CN119459091A

CN119459091A - Panel and method for manufacturing a panel

Info

Publication number: CN119459091A
Application number: CN202311870974.0A
Authority: CN
Inventors: T·L·M·贝尔; T·范波耶; S·伯恩
Original assignee: Chinafloors Timber China Co ltd
Current assignee: Chinafloors Timber China Co ltd
Priority date: 2023-08-11
Filing date: 2023-12-29
Publication date: 2025-02-18
Also published as: WO2025036845A1

Abstract

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

Description

Panel and method for manufacturing a panel

Technical Field

The present invention relates to a panel. The invention also relates to a method of manufacturing a panel. The invention also relates to a system adopting the method.

Background

Building and/or decorative panels, which are commonly used as furniture, shelves, floors, door panels and building boards, are often based on wood, particleboard, high Density Fiberboard (HDF), medium Density Fiberboard (MDF), oriented Strand Board (OSB), plywood and the like constituting the core of the panel. However, these wood panels have several drawbacks. Since these boards are typically made of Melamine Urea Formaldehyde (MUF) and/or phenol based resins as binders, this has raised concerns about Volatile Organic Compounds (VOCs) and indoor air quality. Being wood panels they are susceptible to humidity fluctuations and water, which may lead to warping and delamination. Sealing the edges of the panels with decorative foil requires the use of an adhesive which may leak and be visible at the seams. Wood panels often have anisotropy, and depending on the measuring axis, the material has different physical properties, such as stiffness, expansion and/or expansion, which may have an adverse effect when providing fastening means. Wood panels may have local defects, such as cracks or knots, which may affect their local strength.

Disclosure of Invention

It is an object of the present invention to provide an improved panel for use as a furniture, shelf, floor, door panel and building board, which overcomes at least some of the above-mentioned drawbacks or at least finds an alternative to the known panels.

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

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 support structure. The combination of the porous substrate according to the invention and the at least one support structure may form a relatively strong core layer. An advantage of the core layer is that at least a portion of the at least one support structure extends over the thickness of the at least one core layer, thereby obtaining a robust geometry. Thus, the at least one support structure may constitute a skeleton structure of the panel. The support structure may also be referred to as a skeletal structure. Since the at least one support structure extends over the thickness of the at least one core layer, a relatively thin porous substrate may be used. The orientation of at least a portion of the support structure provides rigidity to the porous substrate. Thus, the core layer benefits from the porous material and the support structure. The panels of the invention have in particular good rigidity and strength.

In the present invention, the panel may be any panel suitable for decoration and/or construction. Thus, the panel may be a decorative panel and/or a structural panel. For example, according to the present invention, the panels may be configured and/or adapted for use with furniture, shelves, door panels, but may also be decorative and non-decorative building panels, floors, walls and/or ceilings. The panel may be, for example, a floor, a wall or a ceiling. When referring to a porous substrate, reference may also be made to a substrate comprising a porous material. One non-limiting example of a porous material is, for example, a foamed material. The panel according to the invention may thus comprise at least one at least partially foamed core layer. For example, it is conceivable that the panel comprises a foamed thermoplastic core, such as foamed PVC, foamed PET, foamed PP and/or foamed WPC, a foamed thermosetting core, such as foamed TPU and/or PU foam, and/or a foamed inorganic core, such as MgO, mgSO ₄、MgCl₂, fibre cement and/or aluminosilicate. It is also conceivable that the panel comprises an organic core, for example comprising cork, mycelium or the like. The core layer is preferably a waterproof core layer. The panel is preferably a waterproof panel.

It is conceivable that at least a portion of the front and rear surfaces of the core layer are formed by the support structure. It is also conceivable that 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. The panels and the substrate may have a variety of possible shapes. For example, the panel and/or the substrate may 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 advantageous 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 the at least one support structure extends over a minimum thickness of the at least one core layer. The core layer may have a variable thickness. For example, it is conceivable that at least a portion of the at least one support structure forms a connection or 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 the at least one support structure is angled with respect to a plane defined by the front surface and/or the rear surface of the core layer. One embodiment is envisaged in which at least a portion of the at least one support structure is substantially perpendicular to a plane defined by the front and/or rear surface of the at least one core layer. When reference is made to the front and rear surfaces, this may also be the first (side) surface and the second (side) surface. Particularly the opposite side of the panel. According to the invention, the panel can be applied in a plurality of directions. Accordingly, the terms "front" and "rear" should not be construed as limiting. For example, upper and lower, first and second, primary and secondary may also be used instead of the terms front and rear. The upper and lower sides, or front and rear sides, are typically two opposing faces with the greatest surface area, which serve as the primary decorative faces. For example, the panels are substantially rectangular. However, the panels according to the invention may have any convenient shape. For example, it is conceivable that the panel is a cuboid or hexahedron, in particular comprising a plurality of faces.

The 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 3mm and 20mm or between 5mm and 16mm, preferably between 6mm and 8mm or between 14mm and 16 mm. One advantageous embodiment comprises a core layer having a thickness in the range of 2.5 to 4mm or in the range of 3.5 to 5 mm. In case the panel comprises a plurality of core layers, it is also conceivable that the core layers have different thicknesses. For example, it is conceivable that the core layer is composed of a thickness of between 3 and 12 mm. It is conceivable that the panel has a plurality of core layers, wherein at least one core layer has a thickness in the range of 0.5 to 1mm and at least one other core layer 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 the central core layer is enclosed between the upper core layer and the lower core layer. It may be preferred that the upper and/or lower core layers have a greater thickness than the central core layer and vice versa. For example, the thickness of the at least one support structure may be substantially equal to the thickness of the core layer.

In a preferred embodiment, the at least one support structure or the at least one skeletal 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, the at least one rib or ribs may form a reinforcing structure within the core layer, in particular within the porous substrate. It is also conceivable that the at least one support structure comprises a plurality of struts. When referring to ribs, it may also refer to struts and vice versa. In a preferred embodiment, at least one rib, preferably at least two ribs, more preferably each rib extends over the entire thickness of the porous substrate of at least one core layer of the at least one support structure. At least two of the 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 may contribute to a good stiffness of the core layer and the panel. It is possible that at least two ribs or a plurality of 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 of a 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 be defined as triangular shaped, e.g. wherein the legs of the triangle extend from the front surface to the back surface of the core layer or vice versa. It is also conceivable that at least two ribs are substantially parallel in a length direction corresponding to the panel.

In one possible embodiment, at least two ribs of at least one support structure may be interconnected. It is thus conceivable that at least one support structure is formed by a plurality of substantially adjacent and/or parallel ribs being interconnected. The 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 made up of a plurality of individual ribs. For example, a plurality of individual ribs may together form a support structure. It is also conceivable that the core layer comprises a plurality of support structures. The orientation and/or position of the at least one support structure and/or the at least one rib (preferably a plurality of ribs) helps to enhance the rigidity characteristics of the core.

