Decorative panel, core layer, and method for producing such a panel

Abstract

Decorative panel, in particular a decorative floor panel, decorative ceiling panel, or decorative wall panel, comprising at least one core layer, and a decorative layer directly or indirectly affixed to a top surface of said core layer, wherein said at least one core layer is made from a polymeric composition.

Description

[0001] Decorative panel, core layer, and method for producing such a panel

[0002] The present invention relates to a panel, such as a decorative panel, in particular a decorative floor panel, decorative ceiling panel, or decorative wall panel, comprising: at least one core layer, and preferably a decorative layer directly or indirectly affixed to a top surface said core layer. The invention moreover relates to a core layer for use in such a panel. The invention also relates to a method of producing a core layer which is suitable for a panel, in particular a decorative panel, according to the invention. The invention further relates to a method of producing a panel, in particular a decorative panel, according to the invention.

[0003] In the last decades many improvements have been observed in the world of decorative panels, such as floor panels and wall panels. These improvements cover various aspects of the decorative panels, such as, for example, improving the aesthetical appearance of the panels, improving mechanical coupling profiles of the panels, improving the acoustic properties of the panels, improving the scratch resistance of the panel, and improving the material that is used for making the core layer of the panels.

[0004] With respect to this latter aspect, a trend is visible that traditional core layer materials, like medium density board (MDF) and high density board (HDF) are partially replaced by other materials, like PVC based compositions. Contrary to MDF and HDF, PVC is waterproof and therefore easy to maintain and moreover exhibits relatively attractive noise reducing properties. However, the use of PVC in core compositions of decorative panels is not undisputed. As this PVC is typically softened by using hazardous plasticizers, like phthalates, health risks may be involved. Moreover, during the production of PVC toxic chemicals are used and toxic by-products and waste are generated. Furthermore, in case of a fire, PVC based panels may generate carcinogens, which is less preferred from a health safety and environmental point of view.

[0005] In addition to the above drawbacks of using PVC, the carbon footprint of PVC is substantial. As awareness is increasing regarding the health safety of materials as well as regarding the environment, a response is being demanded from the industry and its customers to also use different raw materials for manufacturing decorative panels which do not have the drawbacks of PVC at all, or only to a limited extent. More in particular, there is a need to develop a core layer for a decorative panel, which is relatively health safe and which seriously reduces the carbon footprint to spare the environment as much as possible.

[0006] It is therefore a first objective of the present invention to provide a panel, in particular a decorative panel, having a relatively low carbon footprint. Additionally, it is an objective of the present invention to provide a decorative panel having a core layer which is more health safe and / or environmental friendly than a PVC core layer.

[0007] A further objective of the present invention is to provide a decorative panel wherein the core layer is made of a material which imparts the decorative panel with improved properties in the context of its intended use.

[0008] Another objective of the invention is to propose a core layer which is made from a material that is attractive to process in the context of the production of a core layer, for instance when the core layer is produced via the technique of extrusion.

[0009] As an alternative material to PVC, it is has initially been considered to use PET (polyethylene-terephthalate) for the production of core layers, however it was found by the inventors that the above objectives still were not sufficiently met by such a strategy. Consequently, further room for improvement exists in regard of replacing PVC by PET as a material for the core layer.

[0010] At least one of the above objectives are fully or sufficiently achieved by the invention which relates, according to a first aspect, to: a panel, such as a decorative panel, in particular a decorative floor panel, decorative ceiling panel, or decorative wall panel, comprising:

[0011] • at least one core layer, and

[0012] • optionally at least one decorative layer directly or indirectly affixed to a top surface of said core layer; wherein said at least one core layer is at least partially made from a polymeric composition which comprises at least one copolymeric variant of polyalkylene terephthalate , such as polyethylene terephthalate (v-PET), which consists and / or comprises of polymeric chains that are formed by polymerization of at least three types of monomer which are:

[0013] - at least one alkylene glycol (AG) monomer, such as an ethylene glycol (EG) monomer or an analogue thereof,

[0014] - a terephthalic acid (TPA) monomer,

[0015] - and a third monomer which is a heterocyclic organic molecule (HOM) that is provided with two functional groups each of which is suitable for formation of an ester bond with at least one of the other two monomer types (AG / EG; TPA).

[0016] As a first advantage, it is noted that the inclusion of a third monomer in v-PET allows for the incorporation of bio-based components, which may be derived from the compound furfural (C5H4O2) which is derivable from widely available agricultural residual products. Consequently, by virtue of its third monomer, v-PET has a reduced carbon footprint because less petroleum-based raw materials are needed for its production.

[0017] A second advantage, is that v-PET was found to have an improved melt flow and as such is more flexible and easier to process in comparison to PET, which improved processability is also referred to as an improved melt strength. This advantage is especially significant in the context that a core layer is preferably formed by extrusion of the polymeric composition from which the core layer is made.

[0018] A third advantage is related to the inherent crystallinity of v-PET, especially when v-PET is used for making an article by extrusion. It was found that the crystallinity of an article made from v-PET is less brittle than PET, and therefore v- PET has an improved impact resistance over PET, especially when the article was made by extrusion. This improved crystallinity is probably a result of incorporating a heterocyclic organic molecule as a third monomer.

[0019] Finally, it was found that v-PET is expediently recyclable via chemical decomposition (glycolysis or hydrolysis) or thermal decomposition (pyrolysis), which further contributes to mitigating the environmental impact of the polymeric material by recycling used quantities of v-PET of virgin quality. In particular, the recycled v-PET was found to have a better performance and value in comparison to recycled PET. For clarity, it is noted that the term ‘copolymeric variant of polyethylene terephthalate’ is used to indicate that it is a polymeric variant of PET by containing at least one additional monomer, i.e. a third monomer, and that it may include more additional monomer types. In case that the polymeric chains of v-PET would be restricted to the exact three types of monomer as specified, such polymeric chains could appropriately be characterized as a terpolymer.

[0020] In addition to the above scope of the invention, it is noted that the invention also relates to a ‘copolymeric variant of polyethylene terephthalate’ which are actual analogues of PET wherein ethylene glycol is replaced by an analogue thereof as a first monomer. Such an alternative first monomer to ethylene glycol which is suitable in the context of the invention is typically and preferably a linear organic polyol, in particular a diol, having a chain of three up to eight carbon atoms, and includes for instance propylene glycol or butylene glycol. Accordingly, the copolymeric variant of PET (v-PET) encompassed by the invention may actually be a variant of polypropylene terephthalate (PPT) or polybutylene terephthalate (PBT), or a variant of a mixture of PET, in particular v-PET, and / or PPT and / or PBT. These three polymers may also be referred to as polyalkylene terephthalate. In this disclosure of the invention, the expression “v-PET” or “PET” may be replaced by PPT and / or PBT and / or polyalkylene terephthalate and / or one of the examples mentioned below. More generically formulated, the polymeric composition used in the core layer may comprise or consist of one or more polyalkylene terephthalates, which are polyesters derived from the polycondensation of terephthalic acid (TPA) or a derivative thereof with one or more alkylene glycols. Suitable polyalkylene terephthalates include, but are not limited to: Polyethylene terephthalate (PET), derived from ethylene glycol and TPA; Polybutylene terephthalate (PBT), derived from 1 ,4-butanediol and TPA; Polytrimethylene terephthalate (PTT), derived from 1 ,3-propanediol and TPA; Polypropylene terephthalate (PPT), derived from propylene glycol and TPA; Polycyclohexylene dimethylene terephthalate (PCT), derived from 1 ,4-cyclohexanedimethanol and TPA; Polyethylene glycol) terephthalate (PEGT), derived from polyethylene glycol) and TPA; Polyisobutylene terephthalate (PIT), derived from isobutylene glycol and TPA; Copolymers or terpolymers of the above, optionally including one or more additional diols or diacids, such as aliphatic, aromatic, or heterocyclic compounds capable of forming ester linkages; and / or Biodegradable polyalkylene terephthalates such as poly(butylene adipate-co-terephthalate) (PBAT), which is a co-polyester of TPA, adipic acid, and 1 ,4-butanediol. These polyesters may be homopolymers, random or block copolymers, or copolymeric blends, and may optionally be modified with branching agents, and / or nucleating agents, and / or fillers to enhance performance.

[0021] The term “alkylene glycol monomer”, as used herein, refers to a diol comprising an alkylene group, and is suitable for undergoing polycondensation with dicarboxylic acid monomers (such as terephthalic acid) to form polyalkylene terephthalates. Suitable alkylene glycol monomers include, but are not limited to: Ethylene glycol (EG); 1 ,2-Propylene glycol (1 ,2-PG); 1 ,3-Propanediol (PDO); 1 ,4-Butanediol (1 ,4- BDO); Neopentyl glycol (NPG); 1 ,5-Pentanediol; 1 ,6-Hexanediol; Diethylene glycol (DEG); Triethylene glycol (TEG); Polyethylene glycol) (PEG), having a numberaverage molecular weight typically in the range of 200-2000 g / mol; Cycloaliphatic diols, such as 1 ,4-cyclohexanedimethanol (CHDM); Branched or substituted alkylene diols, provided they contain at least two hydroxyl functional groups capable of esterification. The alkylene glycol monomer may be linear, branched, or cyclic in structure, and may optionally include ether linkages, substituted alkyl groups, or other non-interfering functional groups. One or more alkylene glycol monomers may be used in combination to form copolymers or terpolymers.

