ES2635320T3 - Procedure for manufacturing a board of material derived from wood, in particular a board of material derived from wood provided with a decorative layer - Google Patents

Abstract

Process for manufacturing a board of wood-derived material, in particular a board of wood-derived material provided with a decorative layer, comprising the following steps: - providing at least one support board of wood fibers, - moistening with aqueous vapor at least one section of a surface of at least one support board of wood fibers, the aqueous vapor being applied in an amount of 1 to 10 g / m2, - sand the surface moistened at least by sections of the support board of wood fibers and - apply at least one decorative layer on the surface moistened with at least sections of the wood fiber support board.

Description

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DESCRIPTION

Procedure for manufacturing a board of material derived from wood, in particular a board of material derived from wood provided with a decorative layer

The present invention relates to a process for manufacturing a board of wood-derived material in accordance with the main concept of claim 1 and a device for carrying out this process according to claim 12.

Description

As support materials, boards of wood-derived material are used in the most diverse areas such as, for example, as floor panels in the form of laminate floors, as insulating material boards for interiors and exteriors or also as wall panels. Such material boards are usually manufactured from wood fibers, wood chips or strands, using, for example, in the case of laminate floors, HDF boards made from wood-derived fibers (HDF fiber board with high apparent density) with multiple decorative patterns.

To decorate such boards of wood-derived material there are several approaches. In this way, there is a possibility in the coating of boards of material derived from wood with a decorative paper, there being no limits for the plurality of decorative papers of different patterns. As an alternative to the use of decorative papers on boards of wood-derived material, the possibility of direct printing of boards of wood-derived material was increasingly developed, omitting paper printing and subsequent lamination or direct coating on wood. boards of material derived from wood. In this regard, the printing techniques that are mainly used are the gravure printing process and digital printing. The gravure printing procedure is a printing technique in which the elements to be printed are present as depressions in a printing mold, for example, in a printing roller, which is inked before printing. Digital printing allows the production of a print image with a particularly high quality through a higher resolution and additionally allows a wider spectrum of applications with great flexibility. In this regard, in recent years the printing of wood-derived material boards was developed from simple two-color prints in the gravure printing procedure for back walls of furniture, through the printing in four colors in the procedure of gravure printing, for example, for laminate flooring products, even digital printing for the highest quality applications. The use of medium density fiber boards (MDF boards) or fiber boards with high apparent density (HDF boards) proves to be particularly advantageous for direct printing, since they guarantee a good print image thanks to the smooth surface and fine. In this regard, the printing is generally carried out on a primer, in particular, a primer containing pigments, which, during the preparation of the surface of the fiber board derived from the wood for printing, is almost always applied several sometimes through roller application mechanisms. In order to improve the quality of the surfaces, one or more sanding groups can also be placed before and / or between the application mechanisms. With the help of them you can eliminate irregularities of height and so! the quality of the surface to be printed from the wood-derived fiber board can be improved. Through the primer, on the one hand, a uniform surface will be formed, on the other hand, through the pigmentation of the primer layer, the natural color of the material derived from the wood will be covered.

In this regard, a fundamental requirement for the uniform priming of wood-derived fiber boards is a level of humidity as uniform as possible from the wood-derived fiber board used as a support board, and should not be too low. of humidity as uniform as possible. Thus, the humidity of a fiber board derived from wood should be above approximately 4%.

However, due to the specific manufacturing process of wood-derived fiber boards comprising hot pressing of glued wood-derived fibers, after production in the cooling process and during storage of the derived fiber boards of the wood, considerable differences of humidity in the cross-section in the boards and in the distribution of humidity in general can be presented. Thus, in the course of the manufacturing process of wood-based fiber support boards, the fibers are transported under pressure and with high temperatures of compressor belts through ace! called continuous presses. In this regard, the coating layers of the future wood-derived fiber boards are largely dehydrated, while the intermediate layers get wet. After cooling the boards, for example, in ace! called star walls, in which there is also a loss of moisture, the hot panels are still stacked and stored. In the course of the storage process, in this regard, a dehydration of the edges of the boards is first presented, while in the center of the stack of boards there is a uniform distribution, that is, a homogenization of the temperature and of moisture After complete cooling, the edges of the boards are moistened again from the outside inwards, the cooling and the new wetting being carried out sometimes more quickly and sometimes more slowly, depending on the storage temperature and the relative humidity of the air. As a value of experience, it can be said that cooling requires more time

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during the summer, while the new wetting occurs more rapidly during the summer, due to the moisture content in the air that is normally higher during the summer. On the contrary, cooling occurs more rapidly during the winter, but reclimatization, that is, the new wetting of the boards requires more time because of the reduced moisture content of the air.