Advantageously, the strength of the panel is significantly improved due to the presence of the support structure in the core. Several aspects of the panel can be measured. The American society for testing and materials (American Society for TESTING AND MATERIALS) provides a standard test method ASTM D1037-96 for evaluating the performance of wood fiber and particle board materials. Including flexural modulus of elasticity (MOE) and modulus of rupture (MOR). Other useful tests included in ASTM D1037-96 include direct screw pullout tests, hardness tests, modulus of hardness tests, board plane shear strength, glue line shear tests, ball drop impact tests. ANSI/KCMA A161.1 kitchen furniture testing may be particularly useful if the panel is used as part of a furniture product.

When testing a three layer porous polyethylene terephthalate (PET) core layer (including the support structure) having an average density of 250kg/m ³, there is a significant difference between modulus of rupture (MOR) and modulus of elasticity (MOE) if the direction of extension of the support structure is considered. MOE and MOR were tested according to ASTM D1037-96. These three-layer panels are porous sheets comprising polyethylene terephthalate (PET) comprising cells or voids. The cell volume of the support structure in each panel is on average smaller than the cell volume of the surrounding porous substrate. Thus, in this test, the support structure of each panel was composed of PET, which has a relatively high density compared to the average density of the panels.

The support structure is a rib extending linearly parallel throughout the core layer, thus dividing the porous substrate into two portions, wherein the two portions are located on opposite sides of the rib. The ribs themselves are in the form of beams or plates. In the first core, the MOE is tested in a direction from the front and back surfaces on opposite sides of the core, with a single rib (support structure) extending across the core parallel to the front and back surfaces. Thus, the direction of force is perpendicular to the direction of the plane in which the ribs extend. The MOE of the first core layer was 82.3MPa and MOR was 3.5MPa.

In the second porous PET core, similar ribs extend across the core perpendicular to the front and back surfaces of the core. 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. Thus, the direction of the force used to measure the MOE and MOR is the same as the direction of extension of the ribs. The MOE and MOR were measured to be almost doubled, reaching 176MPa and 5.7MPa, respectively.

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

For a core layer with an average density of 250kg/m ³, the average strength of the porous PET comprising the (integrated) support structure appears to be between 170 and 200MPa, while the average strength of the expanded PET without any support structure appears to be between 70 and 90 MPa. "integration" as described herein is defined as a portion of the core layer, in this case consisting of the same compound as the porous substrate itself.

If the core layer is made of a Wood Plastic Composite (WPC), the average MOE value is between 400 and 800MPa, preferably between 500 and 700MPa, for example 600MPa without a support structure. If there is a support structure having the same shape and orientation as the support structure in the second or third porous PET core layer, the average MOE value is between 1200 and 1800MPa, preferably between 1350 and 1650MPa, for example 1500MPa.

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

In a 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 support structure. It is conceivable that the first support structures of the first core layer are arranged at an angle with respect to the second support structures of the second core layer. Each core layer may be any of the embodiments of core layers described in accordance with the present 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 an angle with respect 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.

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 are oriented and/or positioned such that the support structure has rigid features. It is conceivable that at least a part of the support structure forms a grid structure.

In one possible embodiment of the panel according to the invention, at least a part of the at least one support structure is embedded in the at least one porous substrate. Thus, at least a portion, preferably the entire, of at least one support structure is embedded in the porous material comprising the porous substrate. In this way, the at least one support structure may form part of the core layer in an efficient and controllable manner. Embedding at least a portion of the support structure into the at least one porous substrate may enhance the synergy between the support structure and the porous substrate. For example, it is envisioned that at least a portion of the at least one support structure is attached to at least a portion of the at least one porous substrate by an adhesive. It is also possible that at least a portion of the at least one support structure is attached to at least a portion of the at least one porous substrate by lamination, in particular thermal lamination. In this embodiment, the material of the support structure is typically different from the material comprising the porous substrate. It is conceivable that the support structure and the substrate are made of the same material.

It is also conceivable that at least a part of the at least one support structure forms an integral part of the at least one porous substrate. In this way, the core layer may benefit from an integrally formed support structure that may provide strength and rigidity from the core of the core layer, particularly the core of the porous substrate. The integrally formed support structure is not prone to weak points at the joints and/or junctions. For example, the support structure may be an integrated support structure, wherein in particular the support structure is integrated in the porous material of the porous substrate. For the present embodiment, the support structure is preferably made of the same material as the porous substrate. The support structure may be formed during the core layer formation process.

It is conceivable that at least a portion of the at least one support structure is defined as a honeycomb structure, a bubble guard, a corrugated plate, a corrugated structure and/or a double wall structure. At least a portion of the at least one support structure defining any of the structures described above may further contribute to the strength and/or rigidity of the panel. For example, it is conceivable that the walls of the honeycomb structure, bubble guard, corrugated plate, corrugated structure and/or double-walled structure extend over the thickness of the core layer. It is also conceivable that the walls defining the honeycomb structure, the bubble protection sheet, the corrugated structure and/or the double-walled structure extend at an angle, in particular substantially perpendicular to the plane defined by the front and/or rear surface of the panel, preferably substantially perpendicular to the plane defined by the front and/or rear surface of the core. For example, the honeycomb may be an aluminum honeycomb and/or a thermoplastic honeycomb. However, another embodiment is also conceivable, wherein the panel comprises at least one additional support structure or secondary support structure. The at least one secondary support structure may be a separate layer than the at least one core layer. It is also conceivable that at least one secondary support structure forms part of at least one core layer. The at least one secondary support structure may be defined as any one of the embodiments of the support structure according to the invention. Further embodiments are also contemplated wherein at least a portion of the at least one support structure is defined as a grid. The support structure preferably extends over the entire core of the covering 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.

The provision of at least one support structure on the front and/or rear surface of the panel may increase the stiffness of the panel, and the support structure is therefore preferably substantially rigid. The use of at least one support structure according to the invention may further increase the screw pullout strength, allowing a more secure fastening means between the panels.

In a preferred embodiment, at least one of the core layers is an extruded core layer. In a preferred embodiment, the at least one porous substrate is an extruded substrate. In some embodiments, the extruded substrate comprises at least two simultaneously extruded materials. The panel according to the invention may also be an extruded panel. Extrusion is a preferred method of production because it is relatively cost competitive and enables continuous mass production. For example, a panel according to the invention may be produced by a method according to the invention. It is conceivable that the core of the panel is made by co-extrusion layers forming a plurality of individually extruded layers, which layers are then cut into pieces or sheets comprising a plurality of co-extruded core layers bonded to each other, the reinforcement layer being formed by said adjacent skin layers or shells, the reinforcement struts or ribs being formed throughout the volume of at least one core layer. The at least one support structure may have a ribbed structure extending to the core layer, for example formed by a specially shaped extrusion die. It is contemplated that the porous material may be co-extruded with the top and/or bottom layers, or the front and/or back layers, both having rib structures extending to the core layer, the porous material being formed in grooves formed by the rib structures.

The core layer or porous substrate may also be obtained by multilayer extrusion. It is envisioned that the core layer or porous substrate will be composed of a variety of materials. For example, at least one core layer or at least one porous substrate may be composed of alternating materials. For example, at least one core layer or porous substrate may comprise an alternating sequence of a first polymeric material and a second polymeric material, e.g., configured with (-SPC-WPC-). N, where n is an integer ≡1.

