Panel and method for producing panel

Abstract

The present invention relates to a panel comprising a core layer, the core layer comprising a porous substrate and a support structure, and the panel comprising a decorative layer adhered to at least one core layer. The panels are typically made by extrusion, in particular by co-extrusion.

Description

Technical Field

[0001] The invention relates to a panel. The invention also relates to a method for preparing a panel. The invention also relates to a system using the method of the invention. Background Art

[0002] Architectural and / or decorative panels, commonly used as furniture, shelving, flooring, door panels and building panels, are usually wood-based, with particleboard, high-density fiberboard (HDF), medium-density fiberboard (MDF), oriented strand board (OSB), plywood, etc. forming the core of the panel. However, these wood panels have several disadvantages. Since these panels are usually made of melamine urea formaldehyde (MUF) and / or phenol-based resins as adhesives, this raises concerns about volatile organic compounds (VOCs) and indoor air quality. As wood panels, they are susceptible to humidity fluctuations and water, which can cause warping and delamination. Sealing the edges of the panels with decorative foil requires the use of adhesives, which may leak and be visible at the joints. Wood panels are often anisotropic, with the material having different physical properties such as stiffness, expansion and / or swelling depending on the measurement axis, which may have adverse effects when providing fastening means. Wood panels may have local defects such as cracks or knots, which may affect their local strength. Summary of the invention

[0003] The object of the present invention is to provide an improved panel for use in furniture, shelving, flooring, door panels and building boards which overcomes at least some of the above-mentioned disadvantages, or at least provides an alternative to the known panels.

[0004] The present invention provides a panel comprising at least one core layer, in particular at least one porous substrate, and optionally at least one supporting structure, and at least one decorative layer adhered to at least one core layer, wherein at least one core layer comprises a front surface and a rear surface located on opposite sides, wherein the thickness of at least one core layer is defined by the distance between the front surface and the rear surface, and wherein, preferably, at least a portion of at least one supporting structure extends over the thickness of at least one core layer.

[0005] An advantage of the panel according to the invention is that at least one core layer comprises at least one porous substrate and at least one supporting structure. The combination of the porous substrate and at least one supporting structure according to the invention can form a relatively strong core layer. An advantage of the core layer is that at least a part of the at least one supporting structure extends over the thickness of the at least one core layer, thereby obtaining a strong and effective geometry. Thus, the at least one supporting structure can constitute the skeleton structure of the panel. The supporting structure can also be referred to as a skeleton structure. Since at least one supporting structure extends over the thickness of the at least one core layer, a relatively thin porous substrate can be used. The orientation of at least part of the supporting structure provides rigidity to the porous substrate. Thus, the core layer benefits from the porous material and the supporting structure. The panel of the invention has particularly good rigidity and strength.

[0006] In the present invention, the panel can be any panel suitable for decoration and / or construction. Thus, the panel can be a decorative panel and / or a structural panel. For example, according to the present invention, the panel can be configured as and / or suitable for furniture, shelves, door panels, but can also be decorative and non-decorative building panels, floors, walls and / or ceilings. For example, the panel can be a floor, a wall or a ceiling. When referring to a porous substrate, it can also be referred to as a substrate comprising a porous material. A non-limiting example of a porous material is, for example, a foamed material. Thus, the panel according to the present invention may include at least one at least partially foamed core layer. For example, it is conceivable that the panel comprises a foamed thermoplastic core layer, such as foamed PVC, foamed PET, foamed PP and / or foamed WPC; a foamed thermosetting core layer, such as foamed TPU and / or PU foam; and / or a foamed inorganic core layer, for example comprising MgO, MgSO 4 MgCl 2 , fiber cement and / or aluminosilicate. It is also conceivable that the panel comprises an organic core layer, for example comprising cork, mycelium or the like. The core layer is preferably a waterproof core layer. The panel is preferably a waterproof panel.

[0007] It is conceivable that at least a portion of the front and rear surfaces of the core layer is formed by a support structure. It is also conceivable that at least a portion of at least one support structure extends over the entire thickness of the porous substrate of at least one core layer. The panels and substrates can have a variety of possible shapes. For example, the panels and / or substrates can be substantially plate-shaped. It is conceivable that the thickness of the core layer is substantially uniform over the entire core layer and / or the length of the core layer. In this case, it is beneficial if the height of at least a portion of the support structure is substantially equal to the thickness of the core layer. It is also conceivable that at least a portion of at least one support structure extends over the minimum thickness of at least one core layer. The core layer can have a variable thickness. For example, it is conceivable that at least a portion of at least one support structure forms a connection or a bridge between the front surface of the core layer and the rear surface of the core layer. It is conceivable that at least a portion of at least one support structure is at an angle relative to the plane defined by the front surface and / or the rear surface of the core layer. It is conceivable that one embodiment at least a portion of at least one support structure is substantially perpendicular to the plane defined by the front surface and / or the rear surface of the at least one core layer. When referring to the front surface and the rear surface, this can also be a first (side) surface and a second (side) surface. In particular, it refers to opposite sides of the panel. According to the invention, the panel can be applied in a plurality of directions. Therefore, the terms "front" and "rear" should not be interpreted as restrictive. Instead of the terms front and rear, terms such as upper and lower, first and second, primary and secondary can also be used. The upper side and the lower side, or the front side and the rear side, are usually two opposite sides with the largest surface area, which serve as the main decorative surfaces. For example, the panel is essentially rectangular. However, the panel according to the invention can have any convenient shape. For example, it is conceivable that the panel is a cuboid or a hexahedron, in particular comprising a plurality of faces.

[0008] At least one core layer may preferably have a thickness of at least 3 mm. For example, it is conceivable that the thickness of at least one core layer is between 3 mm and 20 mm or between 5 mm and 16 mm, preferably between 6 mm and 8 mm or between 14 mm and 16 mm. An advantageous embodiment comprises a core layer having a thickness in the range of 2.5 to 4 mm or in the range of 3.5 to 5 mm. In the case where the panel comprises a plurality of core layers, it is also conceivable that the thickness of the core layers is different. For example, it is conceivable that the thickness of the core layer combination is between 3 and 12 mm. It is conceivable that the panel has a plurality of core layers, at least one of which has a thickness in the range of 0.5 to 1 mm and at least one other of which has a thickness in the range of 1 to 3 mm. The panel may comprise at least three core layers adjacent to each other, wherein a central core layer is enclosed between an upper core layer and a lower core layer. It may be preferred that the upper core layer and / or the lower core layer have a greater thickness than the central core layer, and vice versa. For example, the thickness of at least one supporting structure may be substantially equal to the thickness of the core layer.

[0009] In a preferred embodiment, at least one supporting structure or at least one skeleton structure comprises a plurality of ribs. In a further preferred embodiment, at least one rib, preferably at least two ribs, or more preferably each rib, extends over the thickness of at least one core layer. In this way, at least one rib or multiple ribs can form a reinforcement structure in the core layer, in particular in the porous substrate. It is also conceivable that at least one supporting structure comprises a plurality of pillars. When referring to ribs, pillars can also be referred to, and vice versa. In a preferred embodiment, at least one rib, preferably at least two ribs, or more preferably each rib of at least one supporting structure extends over the entire thickness of the porous substrate of at least one core layer. At least two ribs are preferably substantially parallel to each other. In this embodiment, good strength can be achieved by applying ribs. The parallel orientation of the ribs can contribute to the good stiffness of the core layer and the panel. It is possible that at least two ribs or multiple ribs extend substantially parallel to the entire porous substrate. For example, it is conceivable that at least two ribs are substantially parallel to each other in a direction substantially perpendicular to the length direction of the panel. In the case where the panel is an extruded panel, it is conceivable that at least two ribs are substantially parallel in a direction at an angle to the extrusion direction. For example, it is possible that at least two ribs are substantially parallel to each other in a direction substantially perpendicular to the extrusion direction. Alternatively and / or additionally, at least two ribs may define a triangular shape, for example, wherein the legs of the triangle extend from the front surface to the rear surface of the core layer, or vice versa. It is also conceivable that at least two ribs are substantially parallel in a direction corresponding to the length of the panel.

[0010] In one possible embodiment, at least two ribs of at least one support structure may be interconnected. Thus, it is conceivable that at least one support structure is composed of a plurality of substantially adjacent and / or parallel ribs interconnected. These ribs may form an interconnected network, thereby defining a support structure. It is also conceivable that at least two ribs are substantially isolated from each other. Thus, it is conceivable that at least one support structure is composed of a plurality of independent ribs. For example, a plurality of individual ribs may together constitute a support structure. It is also conceivable that the core layer comprises a plurality of support structures. The orientation and / or position of at least one support structure and / or at least one rib (preferably a plurality of ribs) contribute to enhancing the rigidity characteristics of the core layer.

[0011] Advantageously, the strength of the panel is significantly increased due to the presence of a support structure in the core layer. Several aspects of the panel can be measured. The American Society for Testing and Materials provides a standard test method, ASTM D 1037-96, for evaluating the properties of wood fiber and particleboard materials. These include the flexural modulus of elasticity (MOE) and the modulus of rupture (MOR). Other useful tests included in ASTM D 1037-96 include direct screw pull-out testing, hardness testing, hardness modulus testing, board plane shear strength, glue line shear testing, and drop ball impact testing. If the panel is used as part of a furniture product, the ANSI / KCMA A161.1 Kitchen Cabinet Furniture Test may be particularly useful.

