EP1937476B1 - Abrasion-resistant slabs having a decorative surface - Google Patents

Description

The invention relates to a method for the production of highly abrasion-resistant boards with a decorative surface and highly abrasion-resistant boards with a decorative surface. A decorative surface in the context of the invention is a motive usually generated by pressure, such as the replica of a wood structure. It can also be an original wood structure that forms the decorative surface.

Parquet floors have decorative surfaces that are formed by wood. To make these decorative surfaces more resistant, one or more transparent layers of varnish are applied and cured. If several paint layers are applied, each individual paint layer is first at least partially cured or gelled, before the next paint coat is applied thereto. It is to be prevented by curing or fishing a flow of each individual paint layer.

It is also known to use so-called filled paints. These are paints containing very small ceramic particles. The particle size is regularly in the range of nanometers. These particles are called nanoparticles. It is to be improved in addition to a seal of a surface in addition to the abrasion resistance. However, since the particles are very small, an abrasion resistance of several 1000 revolutions according to EN 13329 can not be achieved for that reason. In addition, after each coating application, a coated layer is at least partially cured or gelled, so that the individual paint layers do not melt. The fishing also has the consequence that can not achieve very high abrasion values. The achievement of abrasion values above 3000 revolutions is not possible.

In addition, there are so-called laminate floor panels in which the decorative surface is formed by printed paper. The decorative paper surface is provided with an abrasion resistant layer in order to use such a panel for floor coverings. Such a state of the art is the WO 2005/042644 refer to.

If the decorative papers are on the surface of a floor covering, the decorative paper to be produced, together with the abrasion-resistant layer applied thereto, must fulfill a particularly wide variety of properties. This includes that a sufficiently high abrasion resistance must be achieved in order to be offered as a floor covering. In order to be qualitatively competitive, the abrasion values in the area of the floor must be several thousand revolutions. Virtually unsaleable are laminate floor coverings that only meet the requirements of classes AC1 and AC2 according to EN 13329 and thus only have a value IP of 1,800 revolutions. For example, reference is made to recent sales figures of Kronospan GmbH from Lampertswalde. 35% percent of their sold laminate floor production falls into class AC3, which corresponds to an abrasion value IP of at least 2500 revolutions. 60% of the production falls into class AC4, which corresponds to an abrasion value IP of at least 4000 revolutions. 5% of the production falls into class AC5, which corresponds to an abrasion value IP of at least 6500 revolutions.

Abriebwerten IP of at least 2500 is understood in the understanding of the expert to a flooring that can be sold in the floor area in Europe.

In addition to abrasion resistance, other properties such as impact resistance and chemical resistance also play a role. For example, spilling a glass of red wine must not result in a red wine stain remaining in the topping.

In practice, to achieve the above objectives in the field of laminate flooring, the so-called wet-in-wet process with amino resins had prevailed (which inter alia the EP 0 875 399 A2 , Page 3, line 44), in which the decorative paper is first impregnated with an amino resin. On the still wet, impregnated decorative paper, a dispersion based on an amino resin is applied, which contains as abrasion-resistant or abrasive particles mainly (light) corundum or in the case of dark decors (dark) silicon carbide, such as EP 1 270 811 A1 can be seen. The paper is not just about providing a decor. It also fixes the applied wet amino resins. This effect is therefore comparable to the fixation that is to be achieved by the Angelieren in paints.

The wet-on-wet application ensures that no unwanted boundary layers are formed. In this case, an amino resin u. a. therefore used, because this eventually forms with its subsequent curing a so-called matrix or a so-called network. Individual layers formed from amino resin do not merely adhere to one another mechanically. Rather, the layers formed from amino resin are interconnected via double bonds. The then present matrix or the network ensures that there is a solid bond. This is regularly a first important prerequisite in order to achieve high abrasion values.

The abrasion-resistant particles are applied in the wet-in-wet process by means of a dispersion, because it ensures that no optically disturbing interfaces between the abrasion-resistant particles form and also a very stable integration of the abrasion-resistant particles in the resin matrix can be achieved.

Although there have been attempts to sprinkle abrasion-resistant particles, for example, so do not apply with the help of a dispersion. However, it is often very difficult to achieve the required uniform distribution because the particles tended to form clusters (see WHERE 98/47705 , Page 3, paragraphs 1 and 4). Also, it is difficult to embed the abrasion-resistant particles sufficiently well in the resin.

