Acrylate coating composition, and applications thereof

Abstract

An acrylate coating composition comprises - a first group of reactants consisting of one or more aliphatic urethane (meth)acrylate oligomers, wherein the aliphatic urethane (meth)acrylate oligomers have a molar mass higher than 750 g / mol; - a second group of reactants selected from one or more polyester (meth)acrylate oligomers having molar mass higher than 750 g / mol, from one or more unsaturated polyester resins having molar mass higher than 750 g / mol, or from combinations thereof; - a third group of reactants consisting of one or more acrylate reactive diluents having a molar mass lower than 750 g / mol; - at least one thermo-initiator; - at least one photo-initiator; and optionally additives.

Description

[0001] Acrylate coating composition, and applications thereof

[0002] The invention relates to an acrylate coating composition that can be applied on a substrate, e.g. on a resin-impregnated printed sheet of paper, and partially cured, thereby obtaining a partially cured acrylate coating layer. The partially cured acrylate coating layer can be thermally cured in a thermal pressing operation in which the acrylate coating layer is provided with a textured structure and is cured.

[0003] The thermal pressing operation can comprise laminating the substrate with its acrylate coating layer to a board, e.g. to a wood fiber board, in the production of a decorative panel.

[0004] W02020 / 095196A1, WO2021 / 224843 Al and W02020 / 072891A1 describe such processes and products, as well as acrylate coating compositions that can be used in such processes and products.

[0005] It is an objective of the invention to provide improved acrylate coating compositions for the production a textured coating layers.

[0006] The first aspect of the invention is an acrylate coating composition. The acrylate coating composition comprises - and preferably consists of

[0007] - a first group of reactants consisting of one or more aliphatic urethane (meth)acrylate oligomers, wherein the aliphatic urethane (meth)acrylate oligomers have a molar mass higher than 750 g / mol, and preferably lower than 8000 g / mol, and more preferably lower than 4500 g / mol;

[0008] - a second group of reactants selected from one or more polyester (meth)acrylate oligomers having molar mass higher than 750 g / mol (and preferably lower than 8000 g / mol, and more preferably lower than 4500 g / mol), from one or more unsaturated polyester resins having molar mass higher than 750 g / mol; or from combinations thereof;

[0009] - a third group of reactants consisting of one or more acrylate reactive diluents having a molar mass lower than 750 g / mol; - at least one thermo-initiator;

[0010] - at least one photo-initiator; and optionally additives, preferably non-reactive additives.

[0011] The acrylate coating composition of the invention is ideally suited for applying a coating layer on a substrate (e.g. on a resin-impregnated printed sheet of paper), and partially curing the coating layer by means of radiation energy to non-tacky state. The substrate comprising the partially cured coating layer can be processed in a thermal pressing operation using a structured press element, in which flow of the partially cured coating layer creates a texture in the coating layer and in which the thermal pressing operation cures the coating layer by addition reactions of the double bonds - acrylate double bonds and, if present, double bonds of unsaturated polyester resin - initiated by activation of the at least one thermo-initiator in the thermal pressing operation. The combination of the first group of reactants, the second group of reactants and the third group of reactants provides optimal processing conditions, in terms of viscosity of the acrylate coating composition for applying it, in terms of partial curing by means of radiation energy to non-tacky state, in terms of balanced reactivity in the thermal pressing operation - meaning that sufficient flow occurs in the coating layer to create the texture combined with efficient curing of the coating layer in its textured state - as well as excellent properties of the coating layer after being cured in the thermal pressing operation.

[0012] A coating layer with excellent transparency, no or only a very limited number of cracks, and excellent wear and scratch resistance is obtained.

[0013] The benefits related to the processing of the acrylate coating composition and the coating layer obtained from it are of particular importance when thick coating layers are applied with the acrylate coating composition, e.g. coating layers of 70 grams per square meter dry weight or more.

[0014] The thermal pressing operation can comprise laminating the substrate comprising the coating layer onto a board, e.g. onto a wood fiber board (e.g. a wood fiber board or a wood particle board) or onto a mineral based board (e.g. a cement based board, a gypsum board or a magnesium oxide based board). The substrate can be a resin-impregnated sheet of paper. The resin of the resin-impregnated sheet of paper, or a resin layer coating on it can provide the adhesion between the substrate and the board.

[0015] The one or more aliphatic urethane (meth)acrylate oligomers have the benefit of providing adhesion of the coating layer obtained from the acrylate coating composition to the substrate - e.g. an impregnated sheet of printed paper - onto which the acrylate coating composition is applied. Although not clear, the inventors believe that the excellent adhesion is provided by hydrogen bridges as well as by the high elasticity provided by the use of aliphatic urethane (meth)acrylate oligomers resulting in less shrinkage in the curing process, shrinkage which would hinder the creation of adhesion.

[0016] The second group of reactants of the acrylate coating composition balances the reactivity in the radiation induced partial curing step and in the thermally induced curing operation in the thermal pressing operation, as the much more reactive aliphatic urethane (meth)acrylate oligomers could - when used on their own - create problems as the curing reactions would be too fast, which could result in inhomogeneous curing and in cracks caused by curing reactions happening too fast.

[0017] The introduction of the third group of reactants (which are the one or more acrylate reactive diluents) in the acrylate coating composition not only reduces the viscosity of the acrylate coating composition to facilitate its application, but also introduces small molecules in the acrylate coating composition which create effective crosslinking beneficial for the wear and scratch resistance of the coating layer, but which also create steric hindrance during the radiation curing process, preventing excessive speed when curing. Excessive speed in curing which would be negative for the uniformity of the curing as well as for the properties of the coating layer after its thermal curing in a thermal pressing operation. Too fast curing in the thermal pressing operation would cause fast curing of the surface of the coating layer, resulting in cracks as the texture cannot be properly copied from the structured press element used in the thermal pressing operation using a textured press element. The third group of reactants preferably provides between 30 and 60 wt%, and more preferably between 35 and 45 wt%, of the combination of the first group of reactants, the second group of reactants and the third group of reactants. Such embodiments have shown to provide excellent performance in applying the acrylate coating composition, in partially curing it and in the thermal pressing operation.

[0018] The first group of reactants preferably provides between 50 and 80 wt%, and more preferably between 55 and 75 wt%, of the combination of the first group or reactants and the second group of reactants.