Differences in drying and moisture behavior lead to considerable problems during subsequent priming or printing. It is very difficult, or even impossible, to print on a wood fiber board that has not yet cooled or is not at a uniform humidity level. The wood fiber boards are too dry, mainly in the edge region, and, therefore, can be moistened only in a limited way or in very reduced form with water-based primers. This circumstance manifests itself through insufficient and irregular applications with the typical light color to white primer. In addition, due to these priming defects in a region of 20 to 40 g of primer / m2, a primer surface has considerable irregularities. The printing rollers in the gravure printing process subsequently will no longer be able to print completely on these irregularities in the primer. This will then lead to defective places of light color in the print, which were created by the still visible primer of light color. The problem is that the humidity responsible for this cannot be determined exactly, that is, the uneven distribution of moisture on the surface of a wood fiber board, since for the quality of the wetting of the board surface Only the moisture of the top surface of the wood fiber board is responsible for wood fibers.

In order to reduce this problem, in a conventional manner, the wood fiber boards after manufacture are first stored for a defined period of time, in order to establish a uniform distribution of moisture in the boards. However, for different reasons such as, for example, an interruption of the operation of the production facility or overheating periods, operational difficulties can always arise again that do not allow a definite reclimatization of the wood fiber boards for reasons of time. This can then lead to the fact that certain batches of boards can only be processed at a reduced speed or cannot even be processed on the primer and print line. Both cases are associated with increased costs and delays in subsequent processing and delivery to customers.

One approach to solving this problem includes fully air conditioning the storage space, that is, the maturation warehouse for wood fiber boards. However, with storage amounts of several 10,000 m3 of wood fiber boards, this means a considerable increase in costs.

Therefore, a number of disadvantages arise with conventional procedures. The conventional process for direct printing of wood fiber boards depends largely on the weather conditions. In addition, this process does not allow possibilities for reaction in short-term accidents on the fiber board line and there is a reduced quality or insufficient quality below the new description sheet during priming and printing leading to an increase of waste

Therefore, the present invention has the technical objective of solving the described problems with a technical effort as small as possible and being able to continue processing the wood fiber boards also during moisture fluctuations. In addition, it seeks to avoid an increase in costs and, if possible, achieve a reduction in costs.

The stated objective is achieved in accordance with the invention through a procedure with the characteristics of claim 1.

Accordingly, a process for the manufacture of a board of wood-derived material provided with a decorative layer is provided. The present procedure comprises the following steps:

- provide at least one support board for wood fibers,

- moisten at least one section of a surface of the at least one support board of wood fibers with aqueous steam, the aqueous vapor being applied in an amount of 1 to 10 g / m2,

- sand the wetted surface at least by sections of the wood support fiber board and

- apply at least one decorative layer on the surface moistened with at least sections of the wood fiber support board.

Correspondingly, with the present process a process is provided with which a directed damping (vaporizing or spraying) with aqueous steam, preferably water, of support panels of still unrelimited wood fibers is performed. According to the procedure, after the separation of the wood fiber support boards, for example, from a stack of boards, the humidity level of either a part / section or the section is increased before the printing line. Full surface of the wood fiber support board through vaporization or pulverization with aqueous steam. Since the primary objective of the present process comprises wetting the surface of the wood fiber support board, an amount of just a few grams of aqueous vapor per square meter of surface is sufficient. By limiting the amount of

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humidification or vaporization also prevents the occurrence of fiber swells on the surface of the support panels of wood fibers, which could cause a deterioration of the surface or a surface alteration.

