EP2730430B1 - Method for treating a composite wood board and structural panel comprising a core of wooden material - Google Patents

Description

The invention relates to a method for treating a wood-based panel to achieve a tack-free surface after a decor has been printed on at least one upper side of the wood-based panel, and a structural panel with a core of wood-based material (wood-based panel), the surface of which was treated by the method.

Such wood-based panels are widely used and used in many different fields. A particularly large field of application is the use as a floor panel. In particular, in this use, the wood-based panels provided with the decor are exposed to a high load. To withstand these stresses, the decorative layer must be covered with a protective layer. This usually consists of a synthetic resin, for example melamine resin, to which various additives have been added. Due to the various layers applied to the wood-based panel, tensile stresses occur which can lead to a tipping of the wood-based panel. Therefore, both top and bottom of the wood-based panel must be coated to allow these forces to occur evenly on both sides and so avoid a bowl.

From the EP 2 338 693 B1 It is known, on the top and / or bottom of the wood-based panel having the decor, a first upper resin layer applying corundum particles to dry this upper resin layer and then to apply a second resin layer containing cellulose. The second resin layer is then dried, and on this second resin layer, a third resin layer containing glass particles and dried.

The EP 1 339 545 B1 discloses a wear protection layer based on synthetic resin, with which the surfaces of furniture or floors consisting of a decor paper and possibly other overlapping papers can be protected against wear. This wear protection layer contains resin particles having a Mohs hardness of at least 6 and further compact and substantially cut edge-free, round solid particles in the form of spheres having a Mohs hardness of at least 5. The latter spheres may be glass spheres.

The EP 1 512 468 B1 describes a method for sealing a building board made of wood or a wood-based material. Here, liquid resin is first applied to the top and then dried. Subsequently, the building board is pressed under the influence of temperature, the resin at least partially melts. According to the EP 2 098 304 A2 In addition, a relief can be embossed in the melting resin, which corresponds to the decor of the top of the wood-based panel.

In all known methods, a foamed layer of melamine resin and cellulose fibers is applied to the coated directly with a decor large-sized wood-based panel, which is actively dried after the order to protect the decor and thus make the plate stackable and storable. Under a directly coated with a decorative plate is a plate to understand on the top of a decor is printed one or more layers, so no decorative paper is used. The decor can be printed directly on the top of the wood-based panel, or between the Top and the decorative layer may be provided a primer layer.

A conventional layer structure on top of a wood-based panel consists of 15 to 40 g / m ² primer, which consists of an aqueous melamine resin. An aqueous white lacquer in an amount of 20 to 30 g / m ^{2 is} applied to this primer layer as white base. The decor usually consists of two, three or four applied to the white background decorative prints. This decor is then covered with a resist consisting of an aqueous melamine resin-cellulose fiber mixture which is foamed directly before application. The resist is applied in an amount of 10 to 15 g / m ² .

The topcoat is necessary to protect the decoration during further processing and coating of the wood-based panel in the subsequent manufacturing process. The plates are not necessarily finished in the run, but also stored and stacked on each other. The covering is therefore necessary, but its mission is particularly critical, especially with effects in downstream processes that lead to product-critical defects up to waste. In this case, there is the field of tension between a too little foamed melamine resin-cellulose fiber mixture, which can lead to sticking between decorated wood-based panels within a stack, and too much foamed melamine resin-cellulose fiber mixture, which can lead to graying of the decor, but only after the lamination can be seen in a short-cycle press.

Various attempts to adjust the foaming and keep constant have failed because the processing process in time and spatially apart, whereby a regulatory intervention is impossible or only with an unreasonable effort is possible.

The WO 2008/005228 A2 describes a composition for a wear resistant coating of a laminate. This coating may consist of a resin containing corundum and glass particles. The corundum and glass particles are referred to as "natural glass" and should have been formed by volcanic activity (cf., [0028]) and in particular also have no spherical form (cf., [0031]).

