Floor panel

Abstract

The present invention relates to a hard surface floor panel suitable for constructing a floor covering, comprising a core layer, a decorative top layer, and a layer between the core layer and the decorative top layer capable of improving acoustic performance.

Description

[0001] This application is a divisional application of the patent application with application number 2022104819736, application date May 5, 2022, and invention name “Floor Panel”. Technical Field

[0002] The invention relates to a floor panel suitable for constructing hard surface floor coverings. Background Art

[0003] Sound, or noise, is a key design consideration in modern residential, commercial, and industrial buildings. Noise in buildings without proper sound management is transmitted between rooms, while surfaces within the rooms reflect, absorb, or even enhance the noise. This noise can disturb workers or residents and lead to adverse health effects such as sleep disturbances, stress, and headaches. Noise is generally understood to include two types: airborne sound (such as from speech or television) and impact sound (such as from footsteps or objects falling on the floor). Traditionally, sound management solutions designed to improve the acoustic performance of buildings include acoustic ceilings, wall treatments, and even acoustic floors, which focus on reducing the amplitude (intensity) of noise transmitted to adjacent rooms or scattering sound waves to reduce reflections.

[0004] Hard surface floor coverings have gained popularity due to their rigidity and strength. However, it is also known that hard surface floor coverings have relatively poor acoustic properties, particularly due to the rigidity of the top surface, and are therefore generally unsuitable for use as sound absorbing floor coverings. This is further exacerbated by the rigidity required for use as floating floors (generally defined as >3500 MPa when tested according to EN 310), which are floors with interlocking mechanisms that can be installed abuttingly without adhesive to provide sufficient strength to the panels, thereby featuring an interlocking mechanism and bridging the subfloor defects. In the face of these disadvantages, attempts are known to improve and thereby reduce the amplitude of at least some frequencies of transmitted sound of hard surface floor coverings by providing a cushion between the decorative floor and the subfloor, or by adhering an acoustic insulation mat to the back of the decorative floor in the factory. This type of cushion provides a low-density, porous buffer layer that reduces the amplitude of certain frequencies of sound waves passing through the floor by friction between air particles and its pore walls. The sole purpose of this buffer layer is to absorb some of the sound energy passing through the floor panels. To date, there has been no technical solution to improve the reflected foot traffic sound of hard surface floor coverings.

[0005] The disadvantages of the prior art for improving the acoustic performance of floor coverings are threefold. Firstly, the sound attenuation achieved by the resulting impact sound is limited by the thickness of the floor covering (typically in the range of 3 mm to 15 mm), which limits the thickness of the buffer layer and the optimum range of hole sizes for optimum sound diffusion. Secondly, "hard surface" floor coverings are by definition characterized by a surface having a relatively high hardness of greater than 46 Shore D. Thirdly, these panels are characterized by a stiffness greater than 3500 MPa to allow floating installation. The combination of these features results in particularly disturbing high-pitched noises and greatly limits the possibilities for attenuation of impact sound and reflected foot traffic transmission. Summary of the invention

[0006] Therefore, there is a need for a (hard, rigid) surface floor covering which addresses at least one of the shortcomings of the current technology or which provides at least one alternative.

[0007] The present invention provides a floor panel, in particular a (hard) surface floor panel suitable for constructing a (hard) floor covering, the floor panel comprising at least one core layer, at least one decorative top layer and at least one compressible layer located between the core layer and the decorative top layer, wherein the decorative top layer has a bending strength (flexibility) below 1800 MPa and / or wherein the compressible layer has a Shore A hardness below 75.

[0008] The panels according to the invention have several advantages over the prior art.

[0009] The combined use of a decorative top layer with a bending strength below 1800 MPa and / or a compressible layer with a Shore A hardness below 75 located between the core layer and the decorative top layer results in a significant reduction in the sound generated. It has also been found that a reduction in the reflected sound and / or the transmitted impact sound can be obtained. The inventors of the present invention have experimentally found through extensive testing that the best sound attenuation performance is not achieved by reducing the transmitted sound, but by reducing the sound generated when the floor surface is stimulated by an impact, in particular. By absorbing and converting the kinetic energy of the impact, a significant reduction in the amplitude and pitch of the generated sound can be achieved. Decorative top layers with a bending strength below 1800 MPa can be classified as relatively soft top layers. Compressible layers with a Shore A hardness below 75 are generally configured to be temporarily deformed, and in particular to be compressed. It has been experimentally found that the combination of a relatively hard and / or flexible (low bending strength) decorative top layer and a compressible layer according to the present invention has an unexpected positive effect on sound attenuation because the generated sound is attenuated. For the combination of a decorative top layer and a compressible layer according to the present invention, a result of 26 dB attenuation was found. This result can even be obtained with a construction that is significantly thinner than prior art floor constructions featuring a rigid top layer or flexible floor coverings featuring no compressible layer between the core layer and the top layer. A combination of a decorative top layer and a compressible layer wherein the decorative top layer has a flexural strength below 1800 MPa and / or wherein the compressible layer has a Shore A hardness below 75 is not an obvious solution for a person skilled in the art, since the state of the art is only focused on attenuating the generated sound rather than damping the generated sound.

[0010] The flexural strength of flooring layers (e.g., decorative top layers, compressible layers, and / or core layers) is typically measured in accordance with EN310 or ASTMD790. The flexural strength measured in accordance with the standards measures the ability of a material as a whole to withstand deformation when a vertical force is applied to the surface of the material. The hardness of a panel layer can also be measured with a durometer. In this method, a higher value corresponds to a higher hardness. Hardness is an indication of the ability of a material to deform locally at a pressure point when a vertical force is applied to the surface of the material being tested. Shore A typically uses a needle with a blunt tip for softer materials; while Shore D uses a needle with a sharp angle of 30° at the end for medium-hard surface measurements to hard surface measurements. Typically, the Shore A grade can be composed of very soft (0 to 40), soft (40 to 75), and medium-hard (75 to 95); the Shore D grade can be composed of soft (8 to 25), medium-hard (25 to 46), and hard (46 to 90). There is some overlap between the two scales, with a (soft) Shore A hardness of 40 to 75 being similar to a Shore D hardness of 8 to 25; and a (medium-hard) Shore A hardness of 75 to 95 being similar to a Shore D hardness of 25 to 46. By way of illustration, laminate panels featuring a high-density fiberboard core and a melamine-impregnated top layer have a hardness in the range of 80 to 90 Shore D; rigid (hard) vinyl has a hardness in the range of 70 to 90 Shore D; conventional glued LVT has a hardness of about 50 to 55 Shore D; and ceramic tile has a hardness of 80 to 90 Shore D. Since impact noise is generated by a hard object (shoe heel, chair, smartphone, etc.) hitting a hard surface, the harder the surface, the higher the amplitude and pitch of the noise generated, and conversely, the softer the surface or object, the lower the amplitude and pitch of the noise generated. When hard surface floor coverings are excited by footsteps or by the above-mentioned measuring equipment such as a tapping machine, the sound produced has a high pitch and a large amplitude, which, as mentioned above, is particularly disturbing to human perception.

