Process for producing a particleboard and particleboard

Abstract

The invention relates to a process for producing a particleboard and to a particleboard. In order to propose a process in which a particleboard having improved properties, especially having elevated strength, can be produced, the following steps are envisaged: – providing particles; – providing at least one adhesive; – applying the adhesive to the particles, with application of an adhesive content of at least 12% by weight / atro particles to the particles; – forming a single- or multilayer particle cake; – pressing the particle cake in a press to give a particleboard. The invention further encompasses a particleboard.

Description

[0001] METHOD FOR PRODUCING A CHIPBOARD AND CHIPBOARD

[0002] The invention relates to a method for producing a chipboard and to a chipboard.

[0003] The processes mentioned above are used to press chips, sawdust and / or sawdust provided from wood, for example from round wood, fresh wood, waste wood or residual wood or from annual plants such as straw or bagasse, into particle boards.

[0004] To produce particleboard, the wood, such as round or scrap wood or annual plants, is first reduced to chips in a knife-ring flaker, for example. To produce fine chips, the chips can be further reduced in a double-flow mill or impact mill, for example. Before possible interim storage in silos, the chips are usually dried. Single-pass or triple-pass drum dryers or belt dryers are typically used for this purpose.

[0005] Before pressing in a press, the chips are fractionated, e.g., using mechanical sieves or blowers, and then bonded with an adhesive. When bonding the chips, an adhesive content of 2 to n wt.% per dry wood is usually used. The bonded chips are scattered, e.g., using a wind, throwing, or roller process, and the resulting chip cake is then pressed into a particle board, e.g., in a continuous and / or discontinuous press.

[0006] Particleboards manufactured using conventional processes have established themselves in various applications in several industrial and construction sectors, particularly for interior design and the furniture industry. However, particleboards exhibit limited strength and poor water and moisture resistance, which severely restrict their application possibilities. Long-term or even permanent outdoor use is virtually impossible for conventional, possibly coated, particleboards.

[0007] The object can be considered to propose a method by which a chipboard with improved properties, in particular with increased strength, can be produced. Furthermore, the invention is based on the object of providing a chipboard with improved properties, in particular with increased strength.

[0008] The object is achieved by a method for producing a chipboard according to claim i and a chipboard according to claim 13. Dependent claims relate to advantageous developments of the invention.

[0009] The method according to the invention for producing a chipboard comprises the following steps:

[0010] Providing wood shavings;

[0011] Providing at least one adhesive, applying the adhesive to the chips, wherein an adhesive content of at least 12 wt.% / dry wood is applied to the chips; forming a single- or multi-layer chip cake,

[0012] Pressing the chip cake in a hot press to produce a chipboard.

[0013] The steps of the process correspond to those of a conventional process, e.g., for producing a flat pressed board. However, according to the invention, an adhesive content of at least 12 wt.% / dry wood is used. Based on the proportion of chips, an adhesive content of at least 15 wt.% / dry wood, preferably at least 17 wt.% / dry wood, particularly preferably at least 20 wt.% / dry wood, very particularly preferably at least 25 wt.% / dry wood is applied to the chips. Provided that an upper limit for the moisture content of the layer and / or layers of the chip cake is observed after gluing, any desired amount of adhesive can be applied to the chips. The upper limit of the moisture content is preferably between 1 wt.% / glued wood to 20 wt.% / glued wood, preferably between 3 wt.% / glued wood to 18 wt.% / glued wood, particularly preferably between 5 wt.% / glued wood to 15 wt.-% / glued wood.

[0014] The adhesive content is expressed relative to the chips, meaning that the adhesive content is specified relative to the weight of the chips used. For chips that can absorb moisture (e.g., wood chips), the adhesive content is based on wood dried to constant weight. The chips are dried to constant weight at 103±2 °C and are referred to as absolutely dry wood (absolutely dry wood). The adhesive content is specified as 100% solids, i.e., without any added liquid.

[0015] To produce chips, lignocellulosic material, such as wood (e.g., roundwood, fresh wood, waste wood, or annual plants, typically straw or bagasse), is shredded in a single- or multi-stage chipping process. Typical devices for chipping wood include drum and disc chippers, as well as knife-ring chippers. In addition to the chips obtained from chipping, sawdust and sawdust can also be produced. The chips preferably have a length of 0.5 mm to 50 mm, a width of 0.1 to 20 mm, and a thickness of 0.05 mm to 2 mm. A distinction is often made between coarse chips with a length of 5 mm to 50 mm, a width of 1 to 20 mm and a thickness of 0.2 to 2 mm and fine chips with a length of 0.5 mm to 25 mm, a width of 0.1 to 5 mm and a thickness of 0.05 to 1 mm.

[0016] If the chips contain moisture, as is usual for wood chips from fresh wood, for example, the moisture content should be adjusted before pressing the chip cake so that after pressing, particularly under constant climatic conditions without storage in water, a dimensionally stable chipboard is produced that does not expand or shrink. During pressing, e.g. in the chipboard process, it is preferable for the chips to have a moisture content of 1 wt.% / dry wood to 4 wt.% / dry wood before gluing. The chips are dried to achieve the desired moisture content. The chips can be sorted, e.g. sieved, before or preferably after drying. During sorting, the chips are divided into four fractions (dust, fine chips, coarse chips and oversized chips). Dust is preferably separated from the other fractions and is preferably used for energy recovery. Oversized and / or coarse chips can be screened out and preferably re-shredded.