[0019] Such embodiments are beneficial thanks to the excellent adhesion properties of the first group of reactants.

[0020] The combination of the first group of reactants, the second group of reactants and the third group of reactants preferably provides at least 80 wt%, and preferably at least 85 wt% of the acrylate coating composition.

[0021] The acrylate coating composition of this embodiment provides room for additives in the acrylate coating composition, such as wear resistance increasing particles (e.g. aluminum oxide particles, e.g. 10 percent by weight of the acrylate coating composition), one or more thermo-initiators, one or more photo-initiators, wetting agent (e.g. 3 percent by weight), a matting agent and one or more crosslinkers (e.g. in a combined amount of up to 5 or up to 7 percent by weight of the acrylate coating composition).

[0022] The acrylate coating composition can comprise either one or more polyester (meth)acrylate oligomers having molar mass higher than 750 g / mol (and preferably lower than 8000 g / mol, and more preferably lower than 4500 g / mol), or one or more unsaturated polyester resins having molar mass higher than 750 g / mol.

[0023] The acrylate coating composition can comprise one or more polyester (meth)acrylate oligomers having molar mass higher than 750 g / mol (and preferably lower than 8000 g / mol and more preferably lower than 4500 g / mol), as well as one or more unsaturated polyester resins having molar mass higher than 750 g / mol.

[0024] A preferred embodiment is characterized in that the average acrylate functionality of the one or more aliphatic urethane (meth)acrylate oligomers is between 1.5 and 4.5. Such embodiment provides an acrylate coating composition that provides an excellent coating layer after the thermal pressing operation, as cracks are prevented which could occur by too fast curing in combination with an excessive crosslinking density. Too fast thermally induced addition reactions in the thermal pressing operation would hinder the flow of the coating layer required for providing the texture in the acrylate coating layer.

[0025] The third group of reactants preferably comprises less than 3 wt% - and more preferably less than 1 wt%, more preferably less than 0.5 wt% - of methacrylate reactive diluents relative to the combination of the first group of reactants, the second group of reactants and the third group of reactants.

[0026] Such embodiments have the benefit that tackiness of the coating layer is much better prevented after its partial curing by means of radiation energy. The inventors have observed that the introduction of - especially an excessive amount of - methacrylate reactive diluents creates more difficulties to cure the coating layer to non-tacky state.

[0027] More preferably, the acrylate coating composition does not comprise methacrylate reactive diluents.

[0028] The acrylate reactive diluents preferably have an average acrylate functionality of at least 2, and preferably less than 4. Such embodiments have shown to provide an excellent combination of flow and curing in the thermal pressing operation, as well as after the thermal pressing operation, a textured coating layer with excellent wear resistance. When the average acrylate functionality of the acrylate reactive diluents is too high, the acrylate coating layer risks to be too brittle, due to a too dense crosslinking density in the acrylate coating layer. The third group of reactants - even if it has average acrylate functionality between 2 and 4 - may comprise reactive diluents having different acrylate functionality, e.g. reactive diluents having acrylate functionality 2, reactive diluents having acrylate functionality 3, having acrylate functionality 4, reactive diluents having acrylate functionality 5, or even reactive diluents having acrylate functionality 6.

[0029] A preferred embodiments is characterized in that the third group of reactants comprises on the one hand acrylate reactive diluents having acrylate functionality equal to 2 and on the other hand acrylate reactive diluents having acrylate functionality equal to 3 or 4, or both.

[0030] Such embodiments have shown to balance appropriately the kinetics of the curing mechanisms in a radiation induced partial curing and in the thermally induced curing in a thermal pressing operation.

[0031] In a preferred embodiment the third group of reactants comprises on the one hand acrylate reactive diluents having acrylate functionality equal to 2 and on the other hand acrylate reactive diluents having acrylate functionality equal to 3 or 4 (or both) in a mass ratio between 2: 1 and 1 :2, and more preferably between 1.5: 1 and 1 : 1.5.

[0032] A preferred acrylate coating composition does not comprise acrylate reactive diluents having acrylate functionality equal to one. Reactive diluents having acrylate functionality equal to one risk that they do not react in a radiation induced partial curing step. It means that they could leach out of the partially cured coating layer during storage prior to use in a thermal pressing operation. Such leaching could create tackiness issues of the partially cured acrylate coating layer.

[0033] The at least one thermo-initiator preferably provides less than 1.5 wt%, and more preferably less than 1 wt%, and even more preferably less than 0.5 wt% of the combination of the first group of reactants, the second group of reactants and the third group of reactants. Thanks to the preceding radiation induced partial curing and the use of a thermal pressing operation for the thermal curing - thermal pressing in which oxygen is prevented by the closed press from inhibiting curing reactions - the amount of thermo-initiator in the acrylate coating composition can be kept low.

[0034] The at least one photo-initiator preferably provides less than 1.5 wt%, more preferably less than 0.75 wt%, more preferably less than 0.35 wt%, and even more preferably less than 0.2 wt%, of the combination of the first group of reactants, the second group of reactants and the third group of reactants.

[0035] The amount of photo-initiator can be kept low as the photo-initiator is only required for inducing a radiation induced partial curing, preferably to non-tacky state. The composition of the acrylate coating composition of the invention is tailored for use of such low amount of photo-initiator.

[0036] A preferred acrylate coating composition is characterized in that the first group of reactants and the second group of reactants do not comprise methacrylate oligomers.

[0037] A preferred acrylate coating composition is characterized in that the second group of reactants comprises either one or more unsaturated polyester (meth)acrylate oligomers or one or more non-unsaturated polyester (meth)acrylate oligomers. Such embodiments are beneficial as they keep the complexity of the acrylate coating composition low.

[0038] A preferred acrylate coating composition is characterized in that the second group of reactants comprises one or more unsaturated polyester (meth)acrylate oligomers as well as one or more non-unsaturated polyester (meth)acrylate oligomers. Such embodiments optimize the composition of the acrylate coating composition for optimized process performance and properties of the final acrylate coating layer.