[0022] Mixtures of such diols may also be used to tailor the mechanical, thermal, and processing properties of the resulting polymer.

[0023] The term “analogue of ethylene glycol” or more broadly “analogue of a polyalkylene glycol monomer”, as used herein, refers to any organic compound that is structurally or functionally similar to ethylene glycol or other alkylene glycols, and that possesses at least two hydroxyl (-OH) groups capable of participating in polycondensation or esterification reactions with diacid or diester monomers (such as terephthalic acid). Suitable analogues include, but are not limited to: Linear alkylene diols of varying chain lengths, such as: 1 ,3-propanediol, 1 ,4-butanediol, 1 ,5-pentanediol, 1 ,6-hexanediol; and / or Branched diols, such as: Neopentyl glycol (2,2-dimethyl-1 ,3-propanediol); Ether-containing glycols, such as: Diethylene glycol (DEG), triethylene glycol (TEG), polyethylene glycol (PEG) with molecular weights between approx. 200-2000 g / mol; Cycloaliphatic glycols, such as: 1 ,4- cyclohexanedimethanol (CHDM); Substituted or functionalized glycols, including those with pendant alkyl groups, halogens, or ether linkages, provided that such substitutions do not impair reactivity in polycondensation; Oligomeric or polymeric glycols, such as PEG or polypropylene glycol) (PPG), that can function as flexible or hydrophilic segments in the resulting copolyester; Biobased or renewable diols, such as isosorbide, xylitol, or sorbitol, provided they are functionalized for ester formation; Aromatic diols, such as hydroquinone, resorcinol, or bisphenol-A, may also be considered analogues when capable of forming polyesters with terephthalic acid or derivatives thereof. These analogues may be used to replace or supplement ethylene glycol in whole or in part, and may serve to modify the thermal, mechanical, optical, or chemical resistance properties of the resulting polymer. Use of such analogues may also support the formation of copolymeric or terpolymeric variants of polyalkylene terephthalates with tailored characteristics.

[0024] In the decorative panel according to the invention, it is preferred that the heterocyclic organic molecule (HOM) contains a five-membered ring that is composed from four carbon atoms and one oxygen atom.

[0025] Further in the decorative panel according to the invention, it is preferred that either the five-membered ring is of a furan type which is an aromatic compound, or a hydrogenated furan type which is a non-aromatic compound, or wherein the third monomer is composed of a mixture of the furan type and the hydrogenated furan type.

[0026] Especially preferred in the decorative panel according to the invention, is preferred that the two functional groups of the heterocyclic organic molecule (HOM) are either two hydroxyl groups or two carboxyl groups, or a combination of one hydroxyl group and one carboxyl group.

[0027] Furthermore preferred in the decorative panel according to the invention, is that the two functional groups of the heterocyclic organic molecule (HOM) are attached to two different carbon atoms of the heterocyclic organic molecule.

[0028] In particular it is herein preferred that the two different carbon atoms to which the two functional groups are attached, are two carbon atoms which are either both in an alpha position or both in a beta position relative to the oxygen atom. In a particular preferred embodiment of the decorative panel according to the invention, the third monomer is either of: i) a five-membered ring of the furan type which has two carboxyl groups attached to two different carbon atoms and which is an aromatic compound; and / or ii) a five-membered ring of the hydrogenated furan type which has two hydroxyl groups attached to two different carbon atoms and which is a non-aromatic compound.

[0029] In the above context, it is especially preferred that: the furan type i) is 2,5-furandicarboxylate or 3,4-furandicarboxylate (FD), optionally comprising additional organic residue groups such as methyl groups, for instance dimethyl-2,5-furandicarboxylate or dimethyl-3,4-furandicarboxylate (DMFD); and / or the hydrogenated furan type ii) is 2,5-tetrahydrofurandimethanol, 3,4- tetrahydrofurandimethanol (THFDM), 2,5-dihydroxy-tetrahydrofuran or 3,4- dihydroxy-tetrahydrofuran (DHTHF), optionally comprising additional organic residue groups such as methyl groups.

[0030] Further preferred third monomer types of the above indicated type i) or type ii) in the context of the invention, comprise one or more of the following compounds:

[0031] Furfural (Furan-2-carbaldehyde);

[0032] 5-Hydroxymethylfurfural (HMF);

[0033] 2.5-Furandicarboxylic Acid (FDCA);

[0034] Furfuryl Alcohol;

[0035] 2.5-Bis(hydroxymethyl)furan (BHMF);

[0036] Levulinic Acid;

[0037] 2-Furoic Acid;

[0038] Methylfuran;

[0039] Furfural Acetone;

[0040] Furan-2,5-dicarboxaldehyde.

[0041] In the decorative panel according to the invention, it is preferred that the polymeric chains contain a first type of polyester units PU1 composed of an ester of an EG monomer with a TPA monomer, and a second type of polyester units PU2 composed of an ester of an HOM monomer with either a EG monomer or a TPA monomer, wherein the molar ratio of PU2 / PU1 is 5 / 95 up to 20 / 80, preferably up to 15 / 85.

[0042] It has been found that the polymeric chains having such a molar ratio of the polyester units result in the v-PET material having an appropriate crystallinity for processing of the material into a core layer, in particular in regard of extruding the v-PET material into an article from which a core layer is produced.

[0043] Further in the decorative panel according to the invention, it is preferred that the polymeric chains have a EG / TPA molar ratio in a range from 40 / 60 up to 60 / 40.

[0044] In the decorative panel according to an embodiment of the invention, it is preferred that the core layer is made from the polymeric composition by extrusion of the polymeric composition into an extruded product of a suitable format.

[0045] In this context, it is noted that the suitable format is such that it is appropriate for further dimensioning the extruded product to the required dimensions of the core layer. The core layer is typically of an oblong or rectangular format, similar to the (flat) panel, wherein the thickness of the core layer typically varies between 4 and 10 mm, preferably between 4.5 and 8 mm.

[0046] In the decorative panel according to the invention, it is advantageous that the copolymeric variant of polyethylene terephthalate (v-PET) is of virgin quality, of recycled quality, or is a mixture of both qualities. The v-PET may be a solid or may be foamed. The v-PET used in at least one layer of the decorative panel may be amorphous v-PET (v-APET), which is transparent, or may be crystalline v-PET (v- CPET), which has a higher thermal resistance compared to APET.

[0047] In a particularly preferred embodiment of the decorative panel according to the invention, the copolymeric variant of polyethylene terephthalate (v-PET) contains polymeric chains which are extended by incorporation of a chain extender, wherein the chain extender is an additional molecule that is bonded with at least two, preferably at least four, of the monomers that are present in the polymeric chains of v-PET.

[0048] The incorporation of a chain extender in polymeric chains of v-PET contributes to creating polymeric chains that are sufficiently large for the intended purpose of the invention. Furthermore, the chain extender when having a functionality of three or four, will generate a polymeric structure of v-PET that has more dimensions than a purely linear polymeric structure, which may further enhance the properties of v-PET in view of its intended purpose.

[0049] The use of a chain extender is especially beneficial when producing v-PET of a recycled quality, because the process of forming v-PET of recycled quality involves initially the decomposition of a used quantity of a copolymeric variant of polyethylene terephthalate (v-PET), wherein the original polymeric chains are broken into shortened polymeric chains.

[0050] Further aspects of the chemical process of forming v-PET are discussed in more detail in the below sections wherein further aspects of the invention relating to methods of producing a panel and a core layer are discussed.

[0051] With regard to the nature of the chain extender, it is preferred that at least one chain extender is a multifunctional epoxide oligomer, more preferably an epoxide oligomer having a chemical structure according to the formula: wherein

[0052] - R1-R5 are H, CH3, a higher alkyl group, or combinations of them;

[0053] - R6 is an alkyl group, and

[0054] - x, y, and z are each between 1 and 20.

[0055] Further in the context of the chain extender, it is preferred that at least one chain extender is a molecule of a dianhydride type, preferably pyromellitic dianhydride (PMDA) and / or mellophanic dianhydride (MEDA).

[0056] In a further preferred decorative panel according to the invention, the core layer is structured as a laminate of multiple core layers, containing at least two core layers that are made from the polymeric composition which comprises the copolymeric variant of polyethylene terephthalate (v-PET), wherein preferably an intermediate layer of different properties than v-PET is present between the two core layers of v- PET.

