EP4094848B1 - Process for manufacturing an abrasion-resistant laminate - Google Patents

Description

The present invention relates to a method of making an abrasion resistant laminate.

A large number of products or product surfaces that are subject to wear due to mechanical stress must be protected from premature damage or destruction by wear by applying wear-inhibiting layers. These products can be z. B. to furniture, countertops, counters, floors, etc. act. Depending on the frequency and intensity of the stress, different protective measures must be applied so that the user can be guaranteed the longest possible service life.

A large number of the products mentioned above have decorative surfaces that quickly become unsightly and/or can no longer be cleaned when they wear out due to intensive use. These decorative surfaces very often consist of paper impregnated with duroplastic resins, which are pressed onto the wood-based material used in so-called short-cycle presses. Melamine-formaldehyde resin is very often used as a duroplastic resin.

So-called overlay papers, which are thin, α-cellulose-containing papers, have long been used to protect the decorative surfaces. After impregnation with melamine-formaldehyde resins and co-compression on the decorative paper, these have a high degree of transparency, so that the brilliance of the decor is not or only slightly impaired. However, overlays with a high proportion of corundum can lead to transparency problems in high service classes in combination with dark decors.

In the production of laminate floors, the so-called liquid technology is often used today, among other things for reasons of transparency. In contrast to the older manufacturing processes, it does not use impregnated paper, but applies all the layers of a laminate floor to wooden materials in a direct application process using rollers. In detail, these are: primer, color primer, print, wear layer. The respective layer can be applied with a single roller or with a plurality of rollers. Multiple jobs are usually used for color priming (for reasons of opacity) and printing (one color) per roller chosen. Of course, the print can also be applied without contact using a digital printer.

The wear layer, which is intended to minimize the effects of mechanical stress when walking on, essentially consists of melamine resin and corundum particles. A mixture of resin, corundum and auxiliaries (slurry) is either applied to the already printed board with rollers, such as .B. in the EP 1 339 545 B1 described, or the corundum sprinkled into a layer of resin and then covered after intermediate drying of several layers of melamine resin, such as, for example, in the WO2017/198474 A1 described. The structure, which also includes a resin backing, is pressed onto the wood-based panel in a short-cycle press at high pressure and high temperature.

A chrome-plated, structured steel sheet is used for structuring on the upper side of the press. Since the chrome layer is worn away by contact with the corundum particles, glass beads are added to one or more melamine resin layers after the corundum has been applied. The glass spheres, which have a diameter approx. 20 to 30 µm larger and are less hard than the corundum particles, are intended to act as spacers for the corundum from the metal sheet.

The application, which is in the order of magnitude of 10 to 15 g/m ² , is again preferably carried out using a roller system. The order can be made once or several times. This only depends on the number of roller applicators that are behind the corundum application.

As has been shown, however, this technology only provides limited positive results with regard to sheet metal wear. While a metal sheet that is used in the processing of an impregnate structure (with an overlay loaded with corundum) can usually go through more than 50,000 pressings before reworking, this is often less than 10,000 pressings with a liquid structure. This not only leads to higher sheet metal costs per square meter of laminate flooring, but also to a higher stock of pressed sheets in the various structures, since the processing of the pressed sheets is not carried out in the factory but by external companies. This revision, including transport, takes about four weeks. The approx. 10,000 pressings are carried out within approx. three days with a short-cycle press of newer design, so that a new pressing plate then has to be installed.

Attempts to increase sheet life by increasing the amount of glass beads in the roll application have not shown any positive effect on sheet life. In addition, when the glass spheres were increased to more than 20 g/m ² , the transparency was found to deteriorate due to inhomogeneous distribution of the glass spheres. However, this inhomogeneity in the distribution tended to be observed even when the glass beads were applied in quantities of less than 20 g/m ² . It was irrelevant whether the glass spheres were applied directly after the corundum application or whether the glass spheres were only applied after one or more layers of resin without glass spheres. Varying the size of the glass beads did not increase the sheet life either. In addition, as the diameter of the glass spheres increased, a worsening of the distribution was observed. This resulted from the increased tendency of the glass beads in the slurry to sediment, which was also observed with the glass beads with "normal" diameter. This led to increased cleaning effort in lines, storage and preparation tanks.

This results in various disadvantages: uneven application, increased sheet metal wear, transparency problems, increased cleaning effort and sedimentation.

The invention is therefore based on the technical task of increasing sheet metal service life. This should be done without an increase in costs and also without a general change in production technology.

The object is achieved according to the invention by a method having the features of claim 1.

• Bereitstellen einer Holzwerkstoffplatte, die auf der Oberseite mindestens eine Dekorschicht, insbesondere als Druckdekor, aufweist,
• Auftragen von mindestens einer ersten Harzschicht auf die mindestens eine Dekorschicht auf der Oberseite der Holzwerkstoffplatte,
• Aufstreuen, insbesondere gleichmäßiges Aufstreuen eines Gemisches aus abriebfesten Partikeln umfassend Korundpartikel und Glaskugeln , insbesondere eines Gemisches aus Korundpartikeln und Glaskugeln, auf die erste Harzschicht auf der Oberseite der Holzwerkstoffplatte, wobei der Anteil der Menge an aufgestreuten Glaskugeln in dem Gemisch aus abriebfesten Partikeln 5 bis 35 g/m² beträgt,
• Ablüften der mit dem Gemisch aus abriebfesten Partikeln versehenen ersten Harzschicht auf der Oberseite der Holzwerkstoffplatte;
• Auftragen von mindestens einer weiteren, insbesondere zweiten Harzschicht auf die mit dem Gemisch aus abriebfesten Partikeln versehene erste Harzschicht auf der abgelüfteten Oberseite der Holzwerkstoffplatte; und
• Verpressen des Schichtaufbaus unter Ausbildung eines Laminats.