[0039] A more preferred acrylate coating composition is characterized in that the second group of reactants comprises one or more unsaturated polyester (meth)acrylate oligomers as well as one or more non-unsaturated polyester (meth)acrylate oligomers, wherein the mass ratio of the one or more unsaturated polyester (meth)acrylate oligomers to the one or more non-unsaturated polyester (meth)acrylate oligomers is between 0.5 - 2. Such embodiments optimize the composition of the acrylate coating composition for optimized process performance and properties of the final acrylate coating layer.

[0040] The second group of reactants preferably comprises polyester (meth)acrylate oligomers having acrylate functionality at least 2.5; more preferably all polyester (meth)acrylate oligomers in the acrylate coating composition have acrylate functionality at least 3. Such embodiments optimize the composition of the acrylate coating composition for optimized process performance and properties of the final acrylate coating layer.

[0041] A preferred acrylate coating composition is characterized in that the acrylate coating composition comprises besides the first group of reactants, the second group of reactants and the third group of reactants and relative to the combined amount of reactive monomers, reactive oligomers and reactive resins less than 4 wt% (and preferably less than 3 wt%, more preferably less than 2 wt%, more preferably less than 1 wt%, more preferably less than 0.5 wt%, even more preferably less than 0.2 wt%) of reactive components.

[0042] The coating composition can comprise a wetting agent, e.g. in an amount between 1.5 and 3 wt% of the acrylate coating composition. An example of such wetting agent is silicone acrylate.

[0043] The one or more thermo-initiators preferably comprise a first thermo-initiator and a second thermo-initiator, wherein the 60 seconds half-life of the second thermo-initiator is at least 8°C higher than the 60 seconds half-life of the first thermo-initiator.

[0044] Such embodiment is beneficial as it allows a gradual thermally induced curing in the thermal pressing operation in which the acrylate coating layer is textured by using a textured press element. The gradual curing ensures that sufficient flow in the acrylate coating layer is ensured during the pressing operation, such that the textured press element can press a texture in the acrylate coating layer and the acrylate coating layer is thermally cured in the textured state. Such embodiment is especially beneficial when deep structures are to be pressed in the acrylate coating layer during the thermal pressing operation.

[0045] The one or more thermo-initiators preferably comprise a third thermo-initiator, wherein the 60 seconds half-life of the third thermo-initiator is at least 8°C higher than the 60 seconds half-life of the second thermo-initiator.

[0046] Such embodiment has the same benefit as when only a first thermo-initiator and a second thermo-initiator are used, but to a larger extent.

[0047] The one or more thermo-initiators may even comprise a fourth thermo-initiator, wherein the 60 seconds half-life of the fourth thermo-initiator is at least 8°C higher than the 60 seconds half-life of the third thermo-initiator.

[0048] Such embodiment has the same benefit as when only a first thermo-initiator, a second thermo-initiator and a third thermo-initiator are used, but to a larger extent.

[0049] The acrylate coating composition preferably comprises at least one additive, wherein the at least one additive comprises a metal soap. The metal soap may be selected from a sodium soap, a zinc soap or a bismuth soap. The metal soap can be a saturated metal soap or an unsaturated metal soap.

[0050] The inventors have observed that the use of a metal soap allowed to realize deep textures (which require sufficient flow of the acrylate coating layer during the thermal pressing operation) in the acrylate coating layer in the thermal pressing operation while the press time could be kept short, which is beneficial for a high productivity of the thermal pressing operation.

[0051] An example of a metal soap that can be used in the invention is bismuth neodecanoate. The acrylate coating composition may comprises additives, wherein the additives comprise abrasion resistant particles, e.g. aluminum oxide particles, nanosilica particles, diamond particles, or siliconcarbide particles. Abrasion resistant particles are more preferably present in an amount between 0.5 and 15 wt% of the acrylate coating composition.

[0052] The acrylate coating composition may comprise abrasion resistant particles - e.g. aluminum oxide - having S50 particle size between 40 and 90 micrometer, and / or may comprise abrasion resistant particles - e.g. aluminum oxide - having S50 particle size between 5 - 30 micrometer.

[0053] The S50 particle size, determined from the cumulative particle size distribution according to volume measured by laser diffraction in accordance with ISO 13320:2020, is the particle size at which 50% of the hard particles are smaller than this particle size S50.

[0054] Abrasion resistant particles having S50 particle size between 40 and 90 micrometer provide increased abrasion resistance.

[0055] Abrasion resistant particles having S50 particle size between 5 - 30 micrometer have the benefit that they provide improved scratch resistance to the acrylate coating layer obtained from the acrylate coating composition.

[0056] Acrylate coating compositions according to the invention comprising abrasion resistant particles having S50 particle size between 5 - 30 micrometer are preferably applied as a top coating layer, preferably above a previously applied first acrylate coating layer which is preferably also obtained from an acrylate coating composition according to the invention.

[0057] Such embodiments provide coated products with increased resistance to scratches and micro scratches. Such embodiments are of particular interest for application in floor pnels. The acrylate coating composition may comprise a hindered amine light stabilizer as an additive. Such acrylate coating compositions result in acrylate coating layers having improved performance, as the risk of yellowing of the acrylate coating layer is reduced.

[0058] The acrylate coating composition may comprise a matting agent, preferably wherein the matting agent provides between 2 and 14 wt% - and more preferably between 3 and 10 wt% - of the acrylate coating composition.

[0059] A preferred matting agent for use in the invention is amorphous silica, preferably having numerical average particle size between 3 and 20 micrometer. The numerical average particle size can be determined using laser diffraction in accordance with ISO 13320:2020.

[0060] A texture can be pressed in the acrylate coating layer in a thermal pressing operation by means of a textured press element. The required texture of the acrylate coating layer can comprise a macro texture and a micro texture (which results in the gloss / matte appearance), e.g. for imitating a wood surface. The inventors have noticed that when a high and fine microstructure is required, it can be difficult to obtain the required matte level just by copying the texture of the textured press element. This has been resolved by modifying the texture of the textured press element and adding the matting agent to the acrylate coating composition such that the matting agent in the acrylate coating composition can compensate for the difference between the matte level which is required and the matte level provided by the microstructure of the textured press element.