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 that 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 the at least one core layer and the 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 of the embodiments of the decorative layer described herein, the first decorative layer and/or the second decorative layer may be applied, if applicable.

The at least one core layer may include at least one side edge, and the at least one decorative layer may be adhered to the at least one side edge. In such embodiments, the panel may be used, for example, for decorative purposes, and/or for furniture and/or to form a door. Typically, in the panel according to the invention, the front surface and/or the rear surface define a surface area which is larger than the surface area defined by the at least one side edge. It is conceivable that at least one decorative layer completely surrounds the core layer. Decorative layers may also be provided on all sides, including the front and rear surfaces of the panel. For example, one (rectangular) block panel may have six sides provided with a decorative layer.

The panel according to the invention, in particular the core layer therein, may comprise sealing edges. Thus, it is envisioned that the porous material forming the porous substrate is substantially sealed on all sides. For example, the panel may comprise a sealing strip or layer, preferably by heat lamination. The sealing layer may be heat laminated to the outer edge of the core layer. This has the additional advantage that the porous structure of the porous substrate and optionally of the support structure portion is sealed. This prevents dirt from accumulating or moisture from being absorbed into the core from the surrounding environment. A separate sealing strip may be used. Such embodiments may seal the porous substrate by heating, allow for greater structural integrity at the edges, and provide support for screws, fastening devices, snap systems, and/or interlocking mechanisms.

In a preferred embodiment, the panels comprise mutually mating connecting elements and/or connecting parts. For example, it is conceivable that at least two sides of the panel comprise mutually mating connecting elements. For example, the connection element and/or the connection component may be configured to provide a snap-fit connection and/or a snap-fit connection. For example, the connection parts of the panels may be interlocking connection parts, preferably providing horizontal and vertical locking. Interlocking connection members are connection members that require elastic deformation, snapping, or multidirectional movement to couple or decouple parts to or from one another. Any suitable interlocking connection means known in the art may be used. One non-limiting example is an embodiment wherein a first edge of the first pair of opposing edges comprises a first connecting part and a second edge of the first pair of opposing edges comprises a complementary second connecting part, the connecting parts 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 a plane defined by the panels, wherein the second connecting part comprises a groove configured to receive at least a portion of a lateral tongue 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-on assembly is thermoformed and/or milled.

The compressive strength of the support structure may be higher than the compressive strength of the porous substrate as measured in a direction from the front surface to the back surface of the core layer according to ASTM-D1037. Advantageously, the support structure may increase the overall compressive strength of the core and the panel. This makes the panel stronger and stiffer and less prone to fracture under pressure.

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 porous substrate to be bonded together without any adhesive, such as by thermal lamination. Identical compounds are defined herein as substantially identical molecules. For example, both the support structure and the porous substrate may be made of polyvinyl chloride. However, the density of the porous substrate may be lower than the density of the support structure, as the porous substrate may contain more cells and/or have larger volume cells (i.e., have a larger cell size). Because the density of the support structure is increased relative to the porous substrate, the strength of the support structure is higher than the porous substrate, thereby enabling the support structure to support the entire core layer. Thus, the average cell volume of the porous substrate is preferably greater than the average cell volume of the support structure. Alternatively, the support structure may be substantially free of cells.

The porous substrate and/or support structure may comprise a thermoplastic polymer or a thermosetting polymer. Thermoplastic polymers are preferred because they can be heated prior to extrusion to better control the viscosity of the extruded material. However, thermosetting polymers are also possible.

The porous substrate and/or support structure may comprise at least one material selected from the group consisting of 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 support structure is at least partially biodegradable. Thus, preferred polymers are biodegradable. It is conceivable that the porous substrate comprises at least one bio-plastic. It is also conceivable that the porous substrate and/or the support structure is made of a bio-plastic.

The polymer may also be a thermoplastic adhesive. The core layer preferably comprises at least one such thermoplastic adhesive. However, it is also conceivable that the core layer further comprises additionally or alternatively at least one thermosetting binder. The use of at least one thermoplastic or thermosetting material in the core is believed to impart flexible properties to the panel when necessary, for example when flexibility is required to achieve engagement of the locking mechanism.

The porous substrate and/or support structure may comprise starch-based plastics, soy-based plastics, cellulose-based plastics, lignin-based plastics and/or natural fibers. The biodegradability of these plastics makes them called environment-friendly panels, so that the panels can be biodegraded after their lifetime has ended.

The core layer, in particular the porous substrate, may comprise 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, pozzolan, vegetable fibers (such as mushroom fibers, cotton fibers, bamboo fibers, abaca fibers, pineapple fibers), magnesium compounds, magnesium oxides, magnesium alloys, etc., pineapple fibers, magnesium compounds, magnesium oxides, magnesium carbonate, limestone, polymeric fibers, glass fibers, carbon-based fibers, polymer particles, or hollow microspheres or particles made of materials including, but not limited to, ceramics, glass, polymers, composites, or metals having a particle size in the range of 1 to 1000 microns. Preferably, the core layer comprises at least one filler selected from the group consisting of minerals (preferably calcium carbonate), pigments, modifiers, fibers (e.g. glass fibers, wood, straw and/or hemp). The fibers may be loose fibers and/or interconnected fibers to form a woven or non-woven layer. Preferably, the core layer further comprises at least one additional filler selected from the group consisting of steel, glass, polypropylene, wood, acrylic, alumina, karya (curaua), carbon, cellulose, coconut, kevlar (kevlar), nylon, bayon (perlon), polyethylene, PVA, asbestos, vibe (viburnum), and fei-quail leaf fiber (fique). This may further increase the strength of the panel and/or the water and/or fire resistance of the panel. The core layer may be a wood plastic composite core layer.

The density of the porous substrate may be lowest at a location furthest from the support structure and highest at another location adjacent the support structure. The porous substrate may be formed from a plurality of porous sheets formed by expanding and laminating together an extrusion mixture (including thermoplastic polymers). Thus, the laminated outer edges of the porous sheet material constitute a support structure. The expansion of the outer edge is minimal due to the rapid cooling of the outer edge. The centers of each porous sheet material can be maintained at a high temperature for a longer period of time than the outer edges, and therefore, the degree of expansion of the centers is greater, resulting in the lowest density of the centers. Advantageously, this maximizes the core density of the support structure. Thus, the density of the porous substrate may be graded. Thus, the at least one porous substrate, in particular the porous material of the porous substrate, may have a density gradient. It is conceivable that the density of at least one side or at least two sides of the porous substrate is higher than the central portion of the porous substrate. The density gradient is advantageous to provide support for tightening, for example in a plane perpendicular to the panel. For example, the density gradient may be a density gradient across 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 near the back surface is higher than the density of the central region of the core layer between the front surface and the back surface. The density of at least a portion of the central region of the core layer is preferably substantially constant or uniform. For example, it is conceivable that the density near the front surface and/or near the back surface of at least one core layer is at least 5%, preferably at least 10% higher than the average density of the core layer. The density near the front surface and/or near the back surface is preferably higher than the density of the core body. When referring to a density near the front surface or near the back surface, it may refer to the upper or bottom region of the core layer. Basically, an embodiment is envisioned in which the core layer or porous substrate comprises an upper skin layer and/or a lower skin layer. The density of each skin layer is at least 5%, preferably at least 10% higher than the average density of the core layer. The skin layer is an inner skin layer, which is an integral part of the core layer. The skin layer may also be referred to as a shell layer. The skin layer is essentially an integral protective layer of the core layer. In a further preferred embodiment, the (core) density is higher near the front surface than near the rear surface. For example, it is also conceivable that the density of 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.

