EP3578385B1 - Method for refining a large format building panel - Google Patents

Description

The invention relates to a method for finishing a provided building board, in particular MDF or HDF, with a top side and a bottom side, at least in the top side in a first embossing step a relief as first strip-shaped depressions with two opposite side walls (5.1, 5.2), one this connecting bottom wall (5.3) and a depth, is embossed, and then a decoration is printed on the embossed upper side of the building board and the decoration is then sealed by applying an abrasion-resistant layer.

Such a method is, for example, from WO 2017/164806 A1 known. With this method, a floor panel is refined by pressing a bevel into the side edges starting from the top.
The ones from the EP 1 820 640 B1 known building panels are divided into individual panels after finishing and used, for example, as floor or wall and ceiling panels and are often provided with a wood, stone or fantasy decoration with an overlaid, three-dimensional surface. The divided panels have connecting means (tongue and groove) and are mostly equipped with locking means for locking adjacent panels in the horizontal and vertical direction (so-called click panels). The superimposition of decor and three-dimensional surface creates a realistic visual and haptic impression of the imitated material.

In the case of floor panels in particular, it is known that these are coated at least on the upper side and have a structure that is adapted to the decor.

Such a structure is called a decor-synchronous structure (embossed register). The decoration is either in the form of a paper layer laminated onto the carrier plate or as a layer of color printed directly on the carrier plate. The decor is also provided with a wear-resistant layer. For this purpose, either abrasion-resistant paper layers, so-called overlays, or, after hardening, abrasion-resistant lacquer or resin layers are used. The decor-synchronous structure is available as a three-dimensional surface structure and is embossed into the panel surface by means of a corresponding three-dimensionally structured press plate. The thermal components of the coating that can be activated under pressure melt and run and fill the three-dimensional structural embossing with curing. 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 activatable components and on the other hand by the pressing force.

In the case of laminate flooring, the abutting edges at which adjacent floor panels meet are problematic. Depending on the incidence of light, even the smallest differences in height cause optically unsightly shadows that negatively affect the overall appearance of a floor. The panels are also sensitive to moisture due to the core made of wood-based material. 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 produce irreversible swelling, since 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 manufacture of the panels. Adjacent panels should be able to lie tightly against one another, the panels should have an optically uniform appearance to a floor and precautions must be taken to ensure that spilled liquid cannot immediately flow into the connecting joints.

The EP 3 059 020 A1 discloses a method for producing a wood-based panel provided with a decorative layer, which provides at least a portion of treat their surface with water-based steam, sand the moistened surface and then provide at least one decorative layer.

The U.S. 4,579,767 A discloses a hardboard in which a tile pattern simulated by indentations running in the longitudinal direction and transverse direction is embossed and which is coated in such a way that tiles are imitated. A large number of individual tiles are each depicted on a hardboard. Several hardboard can be placed next to each other.

From the WO 2016/180643 A1 It is known to produce panels with recesses provided in the edge areas of the usable area by embossing at least two parallel grooves with a web that forms between them in a large-format wood-based panel and dividing the embossed board into individual smaller panels with a saw cut through the web .

The DE 10 2014 010 747 A1 describes a process for the production of building boards in which the last applied plastic layer is embossed with the circumferential contours of a plurality of panels in the melted plastic layer when the structure is pressed and, after the laminate has cooled, individual panels are cut out of the laminate along the circumferential contours that are at least embossed in the plastic layer become.

Proceeding from this problem, the method described at the outset is to be improved accordingly.

In order to avoid the aforementioned disadvantages and to be able to lower the side edges of the panels all the way round, a generic method according to the invention provides that the at least one further recess running at an angle transverse to the at least one recess is embossed. And the provided building board is divided into individual panels by making a saw cut in and along the depressions.
The top is then lowered at the side edges through the embossed depressions. The abutting edges of adjacent panels are opposite the So the top is lower. In such a case, a height offset cannot create shadows that are visually noticeable because all butt joints are lowered. Corresponding edge profiling enables a firm connection to be achieved between adjacent panels, which effectively prevents liquid from penetrating the butt joint too quickly.