Accordingly, a method of making an abrasion resistant laminate is provided. The present procedure comprises the following steps:

• Providing a wood-based panel that has at least one decorative layer on the upper side, in particular as a printed decoration,
• Applying at least one first resin layer to the at least one decorative layer on the upper side of the wood-based panel,
• Scattering, in particular uniform scattering, of a mixture of abrasion-resistant particles comprising corundum particles and glass beads, in particular a mixture of corundum particles and glass beads, onto the first resin layer on the upper side of the wood-based panel, the proportion of the amount of glass beads sprinkled on in the mixture of abrasion-resistant particles being 5 to 35 g/m ² is
• flashing off the first resin layer provided with the mixture of abrasion-resistant particles on the upper side of the wood-based panel;
• Application of at least one further, in particular second, resin layer to the first resin layer, provided with the mixture of abrasion-resistant particles, on the aired-off upper side of the wood-based material panel; and
• Pressing the layered structure to form a laminate.

The present process thus enables the provision of a laminate in various formats (i.e. piece goods and not in the form of a continuous web) with high wear resistance in a batch process in a cost-effective manner.

According to the present method, a first resin layer, in particular in the form of a first duroplastic resin layer, such as a melamine-formaldehyde resin layer, is applied to the decorative layer (pretreated or not pretreated) of the wood-based panel. Initially, the first resin layer does not dry or begin to dry, but instead the mixture of abrasion-resistant particles (such as corundum particles and glass beads) is evenly scattered onto the wet or still liquid first resin layer on the upper side of the wood-based panel using a suitable scattering device. Since the first resin layer is still liquid when it is sprinkled on, the abrasion-resistant particles can sink into the resin layer. Due to the high solids content of the resin and the resulting increased viscosity, the abrasion-resistant particles are also well embedded in the resin layer. The procedure described allows scattering of corundum and glass without having to use a second scattering device. Surprisingly, this was possible despite the different size and geometry of the particles. For this purpose, the particles only had to be mixed in a simple mixing device. There was no demixing during further processing (spreading).

After the mixture of abrasion-resistant particles has been sprinkled onto the first layer of resin, there is no drying, but flashing off. Flash-off means that a solvent (such as water) in a liquid surface coating slowly evaporates from the surface due to the vapor pressure that the solvent possesses at a certain temperature. Flashing off can be accelerated by a stream of air passed over the surface. This can be done either by the movement of the element on which the surface coating is placed or by an air flow that is passed over the surface coating. The resin layer with the sprinkled mixture of abrasion-resistant particles is not actually dried. It has lost some solvent but still has a high level of stickiness.

The abrasion-resistant particles of the mixture are thus fixed in the at least one first resin layer. The abrasion-resistant particles are thus located in a first resin layer which is provided on the decorative layer and which is covered by at least one further, preferably several further resin layers. The mixture of abrasion resistant particles is thus not provided in the outer covering layers (and thus does not protrude from the resin structure), but rather is provided in a lower resin layer. The wear of the press plates can be reduced by covering the abrasion-resistant particles with additional layers of resin. These are results contrary to those obtained using a glass bead slurry. There it was shown that the wear of the press plate was reduced if the glass beads were applied as far as possible behind the corundum application.

By sprinkling on a mixture of corundum particles and glass beads, it is also possible to increase the amount of glass beads applied (e.g. compared to applying the glass beads in a slurry) without the otherwise observed transparency problems occurring.

In addition, it was surprisingly observed that the wear resistance (Taber test) increased when the quantity of glass beads applied was increased while the quantity of corundum applied was reduced at the same time (eg up to 30%). This, too, was not observed when glass beads were applied by rollers. This is of particular interest with regard to costs, because it means that more expensive corundum can be replaced with cheaper glass beads. As has been shown, when the identical quantity of glass beads is applied using a spreader, the sheet metal service life can be increased by an average of approx. 10% compared to application with a roller.

This effect was also evident when using an overlay in which the amount of corundum spread, for example 18 g/m ² , was replaced by a mixture of 12 g corundum/m ² and 6 g glass beads/m ² . Here, too, it was shown that when testing the behavior against abrasion stress on a laminate floor sample for which the overlay was used for its production, similar results were achieved as with the zero sample. It was also found that there was no difference between silanized and non-silanized glass beads.

In addition, when the large formats were divided into individual elements, there was a reduction in tool costs.

With the present method, an increase in the service life of the sheet metal, a reduction in the cost of auxiliary materials and an improvement in transparency are achieved.

In a preferred embodiment of the present method, the wood-based panel provided with the decorative layer is not heated in a dryer, such as an IR dryer, before the application of the first resin layer. This can be done by turning off an IR dryer on the production line, or by not having an IR dryer on the production line. By avoiding the heating of the wood-based panel provided with a decorative layer, there is no electrostatic charging of the panel surface and the spreading curtain when the corundum is spread becomes homogeneous. Also, the thermal lift resulting from the dissipated heat of the disk surface of the disk is reduced.

For a person skilled in the art, dispensing with heating the printed wood-based material board in an IR dryer is not obvious, since a protective layer made of a resin that has not yet fully hardened is typically arranged on the decorative layers applied by means of direct printing.

In one embodiment of the present method it is therefore provided that the first resin layer is applied to a decorative layer provided with a protective layer. This protective layer can be a layer of paper impregnated with a thermosetting resin or a layer of a thermosetting resin, in particular a melamine-formaldehyde resin, urea-formaldehyde resin or melamine-urea-formaldehyde resin and can be glass beads (size 50-150 µm) included as spacers for intermediate storage of the panels. This protective layer serves as a temporary protection for the decorative layer for storage prior to further processing. The protective layer on the decorative layer is not yet complete cured, but with a certain residual moisture content of about 10%, preferably about 6%, provided and further crosslinkable. Such protective layers are, for example, in the WO 2010/112125 A1 or EP 2 774 770 B1 described.

