Method for finishing a wood based board

Abstract

A method for finishing a wood-based panel having a top surface, comprising the following steps: (Step 2) providing an unprinted base paper with a surface to be printed, (Step 4) applying a first resin to the unprinted base paper, (Step 8) printing a decoration onto the surface of the base paper using a printing system to create a decorative paper, (Step 10) assembling a stack of pressed material comprising at least the wood-based panel and the decorative paper, and (Step 12) pressing the stack of pressed material under increased pressure and / or increased temperature.

Description

[0001] The present invention relates to a method for refining a wood-based panel and a method for producing a decorative paper.

[0002] From EP 3 075 906 B1, an impregnation system is known in which a decorative paper web with an applied decoration is coated with a resin. The impregnation system has a sensor to enable practical online measurement of the properties of the decorative paper web.

[0003] EP 2 695 745 B1 discloses a method for manufacturing panels with a decorative surface, wherein the panel comprises a substrate and a top layer. The top layer consists of a paper layer with a printed pattern. The paper layer is coated with thermosetting resin and then provided with a printed pattern. The top layer is placed on the substrate and pressed together with it. The substrate may have a counter-tension on its side facing away from the top layer. A disadvantage is that the resin-coated paper is difficult to print on and delamination of the substrate and top layer can occur.

[0004] EP 3 023 261 A1 discloses a method for finishing a wood-based panel, in which a layer of liquid synthetic resin is applied to the top or bottom surface of the panel, and then a decorative paper impregnated with synthetic resin is applied to the top or bottom surface. A disadvantage of this method is that the impregnation of the decorative paper must take place in a separate impregnation unit with a resin bath, and the decorative paper impregnated with liquid synthetic resin is difficult to handle and has an increased risk of damage and irregularities.

[0005] The object of the present invention is to avoid or at least reduce disadvantages arising from the prior art.

[0006] The invention solves the stated problem by a method for refining a wood-based panel which has a top surface, wherein the method comprises the following steps: Providing an unprinted raw paper with a surface to be printed (top side), printing a decoration onto the surface using a printing system to create a decorated paper, assembling a stack of pressed material which includes at least the wood-based panel and the decorated paper, and pressing the stack of pressed material under increased pressure and / or increased temperature, the procedure is characterized by the following step: Applying a first resin to the unprinted raw paper, wherein the application of the first resin takes place at least partially, preferably completely, before the printing of the decoration.

[0007] The unprinted raw paper preferably has a basis weight between 40 g / m² and 100 g / m², for example 50 g / m² or 65 g / m².

[0008] The inventive method reduces the amount of resin, particularly melamine resin, required for finishing the wood-based panel. This lowers production costs and improves the compressibility of the pressed material stack. In the past, large quantities of resin have led to pressing problems.

[0009] This can be remedied or at least reduced by the method according to the invention.

[0010] According to the invention, the first resin is applied at least partially, but preferably completely, before the printing of the design. The surprising advantage of this embodiment is that printing ink can be saved, since the prior application of the first resin surprisingly improves the adhesion of the primer and / or the printing ink to the surface to be printed, and thus the colors appear more intense with the same amount of printing ink. This advantage is particularly pronounced when the first resin is applied only to the surface to be printed (top side) or at least also to the top side of the base paper before the design is printed. Alternatively or additionally, the first resin is applied at least partially, and in particular completely, after the design has been printed. Preferably, the first resin is applied in the digital printing system that also prints the design.This makes it possible to control the paper's growth very precisely. During impregnation, irregular paper growth can occur, leading to problems and difficulties during subsequent printing of the design, especially if a structure corresponding to the design (synchronous pore) is to be pressed into the surface.

[0011] Advantageously, several designs are printed onto the surface of the base paper. The designs are preferably essentially identical. Alternatively, the designs can also be different.

[0012] Preferably, the decorative paper is part of a paper web. The paper web preferably has at least one, and preferably several, decorative papers. Preferably, the paper web is a single piece. Preferably, the paper web is rolled into a roll after the decoration has been printed on it. Preferably, the first resin is applied before the paper web is rolled into a roll. Preferably, the decorative paper is cut or die-cut from the paper web before the press stack is assembled.

[0013] Preferably, the raw paper is placed on the top surface of the wood-based panel before the decoration is printed on it, most preferably by laminating it. The raw paper is placed on the wood-based panel, preferably by laminating it, and printed with the decoration in this state.