[0057] When the core layer is structured as a laminate, it is preferred that an reinforcement layer, such as a glass fibre layer, is present as an intermediate layer between two core layers that are made from v-PET. A further attractive intermediate layer is of a foamed quality, which reduces the overall density of the core layer and which enhances the sound dampening properties of the decorative panel as such.

[0058] In the decorative panel according to the invention, it is further advantageous when the polymeric chains of v-PET have an average molar mass smaller than 20,000, preferably smaller than 15,000, more preferably smaller than 12,000 g / mol.

[0059] Preferably, this average molar mass is higher than 10,000 g / mol to secure a sufficiently high viscosity, preferably of at least 0.5 dl / g. The molar mass of the polymeric chains of v-PET is approximately a multiplexity of the values within the above indicated ranges.

[0060] In the decorative panel according to the invention, it is attractive when the polymeric composition from which the core layer is made further includes an inorganic filler and / or an organic filler, wherein the total amount of filler in the core layer is at least 50 percent by weight of the core layer, preferably at least 60 percent by weight of the core layer, more preferably at least 70 percent by weight of the core layer, such as at least 75 percent by weight of the core layer.

[0061] Typically, the chain-extended PET molecules form a polymer matrix, wherein one or more fillers are dispersed. Examples of an inorganic filler, resp. an organic filler which are very suitable for the invention are limestone, resp. wood particles. Other suitable inert and / or functional fillers are for example, chalk, calcined clay, glass particles, glass fibres, carbon particles, silicon particular, a(nother) mineral filler, rice, a(nother) natural filler, a(nother) (auxiliary) polymer, such as an elastomer and / or latex. These fillers are often used to either reduce the cost price of the core layer and / or to make the core layer either more flexible or more rigid (stiff). It is advantageous in the decorative panel according to the invention, that the polymeric composition from which the core layer is made comprises at least one lubricant, for instance long-chain fatty acids compounds, preferably in an amount of not more than 1 percent by weight of the polymeric composition.

[0062] The inclusion of a lubricant in the polymeric composition is especially attractive when the composition is subjected to temperatures of 200°C or higher, such as during extrusion of the polymeric composition. The lubricant’s primary role is to reduce friction, minimize wear, and prevent overheating of parts during extrusion.

[0063] It is further attractive in the decorative panel according to the invention, that the polymeric composition from which the core layer is made comprises at least one toughening agent, preferably in an amount of not more than 10 percent by weight of the core layer, more preferably in an amount of 3 to 8 percent by weight of the core layer.

[0064] In this context, the toughening agent is suitable reduce the melt flow index (MFI) of the polymeric composition, for example to a value of approximately 50 g / 10 min, which is favourable to produce the core layer by extrusion.

[0065] An example of a suitable toughening agent is a styrene-ethylene-butylene- styrene terpolymer functionalized with maleic anhydride (SEBS-g-MA) (such as (FG1901X obtained from KRATON Corporation).

[0066] In a preferred embodiment of the decorative panel according to invention, the panel comprises one pair of opposing side edges which are provided with complementary coupling profiles allowing intercoupling of adjacent decorative panels, and preferably the panel comprises two pairs of opposing side edges each pair of which is provided with complementary coupling profiles allowing intercoupling of adjacent decorative panels.

[0067] The complementary coupling profiles are preferably of an complementary groove / tongue design by the profiles which can be interconnected with each other.

[0068] One tongue / groove design that is preferably used for a pair complementary coupling parts, is such that the coupling parts can be interconnected with each other by an angling (i.e. a rotational) movement of the coupling parts with respect to each other. Another tongue / groove design that is preferably used for a pair complementary coupling parts, is such that the coupling parts can be interconnected with each other by a mutual vertical movement of the coupling parts towards each other.

[0069] It is especially preferred in the panel according to the invention, that both above mentioned types of tongue / groove design are included in the panel.

[0070] The complementary coupling profiles may be formed substantially in the core layer material, for instance by removal of core layer material at the side edges by milling.

[0071] The decorative layer preferably comprises a plurality of layers, comprising at least one printed decor, in particular at least one digitally printed decor, and at least one transparent and / or translucent wear layer covering said printed decor. Said printed decor is printed onto a primer layer and / or onto a film, such as a paper film or a thermoplastic film. Said thermoplastic film is a PET based film and / or a PET-v based film, which facilitates recycling of the panel post-use. Alternatively formulated, the decorative layer may make part of a decorative top structure applied onto the core layer(s), wherein the decorative top structure preferably comprises at least one decorative layer and at least one transparent wear layer covering said decorative layer. The decorative top structure may additionally comprise at least one back layer situated in between said decorative layer and the core, wherein said back layer is preferably at least partially made of a vinyl compound, wood, coconut fibers, coconut husk, paper, textile, such as, and / or combinations thereof. The one or more materials used in said at least one back layer may comprise virgin materials, recycled materials, and combinations thereof. Here, it is for example imaginable and even preferred that the back layer comprises a mixture of wood and / or plant fibers, such as coconut fibers, and / or cotton; and at least one binding agent. Preferably, the back layer comprises wood in an amount of 20-60% by weight of the back layer, and a cotton based material, such as recycled jeans and / or raw cotton (virgin cotton), in an amount of 30-70% by weight of the back layer, and at least one binding agent, preferably in an amount of 1-7% by weight of the back layer. The back layer may be free of PVC and / or any other synthetic polymer. Optionally, the back layer may act as decorative layer (which does not require a separate decorative layer on top). The wear layer is at least partially composed of a thermoplastic material, such as PVC or (T)PU, and is more preferably at least partially composed of a PET and / or PET-v. The wear layer may be provided with a decoratively structured top surface, which decoratively structured top surface is preferably at least partially aligned with said printed decor. This alignment of structure (texture) and decor is also referred to as embossing in register (EIR).

[0072] A lacquer layer or other protective layer, in particular scratch resistant layer, may be applied on top of said wear layer. The protective layer and / or wear layer preferably comprises silicon oxide (SiO2). A finishing layer may be applied in between the decorative layer and the wear layer. The decorative layer will be visible and will be used to provide the panel an attractive appearance. To this end, the decorative layer may have a design pattern, which can, for example be a wood grain design, a mineral grain design that resembles marble, granite or any other natural stone grain, or a colour pattern, colour blend or single colour to name just a few design possibilities. It is imaginable and may even be preferred that the decorative layer comprises at least one recycled material and / or at least one natural material, such as e.g. wood, textile, and / or mixtures. The decorative layer may be free of PVC and / or any other synthetic polymer. Customized appearances, often realized by digital printing during the panel production process, are also imaginable. The decorative top structure may also be formed by a single layer. In an alternative embodiment, the decorative top structure is omitted, thus not applied, in the panel according to the invention. In this latter embodiment, the upper side of the core constitutes the upper side of the panel.

[0073] The decorative layer may at least partially be formed at least partially by a (digitally) printed plastic layer, in particular a thermoplastic layer, or a (digitally) printed film, in particular paper film or thermoplastic film. The plastic material, in particular the thermoplastic material, which is used can be of various nature, but may, for example be PVC, PU, in particular TPU, PP, PET, in particular v-PET. PET, in particular v-PET, may be a preferred material from a recyclability point of view. Preferably this (thermo)plastic layer or paper film is preferably a white plastic layer or white film, preferably an opaque white layer or opaque white film. White, and in particular opaque white, will provide a bright background which will reflect back to the viewer the light that travels through transparent ink colours. The decorative layer may also be formed by an ink layer printed, preferably digitally printed, either directly or indirectly onto the core. The decorative layer may at least partially made of at least one biobased material, such as a polymer, in particular TPU, based upon plant-based oils such as canola oil or castor oil, and / or biobased (v-)PET. Biobased (v-)PET is typically partly, often up to 30% by weight, produced from plant biomass, wherein more in particular at least one of the monomers, such as ethylene glycol, used to produce (v-PET) may be produced from renewable resources, currently mainly sugar or residues from the sugar industry. The decorative may additionally comprise mineral components such as chalk or talc or magnesium oxide. This combines sustainability with extremely high levels of resilience for an improved panel performance in terms of acoustic properties, indentation resistance, etcetera.

[0074] The decorative top structure may also comprise and / or constitute a carpet base having pile yams projecting upwardly therefrom. The pile yams can be made from a number of natural or synthetic fibres. Many types of yam are made differently though, wherein there are typically two main types of yam: spun and filament. The yams may be made of nylon but other suitable synthetic yams such as polyester, polypropylene, acrylic or blends thereof can be employed. The carpet tile may be either rigid or flexible. It is also conceivable that the base is free of any yam or fibres. The pile yams may consist of loop piles. It is however also possible that the pile yams consist of cut piles, twisted piles or any other suitable pile yams in for example a level- or multilevel configuration. The loop piles are possibly synthetic yams, such as nylon, polyester, polypropylene, acrylic or blends thereof. In the shown embodiment, the loop piles are tufted in the carpet base. The carpet base preferably also comprises a backing sheet, which can for example be a non-woven sheet, a woven sheet, a non-woven polyester sheet, a polypropylene sheet, a glass fibre scrim or tissue sheet or combinations thereof. The backing sheet typically acts as support structure (holding structure) for holding the yams. To more efficiently bond the tufts in position on the carpet base, and in particular on the backing sheet, preferably a pre-coat layer is applied. This pre-coat layer can for example be a latex layer.

