Panels and methods of manufacturing panels

Abstract

The present invention relates to a panel, such as a floor panel, a wall panel, or a ceiling panel, in particular a decorative panel, and to a method for producing such a panel. The panel according to the invention comprises a core layer comprising a first composite material and a second composite material having different material properties. The panel is also provided with a plurality of cavities.

Description

Technical Field

[0001] The invention relates to a panel, in particular a floor panel, a wall panel or a ceiling panel. The invention also relates to a method for producing such a panel. Background Art

[0002] Over the past few years, the market for rigid suspended flooring has seen significant growth, evolving from thin, flexible strips of vinyl or LVT (luxury vinyl tile) to multi-layer, integrated, thick, rigid engineered hybrids characterized by several advantages, such as unprecedented stability under temperature fluctuations, reduced likelihood of print-through or deformation on uneven subfloors, and increased locking strength between panels. This development has led to more rigid floor panels, which typically have a core made of materials such as WPC (wood plastic composite, essentially a foamed PVC core with or without wood particles) and a density of approximately 900 kg / m 3 ) and SPC (Stone Plastic Composite, density of about 2000kg / m 3 Compared to WPC, SPC has better dimensional stability when subjected to temperature fluctuations, which allows for a larger installation surface area and the ability to be installed in hot and crowded areas. Another advantage of solid SPC compared to low-density WPC is its impact resistance and indentation resistance. However, an inherent disadvantage of solid SPC is that its acoustic performance is less than satisfactory. Compared to the more flexible and soft LVT and WPC, solid SPC has poor sound performance. Generally, it can be considered that an increase in the filler or mineral content in the product causes higher rigidity and improved dimensional stability, but leads to poorer acoustic performance. Acoustic performance in the flooring industry is understood as both the reduction in the amplitude of the sound wave when it passes through the floor (the sound propagates to the room below), and the reduction in the amplitude when the reflected walking sound (the sound heard in the same room) is tested. It can be measured using "Delta IIC" (USA) or "Delta

[0003] Lw" (Europe, Australia) test for the reduction of transmitted sound. These two test methods give an indication of the reduction in sound transmission to the room below due to the decorative flooring, or in short, the difference between sound transmission with or without the decorative flooring installed. To improve (reduce) the amplitude of the transmitted sound, an underlayment can be installed between the decorative flooring and the subfloor, or an acoustic underlayment can be bonded to the back of the decorative flooring at the factory. By way of example, it is expected that a 4mm with a 1mm pre-attached EVA backing

[0004] SPC achieves a Delta Lw result of 12 dB; WPC products of the same specifications typically achieve 20 dB. The lower density of WPC can improve sound absorption. Furthermore, due to its relatively low mineral content, WPC is inherently less dimensionally stable than solid SPC. Therefore, there is a need for flooring products that combine the advantages of SPC panels (rigidity, non-print-through, stability, and indentation resistance) with those of WPC panels (lower weight and improved acoustic performance).

[0005] In the prior art, it is known to apply "grooves" to the backside of wood-based or thermoplastic floor panels to improve stability and increase flexibility. These grooves are typically applied by cutting with a saw blade or carving with a tool to remove material. It is also known to apply grooves to extruded thermoplastic floor panels through clever shaping of the extrusion die, through which a single support sheet is extruded, forming "strip-shaped recesses" along the direction of extrusion. Both manufacturing methods result in a bottom surface texture with a linear design. In practice, these panels are characterized by a linear or longitudinal design, in which the boundaries of the cavities applied to the bottom surface of the floor panel are unidirectional in the plane of the bottom surface. Although the applied grooves may have at least one boundary that defines the exit or entry point of the tool used to apply the grooves, at least 90%, typically greater than 95%, and most often greater than 98%, of the entire perimeter of these linear or longitudinal cavities or grooves have linear, parallel boundaries. These longitudinal cavity boundaries form the line between the point of entry into the panel and its exit point. Therefore, typically, the applied grooves are defined by boundaries that primarily face a single direction (equivalent to the direction of the cutting or extrusion process used to apply the grooves). When multiple such grooves are present on the back surface, they are present with primarily linear or longitudinal boundaries that are parallel to each other and face the same direction. Such panels lack the opportunity for acoustic improvement because they do not allow for more complex acoustic designs. Summary of the Invention

[0006] It is an object of the present invention to provide a panel which at least partially offers the advantages of reduced panel weight and which also provides improved acoustic properties.

[0007] Furthermore, the invention provides a panel, such as a floor panel, a wall panel or a ceiling panel, in particular a decorative panel, comprising:

[0008] - at least one core layer, said core layer comprising:

[0009] o at least one upper core layer comprising a first composite material; and

[0010] o at least one lower core layer comprising a second composite material;

[0011] wherein at least a portion of the bottom surface of the lower core layer is provided with a plurality of embossed cavities, and / or wherein the Vicat softening temperature of the upper core layer is at least 15 degrees Celsius higher than the Vicat softening temperature of the lower core layer.

[0012] The panel according to the present invention, wherein at least a portion of the bottom surface of the lower core layer is provided with a plurality of embossed cavities, and wherein the Vicat softening temperature of the upper core layer is at least 15 degrees Celsius higher than that of the lower core layer, thereby providing the panel with improved acoustic performance and reduced weight relative to a substantially solid panel, without compromising the panel's rigidity or indentation resistance. At least the upper core layer of the panel is relatively rigid, which is advantageous compared to flexible panels, as substantially rigid panels facilitate relatively easy handling and / or installation. Furthermore, substantially rigid panels are better suited to smoothing out slight bumps and undulations in the subfloor without transferring them to the surface. This is particularly advantageous for use as floor panels, while the panel's rigidity is also advantageous when the panel is used as wall or ceiling panels. However, as mentioned above, rigid panels typically have unsatisfactory acoustic performance. This disadvantage is overcome by providing at least a portion of the bottom surface of the core layer with a plurality of embossed cavities. The presence of multiple (embossed) cavities in the core layer reduces the amount of material in at least the lower core layer. This can influence the absorption, transmission, reflection, refraction, and / or diffraction of sound waves interacting with the panel. Experiments have found that, according to the present invention, the combination of a composite core layer with cavities provided in at least its lower core layer has a positive effect on the acoustic performance of the panel, achieving a sound damping effect. This is advantageous because it eliminates the need for an additional sound damping layer underneath or on the back of the panel.

[0013] The presence of multiple embossed cavities in at least a portion of the lower core layer of a panel according to the present invention reduces the amount of material present, resulting in a lightweight and durable panel. While the multiple cavities reduce the amount of material in the lower core layer, it has been found that this reduction in material due to the presence of the upper core layer according to the present invention does not negatively impact the dimensional stability of the lower core layer or the core layer as a whole. The presence of multiple cavities in at least a portion of the lower core layer significantly improves the acoustic performance of the panel due to the excellent sound absorption properties of the lower core layer. The cavities positively impact the sound absorption properties of the panel, particularly the lower core layer, by enabling the lower core layer to absorb sound energy when encountering sound waves without reflecting energy that would contribute to unwanted noise. Some of the absorbed energy is converted into heat, and some is transmitted through the multiple cavities in the lower core layer. Furthermore, due to the intended softness of the lower core layer, it acts as a sound and vibration damping layer.

[0014] As mentioned above, the presence of multiple embossed cavities in at least one lower core layer also helps eliminate noise and echoes by improving sound absorption. The multiple cavities are typically configured to scatter sound waves onto different frequencies, which essentially prevents noise by reducing the number of sound reflections and ultimately lowering the level of noise generated within the panel. It is conceivable that at least one cavity, and preferably multiple cavities, have a depth defined by the maximum thickness of the lower core layer. It is also conceivable that at least one cavity, and preferably multiple cavities, have a depth defined by the distance from at least the outer surface of the lower core layer up to the bottom surface of the upper core layer. Because at least one cavity has a depth of at most the thickness of the lower core layer, or at most at the bottom surface of the upper core layer, it has been found that sound waves are functionally disrupted and reflected in multiple directions, thereby diffusing echoes within the panel and improving the panel's acoustic performance. The depth of at least one cavity can vary, as can be observed along at least one cross-sectional direction of the cavity. Furthermore, the presence of multiple cavities in the bottom layer of the panel results in a reduction in material content within at least the panel. This may affect the absorption, transmission, reflection, refraction and / or diffraction of sound waves interacting with the panel.

[0015] The core layer comprises at least one upper core layer comprising a first composite material and at least one lower core layer comprising a second composite material, wherein the Vicat softening temperature of the upper core layer is at least 15 degrees Celsius higher than the Vicat softening temperature of the lower core layer, the core layer being advantageous such that an embossing step applied to provide the embossed cavity does not adversely affect the upper core layer of the core layer. Thus, the embossed cavity can be provided at the bottom surface of the lower core layer by pressure and / or heat without adversely affecting or deforming the upper core layer.