The US 2009/0087643 A1 describes a method for producing a decorative laminate, in which a slurry is applied to a resin-impregnated decorative paper (see [0025]). This mass, referred to as sludge, may comprise cellulose and / or glass spheres in order to protect the press plates of the press in which the laminate is subsequently pressed against wear (see [0025]). It is expressly disclosed in [0026] that the thermosetting resin composition additionally contains a mixture of wear-resistant particles, which may consist of various materials. The mass, which is thus applied to the decor, contains abrasive particles and may additionally comprise cellulose and / or glass beads.

From the WO 93/01935 A1 For example, a decorative cover layer for a laminate is known, which is composed of different thermoplastic or thermosetting polymers.

The WO 2007/079547 A1 describes a method and apparatus for making a decorative laminate that consists of one or more resin-impregnated papers that are pressed onto a substrate. The resin-impregnated papers, substrate and / or laminate may be heat treated prior to compression to reduce the amount of liquid in the paper. The heat treatment can be done via infrared radiators.

Since the interest in a safe process for the production of laminates is of course high, the invention is based on the object, the beginning described method to the effect that on the one hand a tack-free surface of the wood-based panel is achieved in order to stack the semi-finished in the further processing process, and on the other hand to achieve a surface whose color deviation-free further processing is certainly possible.

This object is achieved in that a cellulose-free cover layer of melamine resin is applied to the decor, in which glass beads are mixed, and this cover layer is dried before a wear protection layer is applied to them.

The use of glass beads instead of cellulose in the melamine resin brings significant advantages in terms of processability and technological values of the product. The melamine resin is preferably a melamine-formaldehyde resin (M / F resin) in which the cellulosic fibers admixed by the prior art are split into shorter fiber chains, that is, swell. By swelling the cellulose fibers, the viscosity of the melamine resin is drastically increased, which makes its use problematic in the long term. In the glass beads, especially when they are preferably used in silanized form, no disturbing side reactions are observed, which adversely affect the flow properties of the melamine resin. While most of the cellulose is physically bound to the melamine-formaldehyde resin network, the silane groups of the glass spheres form a strong covalent bond with the hydroxy groups of the resin. Thus, the glass is chemically incorporated into the three-dimensional polymer network and thus stronger, resulting in a better abrasion and scratch resistance compared to cellulose fibers. In addition, the glass itself has a higher hardness than cellulose fibers. The glass spheres blended into the melamine resin produce a uniform, rough surface which is of great importance for further processing but does not stick.

In principle, a rough surface can also be produced with cellulose, but the correspondingly coated wood-based panels tend to adhere within a stack during storage and are therefore no longer suitable for further processing. The gluing of the wood-based panels is carried out by a heat-catalytic condensation between the cellulose fibers in the resin and the wood fibers of the upper panel. When using silanized glass beads no sticking can occur. In addition, the glass beads are much more temperature stable, so that in the further lamination process when pressing the wood-based panel, the top layer is not cloudy.

The drying of the cover layer is preferably carried out actively in order to shorten the production time.

Preferably, the melamine resin-glass ball mixture is applied in an amount of 10 to 30 g / m ² , preferably 12 to 20 g / m ² . The proportion of glass beads in the mixture is 12 to 16% by weight.

The diameter of the blended glass beads is in the range of 60 to 110 microns, more preferably in the range of 60 to 90 microns or from 70 to 110 microns.

A building board, in particular a floor panel which has been coated from a wood-based panel produced by the method described, is characterized by a core of wood-based material, a decor printed on at least one top side of the core and a cover layer covering the decor and based on melamine resin coated on the top layer wear protection layer with abrasive particles, in which the cover layer is cellulose-free and has glass beads, and the wear protection layer consists of a melamine resin-corundum-cellulose fiber mixture.

The abrasive particles in the wear protection layer are preferably corundum. However, glass beads can also be used, as is already known in principle from the previously described prior art.