[0011] In a preferred embodiment of the panel, the compressible layer has a Shore A hardness below 75. This means that a compressible layer with a Shore A hardness below 75 allows the layer to be deformed relatively easily. In a further preferred embodiment, the compressible layer has a Shore A hardness below 65, more preferably below 55. The Shore A hardness of the compressible layer may for example be in the range of 45 to 65. In an advantageous embodiment, the Shore A hardness of the compressible layer is at most 55.

[0012] The compressive strength of the compressible layer can also be measured according to EN 826. The compressive strength is an indication of the ability of a material to deform locally at a pressure point when a perpendicular force is applied to the surface of the material. According to this test method, a Shore A hardness of 75 is roughly equivalent to 445psi or 3Mpa. Preferably, the compressible layer has a compressive strength of less than 400kPa, and more preferably has a compressive strength of less than 200kPa. A compressible layer with a compressive strength of less than 200kPa allows deformation and can recover to its initial state relatively quickly after being subjected to stress. It is also conceivable that the compressible layer has a compressible strength of up to 3MPa. The use of such a compressible layer can further contribute to the absorption and / or conversion of the kinetic energy of the impact, thereby enabling a significant reduction in the amplitude and pitch of the sound produced. It has been found experimentally that good results are obtained when such a compressible layer is applied.

[0013] The compressible layer may comprise a material selected from the group consisting of closed-cell flexible foam, compressible foam, flexible polymer, elastomer, compressible natural material and / or any combination thereof. Preferably, the compressible layer comprises at least 50% of a foam material, in particular a closed-cell foam material. Optionally, the compressible layer comprises at least 80% of a closed-cell foam material. Closed-cell foam materials are preferred because they enable sufficient compressible behavior while being strong enough to support the decorative top layer and the applied load. The compressible layer may, for example, be made of closed-cell flexible foam. The compressible layer may also comprise semi-closed-cell or open-cell compressible foam. Open-cell structures have the advantage of improved sound absorption. The compressible layer may, for example, comprise polyolefin foam, expanded polystyrene, expanded polypropylene, expanded rubber, expanded ethylene vinyl acetate, expanded ethylene and / or expanded polyethylene. The compressible intermediate layer may also be a substantially solid non-foamed layer. In this case, the best results are obtained using a material selected from the group of flexible polymers and elastomers, such as rubber, latex, acrylic elastic epoxy resin, cis-polyisoprene (natural rubber, NR), cis-polybutadiene (butadiene rubber, BR), nitrile rubber (NBR), styrene-butadiene rubber (SBR), rubber, latex and / or ethylene-propylene monomer (EPM). The compressible layer may, for example, include compressible natural materials such as felt, cotton, wool, mycelium, hemp, cork and / or the like. The compressible layer may be any combination of the above-mentioned foam and / or non-foam materials. These examples are non-limiting and any similar foam material with equivalent material properties may be applied. The thickness of the compressible layer is typically in the range of 0.8 mm to 4 mm, in particular in the range of 0.8 mm to 2 mm. In a further preferred embodiment, the compressible layer has a thickness in the range of 0.75 mm to 1.25 mm in the uncompressed state.

[0014] Preferably, the acoustic impedance of the compressible layer is at most 8 MRayl, more preferably at most 5 MRayl, even more preferably at most 2 MRayl. Preferably, the acoustic impedance of the compressible layer is lower than the acoustic impedance of the decorative top layer. Optionally, the acoustic impedance of the compressible layer is at least less than half the impedance of the decorative top layer, preferably less than one quarter the impedance of the decorative top layer. Preferably, the acoustic impedance of the compressible layer is lower than the acoustic impedance of the decorative top layer. Optionally, the acoustic impedance of the compressible layer is at least less than half the impedance of the decorative top layer, preferably less than one quarter the impedance of the decorative top layer. Optionally, the acoustic impedance of the compressible layer is at least less than half the impedance of the core layer, preferably less than one quarter the impedance of the core layer.

[0015] It is also conceivable that the compressible layer comprises at least one intermediate acoustic impedance layer, preferably, wherein the acoustic impedance of the intermediate acoustic impedance layer is at least 4 Mrayl, preferably at least 7 Mrayl, more preferably at least 10 Mrayl. It is also conceivable that the acoustic impedance of the intermediate acoustic impedance layer is at most 8 Mrayl, preferably at most 5 Mrayl, more preferably at most 2 Mrayl. If applied, the thickness of the intermediate acoustic impedance layer is in the range of 0.05 mm to 2 mm, preferably in the range of 0.1 mm to 0.7 mm. In a preferred embodiment, the intermediate acoustic impedance layer comprises at least one additive, which preferably has an acoustic impedance higher than 30 Mrayl. The use of such an additive can have a further positive effect on the acoustic properties of the panel itself. The compressible layer can include at least one additive selected from the following group: iron, silicon carbide and / or aluminum oxide. The additives can also contain iron, silicon carbide and / or aluminum oxide. The additives are relatively heavy, which prevents them from vibrating in the material. The additives can be dispersed in at least a portion of the intermediate acoustic impedance layer.

[0016] The thickness of the decorative top layer may be in the range of 0.5 to 3 times the thickness of the compressible layer. In a preferred embodiment, the thickness of the decorative top layer is at least equal to the thickness of the compressible layer. Preferably, the compressible layer and the decorative top layer are configured such that the decorative top layer can be deformed into the compressible layer.

[0017] In a preferred embodiment, the flexural strength of the decorative top layer is below 1500 MPa, preferably below 1200 MPa, more preferably below 900 MPa. Preferably, the decorative top layer has a flexural strength of at least 300 MPa. The decorative top layer may, for example, have a flexural strength in the range of 300 MPa to 900 MPa. It has been found experimentally that decorative top layers having said flexural strength values ​​provide good sound attenuation results.

