METHOD FOR PRODUCING A COMPOSITE MATERIAL FREE OF MELAMINE FORMALDEHYDE RESIN

Description

[0001] The present invention relates to a method for producing a composite material free of melamine-formaldehyde resin and a melamine-free composite material produced by this method.

[0002] Melamine resin surfaces have been used in a wide variety of applications for decades. These surfaces are frequently used where high demands are placed on easy cleaning and disinfection. A particular advantage is that melamine surfaces inherently do not provide a good growth substrate for bacteria. Further benefits include their very high chemical and mechanical resistance. The melamine layer also acts as an effective barrier against outgassing from the core boards. These advantages of melamine resin surfaces are particularly utilized in laminate flooring and furniture surfaces.

[0003] However, the potential negative environmental properties of melamine are currently being discussed. These include its persistence (poor biodegradability) and its mobility after release. Although melamine is only detectable in melamine resin surfaces in harmless trace amounts, this discussion is naturally causing uncertainty in the market.

[0004] A further problem is that alternative materials are either not available in the required quantities, are not as high-performing in terms of their properties, and / or cannot be processed on existing production lines (e.g., short-cycle presses, laminate presses, etc.). The same applies to the customers of the coated panels, who naturally also take into account the good mechanical properties during transport through processing lines, etc.

[0005] The idea of ​​covering the finished melamine resin surface with a thin protective layer after production is unfortunately not practical, as this protective layer could be quickly worn away by abrasion from foot traffic (laminate flooring) or disinfection (furniture surfaces). Furthermore, this would not solve the problem of melamine dust generated during processing.

[0006] Besides melamine resin, a number of other resins are known to be used for impregnating papers for decorative applications. However, these synthetic resins have disadvantages that make their use as the sole resin impossible.

[0007] Urea-formaldehyde resins are used, for example, individually or in mixtures with melamine-formaldehyde resins for core impregnation. However, they have the disadvantage that, when impregnated materials are processed in short-cycle presses, these resins do not flow into a film. Furthermore, urea-formaldehyde resins are susceptible to hydrolysis and are not chemically stable.

[0008] Another synthetic resin used for various applications is phenol-formaldehyde resin. This resin, which has a light to medium brown color, is used for impregnating the core layers of laminates or for underlay sheets. However, due to its inherent color, it cannot be used for impregnating the surfaces of decorative papers. Furthermore, the resin deepens in color when exposed to sunlight. Direct contact of phenol impregnating agents with food must also be avoided.

[0009] Another resin system that could be used is acrylate resin. However, when used alone in paper production, this results in a brittle impregnation that cannot be processed in a short-cycle press.

[0010] For surfaces not subjected to high mechanical or chemical stress, so-called finish foils are an alternative. These are decorative products with a core impregnation of urea-formaldehyde resin and acrylate resin, coated on the top surface with a lacquer (UV or ESH lacquer). These foils are laminated onto wood-based substrates on laminating lines. Compared to melamine surfaces, they have significantly inferior properties, making them unsuitable for applications with moderate or heavy-duty stress. They cannot be processed on short-cycle presses.

[0011] EP 3878648A1 relates to a composite material for use in a floor covering consisting of a substrate material (wood-based panel, paper layer) with a resinous layer and a TPU film arranged on the resinous layer.

[0012] The invention is therefore based on the technical objective of overcoming the disadvantages resulting from the reclassification. The product should be melamine-free through the use of alternative resins or films. To this end, a composite material, e.g., in the form of an impregnating agent, is to be developed that, after processing on short-cycle and continuous presses, yields products with a property profile nearly identical to that of a melamine surface. The impregnating agent should be producible on existing impregnation channels. Further processing should also remain possible on short-cycle and continuous presses without any technological or technical modifications. The product's cost should not change significantly.

[0013] This problem is solved according to the invention by a method having the features of claim 1 and a composite material produced therein according to claim 13.

[0014] Accordingly, according to a first aspect of claim 1, a method for producing a composite material free of melamine-formaldehyde resin is provided, comprising at least one paper layer as a substrate, at least one polymer layer of a thermoplastic polymer provided on the top side of the paper layer, and at least one resin-containing layer provided on the bottom side of the paper layer, wherein the method comprises the following steps: Providing at least one carrier material, applying at least one layer of a urea-formaldehyde resin to the top of the paper layer for impregnation of the paper layer, after impregnation applying at least one layer of the thermoplastic polymer, in particular, thermoplastic polyurethane, to the top of the paper layer, wherein the thermoplastic polymer is applied as a dispersion with a solids content of 20-60 wt%; applying at least one resinous layer to the underside of the paper layer, and drying and pressing the layer structure.

[0015] A method for producing a composite material for use in floor laminates or furniture components is thus provided, in which the use of melamine-formaldehyde resin can be completely dispensed with. In particular, the surface layers provided on the substrate material do not contain any melamine-formaldehyde resin. Surprisingly, the composite materials produced with the present method meet the requirements necessary for floor coverings, as shown in the exemplary embodiments.