[0061] The second aspect of the invention is an acrylate coating composition. The acrylate coating composition comprises

[0062] - one or more (meth)acrylate oligomers, wherein the aliphatic urethane (meth)acrylate oligomers have a molar mass higher than 750 g / mol, and preferably lower than 8000 g / mol, and more preferably lower than 4500 g / mol;

[0063] - one or more acrylate reactive diluents having a molar mass lower than 750 g / mol, preferably wherein the acrylate reactive diluents have an average acrylate functionality of at least 2; - at least one thermo-initiator;

[0064] - optionally at least one photo-initiator;

[0065] - a matting agent, preferably wherein the matting agent provides between 2 and 14 wt% (and more preferably between 3 and 10 wt%) of the acrylate coating composition; and optionally additives.

[0066] In a similar way as the acrylate coating composition of the first aspect of the invention, the acrylate coating composition of the second aspect of the invention is ideally suited for applying a coating layer on a substrate (e.g. on a resin-impregnated printed sheet of paper), and partially curing the coating layer by means of radiation energy to non-tacky state. The substrate comprising the partially cured coating layer can be processed in a thermal pressing operation using a structured press element, in which flow of the partially cured coating layer creates a texture in the coating layer and in which the thermal pressing operation cures the coating layer by addition reactions.

[0067] A texture can be pressed in the acrylate coating layer in a thermal pressing operation by means of a textured press element. The required texture of the acrylate coating layer can comprise a macro texture and a micro texture (which results in the gloss / matte appearance), e.g. for imitating a wood surface. The inventors have noticed that when a high and fine microstructure is required, it can be difficult to obtain the required matte level just by copying the texture of the textured press element. This has been resolved by modifying the texture of the textured press element and adding the matting agent to the acrylate coating composition such that the matting agent in the acrylate coating composition can compensate for the difference between the matte level which is required and the matte level provided by the microstructure of the textured press element.

[0068] A preferred acrylate coating composition of the second aspect of the invention is characterized in that the matting agent is an amorphous silica, more preferably having average particle size between 3 and 20 micrometer. The average particle size is the numerical average particle size and can be determined using laser diffraction in accordance with ISO 13320:2020. The acrylate coating composition of the second aspect of the invention can comprise features as mentioned for the acrylate coating compositions of the first aspect of the invention.

[0069] A preferred acrylate coating composition of the first aspect or of the second aspect of the invention is characterized in that the acrylate coating composition comprises a crosslinker, more preferably selected from an isocyanate, an aziridine or a carbo-diimide, or combinations thereof.

[0070] Such embodiments provide for an improved cross-linking of the coating layer obtained from the acrylate coating composition, resulting is improved wear resistance, including increased scratch resistance.

[0071] The third aspect of the invention is a method of applying a coating layer onto a carrier substrate. The method comprises the steps of

[0072] - providing a carrier substrate;

[0073] - applying an acrylate coating composition according to the first aspect or according to the second aspect of the invention onto the carrier substrate, thereby obtaining a coating layer on the carrier substrate; and

[0074] - partially curing the coating layer, preferably to non-tacky state.

[0075] The carrier substrate can be a filled sheet of paper. More preferably, the filled paper has a weight between 10 and 120 gram per square meter, more preferably between 60 and 80 gram per square meter.

[0076] The filled sheet of paper can be a printed sheet of paper. The printed sheet of paper can provide a printed decor to a panel made with the sheet of paper.

[0077] The carrier can be an alpha cellulose sheet of paper, preferably having a weight between 15 and 60 gram per square meter. Such impregnated sheet of alpha cellulose paper can be used as an overlay to provide a wear resistant layer in a panel. Preferably, between 30 and 300 gram per square meter of dry weight of the acrylate coating composition is applied.

[0078] More preferably, more than 50 gram per square meter of dry weight of the acrylate coating composition is applied, even more preferably, more than 100 gram per square meter of dry weight acrylate lacquer is applied.

[0079] The acrylate coating layer may range between 30 and 300 grams per square meter, and preferably ranges between 100 and 300 grams per square meter. Meant is dry weight of the coating layer.

[0080] The coating layer can be partially cured (preferably to non-tacky state) by means of radiation energy, e.g. by means of UV-radiation, preferably including excimer radiation.

[0081] The step of partially curing the coating layer may comprise the steps of

[0082] - optionally applying a first UV-radiation step to the coating layer;

[0083] - applying a second UV-radiation step to the coating layer using an excimer-type monochromatic radiation lamp; and

[0084] - applying a third UV-radiation step to the coating layer.

[0085] Such method has shown to provide an optimum way to obtain non-tacky state of the surface of the partially cured acrylate coating layer combined with an appropriate level of curing in the depth of the acrylate coating layer which ensures that the carrier with the partially cured acrylate coating layer can be stored during some time, while still allowing for sufficient flow of the acrylate coating layer during a thermal pressing operation in which the acrylate coating layer is provided with a texture and in which the acrylate coating layer is thermally cured.

[0086] Preferably, the first UV-radiation step uses non-monochromatic UV-radiation. Such embodiment ensures that an appropriate level of curing is obtained over the depth of the coating layer. Preferably, the third UV-radiation step used non-monochromatic UV-radiation. Such embodiment ensures that an appropriate level of curing is obtained over the depth of the coating layer.

[0087] A preferred method according to the third aspect of the invention is characterized in that the step of applying the acrylate coating composition onto the carrier substrate comprises the steps of

[0088] - applying a first acrylate coating composition as in any embodiment of the first aspect or as in any embodiment of the second aspect of the invention onto the carrier substrate, and

[0089] - applying a second acrylate coating composition as in any embodiment of the first aspect or as in any embodiment of the second aspect of the invention onto the carrier substrate.

[0090] The composition of the first acrylate coating composition may be different from the composition of the second acrylate coating composition in order to optimize the process efficiency of a thermal pressing operation and / or of the final properties of the cured, textured acrylate coating layer.

[0091] It is preferred to apply a radiation curing step after applying the first acrylate coating composition and before applying the second acrylate coating composition. Such embodiment facilitates the partial curing of the combined acrylate coating layer (which comprising the first acrylate coating composition and on top of it the second acrylate coating composition). Such embodiment also facilitates the provision to the acrylate coating layer of a texture in a thermal pressing step.

[0092] The first acrylate coating composition preferably comprises abrasion resistant particles

[0093] - e.g. aluminum oxide particles, nanosilica particles, diamond particles, or siliconcarbide particles - having S50 particle size between 40 and 90 micrometer.