[0017] The inventors recognized that the high adhesive content in the gluing of the chips allows the production of a water-resistant and thus also moisture-resistant chipboard that also exhibits high strength. It has also surprisingly been found that swelling of the chipboard, e.g., due to 24 hours of water storage, is reversible due to the high adhesive content. The swelling behavior is preferably determined according to DIN EN 317. After just 24 hours of re-drying, e.g., at room temperature, the chipboard regains its original dimensions, e.g., initial length, initial width, and initial thickness before 24 hours of water storage. From this, it can be concluded that the adhesive bonds remain essentially undamaged during exposure to water. This swelling-shrinkage behavior has not been observed with chipboards before; rather, a proportional, irreversible residual deformation was common.The complete reversal of the deformation caused by swelling opens up new areas of application for chipboard.

[0018] Particularly preferred for the production of the particleboard is an adhesive comprising a first, thermosetting component and a second, thermoplastic component. The adhesive is used in a proportion of at least 12 wt.% of the dry wood to 60 wt.% of the dry wood, preferably from 15 wt.% of the dry wood to 45 wt.% of the dry wood, particularly preferably from 18 wt.% of the dry wood to 35 wt.% of the dry wood, in particular from 20 wt.% of the dry wood to 33 wt.% of the dry wood, advantageously from 24 wt.% of the dry wood to 31 wt.% of the dry wood.

[0019] According to an advantageous embodiment of the invention, a condensation resin, in particular aminoplasts such as melamine-formaldehyde resin, urea-formaldehyde resin (UF resin), or benzoguanamine resin, as well as phenolplasts such as phenol-formaldehyde resin (PF resin), are used as the thermosetting component, either individually or in a mixture. Aminoplasts are used in aqueous solution, e.g., as melamine resin, usually as melamine-formaldehyde resin (MF resin), with the solids content of the aminoplast preferably being at least 45 wt.% based on the aqueous solution; advantageously, the solids content is above 50 wt.%. The upper limit of the solids content is determined by the solubility and, if applicable, processability of the aminoplast in the production process, e.g., in spray nozzles or high-pressure gluing processes.

[0020] The adhesive preferably comprises melamine resin, e.g., MF resin (melamine-formaldehyde resin), at least as its first component. Melamine resin is preferred because it has low swelling and low hygroscopicity, as well as being resistant to hydrolysis. Alternatives include phenolic resin, urea resin, or mixtures or combinations of several of these thermosetting first components. Although urea resin is not resistant to hot water, it can surprisingly be used, especially in a mixture with melamine resin and / or phenolic resin, to produce the particle board according to the invention. Melamine resin, in particular, can be used either alone as the first component or in combination with one or more of the other thermosetting components. The proportion of UF resin is preferably up to 50% by weight of the MF or PF resin, without impairing the water resistance or strength of the particle board.

[0021] In the context of this invention, "in combination" means that mixtures of resins of the first component can be used, whereby either the mixture of two or more resins of the first components is applied to the chips simultaneously. Or several different resins of the first component are used sequentially, e.g., because they cannot be used in a mixture or because separate application of different resins of the first component or individual resins of the first component of the adhesive has a beneficial effect, e.g., on the subsequent product and / or application properties.

[0022] Preferably, technical diphenylmethane diisocyanate (PMDI) is applied to the chips as the second, thermoplastic component of the adhesive. Alternatively or additionally, other substances such as methylene diphenyl isocyanate (MDI), also in emulsified form as eMDI, but also polyurethane can be used as the second component. The proportion of the second component is preferably more than 1 wt. %, in particular 3 wt. % or more, advantageously 5 wt. % or more, in each case based on dry wood. The proportion of the second component, e.g. PMDI, in the chipboard according to the invention is thus significantly higher than in conventional chipboards. Advantageously, the second component of the adhesive, e.g. PMDI, is also used in a multi-layer structure of the board, or in particular, in the cover layers of the chipboard according to the invention. The second component is preferably used in the same amount in the middle layer and in the cover layer.Here, too, several substances suitable as a second component can be applied to chips either in a mixture with each other at the same time or individually one after the other.

[0023] Preferably, at least one third component, for example, a polyol or polyether, can be added to the first and second components of the adhesive, preferably as a solid. The third component can be added in a proportion of up to 15 wt.%, preferably up to 10 wt.%, particularly preferably in a proportion of 2 to 5 wt.%, based on the total amount of the adhesive.