[0016] The order in which the thermoplastic polymer layer is applied to the top of the substrate and the resin layer to the underside can be flexible and variable. This means that the thermoplastic polymer can be applied to the top of the substrate first, followed by the resin layer to the underside. Alternatively, the resin layer can be applied to the underside first, followed by the thermoplastic polymer to the top. It is also possible to apply the thermoplastic polymer to the top and the resin layer to the underside simultaneously. The specific order depends on the production line.

[0017] In another non-inventive variant, it would also be possible not to use a thermoplastic polymer for coating the surface, but instead to use a lacquer layer, whereby this lacquer layer is applied to the top or surface of the substrate material after pressing the layer structure.

[0018] According to a non-inventive aspect, a method for producing a composite material free of melamine-formaldehyde resin is provided, comprising at least one substrate material, at least one lacquer layer provided on the top side of the substrate material, and at least one resinous layer provided on the bottom side of the substrate material, wherein the method comprises the following steps: Providing at least one substrate material, applying at least one layer of a urea-formaldehyde resin to the substrate material, applying at least one resinous layer to the underside of the substrate material, and drying and pressing the layer structure; applying at least one layer of a lacquer to the top side of the pressed layer structure. Paper layer as carrier material

[0019] According to the invention, at least one carrier material is a layer of paper, preferably a layer of decorative paper.

[0020] According to the first aspect, the present procedure therefore comprises the following steps: Providing at least one paper layer, applying at least one layer of a urea-formaldehyde resin to the paper layer for impregnation of the paper layer, applying at least one layer of a thermoplastic polymer, in particular thermoplastic polyurethane, to the top of the impregnated paper layer, applying at least one resin-containing layer as an adhesive layer to the underside of the impregnated paper layer, and drying and pressing the layer structure.

[0021] The paper layers used here, in particular decorative paper layers, have a paper weight between 60 and 120 g / m², preferably 80 g / m².

[0022] Decorative papers are specialty papers used for surface finishing of wood-based materials, offering a wide variety of designs. In addition to typical prints of various wood textures, more elaborate prints of geometric shapes or artistic, decorative designs are available. There are virtually no limitations on the choice of motif. To ensure optimal printability, the paper used must be smooth and dimensionally stable, and also suitable for penetrating any necessary resin impregnation.

[0023] As stated, a urea-formaldehyde resin is first applied to the substrate. The paper layer is partially or completely impregnated with the resin, which penetrates the paper layer. In this context, "impregnation" refers to the complete or partial saturation of the paper layer with the resin. The urea resin used here is employed for the so-called core impregnation of the paper.

[0024] In one variant, the liquid application rate of the urea-formaldehyde resin is between 100 and 250 g / m², preferably between 130 and 200 g / m², and particularly preferably between 150 and 180 g / m², such as 160 g / m². The solid application rate of the urea-formaldehyde resin is between 50 and 125 g / m², preferably between 65 and 100 g / m², and particularly preferably between 75 and 90 g / m², such as 80 g / m².

[0025] The usual additives, such as hardeners, wetting agents (surfactants or mixtures thereof), release agents and / or other components, are added to the urea-formaldehyde resin used for core impregnation.

[0026] In the production of the impregnating agents, the urea resin is applied in an impregnation tank. After immersion, the resin is scraped off to a defined thickness using doctor blades or squeeze rollers. The impregnating agent is then intermediate-dried in a hot air dryer, for example, to a residual moisture content of 20% by weight.

[0027] A corresponding impregnation plant includes: Optional paper unwinding and changing device, an impregnation station for pre-impregnation (core impregnation) of at least one paper layer with a urea-formaldehyde resin, and a first drying station.

[0028] Specifically, the impregnation plant includes impregnation tanks or impregnation immersion baths (as impregnation stations), possibly a breathing zone, a doctor blade system / pair of squeeze rollers for removing excess resin, at least one dryer (e.g. a floating dryer), optionally a grid system, optionally a powder spreader and an optional second dryer, at least one cooling device (e.g. a cooling roller system).

[0029] Following core impregnation, the thermoplastic polymer, in particular thermoplastic polyurethane, is applied to the paper layer in a subsequent step. In this case, a dispersion of a thermoplastic polymer with a solids content between 20 and 60 wt%, preferably between 30 and 50 wt%, and particularly 40 wt%, is used. The application rate of the thermoplastic polymer is between 50 and 150 g / m² < fl, preferably between 70 and 130 g / m² < fl, and particularly preferably between 90 and 110 g / m² < fl, such as 100 g / m² < fl. The application rate of the thermoplastic polymer is approximately 30–50 wt% based on the paper weight.

[0030] As already indicated, thermoplastic polyurethane is preferably used as the thermoplastic polymer, especially as a surface layer.

[0031] Thermoplastic polyurethane (TPU) belongs to a class of polyurethanes - plastics with many properties, such as high abrasion resistance, low temperature performance, high shear strength, high elasticity, transparency, and oil and grease resistance.