[0016] The core layer may also be referred to as a multi-layer core layer. The core layer may include at least one upper core layer and at least one lower core layer integrally connected. Thus, the core layer may integrally include at least one upper core layer and at least one lower core layer. The upper core layer and the lower core layer may be interconnected. It is also conceivable that the core layer includes multiple upper core layers and / or multiple lower core layers. In the case where the core layer includes more than two layers, it is conceivable that each core layer has different material compositions and / or material properties.

[0017] The material and cavity according to the present invention are characterized by the rigidity of the composite material, which prevents undesirable vibrations and flexibility of the panel during use. This is also positive for the overall performance of the panel during use. An embossed cavity is understood to be a cavity mechanically pressed into the bottom surface of the core layer during manufacturing. This mechanical embossing step is preferably performed when the core layer is sufficiently soft, typically before the core layer is subsequently (further) cured and / or (further) hardened.

[0018] At least a portion of the bottom surface of the core layer, and in particular at least a portion of the bottom surface of the lower core layer, is typically substantially flat. In particular, the bottom surface typically defines a substantially flat surface. When referring to a cavity, the terms recess, opening, and / or depression may also be used. During the manufacturing process, it is advantageous to form a cavity, typically as a localized depression, in the flat back side of the core layer immediately after extrusion and / or during hot pressing and / or just before the curing of the composite material or composite materials forming the core layer or layers of the panel. The panels are typically waterproof panels. Due to their good acoustic properties, the panels may also be referred to as acoustic panels.

[0019] The Vicat softening temperature is an indicator of the softening of composite materials, particularly polymer composite materials, at high temperatures. While the Vicat softening temperature of the upper core layer is expressed as being at least 15 degrees Celsius higher than the Vicat softening temperature of the lower core layer, this can also be expressed as the Vicat softening temperature of the first composite material being at least 15 degrees Celsius higher than the Vicat softening temperature of the second composite material. Preferably, the Vicat softening temperature of the upper core layer is at least 20 degrees Celsius higher than the Vicat softening temperature of the lower core layer, more preferably at least 25 degrees Celsius higher. The present invention particularly relates to a panel in which there is a difference of at least 15 degrees Celsius between the Vicat softening temperatures of the upper and lower core layers, wherein preferably, the Vicat softening temperature of the lower core layer is lower than that of the upper core layer. Within the indicated deviation range, it is industrially feasible to apply the embossing cavity to the bottom surface of the lower core layer by means of pressure and / or heat without adversely affecting or deforming the upper core layer.

[0020] Preferably, the lower core layer and / or the second composite material has a Vicat softening temperature of at least 50 degrees Celsius. The Vicat softening temperature range of the lower core layer may be, for example, in the range of 50 degrees Celsius to 90 degrees Celsius. Experiments have found that within this range, the lower core layer can be thermoformed into a desired shape at a temperature above its Vicat softening temperature. Since the Vicat softening temperature of the upper core layer is at least 15 degrees Celsius higher, the upper core portion will be able to withstand deformation under the effects of pressure and heat applied to the lower core layer. It is conceivable that the Vicat softening temperature of the upper core layer and / or the first composite material is at least 95 degrees Celsius.

[0021] The panel according to the present invention can be substantially rectangular, but can also be substantially rhombus-shaped or substantially polygonal. In a preferred embodiment, the flexibility of the panel in the longitudinal direction is substantially equal to the flexibility of the panel in the transverse direction. For example, in the case of a substantially square or approximately square panel, it is also conceivable that the flexibility of the panel in the first direction is substantially equal to the flexibility in the second direction, wherein the first and second directions are defined in the same plane, and wherein the directional component of the first direction is substantially perpendicular to the directional component of the second direction. Substantially equal means that the average measured deviation between the longitudinal and transverse directions is within 10%, and preferably within 5%. The advantage of this embodiment is that a relatively rigid and stable panel can be obtained. The cavity is preferably arranged so that the flexibility of the panel is not significantly affected, particularly in at least one direction so that the flexibility of the panel is not significantly affected, and the flexibility of the panel in a single direction can be not significantly affected. For example, it is conceivable that the cavity is arranged so that it does not affect the flexibility in the first direction, the first direction being, for example, (but not limited to) the longitudinal direction.

[0022] In a further preferred embodiment, the elastic modulus of the lower core layer is at most 50% of the elastic modulus of the upper core layer. This means that the upper core layer is substantially more rigid than the lower core layer. This is beneficial for sound attenuation and the acoustic performance of the panel itself. In particular, when tested according to EN310, the elastic modulus of the upper core layer may (for example) be at least 3500 MPa. The elastic modulus of the at least one lower core layer of the panel according to the invention may be at most 1750 MPa, preferably at most 1050 MPa, even more preferably at most 525 MPa. Therefore, when subjected to stress, the at least one lower core layer exhibits a significantly reduced resistance to non-permanent deformation compared to the core layer. Therefore, the panel of the present invention exhibits both the rigidity brought about by the upper core layer and the deformability of the at least one lower core layer. It has been found through experiments that due to this combination of a substantially rigid upper core layer and a substantially flexible lower core layer, the acoustic performance of the panel is positively influenced while also maintaining the dimensional stability of the panel. It has been observed that this combination of core layers having a rigid (upper) core layer and a flexible (lower) core layer enhances the sound absorption of the panel by attenuating vibrations imparted thereto. Furthermore, it has been observed that this combination of a multilayer core layer having rigid and flexible core layers substantially reduces the amplitude of vibration energy imparted in the panel, thereby also reducing unwanted noise.

[0023] The panel itself preferably has a modulus of rigidity of at least 2500 MPa. In a further preferred embodiment, the modulus of rigidity of the panel in the longitudinal direction is at least 2500 MPa, and / or the modulus of rigidity of the panel in the transverse direction is at least 2500 MPa, when measured according to the EN310 standard. Thus, the substructure of the core layer of the panel according to the present invention has a positive impact on the stability, pressure distribution, and strength of the panel in both the longitudinal and transverse directions. This represents a significant improvement over the prior art, which suffers from a reduced modulus of rigidity in a direction perpendicular to the recesses or grooves formed by the subtractive manufacturing process.

[0024] The upper core layer, and in particular its upper surface, may have a Shore D hardness in the range of 85 to 95. The lower core layer, and in particular its upper surface, may have a Shore D hardness in the range of 55 to 65. The hardness of one or more core layers can be measured, for example, using a durometer. In this method, higher Shore D values ​​correspond to higher hardness. Hardness indicates the ability of a test material to deform locally at a pressure point when a perpendicular force is applied to the surface. Since impact noise is generated by the impact of a hard object, such as a shoe heel, chair, or smartphone, on a hard surface, the amplitude and pitch of the noise generated increases with a harder surface, and conversely, the amplitude and pitch of the noise generated decreases with a softer surface or object. The combination of an upper core layer having a higher hardness than a lower core layer has a positive impact on the acoustic performance of the panel. The Shore D hardness range for the upper core layer has a positive impact on the attenuation of the generated sound, while the Shore D hardness range for the lower core layer has a positive impact on the reduction of the generated sound.

[0025] The first composite material differs at least partially from the second composite material in terms of composition. However, the first composite material and the second composite material may comprise at least some similar basic materials. Each composite material may, for example, comprise at least one mineral material and at least one adhesive. The upper core layer may comprise at least one adhesive, wherein the ratio of the weight percentage of mineral material relative to the adhesive is preferably at least 1. It is also conceivable that the lower core layer comprises at least one adhesive, wherein the ratio of the weight percentage of mineral material relative to the adhesive is at least 1. In an advantageous embodiment, the adhesive of the first composite material of the upper core layer is similar to the adhesive of the second composite material of the lower core layer. This embodiment is advantageous because it allows efficient thermoforming. The at least one first composite material and / or the at least one second composite material may, for example, comprise thermoplastic and / or thermosetting materials, and preferably comprise mineral materials.

