EP2274176B1 - Derived timber plate provided with a high-gloss laminate coating, and method for producing such a derived timber plate - Google Patents

Description

The invention relates to a method for producing a wood-based panel having a high-gloss laminate coating, in which at least one flat, broad surface of a chipboard is ground before the application of the laminate coating, and a chipboard provided with a high-gloss laminate coating.

Various processes are available for the coating of wood-based materials. In the field of furniture and interior design, in addition to liquid coating with paints and varnishes, film lamination and powder coating, coating with laminates is common.

With regard to the laminate coating, in turn, different methods are known. These processes typically use multiple layers of paper impregnated with synthetic resin, usually melamine resin, melamine-urea resin or phenolic resin. The paper layers can be freely designed in their color and printed with any desired decors such as wood decors or fantasy decors. At elevated pressure and temperature, these paper layers are then pressed either directly (Direct Pressure Laminate (DPL)) or only after their processing into a so-called laminate with the wood-based panel (High Pressure Laminate (HPL) or Continuous Pressure Laminate (CPL)).

To improve the wear resistance of the laminate coating, an overlay paper, which may additionally be provided with hard particles, for example with corundum particles, may optionally be provided. Through the use of laminates, wood-based panels with very resistant surfaces can be achieved. However, this type of laminate coating is more expensive than the direct coating (DPL technology) due to the two pressing steps required and thus causes higher costs. For most applications of wood-based materials used in furniture and interior design, panels are those produced by direct coating are finished, sufficiently wear-resistant. There are usually used for this with melamine resin impregnated papers.

Laminates and coatings based on DPL technology are usually produced in cycles with single and multi-day presses or continuously with double belt presses. Generic for the present invention is the DE 2006781 ,

High-gloss surfaces have recently become increasingly popular in the field of furniture and interior design.

In order to achieve particularly high-gloss laminate coatings, it has hitherto been necessary to recool after pressing. This means that after the actual pressing step at high pressure and high temperature a rapid lowering of the temperature - while maintaining the pressing pressure - is required. Furthermore, high-gloss press plates or appropriate allowances are required. This understandably requires specially designed pressing devices and is also possible only with high energy consumption. In order not to pollute the particularly high-quality surfaces of the press plates or supplements, clean room conditions must be fulfilled. Accordingly, the handling of the various pressing tools must be done with the utmost cleanliness. Fingerprints or dust grains on the surfaces of the press plates or additives can lead in the shortest possible time to laminate coatings that do not meet the requirements of a first choice or are even unsaleable as a committee.

Gloss is an optical property of light-reflecting surfaces. Physically, gloss is defined as the quotient of the directed and the diffusely reflected portion of the amount of light falling on a surface. It can be quantitatively determined with gloss meters; Details are given in the standards DIN 67530 and ISO 2813 respectively. For directly coated panels, the determination of the degree of gloss is specified in EN 14323 (current edition 2004-06-01). Then the degree of gloss is to be determined with a so-called reflectometer according to ISO 2813. The principle of the reflectometer is based on the measurement of the directed reflection. For this purpose, the intensity of the reflected light is measured in a narrow band of the reflection angle. The measurement results are not related to the amount of light emitted, but instead on a black, polished glass standard with a defined refractive index (1.567). For this standard, the measurement value = 100 gloss units (GE or gloss grade points) is set. There are material surfaces that have a higher refractive index than the black glass standard used for calibration. Therefore, gloss levels of more than 100 GE may arise for certain material surfaces, for example in polished metals. For a better differentiation of the measured values one measures depending on the gloss with different measuring angles. According to the ISO 2813 standard, for high-gloss surfaces (≥ 70 GE), in addition to the conventional measurements with a 60 ° measuring geometry, measurements with a 20 ° measuring geometry must also be carried out. However, the values given below refer exclusively to measurement results obtained with a 60 ° measuring geometry.