[0075] In certain embodiments, the polymeric composition of the core layer may optionally comprise one or more additives selected from the group consisting of reinforcing fillers, impact modifiers, flame retardants, UV stabilizers, antioxidants, hydrolysis stabilizers, processing aids, and adhesion promoters. These additives may be incorporated individually or in any combination, depending on the desired mechanical, thermal, optical, or processing characteristics of the decorative panel. Non-limiting examples of suitable additives are described below.

[0076] The composition may comprise one or more reinforcing fillers, such as glass fibers, talc, or calcium carbonate. Glass fibers, for example, may be included in an amount of 5-30 wt.% (of the core layer) to enhance mechanical strength, stiffness, and dimensional stability of the panel, which is particularly advantageous for floor panel applications subject to compressive or flexural loads.

[0077] One or more impact modifiers may be incorporated to improve the toughness and resistance to brittle fracture of the polymer matrix. Suitable impact modifiers include core-shell polymers such as methacrylate-butadiene-styrene (MBS) or rubbery copolymers such as EPDM. These additives may be present in an amount of 2-10 wt.% (of the core layer) and are particularly beneficial for applications where edge or surface impact resistance is critical, such as wall or floor panels.

[0078] To improve fire safety, the composition may further comprise one or more halogen- free flame retardants, such as aluminium trihydrate (ATH), magnesium hydroxide (MDH), or organophosphorus compounds (e.g., DOPO derivatives). These flame retardants can reduce flammability and smoke generation, and may be included in an amount of 10-30 wt.% (of the core layer), thereby enhancing compliance with building fire safety standards (e.g., EN 13501 , ASTM E84).

[0079] For protection against degradation from ultraviolet (UV) radiation, the polymeric composition may include a UV stabilizing system comprising a UV absorber (e.g., benzotriazole or benzophenone derivatives) and / or a hindered amine light stabilizer (HALS). These stabilizers reduce discoloration and mechanical degradation of the polymer matrix during prolonged light exposure and may be included in a combined amount of 0.1-2 wt.% (of the core layer).

[0080] Antioxidants such as hindered phenols, phosphites, or thioesters may be added in an amount of 0.05-1 wt.% (of the core layer) to prevent thermal oxidative degradation during processing or long-term use. These are particularly useful in high-temperature extrusion or lamination processes.

[0081] To enhance resistance to hydrolytic degradation, particularly in humid environments, the composition may include carbodiimide-based hydrolysis stabilizers, such as Stabaxol®. These additives may be present in amounts of 0.1- 1 wt.% (of the core layer) and help preserve molecular weight and mechanical properties over time.

[0082] Processing aids and lubricants such as calcium stearate, zinc stearate, polyethylene waxes, or amide waxes may be used to improve melt flow, reduce viscosity, or prevent die buildup during processing. These may be used in amounts of 0.1-1 wt.%.

[0083] Where the core layer is combined with decorative films, backer layers, or other substrates, one or more adhesion promoters may be used. Examples include maleic anhydride grafted polyolefins or isocyanate-functionalized compounds. These improve interfacial bonding and reduce the risk of delamination during use or thermal cycling.

[0084] The selection and proportion of these additives may be optimized according to the specific application (e.g., floor, wall, or ceiling panel) and performance criteria, such as load-bearing capacity, flame retardancy, weatherability, or processing efficiency.

[0085] The panel thickness is typically situated in between 3 and 12 mm, preferably between 4 and 8 mm.

[0086] A second aspect of the invention relates to: a method of producing a core layer which is suitable as a core layer in a (decorative) panel according to the first aspect of the invention, wherein the method comprises the steps of: providing a quantity of copolymeric composition comprising a copolymeric variant of polyalkylene terephthalate, such as polyethylene terephthalate (v- PET), which is of virgin quality, recycled quality, or a mixture of both qualities, and which contains and / or comprises polymeric chains that are formed by polymerization of at least three types of monomer which are: o at least one alkylene glycol monomer (AG), such as an ethylene glycol (EG) monomer, or an analogue thereof, o a terephthalic acid (TPA) monomer, o and a third monomer which is a heterocyclic organic molecule (HOM) that is provided with two functional groups each of which is suitable for formation of an ester bond with at least one of the other two monomer types (AG / EG; TPA); extruding the quantity of the copolymeric composition, wherein the extruding is performed at a raised temperature and the extruded product is of a suitable format for forming the core layer; cooling, preferably an enhanced cooling, of the extruded product in order to impart the extruded product with a predetermined degree of crystallinity; dimensioning the obtained extruded product after cooling, such that it is conform the dimensions of the core layer.

[0087] In view of the method of producing a core layer via the above indicated steps, it is noted that the preferred features explained above in regard of the first aspect of the invention, analogously apply to the method according to the second aspect of the invention, in particular in regard of the preferred features specified for the three monomers and the copolymeric composition .

[0088] The above method achieves the provision of a core layer which is suitable for a decorative panel, wherein the core layer has advantageous properties already indicated above in regard of the first aspect of the invention. Some significant advantages in the particular context of the method of producing the core layer are:

[0089] - The v-PET compound was found to have an improved melt flow and melt strength and as such is more flexible and easier to process in comparison to PET. This advantage is especially significant in the context that the core layer is formed by extrusion of the polymeric composition from which the core layer is made. The v-PET compound has an inherent crystallinity which is less brittle than PET, and consequently renders an extruded article made from v-PET with an improved impact resistance over PET.

[0090] The invention also relates to the core layer for use in a panel, in particular a decorative panel, according to the invention.

[0091] In the method according to the second aspect of the invention, it is preferred that the copolymeric variant of polyethylene terephthalate (v-PET) of virgin quality has been obtained via a process comprising the steps of: a) preparing a reactive mixture which comprises: o an ethylene glycol (EG) monomer or an analogue thereof, o a terephthalic acid (TPA) monomer, o a third monomer which is a heterocyclic organic molecule (HOM) that is provided with two functional groups each of which is suitable for formation of an ester bond with at least one of the other two monomer types (EG; TPA); b) performing an esterification step of said mixture at a raised temperature and in the presence of an esterification catalyst; c) performing a polymerization step at a raised temperature; d) separating the polymerized product that is produced in step c) from the reactive mixture, so that v-PET of virgin quality is formed.

[0092] Further in the method according to second aspect of the invention, it is preferred that the copolymeric variant of polyethylene terephthalate (v-PET) of recycled quality has been obtained via a process comprising the steps of: a) decomposition of a used quantity of a copolymeric variant of polyethylene terephthalate (v-PET) which contains polymeric chains consisting of at least three types of monomer which are: o an ethylene glycol (EG) monomer or an analogue thereof, o a terephthalic acid (TPA) monomer, o and a third monomer which is a heterocyclic organic molecule (HOM) that is provided with two functional groups each of which is suitable for formation of an ester bond with at least one of the other two monomer types (EG; TPA); wherein the decomposition step involves the breaking of the polymeric chains into shortened polymeric chains; b) admixing of a chain extender to the decomposed quantity of v-PET that is obtained in step a), wherein the chain extender is a molecule that has the functionality to bond with at least two, preferably at least four, of the shortened polymeric chains; c) allowing the chain extender to react with at least a part of the shortened polymeric chains at a raised temperature, so that v-PET of recycled quality is formed.

[0093] In view of using a chain extender in the method for producing v-PET of recycled quality, it is noted that the preferred features that apply to the chain extender as set out above in view of the first aspect of the invention, analogously apply to the above defined method for producing v-PET of recycled quality.

[0094] A third aspect of the invention relates to: a method of producing a decorative panel according to the first aspect of the invention, which comprises the steps of: producing a core layer which is made from a polymeric composition which comprises a copolymeric variant of polyethylene terephthalate (v-PET) which consists of polymeric chains that are formed by polymerization of at least three types of monomer which are: o an ethylene glycol (EG) monomer or an analogue thereof, o a terephthalic acid (TPA) monomer, o and a third monomer which is a heterocyclic organic molecule (HOM) that is provided with two functional groups each of which is suitable for formation of an ester bond with at least one of the other two monomer types (EG; TPA); attaching a decorative layer directly or indirectly on a top surface of the core layer, wherein preferably the core layer is obtained by the method according to the second aspect of the invention.