[0024] According to an advantageous embodiment, the elastic properties of the chipboard can be modified, in particular improved, by adding an elastomer or thermoplastic used as an elasticizing additive, e.g., by adding polyvinyl acetate (PVAc) or ethyl vinyl acetate. Particularly preferably, an elastomer or thermoplastic is applied to the chips as an elasticizing additive, in particular in addition to the first and second components of the adhesive. Advantageously, the elasticizing additive is not added to the first or second component of the adhesive, nor is it applied to the chips with one of the components of the adhesive. Acrylate, styrene acrylate, or polyurethane (PU) are preferably used to elasticize the chipboard according to the invention, in particular in the form of a liquid additive such as a dispersion or emulsion, because they are water-resistant.Acrylate, styrene acrylate and PU with a glass transition temperature of TG below 0 °C are preferably used. However, mono- or diethylene glycol are also suitable for elasticizing the chipboard. The above-mentioned elasticizing additives can be used individually or in mixtures. The addition of elastomers or thermoplastics reduces the brittleness of the chipboard and improves its elastic properties, e.g. the modulus of elasticity. Furthermore, the addition of elasticizing additives results in better flatness of the chipboard according to the invention. The elasticizing additive is calculated as a solid proportional to the total amount of chipboard (dry) in an amount of preferably 1 wt.% up to 7 wt.%, advantageously 2 wt.% to 7 wt.%, preferably 2 wt.% to 6 wt.%, particularly preferably 2.5 wt.% to 5.5 wt.%. The elasticizing additives are added, for example, to the adhesive, e.g.Melamine resin is added to the chips before application and applied to the chips together with the adhesive. The elasticizing agent is preferably applied to the chips before or, more preferably, after the adhesive.

[0025] As described above, a first and a second, or optionally more, components are used in combination as an adhesive. It is preferred if the adhesive predominantly comprises a first component, in particular melamine resin. It is further preferred if the proportion of the first component in the total adhesive used exceeds 15% by weight, in particular 20% by weight. The first component and the second component of the adhesive can be continuously adjusted within a wide range depending on the requirements of the chipboard. In the case of a multi-layer board structure, this preferably applies to both the middle layer and the further layers. They are preferably applied to the chips in a ratio of 2:1, preferably 3:1, particularly preferably 4:1 or 5:1 of first component to second component, or in a ratio between these values.If the chipboard according to the invention has cover layers, a higher proportion of the first component of the adhesive is preferably used compared to the middle layer.

[0026] The adhesive is usually provided in liquid form, but can also be in solid form, e.g. in the form of particles or powder. The adhesive can be provided in pure form or - as is usually the case - in liquid form, proportionally dissolved either in solvent or in water, as a dispersion or emulsion. In the context of this invention, adhesive is always specified based on 100% solids, i.e. without, for example, the solvent or water content. The application, in particular coating, of the adhesive onto the chips is usually carried out by spraying, e.g. through a plurality of nozzles, e.g. high-pressure nozzles, which generate a spray of the adhesive and which can, for example, be arranged around a downward flow of chips. Typical designs for such a gluing device are, for example, a so-called chute and / or additionally a conventional gluing mixer, which are used in chipboard production.Coarse chips are preferably glued in a chute and then passed through a conventional glue mixer, where one or more of the adhesive components are preferably applied. Fine chips are glued in a conventional glue mixer and / or a chute.

[0027] The surface of the chips is wetted with adhesive droplets or a mist of adhesive. The adhesive-coated chips are formed into a chip cake and then pressed together. If a thermosetting adhesive is used, the adhesive cures under the influence of increased pressure and temperature; it polymerizes, for example, in an irreversible addition or condensation reaction. If a thermoplastic adhesive is used, it sets thermally reversibly. The thermoplastic adhesive mechanically bonds to the chips during pressing. Both components of the adhesive are preferably used in combination.

[0028] Depending on the type, quantity, or combination of adhesive components, the adhesive can be applied to the chips in one or several passes. Optionally, the chips can be dried after application of, for example, one component of the adhesive.

[0029] As is usual with chips, the chip cake is generally formed by scattering, for example using the wind scattering method and / or throw scattering method. The chips, coated with the entire amount of adhesive, are scattered onto a carrier, usually onto a conveyor belt, e.g. in a homogeneous layer, or in several layers, whereby the layers can have a different composition in terms of chips, adhesive, elasticizing additive or possibly additives. The scattered chip cake is first pre-compacted on the carrier using a pre-press if necessary and then pressed in a press. The press acts on the top and bottom of the chip cake or chipboard using pressing elements, e.g. press plates or press belts. During curing orSetting, which occurs under the influence of pressure and temperature essentially on the top and bottom of the chip cake, creates a chipboard with a width and, if applicable, length specified by the press or, in the case of a continuous press, of infinite length and a thickness specified by the distance between the pressing elements.

[0030] In principle, any press that applies sufficient pressure and temperature is suitable for producing particleboard. This includes a panel press in which the particle board is pressed between two metal sheets, and continuous hot presses, e.g. a continuous double-belt hot press in the form of rotating, heated metal press belts. In this press, the particle board is pressed between two rotating press belts, and the resulting particle board is transported through the press by the rotating press belts at a predetermined speed. Hot presses are preferably used whose pressing elements, e.g. in the form of press plates or rotating press belts, are heated to a predetermined temperature. Suitable pressing temperatures, measured as the temperature of the pressing elements, can be selected from 150 °C to 240 °C, preferably from 160 °C to 220 °C.The thinner the sheet, the lower the pressing temperature can be. Suitable pressing pressures, for example, are in the range of 2 N / mm. 2 up to 5 N / mm 2 , preferably 3 N / mm 2 up to 5 N / mm 2 , particularly preferably 3.5 N / mm 2 up to sN / mm 2 .