[0018] Preferably, the upper surface of the decorative top layer has a Shore D hardness of at least 46. The Shore D hardness of the upper surface of the decorative top layer may be, for example, in the range of 46 to 90, in the range of 46 to 60, or in the range of 61 to 90. The Shore D hardness of the upper surface of the decorative top layer may also be in the range of 50 to 80, preferably in the range of about 60 to 70. It has been found experimentally that a decorative top layer having the required bending strength and a Shore D hardness of about 60 to 70 has all the advantages of a hard surface floor covering, including scratch resistance, easy cleaning, indentation resistance, and also has greatly improved acoustic performance, and provides sufficient hardness to withstand heavy traffic.

[0019] Preferably, the decorative top layer comprises at least one polymer material. The decorative top layer may, for example, be at least partially made of polyvinyl chloride (PVC), polyurethane (PU), polypropylene (PP), polyethylene terephthalate (PET), chlorinated polyethylene (CPE), polyethylene (PE), chlorinated PVC (CPVC), acrylonitrile butadiene styrene (ABS), polycarbonate (PC), etc. Preferably, the top layer comprises flexible PVC, flexible PET or a flexible PP composite. Preferably, the top layer comprises flexible PVC. The density of PVC may, for example, be 1.1 g / cm 3 Up to 1.35g / cm 3 Preferably, the decorative top layer further comprises at least one mineral filler. Non-limiting examples of mineral fillers used are talc, calcium carbonate (CaCO3) and / or perlite. The decorative top layer may, for example, comprise up to 15 wt% (weight %), preferably up to 10 wt% of filler.

[0020] Preferably, the decorative top layer comprises at least one plasticizer, such as, but not limited to, external or internal plasticizers, including: phthalate plasticizers, such as DEHP, DOP, DIDP, DTDP; non-OTP plasticizers, such as DOTP, DINCH; bioplasticizers, such as soybean oil; copolymers, such as ASA, ABS, MBS, chlorinated polyethylene (CPE), acrylates (ACR), or elastomers selected from the group consisting of polyolefin elastomers, copolymers of ethylene-butene or ethylene-octene, nitrile rubber (NBR), etc. It is conceivable that the decorative top layer comprises at least one internal plasticizer and / or at least one external plasticizer. The use of at least one plasticizer can actively contribute to the softness and / or flexibility of the decorative top layer, which improves the sound damping effect of the panel according to the invention. The decorative top layer may also include other additives, such as but not limited to flame retardants (ATH, MDH, etc.); stabilizers (e.g., metal soaps such as zinc stearate, calcium-zinc stearate, calcium stearate, etc.); UV inhibitors, microbicides such as antimicrobial agents, antiviral agents (si-quat), antibacterial agents and antifungal agents; processing aids and lubricants, such as solid or liquid fatty esters, fatty alcohols, fatty acid esters, ester waxes, solid hydrocarbons (such as paraffin or polyethylene wax); titanium dioxide and similar whitening agents, foaming agents and / or foaming regulators, etc.

[0021] In a preferred embodiment, the decorative top layer includes at least one decorative layer and / or at least one wear layer. The wear layer can be, for example, a scratch-resistant layer. The decorative top layer can include a wear layer or a finishing layer, for example, with a thermosetting varnish or paint, such as polyurethane, PUR or melamine-based resin. In a preferred embodiment, the top layer includes at least one substantially transparent wear layer or finishing layer. The wear layer can include one or more transparent layers of thermoplastic or thermosetting resins. Non-limiting examples of thermoplastic or thermosetting materials that can be used are polyvinyl chloride (PVC), polystyrene (PS), polyethylene (PE), polyurethane (PU), acrylonitrile-butadiene-styrene (ABS), polypropylene (PP), polyethylene terephthalate (PET), phenolic resin and / or melamine resin or formaldehyde resin. The wear layer can also be a liquid or paste form made of a thermosetting resin, such as but not limited to a phenolic resin and / or melamine resin or formaldehyde resin. The wear layer may comprise, or may consist essentially of, an inherently scratch resistant thermosetting resin impregnating a carrier layer such as paper or lignocellulose. An advantage of the latter embodiment (the embodiment consisting essentially of the inherently scratch resistant thermosetting resin as described above) is that the urea-formaldehyde also acts as a relatively scratch resistant wear layer. Typically, the preferred thickness of the wear layer structure in the panel of the present invention is in the range of 0.1 mm to 2.0 mm, more preferably between 0.15 mm and 1 mm, and most preferably between 0.2 mm and 0.8 mm.

[0022] In a preferred embodiment, the wear layer or the finishing layer may comprise at least one coating. For example, the at least one coating may comprise an at least partially transparent or translucent protective coating. In a preferred embodiment, the at least one coating may be, for example, a polyurethane coating, an acrylic coating and / or an epoxy polyol coating. Such a coating may, for example, be an ultraviolet (UV) curable coating or an electron beam (EB) curable coating. It is also conceivable that the coating comprises a thermosetting resin and a photoinitiator crosslinked by a UV or electron beam curing method.

[0023] In an optional embodiment, the decorative layer consists essentially of a carrier material layer designed to be provided with a decorative pattern at the upper side. Suitable materials are woven, extruded or calendered plastic meshes, sheets or films. Non-limiting examples of thermoplastic or thermosetting materials that can be used are polyvinyl chloride (PVC), polystyrene (PS), polyethylene (PE), polyurethane (PU), acrylonitrile-butadiene-styrene (ABS), polypropylene (PP), phenolic resins and / or melamine resins or formaldehyde resins.

[0024] Alternatively, the decorative layer may include at least one cellulose-based layer and optionally a cured resin, wherein the cellulose-based layer is preferably paper, wood veneer, bamboo veneer, etc. Such a decorative layer may include a plurality of such resin-impregnated paper or wood veneer board layers. The decorative layer may also include a facing of stone or cured clay, or a porcelain tile or ceramic tile. Alternatively, the decorative layer may include a bottom primer or coating, which is applied in a liquid or semi-liquid state, then cured, and then receives at least one decorative visual piece in the form of ink provided in dots to form a desired visual effect as a whole. This ink may be composed of at least 3 colors based on a standard color scheme and applied in an amount of 0.1pl to 50pl / dot. For flooring purposes, a preferred color scheme may be applied at a resolution of at least 350dpi, more preferably at least 400dpi.