[0032] TPU is a block copolymer consisting of alternating sequences of hard and soft segments or domains formed by the reaction of (1) diisocyanates with short-chain diols and (2) diisocyanates with long-chain diols. By varying the ratio, structure, and / or molecular weight of the reactants, a vast variety of different TPUs can be produced. This allows the polymer structure to be finely tuned to the desired end properties of the material.

[0033] TPU is used as a dispersion (TPU beads in water) for coating. During the drying process of the impregnating agent, the TPU reacts and is incorporated into the polymer matrix, particularly the impregnating agent, during compression molding. It is advantageous if the glass transition temperatures of the TPU are as low as possible to maintain its elastic properties.

[0034] As mentioned above, a resinous layer is applied to the underside of the paper layer. In the case of the paper layer, this resinous layer acts as an adhesive layer or bonding layer.

[0035] A phenol-formaldehyde resin (PF resin), phenol-lignin-formaldehyde resin (PLF resin) or a polyurethane (PU) can be used as the adhesive layer.

[0036] The phenol-formaldehyde resin (PF resin) or phenol-lignin-formaldehyde resin (PLF resin) can be applied to the underside of the paper layer as a liquid coating or as a powder coating.

[0037] In the case of liquid application, PF resin or PLF resin with a solids content between 30 and 80 wt%, preferably between 40 and 60 wt%, and particularly 50 wt%, is used. The application rate of the PF resin or PLF resin is between 30 and 100 g / m² < fl, preferably between 40 and 80 g / m² < fl, and particularly preferably between 50 and 70 g / m² < fl, such as 60 g / m² < fl. The application rate of the PF resin or PLF resin is approximately 20–30 wt% based on the paper weight.

[0038] In the case of powder application, PF resin or PLF resin is applied in an amount between 10 and 50 g / m², preferably between 20 and 40 g / m², and particularly preferably between 25 and 35 g / m², such as 30 g / m². The powdered resin is applied to the substrate by electrostatic charging and optionally melted. The application can also be carried out by powder coating using the tribological process. In this process, the powder to be applied is charged by friction.

[0039] "Pre-melting" within the meaning of this application means that the resin layer is not yet fully polymerized, but rather the polymerization is stopped at an intermediate stage in which further cross-linking or polymerization is still possible at a later processing stage. Pre-melting of the applied layer of powdered resin can be carried out using an IR emitter, microwave systems, or similar devices. The use of IR emitters is particularly preferred.

[0040] In a further embodiment, polyurethane is applied as an alternative to phenol-formaldehyde resin as at least one adhesive layer or coating to the underside of the substrate. The amount of polyurethane adhesive coating is 10-40% by weight, preferably 20-30% by weight, based on the paper weight.

[0041] After all layers have been applied to the paper layer, the resulting impregnating agent is dried to a defined residual moisture content, e.g. 5-10 wt%, preferably 6 wt%.

[0042] A paper layer coated and impregnated in this way, e.g., a decorative paper layer, can be pressed onto a substrate, e.g., a wood-based panel such as MDF or HDF or particleboard, in a short-cycle press or a continuous press. In particular, the impregnating agent can be cut to suitable formats and pressed onto wood-based panels.

[0043] After compression molding, in one embodiment the (upper) layer of thermoplastic polymer can be coated with a lacquer layer to increase abrasion resistance. For this purpose, a lacquer system consisting of at least one lacquer layer and at least one topcoat, preferably a UV or ESH lacquer, is applied as a cover layer to improve scratch resistance. The topcoat may contain nanoparticles, e.g., made of silica. No solvent-based lacquers are used.

[0044] For the coating layer and the topcoat, radiation-curable, acrylate-containing coatings are primarily used. Typically, the radiation-curable coatings used contain (meth)acrylates, such as polyester (meth)acrylate, polyether (meth)acrylate, epoxy (meth)acrylate, or urethane (meth)acrylate. It is also conceivable that the acrylate used, or the acrylate-containing coating, consists of substituted or unsubstituted monomers, oligomers, and / or polymers, particularly in the form of acrylic acid, acrylate ether, and / or acrylic acid ester monomers, oligomers, or polymers. Of importance for the present process is the presence, by definition, of a double bond or unsaturated group in the acrylate molecule. The polyacrylates can also be functionalized. Suitable functional groups include hydroxy, amino, epoxy, and / or carboxyl groups. The aforementioned acrylates enable crosslinking or curing in the presence of UV or other radiation.Electron beams (ESH).

[0045] The coating layer is applied in an amount between 50 and 100 g / m², preferably between 60 and 80 g / m², while the topcoat is applied in an amount between 10 and 30 g / m², preferably 30 g / m². The coating system can consist of at least one ESH coating layer, which is gelled after application using an ESH lamp, and at least one topcoat, which is partially cured after application using an excimer lamp. The entire coating system is then fully cured using an ESH lamp.