[0031] The compression factor, i.e., the time the compression elements are in contact with the particle board, is advantageously at least 6 seconds / mm of board thickness (hereinafter: s / mm) to 20 s / mm, preferably 8 s / mm to 18 s / mm, particularly preferably 9 s / mm to 15 s / mm. This makes the compression factor significantly higher than comparable, known standard particle boards of type P2 according to DIN EN 312, where it is up to 5.5 s / mm.

[0032] The chips or chip cake are particularly preferably pressed into a chipboard with an odd number of layers. For example, the chipboard has three or five layers lying one above the other. In a chipboard with three layers, for example, a middle layer is arranged between two cover layers. The chips are preferably already scattered during the shaping of the chip cake to form the different layers. The cover layers preferably comprise predominantly fine chips, which are preferably scattered using the wind scattering method. The middle layer preferably contains predominantly coarse chips, which are scattered, for example, using the throw scattering method. The middle layer typically consists of a proportion of at least 30 wt.%, preferably at least 45 wt.%, particularly preferably at least 60 wt.% of a pressed chipboard.The surface layers are distributed symmetrically or asymmetrically relative to each other, based on their weight proportions. If the particle board according to the invention consists of a single-layer structure, different particle fractions of the coarse and fine particles described above are combined in one layer.

[0033] The actual hot-pressing process can be preceded by a pre-press to compact the chip cake. In principle, a release agent can be applied, in particular sprayed, to the carrier, e.g., the conveyor or forming belt, and / or the top surface of the cake. Particularly preferably, the release agent, e.g., a liquid containing various polymers, in particular a silicone-containing liquid, is applied to the pressing elements of the press, thereby preventing the chip cake / chipboard from sticking to the pressing elements. For application to the pressing elements, the release agents are preferably mixed with a fluid medium, in particular water.

[0034] Optionally, a device for cooling the chipboard can be connected downstream of the press, in particular a device for cooling under a predetermined pressing pressure, which can be lower than the pressing pressure during the chipboard pressing. Alternatively and / or additionally, the chipboard can be cooled at room temperature.

[0035] To produce the particleboard according to the invention, one or more additives, e.g., antioxidants, light stabilizers, antistatic agents, colorants, fungicides, flame retardants, agents for adjusting thermal or electrical conductivity, or even one or more fillers, can also be used. Mineral particles, but also ceramic, synthetic particles, or particles made of glass or plastic, can be used as fillers. A combination of additives or fillers can also be applied to the particles, either individually or as a mixture. Fillers and / or additives can also be applied, in particular coated, in a mixture with the adhesive.

[0036] According to an advantageous embodiment of the invention, a hydrophobic agent is applied to the chips before pressing the chip cake, in particular after gluing the chips. Suitable hydrophobic agents include paraffin or wax, which are typically used in amounts of up to 5 wt.% per dry wood, usually in amounts of up to 2 wt.% per dry wood, often in amounts of 0.1 wt.% per dry wood to 1 wt.% per dry wood, possibly up to 1.5 wt.% per dry wood. The use of hydrophobic agents contributes to reducing the swelling tendency of the chipboard and increasing its moisture resistance.

[0037] According to an advantageous development of the invention, the chipboard is sanded after pressing. For this purpose, a sanding device with an abrasive, e.g., sandpaper and / or preferably a sanding belt, can be provided. Sanding is typically carried out in two sanding steps, with abrasives with a grain size of 50-60 being used in the first sanding step and 80-100 in the second sanding step. The chipboard according to the invention has a harder surface than known chipboards according to DIN EN 312, for which a coarser grain size of the abrasive is preferred. Preferably, the grain size in both sanding steps is a maximum of 60, preferably a maximum of 50, particularly preferably a maximum of 40.

[0038] The particle board produced using the method described above can be adapted to various requirements by using different combinations of particles, adhesive, fillers, and, if necessary, other additives such as waxes. It is therefore expressly pointed out that the features described in connection with this invention can be freely combined with one another.

[0039] The invention further relates to a particle board with an adhesive content of at least 12% per dry wood. The particle board is produced in particular using the method described above. The particle board according to the invention is preferably waterproof and thus also moisture-resistant. It has excellent and unusual swelling and shrinkage behavior, with slight swelling accompanied by substantial regression of the swelling during subsequent drying.

[0040] The chipboard according to the invention is formed in a plate shape as a result of pressing, i.e. it generally has two main surfaces, which are also referred to below as the top and bottom. The top and bottom are spaced from each other by the thickness of the chipboard. The narrow surfaces of the chipboard extend between the top and bottom, each of which merges into the top and bottom at the edges. The thickness of the finished chipboard can be from 2 mm to 80 mm, typically between 3 mm and 50 mm, mostly between 3 mm and 32 mm. A typical application may require a chipboard thickness of 6 mm to 32 mm. The chipboard can have flat main surfaces; however, the top and / or bottom can also be embossed or milled or processed in some other way, resulting in a variable thickness of the chipboard, based on the surface area of ​​the chipboard.