The DE 1 198 540 B discloses a method for smoothing, calibrating and optionally conditioning wood chipboards, in which, after grinding the surfaces, they are moistened with water on one or both sides and then again subjected to the action of heat and pressure. With the method, thickness differences in the order of a few tenths of a millimeter can be largely irreversibly compressed by a hot pressing with simultaneous plasticization by steam. As a device for the practice of this method, hot plate presses, belt presses, roller presses and roller presses are proposed. The DE 1 198 540 B However, it does not deal with the production of wood chip boards that have a high-gloss laminate coating.

The present invention has for its object to provide a method for coating chipboard, can be provided with the high-gloss laminate surfaces having chipboard cost. In particular, the invention has for its object to provide a provided with a high-gloss laminate coating wood material panel that can be produced inexpensively.

This object is achieved by a method having the features of claim 1 or by a wood-based panel having the features of claim 15. Preferred and advantageous embodiments of the invention are specified in the subclaims. The inventive method in which a chipboard having at least one flat broad surface is ground on this broad surface as the wood-based panel is characterized by the steps of cutting the smooth, flat, broad surface by compacting it by means of a cylindrical or plate-shaped smoothing body whose smoothing surface is tempered to at least 100 ° C or has a temperature of at least 100 ° C, and coating the smoothed broad surface by pressing a high-gloss laminate coating in the form of a direct coating. Furthermore, in the method according to the invention as a wood-based panel a chipboard is used which has layers of different chip thickness distribution, with a middle layer in which the maximum of the chip thickness distribution in the range of 1.0 mm to 4.0 mm, and cover layers, in which the maximum the chip thickness distribution is in the range of 0.1 mm to 0.8 mm at a chip thickness, wherein the proportion of chips having a thickness of less than 0.6 mm in the chip material of the cover layers at least 75 wt .-%, in particular at least 80 wt. -%, and preferably at least 90 wt .-% is.

The wood-based panel according to the invention, which is formed from such chipboard, is accordingly provided with a glossy laminate coating, which is applied as a direct coating on a chipless smoothed broad surface of the chipboard and a gloss level of at least 105, in particular at least 110 and preferably measured at least 115 gloss units according to ISO 2813 with a 60 ° measuring geometry.

By a high-gloss laminate coating in the sense of the present invention is meant a laminate coating applied as a direct coating, based on at least one flat broad surface of the wood-based panel over its entire area or in an area fraction of at least 80%, preferably at least 90%, particularly preferably at least 95% of 1 m ² large flat broad surface of the wood-based panel has a gloss level of at least 105 gloss units measured according to ISO 2813 with a 60 ° -Meßgeometrie.

Applicants have recognized that wood-base panels with high-gloss laminate coatings can be produced cost-effectively if the relevant broad surface of the wood-based panel is smoothed after sanding and before coating (pressing on melamine resin-impregnated paper layers). In contrast to conventional grinding, smoothing takes place without chip removal. It is thereby effected by contact with a smooth, tempered surface that the after grinding out of the surface protruding wood fibers or chips plasticized and flattened. This is achieved on the one hand, that small elevations, which have previously formed the wood fibers or wood chips on the plate surface, are largely eliminated, so that no more such elevations are embedded in the applied resin layer, on the other hand results from the smoothing a regular compression of the surface , which causes the coating resin to form a uniform film over the surface. Both circumstances cause a significant improvement in the gloss level of the finished coated plate.

The chipless smoothing of the ground, flat broad surface of the wood-based panel by means of a tempered smoothing body can be carried out both cyclically and continuously in the method according to the invention. However, for smoothing wood boards of different lengths and to minimize the energy required for smoothing the smoothing of the ground wide surface of the wood-based panel is preferably continuous, for example, with a smooth, tempered roller. When using the method according to the invention, a roller used as a smoothing element should be pressed onto the broad surface to be smoothed with a force in the range of 200 to 1000 N / cm plate width, preferably in the range of 450 to 750 N / cm plate width. The non-cutting smoothing is carried out with one or more rollers arranged one behind the other.

It is also proposed that the smoothing surface of the smoothing body is heated to a temperature in the range of 150 ° C to 240 ° C, preferably in the range of 180 ° C to 230 ° C.

