FIELD OF THE INVENTION

The present invention relates to laminated boards having improved sound insulation properties for producing floating floors, walls and suspended ceilings having excellent aesthetic characteristics. The boards comprise cork layers for sound insulation.

BACKGROUND OF THE INVENTION

The industry of wood/cork laminates is very large and encompasses many solutions to attend for a growing demand on comfort and sound insulation in combination with more evolved products in terms of aesthetic and technical features.

It is well known that the high competition of this market provides new solutions for technical problems which prevent the fully satisfaction of consumers in terms of quality and cost. Accordingly, the laminated products e. g., floors, has largely evolved, both aesthetically and in terms of sound insulation, but at the cost of complex products and processes, therefore fairly expensive.

Many of the developed flooring products comprise different combinations of several pressed layers from Cork material, wood and composites thereof, usually alternately disposed from each other. Usually, layers from other materials are included to impart floors with such properties as, for example, dimensional stability, better stress sharing and better wear resistance, arranged with a certain order, with more or less variation and having a varied number of layers. At present it is recognized that laminated boards with uneven number of layers are dimensionally more stable, having less propensity for bending. The more used layers of wood based material are HDF (High Density Fiberboard) or MDF (Medium Density Fiberbpard) which impart stiffness and stability to pressed board, in particular with respect to tensile strength or buckling strength, while the cork based layers impart some elasticity and good thermal and sound insulation properties to the board.

The applications DE 3339454, WO 2005100719 Al , WO 03087498 Al and WO 03016655 Al , disclose products having the above mentioned kind of features and others, all being laminated products designed for insulation.

DE 3339454, entitled "Thermal And Impact Sound Insulating Material And Process For The Production Thereof" by POLYBREVETS & GESTION SA, discloses thermal and impact insulation laminated material, made of one thermal insulation inner layer of polyurethane stiff foam and at least one impact insulation outer layer formed from insulation materials such as cork.

WO 2005100719 Al, entitled "Flooring Having Impact Sound Insulation Characteristics and Manufacture Process Thereof", by Amorim Revestimentos, S.A., discloses a flooring having improved sound insulation and impact damping, including decorative, insulation, structural support and stress balance layers, made of wood and cork materials.

WO 03087498 Al , entitled "Floorboards for Floorings", by Valinge Aluminium AB, discloses a um board for laminated flooring having one superficial layer comprising thermosetting resins and including inner layers of MDF or HDF and cork for sound absortion. WO 03016655 Al, entitled "Floor Panel and Method for the Manufacture Thereof, by Unilin Beheer B.V., Besloten Vennootschap, relates to flooring boards made of layers and comprising one hard upper layer forming one decorative surface, and at least one sound absorbing layer comprising at least one structural layer between the sound absorbing layer and the upper layer, at least one support layer at the lower side of the board, wherein the materials include MDF and/or HDF and cork or cork based materials.

While meeting the needs of sound insulation, the above mentioned disclosed products do not solve the prior art problem related with the uneven contact between two joined surfaces of two layers from different materials, or between any materials having corrugated surfaces. This problem occurs, for example, between one cork layer and one thermolaminate layer, wherein such uneven contact causes a roughness transmission from cork layer to thermolaminate layer. This is obviously a drawback when the use of an outer thin coating layer is intended, as said roughness transmission compromises the aesthetic features of the board and therefore the flooring. This issue is restrictive of the type, thickness and number of layers to be used to form said coating or decorative layer.

The boards of the aforementioned applications circumvent the problem by using thick decorative coating layers or otherwise combining several layers to achieve the desired effect. However, in order to use thin outer coating layers, a heed to solve the mentioned problem persists.

Surprisingly, it was found that the arrangement of a board with one thin interface leveling layer, having some characteristics better described herein below, between said layers, for example between a cork layer and a thermolaminate layer, solve the above problem, hence enabling the use of very thin outer coating layers.

Further, it was surprisingly found that despite they have very thin outer coating layers, several boards comprising said leveling layer provided improved sound insulation and impact damping features over prior art flooring. According to the above mentioned, it is a purpose of the present invention to provide a new laminated board which enables to solve the roughness transmission between two layers from different materials, particularly the upper layers, whereby providing simple and aesthetically faultless laminated boards which could be compared in terms of mechanical strength to much more complex and expensive prior art products.