[0094] Even if the first acrylate coating composition is covered by a second acrylate coating composition, the presence of the abrasion resistance particles is beneficial to increase the wear resistance of the acrylate coating layer. The second acrylate coating composition preferably comprises abrasion resistant particles - e.g. e.g. aluminum oxide particles, nanosilica particles, diamond particles, or siliconcarbide particles — having S50 particle size between 5 - 30 micrometer.

[0095] As these fine particles are provided on the surface of the acrylate coating layer, they are beneficial to increase the scratch resistance of the acrylate coating layer.

[0096] The fourth aspect of the invention is a partially cured coated product, wherein the partially cured coated product comprises a carrier substrate - preferably a resin impregnated sheet of (more preferably printed) paper-; and a partially cured acrylate coating layer obtained from an acrylate coating composition as in any embodiment of the first aspect or as in any embodiment of the second aspect of the invention; and / or wherein the partially cured coated product is obtained in a method according to any embodiment of the third aspect of the invention.

[0097] The fifth aspect of the invention is a method of manufacturing a coated product comprising a cured acrylate coating layer. The method of the fifth aspect of the invention comprises the steps of

[0098] - providing a partially cured coated product as in any embodiment of the fourth aspect of the invention; and

[0099] - performing a thermal pressing operation onto the partially cured coated product, thereby providing the acrylate coating layer with a textured structure and curing the acrylate coating layer; and

[0100] - optionally laminating the partially cured coated product onto a carrier in the thermal pressing operation.

[0101] Preferably, use is made of a textured press element in the thermal pressing operation, wherein the textured structure of the acrylate coating layer is obtained by copying the texture of the textured press element. The thermal pressing operation can be performed in a continuous press or in a discontinuous press. Examples of press equipment that can be used include a single daylight press, a multiple daylight press and a double belt press.

[0102] As used for the acrylate coating composition of the different aspects of the invention, the molar mass of a compound is the calculated molar mass. The calculated molar mass is obtained by adding the atomic masses of all atoms present in the structural formula of a compound. When the exact structural formula of a compound is not known, the molar mass of the compound is the number average molecular weight determined using Triple Detection Size Exclusion Chromatography using tetra hydrofuran THF as eluent.

[0103] In the context of this document, the acrylate functionality of a compound is the number of acrylate groups per molecule of the compound. The average acrylate functionality of a compound comprising different types of molecules not necessarily having the same acrylate functionality is determined as the molar based weighed average of the acrylate functionality of the different molecules.

[0104] With unsaturated polyester resin is meant a polyester resin comprising carbon-carbon double bonds and which does not comprise acrylate reactive groups.

[0105] Photo-initiators that may be used in the different aspects of the invention may be selected from phosphine oxide type photo-initiators, hydroxy ketone type photo-initiators, hydroxy acetophenone type photo-initiators, free radical type 2 photo-initiators or polymeric photo-initiators (of type 1 or of type 2).

[0106] The use of phosphine oxide type photo-initiators is preferred as they are photo bleaching and therefore contribute to provide a transparent, colorless acrylate coating layer after the thermal curing of the acrylate coating layer.

[0107] Examples of phosphine type photo-initiators that may be used in the different aspects of the invention include ethyl (2,4,6-trimethyl benzoyl) phenyl phosphinate (CAS No. 84434-11-7) and bis (2,4,6-trimethylbenzoyl) phenylphospine oxide (BAPO, CAS No. 162881-26-7).

[0108] An example of a hydroxy ketone photo-initiator that can be used in the different aspect of the invention is difunctional alpha hydroxy ketone (CAS No. 71868-15-0).

[0109] Examples of hydroxy acetophenone photo-initiators that can be used in the invention include 2 -hydroxy -2 -methyl- 1 -phenylpropanone (CAS No. 7473-98-5) and 1- hydroxycyclohexyl-phenyl ketone.

[0110] Free radical type 2 photo-initiators have the benefits that they are not very sensitive to oxygen inhibition and that they are low in yellowing.

[0111] An example of free radical type 2 photo-initiators that can be used in the invention is benzoylformate ester, e.g. methylbenzoylformate.

[0112] Polymeric photo-initiators that may be used have molar mass higher than 500 g / mol, and preferably higher than 600 g / mol. Such photo-initiators are favored as they will not migrate to the surface of the acrylate coating layer.

[0113] Examples of polymeric photo-initiators that may be used in the invention are polymeric benzophenone derivatives.

[0114] A combination of two or even more than two photo-initiators is preferred. Such embodiments combine appropriate partial curing at the surface and over the depth of the partially cured acrylate coating layer.

[0115] Examples of thermo-initiators that can be used in the different aspect of the invention include:

[0116] - tert-butylperoxy 2-ethylhexyl carbonate (TBEC), having a 60 seconds half-time temperature of 166 °C. - tert.butylperoxyneodecanoate (TBPND), having a 60 seconds half-time temperature of 100 °C.

[0117] - tert-butyl 3,5,5-trimethylperoxyhexanoaat (TBPIN), having a 60 seconds halftime temperature of 160 °C.

[0118] 2-5-dimethyl-2-5-di-tert-butylperoxy-hexane, having a 60 seconds half-time temperature of 177 °C.

[0119] - tert-amyl peroxy 2-ethylhexyl carbonate (TAEC), having a 60 seconds half-time temperature of 155 °C. l,l-di(t-amylperoxy)-cyclohexane (DTAC), having a 60 seconds half-time temperature of 152 °C.

[0120] 2,5 dimethyl2,5di(tertbutylperoxy)hexyne3, having a 60 seconds half-time temperature of 194 °C.

[0121] With the intention of better showing the characteristics of the invention, hereafter, as an example without any limitative character, several preferred embodiments are described, with reference to the accompanying drawings, wherein: figure 1 illustrates an embodiment of a method of applying a coating layer onto a carrier substrate according to the third aspect of the invention; figure 2 illustrates an embodiment of a method of applying a coating layer onto a carrier substrate according to the third aspect of the invention; figure 3 shows an embodiment of method according to the fifth aspect the invention of manufacturing a coated product comprising a cured acrylate coating layer; figure 4 shows an example of a decorative panel as can be made in the method of the fifth aspect of the invention.