[0014] In a particularly preferred embodiment, a second resin is applied to the top surface of the wood-based panel before the base paper is laid on it, preferably before it is laminated. Preferably, the base paper is laid on or laminated onto the wood-based panel while the second resin is still wet. The still-moist resin ensures good adhesion, holding the base paper firmly to the top surface of the wood-based panel. In this state, the base paper can be printed with the decorative design particularly easily. Due to the preferably full-surface bond between the wood-based panel and the base paper, which is caused by the second resin, no paper growth occurs after the decorative design is printed onto the surface of the decorative paper, even though the printing process may introduce considerable amounts of moisture.

[0015] In another embodiment, the raw paper is printed with the decorative design before being placed on the wood-based panel. In this case, the stack of pressed material is formed, among other things, by placing the printed decorative paper on the top surface of the wood-based panel.

[0016] The first resin is preferably applied to the raw paper before the surface is printed. If the raw paper is printed with the decor in its laminated state, the first resin is preferably applied to the unprinted raw paper before the raw paper is mounted on the wood-based panel. An advantageous step of the process involves first applying the first resin to the unprinted raw paper and the second resin to the top surface of the wood-based panel. The raw paper coated with the first resin is then placed on the wood-based panel, preferably laminated, and then printed with the decor.

[0017] Another process involves applying the first resin to the unprinted base paper, which is then printed with the decorative design. Only in this printed state, as decorative paper, is the paper then applied to the wood-based panel, preferably laminated, after the panel has been coated with the second resin.

[0018] Preferably, the first resin is applied only to the side of the paper that faces the wood-based panel and that is not printed with the decoration.

[0019] Preferably, the second resin is applied to the top surface of the wood-based panel before the press stack is assembled. An advantage of this design is that the resin impregnation of the decorative paper and the wood-based panel no longer needs to be carried out in a separate impregnation plant. Surprisingly, in some embodiments, this design allows for integration into a single overall process for finishing a wood-based panel. Previously, separate impregnation in a complex impregnation plant was always required, which often cannot be located on-site, resulting in particularly high transport costs. This reduces manufacturing costs and the required production time. In some embodiments, less space is also required for the production machinery.Advantages arise particularly from combining this process with the resin impregnation of the unprinted base paper and / or the decorative paper, as the amount of resin required for the decorative paper can be reduced, thus making the unprinted base paper easier to print. Furthermore, the risk of delamination can be reduced. In some embodiments, the application of the first resin can be carried out using standard application rollers from laminate production and therefore no longer requires a separate impregnation unit with an impregnation bath.

[0020] Preferably, the second resin is applied to the underside of the wood-based panel before the pressed material is assembled. This counter-tensioning allows for the compensation of deformations caused by the first resin and, if applicable, the second resin on the top side of the wood-based panel. The underside of the wood-based panel is preferably spaced from the top side by a thickness equal to the thickness of the wood-based panel.

[0021] Preferably, the wood-based panel is heated before the second resin is applied. Particularly in this embodiment, drying of the second resin after its application and before pressing the stack of material is not required.

[0022] Preferably, the first resin is applied to the underside and / or the surface to be printed (top side) of the unprinted raw paper and / or the decorative paper.

[0023] Preferably, the first resin is applied only to the underside of the unprinted base paper and / or the decorative paper. An advantage of this design is that the unprinted base paper and / or the decorative paper is easier to handle, and the resin has no or only a minimal effect on print quality. Alternatively, the first resin is applied only to the top side of the unprinted base paper and / or the decorative paper.

[0024] Preferably, the entire surface of the top and / or bottom of the unprinted base paper and / or the decorative paper is wetted with the first resin. Preferably, the base paper is not completely, or at least not entirely, penetrated by the first resin. For example, it may be advantageous that only the underside of the unprinted base paper is wetted with resin and that the paper is not completely penetrated by the first resin. Preferably, an amount of the first resin is applied that is sufficient to wet the top or bottom of the unprinted base paper and / or the decorative paper, but not sufficient to completely penetrate the paper.

[0025] Preferably, the first resin is applied at a quantity of at least 2 g / m², more preferably at least 5 g / m², and in particular at least 10 g / m². More preferably, the first resin is applied at a quantity of at most 50 g / m², more preferably at most 20 g / m², and further preferably at most 10 g / m², and in particular at most 5 g / m².

[0026] Preferably, the second resin is applied at a quantity of at least 10 g / m², preferably at least 20 g / m², and particularly at least 30 g / m². More preferably, the second resin is applied at a quantity of at most 50 g / m², preferably at most 30 g / m², and particularly at most 20 g / m². These application quantities ensure sufficient bond thickness of the laminate composite.

[0027] Preferably, the second resin is applied in a larger quantity than the first. This improves the handling of the base paper and / or the decorative paper. Alternatively, the second resin is applied in the same quantity as the first resin or in a smaller quantity.

