EP1681103B1 - Wooden material with conductive surface - Google Patents

Abstract

A panel (A) of wooden material (WM), having a surface coating comprising an undercoat (applied to WM) and at least one lacquer layer (LL) hardened by UV-light or an electron beam (the overall thickness of the LL('s) being less than 120 mu m), includes at least one functional component (I), integrated in LL('s) or in the form of a functional layer which is external, under LL('s) or between at least two LL's. Independent claims are included for: (1) a panel (A') of WM, having a coating of lacquer on at least part of the side opposite to the surface coated; (2) a method for coating WM by applying at least two layers of UV-hardenable lacquer, where the first layer is subjected to UV treatment to start hardening of the lacquer, the second layer(s) is/are applied before the first layer has hardened completely and complete hardening of the second layer(s) using UV light is commenced after applying the last layer; and (3) apparatus for coating (specifically lacquering) panels, in which the panels are transported to and from a processing unit, the coating is applied and the coating is partially or completely hardened, where (a) application and hardening devices arranged in direct succession are combined to a give a processing unit, (b) at least two such processing units are provided and (c) a processing unit for applying functional layer(s) is provided before, between or after processing units for applying at least two LL's.

Description

The invention relates to a plate-shaped wood material and an overlay, which are each coated with a synthetic resin.

Wood-based materials coated with synthetic resins are widely used in practice, for example as floors, wall or ceiling coverings, countertops, work surfaces and the like. Overlays coated with synthetic resins, which are suitable for application to wood-based materials, are a common precursor in the production of coated wood-based materials. Due to the resistant surfaces resulting from the coating of the wood-based materials directly or through the application of resin-impregnated overlays, these wood-based materials used both in the living area (kitchens, offices, floors) and used for commercial purposes. In the context of this invention, all products made of wood or a mixture of wood and plastic are referred to as wood-based materials. Particularly typical wood-based materials are different types of fiberboard or chipboard.

In this case, some resin-coated wood materials are subject to only a serious limitation, the static charge resulting from acting as an insulator resin surface. In practice, this is particularly disadvantageous in melamine resin-coated surfaces. In private use, this merely means an undesirable or unpleasant characteristic, in commercial use the risk of static charge can be an exclusion criterion for various uses, especially in environments where a spark due to the risk of explosion is to be avoided.

So far, three different strategies are pursued to reduce the static charge of resin surfaces: First, conductive substances, such. As soot, mixed into the resin that is applied to the surface of wood materials or on overlays. Apart from the difficult processability and the Pollution problems, especially in the processing of z. As soot, which has limited essentially to "black" color scheme of the surface practical use in the market.

Black, gray or semi-transparent, conductive paints are used in the US 6,296,939 described, but only as a carrier layer for depositing powder coating particles, which are then melted and cured to a lacquer layer. Fully transparent conductive paints are not described.

Alternatively, so-called antistatic agents, mostly surfactants, are mixed into the synthetic resins or applied to their surface. Examples of this mechanism of action are z. B. in the DE 20318 290 (Kaindl ) or the WO 2004/050359 (Unilin). These surfactants extract water from the ambient air. The forming in the vicinity of the surfactants, thin molecular water film is sufficient to ensure a minimum charge balance. However, this intrinsically simple and convincing active principle has in practice two decisive disadvantages: The water film forming around the surfactants only causes a reduction of the surface resistivity by about one order of magnitude, ie to about 1 × 10 ¹⁰ Ω to 1 × 10 ¹¹ Ω , Thus, the measured values, z. B. to EN 14 041 are required to classify surfaces as conductive, not achievable. Another disadvantage is that the ambient air must have sufficient moisture to form a film of water. However, the problem of static charge is just at low humidity. Antistatic agents do not work exactly when they are needed.

Finally, in the DE 103 01 293 (Blomberger ) proposed to embed conductive fabrics in strip form in a synthetic resin layer on the surface of plate-shaped wood materials. However, the optical degradation of the surface severely limits the usefulness of these conductive fabrics.

There is therefore a need to prepare a plate-shaped wood material or an overlay with at least one synthetic resin layer in such a way that a significant long-term Improvement of the conductivity is given.

This object is achieved with a plate-shaped wood material according to claim 1 and an overlay according to claim 8.

The core of the invention is the incorporation of electrically conductive, transparent particles in synthetic resin, preferably in transparent synthetic resin. This mixed with transparent, electrically conductive particles resin is then either on an overlay applied or on the surface of a plate-shaped wood material. According to the invention, it has been found that a single layer of synthetic resin mixed with small amounts of said particles is sufficient to ensure a significant improvement in the dissipation capacity permanently and independently of other parameters such as ambient humidity, for example a surface for a dissipative floor according to DIN IEC 61 340 to create.