Experiments with rolls tempered at 200 ° C., which were pressed onto the board from above and below with a force of approximately 350 N / cm plate width, gave markedly smoother and more closed surfaces than the merely ground plates. For comparison, 88 gloss points were achieved in tests on non-smoothed plates, while in the case of such smoothed and similarly coated plates, in particular 106 gloss grades were achieved.

The peripheral speed of the tempered roller can correspond to the feed rate of the wood-based panel to be smoothed. The tempered roller can be used in particular at the same time as a transport roller for advancing the wood-based panel. In an advantageous embodiment of the method according to the invention, a relative movement between the plate-shaped or roller-shaped smoothing tool and the broad surface of the wood-based material board to be smoothed can also be carried out for smoothing the ground wood-based panel. As a result, the effect of the smoothing tool can be increased. When using a tempered smoothing roll this is rotated in this process variant with a peripheral speed which is greater or less than the feed rate of the wood-based panel to be smoothed, so that between the smooth tempered contact surface (peripheral surface) of the roller and the thus in contact, to be smoothed Surface of the wood-based panel results in a slip.

The tempering of the smoothing or the smoothing roll does not have to be done by supplying heat energy or the like. Rather, it is also within the scope of the invention, to cause the tempering of the smoothing surface of the smoothing or the smoothing roll by friction between the smoothing body and the broad surface to be smoothed. The caused by appropriate friction temperature of the smoothing surface is at least 100 ° C, preferably at least 150 ° C.

A further advantageous embodiment of the method according to the invention is characterized in that the temperature of the smoothing surface of the smoothing body or the temperature of the smoothed broad surface of the wood-based panel is measured, that the measured temperature is compared with a predetermined target temperature, and that the relative speed between the smoothed Wide surface and the smoothing surface of the smoothing body and / or the force with which smoothing body is pressed against the flat surface to be smoothed, is controlled depending on the measured temperature. In this way, the desired smoothing of the wood-based panel can be achieved particularly reliable and automated.

The use according to the invention of the DPL technology (direct coating) for applying a high-gloss laminate coating to a chipless smoothed broad surface of the wood-based panel offers the above-mentioned procedural and economic advantages compared to an application of the HPL technology.

The rapid recooling required with conventional methods for producing high-gloss laminate coatings wood-based panels while maintaining the pressing pressure is not required in the inventive method. The method according to the invention thus also offers cost advantages to that extent. For the construction and control of a coating press required for carrying out the method according to the invention is easier and their throughput higher than the throughput of a coating press whose pressing tools are provided with a cooling device. According to a preferred embodiment of the method according to the invention, the pressed onto the wood-based panel high-gloss laminate coating is therefore not subject to forced cooling in the press.

The inventive method is particularly advantageous in the use of chipboard, since these are much cheaper to manufacture than MDF boards, on the other hand, are generally better suited for the direct coating with a high-gloss laminate material as chipboard. Strictly speaking, the method according to the invention only creates the prerequisite for being able to produce cost-effective chipboard with a high-gloss laminate coating pressed in by the direct coating method.

Another advantage of using chipboard compared to the use of MDF boards is that grinding of the chipboard is possible immediately after pressing and a brief cooling (about 10 to 20 minutes). On the other hand, after hot pressing, MDF boards are stored for 2 to 5 days in a maturing warehouse before they can be sanded and then further processed. This circumstance is detrimental to the production logistics as well as to the manufacturing costs due to the need for corresponding storage capacities and the longer capital tie-up in the maturing warehouse.

In tests, multilayer particle boards were produced with an increased proportion of relatively fine cover shavings. By adding, for example, 5 to 7% more top layer chips compared to chipboard, which in cross-section about 60% coarser middle-layer chips and about 2 x 20% finer cover shavings have, otherwise the same binder dosage and the same plate thickness, was achieved that less large chips came to lie on the surface. The surfaces of this chipboard having an increased proportion of cover shavings were particularly smooth and closed after smoothing. In the finished coated panels, a further increase in the gloss level of at least 3 gloss grades was achieved.