[0046] In one embodiment, the present method thus comprises the following steps: Providing at least one paper layer as a substrate, applying at least one layer of a urea-formaldehyde resin to the paper layer for impregnation, applying at least one layer of a thermoplastic polyurethane to the top of the impregnated paper layer, applying at least one adhesive layer to the bottom of the impregnated paper layer, and drying and pressing the layer structure, optionally applying at least one varnish to the at least one layer of thermoplastic polyurethane.

[0047] In a further embodiment, the present method thus comprises the following steps: Providing at least one paper layer as a substrate, applying at least one layer of a urea-formaldehyde resin to the paper layer for impregnation, applying at least one layer of a thermoplastic polyurethane to the top of the impregnated paper layer, applying at least one powdered layer of a PF resin or PLF resin as an adhesive layer to the underside of the impregnated paper layer and melting the powdered layer, drying and pressing the layer structure, and optionally applying at least one varnish to the at least one layer of thermoplastic polyurethane.

[0048] In another embodiment, the present method thus comprises the following steps: Providing at least one paper layer as a substrate, applying at least one layer of a urea-formaldehyde resin to the paper layer for impregnation, applying at least one layer of a thermoplastic polyurethane to the top of the impregnated paper layer, applying at least one liquid layer of a PF resin or PLF resin as an adhesive layer to the underside of the impregnated paper layer, drying and pressing the layer structure, optionally applying at least one varnish to the at least one layer of thermoplastic polyurethane.

[0049] In yet another embodiment, the present method thus comprises the following steps: Providing at least one paper layer as a substrate, applying at least one layer of a urea-formaldehyde resin to the paper layer for impregnation, applying at least one layer of a thermoplastic polyurethane to the top of the impregnated paper layer, applying at least one liquid layer of a polyurethane as an adhesive layer to the underside of the impregnated paper layer, drying and pressing the layer structure, optionally applying at least one UV varnish to the at least one layer of thermoplastic polyurethane.

[0050] Accordingly, the present method, according to the first aspect, enables in one variant the provision of a first melamine-free composite material with the following layer structure (from bottom to top): Optional adhesive layer, layer of a phenol-formaldehyde resin or phenol-lignin-formaldehyde resin, paper layer impregnated with urea-formaldehyde resin - TPU layer - optional varnish.

[0051] In another variant, the present process enables the provision of a melamine-free composite material with the following layer structure (from bottom to top): wood-based panel - adhesive layer, layer of a phenol-formaldehyde resin or phenol-lignin-formaldehyde resin - paper layer impregnated with urea-formaldehyde resin - TPU layer - optional lacquer.

[0052] As described above, according to the invention, the use of a thermoplastic polymer for coating the surface can also be dispensed with, and instead a lacquer structure can be applied to the layer structure after pressing.

[0053] According to this non-inventive aspect, the present method may comprise the following steps: Providing at least one layer of paper, applying at least one layer of a urea-formaldehyde resin to the paper layer for impregnation of the paper layer, applying at least one resinous layer as an adhesive layer to the underside of the impregnated paper layer, drying and pressing the layer structure, and applying at least one layer of a varnish to the top side of the pressed layer structure.

[0054] In a further non-inventive embodiment, the present method thus comprises the following steps: Providing at least one paper layer as a substrate, applying at least one layer of a urea-formaldehyde resin to the paper layer for impregnation of the paper layer, applying at least one powdered layer of a PF resin or PLF resin as an adhesive layer to the underside of the impregnated paper layer and melting the powdered layer, drying and pressing the layer structure, and applying at least one layer of a varnish to the top side of the pressed layer structure.

[0055] In another non-inventive embodiment, the present method thus comprises the following steps: Providing at least one paper layer as substrate material, applying at least one layer of a urea-formaldehyde resin to the paper layer for impregnation of the paper layer, applying at least one liquid layer of a PF resin or PLF resin as an adhesive layer to the underside of the impregnated paper layer, drying and pressing the layer structure, and applying at least one layer of a varnish to the top side of the pressed layer structure.

[0056] In yet another non-inventive embodiment, the present method thus comprises the following steps: Providing at least one paper layer as a substrate, applying at least one layer of a urea-formaldehyde resin to the paper layer for impregnation, applying at least one liquid layer of polyurethane as an adhesive layer to the underside of the impregnated paper layer, drying and pressing the layered structure. Applying at least one layer of varnish to the top side of the pressed layered structure.

[0057] The above-mentioned information regarding the composition and application quantities of resin and varnish also applies to the latter embodiments of the non-inventive aspect of the process.

[0058] Accordingly, the present method, according to the non-inventive second aspect, enables in one variant the provision of a melamine-free composite material with the following layer structure (from bottom to top): adhesive layer, preferably a layer of a PF resin or PLF resin or polyurethane paper layer impregnated with urea-formaldehyde resin lacquer structure.

