Method for producing a composite material that is free of melamine-formaldehyde resin

Abstract

The present invention relates to a method for producing a composite material that is free of melamine-formaldehyde resin and comprises at least one carrier material, at least one polymer layer or lacquer layer provided on the top surface of the carrier material, and at least one resin-containing layer provided on the bottom surface of the carrier material, said method comprising the steps of: providing at least one carrier material; applying at least one layer of a urea-formaldehyde resin to the carrier material; applying at least one layer of a thermoplastic elastomer to the carrier material; applying at least one melamine-free resin-containing layer to the bottom side of the carrier material; and drying and compressing the layer structure. Instead of a thermoplastic elastomer, a lacquer can be applied after the compressing process.

Description

[0001] Process for producing a composite material free from melamine-formaldehyde resin

[0002] The present invention relates to a process for producing a composite material free of melamine-formaldehyde resin and to a melamine-free composite material produced by this process.

[0003] Description

[0004] Melamine resin surfaces have been used in a wide variety of applications for decades. These surfaces are often used where high demands are placed on easy cleaning and disinfection. A particular advantage is that melamine surfaces are not inherently a good growth substrate for bacteria. Further advantages include their very high chemical and mechanical resistance. The melamine layer also provides an effective barrier against off-gassing from the substrate. These advantages of melamine resin surfaces are particularly utilized in laminate flooring and furniture surfaces.

[0005] However, the potentially negative environmental effects of melamine itself are currently being discussed. These include its persistence (poor biodegradability) and its mobility after release. Although melamine is only detectable in harmless traces in melamine resin surfaces, the aforementioned discussion is naturally causing uncertainty in the market.

[0006] Another problem is that alternative materials are either not available in the required quantities, lack the same properties, and / or cannot be processed on currently available production lines (e.g., short-cycle presses, laminate presses, etc.). The same applies to the buyers of the coated panels, who naturally also consider the good mechanical properties during processing during transport through processing lines, etc.

[0007] The idea of ​​covering the finished melamine resin surface with a thin protective layer after production is also unfortunately not effective, as this protective layer could be quickly removed by abrasion during walking (laminate flooring) or disinfection (furniture surfaces). Furthermore, this would not solve the melamine dust generated during processing. In addition to melamine resin, a whole range of resins are known for impregnating paper for decorative applications. However, these synthetic resins have disadvantages that make their use as the sole resin impossible.

[0008] Urea-formaldehyde resins, for example, are used individually or in a mixture with melamine-formaldehyde resins for core impregnations. However, they have the disadvantage that these resins do not flow into a film during further processing of the impregnated materials in short-cycle presses. Furthermore, urea-formaldehyde resins are susceptible to hydrolysis and chemically inresistant.

[0009] Another synthetic resin used for various applications is phenol-formaldehyde resin. This resin, which has a light brown to medium brown color, is used for impregnating core layers of laminates or underlay sheets. However, due to its inherent color, it cannot be used for impregnating the surfaces of decorative papers. In addition, exposure to sunlight on the resin causes the color to deepen. Furthermore, direct contact of phenol impregnates with food should be avoided.

[0010] Another resin system that could be used is acrylic resin. However, when used alone on a paper, this produces a brittle impregnated product that cannot be processed in a short-cycle press.

[0011] An alternative for surfaces subject to less mechanical and chemical stress are so-called finish films. These are decorative products with a core impregnation of urea-formaldehyde resin and acrylate resin, coated on the top with a varnish (UV or ESH varnish). These films are laminated onto wood-based substrates using laminating lines. Compared to melamine surfaces, they have significantly inferior properties, making them unsuitable for applications requiring higher or higher levels of stress. Processing on short-cycle presses is also not possible.

[0012] The invention is therefore based on the technical problem of overcoming the disadvantages resulting from this 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 impregnate, should be developed that, after processing on short-cycle presses and continuously operating presses, leads to products that have approximately the property profile of a melamine surface. The impregnate should be producible on the existing impregnation channels. Further processing should also continue to be possible on short-cycle presses and continuously operating presses without technological or technical changes. The cost of the product should not change significantly.

[0013] This object is achieved according to the invention by a method having the features of claims 1 or 2 and a composite material produced thereby.

[0014] Accordingly, according to a first aspect of claim 1, a method for producing a composite material free of melamine-formaldehyde resin comprising at least one carrier material, at least one polymer layer provided on the upper side of the carrier material and at least one resin-containing layer provided on the underside of the carrier material is provided, the method comprising the following steps:

[0015] Providing at least one carrier material,

[0016] - applying at least one layer of a urea-formaldehyde resin to the carrier material,

[0017] - applying at least one layer of a thermoplastic elastomer to the top of the carrier material,

[0018] - applying at least one melamine-free resin-containing layer to the underside of the substrate, and

[0019] - Drying and pressing the layer structure.

