Patent Application
20250019972
This application claims priority under 35 U.S.C. § 119 to Netherlands Patent Application No. 2035354, filed Jul. 12, 2023, which is incorporated herein by reference in its entirety.
The present invention relates to a panel. The invention further relates a method of manufacturing a panel.
Extruded resilient floor or wall panels typically comprise a core containing binders such as thermoplastic elastomers or flexible polymers. These binders are often thermoplastic polymers that have desirable properties, such as resistance against moisture, heat, and impact. Common binders are polyvinylchloride (PVC) and polypropylene (PP) or other thermoplastic polymers as they are easy to process in extrusion, calendaring, and thermolamination processes.
In addition to binders, extruded resilient floor or wall panels typically can comprise inorganic mineral fillers. These inorganic mineral fillers are usually added to the core of the extruded resilient floor or wall panel, and impart benefits such as increased thermal stability, increased rigidity and toughness, and an increased modulus of elasticity and hardness. Flame and smoke retardant properties can also be imparted by including certain inorganic mineral fillers in the core. However, the addition of inorganic mineral filler to the core is only beneficial up to a certain level, upper limit or saturation point. This so-called saturation point represents a point where the weight ratio between the binder and the inorganic mineral filler can no longer be increased without negatively affecting the panel properties. Past this point, differences in interfacial compatibility and adhesion between the inorganic mineral filler and the binder, which is typically a thermoplastic polymer, as well as an agglomeration of the inorganic mineral filler cause deterioration in tensile strength, impact strength, and compressive strength of the floor or wall panel. In addition, a steep decline in processing performance of the composition that is to be extruded to form the resilient floor, is observed. As inorganic mineral fillers are relatively inexpensive, increasing inorganic mineral filler content of the core decreases product costs and can provide benefits as described above. A weight ratio of at least 2.5:1 mineral filler to thermoplastic binder is preferred and even higher mineral filler to binder weight ratios can be desirable, such as 3:1, and even up to a saturation point of 3.5:1. The saturation point is dependent on the type and properties of inorganic mineral filler and the type of binder, and as such may differ from 3.5:1. To further increase the weight ratio between inorganic filler mineral filler and binder beyond this saturation point, it is known to add large quantities of plasticizers to a mixture of inorganic mineral filler and binder, to improve the core's plasticity during extrusion and to improve its flexibility and durability in use. The use of plasticizers allows to further increase the weight ratio of inorganic mineral filler to binder to 4:1 or even up to 4.5:1. Other additives such as waxes, lubricants, and coupling agents can also be utilized to improve the processibility of these high-mineral content polymeric compositions.
In general, a plasticizer content lies in the range of 2-3% by total weight of the panel. The addition of plasticizer is even more crucial when producing flexible resilient flooring for glue down installation, commonly called Luxury Vinyl Tile (LVT), through an extrusion process. The flexibility and deflection of LVT panels can be tested according to ISO 24344 or ASTM F137. LVT needs to be flexible enough to be bent 180° around a mandrel having a diameter of 25/38 mm when tested according to ISO 24344 or ASTM F137. To extrude flexible LVT with a relatively high mineral content, i.e., a mineral filler to thermoplastic binder weight ratio of at least 3.5:1, the plasticizer content should be increased to at least 4% by total weight of the panel, even up to 6% or 8% by total weight of the panel with increasing mineral content.
Nevertheless, the combination of a binder such as a thermoplastic elastomer or a flexible polymer binder, for example PVC or PP, a weight ratio of inorganic mineral filler to binder exceeding 3.5:1, and at least one plasticizer, poses multiple technical challenges. At least one mineral filler may comprise magnesium oxide, magnesium carbonate, magnesium oxysulphate, magnesium oxychloride cement (MOC), magnesium chloride (MgCl2), magnesium sulphate (MgSO4), Sorel cement, fiber cement, MOS cement, limestone, calcium carbonate, calcite mineral, stone, chalk, clay, calcium silicate and/or talc.
A first challenge is a relatively low surface energy of 24-32 dyn/cm of the core of a panel when the core comprises thermoplastic elastomers and/or flexible polymers. A surface energy of this range, measured according to ASTM D7490-13, is insufficient to allow for proper wetting, application, and adhesion of adhesives. One solution to this is to subject the back surface of the core to a corona or plasma treatment prior to the application of adhesive, which can achieve a limited increase of surface energy for at least a certain time. However, as this surface energy increase is limited in time, it is not a suitable solution for panels intended for glue down installation as the adhesive is applied when installing the panels, which could be weeks or months after production. Resilient panels with low surface energy are also expected to cause issues with adhesion and adhesive compatibility and are a main contributing factor or root cause in installation failures and quality complaints.
Plasticizers are low-molecular weight processing aids that improve processability. As touched upon above, an increase in mineral content of a core of a panel typically requires a corresponding increase in plasticizer content of the core. Plasticizers can be classified as internal plasticizers and external plasticizers. External plasticizers do not react with polymers. These are different from internal plasticizers which react with and make up part of a polymer chain. External plasticizers function by reducing the cohesive forces between polymer chains, and do not bond with these but are merely attracted to them through Van der Waals forces, weak intermolecular cohesive forces that occur between molecules due to temporary fluctuations in electron density. Plasticizers can weaken these cohesive forces by disrupting the intermolecular interactions between the chains, thereby making the polymer matrix more flexible and less brittle.