[0059] In another variant, the present method, according to the non-inventive aspect, enables the provision of a melamine-free composite material with the following layer structure (from bottom to top): wood-based panel - adhesive layer, preferably a layer of a PF resin or PLF resin or polyurethane - paper layer impregnated with urea-formaldehyde resin - lacquer structure. Wood-based panel as substrate material

[0060] In another embodiment of the present method, a wood-based panel, preferably a medium-density fiberboard (MDF), a high-density fiberboard (HDF), a plywood panel, a particleboard, or a wood-plastic composite (WPC) panel, is used as the substrate material. Particularly preferred wood-based panels are fiberboards with urea-formaldehyde adhesive as a binder, such as an HDF panel with urea-formaldehyde adhesive.

[0061] The present procedure according to the first aspect can therefore also include the following steps (non-inventive): Providing at least one wood-based panel as a substrate material, applying at least one layer of a urea-formaldehyde resin to the top surface of the wood-based panel, applying at least one layer of at least one thermoplastic elastomer; in particular a thermoplastic polyurethane; applying at least one backing layer, preferably in the form of a layer of a PF resin or PLF resin, to the underside of the wood-based panel, and drying and pressing the layer structure.

[0062] In a preferred non-inventive embodiment, the present method comprises the following steps: Providing at least one wood-based panel as a substrate material, applying at least one layer of a urea-formaldehyde resin to the top surface of the wood-based panel, applying at least one color primer layer; applying at least one first primer layer, applying a printed decoration; applying at least one second primer layer, applying at least one layer of at least one thermoplastic elastomer; applying at least one backing layer, preferably in the form of a layer of PF resin or PLF resin, to the underside of the wood-based panel as a backing layer, and drying and pressing the layer structure.

[0063] Urea-formaldehyde resin is therefore used as a resin primer or roller primer. The application rate of the resin primer can be between 10 and 40 g resin fl / m², preferably 20 to 30 g resin fl / m², e.g., 25 g resin fl / m². The solids content of the resin primer can be between 20 and 50 wt%, preferably between 30 and 40 wt%, and particularly preferably 35 wt%.

[0064] The usual additives, such as hardeners, wetting agents (surfactants or mixtures thereof), release agents and / or other components, are added to the urea-formaldehyde resin used for priming.

[0065] A preferred color primer consists of casein or soy protein as a binder and inorganic pigments, particularly inorganic color pigments. White pigments such as titanium dioxide or other color pigments, such as calcium carbonate, barium sulfate, or barium carbonate, can be used in the primer layer. In addition to the color pigments and the casein or soy protein, the primer may also contain water as a solvent. It is also preferred that the applied pigmented primer layer consists of at least one, preferably at least two, and particularly preferably at least four, or up to seven successively applied layers or coats, whereby the application rate between layers or coats may be the same or different. The application rate of the color primer is 5-10 g of primer fl oz / m² per layer. An intermediate drying step is preferably performed after each application.

[0066] The amount of liquid first primer applied to the color base is between 5 and 30 g / m², preferably between 10 and 20 g / m², and particularly preferably between 10 and 15 g / m². Isocyanate-based compounds are preferred as primers, with non-aromatic, aliphatic isocyanates, such as hexamethylene diisocyanate, isophorone diisocyanate, or prepolymers containing these isocyanates being particularly preferred.

[0067] After a drying step, the decorative layer is applied. This is preferably done using direct printing. In the case of direct printing, a water-based, pigmented ink is applied using gravure or digital printing, whereby the water-based pigmented ink can be applied in more than one layer, e.g., in the form of two to ten layers, preferably three to eight layers. Gravure printing is a printing technique in which the elements to be reproduced are recesses in a printing plate, which is inked before printing. The ink is primarily located in the recesses and is transferred to the substrate, such as a wood fiberboard, due to the pressure of the printing plate and adhesive forces. In contrast, in digital printing, the print image is transferred directly from a computer to a printing press, such as a laser printer or inkjet printer.This eliminates the need for a static printing plate. Both processes allow the use of water-based inks or UV-based colorants. It is also conceivable to combine the aforementioned gravure and digital printing techniques. A suitable combination of printing techniques can be applied directly to the substrate or the layer to be printed, or before printing by adjusting the electronic data sets. Along with the decorative element, the markings required for press alignment are also printed.

[0068] The liquid second primer, applied after the printed decoration, has a solids content of between 40 and 60 wt%, preferably 45 and 55 wt%, and particularly preferably 50 wt%. The amount of the second primer layer applied to the printed decoration can be between 10 and 40 g / m², preferably 10 and 30 g / m², and particularly preferably 20 g / m². Isocyanate-based compounds are preferred as primers, with non-aromatic, aliphatic isocyanates, such as hexamethylene diisocyanate, isophorone diisocyanate, or prepolymers containing these isocyanates being particularly preferred.

[0069] In a further non-inventive variant of the process, a film made of thermoplastic polymer, in particular a film made of thermoplastic polyurethane, is used as the thermoplastic polymer layer.

[0070] The thickness of the film, in particular the TPU film, is between 50 and 150 µm, preferably 80 and 120 µm, and particularly 100 µm. Multiple films can also be used, which are either applied individually during pressing or bonded together in a preceding step.