[0122] Figure 1 shows an example according to the third aspect of the invention. An impregnated printed sheet of paper 1 is unwound from a roll. The printed sheet of paper can be impregnated with a partially cured thermoset resin, e.g. with an aminoplast resin, with a polyurethane resin, with an acrylate resin, or with combinations thereof. Other resins can also be used. A coating station 6, e.g. a comma bar coater, is used to apply an acrylate coating composition 7 according to the first aspect or according to the second aspect of the invention onto the sheet of paper. The applied acrylate coating layer is partially cured, to non-tacky state, using radiation energy in a UV-radiation station 15. The impregnated printed sheet of paper covered at one side with the partially cured acrylate coating layer is wound on a roll 17.

[0123] The UV-radiation station can apply a first UV-radiation step to the coating layer, followed by a second UV-radiation step in which excimer-type monochromatic radiation lamps are used, and a third UV-radiation step.

[0124] Figure 2 illustrates an embodiment of a method of applying a coating layer onto a carrier substrate according to the third aspect of the invention. An impregnated printed sheet of paper 1 is unwound from a roll. The printed sheet of paper can be impregnated with a partially cured thermoset resin, e.g. with an aminoplast resin, with a polyurethane resin, with an acrylate resin, or with combinations thereof. Other resins can also be used. A first coating station 26, e.g. a comma bar coater, is used to apply a first acrylate coating composition 27 according to the first aspect or according to the second aspect of the invention onto the impregnated printed sheet of paper. The applied first acrylate coating layer can be partially cured using radiation energy in a first UV-radiation station 25.

[0125] A second coating station 36, e.g. a comma bar coater, is used to apply a second acrylate coating composition 37 according to the first aspect or according to the second aspect of the invention onto the impregnated printed sheet of paper provided with the first acrylate coating layer. The applied second acrylate coating layer can be partially cured using radiation energy in a second UV-radiation station 35 to non-tacky state. The impregnated printed sheet of paper covered at one side with the partially cured first and the second acrylate coating layers is wound on a roll 17.

[0126] The second UV-radiation station can apply a first UV-radiation step to the coating layer, followed by a second UV-radiation step in which excimer-type monochromatic radiation lamps are used, and a third UV-radiation step. Figure 3 shows an embodiment of method according to the fifth aspect the invention of manufacturing a coated product comprising a cured acrylate coating layer. Figure 3 shows an example of the production of a decorative panel, e.g. a decorative floor panel. The method involves a thermal pressing operation.

[0127] A stack comprising from top to bottom an impregnated printed sheet of paper 40 comprising a printed sheet of paper 41 impregnated with an impregnation compound and comprising a partially cured acrylate coating layer 43, a board 46 and optionally a balancing layer 47 (e.g. a sheet of paper impregnated with a thermoset resin, e.g. impregnated with a partially cured acrylate impregnation compound) is positioned in a single daylight press 50 having a structured press element 51.

[0128] The partially cured acrylate coating layer 43 is obtained from one or more acrylate coating compositions as in the first aspect of in the second aspect of the invention. The impregnated printed sheet of paper 40 comprising a printed sheet of paper 41 impregnated with an impregnation compound and comprising a partially cured acrylate coating layer 43 can have been produced in a method as shown in figure 1 or in figure 2.

[0129] The single daylight press 50 is closed, applying increased temperature - e.g. between 180 and 210 °C - and pressure - e.g. 5 - 100 kg / cm2- e.g. during 12 - 30 seconds. The use of the structured press element 51 results in a textured, cured surface of the decorative panel made in the thermal pressing operation. At the same time, the impregnated sheet of paper 40 is laminated to the board 46. The optional balancing layer 47 is also laminated to the board 16 in the thermal pressing operation.

[0130] The board 46 can be a wood-based board (e.g. a wood fiber board or a wood particle board) or a mineral board (e.g. an magnesium oxide based board). Other types of boards can also be used in the invention.

[0131] The board 46 of figure 3 can be replaced by a stack of impregnated sheets of paper that will provide a carrier in the similar way as the board 46 shown in figure 3. Figure 4 shows an example of a decorative panel 80 that can be made in the method of the fifth aspect of the invention. The decorative panel can be made in the thermal pressing operation shown in figure 3. The decorative panel comprises a board 46, optionally a balancing layer 47 at the bottom of the board, and a decorative top layer 44. The decorative top layer is provided by an impregnated sheet of paper 41 comprising a printed sheet of paper 41 having been impregnated with an impregnation compound and comprising an embossed acrylate coating layer. The decorative top layer can be obtained in the thermal pressing operation in which the coating layer is textured and cured.

[0132] As non-limiting examples only, a number of examples of acrylate coating compositions according to the invention are given.

[0133] A first example of an acrylate coating composition according to the invention comprises: first group of reactants o 35 parts by weight of an aliphatic urethane acrylate oligomer having acrylate functionality equal to four; second group of reactants o 10 parts by weight of a polyester acrylate oligomer having acrylate functionality three; o 10 parts by weight of an unsaturated polyester resin;

[0134] - third group of reactants: o 20 parts by weight of glyceryl propoxy triacrylate (GPTA), a trifunctional acrylate reactive diluent; o 5 parts by weight of dipropylene glycol diacrylate (DPGDA), a difunctional acrylate reactive diluent; o 20 parts by weight of tripropyleneglycol diacrylate (TPGDA), a difunctional acrylate reactive diluent; thermo-initiator: o 0.2 parts by weight of tert-butyl 3,5,5-trimethylperoxyhexanoaat (TBPIN);

[0135] 0.2 parts by weight of photo-initiator;

[0136] 0.2 parts by weight of bismuth neodecanoate (a bismuth soap); optionally, 3 parts by weight of a silicone hexa acrylate as wetting agent. optionally, 7 parts by weight of a matting agent can be added, e.g. amorphous silica.