[0020] Thus, a process is provided for producing a composite material for use in flooring laminates or furniture elements, in which the use of melamine-formaldehyde resin can be completely dispensed with. In particular, the surface layers provided on the carrier material (i.e., layers on the top and bottom of the carrier material) do not contain any melamine-formaldehyde resin. Surprisingly, the composite materials produced using the present process meet the requirements necessary for floor coverings, as shown in the exemplary embodiments. The order of application of the layer of thermoplastic elastomer to the top of the carrier material and the application of the resin-containing layer to the bottom of the carrier material can be flexible and variable, i.e.It is possible to first apply the thermoplastic elastomer to the top side of the substrate and then apply the melamine-free resin-containing layer to the underside of the substrate, or to first apply the melamine-free resin-containing layer to the underside of the substrate and then apply the thermoplastic elastomer to the top side of the substrate. It is also possible to apply the thermoplastic elastomer to the top side and the melamine-free resin-containing layer to the underside simultaneously. The order depends on the respective production lines.

[0021] For the purposes of the present invention, the term "thermoplastic elastomers" refers to plastics that behave similarly to classic elastomers at room temperature, but can be plastically deformed when heat is applied, thus exhibiting thermoplastic behavior. Thermoplastic elastomers are materials in which elastic polymer chains are embedded in thermoplastic material. They can be processed in a purely physical process combining high shear forces, heat, and subsequent cooling. Although no chemical crosslinking through time- and temperature-intensive vulcanization is necessary, as is the case with elastomers, the manufactured parts still exhibit rubber-elastic properties due to their special molecular structure. Further exposure to heat and shear forces leads to the material melting and deformation again.However, this also means that thermoplastic elastomers are far less thermally and dynamically resilient than standard elastomers. Thermoplastic elastomers are therefore not a "successor product" to conventional elastomers, but rather a complement that combines the processing advantages of thermoplastics with the material properties of elastomers. Well-known thermoplastic elastomers include thermoplastic polyamide elastomers (TPA), thermoplastic copolyesters (TPC), thermoplastic styrene block copolymers (TPS), olefin-based thermoplastic elastomers (TPO), and thermoplastic urethanes (TPU) (see Wikipedia "Thermoplastic Elastomers").

[0022] For the purposes of the present invention, thermosetting resins are used as resins, and here preferably melamine-free formaldehyde resins.

[0023] It is also possible not to use a thermoplastic elastomer to coat the surface, but instead to use a layer of lacquer, whereby this lacquer layer is applied to the top or surface of the carrier material after the layer structure has been pressed together.

[0024] According to a second aspect of claim 2, a method for producing a composite material free of melamine-formaldehyde resin comprising at least one carrier material, at least one lacquer layer provided on the upper side of the carrier material and at least one resin-containing layer provided on the underside of the carrier material is provided, the method comprising the following steps:

[0025] Providing at least one carrier material,

[0026] - applying at least one layer of a urea-formaldehyde resin to the carrier material,

[0027] - applying at least one melamine-free resin-containing layer to the underside of the substrate, and

[0028] - Drying and pressing the layer structure;

[0029] - Applying at least one layer of varnish to the top of the pressed layer structure.

[0030] For the purposes of this invention, the term "paint" refers to a liquid or powder coating material that is applied thinly to objects and, through chemical or physical processes (e.g., evaporation of the solvent), builds up into a continuous, solid film. Paints typically consist of binders such as resins, dispersions or emulsions, fillers, pigments, solvents, and additives (see Wikipedia "Paint").

[0031] Paper layer as carrier material

[0032] In one embodiment of the present method, the at least one carrier material is a paper layer, preferably a decorative paper layer.

[0033] The present method may therefore, according to the first aspect, comprise the following steps:

[0034] Providing at least one paper layer, - applying at least one layer of a urea-formaldehyde resin to the paper layer to impregnate the paper layer,

[0035] - applying at least one layer of a thermoplastic elastomer, in particular thermoplastic polyurethane, to the upper side of the impregnated paper layer,

[0036] - applying at least one melamine-free resin-containing layer as an adhesive layer to the underside of the impregnated paper layer, and

[0037] - Drying and pressing the layer structure.

[0038] The paper layers used here, especially decorative paper layers, have a paper weight between 60 and 120 g / m 2 , preferably 80 g / m 2 on.

[0039] Decorative papers are specialty papers for surface finishing of wood materials, allowing for a wide variety of decorative finishes. In addition to the typical prints of various wood textures, more sophisticated prints of geometric shapes or artistic, decorative designs are available. There are virtually no restrictions on the choice of motifs. To ensure optimal printability, the paper used must exhibit good smoothness and dimensional stability, as well as be suitable for penetration by the necessary synthetic resin impregnation.

[0040] As mentioned, a urea-formaldehyde resin is first applied to the carrier material. When paper layers are used as the carrier material, the paper layer is partially or completely impregnated with the urea-formaldehyde resin, whereby the urea-formaldehyde resin penetrates the paper layer. In this case, the term "impregnation" refers to the complete or partial saturation of the paper layer with the resin. The urea resin used here is used for the so-called core impregnation of the paper. Thus, melamine-free paper layers are used as the carrier material.

[0041] In one variant, the liquid application quantity of the urea-formaldehyde resin is between 100 and 250 g / m 2 , preferably between 130 and 200 g / m 2 , particularly preferably between 150 and 180 g / m 2 , such as 160 g / m 2The fixed application quantity of urea-formaldehyde resin is between 50 and 125 g / m 2 , preferably between 65 and 100 g / m 2 , particularly preferably between 75 and 90 g / m 2 , such as 80 g / m 2 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.