[0028] Preferably, the first resin and / or the second resin comprises or consists of a synthetic resin, in particular a melamine resin and / or a urea resin. Preferably, the first resin and / or the second resin comprises at least one additive, preferably a hardener, a wetting agent, and / or thermoplastic polymers.

[0029] In a preferred embodiment, the first resin and / or the second resin is applied by brushing, rolling, troweling, and / or spraying. Particularly preferably, the first resin and / or the second resin is applied using at least one application roller. The at least one application roller preferably has a rubber surface. Preferably, the application roller is unstructured. This means that the surface of the application roller that comes into contact with the base paper and / or the decorative paper has no raised or recessed structural elements. Alternatively or additionally, at least one application roller for the first resin and / or the second resin is structured.

[0030] Alternatively or additionally, the first resin and / or the second resin is sprayed onto the unprinted base paper and / or the decorative paper. For this purpose, the manufacturing device has at least one, preferably several, nozzles through which the first resin and / or the second resin is sprayed onto the unprinted base paper and / or the decorative paper. Preferably, several nozzles are arranged side by side and / or one behind the other. Preferably, the first resin and / or the second resin is applied homogeneously through the at least one nozzle. Alternatively, the first resin and / or the second resin is applied inhomogeneously through the at least one nozzle. For this purpose, the nozzles are preferably individually and independently controllable.

[0031] Preferably, the first resin and the second resin are applied through different nozzles. Alternatively, the first resin and the second resin are applied through the same nozzles.

[0032] Preferably, the first resin and / or the second resin is applied in liquid form. Preferably, the first resin and / or the second resin is mixed with water to form a resin-water mixture before application. The water content of the resin-water mixture is preferably at least 20%, more preferably at least 30%, and particularly at least 40%. More preferably, the water content of the resin-water mixture is at most 60%, more preferably at most 50%, and particularly at most 40%. Alternatively or additionally, the first resin and / or the second resin can be applied in a solid form.

[0033] Preferably, the first resin is applied from above to the underside and / or the top side of the unprinted base paper and / or the decorative paper. Alternatively or additionally, the first resin is applied from below to the underside and / or the top side of the unprinted base paper and / or the decorative paper.

[0034] The unprinted base paper is preferably fed into the printing press before the design is applied. This is preferably done automatically. Preferably, the underside of the unprinted base paper faces upwards when it is fed into the printing press. Preferably, the printed design paper is then turned over after the design has been applied and before the stack of paper is assembled, so that the printed surface (top side) faces upwards. This turning can also take place within the printing press, so that the printed design paper exits the printing press with its printed side facing upwards. Alternatively, the surface to be printed (top side) of the unprinted base paper can face upwards when it is fed into the printing press.

[0035] Preferably, the top side of the unprinted base paper faces upwards during the printing of the design, so that the printed design paper does not need to be turned over after the design is printed and before the stack of compressed goods is assembled. The printed surface then preferably faces upwards after the design is printed. Alternatively, the underside of the unprinted base paper faces upwards during the printing of the design.

[0036] In one embodiment of the invention, the unprinted raw paper is turned over after the first resin has been applied and before the decorative layer has been printed. This turning preferably takes place after the first resin has dried or hardened. Preferably, after turning, the top side of the decorative layer faces upwards. In this way, the first resin can be applied from above to the underside, and the unprinted raw paper can be printed from above onto the surface to be printed. Alternatively, the unprinted raw paper is not turned over before the decorative layer is applied. Preferably, the unprinted raw paper and the decorative paper are not turned over before the stack of paper is compressed, and thus, in particular, not turned over during the entire process of finishing a wood-based panel.

[0037] A further development of the invention is characterized in that the applied first resin and / or the applied second resin is dried or cured under elevated temperature and / or pressure. Preferably, the drying or curing of the first resin and / or the second resin takes place at least partially, but preferably completely, before the assembly of the pressed material stack and / or the pressing of the pressed material stack. Particularly preferably, the drying or curing of the first resin and / or the second resin takes place at least partially, but preferably completely, before the printing of the decoration, in order to prevent smearing of the resin. Alternatively, the drying or curing of the first resin and / or the second resin takes place at least partially, but particularly completely, after the printing of the decoration and / or after the pressing of the pressed material stack.Preferably, in this case, the application of the first resin and / or the second resin also takes place after the printing of the decoration or the pressing of the stack of pressed material.

[0038] After the decoration is printed, the decorative paper is preferably dried (further) to dry the printing ink. Drying preferably takes place at an elevated temperature.

