METHOD FOR COATING A PLANAR WORKPIECE

Abstract

The invention relates to a method for coating a planar workpiece. In order to provide a planar workpiece, which is produced from a workpiece having lignocellulose fibers and a proportion of more than 50 wt % binding agent and optionally filler, with improved performance characteristics, a method is provided having the following steps: providing the planar workpiece, which has an upper face and a lower face and a lateral surface, applying a coating, applying a decoration, optionally structuring the coating, at least on a portion of an upper face, a lower face, or a lateral surface, in each case, and optionally curing the coating.

Description

BACKGROUND OF THE INVENTION

The invention relates to a method for coating a planar workpiece, a coated planar material, and the use of the coated planar workpiece.

Although planar workpieces can in principle also be used without a coating, for most use cases a coating is applied, both to increase the usability of the workpiece and to improve the aesthetic impression of the workpiece. The composition of the material of a planar workpiece determines how the workpiece can best be coated. A typical planar material is disclosed in US 2015/0017461 A1.

SUMMARY OF THE INVENTION

In the present case, the performance characteristics of a planar workpiece that has more than 50 wt % binding agent and furthermore lignocellulose fibers and optionally an aggregate are to be improved. This object is solved by the method as disclosed herein and by the planar workpiece disclosed herein. Surprisingly, it has been found that this planar workpiece can be coated using all known coating techniques.

The planar workpiece to be coated is produced from a material having lignocellulose fibers and binding agent as well as optionally an aggregate, wherein the proportion of the binding agent is at least 50 wt % (calculated as a solid). The binding agent proportion is also calculated in relation to the atro fiber proportion and can be from 101 wt % up to 500 wt % binding agent (in connection with this invention, atro means that the fiber proportion is dried at 105° C. to a constant weight). Such a material is described in EP patent application 19170159.8.

In particular melamine-formaldehyde resins, methylene diphenylisocyanate (MDI), also in emulsified form as eMDI, polymeric diphenylmethane diisocyanate (PMDI), and also phenol-formaldehyde resins to a limited extent due to the intensive coloring, or mixtures of the aforementioned binding agents are suitable as binding agents. The properties of the binding agent of the material, in particular melamine, can be modified, in particular improved through plasticizing, by adding elastomers or thermoplastics, for example, by adding polyvinyl acetate (PVAc) or ethylene vinyl acetate. Adding mono- or diethylene glycol are also suitable for plasticizing the planar material. Acrylate, styrene acrylate, or a polyurethane dispersion (PU dispersion) are preferably used for plasticizing the planar material, wherein their glass transition temperature is preferably below 0° C. (Tg<0° C.). These additives to the synthetic resin are used, measured as the weight of the solids proportion of the additive, in a ratio of maximally 1:1, preferably of up to 0.7:1, in particular of up to 0.2:1, advantageously of at least 0.1:1, proportionally in relation to the weight of the solids of the synthetic resin used. However, thermoplastics are preferably not used as the main component of the binding agent, especially not as the quantitative main component.

Natural or synthetic fibers, inorganic or organic fibers, or mixtures of fibers, in particular of the aforementioned fibers, can also be added to the material. The planar material can contain—in relation to the total amount of the material-up to 30 wt % aggregate, in particular non-hygroscopic or non-swelling aggregate. The aggregate can consist of mineral, ceramic, or synthetic material or glass. Mixtures of aggregates can also be used. The planar material can have a swelling in thickness of up to 3%, preferably of up to 2%, preferably of less than 1%, measured in each case in accordance with DIN 137 (swelling of the carrier board) or respectively DIN 13329 (edge swelling in a coated carrier board). Advantageously, a hydrophobing agent can be used, e.g., paraffin or wax, typically in amounts of up to 5 wt %, preferably in amounts of up to 2 wt %, usually in amounts of 0.1 wt % to 1.5 wt %, in each case in relation to the total weight of the planar material. Mixtures of hydrophobing agents can also be used. In addition, one or more algicides and/or fungicides can be added to the planar material, typically in an amount of up to 5 wt % in relation to the total weight of the planar material.

The planar workpiece has a thickness of 1 mm to 500 mm, usually between 3 mm and 80 mm. The material from which the planar workpiece is produced has a density of 1000 kg/m³ to 1800 kg/m³, usually between 1000 kg/m³ and 1600 kg/m³.

The material for the planar workpiece according to the invention can be produced on known systems for producing wood material boards. Fibers are glued, i.e., supplied with adhesive, scattered to form a fiber cake, and pressed under the effect of heat and pressure in a press that exerts pressure on the upper face and lower face of the planar material, for example in a double-belt press or in a short-cycle press, to form a planar material. Typical pressing conditions are temperatures of 140° C. to 220° C., usually 160° C. to 200° C., and a pressure of 0.3 N/mm² to 5.5 N/mm², preferably 1 N/mm² to 3 N/mm², usually with a pressing duration of 6 seconds/mm of board thickness to 20 seconds/mm of board thickness. The planar material can be produced in any size that the available presses enable.

In contrast to previously known planar workpieces, in particular those made of wood materials, the surface, meaning the upper face, the lower face, and the lateral surfaces of the workpiece, has significantly fewer fibers and instead predominantly cured binding agent due to the material used. It was not expected that previous coating methods could be used without difficulty for the new planar material. However, it has been found that it is possible to perform the method according to the invention for coating a planar workpiece, the material of which has lignocellulose fibers and a proportion of more than 50 wt % binding agent, wherein the method is performed with the steps of:

• • providing the planar workpiece that has an upper face and a lower face and a lateral surface,
  • applying a coating,
  • applying a decoration,
  • optionally structuring the coating, at least on a portion of an upper face, a lower face, or a lateral surface, and
  • optionally curing the coating.

It has been found that the surface of the workpiece, which consists mostly of cured binding agent, can be coated well. Coatings adhere well to the surface of the workpiece, which is formed mostly by synthetic resin. The components of the material from which the planar workpiece is produced, binding agent and fibers as well as optionally aggregate are also suited in particular for those coatings that are applied by means of a press under the application of pressure and high temperatures. However, painting and laminating (adhering films or papers) are also possible forms of the coating. The individual coating means and methods explained below can also be combined. The coating applied according to the invention can be a single layer or multiple layers, as explained in detail below. The coatings improve the performance characteristics of the planar workpiece considerably. They seal the surface of the workpiece, inter alia, against moisture, and design the workpiece preferably water-resistant as a result, they improve the maintenance characteristics, and they enable the aesthetic design of the surface of the workpiece.