This procedure offers essential advantages related to cost reduction, reduction of stored quantities and quality improvement.

As mentioned above, after the dampening installation, a first sander will be placed, so that, if necessary, slight swelling can be eliminated immediately.

In addition, the dampening can be adapted depending on the present problem or the questioning through the interruption of a corresponding program. In this way, through direct disconnection and control maneuvers it is possible to perform a vaporization only in the region of the edge of the wood fiber boards, while with problems on the entire surface, the entire surface of the board can be moistened. wood fibers

The application of an aqueous liquid on wood fibers during the manufacturing process of wood fiber boards is known, for example, through document DE 10 2008 240 B4 or also document DE 10 2008 049 132 A1, there being essential differences with respect to the present procedure.

Thus, in DE 10 2008 240 B4, water is applied on the upper side of a board of wood-derived material in an amount of 10 ml / m2 to 40 ml / m2, which also penetrates into the material board derived from wood. The amounts of water described there are clearly above the amounts used in the present aqueous vapor process, as will be described in more detail below.

In DE 10 2008 049 132 A1 the application of an aqueous liquid is carried out on one side of a raw wood fiber board and at the same time a vacuum is applied on the second side opposite the first side of the fiber board of raw wood, so that the aqueous liquid is absorbed into and / or through the board of raw wood fibers. Such an integral wetting of the raw wood fiber board, for example, can prevent alterations in the dimensions of the fiber boards. However, a complete integral wetting of a fiber board leads to a swelling of the surface of the wood fiber board, which directly opposes a uniform primer and an impression of the wood fiber board.

In one embodiment of the present process, the aqueous vapor, used to moisten at least in sections the surface of the wood-based fiber support board, is composed of at least 95%, preferably at least 98%, especially preferably for 100% water. It is conceivable to add additives to the aqueous vapor to improve the properties of the wood fiber board. For example, biocides or also surface active agents can be added thereto to improve the wetting properties of water vapor. The additives may be added to water vapor or aqueous vapor at 0 to 5% by weight, preferably 0 to 2% by weight.

In addition, it is preferred that the aqueous vapor used to moisten at least in sections the surface of the wood fiber support board has a droplet size of 5 to 50 pm, preferably 10 to 40 pm, especially preferably 20 to 20 30 pm In general, with the present procedure a size of drops of 30 pm is used.

The temperature of the aqueous vapor, in particular of the water vapor, can be up to 60 ° C, with temperatures from 30 to 60 ° C being preferred, in particular from 40 to 50 ° C.

In a further embodiment of the present process, the aqueous vapor is applied, used to wet at least in sections the surface of the wood fiber support board, in an amount of 2 to 8 g / m2, particularly preferably 3 at 5 g / m2. This corresponds approximately to an amount by volume of aqueous vapor of 1 to 10 ml / m2, preferably 2 to 8 ml / m2, particularly preferably 3 to 5 ml / m2.

In accordance with the present process, the surface moistened at least by sections of the wood fiber support board, after the vaporization stage, is subjected to at least one sanding process. During the sanding process, a part of the moistened surface of the wood fiber support board is sanded, although, surprisingly, as will be explained later in the embodiment example, there is a significant improvement in the surface quality of the wood fiber support board, for the subsequent application of the decorative layer. The sanding procedure can be repeated, as many times as desired, after wetting the surface of the wood fiber support board.

In a further embodiment of the present process, the surface moistened at least by sections and, possibly, the sanded surface of the fiber support board derived from the wood is dried, at least partially. Intermediate drying of the wetted and sanded wood fiber support board can be performed, for example, in an IR dryer.

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In a next stage of the present process, at least one layer of resin can be applied to the surface, at least partially moistened, sanded and subsequently dried, of the support board of wood fibers. This resin layer is also called a roller base and serves to improve the adhesion of the primer layer on the support board. The roller base preferably comprises a formaldehldo resin such as, for example, melamine formaldehldo resin, melamine urea formaldehldo resin or urea formaldehldo resin. This resin can be applied once or several times and, correspondingly, can consist of several layers. Preferably, the resin layer (roller bottom), after application, for example, is dried in a convection dryer.