[0039] Preferably, the first resin and / or the second resin has a degree of cross-linking of at most 80%, more preferably at most 60%, and particularly at most 40%, after drying or curing. More preferably, the first resin and / or the second resin has a degree of cross-linking of at least 20%, and particularly at least 30%, after drying or curing. This ensures sufficient flexibility of the resin for further processing.

[0040] Preferably, the degree of cross-linking of the first resin and / or the second resin after pressing the stack of material is at least 80%, preferably at least 90%, and in particular at least 95%.

[0041] Preferably, the drying or curing of the first resin and the second resin takes place at least partially, but preferably completely, simultaneously. This reduces energy consumption and consequently also manufacturing costs.

[0042] Preferably, the unprinted base paper and / or the decorative paper has a residual moisture content of at most 20%, more preferably at most 10%, and particularly at most 6%, after drying or hardening. Preferably, the unprinted base paper and / or the decorative paper has a residual moisture content of at least 2%, more preferably at least 4%, and particularly at least 6%, after drying or hardening.

[0043] Preferably, the residual moisture content of the decorative paper after pressing the stack of material is at most 4%, preferably at most 2%, and in particular at most 1%.

[0044] The resins, in particular the first resin and / or the second resin, preferably have three states, namely a state A in which the resin is liquid and completely reactive, a state B in which the resin is dried, in particular partially cured, and still largely reactive, and a state C in which the resin is completely cured and thus essentially no longer reactive.

[0045] Preferably, the first resin and / or the second resin are in state B after drying or curing and before pressing the stack of material. Alternatively or additionally, the first resin and / or the second resin are in state A after application of the first resin and / or the second resin and before pressing the stack of material.

[0046] Preferably, the first resin and / or the second resin are in state C after the pressing of the stack of material.

[0047] A further development of the invention is characterized by the application of a primer to the surface to be printed prior to printing the design. This improves the color fidelity of the design. Preferably, the primer is dried before the design is printed. The primer preferably contains calcium chloride and / or methanol. The primer can be dried together with the first resin and / or the second resin, or separately. Preferably, the primer is applied to the unprinted paper after the first resin has been applied. Alternatively, it can also be applied before the first resin has been applied to the unprinted paper and / or the printing paper. Preferably, the primer is applied to the surface to be printed at a rate of at least 2 g / m², more preferably at least 4 g / m², and particularly at least 5 g / m².Preferably, the amount of primer applied to the surface to be printed is at most 20 g / m², preferably at most 10 g / m², and in particular at most 6 g / m².

[0048] The printing system is preferably a digital printing system, more preferably a single-pass digital printing system. In such a single-pass digital printing system, the paper to be printed passes the printheads of the digital printing system only once. The printheads preferably extend across the entire printing width. The printing inks used are preferably cyan, red, yellow, and black (CRYK).

[0049] Preferably, the first resin and the second resin are identical. Alternatively, the first resin and the second resin are different.

[0050] After the design is printed, the decorative paper is placed on the top surface of the wood-based panel. Preferably, the decorative paper is placed on the wood-based panel so that the printed surface (top side) of the decorative paper faces upwards. The top surface of the wood-based panel is preferably sanded.

[0051] Preferably, the pressed material stack comprises an overlay paper that is placed on the top side of the decorative paper laid on the wood-based panel. The advantage of this is that the overlay paper increases the strength of the pressed composite. Preferably, the overlay paper is placed on the top side of the decorative paper so that one side of the overlay paper faces upwards. Preferably, the overlay paper is at least partially, but preferably completely, transparent after the pressed material stack has been pressed. Advantageously, the overlay paper has a residual moisture content of at most 30%, preferably at most 20%, and particularly at most 10% when the pressed material stack is assembled. Preferably, the residual moisture content of the overlay paper when the pressed material stack is assembled is at least 2%, more preferably at least 4%, and particularly at least 6%.

[0052] Preferably, the overlay paper is resin-coated. For example, the overlay paper can have an overlay resin coating on its top and / or bottom surface. Preferably, the overlay resin coating comprises or consists of the first resin and / or the second resin.

[0053] Preferably, the unreinforced overlay paper has a coating weight of at most 50 g / m², more preferably at most 40 g / m², more preferably at most 30 g / m², and in particular at most 20 g / m². Preferably, the overlay resin coating has a basis weight of at least 10 g / m², more preferably at least 30 g / m², and in particular at least 50 g / m². More preferably, the overlay resin coating has a basis weight of at most 200 g / m², more preferably at most 150 g / m², and in particular at most 100 g / m².

[0054] The resin of the overlay resin application is preferably dried and is preferably in state B before pressing the stack of material. Preferably, the resin of the overlay resin application is in state C after pressing the stack of material.