Transparent conductive particles are produced, for example, by applying metal oxides to carrier particles. For example, a mica particle doped with tin and antimony oxide is suitable. Transparent particles may have a platy or spherical shape. Good conductivity and transparency as well as optimum conductivity is achieved with particles having a diameter of up to 25 .mu.m, preferably up to 15 .mu.m, preferably of up to 10 microns.

It was surprising for a person skilled in the art to permanently achieve a desired dissipation capability with a very thin layer structure without sacrificing high mechanical and chemical resistance of the synthetic resin layer offset according to the invention with electrically conductive, transparent particles.

According to the invention, it is sufficient if the electrically conductive, transparent particles are contained in only one layer of a multilayer synthetic resin structure on an overlay or a plate-shaped wooden material. According to the invention, up to 15% by weight (% by weight) of electrically conductive, transparent particles are based on the solids content of the synthetic resin, preferably up to 10% by weight, more preferably up to 8% by weight of particles based on the Solid portion of the resin used.

A dissipative surface on an overlay or a plate-shaped wood material is built up if at least one layer, that is to say up to 40 g / m ^{2 of} a synthetic resin mixed with transparent, conductive particles according to the invention, is applied. According to a preferred embodiment, up to 25 g / m ² , more preferably up to 15 g / m ² , advantageously up to 10 g / m ² are sufficient. Overall, the layer structure of the respective surface can easily exceed 100 g / m ² in the case of a multilayer structure. Nevertheless, only one layer of the invention with particles is sufficient offset resin to obtain a surface having a significantly improved Ableitfähigkeit.

According to an advantageous embodiment, in the synthetic resin of the invention mixed with electrically conductive, transparent particles, a layer thickness on the wood-based panel of up to 40 μm, preferably up to 20 μm, particularly preferably up to 10 μm, suffices in the walk test according to EN 1815 To achieve classification as a static surface in accordance with EN 14041, which ensures a charge of less than 2 kV. This value is achieved with the inventively applied to an overlay or a plate-shaped wood material, provided with particles of synthetic resin layer. It should be particularly pointed out that this is achieved largely independently of the ambient humidity, that is also at values of, for example, 25% relative humidity. For the first time, a reduction of the surface resistance to values of 2 × 10 ⁰⁸ Ω was achieved with the overlay according to the invention when using melamine resin which has been mixed with transparent, electrically conductive particles.

The electrically conductive, transparent particle is firmly anchored in the synthetic resin. It may therefore be contained in the outermost layer of a multi-layered surface. Surprisingly, however, the desired dissipation ability is also achieved if the layer containing the mentioned particle is used in a multi-layered surface structure, e.g. is covered by other resin layers.

According to an advantageous embodiment of the invention, a transparent synthetic resin is used, in particular a melamine resin. As a result, an expansion of the fields of application of the inventively coated overlays or plate-shaped wood-based materials is achieved, so that these e.g. also suitable for work surfaces in the electronic industry. Panels are also often used for the design of wall surfaces, so floors, ceilings or walls. Here, the coating according to the invention proves to be advantageous, since the conductive surface is also suitable for at least partial shielding of electromagnetic fields. It thus helps to avoid interference from electrosmog.

In the context of the invention, the term "overlay" is understood to mean that a carrier made of paper or a synthetic fiber scrim is coated at least with a synthetic resin layer having transparent, electrically conductive particles. Overlays are usually used for coating board-shaped wooden materials. Alternatively, wood-based materials are renounced by an overlay immediately provided with a layered surface structure. The at least single-layer surface coating of the overlay according to the invention has at least one synthetic resin into which the electrically conductive, transparent particles are mixed. Optionally, the synthetic resin may also contain fibers to form a so-called "liquid overlay". That is, when using a "liquid overlay" can be dispensed with the use of the usual paper-based overlay. The liquid overlay is applied directly in liquid form to the surface of a wood material.

Both in the production of overlays as well as in the construction of surface coatings on plate-shaped wood materials usually several synthetic resin layers are applied one above the other. On the one hand, this simplifies the uniform curing of synthetic resins, on the other hand, the layers often have a different structure. For example, one of the synthetic resin layers is often mixed with corundum in order to increase the wear resistance of the surface. Typically, this happens with floor surfaces.

The multi-layered surface of plate-shaped wooden materials often also has a layer of coloring constituents, which is covered by transparent synthetic resin layers. Especially in the case of this surface structure, it becomes clear that the transparency of the electrically conductive particles abolishes restrictions on the use of the plate-shaped wood-based materials which hitherto existed.

Fig.1:

Schematische Darstellung eines plattenförmigen Holzwerkstoffs mit leitfähiger Oberflächenbeschichtung

Details of the invention will be explained in more detail with reference to the following embodiments.