[0042] During the production of the impregnates, the urea resin is applied in an impregnation tank. After immersion in the tank, the resin is spread to a defined thickness using doctor blades or squeegees. The impregnate is then intermediately dried in a hot air flotation dryer, e.g., to a residual moisture content of 20 wt%.

[0043] A corresponding impregnation system 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

[0044] - a first drying station.

[0045] Specifically, the impregnation system comprises impregnation tanks or impregnation immersion baths (as impregnation stations), if necessary a breathing section, a doctor blade system / squeeze roller pair for removing excess resin, at least one dryer (e.g. a floating dryer), optionally a screen unit, optionally a powder spreader and an optional second dryer, at least one cooling device (e.g. a cooling roller system).

[0046] After core impregnation, the next step is to apply the thermoplastic elastomer, particularly thermoplastic polyurethane, to the paper layer. In this case, a dispersion of a thermoplastic elastomer with a solids content between 20 and 60 wt%, preferably between 30 and 50 wt%, especially 40 wt%, is used. The application quantity of the thermoplastic elastomer is between 50 and 150 g / m². 2 fl, preferably between 70 and 130 g / m 2 fl, particularly preferably between 90 and 110 g / m 2 fl, such as 100 g / m 2 fl.. The application quantity of the thermoplastic elastomer is approximately 30-50 wt% based on the paper weight.

[0047] Applying the thermoplastic elastomer as a liquid (in the form of a dispersion) allows for the application of the thermoplastic elastomer in variable quantities, in contrast to the use of thermoplastic elastomer films, which can only be used with specified film weights (film quantities). As already indicated, thermoplastic polyurethane is preferred as the thermoplastic elastomer, especially as a surface layer.

[0048] Thermoplastic polyurethane (TPII) belongs to a class of polyurethanes - plastics with many properties, such as high abrasion resistance, low temperature performance, high shear strength, high elasticity, transparency, oil and grease resistance.

[0049] TPII 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, an enormous variety of different TPIIs can be produced. This allows the polymer structure to be finely tuned to the desired final properties of the material.

[0050] TPII is preferably used as a dispersion (TPII beads in water) for coating. During the drying process of the impregnate, the TPU reacts and is incorporated into the polymer matrix, especially the impregnate, during compression. It is advantageous if the glass transition temperatures of the TPU are as low as possible to maintain the elastic properties.

[0051] As already mentioned above, a melamine-free resin-based layer is applied to the underside of the paper layer. In the case of the paper layer, this melamine-free resin-based layer acts as an adhesive layer or adhesive coating.

[0052] A phenol-formaldehyde resin (PF resin), phenol-lignin-formaldehyde resin (PLF resin) or a polyurethane (PU) can be used as an adhesive layer (or adhesive coat).

[0053] 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.

[0054] 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%, especially 50 wt%, is used. The application quantity of PF resin or PLF resin is between 30 and 100 g / m 2 fl, preferably between 40 and 80 g / m 2fl, particularly preferably between 50 and 70 g / m 2 fl, such as 60 g / m 2 fl. The application quantity of the PF resin or PLF resin is approximately 20-30 wt% based on the paper weight.

[0055] In case of powder application, PF resin or PLF resin is applied in a quantity between 10 and 50 g / m 2 , preferably between 20 and 40 g / m 2 , particularly preferably between 25 and 35 g / m 2 , such as 30 g / m 2 The powdered resin is applied to the substrate by electrostatic charging and optionally melted. Application can also be achieved by powder coating using the tribo-process, which involves frictional charging of the powder being applied.

[0056] "Partial melting" in the context of this application means that the melamine-free resin layer is not yet fully polymerized; rather, the polymerization is stopped at an intermediate stage, where further crosslinking or polymerization is still possible at a later processing stage. The partial melting of the applied layer of powdered resin can be achieved using an IR emitter, microwave systems, or similar devices. The use of IR emitters is particularly preferred.

[0057] In a further embodiment, as an alternative to the phenol-formaldehyde resin, polyurethane is applied as at least one melamine-free adhesive layer or adhesive coat to the underside of the carrier material. The amount of the polyurethane adhesive coat is 10-40 wt%, preferably 20-30 wt%, based on the paper weight.

[0058] After application of all layers to the paper layer, the resulting impregnate is dried to a defined residual moisture content, e.g. 5-10 wt%, preferably 6 wt%.

[0059] A paper layer coated and impregnated in this way, e.g., a decorative paper layer, can be pressed onto a carrier board, e.g., a wood-based panel such as MDF, HDF, or particleboard, in a short-cycle press or a continuously operating press. In particular, the impregnated material can be cut to suitable sizes and pressed onto wood-based panels.

[0060] After compression, in one embodiment, the (upper) layer of thermoplastic elastomer can be coated with a lacquer layer to increase abrasion resistance. For this purpose, a lacquer structure consisting of at least one lacquer layer and at least one topcoat, preferably UV or ESH lacquer, is applied as a covering layer to improve scratch resistance. The topcoat can contain nanoparticles, e.g., silica. No solvent-based lacquers are used.