[0071] To achieve desired properties, thermoplastic films, such as TPU films, can be additionally coated with a surface finish, such as a lacquer. This can positively influence their resistance to scratches, chemicals, abrasion, and other stresses. A lacquer can also improve their performance with regard to static electricity and dirt accumulation. The lacquer can even be applied during the film manufacturing process.

[0072] The TPU film used here can also contain abrasion-resistant particles, such as abrasion-resistant particles preferably selected from the group consisting of aluminum oxides, boron carbides, silicon dioxides, silicon carbides, and glass particles. Abrasion-resistant particles with grain sizes in classes F180 to F240, preferably F200 or F220, are preferred. The grain size of class F180 covers a range of 53–90 µm, F220 45–75 µm, F230 34–82 µm, and F240 28–70 µm (FEPA standard). The abrasion-resistant particles must not be too fine (risk of dust formation) but also not too coarse. The size of the abrasion-resistant particles therefore represents a compromise.

[0073] According to the invention, a dispersion of a thermoplastic polymer, in particular a dispersion of a thermoplastic polyurethane, is applied as the thermoplastic polymer layer. In this case, a dispersion, in particular a TPU dispersion, with a solids content between 20 and 60 wt%, preferably between 30 and 50 wt%, and in particular 40 wt%, is used. The application rate of the thermoplastic polymer is between 50 and 150 g / m² < fl, preferably between 70 and 130 g / m² < fl, and in particular preferably between 90 and 110 g / m² < fl, such as 100 g / m² < fl.

[0074] As described above, when applying thermoplastic polymers, particularly TPU, the TPU layer can be coated with a lacquer layer after compression molding to increase abrasion resistance. For this purpose, a lacquer system consisting of at least one lacquer layer and at least one topcoat, preferably a UV lacquer, is applied as a protective layer to improve scratch resistance. The topcoat may contain nanoparticles, e.g., made of silica. No solvent-based lacquers are used. For further details, please refer to the information above.

[0075] As mentioned above, a counter-tension layer of PF or PLF resin is applied to the underside of the wood substrate or wood-based panel. This balances the tensile forces acting on the top side of the wood-based panel.

[0076] In a preferred embodiment, the backing layer is designed as a cellulose layer (paper layer) impregnated with PF resin or PLF resin.

[0077] The PF resin or PLF resin used as a countercoat can also be applied in liquid form. In the case of liquid application, PF resin or PLF resin with a solids content between 30 and 80 wt%, preferably between 40 and 60 wt%, and particularly 50 wt%, is used. The application rate of the phenol-formaldehyde resin is between 30 and 100 g / m² < fl, preferably between 40 and 80 g / m² < fl, and particularly preferably between 50 and 70 g / m² < fl, such as 60 g / m² < fl.

[0078] As mentioned, the layered structures are pressed into a laminate in a single operation under the influence of temperature and pressure in a short-cycle press or a continuous press. Typical short-cycle presses operate, for example, at a pressure of 30 to 60 kg / cm², a surface temperature of approximately 160–195 °C, and a pressing time of 10 to 30 seconds.

[0079] Accordingly, in a non-inventive variant, the present method enables the provision of a melamine-free composite material with the following layer structure (from bottom to top): backing layer, preferably made of PF resin or PLF resin - wood-based panel - at least one urea-formaldehyde resin primer - at least one layer of thermoplastic polymer.

[0080] In a further non-inventive variant, the present method enables the provision of a melamine-free composite material with the following layer structure (from bottom to top): backing layer, preferably made of PF resin or PLF resin - wood-based panel - at least one urea-formaldehyde resin primer - at least one color primer - at least one first primer layer - at least one decorative layer applied by direct printing - at least one second primer layer - at least one film made of thermoplastic polyurethane.

[0081] In yet another non-inventive variant, the present method enables the provision of a melamine-free composite material with the following layer structure (from bottom to top): backing layer, preferably made of PF resin or PLF resin - wood-based panel - at least one urea-formaldehyde resin primer - at least one color primer - at least one first primer layer - at least one decorative layer applied by direct printing - at least one second primer layer - at least one layer of thermoplastic polyurethane - optional UV lacquer.

[0082] The present invention will be explained below using several examples. Example of implementation 1:

[0083] A decorative paper (paper weight: 80 g / m²) is impregnated with a urea resin on an impregnation line. The impregnation tunnel runs at a speed of 60 m / min. The application rate is approximately 160 g / m² of liquid, which corresponds to a solid application rate of 80 g / m². The impregnating resin contains the usual additives such as hardener, wetting agent, etc. It is important to ensure that, after impregnation, the decorative sheet is sharply trimmed from both the top and bottom using a doctor blade.

[0084] After intermediate drying to a residual moisture content of approximately 20 wt%, a TPU dispersion is applied to the top surface using grids or rollers, and a phenolic resin or polyurethane dispersion is applied to the back surface.

[0085] The PF resin or PLF resin or the PU dispersion was applied in an amount of 60 g / m² < fl. (solids: 50 wt%).

[0086] The TPU dispersion was applied at a rate of 100 g / m² (solids content: 40 wt%).