[0026] Preferably, the mineral content of the first composite material is at least 50% higher than the binder or thermoplastic material content. In a preferred embodiment, the mineral content of the first composite material is at least 40% by weight, preferably at least 50% by weight, and more preferably at least 60% by weight. This mineral content creates a relatively rigid core layer, and therefore a relatively rigid panel. Considering panels with a core layer made of a polymer material, the presence of an upper core layer containing at least 40% by weight of a mineral material contributes to the increased rigidity of the panel. Compared to relatively flexible panels, substantially rigid panels are more suitable for smoothing out slight bumps and / or undulations in the subfloor without transferring them to the panel surface. It is also conceivable that the mineral content of the second composite material is at most 60% by weight, preferably at most 50% by weight, and more preferably at most 30% by weight. Preferably, the mineral content of the second composite material is lower than that of the first composite material, particularly at least 50% lower, preferably at least 60% lower, and more preferably at least 70% lower. The mineral content ranges in the first and / or second composite materials positively contribute to the Shore D hardness of the core layer. The mineral content of the at least one lower core layer and its difference from the mineral content of the upper core layer impart flexibility to the at least one lower core layer. It is conceivable according to the invention that the core layer comprises an increased mineral content in a ratio of at least 3:1 to the thermoplastic plastic of the core. The upper core layer may also comprise up to 80% by weight of mineral material. A higher mineral content generally results in a greater rigidity of the panel. Furthermore, due to the relatively large amount of mineral material and the relatively small amount of thermoplastic material in the composite core layer, significantly improved temperature resistance can be achieved, in particular compared to conventional floor panels having a core predominantly based on PVC. The panels according to the invention generally do not suffer from undesired shrinkage and expansion due to seasonal and / or local temperature variations.

[0027] The core layer, and in particular the upper core layer and / or the lower core layer, may also comprise at least one Vicat modifier. Non-limiting examples of available Vicat modifiers are ASA (polyacrylonitrile-styrene-acrylate), ABS, thermosetting systems, epoxy systems, etc. Adding any of the Vicat modifiers generally increases the Vicat softening temperature of the core layer to which the modifier is applied. Therefore, a Vicat modifier may also be used to increase the difference in Vicat softening temperature between the upper core layer and the lower core layer.

[0028] The first composite material and / or the second composite material may include at least one selected from the group consisting of the following mineral materials: magnesium oxide (MgO), magnesium chloride (MgCl2), magnesium oxysulfate, calcium carbonate (CaCO3), chalk, clay, calcium silicate and / or talc. These materials have been shown to impart sufficient rigidity to the composite material. As another non-limiting example, limestone (e.g., calcium carbonate and magnesium carbonate) may be used as the mineral material in the upper core layer and / or the lower core layer. The mineral material may be present as a particulate mineral filler.

[0029] Typically, the upper and / or lower core layers of the core layer of the panel according to the present invention are composed of a composite material comprising a mixture of a mineral material and a thermoplastic material. Non-limiting examples of thermoplastic materials include polyvinyl chloride (PVC), polyethylene (PE), polyurethane (PU), acrylonitrile butadiene styrene copolymer (ABS), and / or polypropylene (PP). For example, it is conceivable that the first composite material and / or the second composite material comprises at least one thermoplastic material selected from the group consisting of polyvinyl chloride (PVC), polystyrene (PS), polyethylene (PE), polyurethane (PU), acrylonitrile butadiene styrene copolymer (ABS), polypropylene (PP), phenolic resin, melamine formaldehyde resin, or a combination thereof. The thermoplastic material may also be a thermoplastic material containing vinyl. The core layer may also comprise a mixture of the above materials. Typically, the weight percentage ratio of the mineral material to the thermoplastic material is at least 1. Preferably, the first composite material comprises at least 15% by weight of thermoplastic material. The second composite material preferably comprises at least 30% by weight of thermoplastic material. The first composite material preferably comprises at most 40% by weight of thermoplastic material. The second composite material preferably comprises at most 65% by weight of thermoplastic material. The composition of the first and second composite materials has an influence on the stiffness of the core layer itself and on the temperature resistance of the individual core layers.

[0030] The core layer, and in particular the upper and / or lower core layers, may further comprise at least one additive selected from the group consisting of a pigment, an impact modifier, a lubricant, a stabilizer, a wax, and / or a processing aid. Various pigments, such as inks, impart color to the first and / or second composite materials. When pigments are used, the pigment is typically present in the composite material in an amount of 0% to 5% by weight. It is also conceivable that the first and / or second composite materials comprise an organic or inorganic binder. As impact modifiers, MBS (methacrylate-butadiene-styrene copolymer), CPVC (chlorinated PVC), ABS (acrylonitrile butadiene styrene copolymer), or TPE (thermoplastic elastomer) are preferably used, with the impact modifier more preferably being present in the composite core layer in an amount of 0% to 5% by weight. In addition, at least one lubricant may be present, and more preferably an internal lubricant and an external lubricant. Optional stabilizers may be selected to work in conjunction with the specific polymer used, and may, for example, be calcium zinc stabilizers. Preferably, the total amount of additives present in the composite core layer is limited to 1 wt % to 15 wt %, more preferably 5 wt % to 15 wt %, and most preferably 8 wt % to 12 wt %. In one possible embodiment, the core layer is substantially free of natural organic fibers, and in particular substantially free of wood (e.g., wood fibers, including sawdust and bamboo chips).

[0031] The transition temperature of the lower core layer is preferably at least 10 degrees Celsius lower than the transition temperature of the upper core layer. The temperature difference between the respective transition temperatures of the upper core layer and the lower core layer fundamentally deforms the lower core layer and enables the formation of multiple embossing cavities during manufacture while ensuring that the form and / or shape of the upper core layer remains substantially intact. Preferably, the upper core layer and the lower core layer are extruded layers formed via an extrusion process. The core layer can be formed by co-extruding at least one upper core layer and at least one lower core layer. Therefore, at least one upper core layer and at least one lower core layer can be formed via co-extrusion. Alternatively, the upper core layer and / or the lower core layer can be a calendering layer formed via a calendering process, or a solidified layer formed via a curing process or a hot pressing process. The upper core layer and the lower core layer can also be extruded and subsequently laminated under heat and pressure. Alternatively, the upper core layer and the lower core layer can be connected via at least one adhesive layer and / or glue layer. Preferably, the upper core layer and the lower core layer are interconnected.

[0032] It is conceivable that the core layer, and in particular the upper and lower core layers, are extruded layers formed via an extrusion process. The advantage of forming the core layer via an extrusion process is that the panel can be manufactured relatively inexpensively. Furthermore, it has been found that extruded core layers are advantageous in terms of the rigidity achieved and, when applied, are able to form a fusion bond with the top layer. In this context, the extrusion and fusion processes can be performed simultaneously during the manufacture of the panel. It is particularly advantageous if the cavity in the lower core layer is formed immediately after the extrusion process, before or during lamination with the decorative layer. This prevents material from being removed from the core after the panel is manufactured. Thus, the panel can be manufactured more efficiently. Furthermore, the formation of residual material is prevented. It is also conceivable that the cavity is formed substantially immediately after the extrusion process or during the coextrusion process to manufacture the upper and lower core layers. In this case, this means forming the cavity before the core solidifies. Thus, this refers to forming the cavity on the back side of the lower core layer when the (second) composite material has a ductile consistency or viscosity, rather than being rigid.

[0033] In another possible embodiment, it is conceivable to form the core layer via hot pressing. For this technology, the cavity can be formed during manufacturing and / or can be provided after the panel is manufactured. Hot pressing can have a positive contribution to the rigidity of the panel. It is also conceivable to form the core layer via a curing process. Therefore, this means that the cavity is formed on the back side of the core when the core has a ductile consistency or viscosity and is therefore not rigid. It is conceivable to form the cavity on the back side of the core by an imprinting process, preferably by rotary imprinting. It is also conceivable to form at least one cavity on the back side by other methods, such as heating and / or pressing processes, etching, milling, engraving, stamping, molding, subtractive manufacturing, additive manufacturing or a combination thereof.

[0034] Optionally, the panel may include at least one reinforcement layer. Non-limiting examples of such reinforcement layers are fiberglass, polypropylene, jute, cotton, and / or polyethylene terephthalate. It is particularly advantageous if the reinforcement layer is at least partially impregnated with a thermosetting resin. Such thermosetting resins may be selected from the group consisting of melamine formaldehyde resins, phenolic resins, and / or urea formaldehyde. Typically, when reinforcement layers are applied, they are present near the top and / or bottom surfaces of the panel. Preferably, when reinforcement layers are applied, they are attached to the core layer.

[0035] Preferably, the density of the lower core layer is lower than the density of the upper core layer. Preferably, the density of the upper core layer is at least 1900 kg / m 3 It is conceivable that the density of the upper core layer and / or the lower core layer is 1900 kg / m 3 Up to 2100kg / m 3 However, it is also conceivable that the density of the lower core layer is lower than 1900 kg / m 3 The density of the lower core layer can be (for example) 900 kg / m 3 Up to 1700kg / m 3 The core layer may also have a density gradient across the core layer.

[0036] It is contemplated that embodiments of the panel according to the present invention may include a lower core layer that is at least partially foamed. In other possible embodiments, both the upper and lower core layers are at least partially foamed. The upper and / or lower core layers may, for example, be a closed-cell foam material and / or an open-cell foam material.