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

Figur 1 -

einen schematischen Querschnitt durch eine Holzwerkstoffplatte;

Figur 2 -

die Einzelheit II nach Figur 1.

Show it:

FIG. 1 -

a schematic cross section through a wood-based panel;

FIG. 2 -

the detail II after FIG. 1 ,

The coating of the wood-based panel is below based on the FIG. 1 to be discribed.

On the core of wood fibers, shavings or a wooden material-plastic mixture existing core 1 is first applied to the top of a primer layer 2 of 15 to 40 g / m ^{2 of} an aqueous melamine resin. On top of this primer layer 2, a white base 3 is applied as a further printing base, in which 20 to 30 g / m ^{2 of} an aqueous white paint are applied. The decor 7 consists of several, preferably two, three or four successively applied decorative prints that are applied for example in offset printing or by means of a digital printer (inkjet printer). The cover layer 8 consists of an aqueous melamine resin-glass ball mixture, with an application amount of 10 to 30 g / m ² . The melamine resin is preferably a melamine-formaldehyde resin, and the glass beads 5 blended in the resin have a diameter of 60 to 90 μm or 70 to 110 μm. Of course, the diameter range can also be from 60 to 110 μm. After the cover layer 8 has been actively dried, a wear protection layer 4 of a melamine resin-corundum-cellulose fiber mixture in an amount of 30 to 50 g / m ^{2 is} applied in a subsequent coating step. After drying this last coating, the wood-based panel is pressed in a short-cycle press under the action of a high pressure and a high temperature. This wood-based panel can then in further Processing steps are divided into panels, at the side edges then a spring / groove profiling can be worked. Spring and groove can be provided with integrated locking and latching means to lay the panels then glueless.

• Versuchsdurchführung 1 "AC3"
  • Harzgemisch Auftrag von 12 g/m² enthaltend 12 Gew% Glas der Spezifikation 60 bis 90 µm, führt zu einem Abrieb von 2400 Umdrehungen
  • Harzgemisch Auftrag von 16 g/m² enthaltend 12 Gew% Glas der Spezifikation 60 bis 90 µm, führt zu einem Abrieb von 2600 Umdrehungen
  • Harzgemisch Auftrag von 20 g/m² enthaltend 12 Gew% Glas der Spezifikation 60 bis 90 µm, führt zu einem Abrieb von 2800 Umdrehungen
• Versuchsdurchführung 2 "AC4"
  • Harzgemisch Auftrag von 12 g/m² enthaltend 12 Gew% Glas der Spezifikation 70 bis 110 µm, führt zu einem Abrieb von 4200 Umdrehungen
  • Harzgemisch Auftrag von 16 g/m² enthaltend 14 Gew% Glas der Spezifikation 70 bis 110 µm, führt zu einem Abrieb von 4400 Umdrehungen
  • Harzgemisch Auftrag von 20 g/m² enthaltend 16 Gew% Glas der Spezifikation 70 bis 110 µm, führt zu einem Abrieb von 4600 Umdrehungen

Experiments have shown that with a melamine resin-glass ball mixture a significantly higher amount, namely 10 to 30 g / m ² , preferably 12 to 20 g / m ² can be applied as with a conventional melamine resin-cellulose mixture. According to DIN EN 13329 different types of wear AC are distinguished. AC3 requires at least 2000 revolutions and AC4 at least 4000 revolutions. The following experimental procedures yielded the following results:

• Experimental procedure 1 "AC3"
  • Resin mixture Order of 12 g / m ² containing 12 wt% glass of specification 60 to 90 microns, resulting in an abrasion of 2400 revolutions
  • Resin mixture order of 16 g / m ² containing 12 wt% glass of specification 60 to 90 microns, resulting in an abrasion of 2600 revolutions
  • Resin mixture Order of 20 g / m ² containing 12 wt% glass of the specification 60 to 90 microns, resulting in an abrasion of 2800 revolutions
• Experimental procedure 2 "AC4"
  • Resin mixture Order of 12 g / m ² containing 12 wt% glass of the specification 70 to 110 microns, resulting in an abrasion of 4200 revolutions
  • Resin mixture order of 16 g / m ² containing 14 wt% glass of the specification 70 to 110 microns, resulting in an abrasion of 4400 revolutions
  • Resin mixture Order of 20 g / m ² containing 16 wt% glass of the specification 70 to 110 microns, resulting in an abrasion of 4600 revolutions

• Anlagegeschwindigkeit 60 bis 100 m/min.
• Um den Prozess konstant zu halten, war die Fertigungshalle klimatisiert und die Lackführung temperiert. Außerdem erfolgte die Dosierung und Überwachung automatisch.

When applying the top coat 8, the following conditions prevailed:

• Plant speed 60 to 100 m / min.
• In order to keep the process constant, the production hall was air-conditioned and the paint run tempered. In addition, the dosage and monitoring was done automatically.

As the experiments described above, compared to conventionally coated plates, a higher abrasion resistance, the micro-scratch resistance was improved and the chemical integration of the glass into the melamine resin resulted in a uniform surface distribution, which has also set an improved surface density against impact load. Overall, the implementation of the method thus leads to a simple and safe operation of the manufacturing process and the end product to improve the resistance of the surface and thus improved performance characteristics of the building board.

Within the coating process not only the decor 7 is sealed, but it can also be stacked up to 1000 plates, without these stick together. It has been shown that such stacks can be stored up to 180 days and already at 35 ° C, a stacking is possible. The degree of condensation is not measurable. Preferably, the storage of the stack takes place at 25 ° C and a humidity of 40 to 60%. The better transparency than with cellulose, a sharper décor print and better colors of the décor are fully accentuated by the melamine-glass sphere mixture, in particular because a uniformly closed surface sets in.

LIST OF REFERENCE NUMBERS

1

core

2

primer layer

3

White foundation

4

Wear protection layer

5

glass beads

6

Abrasive particles

7

decor

8th

topcoat

Claims (10)

1. Method for treating a wood material board in order to achieve an adhesive-free surface after a decoration (7) has been printed onto at least a top side of the wood material board,
   characterized in that
   a cellulose-free outer layer (8) made of melamine resin into which glass spheres (5) have been mixed is applied to the decoration (7), and this outer layer (8) is dried before a wear-resistant layer (4) is applied to the top layer (8).
2. Method according to Claim 1, characterized in that the drying of the outer layer (8) is carried out actively.
3. Method according to Claim 1, characterized in that the glass spheres (5) used are silanized.
4. Method according to Claim 1 or 3, characterized in that the melamine resin-glass sphere mixture is applied in a quantity of 10 to 30 g/m², preferably 12 to 20 g/m².
5. Method according to Claim 1 or 4, characterized in that the proportion of glass spheres (5) in the mixture is 12 to 16% by weight.
6. Method according to Claim 5, characterized in that the diameter of the glass spheres (5) lies in the range from 60 to 90 µm.
7. Method according to Claim 5, characterized in that the diameter of the glass spheres (5) lies in the range from 70 to 110 µm.
8. Structural panel, in particular flooring panel, having a core (1) made of wood material or wood material-plastic mixture, a decoration (7) printed onto a top side of the core, an outer layer (8) covering the decoration (7) and comprising a melamine resin base, and a wear-resistant layer (4) which is applied to the outer layer (8) and has abrasive particles (6), characterized in that the outer layer (8) is cellulose-free and has glass spheres (5), and the wear-resistant layer (4) consists of a melamine resin-corundum-cellulose fibre mixture.
9. Structural panel according to Claim 8, characterized in that the glass spheres (5) are silanized.
10. Structural panel according to Claim 8, characterized in that the diameter of the glass spheres (5) lies in the range from 60 to 100 µm.

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