[0061] Radiation-curable, acrylate-containing lacquers are used in particular for the lacquer layer and the topcoat. The radiation-curable lacquers used typically contain (meth)acrylates, such as polyester (meth)acrylates, polyether (meth)acrylates, epoxy (meth)acrylates or urethane (meth)acrylates. It is also conceivable that the acrylate used or the acrylate-containing lacquer contains substituted or unsubstituted monomers, oligomers and / or polymers, in particular in the form of acrylic acid, acryl 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 hydroxyl, amino, epoxy and / or carboxyl groups. The acrylates mentioned enable crosslinking or curing in the presence of UV orElectron beams (EBC).

[0062] The lacquer layer is applied in a quantity between 50 and 100 g / m 2 , preferably between 60 and 80 g / m 2 applied, while the top coat is applied in an amount between 10 and 30 g / m 2 , preferably 30 g / m 2 The coating system can consist of at least one EBC coating layer, which is cured with an EBC lamp after application, and at least one topcoat, which is cured with an excimer lamp after application. The entire coating system is then cured with an EBC lamp.

[0063] In one embodiment, the present method thus comprises the following steps:

[0064] - Providing at least one layer of paper as carrier material,

[0065] - applying at least one layer of a urea-formaldehyde resin to the paper layer to impregnate the paper layer,

[0066] - applying at least one layer of a thermoplastic polyurethane to the top of the impregnated paper layer,

[0067] - applying at least one melamine-free adhesive layer to the underside of the impregnated paper layer, and

[0068] - Drying and pressing the layer structure,

[0069] Optionally, applying at least one varnish to the at least one layer of thermoplastic polyurethane. In a further embodiment, the present method thus comprises the following steps:

[0070] - Providing at least one layer of paper as carrier material,

[0071] - applying at least one layer of a urea-formaldehyde resin to the paper layer to impregnate the paper layer,

[0072] - applying at least one layer of a thermoplastic polyurethane to the top of the impregnated paper layer,

[0073] - applying at least one powdered layer of a PF resin or PLF resin as a melamine-free adhesive layer to the underside of the impregnated paper layer and melting the powdered layer,

[0074] - Drying and pressing the layer structure, and

[0075] Optional application of at least one varnish to the at least one layer of thermoplastic polyurethane,

[0076] In another embodiment, the present method thus comprises the following steps:

[0077] - Providing at least one layer of paper as carrier material,

[0078] - applying at least one layer of a urea-formaldehyde resin to the paper layer to impregnate the paper layer,

[0079] - applying at least one layer of a thermoplastic polyurethane to the top of the impregnated paper layer,

[0080] - Application of at least one liquid layer of a PF resin or PLF resin as a melamine-free adhesive layer on the underside of the impregnated paper layer,

[0081] - Drying and pressing the layer structure,

[0082] Optional application of at least one varnish to the at least one layer of thermoplastic polyurethane.

[0083] In yet another embodiment, the present method thus comprises the following steps:

[0084] - Providing at least one layer of paper as carrier material,

[0085] - applying at least one layer of a urea-formaldehyde resin to the paper layer to impregnate the paper layer, - applying at least one layer of a thermoplastic polyurethane to the top of the impregnated paper layer,

[0086] - Application of at least one liquid layer of a polyurethane as a melamine-free adhesive layer on the underside of the impregnated paper layer,

[0087] - Drying and pressing the layer structure,

[0088] Optional application of at least one UV varnish to the at least one layer of thermoplastic polyurethane.

[0089] Accordingly, the present method according to the first aspect enables, in one variant, the provision of a first melamine-free composite material having the following layer structure (from bottom to top): melamine-free adhesive layer, preferably a layer of a PF resin or PLF resin or polyurethane - paper layer impregnated with urea-formaldehyde resin - layer of TPU - optionally varnish.

[0090] In a further variant, the present process enables the provision of a melamine-free composite material with the following layer structure (from bottom to top):

[0091] Wood-based panel - melamine-free adhesive layer, preferably a layer of PF resin or PLF resin or polyurethane - paper layer impregnated with urea-formaldehyde resin - layer of TPU - optional varnish.

[0092] As already described above, the use of a thermoplastic elastomer to coat the surface can be omitted and instead a lacquer build-up can be applied to the layer structure after pressing.

[0093] According to the second aspect, the present method may therefore also comprise the following steps:

[0094] Providing at least one layer of paper,

[0095] - applying at least one layer of a urea-formaldehyde resin to the paper layer to impregnate the paper layer,

[0096] - Application of at least one melamine-free resin-containing layer as an adhesive layer on the underside of the impregnated paper layer,

[0097] - Drying and pressing the layer structure, and

[0098] Applying at least one layer of a lacquer to the top of the pressed layer structure. In a further embodiment, the present method thus comprises the following steps:

[0099] - Providing at least one layer of paper as carrier material,

[0100] - applying at least one layer of a urea-formaldehyde resin to the paper layer to impregnate the paper layer,

[0101] - applying at least one powdered layer of a PF resin or PLF resin as a melamine-free adhesive layer to the underside of the impregnated paper layer and melting the powdered layer,

[0102] - Drying and pressing the layer structure, and

[0103] - Applying at least one layer of varnish to the top of the pressed layer structure.