In a further preferred embodiment of the present process, in a next step, at least one primer layer is applied on the at least one resin layer.

The primer layer preferably used in the present process comprises a composition of caselna as binder and inorganic pigments, in particular, inorganic dye pigments. As dye pigments, white pigments such as TiO2 titanium dioxide can be used. Other coloring pigments may be calcium carbonate, barium sulfate or barium carbonate. In addition to coloring pigments such as titanium dioxide and caselna, the primer also contains water as a solvent.

It is also preferred, when the applied pigmented primer layer consists of at least one, preferably two, particularly preferably of at least four layers or applications, applied one behind the other, the amount applied between the layers or applications may be same or different, that is, the amount of application of each of the layers may vary. Thus, the amount of application2 of a layer or an application of the primer layer can be from 1 to 50 g / m, preferably from 2 to 30 g / m, especially preferably from 5 to 15 g / m2 of board of wood fiber support.

The total amount of the pigmented primer layer applied, in particular, in the form of a liquid application, can be from 5 to 200 g / m2, preferably from 10 to 150 g / m2, especially preferably from 20 to 100 g / m2 of wood fiber board.

After applying the primer layer, it is dried in at least one convection dryer. When applying several layers of primer or primer layers, a drying step is carried out correspondingly in each case after the application of the respective primer layer or primer layer. It is also conceivable that after each stage of drying a primer layer, one or more sanding aggregates are provided to sand the primer layers.

In the present, in a further embodiment, in the case of applying at least one layer of primer on the support board, at least one layer of primer, for example, can then be applied thereon. in the form of a UV putty or an electron radiation hardening putty (ERE).

In a further variant of the present process, the at least one decorative layer is applied in the gravure printing process or in the digital printing procedure. In the case of a printing decoration, a water-based pigmented printing color can be applied in the gravure printing procedure or in the digital printing procedure. This water-based pigmented printing color can also be applied in more than one layer, for example, two to ten layers, preferably three to eight layers.

As mentioned, the application of the at least one decorative layer is preferably carried out by means of an analog gravure printing procedure and / or a digital printing procedure. The gravure printing procedure is a printing technique, in which the elements to be represented are present as depressions, in a printing mold that is inked before printing. The printing color is mainly in the depressions and is transferred thanks to the compressive pressure of the printing mold and the adhesion forces on the object to be printed, such as a support board made of wood fibers. On the contrary, with digital printing the print image is transferred directly from a computer to a printing machine, such as a laser printer or an inkjet printer. In this regard, the use of a static printing mold is omitted. In both procedures it is possible to use aqueous colors and dyes or UV-based coloring agents.

It is also conceivable to combine the aforementioned printing techniques of gravure and digital printing. An appropriate combination of printing techniques can be performed, on the one hand, directly on the support board or the layer to be printed, or also before printing by adapting the used electronic data sets.

In a further preferred variant of the present process, at least one wear resistant or coating layer is applied to the at least one decorative layer, which, after application, is subjected to at least one drying stage, for example, in a convection dryer.

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The at least one wear resistant layer can be configured in the most varied way. In a first variant

a) the wear resistant layer comprises natural or synthetic fibers, at least one binder, antifriction particles, pigments and / or at least one additive. In an additional variant b) the at least one wear resistant layer consists of a UV hardening layer and / or an electron radiation hardening protective layer (ERE). According to an additional variant c) the wear-resistant layer can be configured in the form of a heat-hardening protective layer.

Possible individual variants of the wear resistant layer are described in more detail below.

The wear-resistant layer of the variant a) of fibers, binders, particles, pigments and / or additive is applied in the form of a powder on the upper side of the fiber support board, in particular on the decorative layer of the board. fiber support The composition according to a) is composed of 30 to 65% by weight, preferably 40 to 60% by weight, of fibers, 20 to 45% by weight, preferably 30 to 40% by weight, of binders, of 5 to 25% by weight, preferably 10 to 20% by weight, of friction-resistant particles and 0 to 8% by weight, preferably 0.5 to 6% by weight, of additive.

