EP3578385A1 - Method for refining a large format building panel - Google Patents

Abstract

The invention relates to a method for finishing a building board (1) made of a wooden material, in particular MDF or HDF, provided with a large format, with a top (2) and a bottom (9), a relief being embossed at least into the top (2), and then a decor (3) is printed on the embossed top (2) of the building board (1) and the decor (3) is then sealed by applying an abrasion-resistant layer (4). According to the invention, the relief is embossed in a first embossing step as at least one strip-shaped depression (5) with two opposite side walls (5.1, 5.2), a bottom wall (5.3) connecting them and a depth (T).

Description

The invention relates to a method for finishing a large-scale provided building board, in particular MDF or HDF, with a top and bottom, wherein at least in the top of a relief is imprinted, and then printed on the embossed top of the building board a decor and the decor then by Applying an abrasion resistant layer is sealed.

Such a method is for example from the EP 1 820 640 B1 known.

Such structural panels are divided after finishing in individual panels and used for example as a floor or as wall and ceiling panels and are often provided with a wood, stone or fantasy decoration with superimposed, three-dimensional surface. The split panels have connecting means (tongue and groove) and are usually equipped with locking means for locking adjacent plates in the horizontal and vertical directions (so-called click panels). The superimposition of decor and three-dimensional surface creates a realistic visual and haptic impression of the imitated material.

In particular, in the case of floor panels, it is known that these are coated at least on the upper side and have a structure adapted to the decor. Such a structure is referred to as a decore-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 onto 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 curing abrasion resistant paint or resin layers are used. The decorsynchronous structure lies as a three-dimensional surface structure and is impressed by means of a correspondingly three-dimensionally structured press plate into the plate surface. The thermal and pressure-activatable constituents of the coating melt and run out and fill the three-dimensional structure embossing with hardening. The structure usually has a height of up to 500 μm. The number and the depth of the structures are limited on the one hand by the available amount of activatable components and on the other by the pressing force.

In laminate flooring, the abutting edges adjacent adjacent floor panels encounter are problematic. Depending on the incidence of light, even the smallest differences in height cause visually unsightly shadow formations that adversely affect the overall appearance of a floor. Due to the core of wood-based material, the panels are also sensitive to moisture. Liquid spilled on the floor must be wiped away as quickly as possible to prevent the liquid from penetrating into the joint between the abutting edges. Penetrates water, the wood fibers in the support plate can expand and produce irreversible swelling, as destroyed by the swelling pressure of the wood, the structure and / or the adhesive is partially hydrolyzed. For this reason, it is important that even during the production of the panels, the later edges are given special attention. Adjacent panels should be able to rest against each other, it should give a visually uniform appearance to a floor laid panels and care must be taken that spilled liquid can not flow immediately into the joints.

Starting from this problem, the method described above should be improved accordingly.

In order to avoid the aforementioned disadvantages, a generic method according to the invention provides that the relief is embossed in a first embossing step as at least one strip-shaped recess with two opposite side walls, a bottom wall connecting them and a depth. Preferably, a plurality of mutually parallel recesses is impressed.

Along the embossed depressions is later the division of the large format plate into individual panels. Due to the embossed depressions then the top is lowered at the side edges. The abutting edges of adjacent panels are therefore lower in relation to the upper side. Height offset can not cause shadowing in such a case, which attracts attention because all butt joints are lowered. By a corresponding edge profiling a firm connection between adjacent panels can be achieved, whereby the too rapid penetration of liquid is effectively avoided in the butt joint.

In order to be able to lower the side edges of the panels circumferentially, preferably at least one further recess extending at an angle transversely to the at least one depression is embossed. Here, too, a plurality of transverse depressions are preferably impressed, along which the division of the panels can then take place in the transverse direction.

If a MDF or HDF board is used as a building board, it is provided that their density profile (density profile over the cross-section of the plate) compared to a conventional density profile, as for example from the EP 3 023 261 B1 is known, is lowered. When pressing the fiber cake to a building board of desired thickness results in the largest density in the top and bottom of the plate. Due to the heat input during pressing, a pressing skin forms at the top and the bottom, which is also called "rotting layer". The plate, when pressed with a maximum apparent density in the cover layers of 950-1000 kg / m ³ , can be provided press-finished, that is, the press-skin is not removed. However, it is also possible to at least partially abrade the press skin to reduce the density at the top.

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

To facilitate embossing, 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 established. The heating of the building board can be done by means of water vapor.

To create a good printable surface, the top of the building panel can be primed with a white paint before embossing the recess. At least the recess can be printed by means of a digital printer with a monochrome or multi-colored decor. Instead of using a white color for the primer, any other color may be used as well.

