Bright colored surface layer

Technical field

The disclosure generally relates to fibreboard based panels with wear resistant surface layers for building panels, preferably floor panels. The disclosure relates to building panels with such a wear-resistant surface and methods of producing such panels.

The scope of application

The disclosure is particularly suitable for use in floating floors that are formed of floor panels with a fiberboard core and a decorative abrasion resistant surface. Therefore, the following description of the technique, problems of known systems, and the object and features of the invention will, as a non-limiting example, be directed primarily to this field of application, and in particular to floors that are similar to traditional floating laminate floors based on fiberboard. Disclosure does not exclude floors that are glued to the floor substrate.

It should be emphasized that the embodiments of the disclosure can be used as a panel or as a surface layer that is, for example, glued to the core. Embodiments of the disclosure can also be used in applications such as, for example, wall panels, ceilings, furniture elements and the like. Embodiments can also be used in floors with optional surface materials such as cork or wood to improve wear and design.

Background of the invention

The production of laminated building panels with a surface comprising laminated paper sheets is well known.

A new panel type called "Fiberboard Floor" (WFF) was disclosed in WO 2009/065769, which shows both products and methods of making such products. Pressed, directly laminated building panels usually contain a 612 mm fibreboard core, an upper laminate decorative surface layer

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0.2 mm and a bottom balancing layer of laminate 0.1-0.2 mm thick, plastic, paper or similar material.

The laminated surface generally contains two sheets of paper - printed decorative paper 0.1 mm thick and transparent cover paper thickness 0.05-0.1 mm applied on decorative paper and designed to protect the decorative paper from abrasion. The print on decorative opaque paper is only about 0.01 mm thick. The transparent cover layer, made of refined cellulose fibers, contains small and transparent particles of aluminum oxide. The refined fibers are rather long, about 210 5 mm, and give the casing paper the required strength. In order to achieve transparency, all natural resins that are present in the virgin fiberboard have been removed and aluminum oxide particles have been used as a very thin layer on decorative paper. The surface layer of the laminate floor is characterized in that the decorative and anti-wear properties are generally obtained by means of two separate layers superimposed on each other.

Printed decorative paper and cover layer are impregnated with melamine resin, and laminated to the core of fiberboard hot and under pressure.

Small particles of aluminum oxide can have dimensions ranging from 20 to

100 microns. Particles can be incorporated into the surface layer in a number of ways. For example, they may be attached to the pulp during the manufacture of casing paper. They can also be sprayed onto the wet lacquer during the impregnation of the cover layer if a varnish is used to impregnate the cover layer.

An anti-wear layer can also be produced without a cellulosic cover layer. In this case, melamine resin and aluminum oxide particles are used as the varnished layer directly on the decor paper using similar methods as those described above. This anti-wear layer is generally called a fluid cover.

Thanks to this method of production, a surface with high wear resistance can be obtained and this type of surface is mainly used on laminate floors, but it can also be used in furniture elements and similar applications. High-quality laminate flooring is resistant

EP2 523 804 wear resistance of 4000-6000 revolutions, which corresponds to the abrasion class AC4 and AC5 measured with the Taber abrasion test device, in accordance with the ISO standard.

It is also known that the wear resistance of a varnished wooden surface can be significantly improved by adding aluminum oxide particles to the transparent varnish layer covering the wood surface.

The most common core material used in laminate flooring is fiberboard with high density and good stability, usually called HDF (High Density Fibreboard). Sometimes MDF (Medium Density Fibreboard) is also used as the core. Other core materials, such as chipboard, are also used.

WFF floor panels are "paper free" with a surface layer containing a substantially homogeneous mixture of wood fibers, binders and wear-resistant particles. The wear-resistant particles are preferably aluminum oxide particles and the binders are preferably thermosetting resins such as melamine. Wear-resistant particles are found over the entire thickness of the surface layer, from top to bottom, and contact the panel core. Other suitable materials are, for example, silicon dioxide or silicon carbide. In general, all these materials are preferably applied in dry form as a mixed powder to the HDF core and cured hot and under pressure to obtain a surface layer of 0.2-1.0 mm thick.

Document US 4,430,375 discloses a method of impregnating unimpregnated paper by means of a coating composed of abrasion resistant particles and microcrystalline cellulose particles dispersed in a stable aqueous suspension. The resulting coated abrasion resistant paper is then impregnated with melamine or polyester resin and dried in a conventional manner.

Application US 2009/0155612 discloses a building panel and a method for producing a building panel of the type described above with reference to WFF (Wood Fiber Floor). A building panel, such as a floor panel, contains a mixture of unrefined wood fibers containing natural resins such as lignin, binder and wear-resistant particles.