[0041] The chipboard preferably has an odd number of layers across its thickness. It is, for example, single-, three-, or five-layered. The narrow surfaces of the chipboard according to the invention can be machined using conventional tools. They can be sawn, cut, or milled. The chipboard can be cut to its maximum length and width as required, for example, during final production. Smaller dimensions can be produced, for example, by disassembling the chipboard originally produced in the press. Typical dimensions of the chipboard can be 6700 mm (length) x 2500 mm (width) after production in the press, 1380 mm x 195 mm after division into floor, wall, or ceiling panels, or 3048 mm x 2800 mm. The latter format is particularly suitable for use in construction because the width of the board corresponds to a standard floor height.

[0042] Advantageously, the particle board according to the invention exhibits only minimal thickness swelling, in particular in accordance with the test method described in DIN EN 317, which, based on the original board thickness, is less than 5%, advantageously less than 4%, preferably less than 3%, particularly preferably less than 2.5%. Likewise advantageously, an uncoated particle board exhibits edge swelling in accordance with the test method described in EN 13329 of less than 6%, preferably less than 5%, and a coated particle board particularly preferably exhibits edge swelling of less than 4%. The swelling can be reduced by over 90% compared to a standard particle board of the same thickness made from the same particle material but with less adhesive used and other types of adhesive.A value of less than 5% for the edge swelling of the uncoated chipboard and less than 4% for the edge swelling of a coated chipboard is therefore an exceptional improvement compared to known chipboards according to DIN EN 312.

[0043] The average density of the particle board according to the invention is preferably 800 kg / m 3 up to 1,000 kg / m 3 , preferably 830 kg / m 3 up to 970 kg / m 3 , particularly preferably 850 kg / m 3 up to 950 kg / m 3 . It is therefore around 100 kg / m 3 up to 300 kg / m 3 higher than known chipboards of type P2 according to DIN EN 312.

[0044] The particle board according to the invention has very good strength properties, in particular a high transverse tensile strength of at least 2.5 N / mm 2 , preferably up to 3 N / mm 2 , especially up to 4 N / mm 2 Preferably, the chipboard has an E-modulus of 3000 N / mm 2up to 5000 N / mm 2 , advantageously from 3500 to 5000 N / mm 2 , particularly preferably from 4000 to 5000 N / mm 2 The good strength properties mean that fewer fasteners, e.g. screws, are needed to attach the chipboard according to the invention, because each fastener has a better hold in the board. The higher transverse tensile strength also allows more intensive processing of a chipboard according to the invention, e.g., milling simple profiles into the side edge of a board. For example, at least one simple profile, such as a tongue and groove profile, can be incorporated into the narrow surface of a chipboard, which aligns two interlocking boards both vertically and horizontally. A high bending strength of the chipboard of at least 35 N / mm 2 , preferably at least 40 N / mm 2allows use as a construction element, e.g. wall stiffeners. The invention further relates to the use of the chipboard described above for structural purposes both indoors and outdoors. The chipboard according to the invention is distinguished by the fact that it can be used in a variety of ways due to its minimal swelling, in particular the reduced thickness swelling in the area of ​​the narrow surfaces. In interior construction, the chipboard can be used, for example, as a floorboard or as a floor covering, with or without a coating. In contrast to, for example, non-waterproof floorboards or floor coverings, it can also be used in damp and wet rooms, in particular because the narrow surfaces, which may have an edge profile where the board is freely accessible to moisture, no longer swell significantly under the influence of water or high humidity and almost completely regain their original dimensions when drying.

[0045] This means that, for example, a chipboard that is essentially non-swelling and dimensionally stable against water or humidity, with high strength values, can now be produced on known devices for the production of wood-based panels, and is not limited to narrow formats.

[0046] Of course, the chipboard according to the invention can also be used as a wall or ceiling panel, as a furniture panel, and as a construction panel, particularly in the construction of damp and wet rooms or laboratory and technical rooms or workshops, but is not limited to this. In exterior construction, the chipboard according to the invention is also suitable as a construction panel, typically, for example, as a facade panel, for exterior window sills, coverings including roof coverings, and wall elements.

[0047] The chipboard according to the invention can be used, for example, for terrace construction or outdoor flooring. This makes it possible to use the same floors or floor coverings for indoor and adjacent outdoor areas (patios, balconies, facades, access routes). The chipboard according to the invention can preferably be used for outdoor constructions, in particular furniture. The construction of workshops, production halls, or stables, for example, can easily be carried out using the chipboard according to the invention. Furthermore, due to its water resistance, the chipboard according to the invention can also be used, for example, for fire protection elements and building elements in shipbuilding, especially when provided or coated with fire protection substances.

[0048] The chipboard according to the invention is suitable for the aforementioned uses even in its uncoated state. As a coated chipboard, it is even more suitable due to further reduced deformation due to exposure to water. The chipboard can optionally be designed as a panel and, if required, provided with a profile on the edges. The profile is preferably used to fix two panels together. Two adjacent panels can alternatively be joined butt to butt. They can be fixed, for example, using double-sided adhesive tape arranged in the area to the side of a joint between the directly adjacent panels. Gluing directly adjacent panels or boards is also possible, whereby a waterproof adhesive is preferably used.