Thus, up to the time of the present application, wet-on-wet resin application is the process almost exclusively used in the practice of making a laminate panel with highly abrasion-resistant decorative paper for a floor covering, although its manufacture and handling a dispersion with therein abrasion-resistant or abrasive particles is relatively expensive in terms of apparatus. Only occasionally in practice a procedure - as from the WO 2005/042644 known - carried out, are sprinkled in the abrasion-resistant particles on a decorative paper.

In order to provide a good quality flooring, so the abrasion-resistant particles must be evenly distributed on a decor. Otherwise the abrasion values will fluctuate and there will be some clouding (see also EP 0 875 399 A2 , Page 3, lines 24 - 27). If a wet application is made, the uniform application generally requires that the abrasion-resistant particles in the amino resin dispersion are already uniformly distributed and remain. This is problematic because the particles sink rapidly and so segregation occurs. To this circumstance, inter alia, the publications EP 0 875 399 A2 , Page 3, lines 24 - 30; WO 98/47705 , Page 2, paragraph 2; DE 197 10 619 , Page 2, lines 18 - 22; EP 0 875 399 A20 , Page 2, lines 20 - 22; EP 0 875 399 A23 , Column 2, lines 48-58.

Thus, at the time of the application, the skilled person skilled in the art of developing abrasion resistant floor materials was confronted with the widespread knowledge that although wet-on-wet application is practically indispensable in the case of decorative papers for floor coverings, the problem is the homogeneity of the abrasion resistant Represents particles in the A-mini resin dispersion.

The prior art has various suggestions as to how this problem could be solved. It is regularly emphasized that the abrasive material should be particularly fine-grained in the case of wet application ( EP 0 875 399 A2 , Claim 6; DE 196 43 742 A1 , Paragraph 2 of the abstract "fine-grained material"; WO 98/47705 , Page 2, paragraph 2; DE 2 362 645 , Page 4, paragraph 1; WO 93/17182 , Page 8, lines 18-19; EP 0 875 399 A23 , Column 6, lines 24-25).

The diameter of the abrasion-resistant particles must not be too small, otherwise high abrasion levels will not be achieved. Also, then the amount of abrasion-resistant particles must be so large that thereby the appearance is undesirable affected. Abrasion-resistant particles with a diameter of a few microns are hardly suitable to reach a surface with high abrasion values.

If a decorative paper has been impregnated with an abrasion-resistant layer, this is placed on a plate. Above the decorative paper, an overlay is placed: Under the plate, a so-called Gegenzugpapier brought. The layer system is pressed in a press while supplying heat. From the plate panels of desired size are sawn out and provided by milling laterally with connecting elements such as tongue and groove.

The overlay is required to protect a press from the abrasion-resistant particles. The abrasion-resistant particles must not protrude from the layers during pressing, otherwise the press would be damaged. Also in the finished laminate panel, the abrasion-resistant particles should not protrude, otherwise an undesirable rough surface remains and the optics is undesirable. For this reason, among other things, abrasion-resistant particles should not exceed a certain diameter. So in the publication WO 2005/042644 called an upper diameter of 200 microns, but can only be realized with the use of relatively thick paper actually.

From a rough surface formed by protruding abrasion-resistant particles, surfaces should be distinguished from coverings which have been embossed. For this purpose, for example, the steel strip of a press on an embossing pattern, as the EP 0 546 402 A2 can be seen. Such an embossing is provided primarily for decorative reasons. Thus, pores of wood are typically replicated by the embossing.

The object of the invention is to provide a plate with a decorative surface and high abrasion in a cost effective manner.

To solve the problem, a varnish is applied to a plate with a decorative surface. Abrasion-resistant particles are placed on the decorative surface plate. Another lacquer layer is applied and the applied lacquers are cured. There is then a plate before, which has an abrasion-resistant surface. The decor of a slab can be formed by solid wood. To make this visible, transparent paints are used.

In contrast to the prior art, after the application of a first lacquer layer, it is not at least partially cured or gelled in order to fix this lacquer in this way. Also, no paper is used to effect fixation of a first applied liquid. The invention thus overcomes the widespread opinion of the skilled person that either first a first liquid layer has to be fixed by partially curing or setting, or another means such as the use of a paper has to be used in order to achieve the fixation. It succeeds so the application of several paints with therein abrasion-resistant particles, which can then be relatively large. Overall, an abrasion-resistant surface with abrasion values of more than 3000 revolutions can be achieved be without the addition of a manufacturing cost increasing paper must be used.