[0025] The thickness of the decorative top layer is typically in the range of 0.5 mm to 2.5 mm, preferably in the range of 0.8 mm to 2 mm. Typically, the thickness of the decorative top layer is less than 3.5 mm, preferably less than 3 mm, more preferably less than 2.75 mm. It is beneficial to apply a relatively thin decorative top layer. This will actively contribute to the flexibility of the decorative top layer and thus to the sound attenuation properties of the panel.

[0026] Optionally, the panel comprises at least one reinforcing layer, the at least one reinforcing layer being positioned between the decorative top layer and the compressible layer. The reinforcing layer is preferably configured to improve the performance of the decorative top layer without adversely affecting its flexibility. It is envisaged that the at least one reinforcing layer forms an integral part of the decorative top layer. The reinforcing layer may, for example, be embedded in the decorative top layer. The reinforcing layer may, for example, comprise glass fibres.

[0027] In a preferred embodiment, the decorative top layer comprises at least one additive having an acoustic impedance higher than 30 MRayl. It is also conceivable that at least one layer included in the decorative top layer comprises at least one additive having an acoustic impedance higher than 30 MRayl. The use of such an additive may have a further positive effect on the acoustic properties of the panel itself. The decorative top layer may comprise at least one additive selected from the following group: iron, silicon carbide and / or aluminum oxide. The additives may also contain iron, silicon carbide and / or aluminum oxide. The additives are relatively heavy, which prevents them from vibrating in the material. The additives may be buried in at least part of the decorative top layer. The acoustic impedance of the decorative top layer is typically at least 4 Mrayl, preferably at least 7 Mrayl, more preferably at least 10 Mrayl.

[0028] In yet another embodiment, the decorative top layer comprises at least one upper acoustic impedance layer having an acoustic impedance of at least 4 Mrayl, preferably at least 7 Mrayl, more preferably at least 10 Mrayl. The thickness of the upper acoustic impedance layer may be in the range of 0.05 mm to 2 mm, preferably in the range of 0.1 mm to 0.7 mm. The upper acoustic impedance layer may, for example, be directly attached to the upper side of the compressible layer. It is also conceivable that the upper acoustic impedance layer is encapsulated between other laminate layers of the decorative top layer. The upper acoustic impedance layer may impart at least some support and / or flexibility to the decorative top layer. It is conceivable that the upper acoustic impedance layer is directly or indirectly connected to other decorative and / or protective elements facing upward, such as decorative films, vinyl veneers, LVT, at least one cellulose-based layer and cured resin, wood veneers, bamboo veneers, tile veneers, stone veneers, clay veneers, etc., thereby imparting the required flexibility and support to the top layer to achieve enhanced acoustic performance. It is conceivable that any layer included in the decorative top layer is used as a high impedance layer. Thus, a high impedance layer may be understood as any portion of the decorative top layer comprising at least 0.5 wt%, preferably at least 1 wt%, more preferably at least 5 wt% of a high impedance material, in particular a high impedance material in order to increase the impedance of the decorative top layer. It is also conceivable that the high impedance layer forms part of a layer comprised in the decorative top layer. The decorative top layer may comprise at most 15 wt%, preferably at most 10 wt%, more preferably at most 5 wt% of a high impedance material.

[0029] Furthermore, it is noted that the combination of the upper acoustic impedance layer with the compressible layer according to the invention further improves the acoustic performance of the structure. The inventors theorize that a high impedance layer at the panel surface, such as the upper acoustic impedance layer, is not able to vibrate and therefore does not produce sound as efficiently or easily as a low impedance layer when subjected to the same kinetic energy. This also applies to the decorative top layer, which is a high impedance layer. A reduction of up to 26 dB amplitude was achieved at the 100 Hz to 4000 Hz frequency band, while the average tone produced was reduced by up to 5 octaves by combining (combining into the laminate) the following layers from top to bottom: a 0.5 mm PVC decorative layer of 1800 MPa stiffness and 65 Shore D hardness; a 0.5 mm iron particle filled CPE composite foil of 1800 MPa stiffness and 8 Mrayl impedance, and a 1 mm IXPP compressible layer of 55 Shore A hardness.

[0030] It is also conceivable that, where applied, the boundary surface between at least one intermediate acoustic impedance layer incorporated in the compressible layer and at least one upper acoustic impedance layer incorporated in the decorative top layer forms a first reflection boundary in the structure of the floor panel. It is conceivable that the ratio between the acoustic impedances of the two (panel) layers forming the first reflection boundary is greater than 2:1, most preferably greater than 4:1. The greater the difference between the acoustic impedances of the two materials at the first reflection boundary, the greater the reduction in the transmitted sound. It is conceivable that the ratio between the acoustic impedances of the two materials at the boundary is greater than 10:1.

[0031] The compressible layer and the decorative top layer may form a first reflection boundary. Where applied, the compressible layer and at least one upper acoustic impedance layer incorporated in the decorative top layer may also form a first reflection boundary. Where an intermediate acoustic impedance layer is applied, the intermediate acoustic impedance layer and the decorative layer and / or the upper acoustic impedance layer may form a first reflection boundary. It is envisaged that the ratio between the acoustic impedances of the two (panel) layers forming the first reflection boundary is greater than 2:1, most preferably greater than 4:1. The greater the difference between the acoustic impedances of the two materials at the first reflection boundary, the greater the reduction in the transmitted sound. It is envisaged that the ratio between the acoustic impedances of the two materials at the boundary is greater than 10:1.

[0032] It is also conceivable that the decorative top layer serves as an upper acoustic impedance layer. Thus, an upper acoustic impedance layer is understood to be any portion of the decorative top layer comprising at least 0.5 wt%, preferably at least 5 wt%, of a high impedance material, in particular a high impedance material in order to increase the impedance of the decorative top layer. It is also conceivable that the upper acoustic impedance layer constitutes part of a layer comprised in the decorative top layer.

[0033] Preferably, the panel according to the invention comprises at least one core layer. The presence of a core layer may further contribute to the acoustic performance of the panel. It is beneficial to apply a core layer having a stiffness of at least 3500 MPa (particularly when measured according to EN310 or ASTM D790). Such a core layer benefits from the high stiffness to provide sufficient support for the decorative top layer and the compressible layer, and may allow an interlocking mechanism to be provided. The core layer may also act as an impedance layer.