[0049] An embodiment of the invention is explained in more detail below with reference to the drawings. These show:

[0050] Fig. 1 is a flow chart of a method for producing a chipboard;

[0051] Fig. 2 shows a schematic perspective view of a chipboard;

[0052] Fig-3 a raw density profile of an embodiment (Invention 1) of the chipboard according to the invention and

[0053] Fig.4 a raw density profile of a standard chipboard of type P2 according to DIN EN 312.

[0054] Figure 1 shows a flow diagram of a method for producing a chipboard i shown in Figure 2. The method comprises the following steps:

[0055] Providing chips (A) Providing adhesive (B) Applying the adhesive (C) Forming a chip cake (D) Pressing the chip cake (E)

[0056] To produce chips, lignocellulosic material, typically wood, e.g., roundwood, fresh wood, waste wood, or residual wood, but also annual plants such as straw or bagasse, is first processed into chips 7, 8 in a single- or multi-stage chipping process, for example, in drum and disc chippers or knife-ring chippers. The chips 7, 8 are then dried, e.g., in a single-pass or three-pass drum dryer and fractionated, for example, using a sieve, into fine chips 7 and coarse chips 8.

[0057] A mixture of a first, thermosetting component and a second, thermoplastic component is used as the adhesive. The thermosetting component can be selected from aminoplasts such as melamine resin, benzoguanamine resin, or urea resin, or from phenolic resins, such as phenolic resin, each of which can be used individually or in a mixture. The second component is selected from MDI, eMDI, PMDI, or polyurethane, each of which can also be used individually or in a mixture. Preferably, as in the exemplary embodiment, melamine resin is provided in combination with PMDI. The provision of the chips and the adhesive is followed by application, in this case, for example, coating the adhesive onto the chips.

[0058] The adhesive is sprayed through nozzles in a known device for gluing chips. The spray mist created by the nozzles condenses on the surface of the chips, which pass through the spray mist, e.g., falling from top to bottom through the spray mist of adhesive. In addition to the adhesive, a hydrophobic agent, in this case paraffin or hydrowax, is applied to the chips at a proportion of 1 wt.% / dry wood. The high proportion of adhesive according to the invention, here 25 wt.% / dry wood in the outer layers and 30 wt.% / dry wood in the middle layer, can be applied in one or more passes, depending on the type, amount, and combination of the components of the adhesive. If necessary, the chips can be dried after application of one component of the adhesive. After the adhesive has been completely applied, the chips are dried.

[0059] The adhesive is applied separately, e.g. for fine chips from which the top layers are to be made and for coarser chips for the middle layer. The composition of the adhesive can also be selected differently for fine chips than for coarser chips, e.g. with a lower proportion of a first, thermoplastic component of the adhesive compared to the adhesive for coarser chips. In this case, the adhesive is used with a first component made of melamine resin and a second component made of PMDI in a ratio of 4:1 for the top layer and in a ratio of 5:1 for the middle layer, with an average of 27.5 wt.% based on dry wood being used, divided into 25 wt.% / dry wood adhesive in the top layers, which each make up 25%, together making up 50% of the board mass, and 30 wt.% / dry wood adhesive in the middle layer, which also makes up 50% of the board mass.It is obvious that both the proportions of middle layer and top layers can vary, as can the amount of adhesive used.

[0060] After the adhesive has been applied and dried, the chips 7, 8 are applied in a known spreading device and spread into a chip cake, e.g., for the formation of a lower cover layer 5, a middle layer 6, and an upper cover layer 5. The fine chips 7 are deposited for the cover layers 6, for example, using the known wind scattering method. The coarser chips 8 are deposited for the middle layer 6, for example, using the known throw scattering method.

[0061] The three-layer chip cake is then pressed in a well-known continuously operating double-belt hot press at temperatures of 160 °C to 240 °C, in this case 180 °C and a pressure of up to 5 N / mm 2 , here: 4.5 N / mm 2at a press factor of 6 s / mm to 20 s / mm, here: 9.35 s / mm. Before and / or during the pressing of the chip cake, a release agent mixed with water, e.g., a liquid containing various polymers, in this case, silicone, is applied to the press plates or press belts of the press to protect against sticking. Following pressing, the chipboard is preferably cooled to room temperature. In a known sanding device, the top and bottom sides 2, 3 of the chipboard are then sanded in two sanding passes, each using an abrasive with a grain of, for example, 50.

[0062] In further steps, the chipboard can be cut, milled, and / or coated, e.g., painted, laminated, or printed. It is then usually stacked and stored and / or prepared for transport.

[0063] According to a preferred embodiment, as shown in Fig. 2, the particleboard 1 produced using the method described above comprises a top side 2, a bottom side 3, and a narrow surface 4, as well as an upper and a lower cover layer (DS) 5 and a middle layer (MS) 6 arranged between the cover layers. The middle layer 6 comprises essentially coarser chips 8, and the cover layers 5 comprise essentially fine chips 7. The chips 7 and 8 are each embedded in adhesive. The adhesive content is more than 15% by weight per dry wood, here an average of 27.5% by weight per dry wood.