Plasticizer migration can occur when the weak intermolecular forces between the plasticizer and polymeric chains are overcome by other forces, or due to differences in concentration between the plasticizer within the polymer matrix and the surrounding or adjacent material. Exposure to heat can increase the speed of this migration as it increases the kinetic energy of the molecules, causing them to move more rapidly, making it easier to overcome the Van der Waals forces. Additionally, heat can also and simultaneously increase the permeability of the polymer matrix, allowing the plasticizers to migrate out of the material more easily. A plasticized extruded core present in a standard heterogeneous resilient floor or wall panel will therefore exhibit plasticizer migration to varying degrees.
A second challenge is then due to the attraction adhesives exert on plasticizers, resulting in the liquification of the adhesive layer. This attraction is due to the strongly polar or ionic nature of adhesives which attract, and interact with, polar or ionic functional groups on the plasticizer molecules. As the adhesive between panel layers liquefies, adherence between the layers is lost, and the layers start to separate or delaminate. Plasticizer migration may therefore directly affect the adhesive layer composition, and consequently lead to quality concerns. In the case of resilient decorative panels directly adhered to the substrate by means of an adhesive, this could mean catastrophic delamination. In the case of resilient wall panels adhered to a vertical substrate, this delamination can even cause safety concerns. Even in the case of a pre-attached or separately installed underlayment present underneath the floor panel, plasticizer migration could lead to the destruction of the polymeric structure of the underlayment, which might be weakened, or even break down or disintegrate. There is a market demand for more sustainable plasticizers, moving away from harmful but highly compatible orthophthalate plasticizers to less compatible terephthalate plasticizers, and even bioplasticizers. As such, plasticizer migration in panels represents a quality and additionally a safety risk that need to be addressed.
A third challenge is that the application of curable coatings on a panel can cause warpage of the panel, especially on panels comprising a high plasticizer content. Due to shrinkage of coatings during the curing process of the coating, the panel is pulled together, resulting in a panel that is not flat. Subsequent installation of such a warped panel on a floor or wall requires additional adhesive, to compensate for the curvature of the panel, and might lead to gapping and height differences between panels. The final adherence of the panel to the floor or wall is therefore not optimal.
It is therefore an object of the invention to provide a panel suitable for an enduring and strong adherence to a floor or wall.
In a first aspect, the invention provides thereto a panel, in particular a floor panel, wall panel or building panel, comprising: at least one core layer comprising at least one mineral filler, at least one polymeric binder, and optionally at least one plasticizer; and at least one coating layer located on a bottom surface of at least one core layer; wherein at least one coating layer preferably comprises an at least partly crosslinked polymer which is preferably impermeable to the plasticizer.
At least one coating layer, located on the bottom surface of the core layer provides a barrier at the bottom surface of the core layer that stops plasticizer from migrating through the coating layer. As such, when the panel is adhered to a substrate or surface with an adhesive, the adherence is maintained over a longer period of time, as the adhesive does not liquefy under the influence of the plasticizer. A mineral is a compound classified as a mineral by the International Mineralogical Association (The New IMA List of Minerals, updated May 2023). A mineral filler is thus a mineral that serves to fill another compound or material.
A plasticizer is a compound added to a material to soften the material and to increase its flexibility. Plasticizers can increase plasticity and decrease viscosity of a material. Depending on the size of the plasticizer, it is advantageous that the crosslinked polymer in the coating layer has a certain crosslink density to prevent migration of the plasticizer through the coating layer. Crosslink density is defined as the number of effective cross-links per unit volume or unit mass, in inverse relation to the molecular weight between cross-links (Mc).
Preferably, at least partially crosslinked polymer comprises a crosslinked polymeric network. Crosslinked polymeric networks comprise polymer chains that are held together with covalent bonds, and as such, form a network.
According to the present invention, the coating layer comprises an at least partially crosslinked polymer. The coating layer is applied to at least part of the bottom surface of the core layer. Prevention of migration of at least one plasticizer from the core layer through the coating layer, is achieved by the at least partly crosslinked polymer comprising a network of crosslinks and voids, defined by a crosslink density and a corresponding average void size. The crosslink density XLD of the at least partially crosslinked polymer in the coating layer according to the invention translates to the crosslinked polymeric matrix forming a plurality of voids having an average void diameter (Vdia).
A high crosslink density results in a relatively small average void diameter, a high volumetric density, a rigid cured composition, and a high shrinking rate. A low crosslink density results in a relatively large average void diameter, a low volumetric density, a flexible cured composition, and a small shrinking rate. Crosslinking density can be expressed as a percentage between 0% (no crosslinks) and 100% (fully crosslinked).
The crosslinked polymer is preferably formed by polymerizing and crosslinking at least one oligomer and at least one monomer by means of a photoinitiator. Preferably, the at least one monomer is an acrylic monomer. Assuming a typical molecular weight of the acrylic monomer unit to be around 100 g/mol, the density of the crosslinked polymer is estimated to be around 1.2 g/cm3. The void diameters for crosslink densities of 40%, 50%, 60%, and 70% then fall in the range of:
A 60%-70% crosslink density was experimentally and theoretically found to be a threshold crosslink density above which the average void diameter decreases exponentially. Through a controlled reduction of the average void diameter of the crosslinked polymer in the coating layer, an inert mechanical barrier can be formed through which plasticizer molecules are unable to migrate, without compromising the shrinking rate and rigidity or brittleness of the crosslinked polymer, and as such the coating layer.