[0012] The average density in the test is 250kg / m 3 When a three-layer porous polyethylene terephthalate (PET) core layer (including a support structure) is tested, there is a significant difference between the modulus of rupture (MOR) and the modulus of elasticity (MOE) if the extension direction of the support structure is taken into account. MOE and MOR are tested according to ASTM D 1037-96. The three-layer panel is a porous sheet material comprising polyethylene terephthalate (PET), which includes pores or voids. The pore volume of the support structure in each panel is on average less than the pore volume of the surrounding porous substrate. Therefore, in this test, the support structure of each panel is composed of PET, which has a relatively high density compared to the average density of the panel.

[0013] The support structure is a rib extending linearly and parallel throughout the core layer, thus dividing the porous substrate into two parts, wherein the two parts are located on opposite sides of the rib. The rib itself is beam-shaped or plate-shaped. In the first core layer, the MOE was tested in the direction from the front and rear surfaces located on opposite sides of the core layer, and a single rib (support structure) extended over the entire core layer parallel to the front and rear surfaces. Therefore, the direction of force applied is perpendicular to the direction of the rib extension plane. The MOE of the first core layer was 82.3 MPa and the MOR was 3.5 MPa.

[0014] In the second porous PET core layer, similar ribs extend across the entire core layer perpendicular to the front and back surfaces of the core layer. The support structure of the second porous PET core layer is rotated 90 degrees compared to the support structure of the first porous PET core layer. Therefore, the direction of the force used to measure the MOE and MOR is the same as the direction in which the ribs extend. The measured MOE and MOR almost doubled to 176MPa and 5.7MPa, respectively.

[0015] In the third porous PET core layer, the ribs extend in the same direction as the second porous PET core layer, but are offset to one side of the core layer. The measured MOE and MOR values ​​are 191 MPa and 5.7 MPa, respectively. These results are very similar to those of the second porous PET core layer. Therefore, the orientation of the support structure in the core layer seems to have a great influence on the overall strength of the core layer.

[0016] For an average density of 250 kg / m 3 The average strength of the core layer of the porous PET including the (integrated) support structure appears to be between 170 and 200 MPa, while the average strength of the foamed PET without any support structure appears to be between 70 and 90 MPa. "Integrated" as used herein is defined as being part of the core layer, in which case the core layer consists of the same compound as the porous substrate itself.

[0017] If the core layer is made of wood plastic composite (WPC), the average MOE value is between 400 and 800 MPa, preferably between 500 and 700 MPa, for example, the average MOE value is 600 MPa in the absence of a support structure. If a support structure having the same shape and orientation as the support structure in the second or third porous PET core layer is present, the average MOE value is between 1200 and 1800 MPa, preferably between 1350 and 1650 MPa, for example, 1500 MPa.

[0018] Another option is to provide an aluminum support structure in the wood plastic porous substrate. If the thickness of the support structure, having the shape and orientation of the second or third porous PET core layer as described herein, and the thickness ranges between 0.3 and 2 mm, the average MOE value is between 4000 and 6000 MPa, preferably between 4500 and 5500 MPa, for example 5000 MPa.

[0019] In one possible embodiment of the panel according to the invention, the panel comprises at least two core layers. For example, the panel may comprise at least two core layers, wherein each core layer comprises at least one porous substrate and at least one supporting structure. It is conceivable that the first supporting structure of the first core layer is arranged at a certain angle relative to the second supporting structure of the second core layer. Each core layer can be any embodiment of the core layer described according to the invention. For example, the panel may comprise at least two stacked or connected core layers, wherein the at least two core layers comprise a plurality of ribs, in particular parallel ribs, wherein at least part of the ribs of the first core layer are arranged at a certain angle relative to at least part of the ribs of the second core layer, preferably substantially perpendicular to at least part of the ribs of the second core layer.

[0020] Preferably, at least a portion of the support structure is substantially rigid. In a further preferred embodiment, the support structure is a rigid support layer. It is also conceivable that the components defining the support structure are not rigid per se, but their orientation and / or position give the support structure rigid characteristics. It is conceivable that at least a portion of the support structure forms a grid structure.

[0021] In a possible embodiment of the panel of the present invention, at least a portion of at least one supporting structure is embedded in at least one porous substrate. Therefore, at least a portion of at least one supporting structure, preferably the entire supporting structure, is embedded in the porous material constituting the porous substrate. In this way, at least one supporting structure can form part of the core layer in an effective and controllable manner. Embedding at least a portion of the supporting structure in at least one porous substrate can enhance the synergy between the supporting structure and the porous substrate. For example, it is conceivable that at least a portion of at least one supporting structure is connected to at least a portion of at least one porous substrate by an adhesive. It is also possible that at least a portion of at least one supporting structure is connected to at least a portion of at least one porous substrate by lamination, in particular thermal lamination. In this embodiment, the material of the supporting structure is generally different from the material constituting the porous substrate. It is conceivable that the supporting structure and the substrate are made of the same material.

[0022] It is also conceivable that at least a portion of at least one support structure forms an integral part of at least one porous substrate. In this way, the core layer can benefit from an integrally formed support structure, which can provide strength and rigidity from the core of the core layer, in particular the core of the porous substrate. An integrally formed support structure is less prone to weak points at joints and / or connections. For example, the support structure can be an integrated support structure, wherein in particular the support structure is integrated into the porous material of the porous substrate. For this embodiment, the support structure is preferably made of the same material as the porous substrate. The support structure can be formed during the formation of the core layer.

[0023] It is conceivable that at least a portion of at least one supporting structure is defined as a honeycomb structure, a bubble shield, a corrugated plate, a corrugated structure and / or a double-walled structure. At least a portion of at least one supporting structure defining any of the above structures can further contribute to the strength and / or rigidity of the panel. For example, it is conceivable that the wall of the honeycomb structure, bubble shield, corrugated plate, corrugated structure and / or double-walled structure extends over the thickness of the core layer. It is also conceivable that the wall defining the honeycomb structure, bubble shield, corrugated plate, corrugated structure and / or double-walled structure extends at a certain angle, in particular substantially perpendicular to the plane defined by the front and / or rear surfaces of the panel, preferably substantially perpendicular to the plane defined by the front and / or rear surfaces of the core layer. For example, the honeycomb structure can be an aluminum honeycomb structure and / or a thermoplastic honeycomb structure. However, another embodiment can also be envisioned, in which the panel includes at least one additional supporting structure or secondary supporting structure. At least one secondary supporting structure can be a separate layer in addition to at least one core layer. It is also conceivable that at least one secondary supporting structure constitutes a part of at least one core layer. At least one secondary supporting structure can be defined as any embodiment of the supporting structure according to the present invention. Further embodiments are also conceivable in which at least a portion of at least one support structure is defined as a grid. The support structure preferably extends over the entire core layer covering the panel. Thus, it is conceivable that the support structure defining the grid extends over the entire core layer. At least a portion of the support structure may be filled with at least one porous material.

[0024] When at least one support structure is provided on the front and / or rear surface of the panel, the stiffness of the panel can be increased, so the support structure is preferably substantially rigid. The use of at least one support structure of the present invention can further increase the screw pull strength, thereby allowing a more secure fastening device to be provided between panels.

[0025] In a preferred embodiment, at least one core layer is an extruded core layer. In a preferred embodiment, at least one porous substrate is an extruded substrate. In some specific embodiments, the extruded substrate comprises at least two materials extruded simultaneously. The panel according to the present invention may also be an extruded panel. Extrusion is a preferred production method because it is relatively competitive in cost and enables continuous batch production. For example, the panel according to the present invention may be produced by the method according to the present invention. It is conceivable that the core layer of the panel is made by co-extruded layers, which form a plurality of individually extruded layers, which are then cut into blocks or sheets consisting of a plurality of mutually bonded co-extruded core layers, and the reinforcing layers are formed by the adjacent surface layers or shell layers, forming reinforcing pillars or ribs in the entire volume of at least one core layer. At least one supporting structure may have a ribbed structure extending to the core layer, for example formed by a specially formed extrusion die. It is conceivable to co-extrude with a top layer and / or a bottom layer, or a front layer and / or a back layer, both of which have a ribbed structure extending to the core layer, and the porous material is formed in the grooves formed by the ribbed structure.

[0026] The core layer or porous substrate can also be obtained by multi-layer extrusion. It is conceivable that the core layer or porous substrate is composed of multiple materials. For example, at least one core layer or at least one porous substrate can be composed of materials arranged in an alternating manner. For example, at least one core layer or porous substrate can include an alternating sequence of a first polymer material and a second polymer material, for example, in a (-SPC-WPC-)*n configuration, where n is an integer ≥1.

[0027] In one possible embodiment, the panel according to the invention comprises at least two decorative layers. It is conceivable that the first decorative layer is adhered to the front surface of the core layer and / or the second decorative layer is adhered to the rear surface of the core layer. It is also conceivable that a further layer is present between at least one core layer and at least one decorative layer. The first decorative layer may be substantially identical to the second decorative layer. However, it is also conceivable that the first decorative layer is different from the second decorative layer. According to any embodiment of the decorative layer described according to the invention, the first decorative layer and / or the second decorative layer may be applied, if applicable.

