EP3885155B1 - Method for refining a large format building panel - Google Patents

Description

The invention relates to a method for refining a provided building board made of HDF with a top and a bottom, with a relief being embossed at least into the top, and then a decor being printed onto the embossed top of the building board and the decor then being applied by applying a liquid overlay is sealed as an abrasion-resistant layer, the relief being embossed in a first embossing step as at least one strip-shaped depression with two opposite side walls, a bottom wall connecting them and a depth, the building board having a maximum bulk density in the cover layers of 950 to 1000 kg /m ³ was pressed.

Such a procedure is, for example, from US 4,579,767 A known.

A similar procedure is from the EP 1 820 640 B1 known. To protect the building board against mechanical stress and damage caused by moisture, an abrasion-resistant layer of electron beam-curable paint or a melamine resin coating with or without abrasion-resistant particles is applied. Thanks to the final coating, the refined building board has a very homogeneous and closed surface.

After finishing, such building panels are divided into individual panels and used, for example, as floor or wall and ceiling panels and are often provided with a wood, stone or fantasy decor with a superimposed, three-dimensional surface. The divided panels have connecting means (tongue and groove) and are usually equipped with locking means for locking adjacent ones Panels equipped in horizontal and vertical directions (so-called click panels). The overlay of decor and three-dimensional surface creates a realistic visual and tactile impression of the imitated material.

In the case of floor panels in particular, it is known that they are coated at least on the top and have a structure that is adapted to the decor. Such a structure is referred to as a decor-synchronous structure (embossed register). The decor is present either as a paper layer laminated onto the carrier plate or as a color layer printed directly on the carrier plate. The decor also has a wear-resistant layer. For this purpose, either abrasion-resistant paper layers, so-called overlays, or abrasion-resistant lacquer or resin layers are used after curing. The decor-synchronous structure is present as a three-dimensional surface structure and is embossed into the plate surface using a correspondingly three-dimensionally structured pressed sheet. The thermal components of the coating that can be activated under pressure melt and run and fill the three-dimensional structural embossing as it hardens. The structure usually has a height of up to 500 µm. The number and depth of the structures are limited, on the one hand, by the available amount of components that can be activated and, on the other hand, by the pressing force.

With laminate floors, the abutting edges where adjacent floor panels meet are problematic. Depending on the incidence of light, even the smallest differences in height can cause visually unsightly shadows that negatively affect the overall appearance of a floor. Due to the core made of wood material, the panels are also sensitive to moisture. Any liquid spilled on the floor must be wiped away as quickly as possible to prevent the liquid from penetrating the joint between the abutting edges. If water penetrates, the wood fibers in the carrier board can expand and cause irreversible swelling, as the swelling pressure of the wood destroys the structure and/or the adhesive is partially hydrolyzed. For this reason, it is important that special attention is paid to the later abutting edges during the production of the panels. Adjacent panels should be able to fit tightly together, Panels laid on a floor should have a visually uniform appearance and precautions must be taken to ensure that spilled liquid cannot immediately flow into the connecting joints.

The WO 2017/164806 A1 discloses a method for refining a building board, in which a recess embossed into the top is printed using a digital printer.

The EP 3 059 020 A1 discloses a method for producing a wood-based panel, the surface of which is moistened in sections with water-containing steam and then sanded in this section before a decorative layer is applied.

Based on this problem, the method described at the beginning should be improved accordingly.

In order to avoid the aforementioned disadvantages, in a generic method according to the invention it is provided that the building board is provided in a press-finished manner and its upper side is also provided with a press skin, further depressions running at an angle transversely to the first recesses are embossed, and the large-format building board provided is divided into individual panels by making a saw cut in and along the recesses and either mixing or sprinkling corundum into the liquid overlay.

The press skin preferably has a thickness of 0.3 to 0.5 mm.

The large-format panel is later divided into individual panels along the embossed recesses. The embossed recesses then lower the top at the side edges. The abutting edges of adjacent panels are therefore lower than the top. In such a case, a height offset cannot cause shadows that are visually noticeable because all butt joints are lowered. Through appropriate edge profiling, a firm connection between adjacent panels can be achieved, which effectively prevents liquid from penetrating too quickly into the butt joint.

