EP3578383B1 - Method for refining a building panel - Google Patents

Description

The invention relates to a method for finishing a provided building board, in particular MDF or HDF, with an upper side and a lower side, with a relief being embossed at least in the upper side, and then a decoration being applied to the embossed upper side of the building board and the decoration then being applied an abrasion-resistant layer, with the following steps:
a) a decorative paper is applied to the upper side and an overlay paper is applied to the decorative paper as an abrasion-resistant layer, b) the underside is provided with a balancing sheet, c) the structure that is so widespread is fed to a short-cycle press and pressed together under pressure and temperature, d) during of pressing, the relief is embossed as at least one strip-shaped depression with two opposite side walls and a bottom wall connecting them into the top side with a depth.

Such a method is, for example, from WO 2016/180643 A1 known.

The EP 1 820 640 B1 describes a process for refining a large-format MDF building board that has a structure or relief embossed on its upper side, a decoration is applied to the embossed upper side and the decoration is then sealed with an abrasion-resistant layer.

The EP 3 023 261 B1 discloses a method for finishing a wood-based panel with an upper side and an underside by first applying a layer of liquid synthetic resin to at least the upper side or the underside, then placing at least one paper layer impregnated with a synthetic resin and this Structure is then pressed in a press under high pressure and high temperature, whereby the resin melts and connects to the wood-based panel.

Such 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 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 panels in the horizontal and vertical direction (so-called click panels). The superimposition 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 these are coated at least on the upper side and have a structure that is matched to the decor. Such a structure is referred to as a decor-synchronous structure (embossed register). The decoration is present either as a layer of paper laminated onto the carrier board or as a layer of color printed directly onto the carrier board. 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 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 correspondingly three-dimensionally structured pressing plate. The components of the coating that can be activated thermally and under pressure melt and run and fill the three-dimensional structural embossing while 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 quantity of activatable components and on the other hand by the pressing force.

With laminate floors, the abutting edges where adjacent floor panels abut are problematic. Depending on the incidence of light, even the smallest differences in height cause unsightly shadows that negatively affect the overall appearance of a floor. Due to the wood core, the panels are also sensitive to moisture. Liquid spilled on the floor must be wiped up as soon as possible to prevent the liquid from entering to avoid the connecting joint between the butt edges. If water penetrates, the wood fibers in the carrier board can expand and cause irreversible swelling, since the structure is destroyed by the swelling pressure of the wood and/or the adhesive is partially hydrolyzed. For this reason, it is important that special attention is paid to the subsequent abutting edges during the production of the panels. Adjacent panels should be able to lie firmly against one another, there should be an optically even appearance to a floor laid panels and care must be taken that spilled liquid can not immediately flow into the connecting joints.

The DE 10 2008 008 240 A1 discloses a carrier plate on the upper side of which water is applied prior to coating, which soaks in and causes a steam burst during subsequent pressing, as a result of which the top layer heats up very quickly. The heat and moisture bring about better plastic deformability and thus enable deeper stamping structures of the pressed sheet metal. The moisture also has the effect that the heat transfer from the pressing plates of the short-cycle press to the wood-based panel improves.

In the EP 3 059 020 A1 describes the treatment of a wood-based panel with steam, which can have a temperature of up to 60°C. This treatment should bring about a moist level of the carrier plate that is as uniform as possible in order to improve the primer for the printing. To do this, the moistened upper side is first sanded and then preheated to a temperature of approx. 45°C. This is followed by a first application of resin as a rolling base. A white primer is rolled onto this base.

The EP 2 106 903 A1 discloses a method for applying wear-inhibiting particles to a flat substrate, which is characterized in that the application takes place by means of an electrostatic field with a potential difference of at least 10 kV.

Based on this problem, the method described at the outset is to be improved accordingly.

• e) auf die Oberseite wird ein Vergütungsmittel aufgetragen,
• f) zumindest in den Bereichen, in denen das Relief geprägt werden soll, wird die Oberseite zur Erreichung einer Oberflächentemperatur von 30 bis 50 °C mit Heißdampf behandelt.

In order to avoid the aforementioned disadvantages, it is provided according to the invention in a generic method that the following steps are carried out before the decorative paper is placed:

• e) a coating agent is applied to the upper side,
• f) at least in the areas in which the relief is to be embossed, the upper side is treated with superheated steam to achieve a surface temperature of 30 to 50 °C.

The large-format panel is later divided into individual panels along the embossed indentations. The upper side is then lowered at the side edges by the embossed indentations. The abutting edges of adjacent panels are therefore lower than the upper side. In such a case, height offset cannot cause any shadows that are visually noticeable because all butt joints are lowered. Appropriate edge profiling can achieve a firm connection between adjacent panels, effectively preventing liquid from penetrating too quickly into the butt joint.