[0104] In another embodiment, the present method thus comprises the following steps:

[0105] - Providing at least one layer of paper as carrier material,

[0106] - applying at least one layer of a urea-formaldehyde resin to the paper layer to impregnate the paper layer,

[0107] - Application of at least one liquid layer of a PF resin or PLF resin as a melamine-free adhesive layer on the underside of the impregnated paper layer,

[0108] - Drying and pressing the layer structure, and

[0109] - Applying at least one layer of varnish to the top of the pressed layer structure.

[0110] In yet another embodiment, the present method thus comprises the following steps:

[0111] - Providing at least one layer of paper as carrier material,

[0112] - applying at least one layer of a urea-formaldehyde resin to the paper layer to impregnate the paper layer,

[0113] - Application of at least one liquid layer of a polyurethane as a melamine-free adhesive layer on the underside of the impregnated paper layer,

[0114] - Drying and pressing the layered structure. - Applying at least one layer of varnish to the top of the pressed layered structure.

[0115] The above-mentioned information on the composition and application quantities of resin and varnish also apply to the latter embodiments of the second aspect of the process.

[0116] Accordingly, the present method according to the second aspect enables, in one variant, the provision of a melamine-free composite material having the following layer structure (from bottom to top): melamine-free adhesive layer, preferably a layer of a PF resin or PLF resin or polyurethane paper layer impregnated with urea-formaldehyde resin - lacquer structure.

[0117] In a further variant, the present method according to the second aspect enables the provision of a melamine-free composite material with the following layer structure (from bottom to top):

[0118] Wood-based panel - melamine-free adhesive layer, preferably a layer of a PF resin or PLF resin or polyurethane - paper layer impregnated with urea-formaldehyde resin - lacquer structure.

[0119] Wood-based panel as support material

[0120] In another embodiment of the present process, a wood-based panel, preferably a medium-density fiberboard (MDF), high-density fiberboard (HDF), a plywood board, a particleboard, or a wood-plastic composite board (WPC), is used as the carrier material. Particularly preferred wood-based panels are wood-fiberboards with urea-formaldehyde glue as the binder, such as an HDF panel with urea-formaldehyde glue.

[0121] The present method according to the first aspect may therefore also comprise the following steps:

[0122] Providing at least one wood-based panel as a carrier material, applying at least one layer of a urea-formaldehyde resin to the upper side of the wood-based panel, - applying at least one layer of at least one thermoplastic elastomer; in particular of a thermoplastic polyurethane;

[0123] - applying at least one melamine-free 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

[0124] - Drying and pressing the layer structure.

[0125] In a preferred embodiment, the present method comprises the following steps:

[0126] Providing at least one wood-based panel as a carrier material,

[0127] - applying at least one layer of a urea-formaldehyde resin to the top of the wood-based panel,

[0128] - Application of at least one coat of primer;

[0129] - Application of at least one first primer layer,

[0130] - Applying a printed decoration;

[0131] - Application of at least a second primer layer,

[0132] - applying at least one layer of at least one thermoplastic elastomer;

[0133] - applying at least one melamine-free countercoat, preferably in the form of a layer of a PF resin or PLF resin, to the underside of the wood-based panel as a countercoat, and

[0134] - Drying and pressing the layer structure.

[0135] Urea-formaldehyde resin is therefore used as a resin primer or roller primer. The application quantity of the resin primer can be between 10 - 40 g resin fl / m 2 , preferably 20 - 30 g resin fl / m 2 , e.g. 25 resin fl / m 2 The solids content of the resin primer can be between 20-50 wt%, preferably between 30 and 40 wt%, particularly preferably 35 wt%.

[0136] The usual auxiliaries such as hardeners, wetting agents (surfactants or mixtures thereof), release agents and / or further components are added to the urea-formaldehyde resin used for the primer. A composition of casein or soy protein as a binder and inorganic pigments, in particular inorganic color pigments, is preferably used as the color primer. White pigments such as titanium dioxide or other color pigments such as calcium carbonate, barium sulfate or carbonate can be used as color pigments in the primer layer. In addition to the color pigments and the casein or soy protein, the primer can also contain water as a solvent. It is also preferred if the applied pigmented base layer consists of at least one, preferably at least two, particularly preferably at least four, or up to seven successively applied layers or applications, wherein the application quantity between the layers or applications can vary.Applications can be the same or different. The application rate of the color primer is 5-10 g primer fl / m. 2 Application unit and layer. Intermediate drying is preferred after each application.

[0137] The amount of liquid first primer applied to the paint base coat is between 5 and 30 g / m 2 , preferably between 10 and 20 g / m 2 , particularly preferably between 10 and 15 g / m 2 . 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.

[0138] 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 printing ink is applied using a gravure or digital printing process, whereby the water-based pigmented printing ink can be applied in more than one layer, e.g. in the form of two to ten layers, preferably three to eight layers. The gravure printing process is a printing technique in which the elements to be reproduced are present as depressions in a printing form that is inked before printing. The printing ink is primarily located in the depressions and is transferred to the object to be printed, such as a wood fiber carrier board, due to the contact pressure of the printing form and adhesion forces. In contrast, with digital printing, the print image is transferred directly from a computer to a printing machine, such as a laser printer or inkjet printer.This eliminates the need for a static printing form. Both processes allow the use of water-based inks or UV-based colorants. It is also conceivable to combine the aforementioned printing techniques from gravure and digital printing. A suitable combination of printing techniques can be applied directly to the carrier board or the layer to be printed, or prior to printing by adapting the electronic data sets used. The markings required for alignment in the press are also printed along with the decoration.