The typically used step of heating decorative layers provided with such a (thermosetting) protective layer serves to heat the protective layer and adjust the degree of residual moisture and the adhesion of subsequent resin layers.

However, it has been shown that the step of heating the protective layer has a negative effect on the scattering pattern of the abrasion-resistant particles. Omitting the heating of the printed wood-based panel provided with a protective layer results in a homogenization of the scatter pattern and thus an even distribution of the abrasion-resistant particles and glass beads on the panel surface.

In one embodiment of the present method, the resin layers to be applied can be in liquid and/or powder form. It is particularly preferred if the first resin layer is applied in liquid form. The further resin layers, which are applied after the mixture of abrasion-resistant particles, can be liquid, powdery or a combination of alternating liquid and powdery resin layers.

The resin layers used in the present method are preferably based on thermosetting resins, in particular melamine-formaldehyde resin, urea-formaldehyde resin or melamine-urea-formaldehyde resin.

The resins used preferably each contain additives such as hardeners, wetting agents (surfactants or mixtures thereof), defoamers, release agents and/or other components. The wetting agent is used in each of the resin layers in an amount of 0.1-1% by weight.

A latent hardener is preferably used as the hardener, such as alkanolamine salts of acids, for example an alkanolamine salt of a sulfonic acid (see DeuroCure from the manufacturer Deurowood). There is a mixing station for each application unit, in which the components are pre-mixed. These pre-mixes are pumped into a storage container from which they are dosed into the application units.

The proportion of hardener in the individual resin layers varies and can be between 0.5 to 1.5% by weight, preferably 0.7 to 1.3% by weight. It is particularly preferred that the proportion of hardener per application of resin decreases in the production direction; i.e. the proportion of hardener in the lower resin layers is greater than in the upper resin layers. By reducing the amount of hardener from the lower to the upper resin layers, the individual resin layers can be hardened evenly in the KT press.

The amount of the first resin layer applied to the upper side of the wood-based panel can be between 50-100 g/m ² , preferably 60-80 g/m ² , particularly preferably between 65 and 75 g liquid/m ² , such as 70 g liquid/m 2 amount to ² .

In one embodiment of the present method it can also be provided that at least one first resin layer is applied parallel to the upper side and also to the underside of the wood-based panel as a counteract. The amount of the first resin layer applied to the underside of the wood-based panel can be between 50-100 g/m ² , preferably 60-80 g/m ² , particularly preferably 70 g/m ² . The first lower resin layer is preferably colored (eg brownish) in order to simulate a balancing act.

The solids content of the resin used for the first resin layer is 60-80% by weight, preferably 65-70% by weight, particularly preferably between 65 and 67% by weight, for both the upper side and the lower side.

The first resin layer is preferably applied in parallel or simultaneously to the top and bottom of the wood-based panel in at least one dual application device (roller application unit).

In one embodiment of the present method, the mixture of corundum particles and glass beads is scattered on in a total amount of between 20 and 40 g/m ² , preferably between 25 and 35 g/m ² , particularly preferably 30 g/m ² .

The corundum particles used are preferably fine corundum (white) with a high level of transparency, so that the optical effect of the underlying decoration is adversely affected as little as possible. Corundum has an uneven three-dimensional shape.

In one embodiment, the amount of corundum particles in the mixture of abrasion-resistant particles is 5 to 35 g/m ² , preferably 8 to 30 g/m ² , particularly preferably 8 to 15 g/m ² , for example 12 or 18 g/m 2 ² with a mixture quantity of 30 g/m ² .

Corundum particles with a Mohs hardness of at least 9, preferably with cutting edges, and a grain size between 50 and 90 μm are preferably used. Corundum particles with grain sizes in the classes F180 to F240, preferably F200, can be used. The grain size of class F180 covers a range from 53 - 90 µm, F220 from 45-75 µm, F230 34-82 µm, F240 28-70 µm (FEPA standard). In one variant, white aluminum oxide F180 to F240, preferably in a main particle size range of 53-90 μm, is used as the abrasion-resistant particles. In a particularly preferred embodiment, corundum particles of class F200 are used, with F200 being a mixture between F180 and F220 and having a diameter between 53 and 75 μm. The corundum particles must not be too fine-grained (danger of dust formation, insufficient abrasion resistance), but also not too coarse-grained (protruding from the resin layer). The size of the corundum particles therefore represents a compromise.

In a further embodiment, silanized corundum particles can be used. Typical silanizing agents are aminosilanes.

It is preferred if the glass beads used have a Mohs hardness of at least 7 and a diameter of 50 to 150 μm, preferably 80 to 120 μm, particularly preferably 90 to 110 μm. The glass spheres are preferably free of cutting edges and spherical.

The amount of scattered glass beads in the mixture of abrasion-resistant particles is between 5 to 35 g/m ² , preferably 10 to 30 g/m ² , particularly preferably 15 to 25 g/m ² , for example 12 or 18 g/m ² with a mixture quantity of 30 g/m ² .

The glass spheres can (but do not have to) be in silanized form. The embedding of the glass beads in the resin matrix is improved by the silanization of the glass beads.

The amount of the additional, second resin layer applied to the upper side and optionally to the underside as a counteract of the wood-based panel can be between 10 and 50 g liquid/m ² , preferably between 15 and 40 g liquid/m ² , particularly preferably between 20 and 30 g liquid / m ² , such as 20 g liquid / m ² amount.

The solids content of the resin used for the second resin layer is 60 and 80% by weight, preferably 65 and 70% by weight, particularly preferably between 65 and 67% by weight for both the upper side and the lower side.