The porous substrate may have a density of between 80 and 1000kg/m ³, preferably between 100 and 1000kg/m ³, more preferably between 300 and 1000kg/m ³, such as about 600kg/m ³. When the porous substrate and the support structure are formed of different compounds, the density of the porous substrate may be relatively uniform. The density of the porous substrate may also vary from a location remote from the support structure to a location adjacent the support structure. A lower density is advantageous at locations remote from the support structure because the overall weight of the core will be substantially reduced, while a relatively higher density of the support structure may increase strength.

Preferably, the core layer has a discrete density gradient. Preferably, the porous substrate has a relatively low density and is relatively uniform compared to the average density of the core layer. Preferably, the density of the support structure is relatively high compared to the average density of the core layer, and is also relatively uniform. In particular, where the porous substrate and the support structure comprise the same compound and the cell volume and number are different, the density gradient between the porous substrate and the support structure is discrete. This ensures that the porous substrate is very light and the support structure is heavy and can withstand the vast majority of the load exerted on the panel.

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 the at least one core layer, has an expansion ratio of 5% to 50%. Non-limiting examples are expansion rates 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 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 an indicator of the rate of change of the volume of the panel, in particular of the core.

The at least one core layer may comprise 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 dimensional stability of the panel. For example, it is envisioned that the mineral material includes magnesium-based minerals such as, but not limited to, magnesium oxide (MgO), magnesium chloride (MgCl or MOC cements), magnesium sulfate (also known as MOS cements). 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 comprise a composite material having a weight ratio of mineral filler to thermoplastic binder of at least 3:1. It is also contemplated that the weight ratio of mineral filler to thermoplastic binder of the composite is greater than 3.5:1, or in the range of 3:1 to 4:1. Alternatively, however, it is also conceivable that the core layer comprises at least 30% by weight of at least one mineral filler, preferably at least 50% (by weight), 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 envisioned 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 may provide sufficient hardness, advantageously above 4000MPa MOE and 22MPa MOR, to ensure dimensional stability and toughness of the panel. The use of at least one polymer in the core is envisaged to impart flexibility properties to the panel when necessary, or for example when flexibility is required to effect engagement of the locking mechanism, if used, preferably below 9000Mpa and 36Nm MOR. The core layer according to the invention is particularly suitable for use in a thermal bonding process. The composite material of the core layer may for example comprise at least one additive to increase the vicat softening temperature. For example, the at least one additive may include Acrylonitrile Styrene Acrylate (ASA), acrylonitrile Butadiene Styrene (ABS), a thermoset system, and/or an epoxy system. The at least one additive may also be a vicat modifier or referred to as a vicat modifier. In another embodiment, the at least one polymer of the composite material may be a thermosetting polymer.

In one embodiment, the porous substrate and/or support structure comprises a Wood Plastic Composite (WPC). The wood-plastic composite materials are attractive and elegant, so that a decorative layer can be omitted.

The support structure may comprise a stone-plastic composite (SPC) and/or a metal (e.g. aluminum). Like the wood-plastic composite, the stone-plastic composite is also beautiful, so that a decorative layer can be omitted. Metals such as aluminum may provide additional stability to the support structure while being relatively light in weight, thereby forming a strong and lightweight panel.

Advantageously, the core and/or the panel are substantially free of adhesive. In particular, if the support structure and the porous substrate comprise the same compound, there is no need to provide an adhesive layer between the two. Further, in this case, the extruded porous sheet material may be bonded together by thermal lamination immediately after extrusion, without providing an adhesive. The binder typically releases harmful volatile organic compounds. Therefore, it is a great advantage not to use an adhesive. In particular, the panels may be joined together by complementary joining means (e.g. tongue and groove), even when the panels are mounted together to cover a larger surface than a single panel, without the use of adhesive.

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 panels have complementary connecting means, the connecting means may be more flexible, thereby facilitating the connection of the panels.

According to the invention, the at least one decorative layer applied in the panel may comprise at least one support layer, such as at least one (highly) filled thermoplastic support layer thermally laminated with a thermoplastic decorative layer, an optional wear layer, and an optional uv-coated finish. The at least one decorative layer, in particular the at least one support layer, may comprise or consist of SPC, LVT, extruded, calendered or injection molded thermoplastic.

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 at least one decorative layer, if applied, is adhered to the core layer. It is also conceivable that the decorative layer is a printed layer. It is also conceivable that at least one decorative layer is a printed layer, in particular a digitally printed layer. The decorative layer may also be an integral part 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 decorative images or patterns may be provided by printing, such as by digital and/or inkjet printing. At least one decorative pattern may also be formed by embossing the upper surface of the support layer or panel. It is also contemplated that the decorative or decorative layer is a separate layer, such as a High Pressure Laminate (HPL), veneer layer, directly laminated paper layer, and/or tile. In a preferred embodiment, the at least one decorative layer comprises a thermoplastic film or a cellulosic layer. For example, the decorative layer may comprise a plurality of impregnated layers comprising lignocellulose, including also wood, thermoplastic, stone, decorative layers or the like and/or combinations thereof. The veneer layer is preferably selected from the group consisting of wood veneer, cork veneer, bamboo veneer, and the like. Other materials such as ceramic tiles or porcelain, stone-like trim, rubber trim, decorative or vinyl, linoleum, and laminated decorative thermoplastic materials in the form of foils or films. It is conceivable that the support layer of the at least one decorative layer is connected to the support structure of the at least one core layer.