[0034] A non-limiting example of a core layer that can be applied is a composite core layer comprising at least one mineral material and at least one adhesive. Preferably, the core layer is made of a relatively brittle material having a high compressive strength. The core layer can, for example, comprise at least 60 wt % of a mineral material, preferably at least 70 wt % of a mineral material. A higher mineral content generally results in a more rigid core layer and, therefore, a more rigid panel. In addition, due to the relatively large amount of mineral material, a relatively good temperature resistance can be obtained, in particular relative to conventional floor panels having a core layer that is mainly based on PVC. It is conceivable that at least one core layer comprises at least one mineral material selected from the group consisting of magnesium oxide, calcium carbonate, chalk, clay, calcium silicate and / or talc. As another non-limiting example, limestone (e.g. calcium carbonate and magnesium carbonate) can be used as the mineral material in the core layer. Optionally, the mineral material is present as a particulate mineral filler.

[0035] Preferably, the core layer further comprises at least one reinforcing additive selected from the group consisting of fibrous materials, fibers such as but not limited to steel, glass, polypropylene, wood, acrylic, alumina, curaua, carbon, cellulose, coconut, Kevlar, nylon, polyamide, polyethylene, PVA, asbestos, viburnum, glass fiber and / or fique. This can further increase the strength of the panel itself. The core layer may also comprise at least one natural material such as wood fiber, mycelium, wool, straw, etc.

[0036] Preferably, the density of the core layer is at least 1200 kg / m 3 , preferably at least 1400 kg / m 3 The density of the core layer can be, for example, 1600 kg / m 3 Up to 2100kg / m 3The core layer may be used, for example, as a (high) acoustic impedance layer. The impedance of the core layer is preferably at least 4 Mrayl, preferably greater than 7 Mrayl, and most preferably greater than 10 Mrayl. Adding high impedance materials such as copper, iron, aluminum oxide, etc. to at least a portion of the core layer can effectively increase the impedance of the core layer. It is conceivable that any layer included in the core layer is used as a (high) acoustic impedance layer. Therefore, an acoustic impedance layer can be understood as any part of the core layer that includes at least 0.5 wt%, preferably at least 5 wt% of a high impedance material to increase the impedance of the core layer. At least a portion of the core layer may, for example, include at least 0.5 wt%, preferably at least 1 wt%, more preferably at least 2 wt% of an additive having an acoustic impedance higher than 30 Mrayl. It is also conceivable that at least a portion of the core layer includes at most 15 wt%, preferably at most 10 wt%, more preferably at most 5 wt% of an additive having an acoustic impedance higher than 30 Mrayl. It is also conceivable that the (high) acoustic impedance layer constitutes part of a layer included in the core layer. The core layer may be designed such that the impedance of the core material is key to further attenuating the sound. The results showed that when the applied density was 1600 kg / m 3 Up to 2100kg / m 3 When a core layer having a density within the range of , an improved sound attenuation of up to 30 dB is observed. It is beneficial if the core layer having a density within the range also has an acoustic impedance greater than 7 MRayl and in conjunction with the other characteristics according to the invention. This can be interpreted as such a core layer being effective in blocking any remaining higher frequencies still generated during excitation of the top surface. It is conceivable that the core layer is at least partially foamed and has a density gradient. In a preferred embodiment, the material density of the core layer at its top and / or bottom surface is at least 5% higher, more preferably at least 20% higher, than that of the rest of the core layer.

[0037] In a preferred embodiment, at least a portion of the upper and / or lower surfaces of the core layer comprises a plurality of cavities. The presence of cavities in the upper and / or lower surfaces of the core layer can further contribute to sound diffusion, sound distribution and / or attenuation. A plurality of cavities may, for example, define a predetermined pattern, which may be a repeated cavity pattern. Preferably, the upper and / or lower surfaces of the core layer at least partially comprise a predetermined pattern of sound diffusion cavities that scatter incoming and / or outgoing sound waves. Optionally, at least a portion of the cavities may be different in depth, shape, size and / or angle. It is conceivable that the sound diffusion cavity is characterized by being designed to scatter different depths, shapes, sizes and / or angles of sound waves of different frequencies. At least a portion of the cavity may be an embossed cavity. At least a portion of the cavity may, for example, be obtained by embossing, rotary embossing and / or rotary (mold) cutting. It is beneficial that the cavity is present in the central region of the panel. At least one outer edge of the core layer and preferably all outer edges may be free of cavities. Therefore, it is conceivable that one or more cavities do not extend through the outer edge of the panel. For example, it is conceivable that there is no cavity at least 1 cm from each outer edge of the panel.For example, it is also optional that the circumferential edge of the panel and in particular the core layer is free of cavities over a range of at least 2 cm.

[0038] In case of applying a core layer comprising a plurality of cavities, in the upper and / or lower surface of the core layer, the density is determined only by the actual material of the core layer, without taking the cavities into account. Therefore, preferably, the material of the core layer has a density of at least 1200 kg / m 3 The density is preferably at least 1400 kg / m 3 The density of the core material can be, for example, 1600 kg / m 3 Up to 2100kg / m 3 within the range.

[0039] The acoustic impedance of the core layer may be at least 4 Mrayl, preferably at least 7 Mrayl, more preferably at least 10 Mrayl. It is also conceivable that the core layer comprises at least one further impedance layer having an impedance of at least 4 Mrayl, preferably at least 7 Mrayl, more preferably at least 10 Mrayl.

[0040] In a preferred embodiment, the compressible layer and the at least one acoustic impedance layer incorporated in the core layer form a second impedance boundary in the structure of the floor panel. Thus, the ratio between the acoustic impedances of the two materials at the boundary is preferably greater than 2:1, most preferably greater than 4:1. The greater the difference between the acoustic impedances of the two materials at the boundary, the greater the reduction in transmitted sound. It is conceivable that the ratio between the acoustic impedances of the two materials at the boundary is greater than 10:1.