SUMMARY OF THE INVENTION The present invention relates to a laminated board comprising: a core layer (1) of wood based material; at least one intermediate layer (2) of cork based material disposed on one side of the core layer (1), and at least one coating layer (4) disposed on layer (2); and at least one intermediate layer (2') disposed on the other side of the core layer (1) and at least one coating layer (4') disposed on layer (2'); characterized by further comprising, at least one leveling layer (3) between said layers (2) and (4) and at least one leveling layer (3) between said layers (2') and (4'), wherein said leveling layer (3) ensure, on the one hand, a stable connection and, on the other hand, prevent a transmission of roughness between layers (2) and (4) and between layers (2') and (4').

In one aspect of the invention, said coating layer (4) of the laminated board has a thickness less than about 1.5 mm. In another aspect, leveling layer (3) of the laminated board of the invention comprises a resin impregnatable material.

Still in another aspect of the invention, said impregnatable material of the laminated board comprises cellulosic fibers, glass fibers and the like, and combinations thereof.

In another aspect of the invention, the resins of the laminated board are melamine resins, phenolic resins and the like, and combinations thereof. Still in another aspect, said leveling layer (3) of the laminated board of the invention has a gram age of at least 40 g/m ² .

Still in another aspect of the invention, said at least one core layer (1) of the laminated board is made of selected material from the group comprising HDF wood, MDF wood and the like, and combinations thereof.

In a further aspect, said at least one intermediate layer (2) of the laminated board of the invention is made of material selected from the group comprising natural cork, agglomerated cork, cork composites and the like, and combinations thereof.

In a still further aspect of the invention, said coating layers (4, 4') and said intermediate layer (2') of the laminated board are made of material selected from the group comprising cork material, thermolaminate material, melamine paper, wood veneer and the like, and combinations thereof.

Still in another aspect, said layers (1, 2, 4) of the laminated board of the invention comprise respectively a thickness of at least 5 mm, at least 0.7 mm and at least 0.15 mm. The preferred board of the present invention is characterized in that:

• said core layer (1) is HDF wood,

• said at least one coating layer (4) is thermolaminate material,

• said at least one intermediate layer (2') is cork based material,

• said at least one coating layer (4') is thermolaminate material and

• said at least one leveling layer (3) is cellulose material.

Another preferred board of the present invention comprises:

• one core layer (1) of HDF wood,

• one intermediate layer (2) of cork composite,

• one coating layer (4) of thermolaminate material,

• one intermediate layer (2') of cork composite,

• one coating layer (4') of thermolaminate material and

• one leveling layer (3) of melamine resin impregnated paper, respectively between said layers (2, 2') and (4, 4'), wherein said layers (1; 2, 2'; 4, 4') have respectively a thickness of about 7.3 mm, about 0.8 mm and about 0.7 mm.

The present invention also relates to use of the laminated board for producing sound insulation elements and/or for dissipation of impact energy, namely for producing floating floors, walls and suspended ceilings and the like. BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will be apparent from the following description in combination with the accompanying drawings, in which:

Fig. 1 is a schematic view of the cross section of a preferred laminated board according to present invention, showing the arrangement of its different layers.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to laminated boards for producing floating floors, walls and suspended ceilings or the like. For the sake of simplicity during the present description reference will be made only to flooring, although such reference should not be construed as a limitation of the scope of the present invention.

Despite the upper coating layers are very thin, the laminated boards of the invention ensure excellent aesthetic, sound insulation and mechanical strength properties, only comparable with those prior art boards using upper coating layers substantially thicker than upper coating layers of the present invention.

The board of the present invention may be of any shape that can be industrially produced, such as rectangular, square, triangular, circular or others. The laminar arrangement in the boards of the invention provides step-sound insulation and dissipation of impact energy, due to the presence of insulation material.

For the production of flooring having the laminated boards of the invention, these boards must necessarily have fitting elements which enable connection to each other. Such fittings are not part of the invention and any elements available in the market could be used. Also, to practice the invention, the manufacturing process to be used may be any suitable conventional process of the prior art.

The terms "symmetry" or "symmetric" relates to the presence of same number of layers on either side of a core layer, the latter being a reference layer along the description.

The term "roughness transmission" relates to the fact that the connection of two layers from different material result in a perception of roughness from a first layer through a second layer disposed on the first. More specifically, the roughness of said first layer take some physical room belonging to said second layer, therefore causing a visual and/or tactile relief on the second layer impairing the aesthetical quality and the technical characteristics of the latter and hence the entire board.

According to the above mentioned, a laminated board of the present invention is made of several layers from different materials, such as wood, cork, cellulosic fiber and/or glass fiber material, melamine paper, thermolaminate material and the like, and combinations thereof.