[0028] At least one core layer may comprise at least one side edge, to which at least one decorative layer may be adhered. In this embodiment, the panel may be used, for example, for decorative purposes, and / or for furniture and / or to form a door. Typically, in a panel according to the invention, the surface area defined by the front surface and / or the rear surface is greater than the surface area defined by at least one side edge. It is conceivable that at least one decorative layer completely encloses the core layer. It is also possible to provide decorative layers on all sides, including the front and rear surfaces of the panel. For example, a (rectangular) block-shaped panel may have six sides provided with decorative layers.

[0029] According to the panel of the present invention, in particular the core layer thereof may include a sealing edge. It is therefore conceivable that the porous material forming the porous substrate is substantially sealed on all sides. For example, the panel may include a sealing strip or a sealing layer, preferably achieved by heat lamination. The sealing layer may be heat laminated to the outside of the core layer. This has the additional benefit that the porous structure of the porous substrate and the porous structure of the optional supporting structure part are both sealed. This prevents dirt from accumulating or moisture from the surrounding environment from being absorbed into the core layer. A separate sealing strip may be used. This embodiment allows the porous substrate to be sealed by heating, allowing for greater structural integrity at the edges and providing support for screws, fastening devices, snap-on systems and / or interlocking mechanisms.

[0030] In a preferred embodiment, the panel comprises mutually matching connecting elements and / or connecting parts. For example, it is conceivable that at least two sides of the panel comprise mutually matching connecting elements. For example, the connecting elements and / or connecting parts may be configured to provide a snap connection and / or a slot connection. For example, the connecting parts of the panel may be interlocking connecting parts, preferably providing horizontal and vertical locking. Interlocking connecting parts are connecting parts that require elastic deformation, snap or multi-directional movement to connect or separate parts. Any suitable interlocking connecting parts known in the art may be applied. A non-limiting example is an embodiment in which the first side of the first pair of opposite sides comprises a first connecting part, and the second side of the first pair of opposite sides comprises a complementary second connecting part, the connecting part allowing a plurality of panels to be connected to each other; wherein the first connecting part comprises a lateral tongue extending in a direction substantially parallel to the plane defined by the panel, wherein the second connecting part comprises a groove, the groove being configured to accommodate the lateral tongue of at least a portion of another panel, the groove being defined by an upper lip and a lower lip. It is conceivable that the connecting part or the snap assembly is thermoformed and / or milled.

[0031] The compressive strength of the support structure can be higher than the compressive strength of the porous substrate as measured in the direction from the front surface to the back surface of the core layer according to ASTM-D1037. Advantageously, the support structure can increase the overall compressive strength of the core layer and the panel. This makes the panel stronger, more rigid, and less likely to break under pressure.

[0032] Preferably, at least one support structure and the porous substrate comprise the same compound, and the density of the support structure is higher than the density of the porous substrate. This allows the support structure and the porous substrate to be bonded together without any adhesive, for example by thermal lamination. The same compound is defined herein as substantially the same molecule. For example, both the support structure and the porous substrate can be made of polyvinyl chloride. However, the density of the porous substrate can be lower than the density of the support structure because the porous substrate can contain more pores and / or have a larger volume of pores (i.e., have a larger pore size). Since the density of the support structure is increased relative to the porous substrate, the strength of the support structure is higher than that of the porous substrate, thereby enabling the support structure to support the entire core layer. Therefore, the average pore volume of the porous substrate is preferably greater than the average pore volume of the support structure. Alternatively, the support structure may be substantially free of pores.

[0033] The porous substrate and / or the support structure may comprise a thermoplastic polymer or a thermosetting polymer. Thermoplastic polymers are preferred because they can be heated before extrusion, thereby better controlling the viscosity of the extruded material. However, thermosetting polymers are also possible.

[0034] The porous substrate and / or the supporting structure may comprise at least one selected from polyvinyl chloride (PVC), polystyrene (PS), polyethylene (PE), high density polyethylene (HDPE), low density polyethylene (LDPE), cross-linked polyethylene (XPE), polyurethane (PU), acrylonitrile butadiene styrene copolymer (ABS), polypropylene (PP), polyethylene terephthalate (PET), thermoplastic starch (TPS), cross-linked polystyrene (XPS), styrene acrylonitrile copolymer (SAN), polyphenylene oxide (PPO), polylactic acid (PLA), phenolic resin, melamine resin, formaldehyde resin or any combination thereof. Preferably, the porous substrate and / or the supporting structure are at least partially biodegradable. Therefore, the preferred polymer is biodegradable. It is conceivable that the porous substrate comprises at least one bioplastic. It is also conceivable that the porous substrate and / or the supporting structure is made of a bioplastic.

[0035] The above polymers may also be thermoplastic binders. The core layer preferably comprises at least one such thermoplastic binder. However, it is also conceivable that the core layer further comprises at least one thermosetting binder in addition or alternatively. The use of at least one thermoplastic or thermosetting material in the core layer is considered to give the panel flexible properties when necessary, for example when flexibility is required to achieve the engagement of a locking mechanism.

[0036] The porous substrate and / or support structure may include starch-based plastics, soy-based plastics, cellulose-based plastics, lignin-based plastics and / or natural fibers. The biodegradability of these plastics makes them environmentally friendly panels, so that the panels can biodegrade after their lifespan.

[0037] The core layer, in particular the porous substrate, may include at least one filler. The filler may include organic or inorganic materials, including but not limited to cellulosic materials, fibrous materials, kraft paper, sawdust, wood chips, wood fibers, long wood fibers, short wood fibers, sand, lime, volcanic ash, plant fibers (such as mushroom fibers, cotton fibers, bamboo fibers, abaca fibers, pineapple fibers), magnesium compounds, magnesium oxide, magnesium alloys, magnesium alloys, magnesium alloys, magnesium alloys, magnesium alloys, magnesium alloys, magnesium alloys, etc., pineapple fibers, magnesium compounds, magnesium oxide, magnesium carbonate, limestone, polymer fibers, glass fibers, carbon-based fibers, polymer particles, or hollow microspheres or particles with a particle size range of 1 to 1000 microns made of, including but not limited to, ceramics, glass, polymers, composite materials or metals. Preferably, the core layer includes at least one filler selected from the following groups: minerals (preferably calcium carbonate), pigments, modifiers, fibers (such as glass fibers, wood, straw and / or hemp). The fibers may be loose fibers and / or interconnected fibers to form a woven layer or a non-woven layer. Preferably, the core layer further comprises at least one additional filler selected from steel, glass, polypropylene, wood, acrylic, alumina, curaua, carbon, cellulose, coconut, kevlar, nylon, perlon, polyethylene, PVA, asbestos, viburnum and fique. This may further increase the strength of the panel and / or the water resistance and / or fire resistance of the panel. The core layer may be a wood plastic composite core layer.

[0038] The density of the porous substrate may be lowest at a position farthest from the support structure, while the density of the porous substrate may be highest at another position adjacent to the support structure. The porous substrate may be formed from a plurality of porous sheets which are expanded and laminated together by extrusion of a mixture (including a thermoplastic polymer). Thus, the laminated outer edges of the porous sheets constitute the support structure. Due to the rapid cooling of the outer edges, the expansion of the outer edges is minimal. The center of each porous sheet can be kept at high temperature for a longer time than the outer edges, and therefore, the expansion of these centers is greater, resulting in the lowest density of these centers. Advantageously, this makes the core layer of the support structure have the highest density. Therefore, the density of the porous substrate may be gradient. Therefore, at least one porous substrate, in particular the porous material of the porous substrate, may have a density gradient. It is conceivable that at least one edge or at least two edges of the porous substrate have a higher density than the central part of the porous substrate. The density gradient is conducive to providing support for tightening, for example providing support in a plane perpendicular to the panel. For example, the density gradient may be a density gradient over the thickness or height of the core layer. It is also conceivable that the density gradient extends in a direction substantially perpendicular to the thickness direction of the panel. For example, it is conceivable that the density near the front surface and / or the density near the back surface is higher than the density in the central area of ​​the core layer located between the front surface and the back surface. The density of at least a part of the central area of ​​the core layer is preferably substantially constant or uniform. For example, it is conceivable that the density near the front surface and / or the back surface of at least one core layer is at least 5% higher than the average density of the core layer, preferably at least 10% higher. The density near the front surface and / or the density near the back surface is preferably higher than the density of the main body of the core layer. When referring to the density near the front surface or near the back surface, it can refer to the upper area or the bottom area of ​​the core layer. Basically, it is conceivable that such an embodiment: the core layer or porous substrate includes an upper skin layer and / or a lower skin layer. The density of each skin layer is at least 5% higher than the average density of the core layer, preferably at least 10% higher. The skin layer is an internal skin layer and is an integral part of the core layer. The skin layer can also be called a shell layer. The skin layer is basically an integral protective layer of the core layer. In a further preferred embodiment, the density (of the core layer) near the front surface is higher than the density (of the core layer) near the back surface. For example, it is also conceivable that the density of the at least one core layer is 70% to 90%, preferably 75% to 85%, of the mass density of the composite material (forming the core layer) in the non-foamed state.

[0039] The density of the porous substrate can be between 80 and 1000 kg / m 3 Between, preferably 100 to 1000 kg / m 3 More preferably, it is between 300 and 1000 kg / m 3 Between, such as about 600kg / m 3When the porous substrate and the support structure are formed of different compounds, the density of the porous substrate can be relatively uniform. The density of the porous substrate can also vary from a location distal to the support structure to a location proximal to the support structure. Having a lower density distal to the support structure is advantageous because the overall weight of the core layer is significantly reduced, while the relatively higher density of the support structure provides increased strength.