The at least one decorative layer may comprise at least one thermoplastic material. For example, the at least one support layer of the at least one decorative layer may comprise at least one thermoplastic material. The thermoplastic material may be PP, PET, RPET, PVC, PLA, PE, HDPE, LDPE, XPE or a thermoplastic starch (TPS) or other bioplastic. For example, the design of the decorative layer may be selected from a design database that includes 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 custom patterns. These patterns may be printed or reproduced using a laser printer, an inkjet printer, or any other digital printing means, including conventional 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, water repellency, light fastness, no acidity, metallic, gloss, sparkling, or jet black properties. Desirably, the decorative layer is visually exposed through a coating that is substantially transparent. The decorative layer may comprise a pattern, wherein the pattern is printed by digital printing, inkjet printing, gravure printing, electronic spool (ELS) gravure printing, automated plastic printing, offset printing, flexography, or rotogravure printing. The thickness of the decorative layer is preferably between 0.05mm and 0.10mm, for example approximately 0.07mm. In a preferred embodiment, the decorative layer comprises at least one decorative layer and/or at least one wear layer. For example, the wear layer may be a scratch resistant layer. The decorative layer may comprise an abrasion resistant layer or a facing layer, for example, a thermosetting varnish or lacquer (e.g., polyurethane, PUR, or melamine based resin). In a preferred embodiment, the decorative layer comprises at least one substantially transparent wear layer or finish layer. The wear layer may comprise one or more layers of transparent thermoplastic or thermosetting resins. Non-limiting examples of thermoplastic or thermoset 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 resins, and/or melamine or formaldehyde resins. The wear layer may also be a liquid or paste made of a thermosetting resin such as, but not limited to, phenolic resin and/or melamine or formaldehyde resin. The abrasion resistant layer may comprise or consist essentially of an inherently scratch resistant thermosetting resin impregnated carrier layer (e.g., paper or lignocellulose). One advantage of the latter embodiment is that the urea-formaldehyde resin also functions as a relatively scratch-resistant wear-resistant layer. In general, the thickness of the wear layer structure in the panels of the invention is preferably in the range of 0.1 to 2.0mm, more preferably between 0.15 and 1mm, more preferably between 0.2 and 0.8 mm. The thickness of the at least one support layer may be in the range of 0.2 to 2mm, preferably 0.5 to 1.5mm. Such an embodiment would provide sufficient body to the panel surface to obtain screw strength and/or screw pullout strength. At least one support layer of the at least one decorative layer is preferably substantially rigid. The rigid support layer may provide rigidity and strength to the panel. For example, the stiffness or MOE of at least one support layer may be greater than 2000Mpa, preferably greater than 4000Mpa, more preferably greater than 6000Mpa, according to EN 310 or according to ISO 24344 at a mandrel test of >100 mm.

The decorative top layer, in particular the support layer thereof, optionally comprises at least one filler. The material of the filler of the decorative layer or its support layer 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-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 made of a size of 1 to 1000 microns, including, but not limited to, ceramics, glass, polymers, composites, or metals. Preferably, the decorative or support layer comprises at least one filler selected from the group consisting of minerals (preferably calcium carbonate), pigments, modifiers, fibers (such as fiberglass, wood, straw and/or hemp). The fibers may be loose fibers and/or interconnected fibers to form a woven or 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, karya (curaua), carbon, cellulose, coconut, kevlar (kevlar), nylon, bayon (perlon), polyethylene, PVA, asbestos, vibe (viburnum), and fei-quail leaf fiber (fique). This may further increase the strength of the panel and/or the water and/or fire resistance of the panel.

In a preferred embodiment, the wear layer or finish layer may include at least one coating. For example, the at least one coating may comprise an at least partially transparent or translucent protective coating. In a preferred embodiment, the at least one coating may be, for example, a polyurethane coating, an acrylic coating, and/or an epoxy polyol coating. Such a coating may be, for example, an Ultraviolet (UV) or Electron Beam (EB) cured coating. It is further contemplated that the coating comprises a thermosetting resin and a photoinitiator that is crosslinked by UV, excimer or electron beam curing processes.

It is further contemplated that at least one decorative layer comprises a tactile texture, preferably having a depth of at least 0.1mm, more preferably at least 0.3mm. Such tactile textures may provide enhanced visual effects. 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 of the wear layers (if applied) may be embossed with a surface texture design. The grain design may be any desired design, such as a natural grain of wood, stone, or the like. The tactile structure may have, for example, an irregular tactile texture if applied. It is also conceivable that only part of the at least one decorative layer has a tactile texture. 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 0.1mm. In particular when the decorative layer is produced by a lamination process, a single press can be used, which makes it cost-effective to use a press plate with matching embossments for each decorative pattern in order to obtain a relief pattern matching the decorative pattern on the top surface of the panel.

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 the like. It is also conceivable that the resin composition impregnating the at least one layer of paper comprises at least one antimicrobial agent, preferably a metal oxide, such as titanium dioxide (TiO ₂), zinc oxide (ZnO) or isothiazolinone (isothiazolinone), zinc pyrithione (zinc pyrithione), thiabendazole (thiabendazole) and/or silver nanoparticles. The presence of at least one antimicrobial agent may be beneficial in situations where it is desired to apply floor panels or floor coverings made from such panels to commercial, industrial or areas where high hygiene standards exist. In the case of using an abrasion resistant layer or cover layer, an antimicrobial agent may also be present in the abrasion resistant layer or cover layer. The antimicrobial agent may be an integral part of the decorative layer. Panels comprising a decorative layer of at least one antimicrobial agent are generally better protected against bacterial, fungal, parasitic and/or viral attack than panels covered with an antimicrobial agent.

It is advantageous to bond the at least one decorative layer and the at least one core layer together by means of 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 advantage of using thermal bonding is that an intermediate adhesive layer between the decorative layer and the core layer can be omitted. The core and decorative layers according to the present invention may be applied using a thermal bonding process.

In another embodiment, the application also relates to a panel comprising at least one 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 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 of the embodiments described in the present application may also be applied to this alternative embodiment.

In another aspect, the invention relates to a method of preparing a panel, in particular the above-mentioned panel, comprising the steps of:

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 said at least two porous sheets to each other, optionally through said intermediate layer, to provide a stack of porous sheets connected by at least one joint, and

D) Cutting the stack of porous sheets in a direction from one of the porous sheets to the other porous sheet to provide at least one core layer comprising at least one porous substrate and at least one support structure, wherein the at least one porous substrate is comprised of portions of at least two porous sheets, wherein at least a portion of the at least one support structure is comprised of at least a portion of at least one junction connecting portions of the porous sheets, and

E) At least one decorative layer is glued to the at least one core layer to obtain a panel. This method is particularly advantageous because the extruded at least two porous sheets are bonded to one another with or without an intermediate layer. After cutting the porous sheet material, the seam between the two sheet materials acts as a support structure. Thus, the joint may form a rib-like structure formed by the portions cut from the joint. The resulting panels are typically flat sheets cut from both sides of the stack of porous sheets. If the porous sheet material itself is also in the shape of a flat plate, the resulting core layer also includes ribs in the form of partial plates. In this case, the two opposite outer edges of the ribs face the front and rear surfaces of the core layer, respectively, while the largest surface of the ribs may be adjacent to the porous substrate.

"Porous" as used herein refers to a substrate or sheet. The porous substrate or porous sheet material is composed of a material comprising a plurality of pores. Cells are voids in a material surrounding cells, which can have varying volumes. The material surrounding the cells is typically a polymer. In general, an expandable thermoplastic material is a material that is capable of expanding by forming cells. The cells may be filled with any type of gas, which may be a gas produced by the thermoplastic material itself as a by-product of the expansion reaction, or as a separate component in a mixture. Thermoplastic materials are polymeric materials that become flexible at high temperatures and solidify upon cooling. The process of cooling and heating the thermoplastic material is such that the thermoplastic material changes from a solid state to a formable or pliable state and vice versa, which process can be repeated almost indefinitely.

