5, however, pressure distribution plates 13 are provided, which are also mounted on the frame elements 9, for example in the recesses 11 of the frame elements 9. The pressure distribution plates 13 can achieve a uniform pressure distribution and prevent the pressure in the area of ​​the frame elements 9 from being significantly higher than between the frame elements 9.

[0040] In addition, the press 1 has heating plates 14, namely an upper heating plate 14A and a lower heating plate 14B. The upper heating plate 14A is arranged above the gap 5 (e.g., below the press cylinders 12) and the lower heating plate 14B is arranged below the gap 5 (e.g., above the pressure distribution plates 13). The heating plates 14 preferably have numerous (in Fig. 1 not shown) so that the heating plates 14 can be flowed through by a heating or cooling medium (e.g. oil) in order to set the desired temperature. The heating plates 14 also have sufficient flexibility so that the width of the gap 5 can be variably adjusted along the transport direction TR by the press cylinders 12 (slightly) elastically deforming the heating plates 14. Roller bars 15 are arranged between the steel belts 2 and the heating plates 14, which are connected to one another and form an endless “roller bar carpet” circulating around rollers 16. The roller bars 15 can be divided into upper roller bars 15A and lower roller bars 15B, with the upper roller bars 15A being arranged above the gap 5 and within the upper steel belt 2A and the lower roller bars 15B being arranged below the gap 5 and within the lower steel belt 2B.The roller rods 15, like a needle bearing, allow low-friction relative movement between the steel belts 2 (moving in the transport direction TR) and the heating plates 14 (not moving in the transport direction TR) and the associated components (e.g., the press cylinders 12 or the pressure distribution plates 13). Preferably, the roller rods 15 roll without a drive between the steel belts 2 and the heating plates 14 while transferring the pressing pressure and heat energy.

[0041] In the area of ​​the inlet 6, the press 1 has several inlet rollers 17 which are adjustable and can act on the steel belts 2 in order to change the geometry of the inlet 6 and adapt it to different applications. Fig. As shown in Figure 1, frame elements 9 with press cylinders 12 can optionally also be arranged in the area of ​​the inlet 6 of the press 1. A continuously operating press is known, for example, from DE 10 2017 110 882 B4.

[0042] The Fig. The press 1 shown in Figure 1 comprises an upper pressing device 1A and a lower pressing device 1B, which are separated from each other by the gap 5 but are nevertheless connected to each other by the frame elements 9. The upper pressing device 1A comprises the upper steel belt 2A, the upper roller bars 15A, the upper heating plate 14A, and the pressing cylinders 12. The lower pressing device 1B comprises the lower steel belt 2B, the lower roller bars 15B, the lower heating plate 14B, and the pressure distribution plates 13.

[0043] Fig. Figure 2 shows a prior art cyclically operating press 1' for producing a wood-based panel for carrying out the method according to the invention. The features of the press which have already been described in connection with Fig. 1 are described in Fig. 2 with corresponding reference numerals. The essential difference to the Fig. 1 is that the material to be processed by the press in the case of the cyclically operating press 1' consists of Fig. 2 is not moved during the pressing process, but remains at rest. Therefore, the press 1' Fig. 2 also has no rotating steel belts 2 and no rotating roller bars 15. Nevertheless, even with a cyclically operating press 1', it has proven advantageous to introduce the material from one side (inlet 6) into the gap 5 of the press 1' and - after the pressing process has been completed - to remove the produced material plate from the gap 5 of the press 1' from the opposite side (outlet 7). This also results in a (preferred, although not mandatory) "transport direction" TR with the cyclically operating press 1'.

[0044] Since neither steel bands 2 nor rolling bars 15 are present, the Fig. 2, during the pressing process, there is direct contact between the two heating plates 14 (i.e., the upper heating plate 14A and the lower heating plate 14B) and the material to be processed. As with the press 1 in Fig. 1 will also be at the press 1' in Fig. 2 the pressing forces are generated by press cylinders 12, which can also cause a change in the gap width 8. The press 1' from Fig. 2 also has several vertically extending frame elements 9, which are connected to one another via stiffening beams 10. The frame elements 9 have recesses 11, which serve, for example, to guide the two heating plates 14 through the frame elements 9. A cyclically operating press is known, for example, from DE 20 2012 104 004 U1.