The board of the present invention is made of one core layer 1 of wood based material. On one side of the Core layer 1 there are disposed: at least one intermediate layer 2 of cork based material and at least one coating layer 4 and, on the other side, there are disposed: at least one intermediate layer 2' and at least one coating layer 4'. Additionally, at least one leveling layer 3 is disposed between said layers 2 and 4 and between said layers 2' and 4' .

The leveling layer 3 is a layer designed to act as a connection interface and as barrier to said roughness transmission between respectively layers 2, 2' and layers 4, 4'. This leveling layer 3 may comprise any melamine or phenolic resin impregnatable material and the like. The leveling layer 3 has a grammage of at least 40 g/m ² . Said impregnatable material may be selected from the group comprising cellulosic fiber, glass fiber material and the like, and combinations thereof.

The role of said leveling layer 3 acting as interface and barrier layer between layers 2, 2' and between layers 4, 4' is of outmost importance, assuring, on the one hand, a stable connection and, on the other hand, preventing roughness transmission between those layers. This fact enables the use of a very thin coating layer 4 and therefore assures a good deal of aesthetic and technical features and costs. The presence of the leveling layer 3 is the solution that enables the use of one thin coating layer 4, due to its particular composition, which in addition to an excellent mechanical strength may have a variety of aesthetic patterns. These characteristics were not possible in prior art flooring due to said roughness transmission which impaired the aesthetic quality of product and forcing the use of several overlapped layers or otherwise thicker layers in order to circumvent the problem. Regarding the materials and dimensions, the core layer 1 may comprise high density wood fibers based material, entitled HDF, or medium density wood fibers based material, entitled MDF. This core layer 1, due to its mechanical characteristics, namely the mechanical strength, has functions related to the board integrity and support of fitting elements. It should be noted that fitting elements should be integral with the core layer, although any prior art process could be used for providing fittings. Also note that this layer 1 of wood based material may be subjected to special treatments to give additional properties for a better performance of the board. For instance, an anti-moisture treatment can be used to prevent board degradation, as moisture is a main factor of degradation, for example, of the fittings. Other treatments could be used according to need or particular use conditions.

With respect to the at least one intermediate layer 2, which is present on one of the core layer 1 sides, it will serve primarily for insulation purposes and therefore it will be formed with cork based materials, such as natural cork, agglomerated cork, cork composites, etc. having thickness of at least 0.7 mm. This intermediate layer 2 mostly ensures the noise insulation, dissipation of impact energy and damping of noise.

Said at least one intermediate layer 2' disposed on the opposite side (the other side of the core layer 1) to the intermediate layer 2, may, eventually, be used in the same way as layer 2 and/or differently, such as structural stabilizer, stress dissipater, etc. Accordingly, intermediate layer 2' can be made of selected materials from the group comprising cork material, thermolaminate material, melamine paper, wood veneer, and the like, and combinations thereof.

By way of example, a floating floor is made from the boards of the invention, the board layers being symmetrically positioned, wherein the cork composite intermediate layer 2 is on the floor use side (upper side) which mainly serves for impact energy dissipation and reduction of reflected noise. On the opposite (lower side) of the floor, the intermediate layer 2' of cork composite acts essentially in the reduction of transmitted noise.

In relation to said coating layer 4, this is mainly made of a wear coating selected from the group comprising thermolaminate material, melamine paper, cork materials, wood veneer and the like, and combinations thereof. The thickness of coating layer 4 is at least 0.15 mm. Further, it has excellent mechanical properties, namely abrasion and scratch resistance, also being antistatic. Additionally, despite of its thin thickness, the coating layer 4 also acts as a decorative layer due to the presence of said leveling interface 3 which prevents its aesthetical degradation due to roughness transmission from the intermediate layer 2 to which is connected.

In case of a floating floor, the coating layer 4' is disposed on the lower side of the floor (which is facing the ground). Layer 4' may act similarly to the coating layer 4, or differently, such as support base, moisture barrier, etc., whereby it is made of material selected from the group comprising cork material, thermolaminate material, melamine paper, wood veneer and the like, and combinations thereof. It is important to ensure the adhesion between different layers in order to achieve a laminated final product which is solid and durable. Usually, connection between layers is made by resins which are very well known by persons skilled in the art. The different layers may be connected to each other by using well known prior art procedures.