[0055] Preferably, at least one protective layer is applied to the decorative paper and / or the overlay paper. Preferably, at least one protective layer is applied to the resin-impregnated overlay paper. This can, for example, improve abrasion resistance, walkability, and / or water resistance. The application of the at least one protective layer preferably takes place before pressing the stack of pressed material and / or before assembling the stack.

[0056] Preferably, at least one protective layer comprises or consists of corundum. Preferably, corundum is applied at a rate of at least 5 g / m², preferably at least 10 g / m², and particularly at least 20 g / m². Alternatively or additionally, at least one protective layer comprises or consists of glass beads, plastic beads, metal particles, and / or pyrogenic silica.

[0057] Preferably, at least one protective layer and / or one resin layer, for example a resin layer formed by the first resin and / or the second resin, is imprinted with a structure during the pressing of the stack of pressed material, which corresponds to the decoration. For example, the structure can depict the course of edges, joints, grains, knots or pores in the decoration.

[0058] Preferably, the stack of pressed material comprises a backing paper on which the wood-based panel is placed. Such a backing paper can significantly reduce or completely compensate for any warping caused by pressing the stack of pressed material. In some embodiments, resin coating of the underside of the wood-based panel is not required, thus simplifying the overall finishing process. Preferably, the backing paper is resin-coated. For example, it can have a backing resin coating on its top and / or underside. Preferably, the backing resin coating comprises or consists of the first resin and / or the second resin.

[0059] Preferably, the unresin-coated backing paper has a coating weight of at most 50 g / m², more preferably at most 40 g / m², more preferably at most 30 g / m², and in particular at most 20 g / m². Preferably, the backing resin coating has a basis weight of at least 10 g / m², more preferably at least 30 g / m², and in particular at least 50 g / m². More preferably, the backing resin coating has a basis weight of at most 200 g / m², more preferably at most 150 g / m², and in particular at most 100 g / m².

[0060] The resin of the counter-tension resin application is preferably dried and is preferably in state B before the pressing of the pressed material stack. Preferably, the resin of the counter-tension resin application is in state C after the pressing of the pressed material stack.

[0061] According to a second aspect, the invention solves the technical problem by a method for producing a decorative paper, wherein the method comprises the following steps: Providing an unprinted raw paper with a surface to be printed, printing a decoration onto the surface using a printing system, so that a decorated paper is created, the procedure is characterized by the following step: Applying a first layer of resin to the unprinted raw paper and / or the decorative paper.

[0062] Advantageous embodiments of the process for producing decorative paper can be found in particular in the preceding explanations of the process for finishing a wood-based panel. Example 1 - Applying the first coat of resin after printing the design.

[0063] In a first embodiment, an unprinted base paper with a basis weight of, for example, 50 g / m² or 65 g / m² is provided. A primer is applied to the surface to be printed (top side) of the base paper using an application roller. The decorative design is then printed onto the surface to be printed, resulting in a decorative paper. After the decorative design is printed, the paper is coated with the first resin on the top side, bottom side, or both sides. In this embodiment, this is done using an application roller. The first resin is, for example, a melamine resin with a solids content of 60% to 65%, containing a hardener and a wetting agent. The application rate of the first resin in this embodiment is 6 g / m². The moisture content of the resin-coated decorative paper is approximately 5.3% to 5.8% immediately after the application of the first resin.After the first resin is applied, the decorative paper is dried using IR emitters at approximately 70 °C, so that the first resin changes from state A (liquid) to state B (dried and still largely reactive). The residual moisture content after drying is approximately 3.6% to 4.1%.

[0064] A wood-based panel is first sanded and heated using infrared emitters. A second resin is then applied to the top surface of the wood-based panel. This second resin contains a hardener and has a solids content of approximately 60% to 65%. The amount of the second resin applied to the top surface of the wood-based panel is approximately 20 g / m² to 25 g / m². In this configuration, the second resin is not dried but remains in state A until the stack of pressed material is compressed.

[0065] In the next step, the stack of pressed material is assembled. First, a resin-impregnated backing paper is prepared. The wood-based panel is placed on the backing paper, followed by the decorative paper, and finally a resin-impregnated overlay paper coated with abrasion-resistant particles (e.g., corundum) on top of the decorative paper. The stack is then pressed in a short-cycle press at a temperature of approximately 200 °C and a pressing pressure of less than 50 kg / m² for a pressing time of approximately 15 seconds. Example 2 - Applying the first layer of resin before printing the design.

[0066] In a second embodiment, an unprinted base paper with a basis weight of, for example, 50 g / m² or 65 g / m² is provided. The unprinted base paper is coated with a first resin on its underside (variant 1) or on its top side (variant 2). In this embodiment, this is done by means of an application roller.