The invention also relates to a planar material having lignocellulose fibers and more than 50 wt % binding agent, wherein the planar material has an upper face, a lower face, and a lateral surface, characterized in that the upper face, lower face, or lateral surface are at least in portions provided with a coating that has a decoration and optionally a structure. Depending on the design, the coating increases the usability of the workpiece according to the invention, for example in a physical regard (e.g., temperature and water resistance, scratch resistance, abrasion resistance, conductivity), in a chemical regard, e.g., through improved resistance to acids and alkalies, alternatively also in an aesthetic regard, for example through the application of attractive decorations and optionally structures.

For the aesthetic design of the surface of the workpiece, a decoration is applied, meaning a two-dimensional application consisting substantially at least of one, typically of two or more colors. Natural decorations such as imitation wood or stone, but also imaginative decorations are typical. Particularly simple decorations show a simple colored face. The decoration can either be directly applied, for example printed or sprayed or rolled, onto the surface of the workpiece according to the invention or respectively onto a coating applied thereto, for example a primer. Alternatively, the decoration can be printed onto a paper or a film, after which the printed paper or the printed film is applied to the surface of the planar workpiece, usually laminated on or, after it has been impregnated in synthetic resin and dried, pressed while curing the synthetic resin. The decoration is typically not wear-resistant and is therefore usually protected by a sealant, for example, made of synthetic resin, varnish, or hot melt.

In particular when the decoration imitates wood, but also in other decorations, introducing a structure intensifies the impression of a realistic image. The structure, in contrast to the decoration, is three-dimensional. It is typically spatially limited; it usually comprises the pores in, for example, wood decorations. The structure is usually introduced into a coating that is arranged above the decoration. The structure can be introduced as an indentation in this coating above the decoration; alternatively, the structure can be applied as a raised pattern on the decoration or respectively the coating above the decoration. The depth or respectively height of the structure is typically 1 m to 400 m, preferably 10 m to 100 m. Indentations are typically introduced by an embossing roller or an embossing sheet that are provided with corresponding raised patterns. Alternatively, indentations can also be applied as what are known as chemical pores by combining a wettable material and a non-wettable material, for example, by a first layer in which, in a matrix of wettable material, portions of non-wettable material are applied in each place where an indentation should be formed. Then, a second layer of material is applied that wets only the wettable material. The remaining portions of the non-wettable material then form indentations. Raised patterns are applied by printers or rollers that apply small amounts of coating material (varnish, ink, paint). It is particularly preferable when decoration and structure are applied synchronously. This means when, for example, pores that are applied in color in the decoration correspond to a structure. In this way, a wood decoration, for example, is imitated in a particularly natural manner.

Alternatively, a structure can also be applied independently of the decoration. Usually a matte effect or a surface is then desired that does not show fingerprints. Finally, a structure that is independent of the decoration and a structure that is synchronous with the decoration can also be combined.

The coating that is applied to the planar workpiece according to the method according to the invention can comprise, for example, a synthetic resin or a varnish. Melamine-formaldehyde resins are preferably used. Preferably, radiation-cured varnishes (electron beam-cured varnishes or UV-cured varnishes) are used as varnishes. Synthetic resin can be applied directly, for example in liquid form, wherein it is preferred to apply synthetic resin in multiple layers, advantageously a total amount of approx. 20 g/m² to 100 g/m² in, for example, 2 to 10 layers. As synthetic resin, for example, melamine-formaldehyde resin is applied. The synthetic resin usually has a solids content, i.e., proportion of the synthetic resin in the total amount of the synthetic resin, of 40% to 70%, preferably of 55% to 70%.

The synthetic resin can contain aggregates, for example corundum or glass or ceramic particles. These aggregates improve, for example, the abrasion or respectively scratch resistance of the surface of the workpiece according to the invention. Other aggregates such as graphite or metal particles or fibers improve the conductivity of the surface of the planar workpiece. The aggregates, which have a diameter of 1 m to 100 m, preferably of 5 jm to 90 m, in particular of 20 m to 70 m, alternatively, in the case of corundum, a grain of F180 to F240 according to the FEPA standard, are added to the synthetic resin in an amount of usually 5 g/m² to 100 g/m², advantageously of 10 g/m² to 60 g/m². In particular the aggregates that improve the scratch resistance and the abrasion resistance are preferably not contained in the outermost synthetic resin layer forming the outside of the coating.

The individual synthetic resin layers are advantageously dried in an intermediate step to a moisture content of 5% to 25%, preferably of 4% to 10%, for example by means of hot air or IR radiation. They then reach what is known as the B-state, in which the synthetic resins are usually no longer sticky but are still reactive. Then the completely applied synthetic resin coating is cured in a press, for example a short-cycle press, under the effect of pressure and increased temperature. Typical pressing conditions comprise a temperature of 160° C. to 220° C., preferably 180° C. to 200° C., a pressing pressure of 20 kg/cm² to 50 kg/cm², preferably 22 kg/cm² to 40 kg/cm², and a pressing time of 5 seconds to 60 seconds, preferably 5 seconds to 30 seconds.

The coating can be applied in the form of papers and/or in the form of films. In particular synthetic resin-impregnated papers in which the synthetic resin is dried but still reactive, meaning in the B-state, are readily used for coating the surface of the planar workpiece. In this embodiment, the synthetic resin is applied to a layer of paper, after which it is dried but not cured. This process is also referred to as impregnation. Impregnation can take place in multiple steps, optionally with intermediate drying of the already applied synthetic resin.

Different synthetic resins or mixtures of synthetic resins can also be applied in this case. The aggregates mentioned above can also be added here in the amounts and sizes mentioned above, in this case also preferably not in the synthetic resin layer that later forms the outside of the coating. In general, mixtures of liquid synthetic resin and synthetic resin in powder form can also be used, both for direct application to the planar workpiece and for the impregnation of paper. One or more synthetic resin-impregnated papers can be placed onto the surface of the planar workpiece. They are then pressed in a press, in particular a short-cycle press, with the planar workpiece, wherein the synthetic resin is first liquefied and then cured. The pressing conditions correspond to those that were mentioned above for curing a synthetic resin coating applied as a liquid.