In line with the above, the at least partially crosslinked polymer may have a crosslinking density (XLD) of at least 50%, more preferably at least 60%, most preferably at least 65%. In particular, the XLD can range between 60% and 75%, such as 65% to 70%. As a result, the crosslinked polymer will exhibit an optimal plasticizer sealing effect which can be measured through the plasticizer migration rate from the core layer through the at least one crosslinked polymer coat, which, when measured according to ISO 177:2016, is less than 0.1, more preferably less than 0.01 mg/cm2. The average diameter of voids within this crosslinked polymer, or crosslinked polymer network, is preferably less than 3 nm, more preferably less than 1.5 nm, most preferably less than 1 nm. Specifically, the average void diameter within the crosslinked polymer matrix is most preferably less than the average diameter of the at least one plasticizer. As such, the functioning of the crosslinked polymer and/or coating layer as a barrier or sealing layer which mechanically/physically impedes the diffusion/migration of the plasticizer to other layers is enhanced.
Another way to quantitate the amount of crosslinking in a polymer network is to quantify the number of remaining double bonds per molecular weight. Bifunctional methacrylates for example, are able to polymerize and form crosslinked three-dimensional polymer structures. The crosslinking of these structures can be identified by quantifying the remaining double bonds after crosslinking, or by the crosslink density (XLD). Typically, about 5-10 double bonds in a polymer of 1000 g/mol remain after crosslinking. In general, this corresponds to about 50-70% of the double bonds being utilized for crosslinking. The number of double bonds available for crosslinking is dependent on the polymer itself.
Preferably, the crosslinked polymer has a crosslink density in a range of 0.01-0.1 mol/g, preferably from 0.02-0.05 mol/g, more preferably from 0.025-0.035 mol/g, most preferably from 0.028-0.032 mol/g3, in particular measured according to ASTM D2765-16. Crosslink densities can be expressed in moles per unit weight or moles per unit volume. If the crosslinked polymer in the plasticizer sealing layer or coating layer is an acrylate polymer, its molecular weight typically lies in the range of 10000-50000 g/mol.
Preferably, the crosslinked polymeric network comprises a plurality of voids, and an average void diameter is preferably smaller or equal to twice a radius of gyration (Rg) of the plasticizer, or diameter of gyration. This effectively allows the crosslinked polymeric network to block plasticizer migration, without becoming brittle or inflexible. The diameter of gyration for a molecule, such as a plasticizer, is defined by the distribution of atoms around its centre of gravity. The diameter of gyration is given by the root-mean-square distance of the segments of a molecule from its centre of mass. For polymers, it can be a measure of size. This diameter of gyration of a molecule depends among others on the molecular weight, its structure (e.g., whether or not it is branched or crosslinked), and whether the molecule is swollen by a solvent.
Plasticizers can have a linear or cyclic structure, but their molecular weight is typically limited to the range of 100-3000 g/mol, and their diameter (i.e., 2 times their radius of gyration) typically ranges between 0.3 and 10 nm. A number of examples of plasticizers with their molecular weight (ranges) and void diameter (expressed as twice the radius of gyration) is given in Table 1.
Preferably, a plasticizer migration rate through the coating layer, in particular a plasticizer migration rate of the plasticizer, measured according to ISO 177:2016 is less than 0.01 mg/cm2, more preferably less than 0.005 mg/cm2, most preferably less than 0.001 mg/cm2. In line therewith, the coating layer is substantially impervious to the plasticizer.
In an embodiment, a weight ratio of the mineral filler to the polymeric binder is at least 3.5:1, preferably at least 4.0:1, and most preferably at least 4.5:1. The relatively high mineral filler content has a positive effect on wear resistance of the panel. However, mineral fillers are relatively brittle. In order for the panel to be sufficiently flexible, a relatively high plasticizer content is required. In line therewith, a weight percentage of the plasticizer is at least 4 wt. %, preferably at least 6 wt %, more preferably at least 8 wt. %, based on total weight of the core layer. The coating layer located at the bottom surface of the core layer prevents the plasticizer from migrating out of the core. In particular, when the panel is adhered to a surface, such as a floor, via an adhesive layer, the plasticizer in the core layer is prone to migrate towards the adhesive layer. The coating layer prevents this migration.
The binder may comprise a thermoplastic elastomer, a polymer having a glass transition temperature below 0° C., measured according to ISO 6721-11:2019, a biopolymer, synthetic resin, or any combination thereof. A thermoplastic is a polymer that softens and becomes pliable upon heating and solidifies upon cooling. The process of heating and cooling a thermoplastic and the associated transition from a pliable form to a solid form can be repeated almost indefinitely. An elastomer is a material comprising polymer chains that enable the elastomer to recover its shape after deformation. The thermoplastic elastomer may be selected from polypropylene (PP), polyethylene terephthalate (PET), polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), chlorinated polyethylene (CPE), or any combination thereof. The thermoplastic elastomer and the mineral filler should preferably be combinable to create a homogeneous melt prior to extrusion. The plasticizer is preferably evenly distributable throughout such a melt.