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Definition of certain terms

In the text below, the visible surface of the installed floor panel is called the "front side", while the opposite side of the floor panel in contact with the floor surface is called the "back side". Sheet material, which is the main part of the panel and provides the panel with the required stability, is called the "core". When the core is covered by a surface layer closest to the front side and preferably also a balance layer closest to the back side, it forms an intermediate called "floor plate" or "floor element" when the intermediate product is divided into multiple floor elements in the subsequent operation. When floor elements are machined along their edges to obtain the final shape with the joining system, they are called "floor panels". By "surface layer" is meant all layers that give the panel decorative properties and wear resistance, and which are applied to the core closest to the front side coating, preferably the entire front side of the floorboard. As "decorative surface layer" is meant a layer which is mainly intended to give the floor a decorative appearance. "Wear layer" means a layer which is mainly adapted to improve the durability of the front side.

As "horizontal plane" is meant a plane extending parallel to the part of the outer surface layer. The term 'horizontal' means parallel to the horizontal, whereas 'vertical' means perpendicular to the horizontal. "Up" means movement towards the front side, while "down" movement towards the rear side.

Brief description of the invention

The general purpose of the embodiments of the disclosure is to provide a building panel, preferably a floor panel, with a light and / or simple abrasion resistant layer, e.g. light white, which can be produced more economically than with currently known technologies.

The method described in WO 2009/065769 includes the use of virgin or recycled wood fibers limited in that when pigments are used to obtain light colors, e.g. light white or very intense colors, the natural color of virgin or

EP2 523 804 recycled wood fibers will give a less bright or less colorful result, due to the natural resins found in the fibers. Natural resins make it difficult to obtain a natural color and can cause discoloration. The problem of organic color can be solved by increasing the amount of pigments, but this is a rather expensive solution and large amounts of pigment can cause other problems, such as pigment stains.

Conventional laminate floor panels are limited in light or intensely colored surfaces due to the limited transparency of highly wear-resistant layers.

The solution to the problem is the use of a dry powder layer containing a mixture of purified binder for fibers, pigment and abrasion resistant particles.

An aspect of the invention is a method of producing a light-colored, wear-resistant surface layer comprising the steps of:

· Applying a layer of dry powder containing a mixture of refined fibers, binder, pigment and wear-resistant particles to the carrier; and • curing the mixture into a colored or light white wear-resistant layer by applying heat and pressure to the mixture.

The binder is preferably melamine resin, and wear resistant particles are aluminum oxide. The pigments for obtaining light white products are preferably titanium dioxide, lead oxide or other commonly used pigments. Pigments for making very colorful products come from a wide range of inorganic and organic products.

The carrier onto which the mixture is applied is preferably an HDF panel, and the resulting panel thus has wear-resistant particles over the entire thickness of the surface layer from top to bottom and in contact with the panel core.

Refined fibers are fibers that are mostly free of natural gums typically found in wood fibers or other natural fibers. Such fibers can be obtained by rinsing, extraction, bleaching or a combination of these. An example of such a fiber is Technocel®

150 TAB, which can be provided by CFF (Germany).

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In a preferred embodiment, the amount of resin compared to the amount in refined fibers, e.g. white fibers, in the dry powder layer is greater than 100%, preferably above 120% and most preferably in the range from 120% to 180%. Such coefficients result in increased processing capacity and improved resistance to stains.

The sublayer, the layer dispersed on the substrate, in combination with the dry powder layer above the sublayer, gives even better processability, such as embossing depth and higher gloss. In embodiments, the sublayer contains wood fibers, preferably natural wood fibers or HDF fibers, however refined fibers and resin can be used. In a preferred embodiment, the amount of resin compared to the amount of wood fibers is less than about 100%, preferably below about 200%, more preferably below about 300% and possibly even below about 400%.

The upper layer of refined fibers, without any aluminum oxide, placed above the dry powder layer further improves the resistance to stains. It also extends the life of the press plates.

Embodiments of the disclosure include the following combinations of layers: (1) a sublayer and a dry powder layer; (2) a dry powder layer and an upper layer; and (3) sublayers, dry powder layer and top layer.

It is also possible to use a mixture of refined fibers and HDF fibers or any natural fibers, i.e., wood fibers that are not refined, to reduce the cost and / or obtain other colors.

You can convert many combinations of ingredients into fully functional products. Two examples are given to show two functional prototypes of innovation.

Short description of the figures

The disclosure can be described as follows, in combination with preferred embodiments and in more detail with reference to the accompanying exemplary drawings, where

Fig. 1 shows a floor panel according to an embodiment of the disclosure.

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A detailed description of the embodiments

Panel 1 is equipped with a wood fiber-based core 6, a homogeneous opaque decorative surface layer 5 and preferably a balancing layer. Panel 1 is, in one embodiment, integrally formed in a production process in which the surface layer, core and balancing layer are formed in the same pressing operation.

Fig. 1 shows the surface layer 5. It comprises a mixture of refined fibers 14, small wear-resistant particles 12, 12 'and binder 19. The wear-resistant particles (12, 12') are preferably aluminum oxide particles.