In order to be able to lower the side edges of the panels all around, at least one further depression is preferably embossed at an angle transversely to the at least one depression. Here too, a plurality of transverse depressions are preferably embossed, along which the panels can then be divided in the transverse direction.

It is envisaged that the bulk density profile (the course of the density over the cross section of the plate) is compared to a usual bulk density profile, such as that from EP 3 023 261 B1 is known, is lowered. When the fiber cake is pressed into a building board of the desired thickness, the greatest bulk density results in the area of the top and bottom of the board. Due to the heat input during pressing, a pressed skin forms on the top and bottom, which is also called the “rotting layer”. The plate is provided in a press-finished state, which means that the press skin is not removed.

Before or after embossing, a tempering agent can be applied to the top, which is preferably an aqueous melamine resin. The remuneration agent ensures that the previously reduced bulk density on the top (in the top layer) is increased again in order to achieve sufficient strength properties on the later panels.

To make embossing easier, the building board is heated to 40 to 80 ° C, preferably 60 ° C, and when embossing the at least one depression, a surface temperature of up to 220 ° C is achieved. The building board can be heated using steam.

To create a good printable surface, the top of the build plate can be primed with a white paint before embossing the recess. At least the depression can be printed with a single-color or multi-color decoration using a digital printer. Instead of using white paint as a primer, any other color can be used if necessary.

The first embossing step can be carried out using at least one calender roll. This has the advantage that the embossing step is integrated into the production line can be. The embossing can then immediately follow the pressing of the wood-based panel in a continuous press, in which the previously spread fiber cake was pressed into a panel of the desired thickness, or can be carried out before the printing of the top in a printing system. This optimizes production.

After completion of the structure, which consists of at least a primer, the decoration and an abrasion-resistant layer, the building board is laminated in a short-cycle press under high pressure and high temperature and in a second embossing step it is embossed again into the at least one strip-shaped recess in order to create the To achieve the formation of the side walls without changing the depth of the position of the bottom wall. During the coating, the side walls formed in the first embossing step are "rounded" so that these roundings are converted back into a flat surface in the second embossing step.

If the tempering agent was applied before the first embossing step and a sufficiently high temperature is achieved in the first embossing step, the melamine resin hardens during the first embossing step and increases the raw density. If the tempering agent is applied after the first embossing step, it hardens in the short-cycle press. The same also applies if a sufficiently high temperature is not achieved in the first embossing step.

The depth of the at least one depression is preferably up to 0.7 mm and can in particular be stepped, so that the bottom wall is designed in a step-shaped manner. In such a case, several first pressing steps are carried out with different pressing depths.

In order to be able to align the building board during the subsequent further processing steps, markings can be printed on the bottom walls of the at least one recess, which can consist of lines, circles, dots, crosses or other graphic symbols. Lines are preferred. Using these markings, the building board can be aligned for the second embossing step and further subsequent processing steps using a camera system.

The repeated embossing into the recess in the second embossing step is preferably carried out in a short-cycle press in which strip-shaped elevations are applied to the press plate.

In the first and/or second embossing step, a structure can be embossed into the top, which runs at least partially synchronously with the decor, which is known in technical language as an “embossed register”.

Figur 1 -

eine perspektivische Teildarstellung einer großformatigen Bauplatte;

Figur 2 -

die Draufsicht auf die Bauplatte nach Figur 1;

Figur 3 -

eine schematische Teildarstellung vor dem zweiten Prägeschritt;

Figur 4 -

eine vergrößerte Teildarstellung während des zweiten Prägeschrittes;

Figur 5 -

eine schematische Teildarstellung während des ersten Prägeschrittes;

Figur 6 -

eine schematische Darstellung der in der Kurztaktpresse befindlichen Bauplatte;

Figur 7 -

ein übliches Rohdichteprofil einer HDF-Platte;

Figur 8 -

das Rohdichteprofil einer ersten großformatigen Bauplatte;

Figur 9 -

das Rohdichteprofil einer zweiten großformatigen Bauplatte;

An exemplary embodiment of the invention will be described in more detail below with the help of a drawing. Show it:

Figure 1 -

a perspective partial representation of a large-format building board;

Figure 2 -

the top view of the building board Figure 1 ;

Figure 3 -

a partial schematic representation before the second embossing step;

Figure 4 -

an enlarged partial representation during the second embossing step;