It is conceivable that the at least partially crosslinked polymer may comprise at least one carboxyl functional group and/or at least one amine functional group capable of reacting with the plasticizer. These functional groups can react with plasticizers to form covalent bonds, thus reducing mobility of the plasticizer. This is particularly advantageous in the case where a variance in void diameter of the crosslinked polymer exists, and at least part of the voids has a diameter, expressed as twice the radius of gyration of the plasticizer, exceeding the average diameter of the plasticizer. The capability of the at least partially crosslinked polymer to react with the plasticizer is a failsafe mechanism that ensures that the coating layer impedes the diffusion and migration of the plasticizer through the coating layer to other layers, such as an adhesive layer.
In contrast with the above, the crosslinked polymer may be inert to the at least one plasticizer. It can be advantageous that the crosslinked polymer does not react with the at least one plasticizer, such that the structure of the crosslinked polymer is maintained, and that plasticizer molecules are not extracted from the core layer. When the plasticizer molecules remain in the core layer, the panel retains its flexibility. This is particularly advantageous when a variance in void diameter is relatively low, for example wherein a void diameter ranges between the radius of gyration of the plasticizer and three times the radius of gyration of the plasticizer. In line therewith, the plasticizer may be an external plasticizer.
The plasticizer may be selected from diisononyl phthalate (DINP), diisodecyl phthalate (DIDP), diethylhexyl phthalate (DEHP), dibutyl phthalate (DBP), butyl benzyl phthalate (BBP), di(2-ethylhexyl) adipate (DEHA), di(2-ethylhexyl) sebacate (DOS), di(2-ethylhexyl) terephthalate (DOTP), diisononyl cyclohexane-1,2-dicarboxylate (DINCH), triethyl citrate (TEC), di(2-ethylhexyl) phthalate (DEHP), di-n-octyl phthalate (DNOP), diisobutyl phthalate (DIBP), di-n-hexyl phthalate (DNHP), diethyl phthalate (DEP), dicyclohexyl phthalate (DCHP), diethylene glycol dibenzoate (DEDB), epoxidized soybean oil (ESBO), citrates, citrate esters, castor oil derivatives, epoxidized vegetable oils, succinic acid esters, tartaric acid, sorbitol, polyethylene glycol, starch, epoxidized soybean oil (ESBO), tributyl citrate (TBC), acetyl tributyl citrate (ATBC), triethyl citrate A (TEC-A), triclocarban (TCC), bis(2-ethylhexyl) maleate, bis(2-ethylhexyl) fumarate, DOML (linseed oil), DOP (castor oil based), DEHT (castor oil), GEFA, ELO, ESO, EVO, ELOV, ELOVAT, DOSA, DOA, DIDA, DES, DBS, PEG, Lactic Acid, Oleic acid, PPG, PES, Paraffinic oils, naphthenic oils, esters, or any combination thereof. Any other type of plasticizer could also be used.
In an embodiment, the coating layer comprises at least one coupling agent. The coupling agent enables the coating layer to be adhered to another surface via, for example, an adhesive layer. The coupling agent is preferably added to an outer surface of the coating layer for optimally enhancing the adherence capabilities of the coating layer. In particular, the coupling agent comprises at least one organosilane. Organosilanes are molecules having at least a single covalent bond between a silicon atom and a carbon atom within the molecule. In particular, the chemical structure of organosilanes is R(4-n)—Si—(R′X)n, wherein n=1 or 2; X is an organofunctional group, such as vinyl, amino, methacryl, epoxy, or any other functional groups. X can be different functional groups when n>1. An organofunctional group is the same as an organic functional group, i.e., a functional group comprising at least one carbon atom. Organosilanes can form a bridging molecule attached to the coating layer, improving adhesion of the coating layer to another layer. As such, organosilanes are particularly suitable additives for the coating layer as these compounds further increase the surface energy of the coating layer, in particular a UV-curable plasticizer-resistant coating layer, and as such improve its adhesive properties. The increased surface energy of the coating layer increases its receptiveness to bonding with other materials, thereby promoting a better adhesion of the panel with the coating layer to other materials via an adhesive layer, through the formation of covalent bonds of the organosilane and the coating layer.
Preferably, a weight percentage of the at least one coupling agent is in the range of 0.5-5.0 wt. %, preferably 1.0-4.0 wt. %, more preferably 2.0-3.0 wt. %, most preferably 2.3-2.7 wt. %, based on total weight of the coating layer. These weight percentages were experimentally found to improve adhesion, surface wetting of the coating layer in an uncured condition, and an increased surface energy of the coating layer in a cured condition, making the coating layer more receptive to bonding with other materials.