If an MDF or HDF board is used as the building board, it is provided that its raw density profile (course of the density over the cross section of the board) compared to a conventional raw density profile, as it is, for example, from the EP 3 023 261 B1 is known to be lowered. When the fiber cake is pressed into a building board of the desired thickness, the greatest raw density results in the area of the top and bottom of the board. As a result of the heat input during pressing, a pressed skin forms on the top and bottom, which is also known as the "rotting layer". If the board has been pressed with a maximum density in the outer layers of ^{950-1000 kg / m 3} , it can be provided as mill-finished, that is, the pressed skin is not removed. However, it is also possible to at least partially grind the pressed skin on the upper side in order to reduce the density.

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

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

To create a printable surface, the top of the building board can be primed with a white paint before embossing the recess. At least the recess can be printed with a single-color or multi-color decoration by means of a digital printer. Instead of using a white paint for the primer, any other color can be used if necessary.

The first embossing step can be carried out by means of at least one calender roller. This has the advantage that the embossing step can be integrated into the production line. The embossing can then immediately follow the pressing of the wood-based panel in a contra press, in which the previously scattered fiber cake was pressed into a plate of the desired thickness, or it can precede 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 decor and an abrasion-resistant layer, the building board is laminated in a short-cycle press under pressure and 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 side walls without changing the position of the bottom wall in depth. During the coating, the side walls formed in the first embossing step are "rounded" so that these rounded areas are converted back into a flat surface by 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 already during the first embossing step and increases the bulk density. If the hardening agent is applied after the first embossing step, it hardens in the short-cycle press. The same also applies in the event that 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 stepped. In such a case, several first pressing steps with different pressing depths are carried out.

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 markings can consist of lines, circles, points, crosses or other graphic symbols. Lines are preferred. Using these markings, a camera system can be used to align the building board for the second embossing step and further subsequent processing steps.

The repeated embossing in 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 in the second embossing step, a structure can be embossed into the upper side, which at least partially runs synchronously with the decor, which is called "embossed register" in technical language.

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 aid 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 according to Figure 1 ;

Figure 3

- a schematic partial representation before the second embossing step;

Figure 4

- an enlarged partial view during the second embossing step;

Figure 5

- a schematic partial 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 density profile of an HDF board;

Figure 8

- the bulk 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 bulk density is lower than that of a conventional HDF board, as compared to the 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 upper side 2 of the building board 1, this is first heated to a temperature between 30 and 50 ° C. by means of steam. Then 10 to 50 g / m ³ , preferably 30 g / m ^{3 of} aqueous melamine resin are applied as a coating agent. This can be a standard impregnating 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 also be used as connecting means. Either it is a postforming resin or a standard impregnation resin, which is made more elastic by adding flexibilizers (e.g. 1,4-butanediol, caprolactam, polyglycol, etc.). A subsequent addition of the elasticizing agent should be of the order of about 3 to 7% by weight.

The building board 1 pretreated in this way is passed under one or more calender rollers 20 arranged one behind the other with embossing rings 21 arranged thereon parallel to one another. In a first embossing step, indentations 5, 6 with a depth T of up to 0.7 mm are embossed in the upper side 2 via the at least two embossed rings 21 in the longitudinal direction L and transverse direction Q. The line pressure of the embossed rings 21 is up to 300 N / mm and the surface temperature is up to 220 ° C. In this first embossing step, the coating agent is at least partially converted on the upper side 2, that is to say at least partially hardens and thereby increases the density. The depressions 5, 6 can be designed in a stepped manner, for example by using several calender rollers 20 with different embossing rings 21 and, for example, first 0.3 mm and then a further depth T of up to 0.7 mm is embossed. Between the embossing rings 21, a structure can be engraved in the jacket 22 of the calender roller 20, which structure is then embossed next to the depressions 5, 6 in the top side 3 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 by means of digital printing, the color dots of the digital printer being mapped 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 so that the wells 5, 6 are completely decorated. The decoration 3 can be single-colored or multi-colored and is applied in such a way that it runs at least partially synchronously with the structure that was first impressed. 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 lines 7.4 or other geometric figures. Using these markings 7, the building board 2 can be aligned using a camera system in order to carry out further processing steps.