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

If an MDF or HDF board is used as a building board, it is provided that its raw density profile (development of the density over the cross section of the board) compared to a usual raw density profile, as is the case, for example, from EP 3 023 261 B1 is known to be lowered. When the fiber cake is pressed to form a building board of the desired thickness, the greatest bulk density is 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 a "rotting layer". The board can be supplied blank if it has been pressed with a maximum raw density in the cover layers of 950 - 1000 kg/m ³ that is, the pressed skin is not removed. It is also possible, however, to at least partially grind off the pressed skin, for example to a thickness of 0.3 mm, in order to reduce the density on the upper side.

The treatment agent ensures 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.

A surface temperature of up to 220° C. occurs when the at least one indentation is embossed.

If desired, one or more layers of paper can be applied as an underlay under the decorative paper. Like the decorative paper, these paper layers are impregnated with a melamine resin.

The finishing agent (melamine resin) applied to the upper side fixes the compacted fiber cake during pressing and curing and increases the bulk density in the top layer.

The depth of the at least one indentation is preferably up to 0.7 mm and can in particular be graduated, so that the bottom wall is designed in a stepped manner. In such a case, several 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, which can consist of lines, circles, dots, crosses or other graphic symbols, can be printed on the decorative paper where it comes to rest in the bottom walls of the at least one depression . Lines are preferred. Instead of printed markings, markings can also be embossed during pressing, which are transferred to the building board as matt or glossy areas or geometric figures with the help of the upper pressing plate. Such markings can also be provided on the edge of the decorative paper, so that they are on the outer edge of the coated building board.

In addition, a structure can be embossed into the upper side via the upper press plate, which structure runs at least partially synchronously with the decor, which is called "embossed register" in technical jargon.

Figur 1 -

eine perspektivische Teildarstellung einer großformatigen Bauplatte;

Figur 2 -

die Draufsicht auf die Bauplatte nach Figur 1;

Figur 3 -

eine schematische Teildarstellung;

Figur 4 -

eine vergrößerte Teildarstellung;

Figur 5 -

eine schematische Darstellung der in der Kurztaktpresse befindlichen Bauplatte;

Figur 6 -

ein übliches Rohdichteprofil einer HDF-Platte;

Figur 7 -

das Rohdichteprofil einer ersten großformatigen Bauplatte;

Figur 8 -

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 partial perspective view of a large-format building board;

Figure 2 -

the top view of the building board figure 1 ;

Figure 3 -

a schematic partial representation;

Figure 4 -

an enlarged partial view;

Figure 5 -

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

Figure 6 -

a typical bulk density profile of an HDF panel;

Figure 7 -

the bulk density profile of a first large format building panel;

Figure 8 -

the bulk density profile of a second large format building panel;

The starting point is a large format HDF panel with a length of 2,800 mm or 1,860 mm, a width of 2,070 mm and a thickness of 7 mm to 14 mm. The raw density is lower compared to a conventional HDF panel, as a comparison of the figure 6 with the figures 7 and 8th shows. In order to form a weak top layer that can be plastically deformed, the top layer peaks were reduced by at least 40 kg/m ³ compared to the standard. Good results have been achieved with a reduction of up to 60 kg/m ³ . The bulk density is then in the range from 950 to 1000 kg/m ³ . An example of the raw density profile of a conventional HDF board is in figure 6 shown. figures 7 and 8th show examples of raw density profiles of building boards used according to the invention.

The HDF board can be supplied blank, i.e. with the complete pressed skin. Preferably, however, the pressed skin is ground down to a thickness of about 0.3 mm in order to initially deliberately “make the top layer weak”.

First, 10 to 50 g/m ² , preferably 30 g/m ² , of aqueous melamine resin are applied as a finishing 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 as a solvent, other additives such as hardeners, wetting agents and the like can be present in the recipe. Alternatively, UF resin or mixtures of UF and melamine resin can also be used as a tempering agent. It is either a postforming resin or a standard impregnating resin that is made more elastic by adding flexibilizers (e.g. 1,4-butanediol, caprolactam, polyglycol, etc.). Subsequent addition of the elasticizing agent should be on the order of about 3 to 7% by weight. In order to be able to emboss depressions 5, 6 in the upper side 2 of the building board 1, this is then heated to a temperature of 30° C. to 50° C. by applying 10 to 30 g/m ² of steam.