[0139] The liquid second primer following the printed decoration is applied with a solids content between 40 and 60 wt%, preferably 45 and 55 wt%, particularly preferably 50 wt%. The amount of the second primer layer applied to the printed decoration can be between 10 and 40 g / m 2 , preferably 10-30 g / m 2 , 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.

[0140] In a further variant of the process, a film made of thermoplastic elastomer, in particular a film made of thermoplastic polyurethane, is used as the thermoplastic elastomer layer.

[0141] The thickness of the film, especially the TPU film, is between 50 and 150 μm, preferably 80 and 120 μm, especially 100 μm. Multiple films can also be used, which are either applied individually during compression or bonded together in a prior step.

[0142] To achieve desired properties, the thermoplastic film, such as TPU film, can be additionally coated with a lacquer, for example. This can positively influence its resistance to scratching, chemical exposure, abrasion, etc. A lacquer can also improve its performance with regard to static charge, soiling, etc. The lacquer can be applied during the film's production.

[0143] The TPU film used here can also contain abrasion-resistant particles, such as, for example, 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 the F180 to F240 classes, preferably F200 or F220, are preferably used. The grain size of the F180 class covers a range of 53-90 pm, F220 from 45-75 pm, F230 34-82 pm, and F240 28-70 pm (FEPA standard). The abrasion-resistant particles must not be too fine-grained (risk of dust formation), but also not too coarse-grained. The size of the abrasion-resistant particles thus represents a compromise. In another, more advanced variant of the process, a dispersion of a thermoplastic elastomer, in particular a dispersion of a thermoplastic polyurethane, is applied as the thermoplastic elastomer 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%, especially 40 wt%, is used. The application rate of the thermoplastic elastomer is between 50 and 150 g / m². 2 fl, preferably between 70 and 130 g / m 2 fl, particularly preferably between 90 and 110 g / m 2 fl, such as 100 g / m 2 fl,

[0144] As already described above, when applying a thermoplastic elastomer, especially TPII, the TPU layer can be coated with a lacquer layer after compression molding to increase abrasion resistance. For this purpose, a lacquer structure consisting of at least one lacquer layer and at least one topcoat, preferably a UV lacquer, is applied as a covering layer to improve scratch resistance. The topcoat can contain nanoparticles, e.g., silica. Solvent-based lacquers are not used. Otherwise, please refer to the above explanations.

[0145] As already mentioned above, a melamine-free counterlayer, particularly in the form of a layer of PF resin or PLF resin, is applied to the underside of the wood core board or wood-based panel. This counterbalances the tensile forces exerted by the layers applied to the top side of the wood-based panel.

[0146] In a preferred embodiment, the melamine-free counter-sheet is designed as a cellulose layer (paper layer) impregnated with PF resin or PLF resin or with urea-formaldehyde resin.

[0147] The PF resin or PLF resin as a melamine-free 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%, especially 50 wt%, is used. The application rate of the phenol-formaldehyde resin is between 30 and 100 g / m². 2 fl, preferably between 40 and 80 g / m 2 fl, particularly preferably between 50 and 70 g / m 2 fl, such as 60 g / m 2 fl, is.

[0148] As mentioned, the layered structures are pressed into a laminate in a single step under the influence of temperature and pressure in a short-cycle press or a continuously operating press. Typical short-cycle presses, for example, operate at a pressure of 30 to 60 kg / cm 2 , a temperature on the wood material surface of approximately 160 - 195 °C and a pressing time of 10 to 30 seconds.

[0149] Accordingly, the present process, in one variant, enables the provision of a melamine-free composite material with the following layer structure (from bottom to top):

[0150] Melamine-free backing, preferably made of PF resin or PLF resin - wood-based panel - at least one urea-formaldehyde resin primer - at least one layer of thermoplastic elastomer.

[0151] In a further variant, the present process enables the provision of a melamine-free composite material with the following layer structure (from bottom to top):

[0152] Melamine-free backing, preferably made of PF resin or PLF resin - wood-based panel - at least one urea-formaldehyde resin primer - at least one colored primer - at least one first primer layer - at least one decorative layer applied by direct printing - at least one second primer layer

[0153] - at least one film made of thermoplastic polyurethane.

[0154] In yet another variant, the present process enables the provision of a melamine-free composite material with the following layer structure (from bottom to top):

[0155] Melamine-free backing, preferably made of PF resin or PLF resin - wood-based panel - at least one urea-formaldehyde resin primer - at least one colored primer - at least one first primer layer - at least one decorative layer applied by direct printing - at least one second primer layer

[0156] - at least one layer of thermoplastic polyurethane - optional UV varnish.

[0157] The present invention is explained below using several examples.