The surface coating of the planar workpiece can be carried out solely with varnish; preferably in this case also in a multilayer application. Alternatively, varnish can also be applied to a synthetic resin coating, in particular to form the outside of a coating. Papers coated with varnish can also be used in which the varnish is dried or cured after being applied. Varnishes, but also synthetic resins, can be used in liquid form, but also as a solid, e.g., in the form of particles of a powdered varnish. Synthetic resin, e.g., melamine-formaldehyde resin, can also be used in the form of a powder. The powder is melted under the effect of pressure and increased temperature, typically flows to form a closed coating, and cures. Liquid varnish can be applied by spraying, rolling, and/or pouring. The workpiece can be painted on all sides (upper face, lower face, lateral surfaces); in particular, profiled surfaces can also be painted, for example those that are provided with a V-joint that is introduced into a side of the workpiece. Varnish can be used as non-pigmented or pigmented varnish. Varnish can comprise the aggregates mentioned in connection with the application of synthetic resin. Varnish can be used as transparent or opaque varnish. Varnish can be rolled on, poured, sprayed, printed, or be applied with a doctor knife. Varnish is applied to the surface of the workpiece according to the invention over the entire surface or on portions. Varnish is applied to the surface of a planar workpiece in an amount of 5 g/m² to 300 g/m², which also includes applying to an already existing coating or primer. Preferably, electron beam or UV-cured varnish is applied. It is also advantageous to partially set, meaning partially cure, an already applied layer of varnish during multilayer application of varnish before the next layer of varnish is applied. Then a multilayer coating with varnish is completely cured.

Another alternative for coating the surface of the planar workpiece according to the invention is the application of a hot melt, for example a polyurethane hot melt (PU hot melt), a polyester, polyamide, polyolefin, or polyacetate hot melt, for example ethylene vinyl acetate hot melt. Hot melts can be applied in a single layer or multiple layers, wherein the multi-layer application is preferred. Hot melts can have the same aggregates described above for the application of plastic. Hot melts can be used in non-pigmented or pigmented form, wherein the proportion of pigments can be up to 30 wt %. Hot melts can be transparent or opaque. A hot melt can be applied to the surface of the workpiece according to the invention over the entire surface or on portions. A hot melt is applied in an amount of 10 g/m² to 300 g/m², preferably in an amount of 50 g/m² to 200 g/m². A hot melt is fixed through cooling after the hot melt is applied at a temperature of 80° C. to 160° C., usually 100° C. to 130° C. A hot melt can be rolled on, be applied with a doctor knife, or sprayed on. An already applied and preferably already cooled layer of hot melt can be printed, in particular with water-based or UV-cured printing ink, to apply a decoration. A hot melt coating is also often combined with a varnish layer, usually with a final outer varnish layer, that forms the outside of the coated planar workpiece. A hot melt is also often used—as explained below—to fix other coating materials, in particular in combination with laminated materials such as continuous pressure laminate (CPL) or high-pressure laminate (HPL), or plastic films, for example polyvinyl chloride films (PVC films) or printed papers.

Finally, the usability of the surface of the workpiece according to the invention can be improved in that a lamination is applied. The lamination has a coating with a usually ready-to-use outside that is adhered to the material according to the invention, for example as described above, by means of a hot melt or by means of an adhesive. A typical embodiment of a lamination is a CPL or HPL that consists, for example, of a plurality of synthetic resin-impregnated papers, wherein the synthetic resin-impregnated papers or films have already been pressed together during the curing of the synthetic resin. However, PVC films can also be laminated. The CPL or HPL or also other coatings with a ready-to-use surface such as PVC film are typically applied to the surface of the planar workpiece with a hot melt as an adhesive. The lamination is pressed on, for example, at 80° C. to 200° C. in a laminating press at a pressure of up to 300 N/cm². The pressing duration is short and is usually a maximum of 1 second. Laminating systems are usually configured as calender systems.

Even if the surface of a lamination is already ready-to-use on its own, this does not preclude an additional coating or sealant from being applied, whether for aesthetic reasons or for additional improvement of the usability. For example, applying a varnish is one or more layers is typical, whether to achieve, for example, special visual effects or because, for example, at least one varnish layer contains corundum for the improvement of the abrasion resistance or, to improve the scratch resistance, aerosils.

It has also been found that the surface of the workpiece, which has mostly binding agent, in particular melamine, but in addition also lignocellulose fibers, can be printed well.

Printing can take place with analog means, for example with rollers, but it can also take place with digital means, for example with inkjet or laser printers. The surface of the workpiece coated at least in portions with printing ink can optionally be sealed by applying additional coatings. For example, a varnish applied in a single layer or multiple layers, a hot melt applied in a single layer or multiple layers, or a synthetic resin coating applied in a single layer or multiple layers, for example in the form of an overlay or a synthetic resin applied as a liquid, are suited for this purpose.

It has been found that coatings including the printing ink described above adhere well to the surface of the workpiece according to the invention. This does not preclude primer from being used to additionally optimize the adhesion. For example, a synthetic resin can be applied as a primer in order to improve the adhesion of additional layers of the same or different coatings. Furthermore, a primer can be used to make the coloring of the planar workpiece uniform. A pigmented synthetic resin, a pigmented varnish, or a pigmented hot melt, for example, can be used as a primer. If it is necessary in order to apply an additional coating or an additional layer of the coating, a primer can also be applied to an existing coating.

It has been found that a coating only on the upper or lower face of the planar workpiece leads to bending to a significantly lower degree than in the case of planar workpieces made of other materials, for example made of wood chipboard or wood fiber boards. Despite this, a single-sided coating in individual cases can lead to an undesired bending of the workpiece. To counteract this, or respectively to prevent such bending, a backing is preferably applied to the side of the workpiece opposite the coating. The backing can be the same, similar, or different than the coating. It is only essential that the backing at least partially compensates for the deformation forces that act upon the planar material due to the single-sided coating. Typically, the backing does not have any decoration or structure, although decoration and/or structure can certainly be applied just as in the case of the coating, in particular if, for example, both the upper and lower faces of the workpiece according to the invention are visible in later use.