The at least one coupling agent may be selected from aminosilanes, methacryloyx silanes, epoxy silanes, vinyl silanes, 3-Aminopropyltriethoxysilane, N-(2-Aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-Aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-Aminoethyl)-3-aminopropyltriethoxysilane, N-(6-Aminohexyl)aminopropyltrimethoxysilane, 3-Methacryloxypropyltrimethoxysilane, 3-Methacryloxypropyltriethoxysilane, 3-Methacryloxypropylmethyldimethoxysilane, 3-Methacryloxypropylmethyldiethoxysilane, 3-Methacryloxypropylphenyldimethylsiloxane, 3-Glycidoxypropyltrimethoxysilane, 3-Glycidoxypropylmethyldiethoxysilane, 3-Glycidoxypropyltriethoxysilane, 2,3-Epoxypropyltrimethoxysilane, 2,3-Epoxypropyltriethoxysilane, Vinyltrimethoxysilane, Vinyltriethoxysilane, Vinyltris(2-methoxyethoxy) silane, Vinyltriacetoxysilane, Vinyltriphenoxysilane, or any combination thereof.
Advantageously the coating layer may have a surface tension of at least 32 dyn/cm, preferably at least 34 dyn/cm, more preferably at least 36 dyn/cm, measured according to ASTM D7490-13 (2022). A disadvantage of a coating layer can be that its surface tension, or surface energy is generally below the surface energy required for installation of the panel using an adhesive. If the surface tension is at least 32 dyn/cm, the adhesion of the panel using an adhesive layer is sufficient. A surface tension above 32 dyn/cm, preferably above 34 dyn/cm, most preferably above 36 dyn/cm is preferred, as it further enhances adherence capabilities of the coating layer.
Preferably, the panel comprises a top layer located on a top surface of the core layer, preferably a decorative top layer. A decorative top layer provides for an aesthetically pleasing panel. Optionally, a second coating layer can be provided on the top surface of the core layer, in between the core layer and the top layer. Such a second coating layer may prevent migration of plasticizers from the core layer to the top layer.
It is conceivable that this second coating layer is designed to receive a decorative print. Therefore, in another exemplary embodiment of the present invention, an at least one digitally printed layer is provided with a digital embossing on the top surface of the core layer of the panel, with a coating layer on the back or bottom surface of the core layer for balancing.
In another embodiment of the present invention, the top surface of the panel and/or the decorative top layer comprises at least partially at least one viscoelastic coating layer and/or a thermoset coating, an at least partially digitally printed layer and/or an excimer cured coating layer. It is further conceivable that said viscoelastic coating layer comprises at least partially a tactile texture and/or an embossing provided thereon by chemical and/or mechanical means. It is also imaginable that at least one embossing layer is substantially viscoelastic.
The decorative top layer may comprise at least one décor layer and/or at least one protective layer. It is conceivable that at least one décor layer is attached to the core layer. It is also conceivable that the décor layer or the decorative layer itself is a print layer, in particular a digital print layer.
Preferably, the decorative top layer comprises a thermoset protective layer or an at least partially UV-cured protective layer. Additionally or alternatively, the crosslinked polymer may be a thermosetting resin. A thermosetting resin can cure, or harden, by undergoing crosslinking reactions to irreversibly form a three-dimensional network. Thermosetting resins are typically liquid prior to curing, and solid after curing. The curing process involves crosslinking, thereby solidifying the resin.
In a preferred embodiment, the decorative top layer comprises at least one décor layer and/or at least one wear layer. The wear layer could for example be scratch resistant layer. The decorative top layer may comprise a wear layer or finishing layer, for example with a thermosetting varnish or lacquer such as polyurethane, PUR, or a melamine-based resin. In a preferred embodiment, the top layer comprises at least one substantially transparent wear layer or finishing layer. The wear layer may comprise one or more transparent layers of a thermoplastic or thermosetting resin.
Non-limiting examples of thermoplastic or thermosetting resins which could be used are polyvinyl chloride (PVC), polystyrene (PS), polyethylene (PE), polyurethane (PU), acrylonitrile butadiene styrene (ABS), polypropylene (PP), Polyethylene terephthalate (PET), phenolic and/or melamine or formaldehyde resins. The wear layer may also be applied in a liquid or paste-like form made of a thermosetting resin such as but not limited to phenolic and/or melamine or formaldehyde resins. The wear layer may comprise or may be substantially composed of an inherently scratch-resistant thermosetting resin impregnating a carrier layer such as paper or lignocellulose. Typically, a preferred thickness of the wear layer lies within the range of 0.1 to 2.0 mm, more preferably between 0.15 mm to 1.0 mm and most preferably between 0.2 mm to 0.8 mm.
In an embodiment, the panel may comprise a decorative print provided by rotogravure printing or digital printing, a wood veneer, at least one ply of cellulose, a ceramic tile, and/or a stone veneer. It is for example possible that the décor layer comprises a plurality of impregnated layers containing lignocellulose but also a wood veneer, a thermoplastic layer, a stone veneer, a veneer layer or the like and/or a combination of said materials.
The veneer layer is preferably selected from the group comprising wood veneer, cork veneer, bamboo veneer, and the like. Other materials such as ceramic tiles or porcelain, a real stone veneer, a rubber veneer, a decorative plastic or vinyl, linoleum, and laminated decorative thermoplastic material in the form of foil or film. The thermoplastic material can be PP, PET, PVC and the like. The at least one thermoplastic may also be selected from Polylactic Acid (PLA), Polyhydroxyalkanoates (PHA), Polybutylene Succinate (PBS), Polyhydroxyurethane (PHU), Cellulose Acetate (CA), Starch-based Bioplastics, Polyethylene Terephthalate (PET), Polyglycolic Acid (PGA), Polyhydroxyalkanoate-Co-Valerate (PHA-V), Polybutylene Adipate Terephthalate (PBAT), and the like.