[0158] Implementation example 1:

[0159] A decorative paper (paper weight: 80 g / m 2 ) is impregnated with a urea resin on an impregnation line. The impregnation channel runs at a speed of 60 m / min. The application rate is approximately 160 g / m 2 liquid, which corresponds to a solid application quantity of 80 g / m 2The impregnating resin contains the usual additives such as hardeners, wetting agents, etc. After impregnation, care must be taken to remove the decorative sheet sharply at the top and bottom using a squeegee. After intermediate drying to a residual moisture content of approximately 20% by weight, a TPU dispersion is applied to the top surface and a phenolic resin or polyurethane dispersion to the back surface using screens or rollers.

[0160] The PF resin or PLF resin or PU dispersion was used in an amount of 60 g / m 2 fl. (solids: 50 wt%).

[0161] The TPU dispersion was used in an amount of 100 g / m 2 (Solid content: 40 wt%).

[0162] The impregnated material 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).

[0163] The impregnated material is then pressed onto a 19 mm chipboard. 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 °C, and T (top / bottom) = 180°C. The surface was tested in accordance with DIN EN 14322: 2021 "Melamine-faced boards for indoor use." The values ​​required by the standard were achieved.

[0164] An HDF (format: 2800 x 2070 x 7 mm) is first primed with a urea-formaldehyde resin in a direct printing line operating at a speed of 80 m / min (application quantity: approx. 25 g urea-formaldehyde resin fl. / m 2 , Solids content: approx. 35 wt.%). The impregnating resin contains the usual additives such as hardeners, wetting agents, etc. The resin is dried in a circulating air dryer.

[0165] A primer consisting of titanium dioxide and casein is then applied. This primer is applied up to seven times, with a maximum application rate of 5–10 g of primer per coat. After each coat, intermediate drying is performed using a circulating air and / or IR dryer.

[0166] Then a primer is applied (application quantity 10 - 20 g fl / m 2 This is also dried. A decorative layer is then printed onto this primer using gravure or digital printing. The print is dried in a circulating air dryer.

[0167] An isocyanate-based primer is applied to the dried print (application quantity: approx. 20 g fl. / m 2 , solids content: approx. 50 wt% ).

[0168] The plates are then coated on top with a TPU film (film thickness: 100 μm) in a short-cycle press. The TPU film contains approximately 15 g of corundum per m².2 with a grain size of F200 according to FEPA standard.

[0169] On the back, the board is coated with a melamine-free backing layer, either in liquid form or as a sheet. A phenolic resin is used as the impregnating resin for the backing layer.

[0170] Then the structure is pressed in the short cycle press at T=160°C, p=40 kg / cm 2 and t=24 see. 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, fixed pieces and subsequently provided with a glueless profile. The surface was tested according to DIN EN 16511 - 2014: "Panels for floating installation - Semi-rigid, multi-layer modular flooring (MMF) with an abrasion-resistant top layer." The requirements of service class 31 were met. Some important tests are listed in the following table.

[0171] A decorative paper (paper weight: 80 g / m 2 ) is impregnated with a urea resin on an impregnation line. The impregnation channel runs at a speed of 60 m / min. The application rate is approximately 160 g / m 2 liquid, which corresponds to a solid application quantity of 80 g / m 2 The impregnating resin contains the usual additives such as hardeners, wetting agents, etc. After impregnation, care must be taken to remove the decal sheet sharply at the top and bottom using a squeegee.

[0172] 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 impregnated material using a sprinkler in an S-bend (30 g phenolic resin solid / m 2 ).

[0173] A TPU dispersion is applied to the top surface using a roller applicator. The TPU dispersion was applied in a quantity of 100 g / m 2(Solids content: 40 wt%). The impregnate is then dried to a residual moisture content of approximately 6 wt%.

[0174] It is then cut or cut into sheets (format: 2800 x 2070 mm). The impregnated material is then pressed onto a 19 mm chipboard. 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 °C, and T (top / bottom) = 180°C.

[0175] Implementation example 4:

[0176] A decorative paper (paper weight: 80 g / m 2 ) is impregnated with a urea resin on an impregnation line. The impregnation channel runs at a speed of 60 m / min. The application rate is approximately 160 g / m 2liquid, which corresponds to a solid application rate of 80 g / m2. The impregnating resin contains the usual additives such as hardeners, wetting agents, etc. After impregnation, care must be taken to remove the decal sheet sharply at the top and bottom using a squeegee.

[0177] After intermediate drying to a residual moisture content of approximately 20% by weight, a phenolic resin is applied to the back using screens or rollers.

[0178] The phenolic resin was used in an amount of 60 g / m 2 liquid (solids: 50 wt%) is applied. The impregnated material is then dried to a residual moisture content of approximately 6 wt%. It is then cut or cut into sheets (format: 2800 x 2070 mm).

[0179] The impregnated material is then pressed onto a 6 mm chipboard. 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 °C, and T (top / bottom) = 180°C.

[0180] An isocyanate-based primer is applied to the impregnated surface (application quantity: approx. 20 g fl. / m 2 , solids content: approx. 50 wt% ).

[0181] The board is then coated in a coating line with a UV or ESH coating in several layers with intermediate curing. The coating layer is applied in a quantity of 30 g / m 2The coating system can consist of at least one layer of EBC coating, which is then cured with an EBC blaster after application, and at least one topcoat, which is then cured with an excimer blaster after application. The entire coating system is then cured with an EBC blaster. The board is then cut into floorboards in a flooring line.