According to another alternative, footstep sound insulation can be applied, in particular adhered or laminated on, in particular to the lower face of the workpiece. Paperboard or cardboard, for example, but also expanded polystyrene (EPS) are particularly well suited for use as a backing. When using paperboard or cardboard, it is preferred that these materials are made hydrophobic.

In a preferred embodiment, the workpiece according to the invention that is made of the material strengthened by the coating is divided into panels, wherein the workpiece or respectively the panels are provided with at least two machined, in particular profiled, edges that are facing each other. An advantageous edge profile is based on a tongue-and-groove profile but preferably additionally has portions that prevent pulling apart in the plane of the boards. However, the panels can also be connected to each other with adhesive or with connecting elements. A water-resistant connection between the panels is preferably chosen in order to obtain a water-resistant covering for wall, ceiling or floor or to design a water-resistant structure for indoor or outdoor construction, for example a facade.

The workpiece according to the invention that has been coated as above and optionally divided into panels can be used in a variety of ways, in particular when profiled edges are provided. Typical uses are floor, wall, and/or ceiling coverings, but also uses in outdoor construction as a structural or cladding element.

Insofar as features relating to the coating of a carrier board are explained in the context of this description, including the following exemplary embodiments, these individual features can be freely combined, independently of the disclosure in a specific context, as far as is technically possible, i.e., can also be used in other coatings of the carrier board.

DETAILED DESCRIPTION

Details of the invention are explained in greater detail below using exemplary embodiments.

In the following, if a carrier board is coated as the workpiece, a carrier board is always meant that consists of 54 wt % melamine resin and 45 wt % wood fibers as well as 1 wt % paraffin. Depending on need, a higher or lower proportion of binding agent can be used, for example a proportion of 51 wt %, 52 wt %, 56 wt %, 58 wt %, or 60 wt % binding agent. The proportion of paraffin always remains the same. The proportion of wood fibers is adapted to the proportion of the binding agent in each case. The carrier board has a thickness of 8 mm. The thickness, however, can be chosen between, for example, 4 mm and 12 mm without difficulty; in particular cases or respectively for particular uses, a smaller or larger thickness can also be chosen. A carrier board with a thickness of 4.5 mm is also particularly typical. The carrier board is produced by mixing binding agent and fibers, scattering a fiber cake, and pressing in a press, wherein, as is typical, pressing plates or circulating metal belts act upon the upper and lower faces of the fiber cake or respectively of the planar material under pressure and at an increased temperature. For the following experiments, the carrier board has a large size of 2800 mm×2070 mm. For the exemplary embodiments described below, the carrier board is used as an uncoated board.

Optionally, the carrier board can be sanded before the coating is applied. The sanding loss per side is 0.1 mm to 0.15 mm; the total sanding loss is therefore 0.1 mm to 0.3 mm of the original total board thickness.

Insofar as ranges are indicated in the following for an exemplary embodiment, for example for decorative raw paper, the number of printing inks, or the amount of the varnish, synthetic resin, or hot melt used, we note that the invention can be carried out over the entire indicated range. The indication of a range simply shows the flexibility of the method according to the invention, or respectively the variety of coating possibilities of the workpiece according to the invention. The same applies to the indication of alternatives, for example for applying printing ink or ink or for applying coatings.

Insofar as the use of synthetic resin is described in the following, typically a synthetic resin is used that contains or can contain the usual auxiliary substances such as hardening agents, wetting agents, etc., which typically amount to 1 wt % to 5 wt % of the total amount of synthetic resin used.

Exemplary Embodiment 1

Carrier Board Pressed with Paper Assembly

A decorative paper and an overlay are placed onto the upper face of the carrier board, an optionally used backing is placed under the lower face of the carrier board, and this pressed material stack made of three or respectively four layers is pressed in a short-cycle press. The overlay, decorative paper, and the optionally used backing are each used as synthetic resin-impregnated papers.

For exemplary embodiment 1, a decorative paper is used as the impregnated paper for coating the carrier board with a total weight of 110 to 200 g/m², based on

• • a decorative raw paper with a weight of 50 to 90 g/m², with
  • a decorative overprint with 1 to 6 colors, produced from pigmented inks that are applied in an analog manner, for example by means of a printing roller, and/or in a digital manner, for example by means of an inkjet printer. The inks are water-based so they can be dried with warm air after being applied, or the inks can be UV-cured and can be cured with UV radiation after being applied. Furthermore, to produce the decorative impregnated paper,
  • resin impregnation, performed before or after the printing, takes place on the basis of urea resin or melamine resin or a mix of the two resins, wherein the synthetic resin is applied as a liquid or as a solid, in particular in powder form. Then the synthetic resin is dried, but not yet cured, until it is present in state B with a weight of 60 g/m² to 110 g/m².

Furthermore, an overlay as an impregnated paper with a total weight of 120 to 400 g/m² is used as a coating, based on

• • a raw paper with a weight of 3 g/m² to 70 g/m², wherein light raw papers with a weight of 10 g/m² to 25 g/m² are preferably used,
  • a resin impregnation on the basis of melamine resin, which is applied in watery form or as a solid, in particular in powder form, and which is present after drying in state B, meaning not yet cured, with a weight of 85 g/m² to 280 g/m², and
  • a filling with corundum of specification F 180 to F 240 (according to the FEPA standard) in an amount of 5 g/m² to 50 g/m², preferably 10 g/m² to 15 g/m², wherein the corundum is either scattered or applied in a mixture with the synthetic resin.

Finally, a backing as an impregnated paper is optionally used with a total weight of 150 g/m² to 240 g/m², based on

• • a raw paper with a weight of 70 g/m² to 120 g/m²
  • a resin impregnation on the basis of urea resin and/or melamine resin or mixes of the two resins, which is applied in watery form or as a solid, in particular in powder form; present in state B with a weight of 80 to 120 g/m².