The thickness of the wear-resistant layer a) can be from 0.05 to 10 mm, in particular from 0.1 to 5 mm. In this regard, the wear-resistant layer a) can be divided into an upper layer and a lower layer, the upper layer having a thickness of 0.05 to 7 mm, while the lower layer has a preferred thickness of 0.5 to 3 mm. In particular, a thickness of one of the two layers of 0.7 mm is preferred.

The upper layer may preferably contain an amount of 0 to 1% by weight of the additive, while the amount of the additive in the lower layer is advantageously 0.5 to 5% by weight. It is also conceivable that the bottom layer has no friction-proof particles. The latter are preferably incorporated to increase the wear resistance of the upper surface in the upper layer.

The at least one additive is advantageously selected from the group containing conductive substances, flame retardants, luminescent materials and metals. The conductive substances can be selected, in this respect, from the group comprising hollln, carbon fibers, metal powder and nanoparticles, in particular carbon nanotubes. As flame retardants, phosphates, borates, in particular, ammonium polyphosphate, tris (trichromoneopentyl) phosphate, zinc borate or boric acid complexes of polyhydric alcohols can be used. The use of flame retardants leads to a decrease in flammability and, therefore, is of particular importance with laminate floors, which are used in enclosed spaces with special fire protection requirements or in escape vlas.

As luminescent materials, fluorescent and / or phosphorescent materials are preferably used on an inorganic or organic basis, in particular zinc sulphide and alkaline earth aluminates. Luminescent materials can be applied in geometric shapes through templates on the surface. Through the incorporation of these dyes on the surface of material boards that can be used as floor or wall panels, for example, in enclosed spaces, during a lighting failure, in this way, it is possible to have an indication relative to escape rods and escape direction.

The natural or synthetic fibers used are preferably selected from the group comprising wood fibers, cellulose fibers, partially bleached cellulose fibers, wool fibers, hemp fibers and organic or inorganic polymeric fibers.

A binder which is selected from the group comprising melamine, acrylate and polyurethane resins is advantageously used as a binder.

The friction resistant particles are preferably selected from the group comprising aluminum oxides, corundum, boron carbide, silicon dioxides, silicon carbides and glass spheres.

According to the additional variants b) and c), the wear-resistant layer may also be present as a UV hardening and / or electron radiation hardening (ERE) protective layer or as a heat-hardened resin layer (liquid coating) .

For the variant b) of the present protective layer, radiation-hardened lacquers containing acrylate can be used in particular. The radiation-hardened lacquers used for this purpose generally contain methacrylates such as, for example, polyester (meta) acrylate, polyether (meta) acrylate, epoxy (meta) acrylate or urethane (meta) acrylate. It is also conceivable that the acrylate used or the lacquer containing acrylate has substituted or unsubstituted monomers, oligomers and / or polymers, in particular in the form of monomers, oligomers or acrylic acid polymers, acryl and / or acrylic acid esters. The acrylates mentioned allow an interconnection in the presence of UV rays or electron rays in the hardening or drying process.

In one embodiment, more than one radiation-hardened protective layer is preferably applied,

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preferably two or three radiation-hardened protective layers that in each case are arranged or applied on top of each other. The at least one radiation-hardened protective layer may also contain chemical interconnects, for example, on an isocyanate basis, through which the interadherence of the individual layers disposed one upon another is increased.

In the radiation-hardened wear-resistant layer that is disposed on the printed decorative layer, the above-mentioned wear-resistant particles, fibers and additional additives, such as flame retardants, conductive substances and / or luminescent materials, can be added.

The heat-hardened resin layer, used as a wear-resistant layer according to variant c) preferably comprises a resin containing formaldehyde, in particular, a melamine formaldehyde resin and / or a melamine urea formaldehyde resin. As the aforementioned additional variants of the protective layer, the heat-hardened resin layer may also contain wear-resistant particles, natural and / or synthetic fibers and additional additives. Such a layer of heat-hardened resin is also called liquid coating. Several layers of heat-hardened resin can also be used, which are arranged one on top of the other and correspondingly applied one after the other. In addition, wetting agents and separating agents are employed in such a liquid coating layer of a preferred embodiment. A process for manufacturing the liquid coating layer described is described in EP 233 86 93 A1.