[0040] Preferably, the core layer has a discrete density gradient. Preferably, the density of the porous substrate is relatively low and relatively uniform compared to the average density of the core layer. Preferably, the density of the support structure is relatively high and relatively uniform compared to the average density of the core layer. In particular, in the case where the porous substrate and the support structure comprise the same compound and have different cell volumes and numbers, the density gradient between the porous substrate and the support structure is discrete. This ensures that the porous substrate is very light, while the support structure is heavy and can bear most of the loads applied to the panel.

[0041] According to the invention, at least one core layer of the panel is preferably at least partially foamed. Within the scope of the invention, different degrees of foaming are conceivable. Preferably, the panel, in particular at least one core layer, has an expansion rate of 5% to 50%. A non-limiting example is an expansion rate between 15% and 35%, in particular between 20% and 30%. However, it is also conceivable that the panel, in particular at least one core layer, has an expansion rate of at least 10%, preferably at least 20%, more preferably at least 30%, even more preferably at least 40%. The expansion rate is in particular a measure of the rate of change of the volume of the panel, in particular the core layer.

[0042] At least one core layer may include at least one mineral filler, preferably selected from the group consisting of calcium carbonate (CaCO 3), chalk, clay, calcium silicate (Si-Cal), dolomite, talc, magnesium oxide (MgO), magnesium chloride (MgCl or MOC cement), magnesium sulfate (MOS cement) and / or limestone. The purpose of using at least one mineral material in the core layer is to provide sufficient hardness to ensure the dimensional stability of the panel. For example, it is conceivable that the mineral material includes magnesium-based minerals, such as but not limited to magnesium oxide (MgO), magnesium chloride (MgCl or MOC cement), magnesium sulfate (also known as MOS cement). If limestone is used as the mineral filler, the mesh size of the limestone is preferably 325 mesh or 400 mesh. For example, the core layer may include a composite material whose weight ratio of mineral filler to thermoplastic binder is at least 3:1. It is also conceivable that the weight ratio of mineral filler to thermoplastic binder of the composite material is greater than 3.5:1, or is in the range of 3:1 to 4:1. However, alternatively, it is also conceivable that the core layer contains at least 30% by weight of at least one mineral filler, preferably at least 50% (by weight), and more preferably at least 60% (by weight). For example, the composite material contains at most 40% of the at least one thermoplastic binder, preferably at most 30% (by weight), more preferably at most 25% (by weight). It is conceivable that the ratio may also be smaller, such as 1:1, 1.5:1 or 2:1. The Vicat softening temperature of the core layer is at least 80 degrees Celsius, preferably at least 85 degrees Celsius, and / or the Shore D hardness of the front surface and / or the rear surface of the panel is at least 85. The use of at least one mineral material in the core layer can provide sufficient hardness, advantageously above 4000 MPa MOE and 22 MPa MOR, to ensure dimensional stability and toughness of the panel. The use of at least one polymer in the core layer is envisaged to give the panel flexible properties when necessary or, for example, when flexibility is required to achieve the engagement of a locking mechanism, and if used, the flexibility is preferably below 9000 MPa and 36 Nm MOR. The core layer according to the invention is particularly suitable for thermal bonding processes. The composite material of the core layer can, for example, include at least one additive to increase the Vicat softening temperature. For example, at least one additive may include acrylonitrile styrene acrylate (ASA), acrylonitrile butadiene styrene (ABS), a thermosetting system and / or an epoxy system. At least one additive may also be a Vicat modifier or referred to as a Vicat modifier. In another embodiment, at least one polymer of the composite material may be a thermosetting polymer.

[0043] In one embodiment, the porous substrate and / or support structure comprises a wood plastic composite (WPC). These WPCs are aesthetically pleasing, so a decorative layer may be omitted.

[0044] The support structure can include stone plastic composite (SPC) and / or metal such as aluminum. Like wood plastic composite, SPC is also aesthetically pleasing, so the decorative layer can be omitted. Metals such as aluminum provide additional stability to the support structure while being relatively light, resulting in a strong yet lightweight panel.

[0045] Advantageously, the core layer and / or the panels are substantially free of adhesive. In particular, if the support structure and the porous substrate comprise the same compound, no adhesive layer needs to be provided between the two. Furthermore, in this case, the extruded porous sheets can be bonded together by hot lamination shortly after extrusion without the need to provide adhesive. Adhesives generally release harmful volatile organic compounds. Therefore, the absence of adhesive is a major advantage. In particular, the panels can be connected together by complementary connecting means, such as tongue and groove, without the need for adhesive, even when the panels are installed together to cover a larger surface than a single panel can.

[0046] The core layer may include at least one bio-based plasticizer, such as palm oil, epoxidized soybean oil, castor oil, succinic acid, citrate or any combination thereof. This gives the panel a certain flexibility, which facilitates the installation of the panel. In particular, if the panel has complementary connecting means, the connecting means can be more flexible, thereby facilitating the connection of the panels.

[0047] According to the invention, at least one decorative layer applied in the panel may comprise at least one support layer, for example at least one (high) filled thermoplastic support layer heat-laminated with a thermoplastic decorative layer, an optional wear resistant layer, and an optional UV coating finish. At least one decorative layer, in particular at least one support layer, may comprise or consist of SPC, LVT, extruded, calendered or injection molded thermoplastic.

[0048] The at least one decorative layer, if applied, preferably comprises at least one support layer, at least one decorative layer and / or at least one protective layer. It is conceivable that, if applied, the at least one decorative layer is adhered to the core layer. It is also conceivable that the decorative layer is a printed layer. It is also conceivable that the at least one decorative layer is a printed layer, in particular a digitally printed layer. The decorative layer can also be a component of the support layer. In an advantageous embodiment of the panel, at least a portion of the upper surface of the support layer is provided with at least one decorative pattern or decorative image. For example, such a decorative image or pattern can be provided by printing, for example by digital and / or inkjet printing. It is also possible that at least one decorative pattern is formed by relief on the upper surface of the support layer or the panel. It is also conceivable that the decorative layer or decorative layer is a separate layer, for example a high pressure laminate (HPL), a veneer layer, a directly laminated paper layer and / or a tile. In a preferred embodiment, the at least one decorative layer comprises a thermoplastic film or a cellulose layer. For example, the decorative layer can comprise a plurality of impregnated layers, the impregnated layers comprising wood cellulose, also comprising wood veneers, thermoplastic layers, stone veneers, veneer layers or similar materials and / or combinations of the above materials. The veneer layer is preferably selected from the group consisting of wood veneers, cork veneers, bamboo veneers, etc. Other materials such as ceramic tiles or porcelain, real stone veneers, rubber veneers, decorative plastics or vinyl plastics, linoleum, and laminated decorative thermoplastic materials in the form of foils or films. It is conceivable that the support layer of at least one decorative layer is connected to the support structure of at least one core layer.

[0049] At least one decorative layer may include at least one thermoplastic material. For example, at least one supporting layer of at least one decorative layer may include at least one thermoplastic material. The thermoplastic material may be a bioplastic such as PP, PET, RPET, PVC, PLA, PE, HDPE, LDPE, XPE or thermoplastic starch (TPS). For example, the design of the decorative layer may be selected from a design database including digitally processed designs, traditional patterns, pictures or image files, customized digital artwork, random image patterns, abstract art, wood grain images, ceramic or concrete style images or user-defined patterns. These patterns may be printed or reproduced using a laser printer, an inkjet printer or any other digital printing means (including traditional printing methods). Various types of inks may also be used to meet the design requirements of the decorative layer. Preferably, the ink used in the printing method has, but is not limited to, properties such as water resistance, light resistance, acid-free, metallic, gloss, gloss, glitter or deep black. Ideally, the decorative layer is visually exposed through a coating that is substantially transparent. The decorative layer may include a pattern, wherein the pattern is printed by digital printing, inkjet printing, gravure printing press, electronic spool (ELS) gravure printing press, automatic plastic printing press, offset printing, flexographic printing or rotary printing press. The thickness of the decorative layer is preferably between 0.05 mm and 0.10 mm, for example, approximately 0.07 mm. In a preferred embodiment, the decorative layer includes at least one decorative layer and / or at least one wear-resistant layer. For example, the wear-resistant layer can be a scratch-resistant layer. The decorative layer may include a wear-resistant layer or a finishing layer, for example, a thermosetting varnish or varnish (e.g., polyurethane, PUR or melamine-based resin). In a preferred embodiment, the decorative layer includes at least one substantially transparent wear-resistant layer or finishing layer. The wear-resistant layer may include one or more layers of transparent thermoplastic resin or thermosetting resin. Non-limiting examples of thermoplastic or thermosetting materials that can be used include polyvinyl chloride (PVC), polystyrene (PS), polyethylene (PE), polyurethane (PU), acrylonitrile butadiene styrene (ABS), polypropylene (PP), polyethylene terephthalate (PET), phenolic resin and / or melamine or formaldehyde resin. The wear layer can also be made of a thermosetting resin (such as but not limited to phenolic resin and / or melamine or formaldehyde resin) in liquid or paste form. The wear layer can include or essentially consist of an inherently scratch-resistant thermosetting resin impregnated carrier layer (such as paper or lignocellulose). An advantage of the latter embodiment is that the urea-formaldehyde resin also acts as a relatively scratch-resistant wear layer. Typically, the thickness of the wear layer structure in the panel of the present invention is preferably in the range of 0.1 to 2.0 mm, more preferably between 0.15 and 1 mm, and more preferably between 0.2 and 0.8 mm. The thickness of at least one support layer can be in the range of 0.2 to 2 mm, preferably 0.5 to 1.5 mm.Such an embodiment will provide sufficient body to the panel surface to obtain screw strength and / or screw pull strength. At least one supporting layer of at least one decorative layer is preferably substantially rigid. The rigid supporting layer may provide rigidity and strength to the panel. For example, the rigidity or MOE of at least one supporting layer may be greater than 2000 MPa, preferably greater than 4000 MPa, more preferably greater than 6000 MPa, tested according to EN 310 or according to ISO 24344 at a mandrel of >100 mm.