Alternatively or in addition to a backing, footstep sound insulation, for example, a layer of paperboard or cardboard or EPS, can be attached to the lower face of the carrier board, typically by laminating, meaning by adhering the footstep sound insulation by means of an adhesive.

The further production of the coating on the workpiece takes place in that a pressed material stack is produced that has, from top to bottom, the overlay as an impregnated paper, the decorative paper as an impregnated paper, the carrier board, and optionally the backing as an impregnated paper. The pressed product stack is pressed in a short-cycle hot press to form a laminate, wherein the short-cycle press has an upper pressing plate that acts on the overlay and a lower pressing plate that acts on the lower face of the carrier board or the backing, and wherein the short-cycle press is adjusted as follows:

• • under the effect of increased pressure of at least 25 kg/cm² and increased temperature of 180° C. to 220° C., preferably 200° C., measured at the pressing plate,
  • and a pressing time of 6 seconds to 30 seconds
  • while forming a surface structure by means of the upper pressing plate, which optionally has a structure that is adapted at least in portions to the decoration (known as “embossed in register”).

The coated carrier board produced in this manner is also dimensionally stable under the influence of water; it does not swell and it also shows no deformation in the face, meaning no bending or distortion.

Exemplary Embodiment 2

A single- or multilayer varnish layer can be applied to the overlay, into which a structure is embossed according to the coated workpiece according to exemplary embodiment 1, in particular in order to adjust surface properties such as gloss, high gloss, or matte effect of the surface or to create anti-fingerprint properties. The varnish is preferably applied as a UV varnish, usually in two to three layers, wherein preferably in the case of multilayer varnish application, the already applied layer is partially set after each varnish layer is applied. After the last varnish layer is applied, the varnish layers cure completely. The adhesion of the varnish layer on the overlay can optionally be improved in that a primer is applied to the overlay before the varnish is applied.

A typical example of a varnish application onto an overlay takes place, for example, by means of a water-based varnish, known as hydro varnish, for example a UV-curable acrylic varnish. A first layer of the varnish of 10 g/m² is applied to the surface of the overlay and partially sets. This layer acts as an adhesion agent between the synthetic resin of the overlay and the following varnish layers. To achieve, for example, a varnish coating with a total layer thickness of 50 g/m², a second layer with 28 g/m² of hydro varnish is applied to the first layer, followed by two additional layers with 5.5 g/m² of hydro varnish each. After each layer, the applied varnish can partially set; after all the layers have been applied, the applied varnish is cured completely. The varnish can be applied in any manner, by pouring, spraying, rolling, or with a doctor knife.

Preferably, the varnish layering is supplemented with corundum with a diameter of preferably 1 μm to 5 μm, usually in the last layer or in the last two layers, in order to improve the scratch resistance of the varnish surface. Corundum is preferably scattered into a not yet cured varnish layer. The decoration is thus further developed by the embossed structure and further protected by the coating of varnish.

This method for varnish application on synthetic resin surfaces is suitable, for example, for creating laminates of the use classes 23 to 34 according to EN 16511. Afterwards, the coated carrier board is split into rectangular panels with a length of 1000 to 2800 mm and a width of 90 to 500 mm. Connecting means of a tongue-and-groove type are worked in on the panels on four lateral surfaces, which are optionally equipped with locking elements, for the formation of locking profiles with which adjacent panels are placed and locked in the horizontal and vertical directions in a floating bond (known as click panels), wherein connecting means and/or locking elements consist of the core material of the carrier board and for this purpose are carved out of it or wherein the locking elements are carried out as separate elements into which the locking profile is introduced and which are attached to the lateral surfaces of the carrier board.

The coated carrier board, which is produced in this way as a laminate, is water-resistant and dimensionally stable. It can be used inter alia as a floor, wall, or ceiling covering, as a structural element for indoor construction, as a structural element for outdoor construction, in vehicle construction, or to design a facade.

Exemplary Embodiment 3

Carrier Board with Laminated-on Layer Made of PVC

A layer of PVC as coating is laminated onto a carrier board as described above. For this purpose, an adhesive is applied to the upper face of the carrier board, for example in an amount of 60 g/m² to 100 g/m². To fix the layer of PVC, all hot-melt adhesives can be used; however, a polyurethane-based, water-resistant hot-melt adhesive is preferred. A layer of PVC, the outside of which is provided with a decoration, is placed with the inside onto the adhesive on the carrier board. The layer of PVC is usually between 1 mm and 5 mm thick.

The stack made up of the carrier board, adhesive, and PVC layer is pressed in a laminating press under the application of pressure and usually increased temperature until the hot melt adhesive has substantially developed its adhesive power.

A carrier board coated with PVC can be used, for example, as a water-resistant panel for a floor covering, but also for structures in outdoor construction, for example for facades or structural elements such as dividers or privacy shielding walls.

Exemplary Embodiment 4

Carrier Board with Liquid Overlay Including Decorative Direct Printing

A workpiece, in this case a carrier board that is coated with liquid synthetic resin, is produced, wherein beforehand a primer is applied to the carrier board and a decoration is then applied onto this primer using direct printing. The direct printing is then covered with layers of synthetic resin applied as a liquid, wherein corundum is introduced into a non-outer layer. The carrier board coated in this way is cured in a short-cycle press (SC press). Specifically, the coating from exemplary embodiment 2 is applied as follows:

• • Priming the board with the aid of a melamine resin, a urea resin, or a mix of the two synthetic resins, applied in liquid form as a coating, in an amount of approx. 20 g/m² to 30 g/m² (solids content: melamine resin: approx. 65 wt %, urea resin: approx. 50 wt % of the total applied amount of synthetic resin). The application takes place using rollers.
  • Drying the resin with the aid of an air-circulating dryer or IR radiators to a moisture content of approx. 20%.
  • Repeatedly applying color primer (for example, mix of pigments and binding agent such as casein or corn protein) in liquid form in an amount of 5 g/m² to 10 g/m² each (solids content: approx. 50 wt %) with intermediate drying, for example by air circulation or IR radiators. The application of the color primer also takes place via roller application. The use of white pigments (titanium dioxide, calcium carbonate, barium sulfate) is preferred in this case.
  • Applying a liquid primer, for example an isocyanate primer, in an amount of approx. 10 g/m² to 20 g/m² to improve the adhesion of the layers to be subsequently applied. The primer is dried by air-circulating dryers or IR radiators. A roller application is used again here.
  • Printing a decoration onto the surface, the adhesion of which has been improved by the primer, either in an analog manner, for example by means of a roller, or in a digital manner, for example with an inkjet printer with water-based inks, then drying the ink by means of an air-circulating dryer, if necessary.
  • Applying a sealant as a coating by means of roller application, wherein the liquid sealant consists of melamine resin (solids content approx. 65 wt %) and glass spheres mixed into it (diameter of glass spheres: 70 μm bis 90 μm). The application amount is 20 g/m²-30 g/m². Then, the
  • drying, but not curing, of the synthetic resin takes place using air circulation or IR radiators until the B-state is reached, followed by cooling and interim storage.
  • Applying another coating made of liquid melamine resin in roller application in an amount of approx. 60 g/m² to 80 g/m² (solids content approx. 65 wt %) to the side of the board that is printed and already sealed by a layer of synthetic resin.
  • Scattering corundum onto the not dried liquid melamine resin with the aid of a scattering device. The corundum has a grain size of F180 to F240 according to the FEPA standard. The amount is between 10 g/m² and 50 g/m² of corundum, depending on the desired wear resistance.
  • Repeated application (preferably up to 5 layers) of a coating of melamine resin on the upper face of the board in an amount of 20 g/m² to 40 g/m² per layer, wherein the melamine resin has the solids content indicated above. During the application of the last layers, glass spheres (diameter: 70 μm bis 90 μm) are added to the resin. After each application, intermediate drying takes place with the aid of air circulation or IR radiators.
  • In parallel with the coatings on the upper face, the application of a liquid melamine resin as a backing can also take place on the back side of the board. This can take place in a part of the roller application plants and, for example, reach a total amount of 100 g/m² to 140 g/m². The melamine resin has the usual solids content indicated above. In addition, the synthetic resin can also contain dye or pigment. Intermediate drying is also to be performed in this case, either by means of air circulation or by means of IR radiators.
  • Then, the carrier board, coated on one or both sides, is pressed in a short-cycle hot press to form a laminate, as already described in exemplary embodiment 1,
    • under the effect of increased pressure of at least 25 kg/cm² and increased temperature of 200° C.
    • and a pressing time of 6 to 30 s
    • while forming a surface structure above the decoration; optionally adapted to each other, known as “embossed in register.”

If further machining of the coated carrier board is desired, this can take place in the same way as described in exemplary embodiment 1. The use of the coated carrier board or a panel produced from the coated carrier board can also take place in the same manner. The properties of the carrier board coated according to exemplary embodiment 4 are comparable to those of the coated carrier board according to exemplary embodiment 1.

For a carrier board with a coating according to this exemplary embodiment 4, a synthetic resin-impregnated paper can also be used as a backing instead of the synthetic resin applied as a liquid. Alternatively, a paperboard or a layer of EPS can also be fastened to the lower face of the carrier board by means of adhesive.

Exemplary Embodiment 5

Carrier Board with Hot Melt Cover Including Decorative Direct Printing

• • Applying a white-pigmented polyurethane hot melt (PU hot melt) to the carrier board (application amount: approx. 60 g/m² to 120 g/m²) in a liquid or respectively melted state as a coating. The hot melt is preferably applied in multiple layers of 5 g/m² to 20 g/m² each. The application takes place at a temperature of 120° C. as a liquid with the aid of a roller application plant onto the surface or upper face of the carrier board, which serves as the workpiece in this case. If necessary, the smoothing of the still liquid hot melt then takes place in a second application plant. The proportion of pigment in the PU formulation is approx. 20 wt %.
  • Cooling of the surface
  • According to a first alternative: Printing a white liquid color layer with a digital printer (application amount: 10 g/m² to 20 g/m²), then optionally drying the color layer, for example, with an infrared or air-circulating dryer.
  • Printing a decoration onto the surface with the aid of a digital printer using water-based or UV inks, then optionally drying the ink, for example, with a UV or air-circulating dryer.
  • According to a second alternative: Placing a decorative paper impregnated with cured synthetic resin or a decorative paper film onto the still liquid hot melt and activating the adhesive in a laminating press under the effect of pressure and in most cases also increased temperature until the desired adhesive power is achieved. Temperatures of 80° C. to 150° C. and a pressure of 150 N/cm² to 350 N/cm² are typical.
  • For both of the alternatives above: Applying another coating, in this case a non-pigmented, preferably transparent PU hot melt layer (application amount: 50 g/m²) with the aid of a roller application unit.
  • Optional: Scattering corundum particles into the hot melt (grain size: F180 to F240 according to the FEPA standard) with the aid of a scattering apparatus (application amount: between 10 g/m² and 50 g/m², depending on the desired abrasion resistance).
  • Application of another PU layer (application amount: approx. 30 g/m²) with a roller application unit.
  • Cooling of the surface.
  • Optional: Painting the surface with a UV varnish that contains approx. 30 g/m² of nanoparticles made of corundum to improve the scratch resistance (varnish application amount: 10 g/m² to 40 g/m²) with subsequent UV curing.

This coated carrier board can also be split into panels as described in exemplary embodiment 1 and provided with edge profiles. The use of the coated carrier board according to exemplary embodiment 5 and if applicable the panels produced therefrom is also described as in exemplary embodiment 1.