[0045] The Fig. The press 1' shown in Figure 2 also has an upper pressing device 1A' and a lower pressing device 1B', which are separated from each other by the gap 5, but are nevertheless connected to each other by the frame elements 9. The upper pressing device 1A' comprises the upper heating plate 14A and the pressing cylinders 12. The lower pressing device 1B' comprises the lower heating plate 14B.

[0046] Fig. Figure 3 shows a diagram with selected parameters of the method according to the invention. The method can be implemented, for example, on the Fig. 1 shown press 1 or on the in Fig. 2. On the first (horizontal) axis, Fig. 3 shows the time t (unit: minutes, seconds). On the second (vertical) axis, Fig. 3 shows several parameters: First, the second axis shows the temperature T (unit: °C), which is the temperature T in the material (in the center of the material plate). The temperature T can be measured, for example, by wires that are inserted into the material for measuring purposes. The second axis also shows the pressure P (unit: bar), which is the pressure P prevailing in the press cylinders 12 of the press 1, 1'. Due to Newton's third law ("force equals counterforce"), the pressing force exerted by the press cylinders 12 roughly corresponds to the contact force acting on the material. Nevertheless, the contact pressure differs from the pressure in the press cylinders because the two pressures act on different sized effective areas; the factor can vary from press to press. Finally, the third (vertical) axis shows the gap width 8 (unit: mm), i.e. the distance between the steel strips 2 ( Fig. 1) or between the heating plates 14 ( Fig. 2).

[0047] The Fig. The parameter curves shown in Figure 3 are explained below in chronological order. A first time t1 denotes the time at which the pressing process begins. This time is defined as the time at which a pressure P (key in Fig. 3: "Pressure") reaches or exceeds a value of 1 bar for the first time. The pressure P increases very quickly and reaches or exceeds a pressure of 100 bar at a second time t2. The increase in pressure P has the immediate consequence that the gap width 8 (key in Fig. 3: "Distance") until the gap width 8 reaches a value of approximately 2.2 mm at a third time t3. A working pressure P A which is approximately in the range between 100 bar and 115 bar, and kept as constant as possible. Since the heating plates 14 are heated (legend in Fig. 3: “Hot plate temperature above” about 250°C), the temperature T in the material (legend in Fig. 3: “MT 2” and “MT 4”) upon contact with the heating plates 14 starting from an initial temperature T A (e.g. room temperature; here about 30°C) and approaches the temperature of the heating plates 14 up to a maximum value T max of approximately 230°C. Due to temperature-induced effects, there is a variance around the desired pressure value, which, however, rapidly decreases when oscillating around the desired value.

[0048] At a fourth time t4, the pressure P is 100 bar and is rapidly reduced until the pressure P reaches a pressure P of 20 bar at a fifth time ts. The rapid pressure drop between the fourth time t4 and the fifth time ts causes the gap width 8 to increase slightly (to approximately 2.5 mm); nevertheless, contact between the press and the material is maintained because the gap width 8 is only slightly increased and the compressed and not yet fully consolidated material expands again as far as the gap width 8 allows due to the reduced pressure.

[0049] The pressure and temperature drop occur in a controlled manner, with the pressure P from the working pressure P A to a holding pressure P H which is approximately 20 bar or less and where the temperature T is different from the maximum temperature T max to a holding temperature T Hwhich is approximately in the range of 180°C. The pressing process is terminated at a sixth point in time t6, which (in analogy to the first point in time t1) is defined as the point in time at which a pressure P again reaches or falls below a value of 1 bar.

[0050] The pressing process thus begins at the first time t1 and ends at the sixth time t6. The pressing process can be simplified into four phases: a pressure increase phase (first time t1 to second time t2), a high pressure phase (second time t2 to fourth time t4), a pressure reduction phase (fourth time t4 to fifth time t5) and a holding phase (fifth time t5 to sixth time t6). Of particular interest is the pressure reduction phase, which in the Fig. The process shown in Figure 3, for example, lasts approximately 4 seconds (t4 to t5), during which the pressure is reduced by approximately 80 bar. The pressure drop is therefore approximately 20 bar per second. As a result of the rapid pressure reduction, the temperature in the material also drops quickly (albeit with a slight time delay). The temperature drop lasts approximately 1.5 seconds, during which the temperature drops by approximately 50°C (T max -> T H ). The temperature drop is therefore about 33°C per second.