[0095] Further embodiments of the invention are described in the non-limitative set of clauses presented below. Clauses

[0096] 1. Decorative panel (1 ), in particular a decorative floor panel, decorative ceiling panel, or decorative wall panel, comprising:

[0097] • at least one core layer (2), and

[0098] • a decorative layer (6) directly or indirectly affixed to a top surface of said core layer (2); wherein said at least one core layer (2) is at least partially made from a polymeric composition which comprises a copolymeric variant of polyalkylene terephthalate, such as polyethylene terephthalate (v-PET), which contains or comprises polymeric chains that are formed by polymerization of at least three types of monomer which are:

[0099] - at least one polyalkylene glycol monomer, such as an ethylene glycol (EG) monomer or an analogue thereof,

[0100] - a terephthalic acid (TPA) monomer,

[0101] - and a third monomer which is a heterocyclic organic molecule (HOM) that is provided with two functional groups each of which is suitable for formation of an ester bond with at least one of the other two monomer types (EG; TPA).

[0102] 2. Decorative panel according to clause 1 , wherein the heterocyclic organic molecule (HOM) contains a five-membered ring that is composed from four carbon atoms and one oxygen atom.

[0103] 3. Decorative panel according to clause 2, either wherein the five-membered ring is of a furan type which is an aromatic compound, or a hydrogenated furan type which is a non-aromatic compound, or wherein the third monomer is composed of a mixture of the furan type and the hydrogenated furan type.

[0104] 4. Decorative panel according to one of the preceding clauses, wherein the two functional groups of the heterocyclic organic molecule (HOM) are either two hydroxyl groups or two carboxyl groups, or a combination of one hydroxyl group and one carboxyl group. 5. Decorative panel according to one of the preceding clauses 2-4, wherein the two functional groups of the heterocyclic organic molecule (HOM) are attached to two different carbon atoms of the heterocyclic organic molecule.

[0105] 6. Decorative panel according to the combination of clause 5, wherein the two different carbon atoms to which the two functional groups are attached, are two carbon atoms which are either both in an alpha position or both in a beta position relative to the oxygen atom.

[0106] 7. Decorative panel according to one of the preceding clauses 3-6, wherein the third monomer is either of: i) a five-membered ring of the furan type which has two carboxyl groups attached to two different carbon atoms and which is an aromatic compound; or ii) a five-membered ring of the hydrogenated furan type which has two hydroxyl groups attached to two different carbon atoms and which is a non-aromatic compound.

[0107] 8. Decorative panel according to clause 7, wherein the furan type i) is 2,5-furandicarboxylate or 3,4-furandicarboxylate (FD), optionally comprising additional organic residue groups such as methyl groups, for instance dimethyl-2,5-furandicarboxylate or dimethyl-3,4-furandicarboxylate (DMFD); and the hydrogenated furan type ii) is 2,5-tetrahydrofurandimethanol, 3,4- tetrahydrofurandimethanol (THFDM), 2,5-dihydroxy-tetrahydrofuran or 3,4- dihydroxy-tetrahydrofuran (DHTHF), optionally comprising additional organic residue groups such as methyl groups.

[0108] 9. Decorative panel according to one of the preceding clauses, wherein the polymeric chains contain a first type of polyester units PU1 composed of an ester of an EG monomer with a TPA monomer, and a second type of polyester units PU2 composed of an ester of an HOM monomer with either a EG monomer or a TPA monomer, wherein the molar ratio of PU2 / PU1 is 5 / 95 up to 20 / 80, preferably up to 15 / 85. 10. Decorative panel according to one of the preceding clauses, wherein the polymeric chains have a EG / TPA molar ratio in a range from 40 / 60 up to 60 / 40.

[0109] 11 . Decorative panel according to one of the preceding clauses, wherein the core layer is made from the polymeric composition by extrusion of the polymeric composition into an extruded product of a suitable format.

[0110] 12. Decorative panel according to one of the preceding clauses, wherein the copolymeric variant of polyethylene terephthalate (v-PET) is of virgin quality, of recycled quality, or is a mixture of both qualities.

[0111] 13. Decorative panel according to one of the preceding clauses, wherein the copolymeric variant of polyethylene terephthalate (v-PET) contains polymeric chains which are extended by incorporation of a chain extender, wherein the chain extender is an additional molecule that is bonded with at least two, preferably at least four, of the monomers that are present in the polymeric chains of v-PET.

[0112] 14. Decorative panel (1) according to clause 13, wherein at least one chain extender is a multifunctional epoxide oligomer, preferably an epoxide oligomer having a chemical structure according to the formula: wherein

[0113] - R1-R5 are H, CH3, a higher alkyl group, or combinations of them;

[0114] - R6 is an alkyl group, and

[0115] - x, y, and z are each between 1 and 20.

[0116] 15. Decorative panel (1) according to clause 13 or 14, wherein at least one chain extender, is a molecule of a dianhydride type, preferably pyromellitic dianhydride (PMDA) and / or mellophanic dianhydride (MEDA). 16. Decorative panel (1) according to any of the preceding clauses, wherein the core layer is structured as a laminate of multiple core layers, containing at least two core layers that are made from the polymeric composition which comprises the copolymeric variant of polyethylene terephthalate (v-PET), wherein preferably an intermediate layer of different properties than v-PET is present between the two core layers of v-PET.

[0117] 17. Decorative panel (1) according to any of the preceding clauses, wherein the polymeric chains of v-PET have an average molar mass smaller than 20,000, preferably smaller than 15,000, more preferably smaller than 12,000 g / mol.

[0118] 18. Decorative panel (1) according to any of the preceding clauses, wherein the polymeric composition from which the core layer is made further includes an inorganic filler and / or an organic filler, wherein the total amount of filler in the core layer is at least 50 percent by weight of the core layer, preferably at least 60 percent by weight of the core layer, more preferably at least 70 percent by weight of the core layer, such as at least 75 percent by weight of the core layer

[0119] 19. Decorative panel (1) according to any of the preceding clauses, wherein the polymeric composition from which the core layer is made comprises at least one lubricant, for instance long-chain fatty acid compounds, preferably in an amount of not more than 1 percent by weight of the polymeric composition.

[0120] 20. Decorative panel (1) according to any of the preceding clauses, wherein the polymeric composition from which the core layer is made comprises at least one toughening agent, preferably in an amount of not more than 10 percent by weight of the core layer, more preferably in an amount of 3 to 8 percent by weight of the core layer.

[0121] 21 . Decorative panel (1 ) according to any of the preceding clauses, wherein the panel comprises one pair of opposing side edges (7,8) which are provided with complementary coupling profiles (9,10) allowing intercoupling of adjacent decorative panels, and preferably the panel comprises two pairs of opposing side edges (7,8 resp. 7’, 8’) each pair of which is provided with complementary coupling profiles (9,10 resp. 33,34) allowing intercoupling of adjacent decorative panels. 22. Decorative panel according to any of the preceding clauses, wherein the decorative layer comprises a plurality of layers, comprising at least one printed decor, in particular at least one digitally printed decor, and at least one transparent and / or translucent wear layer covering said printed decor.

[0122] 23. Decorative panel according to clause 22, wherein said printed decor is printed onto a film, such as a paper film or a thermoplastic film

[0123] 24. Decorative panel according to clause 23, wherein said thermoplastic film is a PET based film and / or a PET-v based film.

[0124] 25. Decorative panel according to any of clauses 22-24, wherein the wear layer is at least partially composed of a thermoplastic material.

[0125] 26. Decorative panel according to clause 25, wherein the wear layer is at least partially composed of a PET and / or PET-v.

[0126] 27. Decorative panel according to any of clauses 22-26, wherein the wear layer is provided with a decoratively structured top surface, which decoratively structured top surface is preferably aligned with said printed decor.

[0127] 28. Decorative panel according to any of clauses 22-27, wherein the decorative layer comprises a primer layer onto which the decor is printed, preferably digitally printed.

[0128] 29. Decorative panel according to any of clauses 22-28, wherein the decorative layer comprises a scratch resistant layer covering said at least one wear layer.

[0129] 30. Core layer for use in a decorative panel according to any of the preceding clauses.

[0130] 31 . Method of producing a core layer (2) which is suitable as a core layer in a decorative panel according to one of clauses 1-29, wherein the method comprises the steps of: providing a quantity of a copolymeric composition comprising a copolymeric variant of polyethylene terephthalate (v-PET) which is of virgin quality, recycled quality, or a mixture of both qualities, and which contains polymeric chains that are formed by polymerization of at least three types of monomer which are: o an ethylene glycol (EG) monomer or an analogue thereof, o a terephthalic acid (TPA) monomer, o and a third monomer which is a heterocyclic organic molecule (HOM) that is provided with two functional groups each of which is suitable for formation of an ester bond with at least one of the other two monomer types (EG; TPA); extruding the quantity of v-PET, wherein the extruding is performed at a raised temperature and the extruded product is of a suitable format for forming the core layer; cooling, preferably an enhanced cooling, of the extruded product in order to impart the extruded product with a predetermined degree of crystallinity; dimensioning the obtained extruded product after cooling, such that it is conform the dimensions of the core layer.