The decorative layer, décor layer, or decorative print may also form integral part of the core layer. In a beneficial embodiment of the panel, at least part of the upper surface of the core layer is provided with at least one decorative pattern or decorative image. It is for example possible that such decorative image or pattern is provided via printing, for example via digital and/or inkjet printing. It is also possible that at least one decorative pattern is formed by relief provided on the upper surface of the core layer or panel. It is also conceivable that the décor layer or decorative layer is a separate layer, for example a high-pressure laminate (HPL), a veneer layer, a directly laminated paper layer, and/or a ceramic tile.
The design of the decorative layer can be chosen from a design database which includes digitally processed designs, traditional patterns, pictures or image files, customized digital artworks, randomized image patterns, abstract art, wood-patterned images, ceramic or concrete style images, or user-defined patterns. The designs can be printed or reproduced using laser printers, inkjet printers, or any other digital printing means including conventional printing methods. Various types of inks can also be used to suit the design needs of the décor layer. Preferably, the ink used during the printing method comprises properties such as but is not limited to waterproofness, lightfastness, acid-free, metallic, glossy, sheen, shimmering, or deep black, among others.
It is preferred that the decorative layer is visually exposed by the coating layer being a substantially transparent coating layer. The décor layer may comprise a pattern, wherein the pattern is printed via digital printing, inkjet printing, rotogravure printing machine, electronic line shaft (ELS) rotogravure printing machine, automatic plastic printing machine, offset printing, flexography, or rotary printing press. The thickness of the decorative layer is preferably in the range of 0.05 mm to 0.10 mm, for example a thickness of 0.06 mm to 0.08 mm, such as 0.07 mm.
Preferably, the coating layer has a shrinking rate A when tested according to ISO 23999 and wherein the protective layer has a shrinking rate B when tested according to ISO 23999, wherein B<A, most preferably wherein A≈1.1·B. This achieves a balanced construction for the panel with a cupping and bending of the panel of less than 1 mm when tested at 80° C. according to ISO 23999.
In an embodiment, the core layer may comprise 10-40 wt. % of the binder, 20-60 wt. % of the mineral filler, and at least 4 wt. %, preferably at least 6 wt. %, most preferably at least 8 wt. % of the plasticizer, based on total weight of the core layer. A relatively high mineral filler and plasticizer content combine to provide a wear resistant, yet flexible panel. The use of a coating layer is particularly advantageous for these types of panels, due to their relatively high plasticizer content. Not only does the coating layer prevent the dissolving of an adhesive layer used to attach the panel to a surface, but it also prevents the core layer from becoming brittle, due to plasticizer molecules leaving the core layer.
The binder may be selected from polypropylene (PP), polyethylene terephthalate (PET), polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), chlorinated polyethylene (CPE), Polylactic Acid (PLA), Polyhydroxyalkanoates (PHA), Polybutylene Succinate (PBS), Polyhydroxyurethane (PHU), Cellulose Acetate (CA), Starch-based Bioplastics, Polyglycolic Acid (PGA), Polyhydroxyalkanoate-Co-Valerate (PHA-V), Polybutylene Adipate Terephthalate (PBAT), TPU, LDPE, LLDPE, HDPE, PS, HIPS, GPPS, PA, PETG, PPC, PC, ABS, PVDF, starch-based polymers, PHD, Bio-PE, LA, cellulose acetate, or any combination thereof.
Advantageously, the coating layer may have a thickness in a range of 0.01-0.30 mm, preferably 0.05-0.25 mm, more preferably 0.10-0.20 mm, most preferably 0.13-0.17 mm. A coating layer that is too thin, requires a very high crosslinking density to effectively block migration of plasticizer molecules. This high density reduces the flexibility of the coating layer and increases brittleness of the panel and as such is not desirable in a plasticized panel. It was experimentally found that a thickness in a range of 0.13-0.17 mm provides and optimal trade-off between the coating layer preventing migration of plasticizer molecules, while still being sufficiently flexible.
Preferably, the coating layer is formed by polymerizing and crosslinking at least one oligomer and at least one monomer, in particular, an acrylate oligomer and an acrylate monomer. The acrylate oligomer provides flexibility, adhesion, and abrasion resistance to the coating layer, while the acrylate monomer helps to control the crosslink density and improve the coating layer's mechanical properties. The coating layer also resists plasticizer migration by acting as a barrier that prevents diffusion and limits the mobility of the plasticizer molecules towards an adhesive layer, when the coating layer is present between the core layer and an adhesive layer. The coating layer as such resists plasticizer migration and provides a sealing function to the lower surface of the core layer of the panel. It can therefore be understood to function as a sealing layer and/or plasticizer sealing layer.
The at least one oligomer, and in particular the at least one acrylate oligomer, is selected from urethane acrylate oligomers, polyester-based urethane acrylate oligomers, aliphatic urethane acrylate oligomers, aromatic urethane acrylate oligomers, polyether-based urethane acrylate oligomers, waterborne urethane acrylate oligomers, polyester acrylate oligomers, unsaturated polyester acrylates, polyester acrylates, adhesion-promoting polyester acrylates, low-molecular weight polyester acrylates, water-reducible polyester acrylates, epoxy acrylate oligomers, bisphenol A epoxy acrylates, aliphatic epoxy acrylates, cycloaliphatic epoxy acrylates, low-viscosity epoxy acrylates, novolac epoxy acrylates, silicone acrylate oligomers, hydrophilic silicone acrylates, silicone acrylates, silicone-modified acrylates, low-viscosity silicone acrylates, and silicone-modified urethane acrylate.