The wood fiber board provided with a wear-resistant layer or coating layer of variant a (powder), variant b (UV layer or electron-radiation-hardened layer) and variant c (liquid coating layer) are it can also provide a 3D printer structure, preferably printing the surface structure in a short-rhythm press optionally synchronized with the decoration. The 3D structure is preferably printed or pressed by appropriate printing structures. Structures can be made using structured lacquered rollers, structured calenders or other structured printing plates.

The at least one wood fiber support board is selected from the group comprising chip boards, high density wood fiber board (HDF), medium density wood fiber board (MDF), OSB board and WPC board . The board of material derived from wood used as a support board has a maximum apparent density of 1400 kg / m3, preferably 1200 kg / m3, a minimum apparent density of 750 kg / m3, preferably 800 kg / m3, and a average apparent density of 850 kg / m3.

In this way, the present process makes it possible to manufacture a board of wood-derived material with layer structure as follows: wood fiber support board - resin layer (roller bottom) - primer layers - layer of primer - decorative layer - wear resistant layer. Each of these layers can be present in several layers. In this regard, it is generally possible, for example, that several layers of primer and one layer of primer are present. On the back side of the wood fiber support board, a counter-traction paper and additional layers of acoustic insulation can be applied.

The present process for manufacturing a board of wood-derived material is performed on a device or a production line comprising at least one device for moistening at least a section of a surface of at least one support board of wood fibers with aqueous vapor and at least one device for applying at least one decorative layer on the surface moistened at least by sections of the wood fiber support board, at least one application device being arranged in the processing direction after the wetting device.

In a variant of the present invention, the wetting device makes possible an application of water spraying, possibly with additives in aqueous solution or dispersion, an automatic adaptation of the amount of spray at speed and automatic cleaning cycles. The spray liquid is applied with a temperature up to 60 ° C, a pH value of 2 to 8 and a viscosity up to 200 mPas. The spray widths that can be achieved with the wetting device or the spraying device range from 180 to 5,700 mm and the spray amounts are from 10 to 4,000 ml / (mmin), that is, up to 10 ml / m2 with an advance of 400 m / min.

In order to carry out the present process it is also advantageous that at least one sanding device is provided in the production line for sanding the surface moistened at least by sections of the fiber support board derived from the wood. In this regard, the at least one sanding device is arranged in the processing direction after the wetting device.

In a further variant, the present method comprises a device for applying a resin layer (roller bottom) on the moistened and sanded support board and a device for drying the resin layer (for example, in the form of a convection dryer ), both devices being arranged in the processing direction behind the wetting device and the sander.

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In a further embodiment, the present device comprises at least one device for applying a pigmented layer such as, for example, a primer layer on a support board and a device that is then connected to this application device for drying the primer layer, such as a convection dryer. As required, more than one primer layer can be applied, so that more than one application device for the primer layer can be provided on the production line with a respective convection dryer connected below. The number of application devices for the primer layer with convection dryer connected below can vary as much as is preferred and easily adapts to the predetermined production conditions.

In a further embodiment variant of the present production line, at least one application device for a primer layer with convection dryer connected next is connected to the application device for the primer, followed by at least one application device, preferably , two to three application devices for the decorative layer and at least one application device connected at the end for a coating or anti-wear layer with convection dryer included.

The application devices for the different layers to be applied can be configured in the form of a roller, spray device or watering device and the respective drying devices arranged after the application devices can be present in the form of a convection dryer, a IR dryer and / or an NIR dryer.