[0137] A second example of an acrylate coating composition according to the invention comprises: first group of reactants o 35 parts by weight of an aliphatic urethane acrylate oligomer having acrylate functionality equal to four; second group of reactants o 10 parts by weight of a polyester acrylate oligomer having acrylate functionality three; o 10 parts by weight of an unsaturated polyester resin;

[0138] - third group of reactants o 20 parts by weight of glyceryl propoxy triacrylate (GPTA), a trifunctional acrylate reactive diluent; o 5 parts by weight of dipropylene glycol diacrylate (DPGDA), a difunctional acrylate reactive diluent; o 15 parts by weight of tripropyleneglycol diacrylate (TPGDA), a difunctional acrylate reactive diluent; o 5 parts by weight of an ethoxylated trimethylolpropane triacrylate, a trifunctional acrylate reactive diluent; thermo-initiator: o 0.2 parts by weight of tert-butyl 3,5,5-trimethylperoxyhexanoaat (TBPIN);

[0139] 0.4 parts by weight of photo-initiator;

[0140] 0.4 parts by weight of bismuth neodecanoate (a bismuth soap); optionally, 2 parts by weight of a silicone hexa acrylate as wetting agent. optionally, 5 parts by weight of a matting agent can be added, e.g. amorphous silica.

[0141] A third example of an acrylate coating composition according to the invention comprises: first group of reactants o 30 parts by weight of an aliphatic urethane acrylate oligomer having acrylate functionality equal to four; o 10 parts by weight of an aliphatic urethane acrylate oligomer having acrylate functionality two; second group of reactants o 10 parts by weight of a polyester acrylate oligomer having acrylate functionality equal to three; o 10 parts by weight of an unsaturated polyester resin;

[0142] - third group of reactants o 20 parts by weight of glyceryl propoxy triacrylate (GPTA), a trifunctional acrylate reactive diluent; o 5 parts by weight of dipropylene glycol diacrylate (DPGDA), a difunctional acrylate reactive diluent; o 15 parts by weight of tripropyleneglycol diacrylate (TPGDA), a difunctional acrylate reactive diluent; thermo-initiator: o 0.2 parts by weight of tert-butyl 3,5,5-trimethylperoxyhexanoaat (TBPIN);

[0143] 0.2 parts by weight of photo-initiator;

[0144] 0.4 parts by weight of bismuth neodecanoate (a bismuth soap); optionally, 3 parts by weight of a silicone hexa acrylate as wetting agent. optionally, 5 parts by weight of a matting agent can be added, e.g. amorphous silica.

[0145] A fourth example of an acrylate coating composition according to the invention comprises: first group of reactants o 30 parts by weight of an aliphatic urethane acrylate oligomer having acrylate functionality equal to four; o 10 parts by weight of an aliphatic urethane acrylate having acrylate functionality two; second group of reactants o 10 parts by weight of a polyester acrylate oligomer having acrylate functionality equal to three; o 10 parts by weight of an unsaturated polyester resin;

[0146] - third group of reactants o 20 parts by weight of glyceryl propoxy triacrylate (GPTA), a trifunctional acrylate reactive diluent; o 5 parts by weight of dipropylene glycol diacrylate (DPGDA), a difunctional acrylate reactive diluent; o 15 parts by weight of tripropyleneglycol diacrylate (TPGDA), a difunctional acrylate reactive diluent; thermo-initiator: o 0.2 parts by weight of tert-butyl 3,5,5-trimethylperoxyhexanoaat (TBPIN); o 0.2 parts by weight of 2-5-Dimethyl-2-5-di-tert-butylperoxy-hexane o 0.2 parts by weight of tert-amyl peroxy 2-ethylhexyl carbonate (TAEC);

[0147] 0.3 parts by weight of photo-initiator;

[0148] 0.2 parts by weight of bismuth neodecanoate (a bismuth soap); optionally, 3 parts by weight of a silicone hexa acrylate as wetting agent. optionally, 5 parts by weight of a matting agent can be added, e.g. amorphous silica.

[0149] The acrylate coating compositions of the examples can optionally comprise abrasion resistance increasing particles, e.g. aluminum oxide particles.

[0150] The present invention is in no way limited to the embodiments described as an example and represented in the figures, on the contrary it can be realized in various forms and dimensions, without leaving the scope of the invention.