[0087] The impregnating agent is then dried to a residual moisture content of approximately 6% by weight. It is then cut or cut into sheets (format: 2800 x 2070 mm).

[0088] The impregnating agent is then pressed onto a 19 mm thick particleboard. A white decorative paper with the same paper weight and resin coating is used as the reverse side. The pressing parameters were: P = 40 kg / cm², t = 20 sec, and T (top / bottom) = 180°C. A surface test was carried out in accordance with DIN EN 14322:2021 "Melamine-coated boards for interior use". The values ​​required by the standard were achieved. Example 2 (not according to the invention):

[0089] An HDF board (format: 2800 x 2070 x 7 mm) is first primed with a urea-formaldehyde resin (application rate: approx. 25 g urea-formaldehyde resin fl. / m², solids content: approx. 35 wt.%) in a direct printing line operating at a speed of 80 m / min. The impregnating resin contains the usual additives such as hardener, wetting agent, etc. The resin is then dried in a circulating air dryer.

[0090] A primer consisting of titanium dioxide and casein is then applied. This primer is applied up to seven times, with an application rate of 5-10 g of primer per surface. After each coat, intermediate drying is carried out using a fan-assisted and / or infrared dryer.

[0091] A primer is then applied (amount 10-20 g fl / m²). This is also dried.

[0092] A decorative design is then printed onto this primer using either gravure or digital printing. The print is then dried in a circulating air dryer.

[0093] An isocyanate-based primer is applied to the dried print (application rate: approx. 20 g fl. / m 2< , solids content: approx. 50 wt%).

[0094] The sheets are then coated on the top side with a TPU film (film thickness: 100 µm) using a KT press. The TPU film contains approximately 15 g of corundum / m² with a grain size of F200 according to the FEPA standard.

[0095] The reverse side of the board is coated with a backing layer, either in liquid form or as sheets. A phenolic resin is used as the impregnating resin for this backing layer.

[0096] The assembly is then pressed in the KT press at T=160°C, p=40 kg / cm², and t=24 sec. After cooling, the adhesion of the film is first tested using a cross-cut test (DIN EN ISO 2409-2013-06). The panels are then cut into raw bonding compounds and subsequently fitted with a glueless profile. The surface was tested according to DIN EN 16511-2014: "Panels for floating installation - Semi-rigid, multilayer modular floor coverings (MMF) with abrasion-resistant top layer." The requirements of service class 31 were met. Some important tests are listed in the following table. Test Result DIN EN 16511 Usage class 31 / 32 Abrasion resistance, IP method A 1500 cycles 600 / 1200 cycles Impact resistance, large ball 1600 mm 800 / 1200 mm Stain resistance Group 1 + 2 Grade 5 Grade 5 Group 3 Grade 4 Grade 4 Micro-scratch resistance class - - / MSR-A3 Example of implementation 3:

[0097] A decorative paper (paper weight: 80 g / m²) is impregnated with a urea resin on an impregnation line. The impregnation tunnel runs at a speed of 60 m / min. The application rate is approximately 160 g / m² of liquid, which corresponds to a solid application rate of 80 g / m². The impregnating resin contains the usual additives such as hardener, wetting agent, etc. It is important to ensure that, after impregnation, the decorative sheet is sharply trimmed from both the top and bottom using a doctor blade.

[0098] After intermediate drying to a residual moisture content of approximately 20 wt%, a phenolic powder resin or PLF powder resin is sprinkled onto the back of the impregnating agent using a spreader in an S-bend (30 g solid phenolic resin / m²).

[0099] A TPU dispersion is applied to the top surface using a roller applicator. The TPU dispersion was applied at a rate of 100 g / m² (solids content: 40 wt%). The impregnating agent is then dried to a residual moisture content of approximately 6 wt%.

[0100] It is then cut or sliced ​​into sheets (format: 2800 x 2070 mm). The impregnating agent is then pressed onto a 19 mm thick chipboard panel. A white decorative paper with the same paper weight and resin coating is used as the backing. The pressing parameters were: p = 40 kg / cm², t = 20 sec, and T (top / bottom) = 180°C. Example of implementation 4:

[0101] A decorative paper (paper weight: 80 g / m²) is impregnated with a urea resin on an impregnation line. The impregnation tunnel runs at a speed of 60 m / min. The application rate is approximately 160 g / m² of liquid, which corresponds to a solid application rate of 80 g / m². The impregnating resin contains the usual additives such as hardener, wetting agent, etc. It is important to ensure that, after impregnation, the decorative sheet is sharply trimmed from both the top and bottom using a doctor blade.

[0102] After intermediate drying to a residual moisture content of approximately 20% by weight, a phenolic resin is applied to the back using grids or rollers.

[0103] The phenolic resin was applied at a rate of 60 g / m² (solids content: 50% by weight). The impregnating agent was then dried to a residual moisture content of approximately 6% by weight. It was then cut or sliced ​​into sheets (format: 2800 x 2070 mm).