[0067] The first resin is, for example, a melamine resin with a solids content of 60% to 65%, containing a hardener and a wetting agent. In this embodiment, the application rate of the first resin is 6 g / m². The moisture content of the resinated base paper is approximately 5.3% to 5.8% immediately after application. After application, the base paper is dried using IR emitters at approximately 70 °C, so that the first resin changes from state A (liquid) to state B (dried and still largely reactive). The residual moisture content of the resinated base paper after drying is approximately 3.6% to 4.1%.

[0068] After drying, a primer is applied to the surface (top side) of the raw paper to be printed. The design is then printed onto the surface using a digital printing system, resulting in a decorative paper.

[0069] A second resin is applied to a sanded and preheated wood-based panel. This second resin contains a hardener and has a solids content of approximately 60% to 65%. The application rate of the second resin to the top surface of the wood-based panel is approximately 20 g / m² to 25 g / m². In this configuration, the second resin is not dried but remains in state A until the stack of pressed material is compressed.

[0070] The stack of pressed material is formed (from bottom to top) from a resin-impregnated backing paper, the wood-based panel, the decorative paper and a resin-impregnated overlay paper coated with abrasion-resistant particles.

[0071] The stack of material is then compressed in a short-cycle press at a temperature of approximately 200 °C and a pressing pressure of 50 kg / m² and for a pressing time of approximately 15 s.

[0072] Particularly in variant 2 of embodiment 2, a saving of printing ink is surprisingly possible, since the pre-coating of the paper surface results in improved adhesion of the primer and the printing ink to the surface to be printed, so that the colors appear more intense with the same amount of printing ink and primer.

[0073] In another embodiment, an HDF board, forming the wood-based panel, is coated multiple times with a small amount of the second resin. In various trials, the HDF board was coated between 3 and 9 times, each time with an amount of 10 g / m². After each application of the second resin, the coated board was not dried in a dryer. Thus, a total of between 30 g / m² and 90 g / m² of the second resin was applied. Subsequently, the base paper was laminated with an amount of the first resin between 30 g / m² and 65 g / m². The adhesion of the laminated base paper thus meets all requirements for further processing. The laminated base paper was then printed in a single-pass digital printing system and subsequently dried. Applying a primer beforehand may be advisable. Finally, a topcoat was applied to the surface.After optional drying in a dryer, the layered structure can be stacked until it is ready for pressing.

[0074] Since the raw paper to be printed, unlike in conventional printing processes, no longer expands when it is arranged and laminated onto the wood-based panel, it is no longer necessary to use dimensionally stable papers, thus reducing production costs. Furthermore, the substrate, i.e., the paper laminated onto the panel, can be cooler than when printing directly onto a wood-based panel without laminated paper. Printing with liquid white ink requires a large amount of energy to be transferred to the panel, resulting in an ink temperature of approximately 60°C during the printing process, which generates a significant amount of condensation. Printing on paper allows for considerably lower temperatures.

[0075] In a preferred embodiment, the first resin is applied in the form of a resin-containing liquid. The process then comprises the following steps: a. Providing an unprinted raw paper with a surface to be printed, b. Applying a resinous liquid to the surface so that the surface is saturated with the resinous liquid, c. Printing a design onto the resin-soaked surface using a digital printing system to create a printed paper, d. Forming a press stack by placing the printed paper on top of the wood-based panel, and e. Pressing the press stack under increased pressure and temperature.

[0076] First, the unprinted raw paper is provided, which, for example, has a basis weight of 50 g / m² or 65 g / m². The first resin, in the form of the resinous liquid, is applied to the surface of this unprinted raw paper so that the surface is saturated with the resinous liquid. This means that preferably the entire surface is wetted with the resinous liquid. However, the raw paper is not impregnated, i.e., completely permeated, with the resinous liquid. Rather, preferably an amount of the resinous liquid is applied that is sufficient to saturate the surface of the paper, but not sufficient to completely impregnate the paper.Preferably less than 15 g / m², more preferably less than 10 g / m², particularly preferably less than 8 g / m², and at least 5 g / m², preferably at least 6 g / m², particularly preferably at least 7 g / m² of the resin-containing liquid are applied.

[0077] The resinous liquid contains the first resin, i.e., at least one synthetic resin, but preferably does not consist entirely of it.