[0037] It is conceivable that the boundaries of the embossed cavities are multidirectional in the plane of the bottom surface of the lower core layer. Therefore, panels according to the present invention can benefit from the presence of cavities whose boundaries are multidirectional in the plane of the bottom surface of the core layer. Typically, floors are subject to a wide range of sound waves, such as footsteps, the sound of televisions or radios, conversations, the sound of babies crying, and noises caused by falling objects. Because sound waves are vibrations that easily propagate in a solid, straight path, floor panels without any geometric shapes on the bottom surface have a very narrow band of sound wavelength attenuation. To improve sound attenuation, vibrations can be stopped or absorbed, or directed in another direction to dissipate the sound waves. The presence of cavities on the back of the panel creates an additional surface for shock waves to propagate through. Panels with grooves on the bottom surface are expected to perform slightly better than panels without any geometric shapes, but they still only attenuate a very limited wavelength band because they can only dissipate sound in one direction. The panels of the present invention significantly improve this by providing floor panels with a multi-layer core that are able to attenuate sound waves due to the presence of embossed cavities in the lower core layer that dissipate sound waves in multiple directions, thereby significantly increasing the sound absorption surface area. To this end, when the cavities have multi-directional boundaries, they significantly improve upon existing technologies that only have unidirectional dissipation.

[0038] Panels according to the present invention can include and benefit from cavities specifically sized to attenuate sound waves of a certain frequency. Multiple cavities of varying sizes, specifically designed to increase the frequency band of attenuated wavelengths, can be used. Furthermore, embossed cavities typically have sharp boundaries. Because they have sharp boundaries, they also function as attenuation chambers. This significantly improves upon existing technologies, where strip-shaped recesses or grooves fail to optimally attenuate frequencies. Cavities according to the present invention can be "tuned" by forming them with appropriate length, width, and depth dimensions to provide passive sound cancellation through resonance. Consequently, cavities can be present in various combinations of shapes, lengths, widths, and depths, and thus in various sizes, to provide optimal sound cancellation. Preferably, at least one dimension of the cavity is approximately 1 / 5 to 1 / 3, more preferably approximately 1 / 4, of the wavelength of the target frequency to be attenuated, thereby forming a resonant chamber that, based on empirical testing, optimally absorbs the target frequency. The target cavity dimensions can then be calculated using the formula "wavelength = sound speed / frequency." The target frequencies are those that cause the greatest range of noise in residential applications, particularly high-pitched noise that propagates to rooms below when walking on the floor surface, and are in the range of 1,000 Hz to 25,000 Hz, more preferably 4,000 Hz to 20,000 Hz, and most preferably 8,000 Hz to 16,000 Hz. For example, at least some of the cavities can be configured to attenuate sound, preferably in the frequency range of 20 Hz to 25,000 Hz, preferably 2,000 Hz to 20,000 Hz, and most preferably 8,000 Hz to 16,000 Hz. It is also contemplated that at least some of the cavities can be configured to attenuate sound in the frequency range of preferably 500 Hz to 10,000 Hz. The maximum length and / or maximum width of at least some of the cavities can range from 2 mm to 15 mm, most preferably 5 mm to 10 mm. Based on the above formula, it has been found that the dimensions of a cavity for floor noise attenuation in residential and commercial buildings can range from 2 mm to 15 mm in width and / or length in the plane of the back surface, most preferably from 5 mm to 10 mm. Empirically, the optimal volume for floor noise attenuation in residential and commercial buildings has been found to be in the range of 5 cubic millimeters to 2 cubic centimeters, more preferably from 0.1 cubic centimeters to 0.6 cubic centimeters. This typically results in an average reduction in sound amplitude of at least 4 dB compared to a single direction and an average reduction of at least 5 dB compared to solid floor panels. It is also conceivable that at least some of the cavities may have different volumes to attenuate different target frequencies.

[0039] At least one cavity may have, and preferably a plurality of cavities may have, a maximum width W and a maximum length L, wherein the ratio between the maximum width W and the maximum length L is between 0.2 and 1, preferably between 0.5 and 1. The depth of at least one cavity may be observed in at least one cross-sectional direction of the cavity. It is also conceivable that the depth of at least some cavities lies between 10% and 30% of the maximum thickness of the core layer. It is also conceivable that the depth of at least some cavities lies between 10% and 30% of the maximum thickness of the lower core layer.

[0040] The panels according to the present invention can, for example, be substantially longitudinal panels. This is particularly advantageous when the panels are used as floor panels. However, it is also conceivable that the panels are substantially rectangular, rhombus-shaped, or polygonal. The panels can be rectangular panels defining a first longitudinal direction, wherein at least some of the cavities have an elongated shape defining a second longitudinal direction, wherein the first and second longitudinal directions enclose an angle with each other, preferably within the range of 30 to 90 degrees.

[0041] A plurality of embossed cavities can exist in a predetermined pattern. The cavity can, for example, extend from the first distal end of the panel to the second distal end of the panel. In this embodiment, the first distal end is generally opposite to the second distal end. It is also conceivable that the cavity is arranged at a predetermined distance from the edge of the panel. For example, it is conceivable that the cavity does not extend through the (outer) edge of the panel. Therefore, the cavity can be arranged substantially in the center. It is found that this is conducive to the sound absorption characteristics of the panel. This embodiment also ensures that the stability and flexibility of the panel will not be negatively affected by the cavity because there is a pull-back strength provided by the bottommost surface formed in this way. A non-limiting example of a predetermined pattern is, for example, a zigzag pattern. It is also conceivable that a plurality of embossed cavities include a repeated cavity pattern. It is also conceivable that at least part of the cavity defines a cell pattern and / or a grid pattern.

[0042] In a preferred embodiment of the panel, at least a portion of the bottom surface of the core layer is provided with a plurality of embossed cavities. For example, such cavities can be provided so that the (predetermined) pattern of cavities influences the acoustic properties, and in particular the sound damping properties, of the panel. For such an embodiment, the cavities typically extend in at least two directions within the same (horizontal) plane. Considering that the cavities extend in the y-direction from the bottom surface of the core layer toward the top surface, these at least two directions can be (for example) the x-direction and the z-direction. For example, the cavities can extend in at least two directions within the plane defined by the bottom surface of the lower core layer. In the case of a substantially longitudinal panel, the cavities can be arranged to extend in directions other than the longitudinal direction of the panel. For example, it is conceivable that the cavities extend in a combination of longitudinal and transverse directions. It is also conceivable that some or all of the cavities are substantially centered within the panel and / or do not extend to the (outer) edges of the panel. It is also conceivable that the cavities are arranged at a predetermined distance from each other. The cavities can also form a network of interconnected cavities. This embodiment can be particularly advantageous because sound waves can pass through such interconnected cavities through which sound propagates. Sound waves can lose their energy through friction with air particles and the walls of the cavity through which the sound waves pass.

[0043] Preferably, the upper core layer is substantially solid. The upper core layer may be free of a cavity. However, it is also conceivable that at least a portion of the cavity provided in the bottom surface of the lower core layer extends into a portion of the upper core layer. The upper region of the upper core layer is preferably substantially solid. Advantageously, the depth of the cavity is at least 20% of the total thickness of the core layer. For the depth of the cavity, a distance measured in the same spatial direction as the thickness of the core layer is taken into account. Typically, in the assembled state of the panels forming the floor covering, both the thickness of the panels and the depth of the cavity can be determined in the vertical direction. The depth of the cavity can also be at least 30% of the total thickness of the core layer and / or the panels. Preferably, the depth of the cavity is not greater than 55% of the total thickness of the core layer. A depth of the cavity of not more than 55% of the total thickness of the core layer prevents deflection of the core layer when pressure is applied to the panels.

[0044] It is contemplated that adjacent cavities are separated by at least one dividing wall, thereby forming an integral part of the core layer, wherein the thickness of the dividing wall is preferably less than 50%, more preferably less than 20%, of the maximum width W of each adjacent cavity. The at least one dividing wall can be multi-directional in the plane defined by the bottom surface of the lower core layer. The bottom surface of the lower core layer can be composed of an embossed portion formed by the plurality of embossed cavities and a remaining unembossed portion, wherein the area occupied by the embossed portion covers at least 50%, preferably at least 70%, of the surface area of ​​the bottom surface of the lower core layer.