The first embossing step may be carried out by means of at least one calendering roll. This has the advantage that the embossing step can be integrated into the production line. The embossing can then be followed directly by the pressing of the wood-based panel in a Kontipresse, in which the previously scattered fiber cake was pressed into a plate of desired thickness, connect, or upstream of the printing of the top in a printing system. The production is thereby optimized.

After completion of the construction, 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 high pressure and high temperature and is characterized in a second embossing step again in the at least one strip-shaped depression to the Forming the side walls to achieve 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 roundings are converted again into a plane surface by the second embossing step.

If the tempering agent has been applied before the first embossing step, and a sufficiently high temperature is achieved in the first embossing step, the melamine resin already hardens during the first embossing step and increases the bulk density. If the tempering agent is applied after the first embossing step, it hardens in the short-cycle press. The same applies in the case when in the first embossing step, a sufficiently high temperature is not achieved.

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

In order to align the building board during the subsequent further processing steps, marks may be printed on the bottom walls of the at least one depression, which may consist of lines, circles, points, crosses or other graphic characters. Preferably, lines are used. By means of these markings, the building board for the second embossing step and further subsequent processing steps can be aligned by means of a camera system.

The re-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 top side, a structure can be embossed in the first and / or second embossing step, which structure runs at least partially synchronously with the decoration, which is called "embossed register" in the 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;

With the aid of a drawing, an embodiment of the invention will be described in more detail below. Show it:

FIG. 1

- A partial perspective view of a large-sized building board;

FIG. 2

- The plan view of the building board after FIG. 1 ;

FIG. 3

a schematic partial representation before the second embossing step;

FIG. 4

- An enlarged partial view during the second embossing step;

FIG. 5

a schematic partial representation during the first embossing step;

FIG. 6

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

FIG. 7

a usual density profile of an HDF board;

FIG. 8

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

FIG. 9

- The density profile of a second large-sized 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 lowered compared to a conventional HDF board as a comparison of FIG. 7 with the FIGS. 8 and 9 shows. To form a weak cover layer, which can be plastically deformed, the cover layer tips were lowered compared to the standard by at least 40 kg / m ³ . Good results were achieved with a reduction of up to 60 kg / m ³ . The apparent density is in the range of 950 to 1000 kg / m ³ . An example of the density profile of a conventional HDF board is in FIG. 7 shown. FIGS. 8 and 9 show examples of gross density profiles of structural panels used in the invention.

In order to impress depressions 5, 6 in the top 2 of the building board 1, it is first heated to a temperature between 30 and 50 ° C by means of steam. Then, as a tempering agent, 10 to 50 g / m ³ , preferably 30 g / m ^{3 of} aqueous melamine resin is applied. It may be a standard impregnating resin having a solids content of 50 to 65 wt.%, Preferably 60 wt.% Act. In addition to water, other additives, such as hardeners, wetting agents and the like may be present in the solution. Alternatively, it is also possible to use UF resin as the bonding agent or UF and melamine resins in mixtures. Either it is a postforming resin or a standard impregnating resin that is more elasticized by the addition of flexibilizing agents (eg, 1,4-butanediol, caprolactam, polyglycol, etc.). A subsequent addition of the elastification agent should be on the order of about 3 to 7 wt.%.

The thus pre-treated building board 1 is passed under one or more calender rolls 20 arranged one behind the other with embossing rings 21 arranged parallel to one another. Here, in a first embossing step in the top 2 on the at least two embossing rings 21 in the longitudinal direction L and transverse direction Q extending recesses 5, 6 are impressed with a depth T of up to 0.7 mm. 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 on the upper side 2 is at least partially reacted, so it hardens at least partially, thereby increasing the bulk density. The recesses 5, 6 can be formed graduated, for example by several calender rolls 20 are used with different stamping 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 calendering roll 20, which is then embossed in the upper side 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 drying the base color, a decoration 3 is printed on the primer 11 by means of digital printing, wherein the color dots of 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 recesses 5, 6 are shown, so that the recesses 5, 6 are completely decorated. The decor 3 may be monochrome or multi-colored and is applied so that it runs at least partially synchronous with the structure previously embossed. Simultaneously with the decor 3 marks 7 are printed on the bottom wall 5.3. The marks 7 may be circles 7.1, crosses 7.2, lines 7.3 and lines 7.4 or other geometric figures. By means of these markings 7, the building board 2 can be aligned via a camera system for carrying out further processing steps.