In a further embodiment of the present method, following the second resin layer, further resin layers are applied one after the other to the top and bottom of the wood-based material board in a double application device and dried after each application (e.g. by means of hot air drying).

As already indicated, the preferably liquid resin layers applied to the underside of the wood-based material board act as a counteract. Applying the layers of resin to the top and bottom of the wood-based panel in approximately the same amounts ensures that the tensile forces on the wood-based panel caused by the applied layers during pressing cancel each other out. The balancing layer applied to the underside roughly corresponds in terms of layer structure and the respective layer thickness to the layer sequence applied to the top side, but without the addition of abrasion-resistant particles.

However, it is also possible for at least one resin-impregnated paper layer to be applied to the underside of the wood-based panel as a balancing act.

The (liquid) resin layers are dried at dryer temperatures of between 150 and 220° C., preferably between 180 and 210° C., in particular in a convection dryer. The temperature is adjusted to the respective resin layers and can vary in the individual convection dryers; for example, the temperature in the second, third and fourth convection dryers may be 205°C and in the fifth and sixth convection dryers 198°C, respectively. Instead of convection dryers, however, other dryers can also be used.

As already indicated above, it is also possible to apply at least one powdered resin layer to the mixture of abrasion-resistant particles instead of liquid resin layers. This powdered resin layer is preferably melted after application, so that a continuous resin layer is formed.

Replacing resin powder with liquid resin eliminates the time-consuming drying process required for liquid overlays, which reduces system costs, exhaust air problems and space requirements. Overall, the present method enables a more flexible technology.

In one embodiment of the present method, the pulverulent resin is applied in an amount of 10 to 50 g/m ² , preferably 15 to 40 g/m ² , particularly preferably 20 to 30 g/m ² . This application quantity of resin powder essentially applies to all resin powder layers to be applied, although these can be adjusted in each case. The scattering density is selected in such a way that covering layers are generated in any case. The particle size of the powdery resin is between 20 and 100 μm, preferably between 40 and 89 μm.

In a further embodiment of the present method, the powdered resin to be applied (as in the case of the liquid resin) is a duroplastic resin, preferably a urea resin, a melamine resin or a phenolic resin, particularly preferably a melamine-formaldehyde resin. It is preferable if a melamine resin or a urea resin is used for the first resin layer. Only melamine resin is preferably used in the upper layers.

In the context of the present application, "melting" or "gelling" means that the resin layer is not yet fully polymerized, but rather the polymerization is stopped at an intermediate stage in which further crosslinking or polymerization is still possible at a later processing time. The meaning of "gelling" is therefore usually based on the fact that further functional layers are to be applied to the protective layer that has already been applied at a later point in time, or that the product is only to be finished in further processing steps.

Other substances can also be added to the melamine resin powder. It is particularly advantageous that because z. B. salting, thickening, settling, hardening influencing effects, etc. poorly compatible with liquid melamine resin substances can be used. These can be salts to increase conductivity, organic or inorganic flame retardants, cellulose derivatives, radical scavengers, pigments, UV absorbers, etc. Accordingly, the powdered resin used can contain additives such as pigments, conductive substances and cellulose.

The overall layer thickness of the resin layers applied to the wood-based material board can be between 60 and 200 μm, preferably between 90 and 150 μm, particularly preferably between 100 and 120 μm.

In the pressing step that follows the last drying step, the layer structure is pressed under the influence of pressure and temperature in a short-cycle press at temperatures between 150 and 250° C., preferably between 180 and 230° C., particularly preferably at 200° C. and a pressure between 30 and 60 kg/cm ² , more preferably between 40 and 50 kg/cm ² . The pressing time is between 5 and 15 seconds, preferably between 7 and 10 seconds.

The coated wood-based panel is preferably aligned in the short-cycle press to a structured press plate located in the short-cycle press using markings on the wood-based panel, so that congruence between the decor on the wood-based panel and the structure to be embossed on the press plate is produced. This enables the production of a decor-synchronous structure. During pressing, the melamine resin layers melt and a laminate is formed by a condensation reaction including the corundum/glass components.

In a further embodiment, the at least one wood-based material panel is a medium-density fiber (MDF), high-density fiber (HDF) or chipboard or coarse particle board (OSB) or plywood panel and/or a wood-plastic panel.

In one embodiment, an unpolished wood fiber board, in particular MDF or HDF, is used, which is also provided with a pressed skin (rotting layer) on the upper side. Aqueous melamine resin is applied on top to fill the press skin. The melamine resin is later melted in the short-cycle press and thus has a tempering effect in the area of this layer; i.e. it counteracts delamination.

The decorative layer already mentioned above can be applied by means of direct printing. In the case of direct printing, a water-based, pigmented printing ink is applied in gravure or digital printing processes, with the water-based pigmented printing ink being able to be applied in more than one layer, for example in the form of two to ten layers, preferably three to eight layers.

In the case of direct printing, the at least one decorative layer is applied, as mentioned, by means of an analog gravure printing and/or a digital printing process. Intaglio printing is a printing technique in which the elements to be imaged are indented in a printing form that is inked before printing. The printing ink is mainly in the indentations and is transferred to the object to be printed, such as a wood fiber board, due to the contact pressure of the printing form and adhesive forces. With digital printing, on the other hand, the printed image is transferred directly from a computer to a printing machine, such as a laser printer or inkjet printer. This eliminates the use of a static printing form. In both processes, the use of water-based paints and inks or UV-based coloring agents is possible. It is also conceivable to combine the mentioned printing techniques from gravure and digital printing. A suitable combination of printing techniques can be done directly on the carrier plate or the layer to be printed, or before printing by adapting the electronic data records used.