In a preferred embodiment, the structure of a production line looks as follows:

a) at least one moistening device for moistening at least a section of a surface of a wood fiber support board with aqueous vapor;

b) at least one sander machine for sanding the surface of the surface moistened with at least sections of the wood fiber support board and at least one IR aggregate arranged in the direction of processing behind the sander machine (the IR aggregate serving particularly to generate a preset minimum surface temperature and to match the surface temperature);

c) a first application device for applying at least a first layer of resin (roller bottom) on the wood fiber support board;

d) a first drying device (for example, convection dryer) arranged behind the first application device in a processing direction to dry the at least a first layer of resin (roller bottom);

e) a second application device disposed behind the first application device in the direction of processing to apply at least one primer layer on the wood fiber support board, the second application device comprises at least one application mechanism, preferably two, especially preferably four application mechanisms;

f) a second drying device arranged behind the second application device in the processing direction (eg, convection dryer) to dry the at least one primer layer;

g) a third application device arranged behind the second drying device for drying the at least one primer layer in the direction of processing to apply at least one primer layer on the wood fiber support board;

h) a third drying device (for example, convection dryer) arranged behind the third application device in the direction of processing to dry the at least one layer of primer;

i) a fourth application device arranged behind the third drying device for drying the primer layer in the direction of processing to apply at least one decorative layer, in which the fourth application device may comprise several rollers for gravure printing (for example, three or four printing rollers);

j) a fifth application device arranged behind the fourth application device to apply the decorative layer in the direction of processing to apply at least one protective layer; Y

k) a fourth drying device (for example, convection dryer) arranged behind the fifth application device to apply the at least one protective layer in the direction of processing to dry the at least one protective layer.

The application devices to be used in a preferred manner are application rollers that make it possible to apply the layers on the upper side of the boards of wood-derived material.

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Depending on the requirements of the manufacturing line, it is understood that it is possible to vary the amount of application devices and drying devices. Thus, for example, it is conceivable and possible to use a production line of two units comprising an application device and a drying device or also more than two such as, for example, three, four or five units of a device application and a drying device.

The invention will be explained in more detail below with reference to the figures of the drawings in an example of realization. In the drawings:

Figure 1 shows a schematic representation of a production line of a board of wood-derived material applying the procedure according to the invention.

The present procedure is described with reference to the example in a printing installation that is schematically represented in Figure 1.

In the printing installation high density fiber boards 2.07 m wide and 2.80 m long, with board thickness of 6 to 12 mm, with up to 85 m / min are processed. The raw boards of high density fibers are first vaporized individually and in a 1A humidifying device with 3.5 g of water vapor / m2 and a droplet size of approximately 30 pm.

After wetting, the wetted surface is sanded in a sander 1. After sanding, the boards are preheated in an IR dryer 2 at a temperature of approximately 45 ° C.

Next, a first resin application (roller bottom) is made in the first application mechanism 3 with subsequent drying through hot air in a convection dryer 4. As the coating resin, an aqueous melamine formaldehyde resin is used with a solids content of 60% by weight.

Then, an aqueous white primer based on caselna and inorganic pigments is applied with the help of four application mechanisms 5 and dried with hot air after each application in a convection dryer 6. The individual application mechanisms 5 apply variable amounts of primer. The total amount of white application varies depending on the printing requirements of 20 g / m2 to 30 g / m2.

Following is an application of primer 7 with subsequent drying in an additional convection dryer 8. The impression 9 (decoration) of the boards in indirect gravure printing follows. After printing, the boards are coated with melamine formaldehyde resin 10 (protective layer) and also dried in a convection dryer 11. The boards are then stored temporarily for a few days before further processing.

The priming process is particularly important, since it has an essential influence on the color printing quality of the boards coated with high density fibers. For a given color pattern, the most constant amount of white application must also be guaranteed, since otherwise different levels of primer clarity can occur and, thus, different colors within the color pattern in several boards

Execution Example

High-density fiber boards of large format (2,500 mm x 2007 mm x 7 mm) were separated from a stack and with a production speed of 85 m / min they were subjected to a primer and a decorative impression. In this regard, after a cleaning sanding, a transparent primer based on a duroplastic resin was first used (amount of application: approximately 20 g of liquid / m2). After an intermediate drying with hot air, a pigmented primer with caselna was then applied as a binder. The application of the pigmented primer was repeated four times after an intermediate drying. The total amount of application was approximately 25 g of liquid / m2. After an additional primer application (application amount: approximately 10 g of liquid / m2) the decorative impression was made in the gravure printing procedure.