[0050] The decorative top layer, especially its supporting layer, optionally contains at least one filler. The material of the filler of the decorative layer or its supporting layer may include organic or inorganic materials, including but not limited to cellulose materials, fibrous materials, kraft paper, sawdust, wood chips, wood fibers, long wood fibers, short wood fibers, sand, lime, volcanic ash, plant-based fibers (such as mushroom fibers, cotton fibers, bamboo fibers, gastrodia fibers, pineapple fibers), magnesium compounds, magnesium oxide, magnesium carbonate, limestone, polymeric fibers, glass fibers, carbon-based fibers, polymeric particles, or hollow microspheres or microparticles with a size of 1 to 1000 microns made of, including but not limited to, ceramics, glass, polymers, composite materials or metals. Preferably, the decorative layer or supporting layer includes at least one filler selected from the following groups: minerals (preferably calcium carbonate); pigments, modifiers, fibers (such as glass fibers, wood, straw and / or hemp). The fibers may be loose fibers and / or interconnected fibers to form a woven layer or a non-woven layer. Preferably, the decorative layer further comprises at least one additional filler selected from the group consisting of steel, glass, polypropylene, wood, acrylic, alumina, curaua, carbon, cellulose, coconut, kevlar, nylon, perlon, polyethylene, PVA, asbestos, viburnum and fique. This can further increase the strength of the panel and / or the water resistance and / or fire resistance of the panel.

[0051] In a preferred embodiment, the wear layer or finishing layer may include at least one coating. For example, the at least one coating may include 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. For example, such a coating may be an ultraviolet (UV) or electron beam (EB) curing coating. It is further contemplated that the coating comprises a thermosetting resin and a photoinitiator that is crosslinked by a UV, excimer or electron beam curing process.

[0052] It is further conceivable that at least one decorative layer comprises a tactile texture, preferably with a depth of at least 0.1 mm, more preferably at least 0.3 mm. Such a tactile texture may provide an enhanced visual effect. The enhanced visual effect may also be referred to as embossing. In one possible embodiment of the invention, the texture or embossing may be provided during the production process by means of rotary or plate embossing. At least one wear layer, if applied, may be embossed with a surface texture design. The texture design may be any desired design, such as natural textures of wood, stone, etc. If a tactile structure is applied, it may, for example, have an irregular tactile texture. It is also conceivable that at least one decorative layer has a tactile texture only partially. In another possible embodiment, both the upper surface and the chamfered surface of the decorative layer may have a tactile texture, the depth of the tactile texture preferably being at least 0.1 mm. In particular, when the decorative layer is produced by a lamination process, a single press may be used, which makes it cost-effective to use a press plate with a matching embossing for each decorative pattern in order to obtain a relief pattern matching the decorative pattern on the top surface of the panel.

[0053] The at least one decorative layer may further comprise at least one resin-impregnated paper layer, comprising at least one antimicrobial agent, preferably zinc oxide (ZnO) and / or silver nanoparticles or similar substances. It is also conceivable that the resin composition impregnating the at least one paper layer comprises at least one antimicrobial agent, preferably a metal oxide, such as titanium dioxide (TiO 2 ), zinc oxide (ZnO) or isothiazolinone, zinc pyrithione, thiabendazole and / or silver nanoparticles. In cases where it is desired to use the floor panels or floor coverings made from such panels in commercial, industrial or areas where high hygiene standards are present, the presence of at least one antimicrobial agent may be beneficial. In the case where a wear layer or a covering layer is used, the antimicrobial agent may also be present in the wear layer or the covering layer. The antimicrobial agent may be a component of the decorative layer. Panels with a decorative layer comprising at least one antimicrobial agent are generally better protected against attack by bacteria, fungi, parasites and / or viruses than panels covered with an antimicrobial agent.

[0054] It is advantageous to bond the at least one decorative layer and the at least one core layer together by applying heat and / or pressure. For example, the at least one decorative layer and the at least one core layer may be bonded by thermal bonding and / or thermal lamination. The benefit of thermal bonding is that an intermediate bonding layer between the decorative layer and the core layer may be omitted. The core layer and the decorative layer according to the present invention may be bonded by thermal bonding.

[0055] In another embodiment, the present invention also relates to a panel comprising at least one core layer, the core layer comprising at least one porous substrate and at least one support structure, and optionally at least one decorative layer adhered to the at least one core layer, wherein the at least one core layer comprises a front surface and a rear surface located on opposite sides, wherein at least a portion of the at least one support structure is substantially parallel to the front surface and / or the rear surface, and / or wherein the at least one support structure extends over the entire width and / or length of the at least one core layer. The support structure is preferably an integrated support structure. Any embodiment described in the present application may also apply to this alternative embodiment.

[0056] In another aspect, the present invention relates to a method for preparing a panel, in particular a panel as described above, comprising the following steps:

[0057] a) extruding at least one mixture comprising at least one expandable thermoplastic material, thereby forming at least two porous sheets;

[0058] b) optionally, providing an intermediate layer;

[0059] c) bonding said at least two porous sheets to each other, optionally via said intermediate layer, to provide a stack of porous sheets connected by at least one joint; and

[0060] d) cutting the stack of porous sheets in a direction from one of the porous sheets to another of the porous sheets to provide at least one core layer, the core layer comprising at least one porous substrate and at least one support structure, wherein the at least one porous substrate is constituted by portions of at least two porous sheets, wherein at least a portion of the at least one support structure is constituted by at least a portion of at least one joint connecting portions of the porous sheets; and

[0061] e) bonding at least one decorative layer to the at least one core layer to obtain a panel. This method is particularly advantageous because at least two extruded porous sheets are bonded to each other, either with or without an intermediate layer. After cutting the porous sheet, the joint between the two sheets acts as a supporting structure. Thus, the joint can form a rib-like structure formed by the parts cut from the joint. The resulting panel is usually a flat plate cut from both sides of the porous sheet stack. If the porous sheet itself is also in the form of a flat plate, the resulting core layer also includes partially plate-shaped ribs. In this case, the two opposite outer edges of these ribs are respectively facing the front surface and the rear surface of the core layer, while the largest surface of these ribs may be adjacent to the porous substrate.

[0062] "Porous" in this context refers to a substrate or sheet. A porous substrate or porous sheet consists of a material that contains pores. Cells are voids in the material that encloses the cells, and the cells can have varying volumes. The material that encloses the cells is usually a polymer. In general, an expandable thermoplastic is a material that is capable of expanding by forming cells. These cells can be filled with any type of gas, which can be generated by the thermoplastic material itself as a byproduct of the expansion reaction, or as a separate component in the mixture. A thermoplastic is a polymer material that becomes flexible at high temperatures and solidifies when cooled. The process of cooling and heating a thermoplastic material is to change the thermoplastic material from a solid state to a formable or flexible state, and vice versa, and this process can be repeated almost infinitely.

[0063] The formed core layer and / or the mixture may further comprise at least one additive. For example, the core layer and / or the mixture may comprise at least one expansion agent, such as a foaming agent. Other additives may be catalysts and / or at least one other filler. For example, at least one (auxiliary) filler may be selected from the following group: minerals (preferably calcium carbonate), pigments, modifiers, fibers (such as glass fibers, wood, straw and / or hemp). The fibers (if applied) may be loose fibers and / or interconnected fibers, forming a woven layer or a non-woven layer. It is also conceivable that the core layer and / or the mixture comprises at least one additional filler, the filler being selected from the group consisting of steel, glass, polypropylene, wood, acrylic, alumina, curaua, carbon, cellulose, coconut, kevlar, nylon, perlon, polyethylene, PVA, asbestos, viburnum and fique. The use of any of the above ingredients can further increase the strength of the core layer and thus increase the strength and / or water resistance and / or fire resistance of the panel.

[0064] An embodiment of a panel comprising a plurality of core layers can be envisaged. Where a plurality of core layers are applied, preferably at least one core layer, more preferably each core layer is an extruded core layer. It is further advantageous if at least one core layer, in particular each core layer is at least partially foamed, such a porous core layer. For example, the panel can comprise at least two core layers. The core layer can be directly adhered to another core layer, for example without interference from an adhesive layer. It is conceivable that the thickness of the core layers varies. It is also conceivable that the core layers have different material compositions. For example, it is conceivable that the density of the upper core layer is lower than that of the lower core layer, or vice versa. Each core layer can be a core layer according to any of the embodiments described in the present invention. For example, it is conceivable that each core layer comprises at least one skin layer. The skin layer is also referred to as a shell layer. The skin layer is formed by cooling and expanding the outer surface of the porous substrate. Active or inactive cooling can ensure that the expansion on the outer surface of the porous substrate is suppressed to a certain extent, thereby forming a skin or shell. It is therefore conceivable that two adjacent core layers are connected so that the adjacent skin layers are bonded together to form a complete support structure within the core layer. In a preferred embodiment, at least one core layer is a coextruded core layer. For example, it can be 2 layers or 3 layers of coextruded. In a preferred embodiment, at least one core layer is a coextruded core layer. For example, it can be 2 layers or 3 layers of coextruded.