Fig.1:

Schematic representation of a plate-shaped wood material with a conductive surface coating

example 1

An overlay with a basis weight of 40 g is used by rollers by itself Known impregnation with Quetschwalzendosierung out. In a bath, through which the overlay is pulled, melamine resin with a solids content of 60% is introduced into the paper. After leaving the bath, the overlay is passed through a pair of rollers on which excess synthetic resin is stripped off. The paper thus impregnated has a weight of 100 g / m ² after intermediate drying.

Subsequently, in each case an additional melamine resin layer of 20 g / m ^{2 is} applied to the top and bottom of the paper in a raster application work. The top side applied melamine resin layer is associated with-related to the solids content of the melamine resin 8 wt .-% transparent, electrically conductive particles, namely with mica particles, which are doped with tin and antimony, and a diameter of approx 15 μm. The overlay is dried after application of the second melamine resin layer.

The overlay is pressed on a high-density fiberboard on which decorative paper is already applied, under pressure and heat. The resulting surface of the fiberboard has a surface resistivity of 3.0 x 10 ⁰⁸ Ω when tested for electrostatic behavior according to IEC 60093 and EN 1081. If such a coated fiberboard is used as floor, it is classified as "Ableitfähiger Fußboden" according to DIN IEC 61340 -4-1: 1997 or as "electrostatic dissipative floor covering" according to EU 14041: 2004 -12-20. This classification was previously unattainable when using melamine resins for surface coating of floors.

The test according to EN 1815 results in a so-called person voltage of 1.8 kV on an insulating pad for a person in rubber soles. Thus, the coated with the above overlay fiberboard is classified as a conductive floor, because the personal voltage of 2 kV is well below.

Example 2

On a medium density fiberboard 2 is -as in Fig. 1 shown after smoothing the surface by means of paint a decor 4 applied. On the decor 4 more surface layers are applied, namely a first layer 6 of a UV-curing paint with a layer thickness of 20 microns, which-based on the solids content of the Melaminharzes- with 8 wt .-% of the above, transparent, electrically conductive particles 10 is provided. After at least partial curing of this lacquer, a further layer 12 of a UV-curing lacquer with a layer thickness of 20 microns is applied and the lacquer layers are finally cured. The thus surface-coated hardboard 2 is provided with an edge profiling 14 a, b. It is used as a ceiling or wall panel. Fig. 1 shows the individual layers of the surface structure for the sake of clarity not to scale.

This panel has a surface resistance of about 10 ⁰⁸ Ω to 10 ⁰⁹ Ω. It shields electromagnetic fields at least partially. If these panels z. B. laid as wallcovering in rooms that are exposed to electromagnetic fields, so these fields behind the panels, so in the rooms, only weakened or no longer perceived.

Example 3

A decorative paper intended for use on a countertop is made by impregnating a backing paper with a melamine resin decor print. On this impregnated paper is then -as described in Example 1, a melamine resin layer, which-based on the solids content of the melamine resin-10 wt .-% of the particles described in Example 1 is added, and those at 40 g / m ² is applied to the prepregnated paper. The decorative paper with a conductive top surface thus produced is pressed onto a chipboard.

This chipboard is suitable for use as a worktop, in particular in the electronic industry, since the surface resistance of the melamine resin coating thus produced is 10 ⁰⁷ Ω to 10 ⁰⁹ Ω. Sensitive electronic components that are damaged or destroyed by stronger electrical discharges can be stored or processed on these easily and inexpensively manufactured surfaces.

Claims (8)

1. Plate-shaped wooden material (2) with an at least one-layered surface coating, whereby the surface coating has at least one layer with

   - a synthetic resin which is eventually mixed with fibres and which

   - has at least one type electrically conductive transparent particles (10),

   characterized in that the particles content (10) amounts to up to 15 % in weight with respect to the solids content of the implemented synthetic resin with respect to the solid bodies content of the implemented synthetic resin and that the synthetic resin mixed with particles is applied onto the plate-shaped wooden material in a quantity of application up to 40 g/m².
2. Plate-shaped wooden material according to claim 1, characterized in that the synthetic resin mixed with particles (10) is applied onto the plate-shaped wooden material as a layer with a thickness up to 30 µm, preferably up to 20 µm, particularly preferably up to 10 µm.
3. Plate-shaped wooden material according to claim 1, characterized in that a transparent synthetic resin is used.
4. Plate-shaped wooden material according to claim 3, characterized in that melamin resin is used as synthetic resin.
5. Plate-shaped wooden material according to claim 1, characterized in that the surface coating of the wooden material has at least one further layer.
6. Plate-shaped wooden material according to claim 1, characterized in that the surface coating has a further layer which has a synthetic resin into which corundum is mixed.
7. Plate-shaped wooden material according to claim 1, characterized in that the surface coating of the wooden material has at least one further layer which has colouring components.
8. Plate-shaped wooden material according to at least one of the claims 1 to 7, characterized in that the plate-shaped wooden material is configured as a floor panel, a wall panel or a ceiling panel.

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