[0041] Typically, the thickness of the core layer is in the range of 2mm to 8mm, preferably in the range of 3mm to 5mm. Another non-limiting example is a core layer in the range of 3.5mm to 4.5mm. In another preferred embodiment, the panel (and in particular the core layer) includes at least one pair of opposite side edges, which are provided with interconnecting coupling portions for interconnecting adjacent panels. The panel according to the present invention may include at least one pair of opposite (side) edges, which include complementary coupling portions configured for interconnection of adjacent panels. The coupling portion of the panel may be, for example, an interlocking coupling portion, which is preferably configured to provide horizontal and vertical locking. The interlocking coupling portion is a coupling portion that requires elastic deformation, snap-on (click) or movement in multiple directions to connect or disengage the coupling portions to each other. Any suitable interlocking coupling portion known in the art may be applied. A non-limiting example is an embodiment wherein a first edge of a first pair of opposing edges includes a first connecting portion, and wherein a second edge of the first pair of opposing edges includes a complementary second connecting portion, the connecting portions allowing a plurality of panels to be connected to each other; wherein the first connecting portion includes a lateral tongue extending in a direction substantially parallel to a plane defined by the panels, and wherein the second connecting portion includes a groove configured to accommodate at least a portion of a lateral tongue of another panel, the groove being defined by an upper lip and a lower lip.

[0042] In a preferred embodiment, the panel comprises at least one backing layer attached to the back side of the core layer. The backing layer may also be referred to as a buffer layer or a damping layer. The backing layer is typically made of a polymer material, such as, but not limited to, a low-density foam layer of ethylene vinyl acetate (EVA), radiation cross-linked polyethylene (IXPE), expanded polypropylene (XPP) and / or expanded polystyrene (XPS). However, it is also conceivable that the backing layer comprises non-woven fibers, such as natural fibers like cork, and / or recycled / recyclable materials, such as PET, felt, recycled carpet, etc.

[0043] The buffer or backing layer imparts a sound dampening effect to the panel. The backing layer further helps to provide an optimal interface between the panel and the underlying surface to which it is applied, and may provide a protective function to the core layer. The backing layer also allows for the absorption of some subfloor irregularities.

[0044] Preferably, the backing layer has a thickness of 65 kg / m 3 and 300kg / m 3 The density is in the range of 80 kg / m 3 and 150kg / m 3 The density of the backing layer is generally in the range of about 0.1 mm to about 2.5 mm. Non-limiting examples of materials from which the backing layer can be made are polyethylene, cork, polyurethane, and ethylene vinyl acetate.

[0045] In one embodiment it is also conceivable that the panel comprises (on its back side) at least one balancing layer, typically consisting of at least one layer comprising lignocellulose and a cured resin, a wood veneer or a bamboo veneer or the like.

[0046] The invention further relates to a decorative top layer for use in a panel according to the invention. The invention further relates to a compressible layer for use in a panel according to the invention. The decorative top layer and / or the compressible layer may be any one of the embodiments described. The invention further relates to an assembly of at least one decorative top layer and at least one compressible layer for use in a panel according to the invention.

[0047] Example

[0048] The invention will be further explained by the following non-limiting examples, which represent preferred embodiments of the invention.

[0049] As mentioned above, extensive testing has shown that the best sound attenuation performance is achieved not by reducing the transmitted sound, but by reducing the generated sound. The tapping machine features six metal hammers designed to apply a fixed force at a fixed frequency on the surface of the floor. Hard surface floor coverings have poor acoustic performance precisely because for their hard surface (usually having an elastic modulus greater than 3500 MPa and a Shore D hardness greater than 46), the impact of the hammer on the surface of any hard surface floor generates noise of about 75 dB at multiple frequencies, especially at higher frequencies ranging from 400 Hz to 4000 Hz.

[0050] To illustrate, below is a table of the reduction in transmitted sound in dB for different types of flooring, different thicknesses, and with / without underlayment.

[0051]

[0052]

[0053] Note that the combination of a flexible top layer with a compressible layer underneath the top layer has an unexpected attenuation result of 26 dB compared to thicker materials featuring a rigid top layer or flexible floor coverings featuring no compressible underlayment.

[0054] The present invention will be further illustrated by the following non-limiting terms.

[0055] 1. A floor panel, in particular a hard surface floor panel, suitable for constructing a floor covering, the floor panel comprising:

[0056] - at least one core layer;

[0057] - at least one decorative top layer; and

[0058] - at least one compressible layer located between the core layer and the decorative top layer;

[0059] Wherein the decorative top layer has a flexural strength of less than 1800 MPa, and / or

[0060] Wherein, the upper surface of the decorative top layer has a Shore D hardness of at least 46.

[0061] 2. The panel according to the preceding clause, wherein at least one compressible layer has a Shore A hardness of 75 or less.

[0062] 3. The panel according to any of the preceding clauses, wherein at least one compressible layer has a compressive strength below 3 MPa.

[0063] 4. A panel according to any of the preceding clauses, wherein the compressible layer has a compressive strength below 200 kPa.

[0064] 5. The panel according to any of the preceding clauses, wherein the compressible layer comprises at least 50% foam material, in particular closed cell foam material.

[0065] 6. A panel according to any of the preceding clauses, wherein the compressible layer comprises a material selected from the group consisting of closed cell flexible foam, open cell foam, compressible natural material and / or compressible elastomer, or a combination thereof.

[0066] 7. A panel according to any of the preceding clauses, wherein the compressible layer comprises polyolefin foam, expanded polystyrene, expanded polypropylene, expanded rubber and / or expanded polyethylene.

[0067] 8. A panel according to any of the preceding clauses, wherein the compressible layer has a thickness in the range of 0.8 mm to 4 mm, preferably in the range of 0.8 mm to 2 mm.

[0068] 9. The panel according to any of the preceding clauses, wherein the compressible layer comprises at least one intermediate impedance layer comprising at least one additive having an acoustic impedance higher than 30 MRayl.

[0069] 10. The panel according to any of the preceding clauses, wherein the intermediate resistance layer comprises at least one additive selected from the group consisting of: iron, silicon carbide and / or aluminium oxide.

[0070] 11. The panel of clause 10, wherein at least a portion of the additive is dispersed in at least a portion of the intermediate resistance layer.

[0071] 12. A panel according to any of the preceding clauses, wherein the compressible layer has an acoustic impedance of at most 8 MRayl, preferably at most 5 MRayl, more preferably at most 2 MRayl.

[0072] 13. A panel according to any of the preceding clauses, wherein the compressible layer comprises at least one intermediate acoustic impedance layer having an acoustic impedance of at most 8 MRayl, preferably at most 5 MRayl and more preferably at most 2 MRayl.

[0073] 14. Panel according to clause 13, wherein the intermediate acoustic impedance layer has a thickness in the range of 0.05 mm to 2 mm, preferably in the range of 0.1 mm to 0.7 mm.