[0064] Particleboard 1 is compared with a standard particleboard of class P2 (DIN EN 312:2010), which was made from the same particle material and with the same adhesive components, but with a significantly lower adhesive content in the middle and outer layers. The outer layers of the standard particleboard P2 do not contain PMDI. Overall, the proportion of PMDI in the middle layer of a standard particleboard (0.1 to 0.6 wt.% / dry wood) is much lower than in the particleboard according to the invention (5 wt.% / dry wood). Figures 3 and 4 show the density distribution across the cross-section of the particleboard. The density is given in kg / m³ in each case. 3plotted against the position along the board thickness in mm. Furthermore, in Figs. 3 and 4, line H1 represents the average density, line H2 represents 85% of the average density, line V1 represents the maximum density on the left (first facing layer), and line V2 represents the maximum density on the right (second facing layer). The particleboard according to the invention has an average density of 850 kg / m 3 up to 950 kg / m 3 , here according to Fig. 3 e.g. 897 kg / m 3 In comparison, the standard P2 chipboard has an average density of 640 to 720 kg / mm² at a comparable thickness. 3 , here according to Fig. 4 e.g. 707 kg / mm 3 Furthermore, the particle board according to the invention has a maximum density of approximately 1080 kg / mm ​​in the cover layers 5 (lines Vi and V2). 3 The standard particleboard P2 has a maximum density of approximately 850 kg / mm ​​in the outer layers (lines Vi and V2). 3 on.

[0065] The following tables 1 and 2 show the two chipboards (Invention 1 and Standard) in comparison, with the board thickness in mm as gross value (before sanding) and the density in kg / m 3 The particle boards were evaluated for transverse tensile strength (DIN EN 319), swelling (measured according to DIN EN 317) and edge swelling (measured according to DIN EN 13329) (see Table 2).

[0066] Furthermore, Table 1 shows test results of two further embodiments (Invention 2 and Invention 3) of the particleboard according to the invention. The second embodiment differs from the first embodiment by a higher board thickness of 19 mm and a lower target density of 660 kg / m 3 , which is achieved by a low chip load of 490 kg / m 3 and a correspondingly lower adhesive usage of 130 kg / m 3However, the third embodiment differs from the first embodiment with the same plate thickness of 8 mm by a lower target density of 720 kg / m 3 , which also has a low chip load of 550 kg / m 3 and a correspondingly lower adhesive usage of 150 kg / m 3 These lighter chipboards also exhibit improved strength properties and improved water resistance compared to standard P2 chipboard.

[0067] Table 1

[0068] Comparative tests of a standard and an inventive chipboard

[0069]

[0070] Table 2

[0071] Comparative tests on swelling and strength values ​​of the standard and the inventive chipboard from Table 1

[0072] *not measurable

[0073] The particle board according to the invention must be more densely packed than a conventional standard particle board. The adhesive factor is approximately 2 to 5 times higher than that of the prior art particle board, and approximately 3 times higher in the examples shown in Table 1. The proportion of the second component of the adhesive is much higher than that of the standard particle board; it is disproportionately increased by more than 10 times compared to the increased use of the first component. The particle board according to the invention exhibits a 10-fold reduction in swelling of the raw board (DIN EN 317) and a more than three-fold increase in transverse tensile strength (DIN EN 319). Furthermore, the particle board according to the invention exhibits a more than 1.5-fold higher modulus of elasticity and a more than 1.5-fold increase in flexural strength compared to the standard particle board P2.

[0074] After coating the top and bottom surfaces, the edge swelling of a coated board is measured. Only the narrow surfaces of the chipboard are exposed to water, as the top and bottom surfaces of the board are sealed by the coating and are no longer accessible to water. This test is particularly important for floor coverings because the narrow surfaces of the floors generally cannot be sealed and are thus exposed to water. This test shows significantly reduced edge swelling for the chipboard according to the invention compared to a conventional chipboard whose edge swelling is so high that the value could not be measured. Both the standard chipboard and the chipboard according to the invention were manufactured on the same industrial production lines.

[0075] Table 3 shows a recipe for a further exemplary embodiment (Invention 4) of the particle board according to the invention with a lower proportion of the first, thermosetting component of the adhesive (gluing factor) in the cover layers and in the middle layer compared to the other exemplary embodiments. The adhesive in this exemplary embodiment has a melamine-formaldehyde resin as the first, thermosetting component. The particle board according to this exemplary embodiment is characterized by an elasticizing additive, here for example styrene acrylate, in the cover layers, which improves the flatness of the particle board according to the invention. The components of the recipe are each given in wt. % / dry wood. Furthermore, the particle board according to this exemplary embodiment contains, for example, a hydrowax as a hydrophobizing agent (emulsion) and, for example, ammonium sulfate as a hardener.