Figure 5 -

a partial schematic representation during the first embossing step;

Figure 6 -

a schematic representation of the building board located in the short-cycle press;

Figure 7 -

a common bulk density profile of an HDF board;

Figure 8 -

the raw density profile of a first large-format building board;

Figure 9 -

the bulk density profile of a second large-format building board;

The starting point is a large-format HDF board with a length of 2,800 or 1,860 mm, a width of 2,070 mm and a thickness of 7 to 14 mm. The raw density is reduced compared to a usual HDF board as a comparison Figure 7 with the Figures 8 and 9 shows. To form a weak top layer that can be plastically deformed, the top layer tips were lowered by at least 40 kg/m ³ compared to the standard. Good results were achieved with a reduction of up to 60 kg/m ³ . The bulk density is in the range from 950 to 1000 kg/m ³ . An example of the bulk density profile of a conventional HDF board is in Figure 7 shown. Figures 8 and 9 show examples of bulk density profiles of building boards used according to the invention.

In order to be able to emboss depressions 5, 6 in the top 2 of the building board 1, it is first heated to a temperature between 30 and 50 ° C using steam. Then 10 to 50 g/m ³ , preferably 30 g/m ³ , of aqueous melamine resin are applied as a modifier. This can be a standard impregnation resin with a solids content of 50 to 65% by weight, preferably 60% by weight. In addition to water, other additives such as hardeners, wetting agents and the like can be present in the solution. Alternatively, UF resin or a mixture of UF and melamine resin can be used as a connecting agent. Either it is a postforming resin or a standard impregnation resin that is made more elastic by adding flexibilizing agents (e.g. 1,4-butanediol, caprolactam, polyglycol, etc.). A subsequent addition of the elasticizing agent should be in the order of approximately 3 to 7% by weight.

The building board 1 pretreated in this way is passed under one or more calender rolls 20 arranged one behind the other with embossing rings 21 arranged parallel to one another. In a first embossing step, depressions 5, 6 with a depth T of up to 0.7 mm are embossed into the top side 2 via the at least two embossing rings 21 in the longitudinal direction L and transverse direction Q. The line pressure of the embossing rings 21 is up to 300 N/mm and the surface temperature is up to 220 ° C. In this first embossing step, the tempering agent is at least partially implemented on the top side 2, i.e. it hardens at least partially and thereby increases the raw density. The depressions 5, 6 can be formed in steps, for example by using several calender rolls 20 with different embossing rings 21 and, for example, first embossing 0.3 mm and then a further depth T of up to 0.7 mm. Between the embossing rings 21, a structure can be engraved into the jacket 22 of the calender roll 20, which is then embossed into the top 3 next to the depressions 5, 6 in the first embossing step.

After the first embossing step, the top 2 is primed with a white base color. After the base color has dried, a decor 3 is printed onto the primer 11 using digital printing, with the color dots from the digital printer not only on the flat top 2, but also on the side walls 5.1, 5.2 and the bottom wall 5.3 of the strip-shaped depressions 5, 6 are depicted, so that the depressions 5, 6 are completely decorated. The decor 3 can be single-colored or multi-colored and is applied in such a way that it is at least partially synchronous with the previously embossed structure. At the same time as the decor 3, markings 7 are printed on the bottom wall 5.3. The markings 7 can be circles 7.1, crosses 7.2, lines 7.3 and dashes 7.4 or other geometric figures. Using these markings 7, the building board 2 can be aligned using a camera system to carry out further processing steps.

After the decor has been printed, a counterweight 8 is placed on the underside 9 of the building board 1 and an overlay paper 4 is placed on the decor 3. Instead of an overlay paper 4, a liquid overlay can also be applied by roller application, into which corundum is mixed or sprinkled. The countermove 8 can also be applied in liquid form. This structure is then fed to a short-cycle press 30, the upper press plate 31 of which is provided with strip-shaped elevations 32. The building board 1 is aligned using the markings 7 and a camera system, so that the elevations 32 are immersed again in the embossed recesses 5, 6 during the subsequent pressing of the structure and the side walls 5.1, 5.2 of the recesses 5, 6, which are rounded when the top side 2 is coated, are embossed again in order to adjust parallel and flat side walls 5.1, 5.2 in a second embossing step without changing the depth T of the recesses 5, 6 or the position of the bottom walls 5.3. How Figure 4 shows, the elevations 32 in the transition area from the side walls 5.1, 5.2 to the bottom wall 5.3 are designed to be larger than the width of the recesses 5, 6 in order to reliably form the lower edges of the recesses 5, 6.