When carrying out the method according to the invention, it is preferred that a chipboard is produced or used as a wood-based panel, the layers having different chip length distribution, with a middle layer, in which the maximum of the Spanlängenverteilung between 8 mm and 15 mm, and outer layers, in which the maximum of span length distribution at a span length between 3 mm and 8 mm, wherein the proportion of chips with a length of less than 6 mm in the chip material of the outer layers is at least 75 wt .-%, in particular at least 80 wt .-% and preferably at least 90 wt .-%.

Experiments have shown that it is favorable for achieving a smooth as possible surface and a high gloss level of the laminate coating when using three-layer chipboard, when according to a preferred embodiment of the method according to the invention a chipboard is used, in the chip material of which the proportion of chips with a thickness of less than 0.6 mm at least 50 wt .-%, in particular at least 65 wt .-% and preferably at least 80 wt .-% is. In particular, it is also advantageous if a chipboard is produced or used for carrying out the method according to the invention, in the chip material of the proportion of chips having a length of less than 8 mm at least 50 wt .-%, in particular at least 65 wt .-% and preferably at least 85 wt .-% is.

Particularly good results were also achieved in experiments in which only sawdust was used as cover shavings, which provided as compared with conventionally prepared wood chips, which may sometimes have minor pollution and bark components, largely free of foreign substances can be. The surfaces of these coverings containing only sawdust were particularly smooth and uniform. In the finished coated chipboard thus produced, a further increase in the gloss level was found.

The binder content was not varied in the experiments, but this is necessarily higher with increasing proportion of relatively fine cover shavings, since the cover shavings have a higher binder content than the coarser middle-layer shavings. Nevertheless, it can be expected that an increase in the binder content in the cover layer by, for example, 3% based on the absolutely dry mass of chips (ie, span span) causes an increase in the gloss level by at least 3 points (gloss units).

In carrying out the process according to the invention, preference is given to the binder fraction in the cover layers of the wood-based panel being at least 10% by weight, in particular at least 12% by weight, based on the absolutely dry composition of the cover shavings, and preferably in the range from 15 to 25% by weight. % lies.

The grinding of the wood-based panels, preferably chipboard is carried out in the inventive method usually in at least three stages. The grains in the different stages are coordinated. It has been recognized that a very fine final finish, for example, with a grain size of 180, brings no additional improvement. Smoothing therefore offers the advantage that it is possible to dispense with the use of particularly high-quality ground plates. According to a preferred embodiment, it is therefore provided that the broad surface of the wood-based panel to be smoothed is ground in a number of stages before the chipless smoothing, wherein the final cut is carried out with a grain size of a maximum of 180, preferably a maximum of 120.

A further preferred embodiment of the method according to the invention is that the wood-based panel is moved along a grinding tool, wherein the flat surface to be smoothed before the chipless smoothing additionally by at least one cross-section relative to the direction of movement of the wood-based panel along the Grinding tool is ground. This makes it possible to achieve a further improvement in the gloss level of the finished laminate-coated wood-based panel.

According to a further advantageous embodiment of the method according to the invention, it is provided that the broad surface of the wood-based material board to be smoothed and / or the smoothing surface of the smoothing body are wetted before smoothing. In this way, the desired smoothness of the wood-based panel can be further improved, with the result that the gloss level of the high-gloss laminate coating of the chipboard increases on average by a further three gloss units. The reason for this increase in gloss level can be seen in the fact that the moisture applied by the wetting is evaporated when smoothing, which then causes an improved heat transfer and / or that the wetted surface of the chipboard is better plasticized or deformable in the short term, so that projecting fibers and / or chips can be embedded even better in the structure of the chipboard.

Fig. 1

ein Ausführungsbeispiel des erfindungsgemäßen Verfahrens in Form eines schematischen Ablaufschemas; und

Fig. 2

einen Abschnitt einer erfindungsgemäßen Holzwerkstoffplatte in Querschnittdarstellung.

The invention will be explained in more detail by means of examples with reference to the accompanying drawings. Show it:

Fig. 1

an embodiment of the method according to the invention in the form of a schematic flow chart; and

Fig. 2

a section of a wood-based panel according to the invention in cross-sectional view.