[0078] After the resin-containing liquid has been applied to the surface of the paper, the design is printed onto the resin-impregnated surface. Preferably, the paper is first dried in a dryer to reduce its moisture content. The design is printed in a digital printing system, preferably a single-pass digital printing system. In such a single-pass digital printing system, the paper to be printed passes the printheads of the system only once. Preferably, the digital printing system has printheads that extend across the entire printing width, with separate printheads for each of the printing inks used being particularly preferred. The printing inks used are preferably cyan, red, yellow, and black (CRYK). Water-based inks are particularly preferred.

[0079] The printed paper is preferably dried in a dryer to reduce its moisture content. The printed paper is then placed on the top surface of the wood-based panel to be finished. The top surface of the wood-based panel is preferably sanded. A synthetic resin is preferably applied to the top surface of the wood-based panel. This synthetic resin is preferably the same resin contained in the resinous liquid.

[0080] The stack of material to be pressed, which includes the wood-based panel and the printed paper placed on its top surface, is pressed under increased pressure and temperature, preferably using a short-cycle press.

[0081] In a preferred embodiment, the resinous liquid contains or consists of melamine resin and / or urea resin.

[0082] Advantageously, the resin-containing liquid contains a primer and / or at least one substance that improves the adhesion of ink applied during printing. In a particularly simple embodiment of the invention, the resin-containing liquid contains a mixture of a synthetic resin and a primer. It is advantageous if the proportion of the primer in the mixture is as small as possible but sufficient for the desired color effect of the decoration. For example, the proportion of the primer in the mixture is such that at least 1 g / m², preferably at least 1.5 g / m², particularly preferably at least 2 g / m² and at most 4 g / m², preferably at most 3.5 g / m², and particularly preferably at most 3 g / m² of primer are applied with the resin-containing liquid. Preferably, the proportion of the primer in the mixture is at most 40 wt%, more preferably at most 30 wt%, and particularly preferably at most 20 wt%.

[0083] Alternatively or additionally, the resinous liquid contains at least one synthetic resin to which substances are added that improve the adhesion of the inks used in printing the decor, especially the pigments. These substances can be called primers or wetting agents. If no mixture of a synthetic resin and a primer is used, the proportion of synthetic resin in the resinous liquid is higher, so that more synthetic resin is available to be used when the stack of panels is subsequently pressed to produce the laminate board. In this case, the amount of synthetic resin that needs to be applied to the surface of the wood-based panel can be reduced.

[0084] Preferably, the resin-containing liquid is applied to the surface of the base paper in such a way that it does not completely penetrate the paper, at least not entirely. There may be individual spots or areas where the resin-containing liquid completely penetrates the paper, but preferably no such spots or areas are present. In a particularly preferred embodiment, the resin-containing liquid is applied to the surface of the base paper using an application roller. The application roller is preferably a roller with a rubber surface. Preferably, the application roller is unstructured. This means that the surface in contact with the base paper has no raised or recessed structural elements.

[0085] Alternatively or additionally, the resin-containing liquid is sprayed onto the surface of the base paper. For this purpose, the device has at least one, preferably several, nozzles through which the resin-containing liquid is sprayed onto the surface of the base paper. Preferably, the nozzles are arranged such that a homogeneous distribution of the resin-containing liquid is achieved on the sprayed surface. By using several nozzles, which can preferably be controlled individually and independently of one another, inhomogeneous distributions of the resin-containing liquid on the sprayed surface can also be achieved. This is useful, for example, if the required amount of primer or primer substances is not identical everywhere on the surface to be printed, for example, because the decoration requires different amounts of printing ink in some places and in some areas.In this case, the areas to be printed with a lot of ink are preferably also sprayed with a larger amount of primer.

[0086] In a particularly advantageous configuration, the resin and primer(s) are mixed directly in front of the nozzles, or separate nozzles are used for the resin and the primer(s), allowing the materials to be sprayed separately. This enables areas requiring less primer to be sprayed with a larger quantity of resin. This ensures, for example, that the surface of the raw paper is sprayed with a homogeneous amount of liquid. This is especially beneficial for subsequent drying, as it allows the surface to dry uniformly. The paper growth induced by the applied liquid can also be homogeneous and therefore easier to manage.

[0087] In a preferred embodiment, the resin-containing liquid is applied using two application units, one application unit being provided for the primer and another application unit for the synthetic resin.

[0088] Preferably, the printed paper is impregnated with a synthetic resin or a synthetic resin mixture before being applied to the top surface of the wood-based panel. It has proven advantageous if the printed paper is impregnated with the same synthetic resin or synthetic resin mixture that was applied to the unprinted base paper and / or to the top surface of the wood-based panel.

[0089] Preferably, at least one layer of a synthetic resin or a synthetic resin mixture is applied to the top surface of the wood-based panel before the printed paper is placed on the top surface.