Claims

Claims1 Acrylate coating composition comprising - and preferably consisting of -- a first group of reactants consisting of one or more aliphatic urethane (meth)acrylate oligomers, wherein the aliphatic urethane (meth)acrylate oligomers have a molar mass higher than 750 g / mol, and preferably lower than 8000 g / mol;- a second group of reactants selected from one or more polyester (meth)acrylate oligomers having molar mass higher than 750 g / mol, from one or more unsaturated polyester resins having molar mass higher than 750 g / mol, or from combinations thereof;- a third group of reactants consisting of one or more acrylate reactive diluents having a molar mass lower than 750 g / mol;- at least one thermo-initiator;- at least one photo-initiator; and optionally additives, preferably non-reactive additives.2.- Acrylate coating composition as in claim 1, characterized in that the third group of reactants provides between 30 and 60 wt% of the combination of the first group of reactants, the second group of reactants and the third group of reactants.3.- Acrylate coating composition as in any of the preceding claims, characterized in that the first group of reactants provides between 50 and 80 wt% of the combination of the first group or reactants and the second group of reactants.4.- Acrylate coating composition as in any of the preceding claims, characterized in that the combination of the first group of reactants, the second group of reactants and the third group of reactants provides at least 80 wt% of the acrylate coating composition.5.- Acrylate coating composition as in any of the preceding claims, characterized in that the coating composition comprises one or more polyester (meth)acrylate oligomers having molar mass higher than 750 g / mol and preferably lower than 8000 g / mol, as well as one or more unsaturated polyester resins having molar mass higher than 750 g / mol.6.- Acrylate coating composition as in any of the preceding claims, characterized in that the average acrylate functionality of the one or more aliphatic urethane (meth)acrylate oligomers is between 1.5 and 4.5.7.- Acrylate coating composition as in any of the preceding claims, characterized in that the third group of reactants comprises less than 3 wt% - and preferably less than 1 wt%, more preferably less than 0.5 wt% - of methacrylate reactive diluents relative to the combination of the first group of reactants, the second group of reactants and the third group of reactants; more preferably the acrylate coating composition does not comprise methacrylate reactive diluents.8.- Acrylate coating composition as in any of the preceding claims, characterized in that the average acrylate functionality of the one or more acrylate reactive diluents is between 2 and 4.9.- Acrylate coating composition as in any of the preceding claims, characterized in that the third group of reactants comprises acrylate reactive diluents having acrylate functionality equal to 2 as well as acrylate reactive diluents having acrylate functionality equal to 3 or 4.10.- Acrylate coating composition as in any of the preceding claims, characterized in that the acrylate coating composition does not comprise acrylate reactive diluents having acrylate functionality equal to one.11.- Acrylate coating composition as in any of the preceding claims, characterized in that the at least one thermo-initiator provides less than 1.5 wt%, and preferably less than 1 wt%, and more preferably less than 0.5 wt% of the combination of the first group of reactants, the second group of reactants and the third group of reactants.12.- Acrylate coating composition as in any of the preceding claims, characterized in that the at least one photo-initiator provides less than 1.5 wt%, and preferably less than0.75 wt%, and preferably less than 0.35 wt%, and more preferably less than 0.2 wt%, of the combination of the first group of reactants, the second group of reactants and the third group of reactants.13.- Acrylate coating composition as in any of the preceding claims, characterized in that the first group of reactants and the second group of reactants do not comprise methacrylate oligomers.14.- Acrylate coating composition as in any of the preceding claims, characterized in that the second group of reactants comprises either one or more unsaturated polyester (meth)acrylate oligomers or one or more non-unsaturated polyester (meth)acrylate oligomers.15.- Acrylate coating composition as in any of the preceding claims, characterized in that the second group of reactants comprises one or more unsaturated polyester (meth)acrylate oligomers as well as one or more non-unsaturated polyester (meth)acrylate oligomers, preferably wherein the mass ratio of the one or more unsaturated polyester (meth)acrylate oligomers to the one or more non-unsaturated polyester (meth)acrylate oligomers is between 0.5 - 2.16.- Acrylate coating composition as in any of the preceding claims, characterized in that the second group of reactants comprises polyester (meth)acrylate oligomers having acrylate functionality at least 2.5; preferably all polyester (meth)acrylate oligomers in the acrylate coating composition have acrylate functionality at least 3.17.- Acrylate coating composition as in any of the preceding claims, characterized in that the acrylate coating composition comprises besides the first group of reactants, the second group of reactants and the third group of reactants and relative to the combined amount of reactive monomers, reactive oligomers and reactive resins, less than 4 wt% of reactive components.18.- Acrylate coating composition as in any of the preceding claims, characterized in that the one or more thermo-initiators comprise a first thermo-initiator and a second thermo-initiator, wherein the 60 seconds half-life of the second thermo-initiator is at least 8°C higher than the 60 seconds half-life of the first thermo-initiator.19.- Acrylate coating composition as in any of the preceding claims, characterized in that the acrylate coating composition comprises at least one additive, wherein the at least one additive comprises a metal soap, more preferably selected from one or more than one of sodium soap, bismuth soap and zinc soap.20.- Acrylate coating composition as in any of the preceding claims, characterized in that the additives comprise abrasion resistant particles, e.g. aluminum oxide particles, preferably in an amount between 0.5 and 15 wt% of the acrylate coating composition.21.- Acrylate coating composition as in any of the preceding claims, characterized in that the additives comprise a matting agent, preferably wherein the matting agent provides between 2 and 14 wt% - and more preferably between 3 and 10 wt% - of the acrylate coating composition.22.- Acrylate coating composition as in claim 21, characterized in that the matting agent is an amorphous silica, preferably having average particle size between 3 and 20 micrometer.23.- Acrylate coating composition comprising- one or more (meth)acrylate oligomers, wherein the aliphatic urethane (meth)acrylate oligomers have a molar mass higher than 750 g / mol, and preferably lower than 8000 g / mol;- one or more acrylate reactive diluents having a molar mass lower than 750 g / mol, preferably wherein the acrylate reactive diluents have an average acrylate functionality of at least 2;- at least one thermo-initiator;- optionally at least one photo-initiator;- a matting agent, preferably wherein the matting agent provides between 2 and 14 wt% of the acrylate coating composition; optionally additives.24.- Acrylate coating composition as in claim 23, characterized in that the matting agent is an amorphous silica, preferably having average particle size between 3 and 20 micrometer.25.- Acrylate coating composition as in any of the preceding claims 1 - 24, characterized in that the acrylate coating composition comprises a crosslinker, preferably selected from an isocyanate, an aziridine or a carbo-diimide, or combinations thereof.26.- Method of applying a coating layer onto a carrier substrate, wherein the method comprises the steps of- providing a carrier substrate, preferably a resin impregnated sheet of paper;- applying the acrylate coating composition of any of the preceding claims 1 - 25 onto the carrier substrate, thereby obtaining a coating layer on the carrier substrate; and- partially curing the coating layer, preferably to non-tacky state.27.- Method as in claim 26, characterized in that the coating layer ranges between 30 and 300 grams per square meter, and preferably ranges between 100 and 300 grams per square meter.28.- Method as in any of the preceding claims 26 - 27, characterized in that the coating layer is partially cured by means of radiation energy, e.g. by means of UV-radiation, preferably including excimer radiation.29.- Method as in any of the preceding claims 26 - 28, characterized in that the step of partially curing the coating layer, comprises the steps of- optionally applying a first UV-radiation step to the coating layer;- applying a second UV-radiation step to the coating layer using an excimer-typemonochromatic radiation lamp; and- applying a third UV-radiation step to the coating layer.30.- Method as in any of the preceding claims 26 - 29, characterized in that the step of applying the acrylate coating composition as in any of the preceding claims 1 - 25 onto the carrier substrate comprises the steps of- applying a first acrylate coating composition as in any of the preceding claims 1 - 25 onto the carrier substrate, and- applying a second acrylate coating composition as in any of the preceding claims 1 - 25 onto the carrier substrate.31.- Partially cured coated product, wherein the partially cured coated product comprises a carrier substrate, preferably a resin impregnated sheet of paper; and a partially cured acrylate coating layer obtained from an acrylate coating composition as in any of the preceding claims 1 - 25, and / or wherein the partially cured coated product is obtained in a method according to any of the preceding claims 26 - 30.32.- Method of manufacturing a coated product comprising a cured acrylate coating layer, wherein the method comprises the steps of- providing a partially cured coated product as in claim 31; and- performing a thermal pressing operation onto the partially cured coated product, thereby providing the acrylate coating layer with a textured structure and curing the acrylate coating layer; and- optionally laminating the partially cured coated product onto a carrier in the thermal pressing operation.

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