[0065] It is conceivable that the expansion component present in the mixture will substantially completely decompose, and the decomposition temperature of the expansion component generally depends on the type of expansion component used. For example, the temperature may be in the range of 170 to 190 degrees Celsius. The actual temperature used depends on the specific material composition used and the preferred extrusion conditions.

[0066] From the screw of the extruder to the die block of the extruder, the mixture or melt may be subjected to a plurality of subsequent (axial) temperature zones. The first temperature zone may be in the range of 170 to 190 degrees Celsius, and / or the second temperature zone may be in the range of 190 to 210 degrees Celsius, and / or the third temperature zone may be in the range of 160 to 190 degrees Celsius. For example, the surface temperature of at least one surface of the melt close to the die block may be in the range of 170 to 190 degrees Celsius, preferably in the range of 175 to 185 degrees Celsius, in particular in order to be able to form a protective skin or shell on at least one surface of the extruded porous sheet. For example, the temperature difference between the screw of the extruder and the die, in particular with the die block of the extruder, is at least 20 degrees Celsius, preferably at least 30 degrees Celsius.

[0067] By temperature control and / or pressure control in the extruder die, the foaming composition can be formed into the desired sheet shape. The pressure in the extruder can also be controlled. For example, it is conceivable to control the pressure by adjusting the volume profile of the internal passage of the extrusion die, in particular by controlling the pressure by the height and / or volume of the internal passage.

[0068] The bonding of step e) may comprise laminating the at least one decorative top layer onto the upper core layer surface of the core layer. For example, the at least one decorative top layer may be laminated onto the core layer by bonding the layers. The lamination may be performed using conventional lamination modules or lamination units. By lamination, the use of an adhesive layer may be omitted. For example, it is conceivable to at least partially fuse the at least one core layer and the at least one decorative top layer together.

[0069] The joint is the connection between two materials. When an intermediate layer is provided in step b), the joint can consist of the intermediate layer alone or of the outer surfaces of two porous sheets directly adjacent to the intermediate layer and the intermediate layer in combination. In the absence of an intermediate layer, the joint can consist of two adjacent outer surfaces of two porous sheets. In both cases, the thickness of the joint may vary. The thickness of the joint is usually a few millimeters.

[0070] The cutting direction in step d) is preferably substantially perpendicular to the extrusion direction in step a). This has the advantage that the joints formed in the porous sheet stack can form a support structure for the core layer. Depending on the position where the porous sheet stack is cut, the number of joints and / or the direction of at least part of the support structure can be determined.

[0071] It is conceivable that the coextruded porous sheet is formed into a plurality of individually extruded sheets, called a porous sheet stack, which is then cut into blocks or sheets comprising a plurality of mutually bonded coextruded porous sheet sections, the support structure being formed by adjacent skin layers or shells. The support structure may be formed by reinforcing struts or ribs extending throughout the volume of the core layer.

[0072] In one embodiment, the bonding in step c) and / or step e) comprises thermal lamination. This eliminates the need to use any adhesive. Therefore, the method is more environmentally friendly as there are no harmful volatile organic compounds released by adhesives.

[0073] At least two porous sheets may be cooled before step c). This has the advantage that, due to cooling, the formation of pores on the outer surfaces of the porous sheets and the volume of each pore are reduced. As a result, the density of these outer surfaces is relatively high compared to the density in the center of the porous sheets. Since the outer surfaces of each porous sheet can together form a support structure, the density of the support structure itself is relatively high. The high density of the support structure can effectively increase the strength of the support structure, so that the panel can withstand greater loads.

[0074] At least a portion of the upper surface and / or at least a portion of the lower surface of the porous sheet can be cooled before and / or after the porous sheet leaves the die block of the extruder, preferably substantially directly after the (shaped) porous sheet leaves the die block of the extruder. This step is particularly suitable for forming a (discrete) density gradient in the porous sheet. For example, at least a portion of the upper surface and / or at least a portion of the lower surface of the porous sheet can be cooled, so that the density close to the upper surface and / or close to the lower surface is higher than the average density of the porous sheet. The cooling can in particular lead to the formation of a skin layer, which forms an integral part of the porous sheet.

[0075] It is conceivable that at least a portion of the melt is cooled in the die of the extruder, so that the temperature of the melt is reduced by at least 10 degrees Celsius, preferably at least 20 degrees Celsius, and more preferably at least 25 degrees Celsius. It is also conceivable that the temperature of the melt is reduced by at least 5 degrees Celsius, preferably at least 10 degrees Celsius, when melting in the die block of the extruder. It is conceivable that the temperature of the melt at its top and bottom surfaces is reduced to a temperature substantially equal to or below the decomposition temperature of the expansion component. It is conceivable that the temperature inside the melt not directly exposed to the cooling step is above the decomposition temperature of the expansion component, substantially inside the porous sheet, thereby causing the core layer to expand further. This can produce a beneficial density gradient, wherein at least one surface of the porous sheet has a higher density than the rest. The method may further include: cooling at least a portion of the upper core layer surface and / or at least a portion of the lower core layer surface of the core layer before and / or after the core layer leaves the die block of the extruder, preferably substantially directly after the (formed) core layer leaves the die block of the extruder. This step is particularly suitable for forming a density gradient in the core layer. For example, at least a portion of the upper core layer surface and / or at least a portion of the lower core layer surface of the core layer may be cooled so that the density near the upper core layer surface and / or near the lower core layer surface is higher than the average density of the core layer. The cooling step may in particular result in the formation of a skin layer, which constitutes an integral part of the core layer.

[0076] It is envisioned that at least a portion of the melt is cooled in the die of the extruder to reduce the temperature of the melt by at least 10 degrees Celsius, preferably at least 20 degrees Celsius, and more preferably at least 25 degrees Celsius. It is also envisioned that the melt is treated in the die block of the extruder to reduce the temperature of the melt by at least 5 degrees Celsius, preferably at least 10 degrees Celsius. It is envisioned that the temperature of the melt at its top and bottom surfaces is reduced to a temperature substantially equal to or below the decomposition temperature of the blowing agent composition. It is envisioned that the temperature inside the melt not directly exposed to the cooling step is above the decomposition temperature of the blowing agent composition, substantially inside the core layer, thereby causing the core layer to expand further. This can form a favorable density gradient, i.e., at least one surface of the core layer has a higher density than the rest of the porous board.

[0077] Preferably, at least two porous sheets can be extruded simultaneously. Another advantage of this is that the porous sheets will automatically stack together during the production process. In addition, when the porous sheets leave the extruder, they have a higher temperature. Therefore, the porous sheets can adhere to each other and automatically form a joint without introducing additional heat or pressure.

[0078] In one embodiment, the at least two porous sheets may be at least 10 porous sheets, preferably at least 15 porous sheets, even more preferably at least 20 porous sheets, and most preferably 30 to 50 porous sheets. The greater the number of porous sheets, the greater the surface area of ​​the panel. Simultaneous extrusion of the porous sheets is particularly advantageous because the lamination of the porous sheets can be performed as part of the extrusion process rather than in a separate hot lamination process.

[0079] In addition, the method also includes: before the bonding in step e), at least two core layers are bonded to each other, wherein the extension direction of the support structure of at least one of the at least two core layers is at a certain angle to the extension direction of the support structure of at least another of the at least two core layers. It is particularly advantageous if ribs or ribs with a plate-like shape are formed in the core layer. The first core layer of the support structure containing or consisting of such ribs can be rotated about 90 degrees relative to another such core layer. The two core layers are bonded together to form a combined core layer, and the combined core layer has an overall support structure, and when viewed from the front surface of the combined core layer to the rear surface of the combined core layer, the overall support structure has a grid-like structure. The core layer can also be rotated at an angle other than 90 degrees. It is also possible to combine multiple core layers, for example three. In the case of combining three core layers, the rotation angle of each core layer relative to the core layer directly above or below can be 60 degrees. Looking from top to bottom, a grid containing triangular porous substrate components is formed.

[0080] The mixture may include an expansion agent or expansion component, such as supercritical CO 2 This expansion agent helps to form the cells in the porous sheet. The expansion agent can be added separately as part of the mixture or it can be generated in a chemical reaction initiated by the mixture after extrusion.

[0081] In a preferred embodiment, at least one expansion component comprises azodicarbonamide (C 2 H 4 N 4 O 2 ) and / or sodium bicarbonate (NaHCO 3). It has been found that the above compounds are suitable for use as expansion agents. The foaming agent can be added to the mixture at up to 1% of the total weight of the mixture, preferably up to 0.8wt%. In particular, for sodium bicarbonate, it is required to apply the compound in an appropriate amount, because too much sodium bicarbonate will cause the pores of the porous sheet to collapse, thereby producing a denser porous structure. It has been found that the density of the porous sheet decreases almost linearly with the increase in the amount of sodium bicarbonate. In a preferred embodiment, the amount of expansion agent added is 0.3 to 0.5wt% of the total weight of the mixture.