[0074] 15. A panel according to any of the preceding clauses, wherein the decorative top layer has a flexural strength in the range of 300 MPa to 900 MPa.

[0075] 16. The panel according to any of the preceding clauses, wherein the decorative top layer has a Shore D hardness of at least 46.

[0076] 17. The panel according to any of the preceding clauses, wherein the decorative top layer has a Shore D hardness in the range of 46 to 90.

[0077] 18. The panel according to any of the preceding clauses, wherein the decorative top layer comprises at least one polymer material and preferably at least one mineral filler.

[0078] 19. The panel according to any of the preceding clauses, wherein the decorative top layer comprises at least one plasticizer, preferably selected from the group consisting of chlorinated polyethylene, acrylic resins, soybean oil and / or dioctyl terephthalate.

[0079] 20. The panel according to any of the preceding clauses, wherein the decorative top layer comprises at least one decorative layer and / or at least one wear layer.

[0080] 21. A panel according to any of the preceding clauses, wherein the decorative top layer has a thickness in the range of 0.8 mm to 2 mm, preferably in the range of 1.2 mm to 1.8 mm.

[0081] 22. The panel according to any of the preceding clauses, wherein at least a part of the decorative top layer comprises at least one additive having an acoustic impedance higher than 30 MRayl.

[0082] 23. The panel according to any of the preceding clauses, wherein at least a part of the decorative top layer comprises at least 0.5 wt%, preferably at least 5 wt%% of an additive having an acoustic impedance higher than 30 Mrayl.

[0083] 24. The panel according to any of the preceding clauses, wherein the decorative top layer comprises at least one additive selected from the group consisting of: iron, silicon carbide and / or aluminium oxide, wherein preferably at least a portion of the additive is embedded in at least a portion of the decorative top layer.

[0084] 25. The panel according to any of the preceding clauses, wherein the decorative top layer has an acoustic impedance of at least 4 Mrayl, preferably at least 7 Mrayl, more preferably at least 10 Mrayl.

[0085] 26. The panel according to any of the preceding clauses, wherein the decorative top layer comprises at least one upper acoustic impedance layer having an acoustic impedance of at least 4 Mrayl, preferably at least 7 Mrayl, more preferably at least 10 Mrayl.

[0086] 27. The panel according to clause 26, wherein the upper acoustic impedance layer has a thickness in the range of 0.05 mm to 2 mm, preferably in the range of 0.1 mm to 0.7 mm.

[0087] 28. A panel according to any of the preceding clauses, wherein the thickness of the decorative top layer is 0.5 to 3 times the thickness of the compressible layer.

[0088] 29. The panel according to any of the preceding clauses, wherein the thickness of the decorative top layer is at least equal to the thickness of the compressible layer.

[0089] 30. The panel according to any of the preceding clauses, wherein the acoustic impedance of the compressible layer is lower than the acoustic impedance of the decorative top layer.

[0090] 31. The panel according to any of the preceding clauses, wherein the panel comprises at least one reinforcement layer positioned between the decorative top layer and the compressible layer.

[0091] 32. A panel according to any of the preceding clauses, wherein the core layer has a stiffness of at least 3500 MPa.

[0092] 33. The panel according to any of the preceding clauses, wherein the core layer is a composite core layer comprising at least one mineral material and at least one binder.

[0093] 34. A panel according to any of the preceding clauses, wherein the core layer comprises at least 60 wt% mineral material, preferably at least 70 wt% mineral material.

[0094] 35. A panel according to any of the preceding clauses, wherein the core layer has a 3 , preferably at least 1400kg / m 3 density.

[0095] 36. A panel according to any of the preceding clauses, wherein at least a portion of at least one surface of the core layer comprises a plurality of cavities.

[0096] 37. The panel of clause 36, wherein the cavity defines a predetermined pattern.

[0097] 38. The panel according to any of clauses 36 to 37, wherein at least a portion of the cavity varies in depth, size, angle and / or shape.

[0098] 39. The panel according to any of clauses 36 to 38, wherein the cavity is an embossed cavity.

[0099] 40. The panel according to any of the preceding clauses, wherein the core layer has a thickness in the range of 2 mm to 8 mm.

[0100] 41. A panel according to any of the preceding clauses, wherein the core layer has an acoustic impedance of at least 4 Mrayl, preferably at least 7 Mrayl, more preferably at least 10 Mrayl.

[0101] 42. A panel according to any of the preceding clauses, wherein the core layer comprises at least one further impedance layer having an impedance of at least 4 Mrayl, preferably at least 7 Mrayl, more preferably at least 10 Mrayl.

[0102] 43. A panel according to any of the preceding clauses, wherein the panel, and in particular the core layer, comprises at least one pair of opposing side edges provided with interconnecting couplings for interconnecting adjacent panels.

[0103] 44. The panel according to any of the preceding clauses, wherein at least a part of the core layer comprises at least 0.5 wt% and preferably at least 5 wt% of an additive having an acoustic impedance higher than 30 Mrayl. BRIEF DESCRIPTION OF THE DRAWINGS

[0104] The present invention will be further illustrated by means of non-limiting exemplary embodiments shown in the following drawings, in which:

[0105] Figure 1a shows a perspective view of a first embodiment of a floor panel according to the invention;

[0106] Figure 1bShown as Figure 1a The cross section of the panel shown;

[0107] Figure 2 shows a cross section of a second embodiment of a floor panel according to the invention;

[0108] Figure 3 shows a cross section of a third alternative embodiment of a floor panel according to the invention;

[0109] Figure 4 shows a cross section of a fourth alternative embodiment of a floor panel according to the invention;

[0110] Figure 5 A schematic diagram showing an alternative embodiment of a core layer for use in a panel according to the invention;

[0111] Figure 6 shows a roller that can be used to manufacture a core layer used in a panel according to the invention; and

[0112] Figure 7 A perspective view showing another alternative embodiment of a floor panel according to the invention is shown.