By shredding solid wood in the form of logs and branches, wood chips are first produced. From the so produced chips and / or other shredded wood residues wood chips are produced. The cutting takes place in the state of the respective moisture content of the wood, which, depending on the origin of the wood and the season can be between 60 and 150% based on the wood dry matter. Subsequently, the wood chips are dried to a humidity in the range of about 1.5 to 3% and fractionated by screening or other suitable classification method, for example by air classification, according to cover layer and middle layer material.

For the middle layer chips used, the maximum of the chip thickness distribution is in the range of 1.0 mm to 4.0 mm. In the case of the cover shavings used, on the other hand, the maximum of the chip thickness distribution is in the range of 0.1 mm to 0.8 mm for a chip thickness. Furthermore, the proportion of chips having a thickness of less than 0.6 mm in the chip material of the outer layers is at least 75 wt .-%, preferably at least 80 wt .-%.

Before or after screening (classification), the wood chips are cleaned of foreign matter such as metal particles and / or stone particles. For this purpose, the wood chips are moved or guided along by electromagnets. The separation of stone particles by means of a density sorter, for example by means of an air classifier or in a downpipe, in which the falling wood chips are deflected by means of a fan laterally, while the relatively heavy stone particles are not or less distracted and thus separated from the wood chips.

The wood shavings are subsequently glued separately after covering shavings and middle layer shavings with binder. The binders used are preferably urea resin and / or phenolic resin. Hardeners, water repellents (paraffin) and optionally additives (e.g., fungicides and flame retardants) are added to the binder. The wood chips are glued by means of a mixer or a spraying device. The wood chips receive a very fine binder coating.

The glued topcoat chips have a binder content in the range of 15 to 25 wt .-%, based on the absolutely dry Spanmasse.

After gluing, the wood chips are scattered by means of a spreader into a multi-layer chip cake substantially mirror-symmetrical about the middle of the board. Preferably, a three-layered chip cake is produced consisting of a lower covering layer of fine chips, a middle layer of coarser chips and an upper covering layer of fine chips (cf. Fig. 2 ).

By hot pressing the chip cake, a stable chipboard is pressed under the action of pressure and temperature, by curing the binder, which can meet the requirements of the European standard 312-3.

The hot pressing of the chip cake can be done in a single-storey or multi-daylight press (cycle press). For this purpose, the continuously scattered chip cake is cut to length by means of cutting tools. Preferably, however, the hot pressing of the chip cake takes place in a continuous double-belt press (so-called "conti-roll press"). The length distribution of the chip cake is in this case only after the pressing process.

Preferably, the initially still relatively loose chip cake before the actual pressing in a press with low pressure precompressed (pre-pressed). An advantage of pre-compaction is that the heat in the main press or the end section of the press reaches the central chips more quickly, so that a more uniform heating of all the chips and thus optimum setting of the binder is achieved. The precompression is optionally carried out under the action of heat, wherein the contact surfaces of the press, for example, to a temperature of about 50 ° C are heated.

In the main press or in the end section of the double belt press, the chip cake is subjected to a temperature of more than 200 ° C. and a pressure of, for example, about 25 kg / cm ² . Due to the high heat in the press, the binder is activated and binds off.

Behind the double belt press, the endless chipboard is cut to length into individual plates of specified length. In combination with the cutting to length preferably trimming of the chipboard, so that it receives straight, mutually perpendicular edges. The trimming is done for example by means of mutually parallel circular saws. Subsequently, a cooling of the individual chipboard is provided. The cooling of the chipboard is preferably carried out in a so-called Sternwender in which the chipboard spaced from each other about an axis of rotation of the Sternwenders be moved, wherein the particle boards are carried by radially projecting from a rotating body of the Sternwenders handrails. The for the cooling of the chipboard provided time period is in the range of about 10 to 30 minutes, preferably in the range of about 10 to 20 minutes.

Subsequently, the chipboard are ground, wherein at least one broad side of the respective chipboard is ground. Preferably, however, both broad sides of the respective chipboard are ground. The grinding of the chipboard takes place by means of at least one cylindrical grinding machine and / or by means of at least one wide-belt sanding machine. The cylindrical grinding machine has a cylinder rotating about its longitudinal central axis, on the lateral surface of which sandpaper is attached. In contrast, the wide-belt sanding machine has an endless sanding belt which runs over several rollers, wherein between at least two of the rollers a pressure plate is arranged which presses the endless sanding belt against the wide surface of the chipboard to be ground.