[0045] The thickness of the upper core layer can be substantially equal to the thickness of the lower core layer. However, it is also conceivable that the thickness of the upper core layer is greater than the thickness of the lower core layer, and vice versa. In one possible embodiment, the upper core layer is thicker than the lower core layer, in particular, the thickness of the upper core layer is at least 50%, more preferably at least 100%, and even more preferably at least 150% greater than the thickness of the lower core layer. The thickness of the upper core layer can be (for example) at least 3 mm. For example, the thickness of the upper core layer can be between 3 mm and 9 mm, preferably between 4 mm and 5.5 mm or between 5.5 mm and 7 mm. The thickness of the lower core layer can be (for example) at least 0.1 mm. For example, the thickness of the bottom layer can be between 0.1 mm and 2.5 mm. The thickness of the lower core layer can also be between 0.5 mm and 5 mm, in particular between 2.5 mm and 4 mm. In another embodiment, the lower core layer can be thicker than the upper core layer, in particular, the thickness of the lower core layer is at least 30%, more preferably at least 50%, and even more preferably at least 90% greater than the thickness of the upper core layer. The thickness of the lower core layer can be (for example) at least 4 mm. For example, the thickness of the lower core layer can be between about 4 mm and 7 mm. The thickness of the upper core layer can, for example, be at least 1.5 mm. For example, the thickness of the core layer can be between 1.5 mm and 4 mm, preferably between 2 mm and 3.5 mm or between 2.5 mm and 3.5 mm. Due to the combination of rigidity and sound absorption properties of the panels according to the present invention, relatively thin panels can be used. The thickness of the panels can be less than 3.5 cm, more preferably less than 2.75 cm. For example, the thickness of the panels can be between 0.5 cm and 3 cm, preferably between 0.7 cm and 2.5 cm. This thickness is substantially less than the thickness of conventional acoustic (wall, floor or ceiling) panels.

[0046] In a further preferred embodiment, the flat surface area of ​​the bottom surface of the core layer is at least 30% smaller than the flat surface area of ​​the top surface of the core layer. Experiments have found that this difference further contributes to the acoustic performance of the panel while not affecting the rigidity and / or stability of the panel. The top surface of the upper core layer is typically substantially flat and free of cavities.

[0047] The cavity can have a substantially curvilinear geometric cross-section. This can be a cross-section of the panel viewed perpendicular to the plane defined by the bottom surface of the lower core layer. This can also facilitate the desired absorption, transmission, reflection, refraction, and / or diffraction of sound waves interacting with the panel. The cavity can also have a substantially curvilinear geometric shape within the plane defined by the bottom surface of the lower core layer. Such a shape can also facilitate sound distribution within the material. It is also conceivable that a portion of the lower core layer surrounding the cavity has a structured surface. For example, the surface of the lower core layer surrounding the cavity can be at least partially structured. This can also be a profiled or roughened surface. Therefore, the lower core layer can preferably be partially provided with a profiled surface near or in the area defining the cavity. It is also conceivable that at least a portion of the embossed cavity is substantially cylindrical, pyramidal, and / or conical. For example, at least a portion of the cavity can be formed by a substantially semi-cylinder, particularly in the plane of the bottom surface. The depth of the cavity can vary with the length and / or width of the cavity. In particular, the shape of the cavities is selected to enhance the dissipation of impact and / or airborne sound by the cavities. Preferably, the geometry of at least one cavity, and preferably all cavities, in the bottom surface of the lower core layer does not introduce differences in the longitudinal or transverse flexibility of the floor panel. Thus, the geometry of the cavities is selected so that they do not adversely affect the rigidity of the panel. Preferred shapes for the embossed cavities include at least one selected from the group consisting of polygons, curves, and / or combinations thereof. This includes honeycombs, herringbone patterns, waffles, wavy patterns, crisscross patterns, grids, radial patterns, weave patterns, or repeating patterns of polygons (triangles, quadrilaterals, pentagons, hexagons, heptagons, octagons, nonagons, or N-gons, where N is greater than 10), quadrilaterals (squares, rectangles, trapezoids, rhombuses, parallelograms, cubes, etc.), ellipses, trefoil shapes, quadrilaterals, circles, semicircles, curves, or combinations thereof, or circumscribed, inscribed, or random patterns of the aforementioned shapes and patterns. Other preferred designs for the embossed cavity include triangular wedges, egg-dish designs, alternating horizontal and vertical ridges, parametric acoustic surfaces, offset pyramids or pyramids with polygonal bases (triangles, quadrilaterals, pentagons, hexagons, heptagons, octagons, nonagons, or N-gons, where N>10), radial designs, or a series of holes or slots with varying depths.

[0048] The core layer of the panel according to the present invention may comprise at least one pair of opposite (side) edges, said pair of opposite (side) edges comprising complementary coupling components configured for mutual coupling of adjacent panels. The coupling components may form a part of the core layer. Therefore, it is conceivable that both the upper core layer and / or the lower core layer are provided with a part of said coupling components. The coupling components of the panel may be, for example, interlocking coupling components, which are preferably configured to provide horizontal and vertical locking. Interlocking coupling components are coupling components that require elastic deformation, clicking or movement in multiple directions to couple or decouple components to each other. Any suitable interlocking coupling components known in the art may be applied. One non-limiting example is an embodiment in which a first edge of the first pair of opposing edges includes a first coupling component, and wherein a second edge of the first pair of opposing edges includes a complementary second coupling component, the coupling components enabling the plurality of panels to be coupled to one another; wherein the first coupling component comprises a lateral tongue extending in a direction substantially parallel to a plane defined by the panels, and wherein the second coupling component comprises a groove configured to receive at least a portion of the lateral tongue of another panel, the groove being defined by an upper lip and a lower lip. It is contemplated that the complementary coupling components require a downward shearing motion when engaged, or lock together by horizontal movement. It is also contemplated that the interconnecting coupling components comprise a tongue and a groove, wherein the tongue is provided on one side edge of a pair of opposing side edges, and the groove is provided on the other side edge of the same pair of opposing side edges, or on a side of the same pair of opposing side edges adjacent to the tongue. Such coupling mechanism designs are well known in the art and have proven well-suited for use with panels for floor coverings, such as floating floors. In other embodiments, the interconnected coupling component can have an interlocking feature that prevents any free movement (activity) of the interconnected panels. This interlocking feature can be a projection and a corresponding recess arranged on the corresponding opposite side edges, and adjacent panels are interlocked with each other by the projection and recess. It is conceivable that a reinforcement is provided in the interlocking coupling component to improve strength and prevent it from being damaged during the installation of the panel. For example, the complementary or interlocking coupling component can be strengthened with the following materials, such as (but not limited to) glass fiber mesh, reinforcing sheet, carbon fiber, carbon nanotube, ceramic, glass, metal or non-metallic rod array or a polymer compound formed as a whole in the core layer. It is also conceivable that a reinforcement coating of micron or nanotechnology is added to the surface of the interlocking coupling component. The panel according to the present invention and / or the panel obtained via the method according to the present invention is suitable for floor, wall or ceiling coverings preferably characterized by a locking mechanism. In this way, the "suspended" covering can be assembled by interconnecting each panel at all four edges without the need for adhesive.

[0049] It is conceivable that the panel includes at least one backing layer, preferably attached to the bottom surface of the lower core layer. The backing layer can provide a protective function for the core layer, particularly the lower core layer, and thus for the panel itself. The backing layer can, for example, include an adhesive layer. This can enable gluing and installation of the panel according to the present invention. It is also conceivable that the backing layer is a balancing layer, preferably configured to stabilize and / or protect the panel. The balancing layer can, for example, prevent the panel from cupping, warping, and / or bending. The balancing layer can also be referred to as a stabilizing layer. It is also conceivable that at least one balancing layer is attached to the top surface of the core layer. The panel can include a first balancing layer attached to the top surface of the core layer and a second balancing layer attached to the bottom surface of the core layer. The balancing layer can comprise lignocellulose and a cured resin. The backing layer can be substantially free of a cavity. In this embodiment, the bottom surface of the core layer has a cavity, and the backing layer substantially completely covers the bottom surface of the core layer. As a result, the backing layer can substantially seal the embossed cavity. However, it is also conceivable that the cavity extends from the backing layer to the core layer. Therefore, the shape of the cavity of the backing layer can follow or be substantially identical to the shape of the cavity of the bottom surface of the core layer. In either case, since the backing layer can have sound damping properties, the presence of the backing layer can further contribute to the acoustic performance of the panel and / or contribute to the ease of installation of the panel. In addition, the backing layer can form a moisture barrier. The backing layer is typically made of a polymer material, such as (but not limited to) polyurethane. It is also conceivable that the panel includes a combination of any of the examples of possible backing layers listed. In addition, the backing layer can also be a sound-absorbing layer. Such sound-absorbing backing layers can further contribute to the good acoustic properties of the panel. Such backing layers can also be referred to as acoustic layers. The backing layer can be composed of a foam layer of ethylene-vinyl acetate copolymer (EVA), radiation-crosslinked polyethylene (IXPE), expanded polypropylene (XPP) and / or expanded polystyrene (XPS), preferably composed of a low-density foam layer. However, it is also conceivable that the backing layer comprises non-woven fibers, such as natural fibers such as hemp or cork; and / or recycled / recyclable materials, such as PET. When a backing layer is used, the density of the backing layer is preferably 65 kg / m 3 and 300kg / m 3 between, most preferably between 80kg / m 3 and 150kg / m 3 between.