[0051] Alternatively, the process can be divided into the phases “heating”, “cooling by controlled pressure relief” and “consolidation”. Fig. 3, the “heating” phase begins as soon as the temperature T rises from the initial temperature T Aand ends at the beginning of the pressure drop (fourth time t4). The second phase, "cooling by controlled pressure relief," follows immediately after this; it begins at the beginning of the pressure drop (fourth time t4) and ends approximately when the holding temperature T H or when the holding pressure P is reached H (fifth time point t5) into the third phase “Consolidation”. List of reference symbols: 1, 1' Press 1A, 1A' upper pressing device 1B, 1B' lower pressing device 2 steel bands 2A upper steel band 2B lower steel band 3, 3A roll (for steel band 2) 4 Drive 5 gap 6 Inlet 7 Outlet 8 gap width 9 Frame element 10 stiffening beams 11 Recess 12 press cylinders 13 Pressure distribution plate 14 Heating plate 14A upper heating plate 14B lower heating plate 15 roller bar 15A upper roller bar 15B lower roller bar 16 rolls (for roller carpet) 17 Inlet roller TR transport direction t time t1-t6 time point T Temperature T A Initial temperature T H Holding temperature T max Maximum temperature P pressure P A Working pressure P H Holding pressure P K Contact pressure QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2017 110 882 B4

[0041] DE 20 2012 104 004 U1

[0044]