For carrying out the method according to the invention, it is preferred that the grinding of the chipboard takes place by means of at least one wide-belt sanding machine.

The grinding of the respective broad side of the chipboard takes place in several stages, starting with a relatively coarse grain, for example a 40 grain. For the subsequent grinding operations, abrasive papers or abrasive belts with a finer grain size are used. The final touch is made with a grain size of a maximum of 180, preferably a maximum of 120.

In addition to the grinding process, which takes place in the direction of movement (transport direction) of the wood material board along the wide-belt sander or cylindrical grinding, preferably at least one transverse to the direction of the endless abrasive belt or transverse to the direction of movement of the wood-based panel acting grinding (transverse grinding) is provided. Due to the cross-section, the grinding result can be significantly improved. In particular, can be reduced by the transverse grinding, the resulting amount of grinding dust for a given number of grinding operations.

Following the sanding of the wood-based panel, it is temporarily stored for maturing. During this intermediate storage, the wooden material board adapts to the Humidity of the environment. The intermediate storage, which serves to mature the wood-based panel, takes 2 to 4 days.

The ground, flat broad sides of the chipboard are then smoothed by compacting by means of at least one smoothing device without cutting. The smoothing device comprises at least one cylindrical or plate-shaped smoothing body whose smoothing surface is tempered. For this purpose, the smoothing element is pressed against the broad side of the chipboard to be smoothed.

Rollers of metal are preferably used for smoothing, the polished shell surfaces are tempered to at least 150 ° C, for example to about 200 ° C and with a force in the range of 450 to 750 N / cm plate width from the top and bottom against the wood-based panel be pressed. In corresponding experiments, significantly smoother and more closed plate surfaces were obtained than those of only ground plates. The non-cutting smoothing preferably takes place with a plurality of rollers arranged one behind the other in the feed direction of the wood-based panel.

The thus smoothed broad surfaces of the wood-based panels are then provided with a high-gloss laminate coating, which is pressed as a direct coating on the respective smoothed broad surface. The direct coating of the wood-based panels takes place cyclically. The high-gloss laminate coating may have a wood decor, stone decor, fantasy decor or a patternless, plain decor (Unidekor).

According to the inventive method prepared in experiments, provided with a high-gloss laminate coating according to the DPL technology wood-based panels, especially chipboard, had a gloss of at least 105 gloss units (gloss grades), each measured according to ISO 2813 with a 60 ° -Meßgeometrie. In particular, high-gloss laminate-coated chipboards were obtained which had a gloss level of more than 110, in particular more than 115 gloss units.

In Fig. 2 a section of a wood-based panel according to the invention is sketched, in which it is a chipboard with the properties described above Spanlängen- and / or Spandickenverteilung is. The transition from the middle layer 1 to the cover layers 2, 3 of the chipboard is marked by dashed lines. The ground and then non-cutting smoothed broad surfaces of the chipboard are provided with high-gloss laminate coatings 4, 5.

In Fig. 1 the main steps and some preferred optional steps of the method according to the invention in the form of a flow chart are shown schematically. Accordingly, a chipboard having the above-mentioned chip length and / or chip thickness distribution characteristics is first selected or manufactured. At least one or both flat broad surfaces of the wood-based panel are then ground in one or more stages. The ground wide surface is freed from grinding dust and wetted before the subsequent chipless smoothing. For wetting, for example, water can be used. However, it may also be advantageous to use a solution or emulsion as a wetting agent. For this purpose, the wide surface to be smoothed and / or the smoothing surface of the smoothing body can be wetted accordingly. Furthermore, the invention provides, if appropriate, to add to the wetting agent one or more additives which can further improve the smoothness effect, or also to achieve an improved bonding of the subsequently applied laminate coating to the surface of the wood-based panel. In this way, also a saving of impregnating resin can be achieved.