[0113] In the drawings, like reference numbers correspond to similar or equivalent elements or features. DETAILED DESCRIPTION

[0114] Figure 1a A perspective view of a first embodiment of a floor panel 101 according to the invention is shown. Figure 1b Shown as Figure 1a A cross section of a panel 101 is shown. The panel 101 comprises a core layer 102, a decorative top layer 103 and a compressible layer 104. The compressible layer 104 is located between the core layer 102 and the decorative top layer 103. The compressible layer 104 comprises a (closed) cell foam material. The decorative top layer 103 benefits from relatively good flexibility properties due to its bending strength below 1800 MPa. The compressible layer 104 according to the present invention has a compressive strength below 400 kPa. The core layer 102 is a substantially rigid core layer. In the embodiment shown, the thickness Td of the decorative top layer 103 is substantially equal to the thickness Tc of the compressible layer 104. The thickness Tu of the core layer is significantly greater than the thickness Td of the decorative top layer 103 and the thickness Tc of the compressible layer 104. The core layer 102 comprises two pairs of opposite side edges. In the embodiment shown, the first pair of opposite side edges are provided with interconnecting coupling portions 108a, 108b for interconnecting adjacent panels 101.

[0115] Figure 2A cross section of a second alternative embodiment of a floor panel 201 according to the present invention is shown. The panel 201 comprises a core layer 202, a decorative top layer 203 and a compressible layer 204. The decorative top layer 203 comprises a decorative layer 203b and a wear layer 203a. The panel 201 further comprises a reinforcing layer 205 between the decorative top layer 203 and the compressible layer 204. In the embodiment shown, the upper surface of the core layer 202 comprises a plurality of cavities 206 in a predetermined pattern configured to scatter incoming sound waves. The panel 201 may optionally comprise a backing layer 207.

[0116] Figure 3 A cross section of a third alternative embodiment of a floor panel 301 according to the invention is shown. The panel 301 comprises a core layer 302, a decorative top layer 303 and a compressible layer 304. The panel 301 further comprises a backing layer 307. The decorative top layer 303 comprises an additive 309, which preferably comprises iron, silicon carbide and / or aluminium oxide. The additive 309 is embedded in at least a portion of the decorative top layer 303.

[0117] Figure 4 A cross section of a fourth alternative embodiment of a floor panel 401 according to the present invention is shown. The panel 401 comprises a core layer 402, a decorative top layer 403 and a compressible layer 404. The upper surface of the core layer 402 comprises a plurality of cavities 406 in a predetermined pattern configured to scatter incoming sound waves. The decorative top layer 403 comprises a decorative layer 403a and an upper acoustic impedance layer 403b.

[0118] Figure 5A schematic diagram of an optional embodiment of a panel 501 according to the present invention is shown, and in particular a core layer 502 of the panel is shown. The figure shows a top view of the core layer 502. The panel includes a core layer 502, which preferably includes a composite material, the composite material including a mixture of a mineral material and a thermoplastic material. The core layer 502 has an upper surface (shown) and a bottom surface (not shown in the figure). However, the bottom surface can be equivalent to the top surface (upper surface), and therefore a plurality of cavities can also be provided. A portion of the upper surface of the core layer 502 is provided with a plurality of cavities 506. The cavity 506 extends to the bottom surface of the core layer 502. The cavity 506 is an integrally formed cavity 506. In the embodiment shown, the cavity 506 defines a unit pattern, in particular a polygonal unit pattern. The figure shows that the cavity 506 is separated via a separator 507, wherein the thickness of at least a portion of the separator 507 between the cavities 506 is less than the length and / or width of the cavity 506. In the embodiment shown, the cavity 506 is embossed into the upper surface of the core layer 502. The cavity 506 is therefore an embossed cavity 506. The edge of the core layer 502 is substantially free of the cavity. The circumferential edge of the panel is free of the cavity 506 over a predetermined distance X. Preferably, the core layer 502 shown is used in combination with a decorative top layer and a compressible layer according to the present invention.

[0119] Figure 6 A roller 600 is shown which can be used to manufacture a core layer for use in a panel according to the invention. A plurality of cavities can be provided by subjecting at least a portion of the upper surface and / or the bottom surface of the core layer to a (rotational) embossing process. This can for example be done substantially immediately after extrusion of the core layer. For example, it is conceivable that the core layer is guided through at least two rollers 600, wherein at least one of the rollers is provided with a surface structure 661 which is configured to provide a plurality of cavities in at least a portion of the bottom surface of the core layer.

[0120] Figure 7 A perspective view of another alternative embodiment of a floor panel 701 according to the present invention is shown. The panel 701 includes a core layer 702, a decorative top layer 703, and a compressible layer 704. A portion of the upper surface of the core layer 702 includes a plurality of cavities 706 in a predetermined pattern configured to scatter incoming sound waves. The panel 701 also includes a backing layer 708.

[0121] Obviously, the present invention is not limited to the exemplary embodiments shown and described here, but can have numerous variations within the framework of the attached claims, which are obvious to those skilled in the art. In this case, it is conceivable to combine completely or partially different inventive concepts and / or technical measures of the above-mentioned variant embodiments without departing from the inventive concept described in the attached claims.

[0122] The verb “comprise” and its conjugated forms used in this patent document are understood to mean not only “include” but also expressions including “comprises”, “consisting essentially of”, “formed by…” and their conjugated forms.

Claims

1. A panel, comprising: - at least one core layer; - at least one decorative top layer; as well as - at least one compressible layer located between the core layer and the decorative top layer; Wherein, at least a portion of the upper surface of the core layer and / or at least a portion of the lower surface of the core layer comprises a plurality of cavities.

2. The panel according to claim 1, wherein The compression layer has a Shore A hardness of 75 or less.

3. A panel according to claim 1 or claim 2, wherein: The decorative top layer has a flexural strength of 1800 MPa or less.

4. The panel according to claim 1, characterized in that The upper surface of the core layer has a plurality of upward cavities.

5. The panel according to claim 1, characterized in that The lower surface of the core layer has a plurality of cavities facing downwards.

6. The panel according to claim 1, characterized in that A plurality of cavities on the upper surface of the core layer face a first angle; a plurality of cavities on the lower surface of the core layer face a second angle; wherein the first angle is different from the second angle.

7. The panel according to claim 1, wherein The compressible layer comprises a material selected from the group consisting of closed cell foam, open cell foam, a compressible natural material or a compressible elastomer.

8. The panel of claim 1, wherein: The compressible layer has a thickness ranging from 0.8 mm to 4 mm.

9. The panel according to claim 1, wherein The compressible layer comprises at least one intermediate acoustic impedance layer having an acoustic impedance of at most 8 MRayl.

10. The panel of claim 1, wherein: At least a portion of the decorative top layer comprises at least 0.5 wt% of an additive having an acoustic impedance higher than 30 Mrayl.

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