[0082] Alternatively, or in addition, for example, at least one expansion agent may include N,N'-dinitroso-N,N'-dimethyl terephthalamide, N-aminophthalimide 4,4'-oxybis(benzenesulphonylhydrazide), N,N'-dinitrosopentamethylenetetramine, Azoisobutyric dinitrile, Diazoaminobenzene, Dinitropentamethylenetetramine, Benzenesulfohydrazide, Terephthalylbis(N-nitrosomethylamide) bis(N-nitrosomethylamide), toluene-2,4-bis(sulfonylhydrazide), p-tertiary butylbenzazide), p-carbomethoxy benzazide, diarylpentaazadiene and / or 3-methyl, 1,5-diphenylpentaazadiene. At least one expansion agent may be an exothermic expansion agent or an endothermic foaming agent. The expansion agent may also be referred to as a foaming agent.

[0083] It is beneficial to add at least one expansion catalyst to the mixture. Non-limiting examples of expansion catalysts that can be added to the mixture include: calcium oxide, carbamide, zinc 2-ethylhexanoate, zinc benzenesulfinate, zinc carbonate, zinc ditolyl sulfinate, zinc oxide, zinc stearate, calcium / zinc esters, barium / zinc esters, potassium / zinc esters, dibutyltin bis(iso-octylmaleate) and / or dialkyltin bis(alkylthioglycollates).

[0084] In one embodiment, before step e), a sealing strip can be heat-laminated with at least a portion of at least one core layer. The sealing layer can be heat-laminated with the outer edge of the core layer. The sealing strip thus has an edge sealing function. Another advantage of this is that the porous structure of the porous substrate and optionally part of the porous structure of the support structure are sealed. This prevents dirt from accumulating or moisture from the surrounding environment from being absorbed into the core layer. A separate sealing strip can be used. Such a sealing strip can consist of the same material as the core layer or a different material. Advantageously, the sealing strip does not contain porous material. It is also conceivable that at least a portion of at least one core layer is heated so as to form a shell that is essentially free of bubbles and has a higher density. Another advantage of the heat-laminated layer is that no separate adhesive is required. In addition, screws can be inserted into the sealing strip or the formed shell, because this part of the core layer has a higher density and is therefore very suitable for fixing the screws. The sealing strip or the shell can also be processed as a snap-on system.

[0085] In another aspect, the invention relates to a system for applying the above method, comprising: at least one extruder for extruding expandable thermoplastic material, the extruder comprising a plurality of extrusion dies; and a conveyor for conveying the extruded thermoplastic material; wherein the plurality of dies and / or die blocks are arranged parallel to each other, wherein the extrusion direction of each die is substantially the same. The system allows the simultaneous manufacture of porous sheets that can be thermally laminated to each other. The system has all the above advantages.

[0086] Preferably, the system comprises a cooler for cooling the extruded thermoplastic material. In particular, by adjusting the amount of cooling on the outside of the extruded thermoplastic material, the thickness of the outer surface of the porous sheet can be adjusted as required. When the porous sheet is stacked, the joints thus created can be adjusted according to the required strength and / or weight of the support structure, as well as the support structure in the core layer.

[0087] A plurality of moulds and / or mould blocks can be stacked on top of each other. Thus, the porous sheets can advantageously be automatically stacked together. When the porous sheet stack needs to be cut, the system can include a cutting element for cutting the porous sheet stack. In this way, the cutting can be done inline by the system itself without a separate cutting device. The cutting position can be adjusted according to the required thickness of the core layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0088] The present invention will now be described based on the non-limiting exemplary embodiments shown in the following drawings. In the drawings:

[0089] Figure 1 A panel according to a first possible embodiment of the present invention;

[0090] Figure 2a , 2b 2c and 2d are possible methods for producing panels according to the present invention;

[0091] Figure 3 A panel according to a third possible embodiment of the present invention;

[0092] Figure 4a , 4b , 4c and 4d are side views of panels according to possible embodiments of the present invention;

[0093] Figure 5a and 5b A panel according to a further possible embodiment of the invention; and

[0094] Figure 6a and 6b A panel according to a further possible embodiment of the invention is shown.

[0095] In these drawings, the same reference numbers refer to similar or equivalent technical features or elements. DETAILED DESCRIPTION

[0096] Figure 1A panel 100 according to a first possible embodiment of the invention is shown. The panel 100 is in particular a decorative panel and / or a structural panel 100. The embodiment shown in the figure comprises a core layer 101 and a decorative layer 102. The decorative layer 102 is adhered to the core layer 101, in particular to the front surface of the core layer 101. In the figure, only a part of the decorative layer 102 is shown in order to observe the core layer 101 in more detail. The core layer 101 comprises a porous substrate 103 and a support structure 104. The core layer 101 comprises a front surface and a rear surface located on opposite sides, wherein the thickness T of the core layer is defined by the distance between the front surface and the rear surface. As can be seen from the figure, a part of the support structure 104 extends over the thickness T of the core layer 101. In the embodiment shown, the support structure 104 comprises a plurality of ribs 104a, which extend over the thickness T of the core layer 101. The ribs 104a are positioned substantially parallel to each other and are defined at an angle of approximately right angles relative to the front surface and the rear surface of the core layer. In the embodiment shown, the ribs 104a are at a distance from each other. In fact, the ribs 104a in the embodiment shown are independent ribs 104a embedded in the porous substrate 103. Optionally, the panel may also include connecting elements and / or other layers adhered to the decorative layer 102 and / or the core layer 101.

[0097] Figures 2a to 2d A process or method for producing a panel 200 according to one possible embodiment of the invention is shown. Figure 2a An intermediate product produced by an extrusion process is shown. The arrow indicates the extrusion direction E. Figure 2a A plurality of interconnected porous sheets 250 produced by an extrusion process are shown. In the embodiment shown in the figure, the plurality of porous sheets 250 are produced by extruding at least one mixture comprising at least one expandable thermoplastic material. Figure 2a As shown, the porous sheets 250 are bonded to each other through an intermediate layer to form a porous sheet stack 250. The porous sheets 250 are connected by joints 251. Figure 2b As shown, the porous sheet stack 250 is subsequently cut to form the core layer 201 of the present invention. Figure 2a A cutting line C is shown, which is directed from one porous plate sheet 250 to another porous plate sheet 250. It can be seen that the cutting direction is substantially perpendicular to the extrusion direction. By this cutting step, a core layer 201 is formed, which includes a porous substrate 203 and a support structure 204, wherein the porous substrate 203 is composed of at least two porous plates 250a, and at least a portion of the support structure 204 is composed of at least a portion of at least one joint 251a connecting the porous plates 250a. Step 2c shows the provision of a plurality of decorative layers 202. In the embodiment shown, two decorative layers 202 are adhered to the core layer 201. Figure 2dA panel 200 manufactured according to the invention is shown, on which complementary connecting parts 230a, 230b are provided. Figure 2d A side view of the panel is shown.

[0098] Figure 3 A picture of a panel 300 made according to the present invention is shown. The panel 300 comprises a core layer 301, which comprises a porous substrate 303 and a support structure 304. The porous substrate 303 is an extruded PET substrate 301, and the support structure 304 is an integral part of the porous substrate 303. Thus, the core layer 301 is formed by extrusion. The support structure 304 is defined by a plurality of ribs 304a, which are integrally formed in the porous substrate 303.

[0099] Figure 4a , 4b , 4c and 4d show side views of panels 400a, 400b, 400c and 400d according to a possible embodiment of the invention. These panels may optionally be provided with connection means.

[0100] Figure 4a A panel 400a is shown comprising a core layer 401, the core layer 401 comprising a porous substrate 403 and a support structure 404. The embodiment shown comprises two decorative layers 402a, 402b, respectively adhered to opposite sides of the core layer 401. The support structure 404 extends over the thickness T of the core layer 401. In the embodiment shown, the support structure 404 is a triangular structure. Adjacent ribs 404a of the support structure 404 are defined as triangles. The legs of each triangle extend from the front surface of the core layer 401 to the rear surface. In the embodiment shown, the ribs 404a are connected to each other. However, it is also conceivable that the ribs of the triangular support structure are kept at a certain distance from each other.

[0101] Figure 4b An embodiment of a panel 400b comprising two core layers 401a, 401b is shown. The upper core layer 401a comprises a porous substrate 403 and a support structure 404. The lower core layer 401b comprises a porous substrate 403b. The lower core layer 401b has no reinforcing structure. The panel 400b also comprises three decorative layers 402a, 402b, 402c, which at least wrap a portion of the core layers 401a, 401b. The density of the upper core layer 401a is lower than that of the lower core layer 401b. The front surface of the upper core layer 401a and the sides of the combined core layers 401a, 401b are provided with decorative layers 402a, 402b, 402c, respectively.

[0102] Figure 4cA panel 400c is shown, which includes a core layer 401 and a decorative layer 402 connected to the front surface of the core layer 401. The core layer 401 includes a porous substrate 403 and a support structure 404. The porous material of the porous substrate 403 is located inside the support structure 404. The support structure 404 provides support for the porous substrate 403 and the panel 400c.

[0103] Figure 4d A panel 400d is shown, comprising a core layer 401 and a decorative layer 402a adhered to the front surface of the core layer 401 and a decorative layer 402b adhered to the rear surface of the core layer 401. The core layer 401 also comprises a support structure 404. The support structure 404 is integrally formed in the porous substrate 403. It can be seen that the density of the porous material of the porous substrate 403 is lower than the density of the porous material of the support structure 404. The support structure 404 is formed by a shell layer, which is formed by a portion of the porous material of the porous substrate 403. It is conceivable that there is a density gradient between the support structure 404, in particular its ribs, and the substrate 403.