The wetting can be done very simply by spraying, preferably by producing a fine spray before the smoothing device, in particular smoothing roll. Even very small amounts of moisture or wetting agent are sufficient to achieve an improvement in the smoothness effect. Preferably, the amount of wetting agent applied is in the range of 2 to 20 g / m ² , preferably in the range of 2 to 10 g / m ² .

After wetting, the ground wide surface of the wood-based panel is smoothed by compacting the same chipless. For this purpose, preferably a smoothing roll is used, the smoothing surface has a temperature of at least 100 ° C. The tempering of the smoothing roll or of the smoothing element takes place, for example, by activation of heating elements integrated in the smoothing element or results from the friction between the smoothing surface of the smoothing element and the broad surface to be smoothed.

Optionally, the temperature of the smoothing surface of the smoothing body and / or the temperature of the smoothed broad surface of the wood-based panel are measured and compared with a predefinable desired temperature value in order to control the smoothing process. For example, if the temperature is too low on the smoothing element or on the smoothing roller, the relative speed between the wood-based panel and the smoothing surface of the smoothing body (preferably smoothing roller) and / or the contact force of the smoothing member are increased to the surface to be smoothed. The measurement of the temperature of the smoothing surface of the smoothing body or the smoothed broad surface of the wood-based panel is preferably carried out by means of non-contact temperature sensors.

Following the chipless smoothing, the smoothed broad surface of the wood-based panel is coated with a high-gloss laminate coating. The so coated wood-based panel is finally treated further without forced cooling, for example, divided into smaller plate formats and stored in a warehouse (see. Fig. 2 ).

The embodiment of the invention is not limited to the embodiment shown in the drawing. Rather, numerous variants are possible, which make use even in deviating embodiment of the reproduced in the appended claims inventive concept.

Claims (19)

1. Method for producing a wood-based material board comprising a high-gloss laminate coating, in which, as a wood-based material board, a chipboard comprising at least one planar wide surface is sanded at this wide surface, characterised by the following operational steps:

   chip-free smoothing of the sanded, planar wide surface by compacting said wide surface by means of a cylindrical or board-shaped smoothing member, the smoothing face of which is tempered to at least 100 °C or has a temperature of at least 100 °C, and coating the smoothed wide surface by pressing on a high-gloss laminate coating in the form of a direct coating, a chipboard being used as a wood-based material board, which chipboard comprises layers of varying chip thickness distribution, having a middle layer in which the maximum of the chip thickness distribution is in the range of from 1.0 mm to 4.0 mm and top layers in which the maximum of the chip thickness distribution is of a chip thickness in the range of from 0.1 mm to 0.8 mm, the proportion of chips in the chip material of the top layers having a thickness of less than 0.6 mm being at least 75 wt.%, in particular at least 80 wt.% and preferably at least 90 wt.%.
2. Method according to claim 1, characterised in that the high-gloss laminate coating pressed onto the chipboard is not subjected to forced cooling.
3. Method according to either claim 1 or claim 2, characterised in that a chipboard is used which comprises layers of varying chip length distribution, having a middle layer in which the maximum of the chip length distribution is between 8 mm and 15 mm and top layers in which the maximum of the chip length distribution is of a chip length of between 3 mm and 8 mm, the proportion of chips in the chip material of the top layers having a length of less than 6 mm being at least 75 wt.%, in particular at least 80 wt.% and preferably at least 90 wt.%.
4. Method according to any of claims 1 to 3, characterised in that the binding agent content in the top layers of the chipboard with respect to the absolute dried mass of the top layer chips is at least 10 wt.%, in particular at least 12 wt.% and preferably in the range of from 15 to 25 wt.%.
5. Method according to any of claims 1 to 4, characterised in that a chipboard is used which has a chip material in which the proportion of chips having a thickness of less than 0.6 mm is at least 50 wt.%, in particular at least 65 wt.% and preferably at least 80 wt.%.
6. Method according to any of claims 1 to 5, characterised in that a chipboard is used which has a chip material in which the proportion of chips having a length of less than 8 mm is at least 50 wt.%, in particular at least 65 wt.% and preferably at least 85 wt.%.
7. Method according to any of claims 1 to 6, characterised in that, as a smoothing member, a roller is pressed onto the wide surface to be smoothed using a force in the range of from 200 to 1000 N/cm of board width, preferably in the range of from 450 to 750 N/cm of board width.
8. Method according to any of claims 1 to 7, characterised in that the wide surface to be smoothed of the wood-based material board is sanded in several stages prior to the chip-free smoothing, the last sanding pass being performed using a grain size of at most 180, preferably of at most 120.
9. Method according to any of claims 1 to 8, characterised in that the chipboard is moved along a sanding tool, the wide surface to be smoothed being additionally sanded, prior to chip-free smoothing, by means of at least one transverse sanding pass with respect to the movement direction of the chipboard along the sanding tool.
10. Method according to any of claims 1 to 9, characterised in that the smoothing face of the smoothing member is tempered to a temperature in the range of from 150 °C to 240 °C, preferably in the range of from 180 °C to 230 °C.
11. Method according to any of claims 1 to 10, characterised in that the chip-free smoothing of the sanded, planar wide surface is performed by compacting said wide surface by means of rollers tempered to at least 150 °C, preferably to at least 180 °C, the rollers being pressed against the chipboard from above and below.
12. Method according to any of claims 1 to 11, characterised in that the smoothing face of the smoothing member has a temperature of at least 100 °C, preferably at least 150 °C, due to friction between the smoothing member and the wide surface to be smoothed.
13. Method according to any of claims 1 to 12, characterised in that the temperature of the smoothing face of the smoothing member or the temperature of the smoothed wide surface of the chipboard is measured, in that the measured temperature is compared with a predefinable target temperature, and in that the relative speed between the wide surface to be smoothed and the smoothing face of the smoothing member and/or the force with which the smoothing member is pressed against the surface to be smoothed is/are controlled according to the measured temperature.
14. Method according to any of claims 1 to 13, characterised in that the wide surface to be smoothed of the chipboard and/or the smoothing face of the smoothing member is wetted with water, a solution and/or an emulsion prior to smoothing.
15. Wood-based material board, formed from a chipboard, which is provided with a glossy laminate coating (4, 5), characterised in that the chipboard comprises layers of varying chip thickness distribution, having a middle layer (1) in which the maximum of the chip thickness distribution is in the range of from 1.0 mm to 4.0 mm, and top layers (2, 3) in which the maximum of the chip thickness distribution is of a chip thickness in the range of from 0.1 mm to 0.8 mm, the proportion of chips in the chip material of the top layers (2, 3) having a thickness of less than 0.6 mm being at least 75 wt.%, in particular at least 80 wt.% and preferably at least 90 wt.%, and in that the laminate coating (4, 5) is applied as a direct coating onto a wide surface, smoothed in a chip-free manner, of the chipboard, the laminate coating (4, 5) having a gloss level of at least 105, in particular of at least 110 and preferably of at least 115 gloss units, as measured according to ISO 2813 with a measuring geometry of 60°.
16. Wood-based material board according to claim 15, characterised in that the layers of the chipboard have a varying chip length distribution, the maximum of the chip length distribution in the middle layer (1) being between 8 mm and 15 mm and the maximum of the chip length distribution in the top layers (2, 3) having a chip length of between 3 mm and 8 mm, and the proportion of chips in the chip material of the top layers (2, 3) having a length of less than 6 mm being at least 75 wt.%, in particular at least 80 wt.% and preferably at least 90 wt.%.
17. Wood-based material board according to either claim 15 or claim 16, characterised in that the binding agent content in the top layers (2, 3) of the wood-based material board with respect to the absolute dried mass of the top layer chips is at least 10 wt.%, in particular at least 12 wt.% and preferably in the range of from 15 to 25 wt.%.
18. Wood-based material board according to any of claims 15 to 17, characterised in that the proportion of chips in the chip material of the chipboard having a thickness of less than 0.6 mm is at least 50 wt.%, in particular at least 65 wt.% and preferably at least 80 wt.%.
19. Wood-based material board according to any of claims 15 to 18, characterised in that the proportion of chips in the chipboard having a length of less than 8 mm is at least 50 wt.%, in particular at least 65 wt.% and preferably at least 85 wt.%.

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