In one embodiment of the invention, a decor has been printed on a plate and preferably by indirect gravure printing. Compared to the laminate floor with the decorative paper, the decor paper is first eliminated. In addition, no Gegenzugpapier is then required, which should counteract in the prior art distortion of the plate. This saves a next paper, including the resin, for bonding the countertraction paper to the plate. Also, an overlay with the associated amount of resin is saved. The meaningfully used amount of paint thus depends only on the particle size. For reasons of cost and handling, the amount of paint is expediently limited so that the particles do not protrude from the paint. It minimizes the amount of paint that should at least be used.

Indirect gravure printing is particularly suitable for properly printing a décor on a HDF or MDF board, for example. Thickness tolerances can namely be compensated by the elastic rollers used in indirect gravure printing. The lacquers used are then also transparent, so that the decor can be seen.

The average diameter of the abrasive particles in one embodiment of the invention is 10 to 160 μm in order to achieve high abrasion levels expected in the field of flooring by European consumers. Preferably, the average diameter is 20 to 40 microns. The diameter of the existing abrasion-resistant particles are then predominantly within the range of the average diameter, that is, for example, between 20 and 40 microns.

On the one hand, abrasion values can be achieved well above 2500 revolutions. Abrasion values are easily more than 3000 revolutions according to the aforementioned relevant standard possible. On the other hand, this ensures that there is no undesirably rough surface due to a large number of protruding abrasion-resistant particles. Also, the amount of abrasion-resistant particles can be kept sufficiently small so as not to affect the optics too strong.

The said range of 20 to 40 microns is particularly preferable because on the one hand the desired high abrasion levels can be achieved and on the other hand, the appropriate amount of paint can be handled easily.

In one embodiment of the invention, a base coat is first applied to the plate. Subsequently, the abrasion-resistant particles and preferably corundum are sprinkled onto the still wet basecoat. Then a topcoat is applied to the wet base coat with the scattered abrasion resistant particles. Basecoat and topcoat are then cured together. The average diameter of the abrasion-resistant particles is then preferably 10 to 60 microns, more preferably 20 to 40 microns. If a mean diameter of 20 to 40 microns is selected, the diameter of the particles usually do not exceed the value of 60 microns.

Surprisingly, it has been shown that the abrasion-resistant particles penetrate deep enough into the basecoat by sprinkling and thus embedded in the basecoat. This is important in order to obtain high abrasion values and to prevent the abrasion-resistant particles from undesirably protruding from the topcoat layer. It is therefore surprisingly possible to dispense with the handling of a dispersion can.

In one embodiment, however, it is initially possible to prepare a dispersion of basecoat with abrasion-resistant particles located therein. If this is then sprayed on, then the dispersion can be sufficiently moved to keep the abrasion-resistant particles in suspension to keep. However, sprinkling is preferable as it works and no dispersion needs to be handled.

In order to further increase the abrasion values, the abrasion-resistant particles are preferably coated with a silane coupling agent and are sprinkled in this state. The embedding of the abrasion-resistant particles in the paint is further improved.

In one embodiment of the invention UV-curable coatings are used and cured by ultraviolet light, preferably with exclusion of air. If UV-curable lacquers are cured under exclusion of air, the conversion of double bonds during curing is more than 90%. Without air exclusion, on the other hand, a double bond conversion of only 50 to 60% can be achieved. The double bonds form a network that extends from the base coat to the top coat. It will then be achieved particularly high abrasion.

If a lacquer is used which can be cured by UV light, then it preferably has additions of photoinitiators, preferably from 0.3 to 5% by weight. This improves the possibility of being able to crosslink the lacquer used in each case with ultraviolet light.

In one embodiment of the invention are used by electron beam curable coatings, which are cured by electron beam in the absence of air. Even so, a very high conversion of the double bonds by curing succeeds. It forms a network, so that very high abrasion can be achieved.

Particularly easy manages curing or crosslinking under exclusion of air or exclusion of air by the surface of the plate to be hardened, for example, covered during curing by a film that transmits UV and / electron radiation without being destroyed. Polymer-based films meet such requirements. A technically complicated flushing with inert gas during curing can thus be omitted. It is also ensured by using the film further improved that the abrasion-resistant particles are embedded in the paint.