The core layer and/or the mixture formed may also contain at least one additive. For example, the core layer and/or the mixture may comprise at least one expanding agent, such as a foaming agent. The other additive may be a catalyst and/or at least one other filler. For example, the at least one (auxiliary) filler may be selected from the group of minerals (preferably calcium carbonate), pigments, modifiers, fibers (such as glass fibers, wood, straw and/or hemp). The fibers (if used) may be loose fibers and/or interconnected fibers forming a woven or non-woven layer. It is also conceivable that the core layer and/or the mixture comprises at least one additional filler selected from the group consisting of steel, glass, polypropylene, wood, acrylic, alumina, caroa (curaua), carbon, cellulose, coconut, kevlar (kevlar), nylon, bayan (perlon), polyethylene, PVA, asbestos, vibe (viburnum) and fei-quail fibres (fique). The use of any of the above components may further increase the strength of the core and thus the strength and/or the water and/or fire resistance of the panel.

An embodiment of a panel comprising a plurality of core layers is conceivable. In the case of using a plurality of core layers, it is preferable that there is at least one core layer, and more preferably each core layer is an extruded core layer. Such a porous core layer is further advantageous if at least one core layer, in particular each core layer, is at least partially foamed. For example, the panel may comprise at least two core layers. The core layer may be directly adhered to another core layer, e.g. without interference from an adhesive layer. It is conceivable that the core layers vary in thickness. It is also conceivable that the core layer has a different material composition. For example, it is conceivable that the upper core layer has a lower density than the lower core layer and vice versa. Each core layer may be a core layer according to any of the embodiments described herein. For example, it is conceivable that each core layer comprises at least one skin layer. The skin layer is also known as the shell layer. The skin layer is formed by cooling expansion of the outer surface of the porous substrate. Active or inactive cooling ensures that expansion on the outer surface of the porous substrate is inhibited to some extent, thereby forming a skin or shell. It is thus conceivable to join two adjacent core layers, bonding together adjacent skin layers, forming a complete support structure within the core layers. In a preferred embodiment, at least one of the core layers is a co-extruded core layer. For example, 2 or 3 layers of coextrusion are possible. In a preferred embodiment, at least one of the core layers is a co-extruded core layer. For example, 2 or 3 layers of coextrusion are possible.

It is envisaged that the expansion component present in the mixture will substantially completely decompose, the decomposition temperature of the expansion component generally being dependent 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 will depend on the specific material composition used and the preferred extrusion conditions.

From the extruder screw to the extruder die block, the mixture or melt may undergo a number 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 the melt proximate to at least one surface of the die compact may be in the range of 170 to 190 degrees celsius, preferably 175 to 185 degrees celsius, particularly to enable the formation of a protective skin or shell on at least one surface of the extruded porous sheet material. For example, the temperature difference between the screw and the die of the extruder, in particular the die press of the extruder, is at least 20 degrees celsius, preferably at least 30 degrees celsius.

The foaming composition may be formed into a desired plate shape by temperature control and/or pressure control in the extruder die. 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 channel of the extrusion die, in particular by the height and/or the volume of the internal channel.

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

A junction is a connection between two materials. When an intermediate layer is provided in step b), the junction may be constituted by the intermediate layer alone or by a combination of the outer surfaces of two porous plates immediately adjacent to the intermediate layer and the intermediate layer. Without an intermediate layer, the junction may consist of two adjacent outer surfaces of two porous sheets. In both cases, the thickness of the contact may be different. The thickness of the contact is typically a few millimeters.

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 stack of porous plates can form the support structure of the core. Depending on the location of the cut stack of porous sheet material, the number of joints and/or the orientation of at least part of the support structure may be determined.

It is conceivable to coextrude the porous sheet material to form a plurality of individual extruded sheet materials, known as a porous sheet material stack, which is then cut into blocks or sheets comprising a plurality of mutually bonded sections of the coextruded porous sheet material, 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 entire core volume.

In one embodiment, the bonding in step c) and/or step e) comprises thermal lamination. Thus eliminating the need for any adhesive. Thus, the method is more environmentally friendly because there are no harmful volatile organic compounds released by the binder.

At least two porous sheets may be cooled prior to step c). This has the advantage that, due to cooling, the formation of holes in the outer surface of the perforated plate and the volume of each hole is reduced. Thus, the density of these outer surfaces is relatively high compared to the density of the porous sheet material center. Since the outer surfaces of each porous sheet material may together constitute a support structure, the density of the support structure itself is relatively high. The high density of the support structure effectively increases the strength of the support structure, enabling the panel to withstand greater loads.

At least a portion of the upper surface and/or at least a portion of the lower surface of the porous sheet material may be cooled before and/or after the porous sheet material leaves the die compact of the extruder, preferably substantially immediately after the (shaped) porous sheet material leaves the die compact of the extruder. This step is particularly suitable for creating (discrete) density gradients within the porous sheet material. For example, at least a portion of the upper surface and/or at least a portion of the lower surface of the porous sheet material may be cooled such that the density near the upper surface and/or near the lower surface is higher than the average density of the porous sheet material. The cooling may in particular result in the formation of a skin layer, which forms an integral part of the porous sheet material.

It is conceivable to cool at least a portion of the melt in the die of the extruder, reducing the temperature of the melt by at least 10 degrees celsius, preferably at least 20 degrees celsius, more preferably at least 25 degrees celsius. It is also conceivable to reduce the temperature of the melt by at least 5 degrees celsius, preferably by at least 10 degrees celsius, when melting is carried out in the die compact 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 expanding component. It is conceivable that the temperature inside the melt, which is not directly exposed to the cooling step, is substantially inside the porous sheet material, above the decomposition temperature of the expansion component, thereby further expanding the core layer. This may create a beneficial density gradient wherein at least one surface of the porous sheet material has a higher density than the rest. The method may further comprise cooling at least a portion of the upper core surface and/or at least a portion of the lower core surface of the core layer before and/or after the core layer leaves the die compact of the extruder, preferably substantially directly after the (shaped) core layer leaves the die compact of the extruder. This step is particularly useful for creating a density gradient within the core layer. For example, at least a portion of the upper core surface and/or at least a portion of the lower core surface of the core may be cooled to a density near the upper core surface and/or near the lower core surface that is higher than the average density of the core. The cooling step may in particular result in the formation of skin layers, which constitute an integral part of the core layer.

It is conceivable 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, more preferably at least 25 degrees celsius. It is also conceivable to treat the melt in a die block of the extruder such that the temperature of the melt is reduced by at least 5 degrees celsius, preferably by at least 10 degrees celsius. 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 blowing agent composition. It is conceivable that the temperature inside the melt, which is not directly exposed to the cooling step, is substantially inside the core layer, above the decomposition temperature of the blowing agent composition, thereby further expanding the core layer. This may create an advantageous density gradient, i.e. a higher density of at least one surface of the core layer than the rest of the porous sheet material.

Preferably, at least two porous sheets may be extruded simultaneously. Another benefit of this is that the porous sheets will automatically stack together during the production process. In addition, the porous sheet material has a higher temperature when it leaves the extruder. Thus, the porous sheets can be bonded to each other to automatically form a joint without introducing additional heat or pressure.