Exemplary Embodiment 6

Laminating on a Multilayer Plastic Film and Applying a UV Varnish

Coating a workpiece, in this case a carrier board, with a multilayer plastic film is described, the layers of which are connected to each other by adhesive or synthetic resin and which is connected to, for example, the upper face of the carrier board by an adhesive. The plastic film has a ready-to-use surface provided with a decoration. In addition, a UV varnish is applied as a sealant. On the opposite side of the carrier board, in this case the lower face, a backing is applied. The coated carrier board is produced by

• • Applying a PU hot melt to the lower face of the carrier board in an amount of approx. 100 g/m² with the aid of a roller application plant
  • Placing a backing consisting of a thin laminate, a multilayer plastic film, or a multilayer synthetic resin-impregnated paper onto the PU hot melt.
  • Pressing the backing in a laminating press. The laminating press, which is also used in the following laminating processes, is at temperatures of 80° C. to 160° C. and at a pressure of 150 N/cm² to 350 N/cm². The laminating can take place, for example, at approx. 120° C. at 300 N/cm² and a pressing duration of 0.8 seconds
  • Rotating the carrier board coated on the lower face
  • Applying approx. 100 g/m² of a PU hot melt as a coating to the upper face of the carrier board with the aid of a roller application plant
  • Applying a multilayer decorative plastic film or a multilayer synthetic resin-impregnated paper, which are in each case made from an inner core layer and an outer decorative film, in this case, however, without a wear layer as a coating on the layer of PU hot melt, which is applied to the upper face of the carrier board, then
  • Pressing the film in a laminating press, which is designed as a continuous press, within the pressing conditions mentioned above, in the present case approx. 120°, at 300 N/cm² and a pressing duration of 1 second,
  • Applying a coating made of multiple layers (usually 2 to 5 layers) of UV varnish, wherein the non-outer layers contain corundum to increase the wear resistance and nanoparticles (e.g., Aerosil) to increase the scratch resistance, wherein preferably the particles for increasing the scratch resistance are applied in a varnish layer that is closer to the outside of the coating.
  • Partially setting the individual varnish layers after each application and final curing after the last application with UV or EBH radiators, as already described above in other exemplary embodiments.

This coated carrier board can also be split into panels as described in exemplary embodiment 1 and provided with edge profiles. The use of the carrier board coated according to exemplary embodiment 6 and if applicable the panels produced therefrom is also described as in exemplary embodiment 1.

Exemplary Embodiment 7

Laminating on CPL/HPL

Exemplary embodiment 7 is similar to exemplary embodiment 6, but instead of the decoration, the decorative paper, or the decorative film as the coating, a thin laminate (CPL or HPL) provided with a decoration is applied to the workpiece, which has a wear layer. The coating can thus take place without the application of varnish. The following takes place:

• • Roller application of a PU hot melt in an amount of approx. 100 g/m² to the lower face of the board
  • Placing a backing consisting of a thin laminate, a plastic film, or a paper onto the lower face of the workpiece, in this case the carrier board
  • Pressing the backing in a laminating press, which can be adjusted as described above in exemplary embodiment 6, in this case a continuous press, at approx. 120° C., 300 N/cm² and a pressing duration of approx. 1 second
  • Rotating the carrier board
  • Roller application of a layer of a PU hot melt in an amount of 100 g/m² to the upper face of the board
  • Placing the CPL or HPL thin laminate provided with a decoration, which laminate meets, for example, the requirements of EN 13329 for the use classes 23 to 32
  • Pressing the assembly in the laminating press at approx. 120° C., a pressure of 300 N/cm², and a pressing duration of 1 second

If further machining of the workpiece, in this case the coated carrier board, is desired, this can take place in the same way as described in exemplary embodiment 1. The use of the coated carrier board or a panel produced from the coated carrier board can also take place in the same manner. The properties of the carrier board coated according to exemplary embodiment 7 are comparable to those of the coated carrier board according to exemplary embodiment 1.

Exemplary Embodiment 8

Carrier Board with Synthetic Resin Coating and Varnishing

Using a glue (e.g.: PVAc glue, urea-based glue, etc.), a decorative finish film is laminated onto the carrier board as a coating on the upper face and a backing is laminated onto the lower face. The finish film provided with a decoration has a paper weight of approx. 80 g/m² and bears a decorative printing, and the backing has a paper weight of approx. 60 g/m²; the finish film and backing are each impregnated with synthetic resin, for example melamine. To fix the finish film and the backing, in each case a glue amount of approx. 60 g/m² is applied to the carrier board in liquid form before the finish film or respectively the backing are placed.

The lamination takes place in a continuous press at a temperature of approx. 160° C., a speed of 20 m/min, and a pressure of 300 N/cm.

After the glue has cooled and hardened, a corundum-containing EBH varnish is applied to the finish film as a coating (EBH: electron beam hardening) in an amount of approx. 90 g/m² (corundum content: approx. 15 wt %). The varnish was partially set with a UV radiator. The EBH sanding base (application amount: approx. 80 g/m²) was then applied and partially set with an EBH radiator. After that, approx. 20 g of a topcoat filled with nanoparticles was applied as a coating to improve the scratch resistance. All applications took place with the aid of roller units. The complete assembly was then hardened with another EBH radiator.

The product met the requirements of DIN EN 14978 class 33.

Exemplary Embodiment 9

Carrier Board with a Varnish-Based Coating

A first prepreg is laminated onto a carrier board on the upper face. The first prepreg is a paper impregnated with transparent, tinted but still transparent, or semitransparent varnish or with colored, usually opaque varnish, which paper has been preimpregnated by drying or respectively curing the varnish. For laminating, first a hot melt is applied to the carrier board, then the first prepreg is placed, and then the carrier board and the first prepreg are guided through a laminating system that fixes the first prepreg to the carrier board by means of the hot melt with the conditions mentioned in exemplary embodiments 4 or 5. If tinted or colored varnish is used, the carrier board shows a uniform surface colored in the manner of a primer, on which a decoration applied over it is particularly well displayed.

Onto this carrier board provided with a prepreg, a second prepreg is placed as an additional coating, which also consists of a paper that is impregnated with a varnish and is optionally printed with a decoration. Optionally, a primer is applied in order to optimize the adhesion of the second prepreg on the first prepreg. A sanding base, for example, can be applied, meaning a varnish that allows an additional coating to be applied without sanding. The second prepreg is fixed to the first prepreg by laminating, in the same way as described for the first prepreg. Alternatively, the second prepreg can be fixed to the first prepreg by a solvent-containing adhesive.

An at least single-layer, preferably, however, multilayer varnish coating is now applied to the carrier board coated with the first and the second prepreg. Typically, two or three varnish layers are applied. Optionally, a primer can be applied to the second prepreg in order to improve the bonding of the varnish layer to the prepreg. Alternatively, the varnish introduced into the second prepreg and the subsequently applied varnish layer are matched to each other such that the varnish layer adheres well to the varnish of the second prepreg.