[0131] 32 Method according to clause 31 , wherein the copolymeric variant of polyethylene terephthalate (v-PET) of virgin quality has been obtained via a process comprising the steps of: a) preparing a reactive mixture which comprises: o an ethylene glycol (EG) monomer or an analogue thereof, o a terephthalic acid (TPA) monomer, o a third monomer which is a heterocyclic organic molecule (HOM) that is provided with two functional groups each of which is suitable for formation of an ester bond with at least one of the other two monomer types (EG; TPA); b) performing an esterification step of said mixture at a raised temperature and in the presence of an esterification catalyst; c) performing a polymerization step at a raised temperature; d) separating the polymerized product that is produced in step c) from the reactive mixture, so that v-PET of virgin quality is formed. 33. Method according to clause 31 or 32, wherein the copolymeric variant of polyethylene terephthalate (v-PET) of recycled quality has been obtained via a process comprising the steps of: a) decomposition of a used quantity of a copolymeric variant of polyethylene terephthalate (v-PET) which contains polymeric chains consisting of at least three types of monomer which are: o an ethylene glycol (EG) monomer or an analogue thereof, o a terephthalic acid (TPA) monomer, o and a third monomer which is a heterocyclic organic molecule (HOM) that is provided with two functional groups each of which is suitable for formation of an ester bond with at least one of the other two monomer types (EG; TPA); wherein the decomposition step involves the breaking of the polymeric chains into shortened polymeric chains; b) admixing of a chain extender to the decomposed quantity of v-PET that is obtained in step a), wherein the chain extender is a molecule that has the functionality to bond with at least two, preferably at least four, of the shortened polymeric chains; c) allowing the chain extender to react with at least a part of the shortened polymeric chains at a raised temperature, so that v-PET of recycled quality is formed.

[0132] 34. Method of producing a decorative panel (1) according to one of clauses 1-

[0133] 29, which comprises the steps of: producing a core layer (2), which is made from a polymeric composition which comprises a copolymeric variant of polyethylene terephthalate (v- PET) which consists of polymeric chains that are formed by polymerization of at least three types of monomer which are: o an ethylene glycol (EG) monomer or an analogue thereof, o a terephthalic acid (TPA) monomer, o and a third monomer which is a heterocyclic organic molecule (HOM) that is provided with two functional groups each of which is suitable for formation of an ester bond with at least one of the other two monomer types (EG; TPA); attaching a decorative layer directly or indirectly on a top surface of the core layer (2), wherein preferably the core layer (2) is produced by the method according to one of the clauses 31-33.

[0134] The present invention is further explained by the provision of some non-limitative examples of preferred embodiments of the invention in accordance with the appended figures, wherein:

[0135] - Figure 1 shows a perspective view of a decorative panel according to the invention;

[0136] - Figure 2 shows a cross-sectional view along the line B-B of the panel depicted in claim 1 ;

[0137] - Figure 3A shows a cross-sectional view along the line A-A of the panel depicted in claim 1 ;

[0138] - Figure 3B shows a cross-sectional view along the line A-A of a variant of the panel depicted in claim 1 ;

[0139] - Figure 4 shows a reaction scheme for producing a first copolymeric variant of polyethylene terephthalate, i.e. v-PET (I) according to the invention;

[0140] - Figure 5 shows a second copolymeric variant of polyethylene terephthalate, i.e. v-PET (II) according to the invention;

[0141] - Figure 6 shows a reaction scheme for forming a v-PET of a recycled quality according to the invention; and

[0142] - Figure 7 shows an alternative reaction scheme for forming a v-PET of a recycled quality according to the invention.

[0143] Figure 1 shows a decorative panel (1) having a top surface (3) and a bottom surface (4) which are vertically opposed to each other. The decorative panel (1) is of a rectangular format having two opposed side edges (7, 8) that are relatively short and two opposed side edges (7’, 8’) that are relatively long. The lines A-A and B-B indicate the direction of cross-sections of the panel as depicted in other figures. Both pairs of opposed side edges (7,8) and 7’, 8’) are provided with complementary coupling parts in the form of profiles that can be interconnected with each other (as shown in other figures), and by virtue of which a coupling of adjacent panels (1) to each other is made possible.

[0144] Figure 2 shows a cross-sectional view of the panel (1) depicted in fig. 1 , wherein the cross-section corresponds to the line B-B indicated in fig. 1. The panel (1) has a centrally located core layer (2), comprising a top surface (31) and a bottom surface (32). A backing layer (5) is directly attached onto the bottom surface (32) of the core layer. A decorative top layer (6) is indirectly attached onto the top surface (31) of the core layer, via an intermediate layer (30). As an alternative to the depicted configuration, the intermediate layer may be dispensed with, and the decorative layer may be directly attached to the core layer.

[0145] The decorative top layer (6) may be composed from a multitude of subsequent layers in accordance with embodiments commonly used in the art, e.g. an adhesive primer, a base coat, a transition layer, a - preferably digitally - printed decor, at least one wear layer, at least one structured layer (which may be integrated with or formed by said wear layer(s)), and a scratch resistant layer that ultimately forms the top surface of the panel.

[0146] The core layer (2) is made from a polymeric composition which comprises a copolymeric variant of polyethylene terephthalate (v-PET) in accordance with the invention as claimed and the description thereof.

[0147] Further in fig. 2, the two short opposite side edges (7, 8) of the panel (1), being provided with two complementary coupling parts (9, 10). These complementary coupling parts (9,10) are of such a design that two adjacent panels can be interconnected with each other by these coupling parts, thereby achieving an intercoupling of adjacent panels. The design of the complementary coupling parts is such that adjacent panels can be interconnected to each other by a mutual vertical movement of the complementary coupling parts (9,10) towards each other as will be further elucidated by the description below.

[0148] The first coupling part (10) is in the form of a downward tongue (11) and the second coupling part (9) is in the form of an upward tongue (12). The second coupling part (9) may comprise a single upward tongue (12), at least one upward flank (13) lying at a distance from the upward tongue and a single upward groove (14) formed between the upward tongue and the upward flank, wherein at least a part of a side (15) of the upward tongue facing toward the upward flank is inclined and extends in the direction of the normal (N1) of the upper side or top surface (3) of the core, and wherein optionally at least a part of a side (16) of the upward tongue facing away from the upward flank comprises a substantially rigid first locking element (17), a single downward tongue (11), at least one downward flank

[0149] (18) lying at a distance from the downward tongue, and a single downward groove

[0150] (19) formed between the downward tongue and the downward flank, wherein at least a part of a side (20) of the downward tongue facing toward the downward flank is inclined and extends in the direction of the normal (N2) of the lower side or bottom surface (4) of the core, and wherein the downward flank comprises a, preferably substantially rigid, second locking element (21) adapted for co-action with the first locking element of yet a further panel.

[0151] An upper or front side (22) of the upward tongue (12) is inclined, from a top side (22A) downwards towards the outside (16). The transition from the inside (15) of the upward tongue (12) to the top side (22A) forms an aligning edge (23). A similar construction is present on the other side, with an upper side (24) of the groove (19) being inclined. The aligning edge (25) on the downward tongue (11) is arranged on the outside (26) thereof. On both sides, the transition between the tongue (11 , 12) and the core (2) is formed by a bridge, being an upper bridge (27) on the downward tongue (11) side and a lower bridge (28) on the upward tongue (12) side. The transition (29) from the downward tongue (11) towards the inside thereof is shown rounded, to facilitate deformation.

[0152] Figure 3A shows schematically a cross-sectional view of two long side edges (7’, 8’) of two panels (1) as depicted in fig. 1 , which respective side edges are interconnected to each other by an angling movement. The cross-sectional view depicted in fig. 3A corresponds to the line A-A as indicated in fig. 1. The long side edges (7’, 8’) are provided with complementary coupling parts (33,34), being of an adapted tongue shape (33) and an adapted groove shape (34), which are adapted so as to allow for interconnecting both side edges with each other by an angling (i.e. a rotational) movement of the side edges with respect to each other.

[0153] It is noted that the layered structure shown in detail in fig. 2, is a also present in the panels (1) of fig. 3A, but is however not further shown for the sake of simplicity. Figure 3B shows, as an analogous variant of the panels shown in fig. 3A, a cross- sectional view of two panels (1) that are interconnected with each other, wherein a different design of the complementary coupling parts (33,34) as shown in fig. 3A is used. Also in the variant according to fig. 3B, the design of the complementary coupling parts (33,34) is such that the side edges (7’, 8’) can be interconnected with each other by an angling (i.e. a rotational) movement of the side edges with respect to each other.

[0154] Figure 4 shows a reaction scheme for producing a first copolymeric variant of polyethylene terephthalate, i.e. v-PET (I) according to the invention, which is produced in two steps, i.e. an esterification and a subsequent polymerization step.

[0155] The type of v-PET that is produced via the reaction scheme of fig. 4, consists of polymeric chains which are represented by structural formula v-PET (I), and are formed by polymerization of three types of monomer which are:

[0156] - an ethylene glycol (EG) monomer,

[0157] - a terephtalic acid (TPA) monomer,

[0158] - and a third monomer which is a heterocyclic organic molecule (HOM) that is provided with two functional groups each of which is suitable for formation of an ester bond with at least one of the other two monomer types (EG; TPA).