PREFERRED EMBODIMENTS OF THE INVENTION

In an embodiment of the invention, the board is made of symmetrically disposed layers, comprising a core layer 1 of wood based material which comprises: on one side, at least one intermediate layer 2 of cork based material disposed therein and, at least one coating layer 4 of thermolaminate material disposed on layer 2; and on the other side, at least one intermediate layer 2' of cork based material disposed therein, and at least one coating layer 4' of thermolaminate material disposed on layer 2'. Additionally, at least one leveling layer (3) is disposed between said layers (2) and (4) and at least one leveling layer (3) is disposed between said layers (2') and (4').

Fig. 1 shows a preferred embodiment of a laminated board of the present invention, comprising one core layer 1 of HDF material, on its both sides is simmetrically disposed, on the one side, one intermediate layer 2 of cork composite and, on the other side, one intermediate layer 2' of cork composite. On each of layers 2, 2\ one leveling layer 3 made of melamine resin impregnatable paper is disposed, which in turn has one coating layer 4 of decorative thermolaminate material on one side, and one coating layer 4 ^* of thermolaminate material on the other side.

This preferred laminated board has a symmetric arrangement with seven layers, wherein core layer 1 has a thickness of about 7.3 mm; each of layers 2, 2' has a thickness of about 0.8 mm, each leveling layer 3 has a grammage of about 150 g/m ² and each of layers 4, 4' has a thickness of about 0.7 mm. The preferred board of the invention is fully symmetric in relation to core layer 1 , which means it has the same number of layers with same material on either side of the board as well as the same relative thicknesses. This arrangement provides the board with excellent physical characteristics and also simplifies the production process resulting in cost reduction.

Several tests performed in flooring made of preferred laminated boards of the present invention are herein below described. The results show the quality of a flooring of this type by comparison with conventional flooring of wood and cork.

According to European standard EN 13329 and with respect to abrasion resistance, results were obtained above 8000 rotation taber, corresponding to class 34, and AC6 for abrasion resistance. These results are much better than those shown in the standard which relate to the best possible results for wood and cork flooring covered with one surface film.

In relation to impact strength, also according to European standard EN 13329, class 34, and IC3 for impact strength were achieved, corresponding to higher values than the maximum value required to achieve the maximum classification of said European standard EN 13329. Like in the prior test, the results obtained in this test are largely higher than those obtained by conventional wood and cork flooring covered with one surface film.

Still according to European standard EN 13329, the flooring of the invention was tested to assess its expansion, the results being less than 4% of expansion, which are not easy to find in wood and cork flooring.

Also according to European standard EN 13329, tests for assessing the discoloration and oxidation were performed which disclosed high resistance of the flooring to those events. Regarding sound performance tests, the preferred boards of the invention achieved lowering of transmitted noise (impact sound) of about 18 dB and of reflected noise (step- sound) of about 76 dB. Until the present invention, these results were only possible with wood and cork based products having substantially thicker layers than those of the present invention.

The flooring of the invention also fulfills the European standard EN 1815 with respect to anti-static characteristic. This characteristic is not present in wood and cork flooring.

Scratch resistance was assessed, according to European standard EN 438, and a higher output than 5N was obtained, which is considerably higher than respective output from wood and cork flooring.

Example

A test with several boards divided into two groups was performed. Both groups of boards were similar in structure with exception of the fact that first group of boards included the leveling layer of the present invention. The leveling layer was not present in the second group of boards.

Boards were made of one core layer of MDF wood in which sides intermediate layers of black condensate cork were glued. On either available side of said black condensate cork layer one decorative coating layer of thermolaminate material was disposed, wherein on boards from first group a further layer of melamine resin impregnated leveling paper having a grammage of 90 g/m ² was disposed between said layers of black condensate and said outer layers of thermolaminate material. The thickness of board layers were the same in both groups, such that MDF core layer having 10 mm, intermediate layers of black condensate cork having 1 mm and thermolaminate layers having 0.7 mm. After 2 minutes pressing, boards of both groups showed undesired buckling.

It was further noted that thermolaminate layers in the second group boards showed glue on its surfaces, which boards additionally showed a rough appearance, and bubbles were noticed in a number of boards. After complete cooling of boards from the second group, the thermolaminate layer was easily detached from the black condensate cork intermediate layer.

Regarding boards from first group, with the exception of said above mentioned buckling, the surface appearance was excellent and none of the above issues was noted.

Several further tests with boards similar to the first group boards were carried out with different pressing times in order to overcome the aforementioned buckling problem, which was solved by adjusting said pressing time.