Optionally, footstep sound insulation is applied to the lower face of the carrier board.

Exemplary Embodiment 10

Carrier Board with Veneer

A carrier board according to the invention is coated either only on the upper face or on the upper and lower faces with a veneer made of oak. If a veneer is only applied to the upper face, a backing is advantageously applied to the lower face to prevent a deformation of the board.

An adhesive that fixes the veneer due to its adhering effect or a binding agent, in this case preferably a partially cross-linked binding agent, is introduced between the veneer and the carrier board.

The partially cross-linked binding agent is advantageously a synthetic resin, advantageously a thermosetting plastic, in particular an aminoplast; preferably, the binding agent has melamine resin, for example as melamine-formaldehyde resin. The binding agent can be used in an amount that is just sufficient to fix the veneer to the upper or respectively lower face of the carrier board. Preferably, the binding agent is used in excess so that the binding agent penetrates into the veneer, possibly penetrates through it. The binding agent can optionally be introduced in the form of a paper impregnated with binding agent. The paper can be symmetrically impregnated with binding agent or an excess of binding agent can be applied to at least one side of the paper. The binding agent is used to impregnate the paper in liquid form and is subsequently dried in a partially cross-linked state. It can alternatively also be used partially in a solid state, for example as powder or dust, that adheres to the still liquid, partially cross-linked binding agent that impregnates the paper. The binding agent can alternatively also be applied directly to the veneer or the upper or respectively lower face of the carrier board.

The veneer is fixed to the carrier board by means of a press. If adhesive is used to fix the veneer, a vacuum press, for example, that is known per se can be used for fixing.

If binding agent is used to fix the veneer, a short-cycle press, for example, can be used in which the synthetic resin is subsequently cross-linked at temperatures of 100° C. to 240° C. and a pressure of 25 N/mm² to 50 N/mm² within 20 seconds to 60 seconds so that it is cured.

In this case, the synthetic resin, which is liquid during the cross-linking, penetrates at least partially into the veneer; optionally, in particular if an excess of binding agent is used, the binding agent penetrates through the veneer at least in portions. According to a preferred alternative, so much excess binding agent is used that the synthetic resin completely penetrates through the veneer and forms the outer surface of the coating of the carrier board. At the mentioned pressure, the veneer is typically also compressed. When a binding agent is used, the veneer is more pressure-resistant after the pressing and offers a less delicate surface than a non-compressed veneer.

In the same way as a binding agent, a polyurethane prepolymer (PU prepolymer) can alternatively be used for direct application onto the surface of the carrier board or the veneer. By curing the PU prepolymer to form a polyurethane, the veneer is bound to the carrier board. Due to the improved light fastness in comparison to aromatic isocyanates, an aliphatic isocyanate is preferred as the polyurethane prepolymer; if yellowing or discoloration is not a concern, an aromatic isocyanate can also be used as the polyurethane prepolymer. The veneer and the carrier board can be pressed together under the pressing conditions mentioned above for the binding agent, for example in a short-cycle press.

An additive can be applied to the surface of the binding agent facing the veneer. The additive can influence, for example, color, conductivity, or light fastness. Additives can also be used in combination with each other. If the additive is applied to the surface of the binding agent, the additive is conveyed through the veneer during the cross-linking in the press by the then liquefied binding agent to the degree that the binding agent penetrates through the veneer. In this way, a maximum effect is achieved with low use of additive.

The carrier board that is coated in this way with a veneer can be coated further, in particular be sealed against the influence of moisture, for example the veneer can be painted.

If the binding agent forms the surface of the veneered carrier board or if a sealant is subsequently applied to protect against moisture, then the water-resistant carrier board can be used with a decorative, still water-resistant coating in damp rooms, for example as a floor covering or for furniture, in particular bathroom or kitchen furniture, or to equip saunas or swimming pools.

Claims

1. A method for coating a planar workpiece, wherein the planar workpiece is produced from a material having lignocellulose fibers and a proportion of more than 50 wt % melamine-formaldehyde resins, phenol-formaldehyde resins, methylene diphenylisocyanate (MDI), also in emulsified form as eMDI, polymeric diphenylmethane diisocyanate (PMDI), or mixtures of the aforementioned binding agents, comprising the steps of:

providing the planar workpiece, which has an upper face and a lower face and lateral surfaces,

applying a coating, and

applying a decoration.

2. The method according to claim 1, wherein the coating is selected from the group consisting of heat-curable synthetic resins, varnishes, and hot melt.

3. The method according to claim 1, wherein the coating is applied as a liquid coating, as a particulate coating, in the form of papers, and/or in the form of films.

4. The method according to claim 1, wherein the coating is a single layer or multiple layers.

5. The method according to claim 1, wherein the coating is cured under the effect of pressure and/or temperature.

6. The method according to claim 1, wherein the coating is cured by radiation.

7. The method according to claim 1, wherein the structuring is created by mechanical or chemical means.

8. The method according to claim 1, wherein the coating is provided with aggregates.

9. A planar workpiece, produced from a material having lignocellulose fibers and more than 50 wt % melamine-formaldehyde resins, phenol-formaldehyde resins, methylene diphenylisocyanate (MDI), also in emulsified form as eMDI, polymeric diphenylmethane diisocyanate (PMDI), or mixtures of the aforementioned binding agents, wherein the planar workpiece has an upper face, a lower face, and lateral surfaces, wherein the upper face, lower face, or at least one lateral surface are at least in portions provided with a coating that have a decoration.

10. The planar workpiece according to claim 9, wherein a primer is applied between the workpiece and the coating or to a coating.

11. The planar workpiece according to claim 9, wherein an adhesive is applied between the workpiece and the coating.

12. The planar workpiece according to claim 4, wherein at least two lateral surfaces that are facing each other have a profile.

13. A use of the planar workpiece with a coating according to claim 9, as a floor covering, wall covering, ceiling covering.

14. The method according to claim 1, further comprising the step of structuring the coating, at least on a portion of an upper face, a lower face, or a lateral surface.

15. The method according to claim 1, further comprising the step of curing the coating.

16. The method according to claim 6, wherein the radiation is electron curing radiation or UV radiation.

17. The planar workpiece according to claim 9, wherein the coating has a structure.