The markings required for alignment in the press are also printed together with the decor.

It is also possible for at least one primer layer to be arranged between the wood material panel or carrier panel and the at least one decorative layer. The primer layer is applied before printing.

The primer layer preferably used here comprises a composition of casein or soybean protein as a binder and inorganic pigments, in particular inorganic color pigments. White pigments such as titanium dioxide can be used as color pigments in the primer layer, or other color pigments such as calcium carbonate, barium sulfate or barium carbonate. In addition to the color pigments and the casein or soy protein, the primer can also contain water as a solvent. It is also preferred if the pigmented base coat applied consists of at least one, preferably at least two, particularly preferably at least four layers or coats applied in succession, it being possible for the amount applied between the layers or coats to be the same or different.

The present method thus makes it possible to produce a laminate from an abrasion-resistant wood material panel provided with a decorative layer and having a resin structure with abrasion-resistant particles, in particular corundum particles and glass beads. The laminate includes at least one wood-based panel, at least one decorative layer on the upper side of the wood-based panel, at least a first resin layer on the upper side and optionally the lower side, at least one layer containing a mixture of abrasion-resistant particles, in particular a mixture of corundum particles and glass beads on and/or in the first resin layer the top of the engineered wood board, and at least a second resin layer on top and optionally on the underside of the engineered wood board.

In a further embodiment, the laminate comprises a wood-based material board provided with a decorative layer with a resin structure consisting of a first resin layer containing abrasion-resistant particles on the upper side, a corresponding resin layer (but without abrasion-resistant particles) on the underside, at least one second resin layer on the upper side and one corresponding resin layer on the underside of the wood-based panel, at least a third resin layer on the upper side and a corresponding resin layer on the underside of the wood-based panel, at least a fourth, fifth and sixth resin layer on the upper side and corresponding resin layers on the underside of the wood-based panel.

In a preferred embodiment, the present method enables the production of an abrasion-resistant wood-based material board with the following layer structure (seen from bottom to top): Balancing layer made of six resin layers - wood-based material board - primer layer - printed decorative layer - protective layer, in particular a protective layer made of a resin that has not yet fully cured - first resin layer - Layer of abrasion-resistant particles, in particular corundum particles and glass beads (which are preferably partially embedded in the first resin layer) - second resin layer - third resin layer fourth resin layer - fifth resin layer - sixth resin layer.

The protective layer serves to cover the decor and to protect the decor during interim storage (stacking, storage, transport). The other layers of resin on the top form an overlay that protects the finished laminate against abrasion and enables structuring that is synchronized with the decor.

• mindestens eine erste Auftragsvorrichtung zum Auftragen einer ersten Harzschicht auf die Oberseite der Holzwerkstoffplatte;
• mindestens eine in Verarbeitungsrichtung hinter der ersten Auftragsvorrichtung angeordnete Vorrichtung zum Aufstreuen einer vorbestimmten Menge eines Gemisches aus abriebfesten Partikeln, insbesondere eines Gemisches aus Korundpartikeln und Glaskugeln;
• mindestens eine in Verarbeitungsrichtung hinter der ersten Auftragsvorrichtung und Streuvorrichtung angeordnete weitere, zweite Auftragsvorrichtung zum Auftragen einer weiteren Harzschicht auf die Oberseite und ggfs. auf die Unterseite der Holzwerkstoffplatte,
• optional mindestens eine in Verarbeitungsrichtung hinter der weiteren, zweiten Auftragsvorrichtung angeordnete Trocknungsvorrichtung zum Trocknen des Schichtaufbaus aus erster und zweiter Harzschicht; und
• mindestens eine in Verarbeitungsrichtung hinter der letzten Trocknungsvorrichtung angeordnete Kurztaktpresse.

The production line for carrying out the present method can include the following elements:

• at least one first application device for applying a first resin layer on top of the wood-based panel;
• at least one device, arranged downstream of the first application device in the processing direction, for sprinkling on a predetermined amount of a mixture of abrasion-resistant particles, in particular a mixture of corundum particles and glass beads;
• at least one further, second application device arranged in the processing direction behind the first application device and spreading device for applying a further layer of resin to the upper side and, if necessary, to the underside of the wood-based panel,
• optionally at least one drying device arranged downstream of the further, second application device in the processing direction for drying the layered structure made up of the first and second resin layers; and
• at least one short-cycle press arranged downstream of the last drying device in the processing direction.