The pressing time in the second embossing step is between 10 and 30 seconds, preferably 12 to 15 seconds, during which the resins melt and bond to the building board 1. The temperature of the pressing sheets 31, 33 is increased during pressing, so that a surface temperature on the compact increases from 120° to 180° C. during the pressing process. The pressure progression takes place starting from a pressure build-up phase, transitioning into a holding phase and a pressure reduction phase. The embossing depth T will be in the sense of a path control. The at least one calender roller 20 is integrated into the printing system or is located immediately upstream of it. For a sensible design, first of all, Embossing step at least two in the longitudinal direction L and two in the transverse direction Q depressions 5, 6 are embossed so that the side edges of the divided panels are all lowered.

Reference symbol list

1 Building plate 2 Top 3 decor 4 abrasion-resistant layer/overlay 5 deepening 5.1 side wall 5.2 side wall 5.3 bottom wall 6 deepening 7 mark 7.1 Circles 7.2 Cross 7.3 line 7.4 dash 8th countermove 9 bottom 20 Calender roll 21 Embossing ring 22 Coat 30 Short cycle press 31 upper press plate 32 strip-shaped elevation 33 lower press plate α angle L Longitudinal direction Q Transverse direction T depth

Claims (13)

1. A method for finishing a supplied building panel (1) made of HDF, with an upper side (2) and a lower side (9), a relief being embossed at least into the upper side (2) and a decorative pattern (3) subsequently being printed onto the embossed upper side (2) of the building panel (1) and the decorative pattern (3) then being sealed by applying a liquid overlay as an abrasion-resistant layer (4), wherein the relief is embossed in a first embossing step as at least one strip-shaped depression (5) with two opposing side walls (5.1, 5.2), a bottom wall (5.3) connecting said side walls and a depth (T), the building panel (1) having been pressed with a maximum bulk density of 950 and 1000 kg/m3 in the top layers, characterised in that the building panel (1) is provided in press-finished condition and its upper side (2) also features a press skin, additional depressions (6) extending at an angle (α) transversely to the first depressions (5) are embossed, the building panel (1) is divided into individual panels by carrying out a saw cut in and along each of the depressions (5, 6), and corundum is either mixed into or scattered over the liquid overlay.
2. The method according to claim 1, characterised in that the press skin has a thickness of 0.3 to 0.5 mm.
3. The method according to one of the preceding claims, characterised in that a tempering agent is applied to the upper side (2) before or after embossing.
4. The method according to claim 5, characterised in that the tempering agent is an aqueous melamine resin.
5. The method according to one of the preceding claims, characterised in that the building panel (1) is heated to 40 to 80°C, preferably 60°C, before embossing and a surface temperature of up to 220°C is achieved when embossing the at least one depression (5).
6. The method according to claim 6, characterised in that the building panel (1) is heated using steam.
7. The method according to one of the preceding claims, characterised in that the upper side (2) is primed with a white paint before embossing the depressions (5, 6).
8. The method according to one of the preceding claims, characterised in that at least one depression (5) is printed with a single-coloured or multicoloured decorative pattern (16) using a digital printer (15).
9. The method according to one of the preceding claims, characterised in that the first embossing step is carried out using at least one calendar roller (20).
10. The method according to one of the preceding claims, characterised in that, once the structure is completed, the building panel (1) is laminated in a short-cycle press under pressure and at a temperature, and in a second embossing step, it is embossed in the strip-shaped depressions (5) to achieve the formation of the side walls (5.1, 5.2) without changing the position of the bottom wall (5.3) in terms of depth (T).
11. The method according to one of the preceding claims, characterised in that the depth (T) of the at least one depression (5, 6) is up to 0.7 mm.
12. The method according to one of the preceding claims, characterised in that the bottom wall (5.3) is designed in the form of steps.
13. The method according to one of the preceding claims, characterised in that markings (7.1, 7.2, 7.3, 7.4) are printed on the bottom wall (5.3) of the at least one depression (5, 6).

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