[0104] Figure 5a and 5b Panels 500a and 500b are shown as possible embodiments according to the invention.

[0105] Figure 5a A cross-sectional view and an assembly view of a panel 500a are shown, and the panel 500a includes a core layer 501, a secondary support structure 540, and a decorative layer 502 formed by decorative printing. The decorative printing is provided by printing (e.g., digital printing or inkjet printing). The upper half of the figure schematically shows a printing device 580 and a printing step. The secondary support structure 540 is an additional layer of the core layer 501. The secondary support structure 540 is defined as a honeycomb structure and a double-walled structure. Sheets 540a and 540b wrap the honeycomb structure 540c to form a double-walled structure. For example, the honeycomb structure 540c can be made of a material different from the sheets 540a and 540b that wrap the honeycomb structure 540c. For example, the honeycomb structure 540c can be made of metal, particularly aluminum, and the sheets 540a and 540b can be made of polymers. The core layer 501 includes a porous substrate 503 and a support structure 504.

[0106] Figure 5b A panel 500b according to another embodiment of the present invention is shown. The panel 500b comprises a core layer 501, the core layer 501 comprising a porous substrate 503 and a support structure 504, and two decorative layers 502a, 502b wrapping the core layer 501. The support structure 504 is defined as a honeycomb structure. The support structure 504 is filled with a porous material to form a porous substrate 503.

[0107] Figure 6a and 6bPanels 600a and 600b according to other possible embodiments of the present invention are shown. Figure 6a Exploded and perspective views are shown. Figure 6b A partially exploded view is shown.

[0108] Figure 6a The upper part of the figure shows a front view and an exploded view of the panel 600a, and the lower part shows the final structure or combined view of the panel. The panel 600a includes a core layer 601 and a plurality of decorative layers 602, which are laminated together with the core layer 601, and each decorative layer 602 includes a support layer 602a, a decorative layer 602b and a wear-resistant layer and / or a protective layer 602c. The core layer 601 includes a porous material. The core layer 601 particularly includes a porous substrate 603. It can be seen that the material of the core layer 601 is a porous material with different densities. A density gradient is basically presented on the core layer 601. The bubbles near the surface of the core layer 601 are smaller, indicating a higher density, and the bubbles near the middle of the core layer 601 are larger, indicating a lower density. Near the edge of the core layer 601, the bubbles are relatively small, indicating that the density on this side is higher, which is caused by the thermal lamination on the edge. According to the present invention, the core layer 601 is optionally equipped with a support structure.

[0109] Figure 6b A panel 600b according to another possible embodiment of the present invention is shown. The panel 600b, in particular the core layer 601, comprises a plurality of ribs 604a defining a support structure 604. The support structure 604 is embedded in a porous substrate 603. All six surfaces of the panel 600b comprise a decorative layer 602. In the embodiment shown, the decorative layer 602 comprises a wood design. Each decorative layer 602 may comprise a stack of functional layers, such as at least one support layer, a decorative layer, a wear layer and / or a protective layer.

[0110] Obviously, the present invention is not limited to the working examples shown and described herein. Instead, many variations are possible within the scope of the appended claims. These variations will be obvious to a person skilled in the art.

[0111] The verb "to comprise" and its conjugations as used in this patent publication are understood to mean not only "to include", but are also understood to mean the phrases "including", "consisting essentially of", "formed of", and their conjugations.

Claims

1. A panel, characterized in that: The panel comprises: At least one core layer, the core layer comprising: at least one porous substrate, and at least one support structure; and at least one decorative layer adhered to the at least one core layer; wherein the at least one core layer comprises a front surface and a rear surface located on opposite sides, wherein the thickness of the at least one core layer is defined by the distance between the front surface and the rear surface, and wherein at least a portion of the at least one support structure extends over the thickness of the at least one core layer.

2. The panel according to claim 1, wherein At least a portion of the at least one support structure extends over the entire thickness of the porous substrate of the at least one core layer, and / or wherein the at least one support structure comprises a plurality of ribs, wherein at least one of the ribs extends over the thickness of the at least one core layer, preferably each of the ribs extends over the thickness of the at least one core layer.

3. The panel according to claim 1 or 2, wherein: At least a portion of the at least one support structure is positioned at an angle relative to a plane defined by the front surface and / or the back surface of the at least one core layer.

4. A panel according to claim 2 or 3, wherein: At least two of the ribs are substantially parallel to each other.

5. A panel according to any one of the preceding claims, wherein The panel comprises at least two of the core layers, wherein each of the core layers comprises the at least one porous substrate and the at least one support structure, wherein a first support structure of a first core layer is arranged at an angle relative to a second support structure of a second core layer.

6. A panel according to any one of the preceding claims, wherein At least a portion of the at least one support structure is embedded in the at least one porous substrate; And / or wherein at least a portion of the at least one support structure forms an integral part of the at least one porous substrate.

7. A panel according to any one of the preceding claims, wherein At least a portion of the at least one support structure is defined by a honeycomb structure and / or a double wall and / or a lattice structure.

8. A panel according to any one of the preceding claims, wherein The at least one core layer is an extruded core layer and / or wherein the at least one porous substrate is an extruded substrate.

9. A panel according to any one of the preceding claims, wherein The core layer includes at least one side edge, wherein the at least one decorative layer is adhered to the at least one side edge.

10. A panel according to any one of the preceding claims, wherein The panels include connecting parts that mate with each other.

11. A panel according to any one of the preceding claims, wherein The compressive strength of the support structure is higher than the compressive strength of the porous substrate as measured in the direction from the front surface to the back surface of the core layer according to ASTM-D1037.

12. A panel according to any one of the preceding claims, wherein The at least one porous substrate and / or the at least one supporting structure comprises a thermoplastic polymer or a thermosetting polymer, preferably selected from polyvinyl chloride (PVC), polystyrene (PS), polyethylene (PE), high-density polyethylene (HDPE), low-density polyethylene (LDPE), cross-linked polyethylene (XPE), polyurethane (PU), acrylonitrile butadiene styrene copolymer (ABS), polypropylene (PP), polyethylene terephthalate (PET), thermoplastic starch (TPS), cross-linked polystyrene (XPS), styrene acrylonitrile copolymer (SAN), polyphenylene ether (PPO), polylactic acid (PLA), phenolic resin, melamine resin, formaldehyde resin or any combination thereof.

13. A panel according to any one of the preceding claims, wherein The density of the at least one porous substrate has a density gradient.

14. A panel according to any one of the preceding claims, wherein The density of the core layer is in the range of 80 to 1000 kg / m 3 , preferably 100 to 1000 kg / m 3 , more preferably 300 to 1000 kg / m 3 , for example about 600kg / m 3 .

15. A panel according to any one of the preceding claims, wherein The at least one porous substrate and / or the at least one supporting structure comprises a wood plastic composite (WPC) and / or a foamed thermoplastic.

16. A panel according to any one of the preceding claims, wherein The at least one support structure comprises a rigid thermoplastic composite, a rigid thermoset composite, a stone plastic composite (SPC) and / or a metal, such as aluminum.

17. A panel according to any one of the preceding claims, wherein The at least one core layer is substantially free of adhesive and / or the panel is substantially free of adhesive.

18. A method for preparing a panel, in particular a panel according to any one of claims 1 to 17, the method comprising the following steps: a) extruding at least one mixture comprising at least one expandable thermoplastic material, thereby forming at least two porous sheets; b) optionally, providing an intermediate layer; c) bonding the at least two porous sheets to each other, optionally via an intermediate layer, to provide a stack of porous sheets connected via at least one joint; as well as d) cutting the stack of porous sheets in a direction from one porous sheet to another porous sheet to provide at least one core layer, the core layer comprising at least one porous substrate and at least one support structure, wherein the at least one porous substrate is constituted by parts of at least two porous sheets, wherein at least a part of the at least one support structure is constituted by at least a part of at least one joint connecting parts of the porous sheets; and e) bonding at least one decorative layer to at least one core layer to obtain a panel.

19. The method according to claim 18, wherein: The cutting direction in step d) is substantially perpendicular to the extrusion direction in step a); and / or, said bonding in step c) and / or step e) comprises a thermal lamination process.

20. The method according to any one of claims 18 to 19, wherein: The at least two porous sheets are extruded simultaneously.

21. The method according to any one of claims 18 to 20, wherein: The method also includes a step of bonding at least two of the core layers to each other before bonding in step e), wherein the extension direction of the support structure of at least one of the at least two core layers is arranged at an angle to the extension direction of the support structure of at least another of the at least two core layers, preferably, wherein the mixture contains an expansion agent, such as supercritical CO2.

22. The method according to any one of claims 18 to 21, wherein: Prior to step e), a sealing strip is heat laminated to at least a portion of the at least one core layer.

23. A system using the method of any one of claims 18 to 22, wherein: The system comprises: at least one extruder for extruding an expandable thermoplastic material, the extruder comprising a plurality of extrusion dies; and Conveyors for conveying extruded thermoplastic materials; wherein a plurality of said molds and / or mold blocks are arranged parallel to each other, and Wherein, the extrusion direction of each of the dies is substantially the same.

24. The system of claim 23, wherein: The plurality of dies and / or the die blocks are stacked on top of each other.

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