[0050] In a further preferred embodiment, the embossed cavity may be at least partially filled with a filling material, such as a sound-absorbing material and / or a sound-insulating material. This can further contribute to the sound absorption properties of the panel, thereby contributing to the acoustic properties of the panel. The sound-absorbing material may, for example, be a natural material such as bamboo fiber, coconut fiber, and / or cork. Other non-limiting examples of sound-absorbing materials that can be used in the present invention are mineral wool, fiberglass, RPET felt, EVA, PE foam, PP foam, and / or polystyrene foam. In other possible embodiments, the cavity may be substantially completely filled with the sound-absorbing material. In other possible embodiments, the sound-absorbing material may cover at least a portion of the back surface of the panel, thereby forming an additional sound attenuation barrier. It is conceivable that the sound-absorbing material includes vibrators and / or barriers of varying densities. It is conceivable that such an attenuation barrier is characterized by a spatially varying density capable of absorbing different wavelengths. The sound-absorbing material may form an interlocking structure with the cavity present in the bottom surface of the panel, thereby forming a structure that is opposite to the embossed cavity present in the bottom surface of the lower core layer.

[0051] The panel according to the present invention may also include at least one top layer, preferably a decorative top layer. Such a decorative top layer may be, for example, a high-pressure laminate (HPL), a plurality of impregnated layers comprising lignocellulose, a wood veneer, a thermoplastic layer comprising at least one decorative layer and an optional protective top layer, a stone veneer, and / or a combination of such decorative layers. The decorative top layer may also include at least one cellulose-based layer and a cured resin, wherein the cellulose-based layer is preferably paper or kraft paper. The cellulose-based material layer may also be a veneer layer bonded to the top surface of the core layer. The veneer layer is preferably selected from the group consisting of wood veneer, cork veneer, bamboo veneer, and the like. Other decorative top layers contemplated according to the present invention include ceramic tile or porcelain, real stone veneer, rubber veneer, decorative plastic or vinyl, linoleum, and decorative thermoplastic films or foils that may be laminated with a wear layer and an optional coating. Examples of thermoplastics include PP, PET, PVC, and the like. An optional primer may also be provided on the top-facing surface of the upper core layer and printed with the desired visual effect using a direct printing process. It is acceptable to further process the decorative layer with a thermosetting varnish or paint such as polyurethane, PUR or melamine-based resin. It is also conceivable that the panel includes a top layer consisting of ceramic tiles. Such tiles can be attached to the top surface of the core layer, for example, by an adhesive (such as, but not limited to, polyurethane). It is also conceivable that the top layer is made of ceramic material and / or stone. Therefore, the present invention also relates to a panel, in particular a floor panel, a wall panel or a ceiling panel, comprising at least one core layer, the core layers comprising at least one upper core layer comprising a first composite material and at least one lower core layer comprising a second composite material, wherein at least a portion of the bottom surface of the lower core layer is provided with a plurality of embossed cavities, the Vicat softening temperature of the upper core layer being at least 15 degrees Celsius higher than the Vicat softening temperature of the lower core layer, and wherein the panel includes at least one top layer attached to the top surface of the core layer, the top layer comprising stone and / or ceramic material. Preferably, the top layer is a stone tile and / or ceramic tile. Alternatively, embodiments of the panel falling within the scope of the present invention are those in which the cavity is not an embossed cavity but rather a cavity formed by material removal. It is also conceivable that the cavity is a thermoformed cavity. Another alternative is that the lower core layer does not have an embossed cavity. Alternatively, the Vicat softening temperature of the first composite material differs from the Vicat softening temperature of the second composite material by at least 15 degrees Celsius.

[0052] The present invention also relates to a method for manufacturing a panel, in particular a floor panel, a wall panel or a ceiling panel, preferably a panel according to any embodiment of the present invention, the method comprising the following steps: providing a first composite material, preferably a substantially ductile first composite material; providing a second composite material, wherein the Vicat softening temperature of the first composite material is at least 15°C higher than the Vicat softening temperature of the second composite material, preferably a substantially ductile second composite material; forming a core layer, the core layer comprising an upper core layer comprising the first composite material and a lower core layer comprising the second composite material, wherein the core layer comprises a top surface and a bottom surface; embossing a plurality of cavities in at least a portion of the bottom surface of the core layer, in particular the lower core layer; and hardening and / or curing the core layer.

[0053] The method steps may be consecutive steps. It is also conceivable that some of the method steps are performed substantially simultaneously. The first and / or second composite materials may be any of the materials described for use in the corresponding panels according to the present invention. The Vicat softening temperature of the second composite material is in the range of 50 degrees Celsius to 90 degrees Celsius. The transition temperature of the second composite material may be at least 10 degrees Celsius lower than the transition temperature of the first composite material. Formation of the one or more core layers may be performed, for example, via extrusion. It is conceivable that at least a portion of the cavities may be obtained via rotary engraving and / or rotary (die) cutting. It is also conceivable that the step of providing the cavities is performed by guiding the core layer, or at least the lower core layer, over at least two rollers, at least one of the rollers being provided with a surface structure configured to provide a plurality of cavities in at least a portion of the bottom surface of the core layer, in particular the lower core layer. Alternatively, it is conceivable that the plurality of cavities may be provided by mechanical means such as drilling, punching, etc. It is conceivable that the plurality of cavities may be provided by subjecting at least a portion of the lower core layer to a (rotary) engraving process. This can be done essentially directly after the upper and bottom core layers are extruded, or after the lower core layer is laminated directly onto the bottom surface of the (extruded) upper core layer. The shape and / or size of the cavity can be any of the cavities exemplified for the panel according to the invention. The method may further comprise the steps of providing at least one backing layer and attaching it to the bottom surface of the core layer, and / or providing at least one top layer and attaching it to the top surface of the core layer. The method may further comprise the step of machining at least two edges of the panel with complementary coupling components.

[0054] The present invention will now be described in more detail with reference to the following non-limiting clauses.

[0055] 1. A panel, such as a floor panel, wall panel or ceiling panel, in particular a decorative panel, comprising:

[0056] - at least one core layer, said core layer comprising:

[0057] o at least one upper core layer comprising a first composite material; and

[0058] o at least one lower core layer comprising a second composite material;

[0059] Preferably, at least a portion of the bottom surface of the lower core layer is provided with a plurality of embossed cavities, and / or

[0060] The Vicat softening temperature of the upper core layer is at least 15 degrees Celsius higher than the Vicat softening temperature of the lower core layer.

[0061] 2. The panel according to clause 1, wherein the Vicat softening temperature of the lower core layer is in the range of 50 degrees Celsius to 90 degrees Celsius.

[0062] 3. The panel according to any of the preceding clauses, wherein the modulus of elasticity of the lower core layer is at most 50% of the modulus of elasticity of the upper core layer.

[0063] 4. The panel according to any of the preceding clauses, wherein the modulus of elasticity of the upper core layer is at least 3500 MPa.

[0064] 5. The panel according to any of the preceding clauses, wherein the upper core layer has a Shore D hardness in the range of 85 to 95.

[0065] 6. The panel according to any of the preceding clauses, wherein the Shore D hardness of the lower core layer is in the range of 55 to 65.

[0066] 7. The panel according to any of the preceding clauses, wherein the first composite material comprises at least 40 wt%, preferably at least 50 wt%, more preferably at least 60 wt% of mineral material.

[0067] 8. The panel according to any of the preceding clauses, wherein the second composite material comprises at most 60 wt%, preferably at most 50 wt%, more preferably at most 30 wt% of mineral material.

[0068] 9. The panel according to any of the preceding clauses, wherein the first composite material and / or the second composite material comprises at least one mineral material selected from the group consisting of magnesium oxide, magnesium chloride, magnesium oxysulphate, calcium carbonate, chalk, clay, calcium silicate and / or talc.

[0069] 10. The panel according to any of the preceding clauses, wherein the first composite material and / or the second composite material comprises at least one thermoplastic material selected from the group consisting of polyvinyl chloride, polystyrene, polyethylene, polyurethane, acrylonitrile butadiene styrene copolymer, polypropylene, phenolic resin, melamine formaldehyde resin or a combination thereof.

[0070] 11. The panel according to any of the preceding clauses, wherein the core layer comprises at least one binder, and preferably wherein the ratio of the weight percentage of mineral material to the binder is at least 1.