[0104] The impregnating agent is then pressed onto a 6 mm chipboard panel. A white decorative paper with the same paper weight and resin coating is used as the reverse side. The pressing parameters were: P = 40 kg / cm², t = 20 sec, and T (top / bottom) = 180°C.

[0105] An isocyanate-based primer is applied to the impregnated surface (application quantity: approx. 20 g fl. / m 2< , solids content: approx. 50 wt%).

[0106] The panel is then coated in several layers with a UV or ESH lacquer, with intermediate curing, in a coating line. The lacquer layer is applied at a rate of 30 g / m². The coating system can consist of at least one ESH lacquer layer, which is gelled after application using an ESH lamp, and at least one topcoat, which is partially cured after application using an excimer lamp. The entire coating system is then fully cured with an ESH lamp. Afterward, the panel is cut into floorboards in a flooring line.

[0107] This results in advantages. Avoiding labeling, reacting to reclassification

Claims

1. A process for the production of a composite material free of melamine-formaldehyde resin comprising at least one paper layer as carrier material, at least one polymer layer of a thermoplastic polymer provided on the upper side of the paper layer and at least one resin-containing layer provided on the underside of the paper layer, comprising the steps: - Providing at least one layer of paper, - Applying at least one layer of a urea-formaldehyde resin to the upper side of the paper layer to impregnate the paper layer, - after impregnation, applying at least one layer of the thermoplastic polymer, in particular thermoplastic polyurethane, to the upper side of the paper layer, the thermoplastic polymer being applied as a dispersion with a solids content of 20-60% by weight; - Applying at least one resin-containing layer to the underside of the paper layer, and - Drying and pressing of the layer structure.

2. Process according to claim 1, characterized in that the one paper layer is a decorative paper layer.

3. Process according to one of the preceding claims, characterized in that the liquid application quantity of the urea-formaldehyde resin is between 100 and 250 g / m2, preferably between 130 and 200 g / m2, in particular preferably between 150 and 180 g / m2.

4. Process according to one of the preceding claims, characterized in that the dispersion of the thermoplastic polymer with a solids content of between 30 and 50% by weight, in particular 40% by weight, is used and the application quantity of the thermoplastic polymer is between 50 and 150 g / m2fl, preferably between 70 and 130 g / m2fl, in particular preferably between 90 and 110 g / m2fl, such as 100 g / m2fl.

5. Process according to one of the preceding claims, characterized in that thermoplastic polyurethane (TPU) is used as a dispersion for coating.

6. Process according to one of the preceding claims, characterized in that an adhesive layer in the form of a phenol-formaldehyde resin (PF resin), a phenol-lignin-formaldehyde resin (PLF resin) or a polyurethane (PU) is applied to the underside of the carrier material as the resin-containing layer.

7. Process according to claim 6, characterized in that the phenol-formaldehyde resin (PF resin) or phenol-lignin-formaldehyde resin (PLF resin) or the polyurethane is applied to the underside of the paper layer as a liquid application or as a powder application.

8. Process according to claim 7, characterized in that, in the case of a liquid application, phenol-formaldehyde resin (PF resin) or phenol-lignin-formaldehyde resin (PLF resin) with a solids content of between 30 and 80% by weight, preferably between 40 and 60% by weight, in particular 50% by weight, is used and the amount of phenol-formaldehyde resin (PF resin) or phenol-lignin-formaldehyde resin (PLF resin) applied is 20-30% by weight based on the paper weight.

9. Process according to claim 7, characterized in that, in the case of powder application, phenol-formaldehyde resin (PF resin) or phenol-lignin-formaldehyde resin (PLF resin) is applied in an amount of between 10 and 50 g / m2, preferably between 20 and 40 g / m2, more preferably between 25 and 35 g / m2.

10. Process according to one of the preceding claims, characterized in that, after application of all layers to the paper layer, the resulting impregnate is dried to a defined residual moisture content of 5-10% by weight, preferably 6% by weight.

11. Process according to one of the preceding claims, characterized in that the coated and impregnated paper layer is pressed with a carrier board, in particular a wood-based board such as medium-density fibreboard (MDF) or high-density fibreboard (HDF) or chipboard, in a short-cycle press or in a continuously operating press.

12. Process according to one of the preceding claims, characterized in that, after pressing, the (upper) layer of thermoplastic polymer is applied with a covering layer comprising at least one lacquer layer and at least one top coat, preferably UV or electron beam hardenable lacquer (ESH lacquer), to improve the scratch resistance.

13. Melamine-free composite material producible in a process according to one of the preceding claims, characterized by the following layer structure: optional adhesive layer - layer of a phenol-formaldehyde resin or phenol-lignin-formaldehyde resin - paper layer impregnated with urea-formaldehyde resin - layer of TPU - optional lacquer.

14. The melamine-free composite material according to claim 13, characterized by the following layer structure: Wood-based panel - adhesive layer - layer of phenol-formaldehyde resin or phenol-lignin-formaldehyde resin - paper layer impregnated with urea-formaldehyde resin - layer of TPU - optional lacquer.