The surface layer also contains colored pigments and / or, optionally, other decorative materials or chemicals. Decorative material includes, for example, materials that can affect the design aspect (s) of the surface layer. Exemplary design materials include materials that affect texture, reflectivity, gloss, luminescence, transparency, etc.

Embodiments of the disclosure offer the advantage that the wear-resistant surface layer can be made much thinner than in known laminate floor panels.

A preferred binder is melamine or urea formaldehyde resin. All other binders, preferably synthetic thermosetting resins, can be used.

In the method according to embodiments of the invention, the same spreading and pressure units as disclosed in WO 2009/065769 are preferably used, preferably in a method with a structured press plate.

Example W1: Light white formula

On the 9.8 mm thick HDF board, two NKR 140 backing papers were attached on the back side for balance, a WFF powder mix consisting of 40 wt. refined fibers, 10% by weight titanium dioxide as a pigment and 40 wt. melamine resin.

The WFF powder mixture was applied using a so-called scattering machine that evenly distributes the WFF powder on the HDF surface. The total amount of WFF powder was 625 g / m2². The WFF powder was attached to the HDF board by spraying on the WFF powder an aqueous solution consisting of 97 wt. demineralized water, 1 wt. BYK-345 (wetting agent 8

EP2 523 804 added to reduce surface tension) and 2 wt. Pat 622 / E (release agent).

The above material was placed in the so-called DPL press. The surface texture consists of a special press plate with mountains and valleys with a height difference between the highest and lowest parts of about 300 microns. This deep-drawing plate cannot be used during DPL and HPL pressing, melamine impregnated papers crack during pressing. The resulting product is a light white building panel.

Further examples of powder mixtures are listed below.

<td>Type</td><td>W1</td><td>W2</td><td>W3</td><td>W4</td><td>sublayer</td><td>W5</td>

<td>HDF fiber, wt.%</td><td> 0</td><td> 0</td><td> 0</td><td> 0</td><td> 75</td><td> 0</td>

<td>White fiber, wt.%</td><td> 40</td><td> 40</td><td> 35</td><td> 30</td><td> 0</td><td> 39</td>

<td>Prefere 4865, wt%</td><td> 0</td><td> 40</td><td> 45</td><td> 52</td><td> 25</td><td> 0</td>

<td>Kauramine 773, wt.</td><td> 40</td><td> 0</td><td> 0</td><td> 0</td><td> 0</td><td> 50</td>

<td>TiO2, wt.</td><td> 10</td><td> 10</td><td> 10</td><td> 9</td><td> 0</td><td> 11</td>

<td>A12O3, wt.</td><td> 10</td><td> 10</td><td> 10</td><td> 9</td><td> 0</td><td> 0</td>

<td>Total wt.</td><td> 100</td><td> 100</td><td> 100</td><td> 100</td><td> 100</td><td> 100</td>

Prefere 4865 and Kauramine 773 are used in the above mixtures, which are examples of formaldehyde melamine resins.

For W3 and W4, the ratio of resins is increased compared to white fibers (refined fibers). The increased ratio increases the processing capacity and the resistance to stains is improved. In a preferred embodiment, the proportion of resin compared to white fibers is greater than about 100%, preferably above about 120% and most preferably in the range of from about

120% to around 180%.

The sublayer, the layer dispersed over the core, in combination with any of the W1-W4 layers above the sublayer gives even better processability, such as embossing depth and higher gloss.

An upper layer, such as W5, without any aluminum oxide, placed above any of the W1-W4 layers further improves the resistance to leaks. It also extends the life of the press plates.

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Example R2: A red formula

On a 9.8 mm thick HDF board, on the back side for balance, two NKR 140 underlay papers were attached, a WFF powder mix consisting of 42.5 wt. refined fibers, 10% by weight aluminum oxide, 5 wt. Heucosin Spez. Tomatenrot G 10138 as a pigment and 42.5 wt. melamine resin. The WFF powder mixture was applied using a so-called scattering machine that evenly distributes the WFF powder on the HDF surface. The total amount of WFF powder was 625 g / m2². The WFF powder was attached to the HDF board by spraying on the WFF powder an aqueous solution consisting of 97 wt. demineralized water, 1 wt. BYK-345 (wetting agent added to reduce surface tension) and 2 wt. Pat 622 / E (release agent).

The above material was placed in the so-called DPL press. The surface texture consists of a special press plate with mountains and valleys with a height difference between the highest and lowest parts of about 300 microns. This deep-drawing plate cannot be used during DPL and HPL pressing, melamine impregnated papers crack during pressing. The resulting product is a colorful simple red building panel that cannot be easily obtained without refined fibers.

The aqueous solution sprayed onto the WFF powder may contain, for example, 80-100 wt. water, preferably demineralized water, 0-10 wt. wetting agent and 0-10 wt. releasing factor. More preferably, the aqueous solution may contain, for example, 95-98.5 wt. water, preferably about 97% by weight, 0.5-2% by weight wetting agent, preferably about 1 wt. and 125 wt. release agent, preferably about 2 wt.

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