[0159] In the structural formula I of fig. 4, the third monomer is a five-membered ring of a hydrogenated furan type which has two hydroxyl groups attached to two different carbon atoms. In the scheme shown in fig. 4, THF-dimethanol (THFDM) is included as a third monomer, but also analogues, precursors or derivatives of THFDM that correspond to the above general indication of the third monomer may be used as an alternative to THFDM. During esterification and subsequent polymerization, the hydroxyl groups of the third monomer react with the carboxyl groups of the TPA monomers in order to form an ester bond.

[0160] It is noted that the esterification is preferably performed at a temperature between 200°C and 260°C and in the presence of an esterification catalyst which preferably is antimony trioxide (Sb2O3). The subsequent polymerization step is preferably performed at a further raised temperature of 260°C up to 300°C. The polymer v-PET (I) consequently consists of polymeric chains which are constructed of units that are dimers of either EG-TPA or of TPA-THFDM as indicated in structural formula I.

[0161] Figure 5 shows a second copolymeric variant of polyethylene terephthalate consisting of polymeric chains represented by structural formula v-PET (II), which are formed by polymerization of three types of monomer which are:

[0162] - an ethylene glycol (EG) monomer,

[0163] - a terephthalic acid (TPA) monomer,

[0164] - and a third monomer which is a heterocyclic organic molecule (HOM) that is provided with two functional groups each of which is suitable for formation of an ester bond with at least one of the other two monomer types (EG; TPA).

[0165] In the structural formula II of fig. 5, the third monomer is a five-membered ring of a furan type which has two carboxyl groups attached to two different carbon atoms. In fig. 5, dimethyl-2,5-furandicarboxylate (DMFD) is included as a third monomer, but also analogues, precursors or derivatives of DMFD that correspond to the above general indication of the third monomer may be used as an alternative to DMFD. During esterification and subsequent polymerization, the carboxyl groups of the third monomer react with the hydroxyl groups of the EG monomers in order to form an ester bond.

[0166] The copolymeric variant v-PET (II) can be produced via the same two-step process shown in fig. 4 for v-PET (I), provided that DMFD is used as third monomer instead of THFDM (as depicted in the reaction scheme of fig. 4).

[0167] The polymer v-PET (II) consequently consists of polymeric chains which are constructed of units that are dimers of either TPA-EG or of DMFD-EG as indicated in structural formula II.

[0168] The type of v-PET (I) and (II) when produced via the above indicate two-step process, are examples of the production of v-PET of virgin quality.

[0169] Figure 6 shows a reaction scheme for forming a v-PET of a recycled quality, using a quantity of decomposed v-PET (72) that bonds to a chain extender (74). In this context, the quantity of decomposed v-PET (72) has been produced by decomposing a used quantity of a copolymeric variant of polyethylene terephthalate v-PET. The decomposition of the used v-PET involves the breaking of the original polymeric chains into shortened polymeric chains so that the quantity (72) is obtained.

[0170] As an alternative to the scheme in fig. 6 wherein v-PET of recycled quality is formed, the indicated quantity of decomposed v-PET (72) may be replaced by a quantity of v-PET of virgin quality wherein the polymeric chains have an insufficient polymeric size for the intended purpose of the invention.

[0171] The chain extender (74) is a molecule which has the functionality to bond with at least two, preferably at least four, of the shortened polymeric chains of v- PET included in the quantity (72). The bonding is herein accomplished with carboxylic terminal groups of the shortened polymeric chains (72). As an example, Fig. 6 shows a chain extender (74) which is a multifunctional epoxide oligomer, i.e. an oligomer having four epoxide moieties which are capable to bond with the carboxylic terminal groups of the polymeric chains (72).

[0172] By virtue of bonding to the chain extender, it is possible to create from a number of shortened polymeric chains of v-PET (72), a larger polymeric v-PET molecule (75) which is suitable for its intended purposes, i.e. a v-PET having a sufficient polymeric chain size.

[0173] Fig. 7 shows, analogously to fig. 6, an alternative reaction scheme for forming a v- PET of a recycled quality, using a quantity of decomposed v-PET (72) that bonds to another type of chain extender (71). The chain extender (71) herein is a molecule which has the functionality to bond with at least two, preferably at least four, of the (shortened) polymeric chains of v-PET, in particular with hydroxylic terminal groups of the shortened polymeric chains (72). Fig. 7 shows a chain extender which is the molecule pyromellitic dianhydride (PM DA). As an alternative to PM DA, mellophanic dianhydride (MEDA) may be used as well.

[0174] The above-described inventive concepts are illustrated by several illustrative embodiments. It is conceivable that individual inventive concepts may be applied without, in so doing, also applying other details of the described example. It is not necessary to elaborate on examples of all conceivable combinations of the abovedescribed inventive concepts, as a person skilled in the art will understand numerous inventive concepts can be (re)combined in order to arrive at a specific application.

[0175] The “floor panel” according to the invention may also applied as wall covering element, ceiling covering element, or alternative covering element. In case in this document reference is made to a “floor tile” or “floor panel”, these expressions may be replaced by expressions like “tile”, “wall tile”, “ceiling tile”, “covering tile”. The panel is preferably a decorative panel comprising at least one decorative layer. It is also imaginable that at least one core layer, in particular an upper core layer, has a decorative character which does not require the presence of a separate decorative layer. This can e.g. be achieved by admixing at least one coloured pigment into said core layer.

[0176] It will be apparent that the invention is not limited to the working examples shown and described herein, but that numerous variants are possible within the scope of the attached claims that will be obvious to a person skilled in the art.

[0177] For the sake of clarity, it is noted that the verb “comprise” and conjugations thereof used in the above description have the meaning of not only “comprise”, but also include the meaning of the phrases “contain”, “substantially consist of’, “formed by” and conjugations thereof.

Claims

Claims1. Decorative panel (1 ), in particular a decorative floor panel, decorative ceiling panel, or decorative wall panel, comprising:• at least one core layer (2), and• a decorative layer (6) directly or indirectly affixed to a top surface of said core layer (2); wherein said at least one core layer (2) is at least partially made from a polymeric composition which comprises at least one copolymeric variant of polyalkylene terephthalate ,such as polyethylene terephthalate (v-PET), which contains or comprises polymeric chains that are formed by polymerization of at least three types of monomer which are:- an alkylene glycol (AG) monomer, such as ethylene glycol (EG) monomer, a terephthalic acid (TPA) monomer,- and a third monomer which is a heterocyclic organic molecule (HOM) that is provided with two functional groups each of which is suitable for formation of an ester bond with at least one of the other two monomer types (AG; TPA).

2. Decorative panel according to claim 1 , wherein the copolymeric variant of polyalkylene terephthalate is a copolymeric variant of polyethylene terephthalate (PET) and the alkylene glycol monomer is an ethylene glycol (EG) monomer.

3. Decorative panel according to claim 1 or 2, wherein the copolymeric variant of polyalkylene terephthalate is a copolymeric variant of polypropylene terephthalate (PPT) and the alkylene glycol monomer is a propylene glycol (PG) monomer.

4. Decorative panel according to any of the preceding claims, wherein the copolymeric variant of polyalkylene terephthalate is a copolymeric variant of polybutylene terephthalate (PBT) and the alkylene glycol monomer is a butylene glycol (BG) monomer.

5. Decorative panel according to any of the preceding claims, wherein the alkylene glycol monomer is ethylene glycol or an analogue thereof, wherein saidanalogue is preferably a structurally and functionally similar polyol, in particular diol, capable of participating in esterification.

6. Decorative panel according to claim 5, wherein the analogue to ethylene glycol monomer is a linear organic polyol, preferably a diol, having a chain of three up to eight carbon atoms.

7. Decorative panel according to claim 6, wherein the linear organic polyol comprises propylene glycol and / or a butylene glycol.

8. Decorative panel according to any of the preceding claims, wherein said core layer comprises one or more additives selected from the group consisting of reinforcing fillers, impact modifiers, flame retardants, UV stabilizers, antioxidants, hydrolysis stabilizers, processing aids, and adhesion promoters.

9. Decorative panel according to any of the preceding claims, wherein the heterocyclic organic molecule (HOM) contains a five-membered ring that is composed from four carbon atoms and one oxygen atom.

10. Decorative panel according to claim 9, either wherein the five-membered ring is of a furan type which is an aromatic compound, or a hydrogenated furan type which is a non-aromatic compound, or wherein the third monomer is composed of a mixture of the furan type and the hydrogenated furan type.11 . Decorative panel according to one of the preceding claims, wherein the two functional groups of the heterocyclic organic molecule (HOM) are either two hydroxyl groups or two carboxyl groups, or a combination of one hydroxyl group and one carboxyl group.