[0090] Advantageously, the raw paper is dried in at least one dryer after the application of the resinous liquid and before printing with the decoration.

[0091] In a preferred embodiment, an overlay paper is placed on top of the printed paper placed on the upper side of the wood-based panel when forming the pressable material stack.

[0092] Preferably, the pressed material stack comprises an overlay paper that is placed on the top side of the decorative paper laid on the wood-based panel. The advantage of this is that the overlay paper increases the strength of the pressed composite. Preferably, the overlay paper is placed on the top side of the decorative paper such that one side of the overlay paper faces upwards. Preferably, a resin, for example, the first resin or the second resin, is applied to one side and / or one side of the overlay paper. This further increases the strength of the pressed composite. Preferably, the overlay paper is at least partially, but preferably completely, transparent after the pressed material stack has been compressed. Preferably, the overlay paper has a basis weight of at most 50 g / m², more preferably at most 40 g / m², more preferably at most 30 g / m², and particularly at most 20 g / m².The overlay paper is preferably not additionally coated with resin.

[0093] With the aid of the attached figure, which shows a schematic flowchart, some embodiments of the invention are explained in more detail below.

[0094] In a first step 2, an unprinted base paper with a surface to be printed is provided. In a second process step 4, a first resin in the form of a resin-containing liquid is applied to this base paper. In the illustrated embodiment, this includes a primer.

[0095] The decoration is printed onto this surface in printing step 8. Optionally, the paper can be laminated onto the wood-based panel before printing in printing step 8, but after the first resin has been applied in the resin-containing liquid. This takes place in lamination step 6. After printing step 8 and optional drying steps not shown, the press stack is formed in process step 10, which contains both the wood-based panel and the printed paper, which is then a decoration paper. This is independent of whether the decoration paper and the wood-based panel are still separate elements or whether the decoration was printed onto the paper laminated onto the wood-based panel.

[0096] The next step is pressing step 12, in which the stack of material to be pressed is compressed.

Claims

1. A method for finishing a wood-based panel having a top surface, comprising the following steps: - providing an unprinted base paper with a surface to be printed, - printing a decoration onto the surface of the base paper using a printing system to produce a decorative paper, - assembling a stack of pressed material comprising at least the wood-based panel and the decorative paper, and - pressing the stack of pressed material under increased pressure and / or increased temperature. characterized by the fact that A first layer of resin is applied to the unprinted raw paper.

2. Method according to claim 1, characterized by the fact that The raw paper is placed on the top of the wood-based panel before the decoration is printed on it, preferably laminated.

3. Method according to claim 2, characterized by the fact that A second resin is applied to the top surface of the wood-based panel before it is laid on, preferably before the raw paper is laminated.

4. Method according to any of the foregoing claims, characterized by the fact that Before assembling the stack of pressed material, the second resin is applied to one underside of the wood-based panel.

5. Method according to any of the foregoing claims, characterized by the fact that The first resin is applied only to the underside of the unprinted raw paper and / or the decorative paper.

6. Method according to any of the foregoing claims, characterized by the fact that the first resin contains at least one additive, preferably a hardener, a wetting agent and / or thermoplastic polymers.

7. Method according to any of the foregoing claims, characterized by the fact that The first resin is applied by brushing, rolling, troweling and / or spraying.

8. Method according to any of the foregoing claims, characterized by the fact that The first applied resin is dried or cured under increased temperature and / or increased pressure.

9. Method according to any of the foregoing claims, characterized by the fact that the first resin with a quantity of at least 2 g / m² 2 , preferably at least 5 g / m² 2 , in particular at least 10 g / m² 2 , is applied.

10. Method according to any of the foregoing claims, characterized by the fact that the first resin with a quantity of no more than 50 g / m² 2 , preferably no more than 20 g / m² 2 , in particular a maximum of 10 g / m² 2 , is applied.

11. Method according to any of the foregoing claims, characterized by the fact that Before printing the design, a primer is applied to the surface.

12. Method according to any of the foregoing claims, characterized by the fact that The printing system is a digital printing system.

13. Method according to any of the foregoing claims, characterized by the fact thatThe stack of pressed material has an overlay paper that is placed on top of the decorative paper laid on the wood-based panel.

14. Method according to any of the foregoing claims, characterized by the fact that at least one protective layer is applied to the decorative paper and / or the overlay paper.

15. Method according to any of the foregoing claims, characterized by the fact that at least one protective layer of corundum or that consists of it.

16. Method according to any of the foregoing claims, characterized by the fact that at least one protective layer consisting of or containing glass beads, plastic beads, metal particles and / or pyrogenic silica.

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