• mindestens eine erste Auftragsvorrichtung zum Auftragen einer ersten Harzschicht auf die Oberseite der Holzwerkstoffplatte;
• mindestens eine in Verarbeitungsrichtung hinter der ersten Auftragsvorrichtung angeordnete Vorrichtung zum Aufstreuen einer vorbestimmten Menge eines Gemisches an abriebfesten Partikeln, insbesondere eines Gemisches aus Korundpartikeln und Glaskugeln;
• mindestens eine in Verarbeitungsrichtung hinter der ersten Auftragsvorrichtung und Streuvorrichtung angeordnete zweite Auftragsvorrichtung zum Auftragen einer zweiten Harzschicht auf die Oberseite der Holzwerkstoffplatte,
• mindestens eine in Verarbeitungsrichtung hinter der zweiten Auftragsvorrichtung angeordnete Trocknungsvorrichtung zum Trocknen des Schichtaufbaus aus erster und zweiter Harzschicht;
• mindestens eine in Verarbeitungsrichtung hinter der Trocknungsvorrichtung angeordnete dritte Auftragsvorrichtung zum Auftragen einer dritten Harzschicht auf die Oberseite und/oder einer Harzschicht parallel auf die Unterseite der Trägerplatte,
• mindestens eine in Verarbeitungsrichtung hinter der dritten Auftragsvorrichtung angeordnete weitere Trocknungsvorrichtung zum Trocknen der dritten oberen und/oder korrespondierenden unteren Harzschicht;
• mindestens eine in Verarbeitungsrichtung hinter der weiteren Trocknungsvorrichtung angeordnete vierte Auftragsvorrichtung zum Auftragen einer vierten Harzschicht auf die Oberseite, und/oder einer Harzschicht parallel auf die Unterseite der Trägerplatte,
• mindestens eine in Verarbeitungsrichtung hinter der vierten Auftragsvorrichtung angeordnete Trocknungsvorrichtung zum Trocknen der vierten oberen und/oder korrespondierenden unteren Harzschicht;
  • mindestens eine in Verarbeitungsrichtung hinter der Trocknungsvorrichtung angeordnete fünfte Auftragsvorrichtung zum Auftragen einer fünften Harzschicht auf die Oberseite und/oder einer Harzschicht parallel auf die Unterseite der Trägerplatte;
• mindestens eine in Verarbeitungsrichtung hinter der fünften Auftragsvorrichtung angeordnete Trocknungsvorrichtung zum Trocknen der fünften oberen und/ oder korrespondierenden unteren Harzschicht;
• mindestens eine in Verarbeitungsrichtung hinter der Trocknungsvorrichtung angeordnete sechste Auftragsvorrichtung zum Auftragen einer sechsten Harzschicht auf die Oberseite und/oder einer Harzschicht parallel auf die Unterseite der Trägerplatte;
• mindestens eine in Verarbeitungsrichtung hinter der sechsten Auftragsvorrichtung angeordnete Trocknungsvorrichtung zum Trocknen der sechsten oberen und/ oder korrespondierenden unteren Harzschicht; und
• mindestens eine in Verarbeitungsrichtung hinter der letzten Trocknungsvorrichtung angeordnete Kurztaktpresse.

In a further embodiment, the present production line includes the following elements:

• at least one first application device for applying a first resin layer on top of the wood-based panel;
• at least one device, arranged downstream of the first application device in the processing direction, for sprinkling on a predetermined quantity of a mixture of abrasion-resistant particles, in particular a mixture of corundum particles and glass beads;
• at least one second application device arranged downstream of the first application device and spreading device in the processing direction for applying a second resin layer to the upper side of the wood-based panel,
• at least one drying device arranged downstream of the second application device in the processing direction for drying the layer structure made up of the first and second resin layers;
• at least one third application device arranged downstream of the drying device in the processing direction for applying a third resin layer to the upper side and/or a resin layer in parallel to the underside of the carrier plate,
• at least one further drying device arranged downstream of the third application device in the processing direction for drying the third upper and/or corresponding lower resin layer;
• at least one fourth application device arranged downstream of the further drying device in the processing direction for applying a fourth resin layer to the upper side and/or a resin layer parallel to the underside of the carrier plate,
• at least one drying device arranged downstream of the fourth application device for drying the fourth upper and/or corresponding lower resin layer;
  • at least one fifth application device arranged downstream of the drying device for applying a fifth resin layer on the upper side and/or a resin layer in parallel on the lower side of the carrier plate;
• at least one drying device arranged downstream of the fifth application device for drying the fifth upper and/or corresponding lower resin layer;
• at least one sixth application device arranged downstream of the drying device for applying a sixth resin layer to the upper side and/or a resin layer in parallel to the lower side of the carrier plate;
• at least one drying device arranged downstream of the sixth application device for drying the sixth upper and/or corresponding lower resin layer; and
• at least one short-cycle press arranged downstream of the last drying device in the processing direction.

In a preferred variant of the present production line, no drying device is provided before the first application device, or in the event that a drying device is installed as part of the production line, this drying device is not in operation, i.e. not active.

Also, no drying device is provided between the spreading device and the second application device. Rather, after leaving the scattering device, the still moist plate is introduced directly into the second application device.

In one embodiment, the present production line comprises a total of a simple, one-sided application unit for applying the first resin layer to the top of the printed wood-based panel and five double application units for applying five further resin layers to the top and bottom of the wood-based panel, with at least one drying device for drying behind each double application unit the upper and/or lower resin layer is provided.

The scattering device provided in the present production line for the mixture of abrasion-resistant particles, in particular the mixture of corundum particles and glass beads is suitable for spreading powder, granules and includes an oscillating brush system. The spreading device essentially consists of a storage hopper, a rotating, structured roller and a scraper. The amount of abrasion-resistant material applied is determined by the rotational speed of the roller. The spreading device preferably comprises a spiked roller.

In one embodiment of the present production line, it is also provided that the at least one scattering device is surrounded or arranged in at least one cabin, which is provided with at least one means for removing dust occurring in the cabin. The means for removing the dust can be designed in the form of a suction device or as a device for blowing in air. Air injection can be achieved via nozzles installed at the plate inlet and outlet, blowing air into the booth. In addition, they can prevent an inhomogeneous scatter curtain of abrasion-resistant material from being created by air movements.

The removal of the dust from abrasion-resistant material from the vicinity of the scattering device is advantageous because, in addition to the obvious health hazards for the workers working on the production line, the fine dust from abrasion-resistant particles is also deposited on other parts of the production line and leads to increased wear of the same. The arrangement of the spreading device in a cabin therefore not only serves to reduce the health pollution of dust in the vicinity of the production line, but also prevents premature wear.

The scattering device is preferably controlled by a light barrier, the light barrier being arranged in the processing direction in front of the roller (scattering roller) provided below the scattering device. Controlling the scattering device using a light barrier makes sense, since there are more or less large gaps between the individual wood-based panels. This starts the spreading process as soon as a plate is in front of the spreading roller.