[0076] Table 3

[0077] Recipe of a particle board according to the invention

[0078] 1 chipboard

[0079] 2 Top

[0080] 3 Bottom

[0081] 4 Narrow surface

[0082] 5 Top layer

[0083] 6 Middle class

[0084] 7 fine shavings

[0085] 8 coarse shavings

[0086] A Provision of chips

[0087] B Providing adhesive

[0088] C Application of the adhesive

[0089] D Forming a chip cake

[0090] E Pressing of the chip cake Hi medium density

[0091] H2 85% of the average density

[0092] Vi maximum density left

[0093] V2 maximum density right

Claims

Claims 1. Method for manufacturing a particleboard, comprising the steps Providing wood chips (7,8) obtained from machining, providing at least one adhesive, - Applying the adhesive to the chips (7, 8), wherein an adhesive content of at least 12 wt.% / atro wood is applied to the chips (7, 8), forming a single- or multi-layer chip cake and pressing the chip cake in a hot press to produce a particleboard (1), characterized in that an elastomer or a thermoplastic is added as an elasticizing additive to modify the elastic properties of the particleboard, wherein the elasticizing additive is used as a solid calculated proportionally based on the total amount of the particleboard (atro) in an amount of 1 wt.% to 7 wt.%.

2. Method according to claim 1, wherein the adhesive comprises at least a first component made of a thermosetting material and a second component made of a thermoplastic material, characterized in that the first component and the second component of the adhesive are applied to the chips (7, 8) in a ratio of first component to second component of 2:1 to 5:1, advantageously of 3:1, preferably 4:1 or 5:

1.

3. Method according to claim 2, characterized in that the first thermosetting component of the adhesive is a condensation resin, in particular an aminoplast, such as a melamine-formaldehyde resin, a benzoguanamine resin or a Urea-formaldehyde resin, or a phenolic resin such as a phenol-formaldehyde resin, are used individually or in a mixture. A method according to claim 2 or claim 3, characterized in that the second, thermoplastic component of the adhesive is technical-grade diphenylmethane diisocyanate (PMDI), methylenediphenyl diisocyanate (MDI), also in emulsified form as eMDI, or polyurethane, either individually or in a mixture. A method according to any of the preceding claims, characterized in that one or more components of the adhesive are applied individually and / or in a mixture to the chips (7, 8). A method according to any of the preceding claims, characterized in that acrylate, styrene acrylate, or polyurethane is used as an elasticizing additive to plasticize the particleboard.A method according to any of the preceding claims, characterized in that the elasticizing additive is applied to the chips before or preferably after the adhesive, in particular in addition to the first and second components of the adhesive. A method according to any of the preceding claims, characterized in that an adhesive content of at least 15 wt.% / atro wood, preferably at least 17 wt.% / atro wood, particularly preferably at least 20 wt.% / atro wood, and most preferably at least 25 wt.% / atro wood is applied to the chips (7, 8). A method according to any of the preceding claims, characterized in that the particleboard (1) has at least surface layers (5) and a middle layer (6), wherein the surface layer (5) and the middle layer (6) each have different adhesives and / or different adhesive compositions. A method according to any one of the preceding claims, characterized in that the chips (7, 8) are pressed in a continuous press with a pressing force of at least 6 s / mm to 20 s / mm, preferably 8 s / mm to 18 s / mm, particularly preferably 9 to 15 s / mm. A method according to any one of the preceding claims, characterized in that the chips (7, 8) are pressed with a pressing pressure of 2 to 5 MPa, preferably 3 to 5 MPa, particularly preferably 3.5 to 5 MPa. A method according to any one of the preceding claims, wherein the particleboard (1) is ground after pressing and / or after cooling, characterized in that an abrasive with a grit size of at most 60, preferably at most 50, particularly preferably at most 40, is used.Particleboard, in particular produced by a process according to one of the preceding claims, comprising wood chips obtained from machining and an adhesive content of at least 12% per dry chips, characterized in that an elastomer or a thermoplastic is added as an elasticizing additive, wherein the elasticizing additive is used as a solid in a quantity of 1 wt.% to 7 wt.%, calculated proportionally based on the total quantity of the particleboard (dry). Particleboard according to claim 13, characterized in that the elasticizing additive is used as a solid in a quantity of 2 wt.% to 7 wt.%, preferably 2 wt.% to 6 wt.%, and particularly preferably 2.5 wt.% to 5.5 wt.%, calculated proportionally based on the total quantity of the particleboard (dry). 15- Particleboard according to claim 13 or 14, characterized by a mean density of 800 to 1000 kg / m³ 3 preferably 850 to 950 kg / m² 3, especially preferably 900 to 950 kg / m³ 3 16. Particleboard according to one of claims 13 to 15, characterized by a maximum swelling of 4% based on the original thickness of the particleboard.

17. Particleboard according to one of claims 13 to 16, characterized by an E-modulus of 3000 N / mm² 2 - 5000 N / mm 2 preferably 3500 to 5000 N / mm 2 , especially preferred 4000 to 5000 N / mm 2 .

18. Use of a particleboard according to one of claims 13 to 17 for structural purposes in interior and exterior areas, in particular for facade panels, exterior window sills, covers, roof coverings and wall elements as well as wet rooms.

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