In one embodiment of the invention, the decorative surface of the plate is covered with a pattern-forming film preferably polymer-based during curing. On the one hand, this achieves the desired exclusion of air during hardening. On the other hand, the surface is immediately provided with a structure without pressing a structure under high pressure as in the prior art.

The topcoat preferably has a release agent to be able to easily solve the cover, so for example, the pattern-forming film after curing again.

In a further embodiment of the invention, base coat and top coat differ. The base coat is selected so that it provides a good adhesion to the ground and can compensate for internal tensions. The topcoat is selected so that it is particularly scratch-resistant, mechanically resilient and behaves insensitive to chemical influences. In order to achieve these goals, the topcoat is preferably such that a higher degree of crosslinking can be achieved with this compared to the basecoat. The paints are preferably provided alternatively or additionally with additives that promote the particular desired properties.

In one embodiment of the invention are used as lacquers acrylic lacquers based on polyurethane or aliphatic polyester, which have been found to be suitable. In order to set the desired crosslinkability and viscosity, dimers are added to the paints used in one embodiment. To adjust the viscosity, monomers are added in one embodiment.

If a paint is applied with a roller, the viscosity is preferably 15 to 180 Pa-sec, particularly preferably 60 to 80 Pa-sec, set. If a paint is applied by casting, then a viscosity of preferably 30 to 70 Pa-sec, more preferably from 40 to 60 Pa-sec is set.

Overall, according to the invention, a layer thickness of preferably up to 100 μm is produced above the decoration. This layer comprises the two applied paint layers and the abrasion-resistant particles located therein. This layer, consisting of basecoat and topcoat with the abrasion-resistant particles therein, is preferably at least 80 .mu.m thick so that abrasion-resistant particles having an average diameter of 20 to 40 .mu.m can not reliably protrude from the paint and good structuring of the surface to allow, for example, a replica of wood pores.

It can thus achieve abrasion values of up to 8500 revolutions. This value corresponds to class 34 in the field of floor panels.

In the following we describe the invention by means of a preferred example.

The surface of a HDF board is ground finely. A primer, ie an adhesion promoter, is applied to the ground surface. The wet job is dried. The surface is now filled with an acrylate system with a high solids content and then dried. Then a base color is applied, for example, to provide a light tone. Preferably, the base color is applied by casting over a gap, since then the surface of a plate is provided without contact with the application of paint. The base color is then dried and smoothed, for example with a calender. Subsequently, preferably, the back of the plate is also provided with a paint spread, which forms a barrier against the ingress of moisture. This counteracts a delay.

With a four-color printing unit, a motif is then printed by indirect gravure printing on the dried and smoothed base color. The printed motif is dried.

The basecoat used is Laromer® UP 35 D from BASF, to which is added crosslinking component Laromer® HDDA from BASF for adjusting the crosslinkability and viscosity. Laromer® UP 35 D is used to produce radiation-curable filler and topcoats for wood and wood-based materials. It is a medium-reactive unsaturated polyester resin, about 55% in dipropylene glycol diacrylate. This is supplied as a clear, pale yellow, medium viscosity resin having a viscosity of 3 to 6 Pa-sec. The Dimer Laromer® HDDA is hexanediol diacrylate C ₁₂ H ₁₈ O ₄ :

The base coat is applied in an amount of 20 to 50 g / m ² .

Particles of corundum or aluminum oxide are now sprinkled onto the wet paint. The particles are coated with a silane coupling agent. The average diameter of the particles is between 20 and 40 microns. A diameter of 60 μm is usually not exceeded.

The amount of corundum depends on the desired level of abrasion that is to be achieved. The amount can be up to 50 wt .-% based on the total amount of paint used. Experiments have shown that even a quantity of 25 g / m ² leads to good abrasion values and practically no visual impairment is observed with this amount.