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, 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 sheet material is particularly advantageous because lamination of the porous sheet material may be performed as part of the extrusion process rather than in a separate thermal lamination process.

The method further comprises, prior to the bonding of step e), bonding the at least two core layers to each other, wherein the direction of extension of the support structure of at least one of the at least two core layers is at an angle to the direction of extension of the support structure of at least another of the at least two core layers. It is particularly advantageous if ribs or ribs having a plate-like shape are formed in the core layer. The first core layer of the support structure comprising or consisting of such ribs may be rotated about 90 degrees with respect to another such core layer. The two core layers are bonded together to form a composite core layer having a total support structure having a grid-like structure when viewed from the front surface of the composite core layer toward the rear surface of the composite core layer. The core layer may also be rotated at angles other than 90 degrees. Multiple core layers, for example three, may also be combined. In the case of combining three core layers, the rotation angle of each core layer with respect to the core layer directly above or directly below may be 60 degrees. From top to bottom, a grid is formed comprising triangular porous substrate members.

The mixture may include an expanding agent or expanding component, such as supercritical CO ₂. Such expanding agents assist in forming cells in the porous sheet material. The expanding agent may be added separately as part of the mixture or may be generated in a chemical reaction initiated by the mixture after extrusion.

In a preferred embodiment, the at least one expansion component comprises azodicarbonamide (C ₂H₄N₄O₂) and/or sodium bicarbonate (NaHCO ₃). The above compounds have been found to be suitable for use as bulking agents. The foaming agent may be added to the mixture up to 1% by weight, preferably up to 0.8% by weight, based on the total weight of the mixture. In particular for sodium bicarbonate, it is desirable to apply the compound in an appropriate amount, since excessive sodium bicarbonate can cause the cells of the porous sheet to collapse, resulting in a more dense porous structure. It was found that the density of the porous sheet decreased almost linearly with increasing sodium bicarbonate. In a preferred embodiment, the expansion agent is added in an amount of 0.3 to 0.5wt% based on the total weight of the mixture.

Alternatively, or in addition, for example, the at least one bulking agent may include N, N '-dinitroso-N, N' -dimethyl terephthalamide (N, N '-dinitroso-N, N' -DIMETHYL TEREPHTHALAMIDE), N-aminophthalimide-4, 4'-oxybis (benzenesulfonyl hydrazide) (N-aminophthalimide, 4' -oxybis (benzenesulphonylhydrazide)), N '-dinitroso pentamethylene tetramine (N, N' -dinitrosopentamethylenetetramine), azoisophthalonitrile (Azoisobutyric dinitrile), diazo aminobenzene (Diazoaminobenzene), dinitroso pentamethylene tetramine (Dinitropentamethylene tetramine), benzenesulfonyl hydrazide (Benzenesulfohydrazide), terephthaloyl bis (N-nitroso methacrylamide) (TEREPHTHALYL BIS (N-nitrosomethylamide)), toluene-2,4-bis (sulfonyl hydrazide) (Toluene-2, 4-bis (sulfonyl hydrazide)), p-t-butylbenzoyl hydrazide (p-tertiary butylbenzazide)), p-methyl ester benzoyl azide (p-carbomethoxy benzazide), diaryl pentamethylene diene (Diarylpentaazadiene) and/or 3-methyl, 1,5-diphenyl pentamethylene diene (3, 3-diphenylpentaazadiene). The at least one expansion agent may be an exothermic expansion agent or an endothermic blowing agent. The expanding agent may also be referred to as a blowing agent.

It is advantageous to add at least one expansion catalyst to the mixture. Non-limiting examples of blowing catalysts that may be added to the mixture include calcium oxide, urea (Carbamide), zinc 2-ethylhexanoate (Zinc 2-ethylhexanoate), zinc benzene sulfinate (Zinc benzenesulfinate), zinc carbonate (Zinc carbonate), zinc xylene sulfinate (Zinc ditolyl sulfinate), zinc oxide, zinc stearate, calcium/Zinc esters, barium/Zinc esters, potassium/Zinc esters, dibutyl tin bis (diisooctyl maleate) (Dibutyltin bis (iso-octylmaleate)) and/or dialkyl tin bis (alkyl thioglycolate) (DIALKYLTIN BIS (alkylthioglycollates)).

In one embodiment, the sealing tape may be thermally laminated with at least a portion of the at least one core layer prior to step e). The sealing layer may be heat laminated to the outer edge of the core layer. Therefore, the sealing strip has an edge sealing function. Another benefit of this is that the porous structure of the porous substrate and optionally part of the porous structure of the support structure is sealed. This prevents dirt from accumulating or moisture from being absorbed into the core from the surrounding environment. A separate sealing strip may be used. Such a sealing strip may consist of the same or different material as the core layer. Advantageously, the sealing strip does not comprise a porous material. It is also conceivable to heat at least a portion of at least one core layer so as to form a shell that is substantially free of cells and has a relatively high density. Another benefit of the autoclave layer is that no separate adhesive is required. In addition, the screws may be inserted into a sealing strip or formed housing, since this part of the core layer has a high density and is thus well suited for fixing the screws. The sealing strip or the housing can also be manufactured as a snap-on system.

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

Preferably, the system comprises a cooler for cooling the extruded thermoplastic material. In particular, by adjusting the amount of cooling outside the extruded thermoplastic material, the thickness of the outer surface of the porous sheet material can be adjusted as desired. After the porous sheet stack is formed, the resulting joints, and thus the support structure in the core, may be adjusted according to the strength and/or weight required by the support structure.

Multiple dies and/or die compacts may be stacked on top of each other. Thus, the porous sheets can be advantageously stacked together automatically. When the stack of porous sheet material needs to be cut, the system may comprise a cutting element for cutting the stack of porous sheet material. In this way, the cutting can be done on-line by the system itself, without the need for a separate cutting device. The cutting position can be adjusted according to the desired thickness of the core layer.

Drawings

The invention will now be elucidated on the basis of non-limiting exemplary embodiments shown in the following figures. The figure shows:

fig. 1 is a panel according to a first possible embodiment of the invention;

FIGS. 2a, 2b, 2c and 2d are one possible method of producing a panel according to the invention;

fig. 3 is a panel according to a third possible embodiment of the invention;

FIGS. 4a, 4b, 4c and 4d are side views of a panel according to a possible embodiment of the invention;

Fig. 5a and 5b show a panel according to a further possible embodiment of the invention, and

Fig. 6a and 6b show panels according to further possible embodiments of the invention.

In the drawings, the same reference numerals refer to similar or equivalent technical features or elements.