In one embodiment of the present scattering device, at least one funnel is provided in front of the scattering roller to collect excess abrasion-resistant particles (i.e. abrasion-resistant particles that are not scattered on the at least one wood-based material board, but rather before the wood-based board is driven in with the help of the transport device under the scattering roller in front of the latter falling down). .

In a further variant, the hopper is coupled to at least one conveyor device and a screening device, with the excess material mixture collected in the hopper being transported to the screening device via the conveyor device. The screen mesh of the screening device corresponds to the largest grain of the abrasion-resistant particulate material used (i.e. approx. 80-120 µm). In the screen, debris and clumped material (such as clumped resin or clumped abrasion resistant material) are separated from the collected abrasion resistant material and the screened abrasion resistant material can be returned (recycled) to the spreader.

As already explained above, provision is also made for mixing the hardener in a targeted manner with the liquid resin at the corresponding application units or application devices for the various resin layers.

Figur 1

eine schematische Darstellung einer ersten Ausführungsform einer Produktionslinie zur Herstellung eines Laminats unter Verwendung des erfindungsgemäßen Verfahrens, und

Figur 2

eine schematische Darstellung einer zweiten Ausführungsform einer Produktionslinie zur Herstellung eines Laminats unter Verwendung des erfindungsgemäßen Verfahrens

The invention is explained in more detail below with reference to the figures of the drawings using an exemplary embodiment. Show it:

figure 1

a schematic representation of a first embodiment of a production line for producing a laminate using the method according to the invention, and

figure 2

a schematic representation of a second embodiment of a production line for the production of a laminate using the method according to the invention

The one in the figure 1 The production line shown schematically includes a one-sided application unit 1 (grooved roller) for applying the first layer of resin.

After the first applicator roller 1, a scattering device 20 is provided for evenly scattering the mixture of abrasion-resistant material such as corundum and glass beads onto the first resin layer on the upper side of the HDF panel. Corundum F200 is used as the abrasion-resistant material, which measures around 50-90 µm in diameter according to the FEPA standard. The glass beads used have a diameter or grain size of 90-110 µm.

The spreading device 20 essentially consists of a storage funnel, a rotating, structured spiked roller and a scraper. The application quantity of the material is determined by the rotational speed of the spreader roller. On the Depending on the required abrasion class of the product, between eg 30 g/m ² of the mixture of corundum particles (12 - 18 g/m ² ) and glass beads (12-18 g/m ² ) is sprinkled onto the resin-coated board.

The mixture falls from the spiked roller at a distance of 5 cm onto the board treated with melamine resin. Since the first resin layer is still liquid when it is sprinkled on, the corundum particles and glass beads can sink into the resin layer. Under the present scattering device, in front of the scattering roller, there is at least one funnel (not shown) for catching excess corundum particles and glass beads (i.e. not scattered on the at least one wood-based panel, but rather corundum particles falling down before the wood-based panel is moved in with the help of the transport device under the scattering roller in front of the same and glass balls) provided.

In a next step, the first layer of resin sprinkled with the mixture of abrasion-resistant particles is flashed off, with the solvent (e.g. water) from the liquid surface coating slowly evaporating out of the surface due to the vapor pressure. Flashing takes place by means of a stream of air that is passed over the surface.

In the double-sided application unit 2, the board coated with melamine-formaldehyde resin and corundum/glass beads is coated with further melamine-formaldehyde resin (about 20 g/m ² ). With the second application, the corundum grains and glass beads are covered with liquid resin or incorporated into the overlay layer. This prevents the removal of the corundum and the glass balls in the convection dryer due to the high level of air turbulence.

The assembly of the first and second resin layers is dried in the convection dryer 2a. If a powdered resin is applied instead of a liquid resin, the drying step is omitted.

Finally, the layer structure is cured in a short-cycle press 7 at a press temperature of 180-220° C. and a press time of 8 to 10 seconds under a specific pressure of 40 kg/cm ² . The pressed panels are cooled and stored.

The one in the figure 2 The production line shown schematically includes the in figure 1 elements shown. Other elements are also planned.

Thus, the production line includes the figure 2 an IR dryer 1a which is switched off. By switching off the IR dryer 1a from the production line, the electrostatic charging of the panel surface that otherwise takes place in the IR dryer is avoided, which enables the formation of a homogeneous scattering curtain of the corundum.

The production line also includes a one-sided application unit 1 (grooved roller) and five double application units 2, 3, 4, 5, 6 for the simultaneous application of the respective resin layer on the top and bottom of the isolated printed material panels, e.g. of printed HDF panels and respectively four convection dryers 2a, 3a, 4a, 5a, 6a arranged behind the application units in the processing direction.

After the first applicator roller 1, the scattering device 20 is provided for evenly scattering the mixture of abrasion-resistant material such as corundum and glass beads onto the first resin layer on the upper side of the HDF panel.

In the next step, the first layer of resin sprinkled with the mixture of abrasion-resistant particles is flashed off, with the solvent (e.g. water) from the liquid surface coating slowly evaporating from the surface due to the vapor pressure. Flashing takes place by means of a stream of air that is passed over the surface.

The assembly of the first and second resin layers is dried in the convection dryer 2a.

A third convection dryer 3a for drying the third resin layer is arranged downstream of the third double application unit 3 for applying the third resin layer.

After the fourth to sixth resin layers have been applied in a fourth to sixth double application unit 4, 5, 6 and dried in a convection dryer 4a, 5a, 6a, the layer structure is pressed in a short-cycle press 7 at a pressing temperature of 180-220 °C and a pressing time of 8 to 10 seconds under a specific pressure of 40 kg/cm ² . The pressed panels are cooled and stored.