After the decorative impression, defective places caused by an uneven primer were observed. In particular, they were observed in the front and rear region of the board in the forward direction. In these defective places, the uncoated primer could be observed under the microscope. In order to eliminate these defective places, after the separation of boards, a dampening of the affected parts of the boards was carried out, for example, with a rotary sprinkler system (Rotor Spray System) of the firm Ahlbrandt. The "application amount" was placed in approximately 3.5 g of water vapor per square meter. The size of drops stood at approximately 30 pm. The control of the gate system in the dampening system was carried out through photocells.

The wood-derived fiber boards after printing presented less defective locations (fewer regions without printing) which were also less marked than in the standard board. An analysis of the defective places with the help of a software should confirm the result obtained visually. As a result, it was obtained that the percentage of the region without printing stood at 7.17% for the standard board. In 5 the board of moistened wood fibers, the region without printing was only at just 6.18%.

This is surprising, since with the cleaning sanding, the previously moistened surfaces are re-sanded and the time of operation of the water fog on the surface of the boards is only about 5 seconds.

10

In an additional test the same amount of water was applied after sanding. In this regard, an unprinted surface of 9.71% was determined. In this sense, wetting before sanding is surprisingly effective.

fifteen

Claims (15)

5 10 fifteen twenty 25 30 35 40 Four. Five fifty 55 60 65 1. Procedure for manufacturing a board of material derived from wood, in particular a board of material derived from wood provided with a decorative layer, comprising the following steps: - provide at least one support board for wood fibers, - wet with aqueous steam at least a section of a surface of at least one support board of wood fibers, applying the aqueous vapor in an amount of 1 to 10 g / m2, - sand the wetted surface at least by sections of the wood fiber support board and - apply at least one decorative layer on the surface moistened with at least sections of the wood fiber support board. 2. Method according to claim 1, characterized in that the aqueous vapor, used to moisten at least the sections of the surface of the wood fiber support board, is composed of at least 95%, preferably at least 98 %, especially preferably 100% water. 3. Method according to claims 1 or 2, characterized in that the aqueous vapor, used to moisten at least in sections the surface of the wood fiber support board, has a droplet size of 5 to 50 pm, preferably of 10 to 40 pm, especially preferably from 20 to 30 pm. 4. Method according to one of the preceding claims, characterized in that the aqueous vapor, used to moisten at least the sections of the surface of the wood fiber support board, is applied in an amount of 2 to 8 g / m2, especially preferably from 3 to 5 g / m2. 5. Method according to one of the preceding claims, characterized in that after the wetting stage the surface moistened at least by sections of the wood fiber support board is dried at least partially. Method according to one of the preceding claims, characterized in that at least partially a resin layer is applied to the sanded and at least partially moistened surface of the wood fiber support board. 7. Method according to claim 6, characterized in that at least one layer of resin is applied to the at least one layer of resin. 8. Method according to claim 7, characterized in that at least one primer layer is applied on the at least one primer layer. Method according to one of the preceding claims, characterized in that the at least one decorative layer is applied in the gravure printing process or in the digital printing process. 10. Method according to claim 9, characterized in that at least one wear resistant layer is applied to the at least one decorative layer. Method according to one of the preceding claims, characterized in that the at least one wood fiber support board is selected from the group comprising chip boards, high density wood fiber board (HDF), wood board. medium density wood fibers (MDF), OSB board and WPC board. 12. Device for carrying out a method according to at least one of the preceding claims, comprising - at least one device for wetting with aqueous steam at least a section of a surface of at least one support board of wood fibers, - at least one sanding device for sanding the wetted surface at least by sections of the wood fiber support board, which is arranged in the processing direction after the wetting device, and - at least one device for applying at least one decorative layer on the surface moistened with at least sections of the wood fiber support board. 13. Method according to claim 12, characterized in that the damping device is configured as a spraying device. 14. Method according to claims 12 or 13, characterized by at least one device for applying at least one layer of primer. 15. Device according to one of claims 12 to 14, characterized by at least one device for applying the decorative layer.