Detailed Description

Fig. 1 shows a panel 100 according to a first possible embodiment of the invention. The panel 100 is in particular a decorative panel and/or a structural panel 100. The embodiment shown in the figures includes 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 portion of the decorative layer 102 is shown in order to view 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 back surface on opposite sides, wherein the thickness T of the core layer is defined by the distance between the front surface and the back surface. As can be seen from the figure, a portion of the support structure 104 extends over the thickness T of the core layer 101. In the illustrated embodiment, the support structure 104 includes a plurality of ribs 104a that extend across the thickness T of the core layer 101. The ribs 104a are positioned substantially parallel to each other and define an angle with respect to the front and back surfaces of the core that is substantially a right angle. In the embodiment shown, the ribs 104a are at a distance from each other. In fact, the ribs 104a in the illustrated embodiment are individual 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.

Fig. 2a to 2d show a process or method of producing a panel 200 according to one possible embodiment of the invention. Fig. 2a shows an intermediate product produced by an extrusion process. The arrow indicates the extrusion direction E. Fig. 2a shows a plurality of interconnected porous sheets 250 produced by an extrusion process. In the embodiment shown in the figures, the plurality of porous sheets 250 are produced by extruding at least one mixture comprising at least one expandable thermoplastic material. As shown in fig. 2a, the porous sheets 250 are bonded to each other by an intermediate layer to form a porous sheet stack 250. The porous plates 250 are connected by joints 251. As shown in fig. 2b, the stack 250 of porous sheets will then be cut to form the core layer 201 of the present invention. Fig. 2a shows a cutting line C, which is directed from one perforated plate 250 to another perforated plate 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 comprising 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 said porous plates 250 a. Step 2c shows the placement of a plurality of decorative layers 202. In the embodiment shown, two decorative layers 202 are adhered to the core layer 201. Fig. 2d shows a panel 200 manufactured according to the invention, on which complementary connecting parts 230a, 230b are provided. Fig. 2d shows a side view of the panel.

Fig. 3 shows a picture of a panel 300 manufactured according to the invention. The panel 300 comprises a core layer 301, said core layer 301 comprising 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 integrally formed within the porous substrate 303.

Fig. 4a, 4b, 4c and 4d show side views of panels 400a, 400b, 400c and 400d according to possible embodiments of the invention. These panels are optionally equipped with connecting parts.

Fig. 4a shows a panel 400a comprising a core layer 401, said core layer 401 comprising a porous substrate 403 and a support structure 404. The embodiment shown in the figures includes two decorative layers 402a, 402b, each 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 illustrated embodiment, the support structure 404 is a triangular structure. Adjacent ribs 404a of the support structure 404 define triangles. Each triangular leg extends from the front surface to the back surface of the core layer 401. In the illustrated embodiment, the ribs 404a are interconnected. However, it is also conceivable that the ribs of the triangular support structure are kept at a distance from each other.

Fig. 4b shows an embodiment of a panel 400b comprising two core layers 401a, 401 b. The upper core layer 401a includes a porous substrate 403 and a support structure 404. The lower core layer 401b includes a porous substrate 403b. The lower core layer 401b has no reinforcing structure. The panel 400b further comprises three decorative layers 402a, 402b, 402c, which encase at least a portion of the core layers 401a, 401 b. The density of the upper core layer 401a is lower than the density of the lower core layer 401 b. 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.

Fig. 4c shows a panel 400c, the panel 400c shown comprising a core 401 and a decorative layer 402 attached to the front surface of the core 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 400 c.

Fig. 4d shows a panel 400d, the panel 400d comprising a core 401 and a decorative layer 402a adhered to the front surface of the core 401 and a decorative layer 402b adhered to the rear surface of the core 401. The core layer 401 further 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 formed by a portion of the porous material of the porous substrate 403. It is envisioned that the support structure 404, and in particular the ribs thereof, may have a density gradient with the substrate 403.

Fig. 5a and 5b show panels 500a and 500b according to possible embodiments of the invention.

Fig. 5a shows a cross-sectional view and an assembled view of a panel 500a, the panel 500a comprising a core layer 501, a secondary support structure 540 and a decorative layer 502 formed by decorative printing. Decoration printing is provided by printing (e.g. digital printing or inkjet printing). The upper part of the figure schematically shows the printing device 580 and the printing steps. 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 wall structure. The sheets 540a and 540b wrap around the honeycomb 540c, thereby forming a double wall structure. For example, the honeycomb 540c may be made of a different material than the sheets 540a, 540b surrounding the honeycomb 540 c. For example, honeycomb 540c may be made of metal, particularly aluminum, and sheets 540a and 540b may be made of polymer. Core layer 501 includes a porous substrate 503 and a support structure 504.

Fig. 5b shows a panel 500b according to another embodiment of the invention. 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 surrounding the core layer 501. The support structure 504 is defined as a honeycomb structure. The support structure 504 is filled with a porous material forming a porous substrate 503.

Fig. 6a and 6b show panels 600a and 600b according to other possible embodiments of the invention. A schematic is shown in which fig. 6a shows an exploded view and a perspective view. Fig. 6b shows a partially exploded view.

The upper half of fig. 6a shows a front view and an exploded view of the panel 600a, and the lower half shows the final structure or combined view of the panel. The panel 600a comprises a core 601 and a plurality of decorative layers 602, the decorative layers 602 being laminated with the core 601, each decorative layer 602 comprising a support layer 602a, a decorative layer 602b and a wear layer and/or a protective layer 602c. The core layer 601 comprises a porous material. The core layer 601 comprises in particular a porous substrate 603. It can be seen that the material of the core layer 601 is a porous material having different densities. The core layer 601 exhibits a substantial density gradient. Smaller bubbles near the surface of core 601 indicate higher density, and larger bubbles near the middle of core 601 indicate lower density. Near the edges of the core 601, the bubbles are relatively small, indicating that the density on this side is high, due to the hot lamination on the edges. According to the invention, the core layer 601 is optionally provided with a support structure.

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

It is obvious that the invention is not limited to the working examples shown and described herein. But that many variations are possible within the scope of the appended claims. Such variations will be apparent to those skilled in the art.

The verb "comprise" and its conjugations as used in this patent publication are understood to mean not only "comprising" but also the phrases "comprising," "consisting essentially of," "forming," and variants thereof.

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. A panel according to claim 1, wherein at least a portion of the at least one supporting structure extends over the entire thickness of the porous substrate of the at least one core layer, and/or wherein the at least one supporting 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. A 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 a front surface and/or a rear 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 core layers, wherein each core layer comprises at least one porous substrate and at least one supporting structure, wherein a first supporting structure of a first core layer is arranged at an angle relative to a second supporting structure of a second core layer.

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

7. The panel according to any of the preceding claims, wherein at least a portion of the at least one supporting structure is defined by a honeycomb structure and/or a double wall and/or a grid structure.

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

10. A panel as claimed in any preceding claim, wherein the panel comprises mutually matching connecting parts.

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, measured in the direction from the front surface to the rear surface of the core layer according to ASTM-D1037.

12. A panel according to any 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 core layer has a density in the range 80-1000 kg/ ^m3 , preferably 100-1000 kg/ ^m3 , more preferably 300-1000 kg/ ^m3 , such as about 600 kg/ ^m3 .

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

17. The panel according to any 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:

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 by at least one joint; and

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 the 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 further comprises the 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. A 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 molds and/or the mold compacts are stacked on top of each other.