After the decor printing, a counter-pull 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 scattered. The backing 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 once again dip into the embossed depressions 5, 6 when the structure is subsequently pressed and the side walls 5.1, 5.2 of the depressions 5, 6 that are rounded when the top 2 is coated are again embossed in order to set parallel and flat side walls 5.1, 5.2 in a second embossing step without changing the depth T of the depressions 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 made 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, in which the resins melt and bond with the building board 1. The temperature of the press plates 31, 33 is increased during the pressing, so that a surface temperature of 120 ° is obtained on the pressed part up to 180 ° C during the pressing process. The pressure curve takes place starting from a pressure build-up phase, transitioning into a holding phase and a pressure reduction phase. The embossing depth T will take place in the sense of a path control. The at least one calender roll 20 is integrated into the printing system or is located directly in front of it. For a meaningful design, at least two recesses 5, 6 in the longitudinal direction L and two in the transverse direction Q must be embossed in the first embossing step so that the side edges of the divided panels are all lowered.

List of reference symbols

1

Building board

2

Top

3

decor

4th

abrasion-resistant layer / overlay

5

deepening

5.1

Sidewall

5.2

Sidewall

5.3

Bottom wall

6th

deepening

7th

mark

7.1

Circles

7.2

cross

7.3

line

7.4

Line

8th

Return

9

Bottom 20 calender roll

21

Embossed ring

22nd

coat

30th

Short-cycle press

31

upper press plate

32

ledge-shaped elevation

33

lower press plate

α

angle

L.

Longitudinal direction

Q

Transverse direction

T

depth

Claims (17)

1. A method for finishing a supplied building panel (1) made of a wood-based material, in particular MDF or HDF, with an upper side (2) and a lower side (9), wherein, in a first embossing step, a relief is embossed at least into the upper side (2) as first strip-shaped depressions (5) with two opposing side walls (5.1, 5.2), a bottom wall (5.3) connecting said side walls and a depth (T), and subsequently a decorative pattern (3) is printed on the embossed upper side (2) of the building panel (1), and the decorative pattern (3) is then sealed by applying an abrasion-resistant layer (4), characterized in that additional depressions (6) extending at an angle (α) transversely to the first depressions (5) are embossed, and the large-size supplied building panel (1) is divided into individual panels by carrying out a saw cut in and along each of the depressions (5, 6).
2. The method according to claim 1, characterized in that the building panel (1) is an HDF panel, the upper side (2) of which features a press skin.
3. The method according to claim 1, characterized in that the press skin has a thickness of 0.3 to 0.5 mm.
4. The method according to one of the preceding claims, characterized in that the bulk density of the building panel (1) in the top layer that forms the upper side (2) is between 950 and 1.000 kg/m³.
5. The method according to one of the preceding claims, characterized in that a tempering agent is applied to the upper side (2) before or after embossing.
6. The method according to claim 5, characterized in that the tempering agent is an aqueous melamine resin.
7. The method according to one of the preceding claims, characterized 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).
8. The method according to claim 6, characterized in that the building panel (1) is heated using steam.
9. The method according to one of the preceding claims, characterized in that the upper side (2) is primed with a white paint before embossing the depressions (5, 6).
10. The method according to one of the preceding claims, characterized in that at least one depression (5) is printed with a single-colored or multicolored decorative pattern (16) using a digital printer (15).
11. The method according to one of the preceding claims, characterized in that the first embossing step can be conducted by at least one calendar roller (20).
12. The method according to one of the preceding claims, characterized in that once the structure is completed, the building panel (1) is laminated in a short-cycle press under pressure and at a temperature. In a second embossing step, it is embossed once again 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).
13. The method according to one of the preceding claims, characterized in that the depth (T) of the at least one depression (5, 6) is up to 0.7 mm.
14. The method according to one of the preceding claims, characterised in that the bottom wall (5.3) is designed in the form of steps.
15. The method according to one of the preceding claims, characterized in that markings (7.1, 7.2, 7.3, 7.4) can be printed on the bottom wall (5.3) of the at least one depression (5, 6).
16. The method according to claim 12, characterized in that re-embossing in the depressions (5, 6) in the second embossing step is conducted by means of strip-shaped elevations (32) on the press plate (31) of the short-cycle press (30).
17. The method according to one of the preceding claims, characterized in that a structure can be embossed into the upper side (2) which is at least partially synchronous with the decorative pattern (3).

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