Subsequently, a topcoat is preferably applied to the basecoat with the scattered abrasion-resistant particles. As a base resin for the Topcoat Laromer® LR 8987 BASF has been chosen. It is an acrylate resin for the production of radiation-curable coatings, inter alia for wood and wood-based materials with the composition aliphatic urethane acrylate, 70% in hexanediol diacrylate. The viscosity at 23 ° is 4 to 6 Pa-sec. Paints provided therefrom are characterized by a very low yellowing. In order to cure this lacquer with UV light, a photoinitiator in an amount of 2 to 5 wt .-% is added. The desired viscosity is set by adding Laromer® DPGDA from BASF. These are dipropylene glycol diacrylate C ₁₂ H ₁₈ O ₅ :

The order is preferably carried out in the from FIG. 1 apparent way. Above the HDF plate 1 with the applied base coat 2 including the scattered abrasion-resistant particles 3, a pattern-forming film 4 is placed by rolling from a roll or roller 5 via rollers 6 and 7. Immediately before placing the pattern-forming film 4 adjacent to the intended for laying first roller 6, the topcoat 8 is supplied in such a way that it completes the immediately following curing process airtight to the outside. Above the applied structured sensor film 4 is a device 9 for the curing of basecoat and topcoat by radiation. The structure-forming film 4 is wound up again with a further roller 10. The plate 1 is transported with a conveyor belt 12 parallel to the applied structure sensor film at the same speed in the direction of the arrow 11.

By means of the texturing film, the desired air seal is achieved and a desired surface structure is produced. Next is achieved so that any protruding abrasion-resistant particles are pressed into the paint. Overall, the proper embedding succeeds of abrasion-resistant particles in the paint. The result is a plate with such embedded in a network abrasion-resistant particles that can easily achieve an abrasion value of 4000 revolutions to EN 13329, as of June 2000, and more.

Instead of a pattern-forming film, it is also possible to use a film with a smooth surface if it is merely a matter of achieving a particularly high abrasion resistance of the surface without the presence of a surface structure.

From the plate then floor panels are sawn and laterally provided with connecting means, such as with grooves and springs together with other locking means that allow a glueless connection of panels.

The paints may contain conventional additives such as silicones and polymerizable oils, for example to improve a substrate wetting or to promote a vent or the degree of gloss.

Below a plate produced according to the invention, one or more sound-absorbing layers may be applied. Compared to the prior art, the sound absorption is then particularly well, because there is a smaller number of boundary layers, the sound reflect back disadvantageous. A sound-absorbing layer according to the invention consists for example of thermoplastic material, which preferably has a particularly pronounced relaxation behavior at room temperature. Then the scarf introduced into the layer is particularly strongly absorbed at room temperature. The layer can be very thin and less than 1 mm.

Claims (13)

1. Method for the production of a panel, in particular for the production of a floor panel having a decorative surface and a highly abrasion-resistant layer comprising the steps:

   a) providing a panel (1), that is made of wood or a derived timber product, having a decorative surface,

   b) application of a basecoat (2), that is preferably hardenable by radiation,

   c) depositing of abrasion-resistant particles (3) onto the basecoat,

   d) application of a basecoat (8), that is preferably hardenable by radiation, onto the abrasion-resistant particles (3),

   e) hardening of both applied coats (2, 8), preferably by means of radiation.
2. Method according to the preceding claim, in which the applied coats (2, 8) are covered by a foil (4) and hardened in the covered state, wherein the foil (4) is preferably a texture-giving-foil.
3. Method according to claim or 2, in which the panel consists of wood or a derived timber product and in particular of HDF.
4. Method according to any one of the preceding claims, in which the abrasion-resistant particles (3) consist of corundum and have an averaged diameter of preferably 10 to 60 µm, and particularly preferred of 20 to 40 µm.
5. Method according to any one of the preceding claims, in which the abrasion-resistant particles (3) are coated with a silane bonding agent.
6. Method according to any one of the preceding claims, in which the abrasion-resistant particles (3) are embedded in a cross-linked coat (2, 8), in which the double bonds are preferably converted in more than 90%.
7. Method according to any one of the preceding claims, in which the coat (2, 8) comprises additives of photo-initiators.
8. Method according to any one of the preceding claims, in which the coat (2, 8) comprises a separating agent.
9. Method according to any one of the preceding claims, wherein the basecoat comprises a lower degree of cross-linking in comparison to the top coat located above.
10. Method according to any one of the preceding claims, in which an acrylate coat based on polyurethane and/or based on aliphatic polyester with added dimers or monomers is applied.
11. Method according to any one of the preceding claims, in which the coat layer (2, 8) is applied up to 100 µm in thickness.
12. Method according to any one of the preceding claims, in which the décor will be imprinted on a sanded and primed surface of the panel (1), that is preferably furnished with a bonding agent and/or a basecoat.
13. Floor panel made of a panel according to the method according to one of the claims 1 to 12.

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