In line with the above, the at least one monomer, and in particular the at least one acrylate monomer, may be selected from tetrahydrofurfuryl acrylate, pentaerythritol triacrylate, 2-hydroxyethyl acrylate (HEA), ethoxylated bisphenol A diacrylate (EBDA), trimethylolpropane triacrylate (TMPTA), isobornyl acrylate (IBOA), and cyclohexyl acrylate (CHA).
Preferably, the coating layer comprises a core-facing layer adjacent to the core layer and an opposite outward facing layer, wherein: the core-facing layer comprises at least partially reactive carboxylic and/or amine functional groups, the core-facing layer is substantially inert to the plasticizer, the outward facing layer comprises at least one organosilane, and/or the outward facing layer has a surface energy of at least 32 dyn/cm, preferably at least 34 dyn/cm, more preferably at least 36 dyn/cm, measured according to ASTM D7490-13 (2022).
In a second aspect, the invention relates to a composition for forming a coating layer, comprising:
A coating layer as described hereinabove can be formed with this composition. The photoinitiator is preferably capable of initiating the ultraviolet (UV) curing process of the composition. Advantageously, the composition may be a liquid composition, such that it can easily be applied to a core of a panel prior to curing. This composition can be applied to a panel, and the resulting coating layer has all the benefits as described hereinabove.
Preferably, the at least one acrylate oligomer is selected from urethane acrylate oligomers, polyester-based urethane acrylate oligomers, aliphatic urethane acrylate oligomers, aromatic urethane acrylate oligomers, polyether-based urethane acrylate oligomers, waterborne urethane acrylate oligomers, polyester acrylate oligomers, unsaturated polyester acrylates, polyester acrylates, adhesion-promoting polyester acrylates, low-molecular weight polyester acrylates, water-reducible polyester acrylates, epoxy acrylate oligomers, bisphenol A epoxy acrylates, aliphatic epoxy acrylates, cycloaliphatic epoxy acrylates, low-viscosity epoxy acrylates, novolac epoxy acrylates, silicone acrylate oligomers, hydrophilic silicone acrylates, silicone acrylates, silicone-modified acrylates, low-viscosity silicone acrylates, silicone-modified urethane acrylate, or any combination thereof.
The at least one acrylate monomer may be selected from tetrahydrofurfuryl acrylate, pentaerythritol triacrylate, 2-hydroxyethyl acrylate (HEA), ethoxylated bisphenol A diacrylate (EBDA), trimethylolpropane triacrylate (TMPTA), isobornyl acrylate (IBOA), cyclohexyl acrylate (CHA), or any combination thereof.
The at least one photoinitiator may be selected from alpha-hydroxy ketones, 2-hydroxy-2-methyl-1-phenylpropan-1-one (HMPP), 1-hydroxycyclohexyl phenyl ketone (HCPK), benzophenones, benzophenone (BP), 4,4′-bis(dimethylamino) benzophenone, phosphine oxides, bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide (TPO), 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, acylphosphine oxides, 2,4,6-trimethylbenzoyl-diphenylphosphineoxide (TPO-L), 2,4,6-trimethylbenzoylphenylphosphineoxide (TPO-P), iodonium salts, diphenyliodonium hexafluorophosphate (DPI-HFP), and (4-methylphenyl)-phenyliodonium hexafluoroantimonate (MPI-HFA), or any combination thereof.
The composition may comprise at least one organosilane. In particular a weight percentage of the at least one organosilane ranges between 0.5 and 5 wt %, based on total weight of the composition. This provides the advantages as disclosed hereinabove.
In line with the above, the at least one organosilane may be selected from aminosilanes, methacryloyx silanes, epoxy silanes, vinyl silanes, 3-Aminopropyltriethoxysilane, N-(2-Aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-Aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-Aminoethyl)-3-aminopropyltriethoxysilane, N-(6-Aminohexyl)aminopropyltrimethoxysilane, 3-Methacryloxypropyltrimethoxysilane, 3-Methacryloxypropyltriethoxysilane, 3-Methacryloxypropylmethyldimethoxysilane, 3-Methacryloxypropylmethyldiethoxysilane, 3-Methacryloxypropylphenyldimethylsiloxane, 3-Glycidoxypropyltrimethoxysilane, 3-Glycidoxypropylmethyldiethoxysilane, 3-Glycidoxypropyltriethoxysilane, 2,3-Epoxypropyltrimethoxysilane, 2,3-Epoxypropyltriethoxysilane, Vinyltrimethoxysilane, Vinyltriethoxysilane, Vinyltris(2-methoxyethoxy) silane, Vinyltriacetoxysilane, Vinyltriphenoxysilane, or any combination thereof.
In a third aspect, the present invention relates to a method of manufacturing a panel as disclosed hereinabove, comprising:
The core layer can be provided by mixing a mineral filler, a thermoplastic, a plasticizer and optionally additives together to form a thermoplastic melt. By extruding the thermoplastic melt, a core layer can be obtained. The core layer may comprise at least one plasticizer, as disclosed hereinabove for the panel.