[0071] 12. The panel according to any of the preceding clauses, wherein the transformation temperature of the lower core layer is at least 10 degrees Celsius lower than the transformation temperature of the upper core layer.

[0072] 13. The panel according to any of the preceding clauses, wherein the upper and lower core layers are formed via coextrusion.

[0073] 14. The panel according to any of the preceding clauses, wherein the cavity is formed during the extrusion process, or substantially immediately after the extrusion process, or by hot pressing, or by a curing process.

[0074] 15. The panel according to any of the preceding clauses, wherein the plurality of embossed cavities defines a repeating cavity pattern.

[0075] 16. The panel according to any of the preceding clauses, wherein the shape, in particular the cross-sectional shape, of the plurality of cavities is selected from the group consisting of polygonal, curvilinear and / or combinations thereof.

[0076] 17. The panel according to any of the preceding clauses, wherein some of the cavities are substantially prismatic comprising a prismatic base selected from the group consisting of: a curved prismatic base, a rounded prismatic base, an n-gonal prismatic base, where n≥3.

[0077] 18. The panel according to any of the preceding clauses, wherein the depth of at least a plurality of the cavities is between 10% and 30% of the maximum thickness of the core layer.

[0078] 19. The panel according to any of the preceding clauses, wherein the core layer comprises at least one pair of opposing edges, said pair of opposing side edges comprising complementary coupling members configured for mutual coupling of adjacent panels.

[0079] 20. The panel according to any of the preceding clauses, comprising at least one backing layer, wherein the backing layer, preferably forming a sound attenuating barrier, covers at least a portion of the bottom surface of the lower core layer.

[0080] 21. The panel according to any of the preceding clauses, wherein the density of the lower core layer is lower than the density of the upper core layer.

[0081] 22. The panel according to any of the preceding clauses, wherein the lower core layer is at least partially foamed.

[0082] 23. A panel according to any of the preceding clauses, comprising at least one top layer, preferably a decorative top layer, fixed to the core layer either directly or indirectly.

[0083] 24. A method for producing a panel, in particular a floor panel, a wall panel or a ceiling panel, preferably a panel according to any of the preceding clauses, comprising the following steps:

[0084] - providing a first composite material (preferably a substantially ductile first composite material);

[0085] - providing a second composite material, preferably wherein the Vicat softening temperature of the first composite material is at least 15 degrees Celsius higher than the Vicat softening temperature of the second composite material (preferably a substantially ductile second composite material);

[0086] - forming a core layer comprising an upper core layer comprising the first composite material and a lower core layer comprising the second composite material, wherein the core layer comprises a top surface and a bottom surface,

[0087] - preferably embossing a plurality of cavities in at least a portion of the bottom surface of the core layer, in particular the lower core layer, and;

[0088] - Hardening and / or curing the core layer.

[0089] 25. The method of clause 24, wherein the core layer is formed via coextrusion.

[0090] 26. Method according to clause 24 or 25, wherein at least a portion of the cavity is obtained via engraving, rotary engraving and / or rotary (die) cutting.

[0091] 27. A method according to any of clauses 24 to 26, wherein embossing the core layer is performed by guiding the core layer over at least two rollers, wherein at least one roller is provided with a surface structure configured to provide a plurality of cavities in at least a portion of the bottom surface of the core layer.

[0092] 28. The method of any one of clauses 24 to 27, wherein the second composite material has a Vicat softening temperature in the range of 50 degrees Celsius to 90 degrees Celsius.

[0093] 29. The method of any one of clauses 24 to 28, wherein the transition temperature of the second composite material is at least 10 degrees Celsius lower than the transition temperature of the first composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0094] The present invention will now be described in more detail with reference to the following non-limiting drawings. In this document:

[0095] Figures 1a to 1eeach a cross-section of a possible embodiment of a panel according to the invention;

[0096] Figures 2a to 2d each a bottom view of a possible embodiment of a panel according to the invention;

[0097] Figure 3a is a bottom view of another possible embodiment of a panel according to the present invention;

[0098] Figure 3b A roller which can be used to produce a panel according to the invention;

[0099] Figures 3c to 3h are bottom views of various possible embodiments of panels according to the present invention;

[0100] as well as

[0101] Figures 4a to 4i are cross-sectional views of various possible embodiments of the cavity according to the present invention.

[0102] In these drawings, like reference numerals correspond to similar or equivalent components and / or technical features. DETAILED DESCRIPTION

[0103] Figures 1a to 1e A schematic diagram illustrates a possible embodiment of a panel 100 according to the present invention. The figure shows a schematic diagram of a side view of a panel 100. Each panel 100a, 100b, 100c, 100d, 100e can be, for example, a floor panel 100, a wall panel 100, or a ceiling panel 100. Each panel includes a core layer 101 comprising an upper core layer 101a and a lower core layer 101b. The upper core layer 101a comprises a first composite material, while the lower core layer 101b comprises a second composite material. The Vicat softening temperature of the upper core layer 101a is different from the Vicat softening temperature of the lower core layer 101b. A portion of the bottom surface of the core layer 101 , in particular the lower core layer 101 b , of each panel 100a , 100b , 100c , 100d , 100e is provided with a plurality of embossed cavities 102 extending towards the top surface of the core layer 101 . Figure 1a It is shown that the panel 100 may optionally have interconnection coupling components 103a, 103b. The interconnection coupling components 103a, 103b may be applied to any embodiment covered by the present invention.

[0104] Figure 1a The panel 100a is shown as including a plurality of cavities 102 arranged at a predetermined distance from each other. The panel 100a also includes a top layer 106. In the embodiment shown, the top layer 106 is a ceramic panel 106 attached to the top surface of the core layer 101. Coupling members 103a, 103b extend through both the upper core layer 101a and the lower core layer 101b. Figure 1b A panel 100b is shown in which each cavity 102 has a different cavity 102 depth. The cavity 102 is substantially trapezoidal in cross-section. Optionally, the panel 100b may include a decorative top layer. Figure 1c An embodiment is shown in which the cavity 102 has a semicircular cross-section. The cavity 102 is filled with a sound absorbing material 107. The panel 100c further comprises a backing layer 108 attached to the bottom surface of the lower core layer 101b. Figure 1d The height or depth h of the cavity 102 is shown to be greater than the thickness of the lower core layer 101b. Thus, the cavity 102 extends to the upper core layer 101a. Figure 1e A side view of the panel 100e is shown, in which it can be seen that the cavity 102 extends substantially over the entire length of the panel 100e, but that the cavity 102 begins and ends at a predetermined distance from the outer end of the panel 100e. The panel 100e also includes a backing layer 108, in particular a balancing layer 108. The cavity 102 is free of filling material, such as sound absorbing material.

[0105] Figures 2a to 2d A schematic diagram of a possible embodiment of a panel 200 according to the present invention is shown. The figure shows a bottom view of the panel 200. Each panel 200a, 200b, 200c, 200d can be (for example) a floor panel 200, a wall panel 200 or a ceiling panel 200. Each panel 200 comprises a core layer 201, which comprises an upper core layer and a lower core layer. The figure shows the bottom surface of the lower core layer. A portion of the bottom surface of the core layer 201 of each panel 200a, 200b, 200c, 200d is provided with an (embossed) cavity 202 extending towards the top surface of the core layer 201. In the embodiment shown, the panels 200a, 200b, 200c, 200d are not provided with an (interlocking) coupling device. However, it is conceivable that such a coupling device can be used.

[0106] Figure 2a A panel 200a is shown comprising a plurality of substantially parallel cavities 202. Each cavity 202 is arranged at a predetermined distance from a peripheral edge of the panel 200a. It can also be observed that each cavity 202 extends in the longitudinal direction of the panel 200a. Figure 2b A panel 200b is shown in which the cavities 202 form a network of interconnected cavities 202. Experiments have found that such an embodiment can enhance the sound damping effect of the panel 200b. Figure 2c The panel 200c is shown with a plurality of individual cavities 202 extending substantially in the longitudinal direction of the panel 200c. The cavities 202 are locally widened. At least the locally widened areas can, for example, be filled with a sound absorbing material. Figure 2d A panel 200d is shown having a series of substantially V-shaped cavities 202. The cavities 202 are arranged at a predetermined distance from each other and do not interfere with adjacent cavities 202.

[0107] Figure 3a A schematic diagram of a possible embodiment of a panel 300 according to the present invention is shown. The figure shows a bottom view of the panel 300. The panel comprises a core layer 301, which comprises an upper core layer and a lower core layer. The figure shows the bottom surface of the lower core layer. A portion of the bottom surface of the core layer 301 is provided with a plurality of cavities 302. The cavities 302 extend towards the top surface of the core layer 301. The cavities 302 are integrally formed cavities 302. In the embodiment shown, the cavities 302 define a cell pattern, in particular a polygonal cell pattern. The figure shows that the cavities 302 are separated by separators 303, wherein the thickness of at least a portion of the separators 303 between the cavities 302 is less than the length and / or width of the cavities 302. In the embodiment shown, the cavities 302 are thermoformed to the bottom surface of the core layer 301.