[0182] There are advantages

[0183] - Avoiding labeling

[0184] - Reaction to reclassification

Claims

Patent claims 1 . A method for producing a composite material free of melamine-formaldehyde resin comprising at least one carrier material, at least one polymer layer provided on the upper side of the carrier material and at least one resin-containing layer provided on the underside of the carrier material, comprising the steps: Providing at least one carrier material, - applying at least one layer of a urea-formaldehyde resin to the top of the carrier material, Application of at least one layer of a thermoplastic elastomer, in particular thermoplastic polyurethane, to the upper side of the carrier material, - applying at least one melamine-free resin-containing layer to the underside of the substrate, and - Drying and pressing the layer structure.

2. A process for producing a composite material free of melamine-formaldehyde resin comprising at least one carrier material, at least one lacquer layer provided on the upper side of the carrier material and at least one resin-containing layer provided on the underside of the carrier material, comprising the steps: Providing at least one carrier material, - applying at least one layer of a urea-formaldehyde resin to the carrier material, - applying at least one melamine-free resin-containing layer to the underside of the substrate, and - Drying and pressing the layer structure; - Applying at least one layer of varnish to the top of the pressed layer structure.

3. Method according to claim 1 or 2, characterized in that the at least one carrier material is a paper layer, preferably a decorative paper layer.

4. Method 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 / m 2 , preferably between 130 and 200 g / m 2 , particularly preferably between 150 and 180 g / m 2 amounts.

5. Method according to one of claims 1, 3-4, characterized in that a dispersion of a thermoplastic elastomer with a solids content between 20 and 60 wt%, preferably between 30 and 50 wt%, in particular 40 wt% is used and the application amount of the thermoplastic elastomer between 50 and 150 g / m 2 fl, preferably between 70 and 130 g / m 2 fl, particularly preferably between 90 and 110 g / m 2 fl, such as 100 g / m 2 fl, is.

6. Method according to one of the preceding claims, characterized in that a melamine-free adhesive layer in the form of a phenol-formaldehyde resin, a phenol-lignin-formaldehyde resin or a polyurethane is applied to the underside of the carrier material as the resin-containing layer.

7. The method according to claim 5, characterized in that the phenol-formaldehyde resin or phenol-lignin-formaldehyde resin or the polyurethane is applied to the underside of the carrier material, in particular the paper layer, as a liquid application or as a powder application.

8. Melamine-free composite material producible in a process according to one of claims 1 - 6, characterized by the following layer structure: optionally melamine-free adhesive layer - layer of a phenol-formaldehyde resin or phenol-lignin-formaldehyde resin - paper layer impregnated with urea-formaldehyde resin - layer of TPU - optionally varnish.

9. Melamine-free composite material according to claim 8, characterized by the following layer structure: Wood-based panel - melamine-free adhesive layer - layer of a phenol-formaldehyde resin or phenol-lignin-formaldehyde resin - paper layer impregnated with urea-formaldehyde resin - layer of TPU - optional varnish.

10. The method according to claim 1, characterized in that the at least one carrier material is a wood-based panel, preferably a medium-density fiber (MDF), high-density fiber (HDF) or chipboard, a plywood panel or a wood-plastic composite panel (WPC). 11 . Method according to claim 10, characterized by the following steps: Providing at least one wood-based panel as a carrier material, - applying at least one layer of a urea-formaldehyde resin to the top of the wood-based panel, - applying at least one layer of at least one thermoplastic elastomer; - applying at least one melamine-free countercoat, preferably in the form of a layer of a phenol-formaldehyde resin or phenol-lignin-formaldehyde resin, to the underside of the wood-based panel, and - Drying and pressing the layer structure.

12. Method according to claim 10, characterized by the following steps: Providing at least one wood-based panel as a carrier material, applying at least one layer of a urea-formaldehyde resin to the top side of the wood-based panel, - Application of at least one coat of primer; - Application of at least one first primer layer, - Applying a printed decoration; - Application of at least a second primer layer, - applying at least one layer of at least one thermoplastic elastomer; - applying at least one melamine-free countercoat, preferably in the form of a layer of a phenol-formaldehyde resin or phenol-lignin-formaldehyde resin, to the underside of the wood-based panel, and - Drying and pressing the layer structure.

13. Method according to one of claims 10-12, characterized in that a film made of thermoplastic polyurethane with a thickness between 50 - 150 pm, preferably 80 - 120 pm, in particular 100 pm, is used as the thermoplastic elastomer layer.

14. Melamine-free composite material producible in a process according to any one of claims 10-13, characterized by the following layer structure: Melamine-free backing, preferably made of phenol-formaldehyde resin or phenol-lignin-formaldehyde resin - wood-based panel - at least one urea-formaldehyde resin primer - at least one layer of thermoplastic elastomer.

15. Melamine-free composite material producible in a process according to any one of claims 10-13, characterized by the following layer structure: Melamine-free backing, preferably made of phenol-formaldehyde resin or phenol-lignin-formaldehyde 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 elastomer.

Images