After the decor print is placed on the bottom 9 of the building board 1 a return 8 and on the decor 3 an overlay paper 4. Instead of an overlay paper 4, a liquid overlay can also be applied in the roll application, into which corundum is mixed or scattered. Also, the return 8 can be applied liquid. This structure is then fed to a short-cycle press 30, the upper press plate 31 is provided with strip-shaped elevations 32. About the markers 7 and a camera system, the building board 1 is aligned, so that the ridges 32 in the subsequent compression of the structure again in the embossed recesses 5, 6 dive and the coated during the coating of the top 2 side walls 5.1, 5.2 of the wells 5, 6 again to adjust parallel and planar 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 FIG. 4 shows, the elevations 32 in the transition region from the side walls 5.1, 5.2 to the bottom wall 5.3 formed larger than the width of the recesses 5, 6, to safely 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 connect to the building board 1. The temperature of the press plates 31, 33 is increased during the pressing, so that a surface temperature of 120 ° to 180 ° C increases in the course of pressing on the compact. The pressure curve is carried out starting from a pressure build-up phase in a holding phase and a pressure reduction phase. The embossing depth T will be carried out in the sense of a path control. The at least one calender roll 20 is integrated into the printing system, or this immediately upstream. For a meaningful design must in the first 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 split panels are all lowered.

LIST OF REFERENCE NUMBERS

1

building board

2

top

3

decor

4

abrasion-resistant layer / overlay

5

deepening

5.1

sidewall

5.2

sidewall

5.3

bottom wall

6

deepening

7

mark

7.1

circles

7.2

cross

7.3

line

7.4

stroke

8th

return

9

Bottom 20 calender roll

21

ferrule

22

coat

30

Short-cycle press

31

upper press plate

32

strip-shaped elevation

33

lower press plate

α

corner

L

longitudinal direction

Q

transversely

T

depth

Claims (19)

Method for finishing a building board (1) made of wood-based material, in particular MDF or HDF, provided with a large format, with a top side (2) and a bottom side (9), wherein a relief is embossed at least in the top side (2), and then on the embossed one Top (2) of the building board (1) a decor (3) printed and the decor (3) is subsequently sealed by applying an abrasion-resistant layer (4), characterized in that the relief in a first embossing step as at least one strip-shaped recess ( 5) with two opposite side walls (5.1, 5.2), a bottom wall connecting them (5.3) and a depth (T) is embossed. A method according to claim 1, characterized in that at least one further at an angle (a) transversely to the at least one recess (5) extending recess (6) is impressed. A method according to claim 1 or 2, characterized in that the building board (1) is an HDF board whose top (2) is still provided with a press skin. A method according to claim 3, characterized in that the press skin has a thickness of 0.3 to 0.5 mm. Method according to one of the preceding claims, characterized in that the bulk density of the building board (1) in the top layer (2) forming the cover layer is between 950 and 1000 kg / m ³ . Method according to one of the preceding claims, characterized in that a tempering agent is applied to the top side (2) before or after embossing. A method according to claim 6, characterized in that the tempering agent is an aqueous melamine resin. Method according to one of the preceding claims, characterized in that the building board (1) is heated to 40 to 80 ° C before embossing, preferably 60 ° C and when embossing the at least one recess (5) has a surface temperature of up to 220 ° C. established. A method according to claim 7, characterized in that the heating of the building board (1) takes place by means of water vapor. Method according to one of the preceding claims, characterized in that before the embossing of the recess (5) the top (2) is primed with a white color. Method according to one of the preceding claims, characterized in that at least the recess (5) by means of a digital printer (15) with a single-color or multi-colored decor (16) is printed. Method according to one of the preceding claims, characterized in that the first embossing step is carried out by means of at least one calender roll (20). Method according to one of the preceding claims, characterized in that the building board (1) after completion of the structure (primer, decor, abrasion resistant layer) is laminated in a short-cycle press under high pressure and high temperature and in a second embossing step in the at least one strip-shaped Recess (5) is embossed to achieve the formation of the side walls (5.1, 5.2), without changing the position of the bottom wall (5.3) in the depth (T). Method according to one of the preceding claims, characterized in that the depth (T) of the at least one recess (5, 6) is up to 0.7 mm. Method according to one of the preceding claims, characterized in that the depth (T) is stepped. Method according to one of the preceding claims, characterized in that on the bottom wall (5.3) of the at least one recess (5, 6) marks (7.1, 7.2, 7.3, 7.4) are printed. A method according to claim 13, characterized in that the repeated embossing in the recess (5, 6) in the second embossing step by means of strip-shaped elevations (32) on the press plate (31) of the short-cycle press (30). Method according to one of the preceding claims, characterized in that the large-sized building board (1) is divided into individual panels, by in each case a saw cut is carried out in and along the recesses (5, 6). Method according to one of the preceding claims, characterized in that in the top (2) a structure is impressed, which at least partially in synchronism with the decor (3).

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