[0108] Figure 3b The invention can be used to manufacture a panel 300 according to the invention (in particular as Figure 3a The core layer is subjected to a roller 330 (e.g., the panel shown). The plurality of cavities can be provided by performing a (rotational) embossing process on at least a portion of the bottom surface of the core layer. When this technique is applied, it can be performed substantially directly after the coextrusion of the core layer. For example, it is conceivable to pass the core layer over at least two rollers 330, at least one of which is provided with a surface structure 331 configured to provide a plurality of cavities on at least a portion of the bottom surface of the core layer.

[0109] Figures 3c to 3h Shows bottom views of various other possible embodiments of panels according to the invention. Figure 3a 3 and 4 show a bottom view of a portion of a panel according to the present invention. For various embodiments, these figures show a plurality of embossed cavities 302, particularly in a repeating pattern. The cavities 302 are separated by dividers 303, wherein at least a portion of the dividers 303 between the cavities 302 has a thickness that is less than the length and / or width of the cavity 302.

[0110] Figures 4a to 4i sectional views of various possible embodiments of the embossed cavity 402 according to the present invention are shown. As can be seen, the cavity 402 has a fairly clear boundary, so the cavity 402 can also function as a damping chamber.

[0111] Obviously, the invention is not limited to the working examples shown and described herein, but is susceptible of numerous variations within the scope of the appended claims, which will be obvious to a person skilled in the art.

[0112] The above-described inventive concepts are described by way of several illustrative embodiments. It is contemplated that individual inventive concepts may be employed without applying the other details of the described embodiments. It is not necessary to elaborate on all conceivable examples of combinations of the above-described inventive concepts, as those skilled in the art will appreciate that many inventive concepts may be (re)combined to achieve a particular application.

[0113] The verb "comprise" and its conjugations as used in this patent disclosure should be understood to mean not only "comprises", but also to mean the phrases "comprising", "consisting essentially of", "formed of", and their conjugations. When referring to a reinforcement layer, the reinforcement element may also be referred to, and vice versa. Within the scope of the present invention, when the term "embossed cavity" is used, the term "cavity" may also be applied, and vice versa. The upper core layer and the lower core layer may be an integrated core layer. The upper core layer may also be referred to as the core layer, and the lower core layer may be referred to as the bottom layer.

Claims

1. A panel comprising: At least one top level, and At least one core layer, the core layer comprising: at least one upper core layer comprising a first composite material and having a Shore D hardness in the range of 85 to 95; and at least one lower core layer comprising a second composite material; wherein the core layer comprises at least one pair of opposing edges comprising complementary coupling members configured for mutual coupling of adjacent panels, wherein the thickness of the upper core layer is at least 1.5 mm, and the thickness of the lower core layer is at least 30% greater than the thickness of the upper core layer, wherein at least a portion of the bottom surface of the lower core layer is provided with a plurality of embossed cavities, and The Vicat softening temperature of the upper core layer is at least 15 degrees Celsius higher than the Vicat softening temperature of the lower core layer.

2. The panel according to claim 1, wherein the panel is a floor panel, a wall panel or a ceiling panel. The panel according to claim 1 , wherein the panel is a decorative panel.

4. The panel of claim 1, wherein the Vicat softening temperature of the lower core layer is in the range of 50 degrees Celsius to 90 degrees Celsius.

5. The panel of claim 1 wherein the modulus of elasticity of the lower core layer is at most 50% of the modulus of elasticity of the upper core layer. The panel of claim 1 , wherein the upper core layer has an elastic modulus of at least 3500 MPa.

7. The panel according to any one of the preceding claims 1-6, wherein the Shore D hardness of the lower core layer is in the range of 55 to 65.

8. The panel according to any one of the preceding claims 1 to 6, wherein the first composite material comprises at least 40 wt% mineral material.

9. The panel according to claim 8, wherein the first composite material comprises at least 50% by weight of mineral material.

10. The panel of claim 8 wherein the first composite material comprises at least 60% by weight of mineral material.

11. The panel according to any one of the preceding claims 1-6, wherein the second composite material comprises at most 60 wt% mineral material.

12. The panel according to claim 11, wherein the second composite material comprises at most 50 wt% mineral material.

13. The panel of claim 11 wherein the second composite material comprises at most 30 wt% mineral material.

14. The panel according to any one of the preceding claims 1-6, wherein the first composite material and / or the second composite material comprises at least one selected from the group consisting of the following mineral materials: magnesium oxide, magnesium chloride, magnesium oxysulfate, calcium carbonate, chalk, clay, calcium silicate or talc.

15. The panel according to any one of the preceding claims 1-6, wherein the first composite material and / or the second composite material comprises at least one selected from the group consisting of the following thermoplastic materials: polyvinyl chloride, polystyrene, polyethylene, polyurethane, acrylonitrile butadiene styrene copolymer, polypropylene or combinations thereof.

16. The panel according to any one of the preceding claims 1-6, wherein the first composite material and / or the second composite material comprises at least one selected from the group consisting of the following thermosetting resins: phenolic resin, melamine formaldehyde resin or a combination thereof.

17. The panel according to any one of the preceding claims 1 to 6, wherein the core layer comprises at least one adhesive.

18. The panel of claim 17, wherein the ratio of the weight percentage of mineral material to the binder is at least 1.

19. The panel of any one of the preceding claims 1-6, wherein the upper and lower core layers are formed via coextrusion.

20. The panel according to any one of the preceding claims 1-6, wherein the cavity is formed during the extrusion process, or immediately after the extrusion process, or by hot pressing.

21. The panel of any one of the preceding claims 1-6, wherein the plurality of embossed cavities defines a repeating cavity pattern.

22. The panel according to any one of the preceding claims 1-6, wherein the shapes of the plurality of cavities are selected from the group consisting of polygonal, curvilinear and / or combinations thereof.

23. The panel of claim 22, wherein the shape of the plurality of cavities is a cross-sectional shape.

24. The panel as claimed in any one of the preceding claims 1-6, wherein the depth of at least a plurality of cavities is between 10% and 30% of the maximum thickness of the core layer.

25. The panel according to any one of the preceding claims 1-6, comprising at least one backing layer, wherein the backing layer covers at least a portion of the bottom surface of the lower core layer.

26. The panel of claim 25, wherein the backing layer forms a sound attenuating barrier.

27. The panel according to any one of the preceding claims 1-6, wherein the density of the lower core layer is lower than the density of the upper core layer.

28. The panel according to any one of the preceding claims 1-6, wherein the lower core layer is at least partially foamed.

29. The panel according to any one of the preceding claims 1-6, comprising at least one top layer fixed directly or indirectly to the core layer.

30. The panel of claim 29, wherein the at least one top layer is a decorative top layer.

31. The panel according to claim 30, wherein the decorative top layer comprises high pressure laminate (HPL), a plurality of impregnated layers comprising lignocellulose, a wood veneer, a thermoplastic layer comprising at least one decorative layer and a protective top layer, a stone veneer, and / or combinations thereof.

32. The panel according to any one of the preceding claims 1-6, wherein the top-facing surface of the upper core layer comprises a primer, and a visual effect printed by a direct printing process.

33. A method for manufacturing a panel, the method comprising the steps of: - providing a first composite material; - providing a second composite material, wherein the Vicat softening temperature of the first composite material is at least 15 degrees Celsius higher than the Vicat softening temperature of the second composite material; - forming a core layer comprising an upper core layer comprising the first composite material and a lower core layer comprising the second composite material, wherein the core layer comprises a top surface and a bottom surface, - embossing a plurality of cavities in at least a portion of the bottom surface of the core layer, and; - Hardening and / or curing of the core layer.

34. The method of claim 33, wherein the panel is a floor panel, a wall panel or a ceiling panel.

35. The method of claim 33, wherein the panel is a panel according to claim 1.

36. The method of claim 33, wherein the core layer is formed via coextrusion.

37. The method of claim 33, wherein at least a portion of the cavity is obtained via engraving, rotary engraving and / or rotary die cutting.

38. A method according to claim 33, wherein the embossing of the core layer is performed by guiding the core layer through at least two rollers, wherein at least one of the rollers is provided with a surface structure configured to provide a plurality of cavities in at least a portion of the bottom surface of the core layer.

39. The method of claim 33, wherein the second composite material has a Vicat softening temperature in the range of 50 degrees Celsius to 90 degrees Celsius.

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