12. Decorative panel according to one of the preceding claims 9-11 , wherein the two functional groups of the heterocyclic organic molecule (HOM) are attached to two different carbon atoms of the heterocyclic organic molecule.

13. Decorative panel according to the combination of claim 12, wherein the two different carbon atoms to which the two functional groups are attached, are two carbon atoms which are either both in an alpha position or both in a beta position relative to the oxygen atom.

14. Decorative panel according to one of the preceding claims 9-12, wherein the third monomer is either of: i) a five-membered ring of the furan type which has two carboxyl groups attached to two different carbon atoms and which is an aromatic compound; or ii) a five-membered ring of the hydrogenated furan type which has two hydroxyl groups attached to two different carbon atoms and which is a non-aromatic compound.

15. Decorative panel according to claim 14, wherein the furan type i) is 2,5-furandicarboxylate or 3,4-furandicarboxylate (FD), optionally comprising additional organic residue groups such as methyl groups, for instance dimethyl-2,5-furandicarboxylate or dimethyl-3,4-furandicarboxylate (DMFD); and the hydrogenated furan type ii) is 2,5-tetrahydrofurandimethanol, 3,4- tetrahydrofurandimethanol (THFDM), 2,5-dihydroxy-tetrahydrofuran or 3,4- dihydroxy-tetrahydrofuran (DHTHF), optionally comprising additional organic residue groups such as methyl groups.

16. Decorative panel according to one of the preceding claims, wherein the polymeric chains contain a first type of polyester units PU1 composed of an ester of an EG monomer with a TPA monomer, and a second type of polyester units PU2 composed of an ester of an HOM monomer with either a EG monomer or a TPA monomer, wherein the molar ratio of PU2 / PU1 is 5 / 95 up to 20 / 80, preferably up to 15 / 85.

17. Decorative panel according to one of the preceding claims, wherein the polymeric chains have a EG / TPA molar ratio in a range from 40 / 60 up to 60 / 40.

18. Decorative panel according to one of the preceding claims, wherein the core layer is made from the polymeric composition by extrusion of the polymeric composition into an extruded product of a suitable format.

19. Decorative panel according to one of the preceding claims, wherein the copolymeric variant of polyethylene terephthalate (v-PET) is of virgin quality, of recycled quality, or is a mixture of both qualities.

20. Decorative panel according to one of the preceding claims, wherein the copolymeric variant of polyethylene terephthalate (v-PET) contains polymeric chains which are extended by incorporation of a chain extender, wherein the chain extender is an additional molecule that is bonded with at least two, preferably at least four, of the monomers that are present in the polymeric chains of v-PET.21 . Decorative panel (1 ) according to claim 13, wherein at least one chain extender is a multifunctional epoxide oligomer, preferably an epoxide oligomer having a chemical structure according to the formula:wherein- R1-R5 are H, CH3, a higher alkyl group, or combinations of them;- R6 is an alkyl group, and- x, y, and z are each between 1 and 20.

22. Decorative panel (1) according to claim 20 or 21 , wherein at least one chain extender, is a molecule of a dianhydride type, preferably pyromellitic dianhydride (PMDA) and / or mellophanic dianhydride (MEDA).

23. Decorative panel (1) according to any of the preceding claims, wherein the core layer is structured as a laminate of multiple core layers, containing at least twocore layers that are made from the polymeric composition which comprises the copolymeric variant of polyethylene terephthalate (v-PET), wherein preferably an intermediate layer of different properties than v-PET is present between the two core layers of v-PET.

24. Decorative panel (1) according to any of the preceding claims, wherein the polymeric chains of v-PET have an average molar mass smaller than 20,000, preferably smaller than 15,000, more preferably smaller than 12,000 g / mol.

25. Decorative panel (1) according to any of the preceding claims, wherein the polymeric composition from which the core layer is made further includes an inorganic filler and / or an organic filler, wherein the total amount of filler in the core layer is at least 50 percent by weight of the core layer, preferably at least 60 percent by weight of the core layer, more preferably at least 70 percent by weight of the core layer, such as at least 75 percent by weight of the core layer26. Decorative panel (1) according to any of the preceding claims, wherein the polymeric composition from which the core layer is made comprises at least one lubricant, for instance long-chain fatty acid compounds, preferably in an amount of not more than 1 percent by weight of the polymeric composition.

27. Decorative panel (1) according to any of the preceding claims, wherein the polymeric composition from which the core layer is made comprises at least one toughening agent, preferably in an amount of not more than 10 percent by weight of the core layer, more preferably in an amount of 3 to 8 percent by weight of the core layer.

28. Decorative panel (1) according to any of the preceding claims, wherein the panel comprises one pair of opposing side edges (7,8) which are provided with complementary coupling profiles (9,10) allowing intercoupling of adjacent decorative panels, and preferably the panel comprises two pairs of opposing side edges (7,8 resp. 7’, 8’) each pair of which is provided with complementary coupling profiles (9,10 resp. 33,34) allowing intercoupling of adjacent decorative panels.

29. Decorative panel according to any of the preceding claims, wherein the decorative layer comprises a plurality of layers, comprising at least one printed decor, in particular at least one digitally printed decor, and at least one transparent and / or translucent wear layer covering said printed decor.

30. Decorative panel according to claim 29, wherein said printed decor is printed onto a film, such as a paper film or a thermoplastic film31 . Decorative panel according to claim 30, wherein said thermoplastic film is a PET based film and / or a PET-v based film.

32. Decorative panel according to any of claims 29-31 , wherein the wear layer is at least partially composed of a thermoplastic material.

33. Decorative panel according to claim 32, wherein the wear layer is at least partially composed of a PET and / or PET-v.

34. Decorative panel according to any of claims 29-33, wherein the wear layer is provided with a decoratively structured top surface, which decoratively structured top surface is preferably aligned with said printed decor.

35. Decorative panel according to any of claims 29-34, wherein the decorative layer comprises a primer layer onto which the decor is printed, preferably digitally printed.

36. Decorative panel according to any of claims 29-35, wherein the decorative layer comprises a scratch resistant layer covering said at least one wear layer.

37. Method of producing a decorative panel, preferably one according to one of the claims 1-36, wherein the method comprises the steps of: providing a quantity of a copolymeric composition comprising a copolymeric variant of polyalkylene terephthalate which is of virgin quality, recycled quality, or a mixture of both qualities, and which contains polymeric chains that are formed by polymerization of at least three types of monomer which are:o an alkylene glycol (EG) monomer, o a terephthalic acid (TPA) monomer, o and a third monomer which is a heterocyclic organic molecule (HOM) that is provided with two functional groups each of which is suitable for formation of an ester bond with at least one of the other two monomer types (EG; TPA); extruding the quantity of v-PET, wherein the extruding is performed at a raised temperature and the extruded product is of a suitable format for forming a core layer which is suitable as a core layer in the decorative panel; cooling, preferably an enhanced cooling, of the extruded product in order to impart the extruded product with a predetermined degree of crystallinity; dimensioning the obtained extruded product after cooling, such that it is conform the dimensions of the core layer attaching a decorative layer directly or indirectly on a top surface of the core layer.

38. Method according to claim 37, wherein the copolymeric variant of polyalkylene terephthalate is a copolymeric variant of polyethylene terephthalate (v- PET) of virgin quality and has been obtained via a process comprising the steps of: a) preparing a reactive mixture which comprises: o an ethylene glycol (EG) monomer or an analogue thereof, o a terephthalic acid (TPA) monomer, o a third monomer which is a heterocyclic organic molecule (HOM) that is provided with two functional groups each of which is suitable for formation of an ester bond with at least one of the other two monomer types (EG; TPA); b) performing an esterification step of said mixture at a raised temperature and in the presence of an esterification catalyst; c) performing a polymerization step at a raised temperature; d) separating the polymerized product that is produced in step c) from the reactive mixture, so that v-PET of virgin quality is formed.

39. Method according to claim 37 or 38, wherein the copolymeric variant of polyalkylene terephthalate is a copolymeric variant of polyethylene terephthalate (v-PET) of recycled quality and has been obtained via a process comprising the steps of: a) decomposition of a used quantity of a copolymeric variant of polyethylene terephthalate (v-PET) which contains polymeric chains consisting of at least three types of monomer which are: o an ethylene glycol (EG) monomer or an analogue thereof, o a terephthalic acid (TPA) monomer, o and a third monomer which is a heterocyclic organic molecule (HOM) that is provided with two functional groups each of which is suitable for formation of an ester bond with at least one of the other two monomer types (EG; TPA); wherein the decomposition step involves the breaking of the polymeric chains into shortened polymeric chains; b) admixing of a chain extender to the decomposed quantity of v-PET that is obtained in step a), wherein the chain extender is a molecule that has the functionality to bond with at least two, preferably at least four, of the shortened polymeric chains; c) allowing the chain extender to react with at least a part of the shortened polymeric chains at a raised temperature, so that v-PET of recycled quality is formed.

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