Example 1:

On a production line that was operated at 22 m/min, printed HDF (8 mm) were first coated with a melamine resin by roller application (amount applied approx. 70 g liquid/m ² . The solids content of the melamine resin was approx. 65% by weight and contained the usual auxiliaries such as hardeners, wetting agents, etc. A shaker was used to sprinkle a mixture of 12 g corundum/m ² and 18 g glass beads/m ² (grain size range: 80 - 110 µm) into the melamine resin. The standard was F200 The resin was flashed off over a distance of approximately ten metres.

Thereafter, in each case 20 g of liquid melamine resin/m ² (solids content about 65% by weight) were applied with a further five further roller applicators. A melamine resin in the same amount was also applied to the back. Hot air drying followed each application. The structure was then pressed in a short-cycle press at a pressing temperature of 200° C., a pressing pressure of 40 kg/cm ² and a pressing time of nine seconds.

A sample from this production was tested for its behavior under abrasion stress using a Taber abrader in accordance with DIN EN 13329. For comparison, a sample was tested with which 18 g corundum/m ² had been scattered and 12 g glass beads/m ² had been applied via slurries in application units two to five. A value of 4500 μm resulted for the first sample. For the second sample, a value of 4100 µm.

The first variant showed better transparency compared to the second variant. Both variants were pressed on the production line with a new press plate of identical structure until damage to the press plate was observed. These became apparent in the first variant after 12,200 pressings and in variant 2 after 11,000 pressings.

Example 2:

In an impregnation channel operated at a feed rate of 50 m/min, an overlay (grammage: 25 g/m ² ) was impregnated with a melamine resin (solids content: approx. 65% by weight) in a first step in a trough. The melamine resin contained the usual auxiliaries such as hardeners, wetting agents, etc. After passing through the breathing section and squeezing rollers to adjust the resin application (400% based on the paper weight).

On a production line that was operated at 22 m/min, printed HDF (8 mm) were first coated with a melamine resin by roller application (application quantity approx. 70 g liquid/m ² . The solids content of the melamine resin was approx. 65% by weight and contained the usual auxiliaries such as hardeners, wetting agents, etc. A shaker was used to sprinkle a mixture of 12 g corundum/m ² and 18 g glass beads/m ² into the melamine resin (grain size range: 80 - 110 µm). The grain size of the corundum according to the FEPA standard was F200. The resin was aired off over a distance of about ten meters.

Thereafter, in each case 20 g of liquid melamine resin/m ² (solids content about 65% by weight) were applied with a further five further roller applicators. A melamine resin in the same amount was also applied to the back. Hot air drying followed each application. The structure was then pressed in a short-cycle press at a pressing temperature of 200° C., a pressing pressure of 40 kg/cm ² and a pressing time of nine seconds. A sample from this production was tested for its behavior under abrasion stress using a Taber abrader in accordance with DIN EN 13329. For comparison, a sample was tested with which 18 g corundum/m ² had been scattered and 12 g glass beads/m ² had been applied via slurries in application units two to five. A value of 4700 μm resulted for the first sample. For the second sample, a value of 4150 µm.

Claims (12)

1. A process for producing an abrasion resistant laminate comprising the steps of:

   - Providing a wood-based panel which has at least one decorative layer on the top side, in particular as a printed decoration,

   - Applying at least one first resin layer to the at least one decorative layer on the top side of the wood-based panel,

   - Scattering a mixture of abrasion-resistant particles comprising corundum particles and glass beads onto the first resin layer on the top side of the wood-based panel;
   Whereby the proportion of the amount of scattered glass beads in the mixture of abrasion-resistant particles is 5 to 35 g/m² ,

   - Flashing-off of the first resin layer provided with the mixture of abrasion-resistant particles on the top side of the wood-based panel;

   - Applying of at least one further resin layer to the first resin layer provided with the mixture of abrasion-resistant particles on the flashed-off top side of the wood-based panel;

   - Pressing of the layered structure with the formation of a laminate.
2. Process according to claim 1, characterized in that the first resin layer is applied to a decorative layer provided with a protective layer.
3. Process according to one of the preceding claims, characterized in that the resin layers to be applied are liquid and/or powder.
4. Process according to one of the preceding claims, characterized in that the resin layers are based on melamine-formaldehyde resin, urea-formaldehyde resin or melamine-urea-formaldehyde resin.
5. Process according to one of the preceding claims, characterized in that the mixture of corundum particles and glass beads is spread in a total amount of between 20 and 40 g/m², preferably between 25 and 35 g/m² , particularly preferably of 30 g/m².
6. Process according to one of the preceding claims, characterized in that the corundum particles have a Mohs hardness of at least 9 and a grain size between 50 and 90 µm.
7. Process according to one of the preceding claims, characterized in that the proportion of the amount of corundum particles in the mixture of abrasion-resistant particles is 5 to 35 g/m², preferably 10 to 30 g/m², more preferably 8 to 15 g/m².
8. Process according to one of the preceding claims, characterized in that the glass beads have a Mohs hardness of at least 7 and a diameter of from 90 to 150 µm, from 90 to 110 µm.
9. Process according to one of the preceding claims, characterized in that the proportion of the amount of scattered glass beads in the mixture of abrasion-resistant particles is 10 to 30 g/m², in particular preferably 15 to 25 g/m².
10. Process according to one of the preceding claims, characterized in that at least one resin layer is applied to the lower side of the wood-based panel as a backing and is dried after application.
11. Process according to one of claims 1 to 9, characterized in that at least one resin-impregnated paper layer is applied to the lower side of the wood-based panel as a backing.
12. Process according to one of the preceding claims, characterized in that the pressing of the layered structure under the influence of pressure and temperature in the short-cycle press is carried out at temperatures between 150 and 250°C, preferably between 180 and 230°C, more preferably at 200°C, and at a pressure between 30 and 60 kg/cm², more preferably between 40 and 50 kg/cm².

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