Claims

[1] Method for producing a material board, in particular a wood-based board, from a material, comprising the following steps: a) providing at least one layer of a material, in particular a material containing wood chips and / or wood fibers, b) providing a press (1, 1') comprising: - an upper pressing device (1A, 1A') and a lower pressing device (1B, 1B'), between which a gap (5) is formed to receive the material, - wherein the upper pressing device (1A, 1A') and / or the lower pressing device (1B, 1B') has hydraulic pressing cylinders (12) which can change the gap width (8) between the upper pressing device (1A, 1A') and the lower pressing device (1B, 1B') and can transmit pressing forces to the material, and - wherein the upper pressing device (1A, 1A') and / or the lower pressing device (1B, 1B') has a heating device, in particular a heating plate (14A, 14B), which can at least indirectly transfer heat to the material, c) pressing the material in the gap (5) between the upper pressing device (1A, 1A') and the lower pressing device (1B, 1B'), d) heating the material in the gap (5) between the upper pressing device (1A, 1A') and the lower pressing device (1B, 1B'), - wherein steps c) and d) take place at least partly simultaneously, characterized by that during step d) the temperature (T) in the material is increased to at least 130°C, in particular at least 150°C, preferably at least 180°C. [2] Method according to claim 1, characterized by that during step d) the temperature (T) in the material increases strictly monotonically for at least 20 seconds, in particular at least 30 seconds. [3] Method according to claim 1 or claim 2, characterized by that the temperature (T) in the material is 150°C or more, in particular 180°C or more, for at least 10 seconds, in particular at least 20 seconds. [4] Method according to one of claims 1 to 3, characterized by that during step c) a reduction of the contact pressure acting on the material (P K ), whereby the contact pressure (P K ) by at least 50 N / cm 2 , in particular by at least 100 N / cm 2 , preferably by at least 200 N / cm 2 is lowered. [5] Method according to one of claims 1 to 4, characterized by that during step c) a reduction of the contact pressure acting on the material (P K ) at a speed of at least 100 N / cm 2 s, in particular at least 200 N / cm 2 s is done. [6] Method according to one of claims 1 to 5, characterized bythat during step c) a reduction of the pressure (P) of the press cylinders (12) from a working pressure (P A ) to a holding pressure (P H ), wherein the pressure (P) of the press cylinders (12) is reduced by at least 20 bar, in particular by at least 40 bar, preferably by at least 60 bar. [7] Method according to one of claims 1 to 6, characterized by that during step c) the pressure (P) of the press cylinders (12) is reduced at a speed of at least 10 bar / s, in particular at least 15 bar / s. [8] Method according to one of claims 1 to 7, characterized by that during step c) the gap width (8) is increased to a value in the range between +2% and +20%, in particular between +4% and +15% of the gap width (8). [9] Method according to one of claims 1 to 8, characterized bythat during step c) the temperature (T) in the material is reduced by at least 20°C, in particular at least 30°C, preferably at least 40°C. [10] Method according to one of claims 1 to 9, characterized by that during step c) the temperature (T) in the material is reduced at a rate of at least 10°C / s, in particular at least 20°C / s, preferably at least 30°C / s. [11] Method according to one of claims 1 to 10, characterized by that the contact pressure acting on the material (P K ) during step c) to a contact pressure (P K ) is lowered, which is in the range between 10 N / cm 2 and 150 N / cm 2 , especially between 30 N / cm 2 and 100 N / cm 2 lies. [12] Method according to one of claims 1 to 11, characterized by that the pressure (P) of the press cylinders (12) during step c) is reduced from a working pressure (P A ) to a holding pressure (PH ) which is in the range between 5 bar and 40 bar, in particular between 10 bar and 30 bar. [13] Method according to claim 11 or 12, characterized by that the reduced contact pressure (P K ) and / or the reduced holding pressure (P H ) is held for at least 10 seconds, in particular at least 20 seconds. [14] Method according to one of claims 1 to 13, characterized by that the temperature (T) depends on a maximum temperature (T max ) to a holding temperature (T H ), which is in the range between 120°C and 220°C, in particular between 140°C and 180°C. [15] Method according to one of claims 1 to 14, characterized by that the holding temperature (T H ) is held for at least 10 seconds, in particular at least 20 seconds. [16] Method according to one of claims 1 to 15, characterized by that in step b) a cyclically operating press (1') is provided, - wherein the upper pressing device (1A') is formed by a plurality of pressing cylinders (12) and an upper heating plate (14A), and - wherein the lower pressing device (1B') is formed by a lower heating plate (14B). [17] Method according to one of claims 1 to 15, characterized by that in step b) a continuously operating press (1) is provided, - wherein the upper pressing device (1A) is formed by a plurality of pressing cylinders (12), an upper heating plate (14A), an upper steel belt (2A) and upper rolling bars (15A), - wherein the lower pressing device (1B') is formed by a lower heating plate (14B), several pressure distribution plates (13), a lower steel belt (2B) and lower rolling bars (15B), - wherein the steel belts (2A, 2B) are mounted so as to rotate around rollers (3, 3A) that the gap (5) for receiving the material is formed between the steel belts (2A, 2B), and - wherein the roller bars (15A, 15B) are mounted so as to rotate around rollers (16) in such a way that they are arranged between the steel belts (2A, 2B) and the heating plates (14A, 14B) and enable a relative movement between the steel belts (2A, 2B) and the heating plates (14A, 14B). [18] Method according to one of claims 1 to 17, characterized by that in step a) the wood-based material is provided in multi-layer form, in particular in 3-layer, 5-layer or 7-layer form, in particular with at least one middle layer, at least one lower cover layer and at least one upper cover layer. [19] Method according to one of claims 1 to 18, characterized by that in step a) a wood-based material with a moisture content in the range between 2% ATRO and 40% ATRO, in particular between 5% ATRO and 30% ATRO, particularly preferably between 10% ATRO and 25% ATRO is provided. [20] Method according to one of claims 1 to 19, characterized bythat in step a) a wood-based material with a binder content of less than 15%, in particular less than 10%, preferably in the range between 0% and 6% is provided. [21] Method according to claim 20, characterized by that glue and / or bio-glue are used as binding agents. [22] Method according to one of claims 1 to 21, characterized by that in step a) fine wood chips are provided for the production of flat pressed boards and / or long chips are provided for the production of coarse chipboards or OSB boards. [23] Method according to one of claims 1 to 22, characterized by that in step a) wood fibers are provided for the production of wood fiber boards, for example medium-density wood fiber boards or MDF boards or high-density wood fiber boards or HDF boards, wherein the wood fiber boards produced preferably have smooth surfaces on both sides.

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