Preferably a mass of the composition is applied to an area of the at least part of the bottom surface of the core layer in a range between 10 and 90 g/m2. Advantageously, the composition may be applied in an uncured state. This mass of the composition per unit area allows the coating layer, created by curing the composition, to effectively prevent migration of plasticizer molecules through the coating layer.
Preferably curing the composition comprises curing the composition with UV light, at least one excimer, pressure, infrared light, electron beam curing (EBC), temperature, or any combination thereof. Curing by UV light is an effective method of curing that can simply be affected with UV light. UV light has a wavelength shorter than visible light, but longer than X-rays. UV light has a wavelength typically ranging between 100 and 400 nm.
The panel according to the invention may further comprise at least one top layer, preferably a decorative top layer. Such decorative top layer may for example be a high-pressure laminate (HPL), a plurality of impregnated layers containing lignocellulose, a wood veneer, a thermoplastic layer containing at least a decorative layer and optionally a protective top layer, a stone veneer or the like, and/or a combination of said decorative layers. The decorative top layer may possibly also comprise at least one ply of cellulose-based layer and a cured resin, wherein the cellulose-based layer is preferably paper or kraft paper. Said ply of cellulose-based material may also be a veneer layer adhered to a top surface of the core layer. The veneer layer is preferably selected from the group consisting of wood veneer, cork veneer, bamboo veneer, and the like. Other decorative top layers that can be considered according to the invention include ceramic tiles or porcelain, a real stone veneer, a rubber veneer, a decorative plastic or vinyl, linoleum, and decorative thermoplastic film or foil which may be laminated with a wear layer and optionally a coating. Examples of thermoplastics may be PP, PET, PVC and the like. It is also possible to provide on the top facing surface of the core an optional primer and print the desired visual effect in a direct printing process. The decorative layer can receive a further finishing with a thermosetting varnish or lacquer such as polyurethane, PUR, or a melamine-based resin. The panel, and in particular the top layer could optionally comprise at least one gloss control layer. The panel, and in particular the top layer, could also comprise at least one, and preferably a plurality of acrylic coating layers.
It is further conceivable that the coating layer is provided on the bottom surface of core layer of the panel, wherein the coating layer is a viscoelastic coating layer, and/or thermoset coating layer, and/or an excimer cured coating layer.
It is conceivable that the wear resistant particles are scattered, at least partially enclosed or embedded, preferably completely enclosed or embedded, by an at least one coating layer. It is likewise conceivable that the wear resistant particles are scattered, at least partially enclosed or embedded, preferably completely enclosed and embedded by at least one coating and/or wear layer, such that the wear resistant particles are encapsulated by the at least one coating, and/or are encapsulated by the at least one wear layer, preferably by at least two wear layers, and/or by the at least one top layer.
It is likewise conceivable that the wear resistant particles are chosen from the group of aluminium oxide, corundum, silicon carbide, titanium dioxide, titanium oxide and/or diamond particles or diamond dust.
In a further embodiment, the at least one coating layer may further comprise antimicrobial, antiviral, antibacterial and/or antifungal agents.
In a preferred embodiment the panel comprises at least one acoustic backing adhered to the back side of the core layer. The backing layer may also be referred to as a cushioning or damping layer. Backing layers are typically made of polymeric materials such as, but not limited to, ethylene vinyl acetate (EVA), radiation cross-linked polyethylene (IXPE), expanded polypropylene (XPP), and/or expanded polystyrene (XPS) of low-density foam layer. However, it is also conceivable that the backing layer comprises non-woven fibers, such as natural fibers like hemp or cork, and/or recycled/recyclable materials, such as PET, felt, recycled carpet, and the like.
The invention will be elucidated based on the following non-limitative clauses.
The invention will now be elucidated on the basis of non-limitative exemplary embodiments shown in the following figures. Herein shows:
Within these figures, the same reference number refer to similar or equivalent technical features.
The panel 101 is adhered to the substrate 200 via an adhesive layer 107. Plasticizer molecules 108 have migrated from the core layer 102 of the panel 101 into the adhesive layer 107. The adhesive layer 107 has liquified as a result.
Curing of the coating layer 110 during manufacturing of the panel 101 has not only shrunk the coating layer 110 but has also crosslinked the oligomers and monomers within the coating to form a polymeric network. The polymeric network contains voids having a relatively small diameter, that prevent the plasticizer molecules 108 from migrating through the coating layer 110 into the adhesive layer 107. As a result, the adhesive layer 107 does not liquefy.
Referring now to
As further exemplified in the panel 101 installed on a substrate 200 as shown in
As shown in the panel 101 of
The panel 101 as shown in
The panel 101 in
Additionally, the size and distribution of voids can be influenced by the polymer's molecular weight, the degree of crosslinking, and the presence of any plasticizers or other additives. The network topology, such as the arrangement of crosslinks, also plays a role in determining the void structure.
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.
The verb “comprise” and conjugations thereof used in this patent publication are understood to mean not only “comprise”, but are also understood to mean the phrases “contain”, “substantially consist of”, “formed by” and conjugations thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2035354 | Jul 2023 | NL | national |