After this pre-treatment, one or more resin-impregnated paper layers are placed on top 2 as underlay 4.1 (cf. figure 5 ) and then or only alone (cf. figure 3 ) a decorative paper 3 placed. The decorative paper 3 can be single-colored or multi-colored. Markings 7 can be provided on the decorative paper 3 . The markings 7 can be circles 7.1, crosses 7.2, lines 7.3 and dashes 7.4 or other geometric figures. The building board 2 can be aligned via these markings 7 via a camera system in order to carry out further processing steps.

A backing 8 is then placed on the underside 9 of the building board 1 and an overlay paper 4 is placed on the decorative paper 3 as an abrasion-resistant layer. This structure is then fed to a short-cycle press 30 whose upper press plate 31 is provided with raised areas 32 in the form of strips. The building board 1 is aligned via the markings 7 and a camera system, so that the elevations 32 shape the depressions 5, 6 when the structure is pressed, thereby forming parallel and planar side walls 5.1, 5.2 and the bottom wall 5.3. Between the strip-shaped elevations 32, the pressing plate 31 can be provided with an engraving, via which a structure is embossed into the upper side of the overlay during pressing, which is at least partially aligned synchronously with the decor (embossed register).

The pressing time in the short-cycle press 30 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 press plates 31, 33 is up to 200°C. The pressure curve proceeds from a pressure build-up phase into a holding phase and a pressure reduction phase. The embossing depth T will take place in the sense of a distance control.

For a meaningful design, at least two depressions 5, 6 in the longitudinal direction L and two in the transverse direction Q must be embossed so that the side edges of the divided panels are all lowered.

Reference List

1

build plate

2

top

3

decor

4

abrasion resistant layer / overlay paper

4.1

underlay

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

dash

8th

return

9

bottom

30

short-cycle press

31

upper press plate

32

bar-shaped elevation

33

lower press plate

a

angle

L

longitudinal direction

Q

transverse direction

T

depth

Claims (15)

1. A method for finishing a supplied building panel (1) made of a wood-based material, especially MDF or HDF, with a lower side (9) and an upper side (2) featuring a decorative pattern, said upper side being sealed by applying an abrasion-resistant layer (4) and a relief being embossed into at least the upper side (2), comprising the steps:

   (a) applying a decorative paper (3) to the upper side and an overlay paper to the decorative paper (3) as an abrasion-resistant layer (4),

   (b) providing the lower side (9) with a backing layer (8),

   (c) feeding the structure prepared in this way to a short-cycle press (30) and pressing it together at a pressure and a temperature,

   (d) during pressing, embossing the relief into the upper side (2) at a depth (T), said relief being embossed as at least one strip-shaped depression (5) with two opposite side walls (5.1, 5.2) and a connecting bottom wall (5.3),

   characterised in that before applying the decorative paper (3)

   (e) applying a tempering agent to the upper side (2) and

   (f) treating the upper side (2) with superheated steam, at least in the areas in which the relief is to be embossed, to achieve a surface temperature of 30 - 50 °C.
2. The method according to claim 1, characterised in that at least one further depression (6) extending at an angle (α) transverse to the at least one depression (5) is embossed.
3. The method according to claim 2, characterised in that longitudinally extending depressions and/or a plurality of transversely extending depressions (6) are embossed.
4. The method according to claim 1 or 2, characterised in that the building panel (1) is an HDF panel, the upper side (2) of which is provided with a press skin.
5. The method according to claim 4, characterised in that the press skin has a thickness of 0.3 to 0.5 mm.
6. The method according to one of the preceding claims, characterised in that the bulk thickness of the building panel (1) in the top layer that forms the upper side (2) is between 950 and 1.000 kg/m^3.
7. The method according to one of the preceding claims, characterised in that the tempering agent is an aqueous melamine resin.
8. The method according to claim 1, characterised in that at least 10 mg/m² of steam is applied.
9. 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.
10. The method according to one of the preceding claims, characterised in that the bottom wall (5.3) of the at least one depression (5, 6) is designed in the form of steps.
11. The method according to one of the preceding claims, characterised in that markings (7.1, 7.2, 7.3, 7.4) are embossed on the bottom wall (5.3) of the at least one depression (5, 6).
12. The method according to one of the preceding claims, characterised in that at least one resin-filled cellulose layer is applied as an underlay (4.1) before the decorative paper (3) is applied.
13. The method according to one of the preceding claims, characterised in that in addition to the relief, a structure is embossed that extends at least partially synchronously to the decorative pattern.
14. The method according to one of the preceding claims, characterised in that the embossing of the at least one depression (5) is achieved by at least one deep-structured press plate (31), preferably by means of strip-shaped elevations (32) on the press plate (31).
15. The method according to one of the preceding claims, characterised in that the building panel (1) is split into individual panels by carrying out a saw cut in and along each of the depressions (5, 6).

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