EP0216269B1 - Decorative panel with improved surface properties - Google Patents

Abstract

A decorative panel and method therefor. The decorative panel includes a core layer and layers which are decorated on one or both sides of the core layer. At least the outermost layer of the panel on at least one of the two surfaces of the panel is predominantly composed of a synthetic resin which can be one or more components polymerized by radiation and includes unsaturated acrylates and methacrylates. This layer is scratch-resistant at a scratch loading of at least 1.5N, preferably 2-7N (DIN 53,799, part 10) and has a low gloss corresponding to a reflectometer value of not more than 50 at an angle of incidence of 85 DEG (DIN 67,350).

Description

The invention relates to a decorative panel, composed of a core layer and a decorative layer on one or both sides, and to a method for the production thereof. Panels of this type are used for indoor or outdoor applications in the construction sector, depending on their thickness they are used as cladding panels or as self-supporting elements.

The previously used decorative panels are, for example, decorative laminated panels (DIN 16 926), so-called "high pressure laminates" (HPL panels). They consist of a heat-pressed stack of resin-soaked paper webs as the core layer and a top layer of resin-soaked decorative paper. These plates have the disadvantage that they are attacked by mineral acids, in particular at concentrations above 10% and an exposure time of longer than 10 minutes. In addition, these standard panels are not sufficiently weather-resistant because the type of resin used in the top layer is sensitive to hydrolysis. Plates of this type can therefore only be used to a limited extent as worktops in chemical laboratories or for the production of wet cells which have to be cleaned with acids. When used outdoors, additional complex measures are required to improve their resistance to weather influences.

Laminates and sheets based on plastics such as polyester or acrylate sheets, on the other hand, are particularly scratch-sensitive and not sufficiently resistant to organic solvents. For this reason, they are also less suitable for these applications.

DE-A-30 10 060 describes a multilayer plate which has a lacquer surface, the lacquer surface consisting of a lacquer which can be hardened by electron beams. Slabs with matt surfaces are not described.

A decorative plate which is particularly suitable for exterior applications, for interior fitting and for the production of special furniture, the surface of which is not sensitive to hydrolysis and has sufficient resistance to weathering influences, mineral acids and organic solvents and high surface hardness, is the subject of the unpublished EP application 85105851.1 (EP-A -0 166 153). It is made up of a core layer and a decorative layer on one or both sides. At least the outermost layer of the plate on at least one of the two plate surfaces consists predominantly of a synthetic resin composed of one or more components polymerized by radiation, selected from the group of unsaturated acrylates and methacrylates. This layer shows a particularly high surface hardness. It is still scratch-resistant at a scratching stress of at least 1.5 H, preferably 2 to 7 H (DIN 53 799, part 10). In the process to produce this plate, a liquid surface layer, which comprises the radiation-polymerizable components, is applied to a base and then polymerized by radiation. Only after a further step in which the surface layer polymerized by radiation is pressed together with the base at elevated temperature. the plate surface shows the required properties.

However, this decorative plate shows the often undesirable property of being more or less shiny. If structured separation media are used in the final heat pressing, the plate surface can have a structure structured according to the surface of the separation medium, for example an orange peel-like surface structure, but its surface gloss is still very high. The addition of known matting agents such as silicon dioxide pigments in the outermost surface layer of the plate practically does not reduce the gloss, because the pigment-matt surface, which was initially silk-matt after the radiation polymerization, strangely shines again as soon as the plate is subsequently subjected to heat compression.

It is therefore an object of the invention to provide a weather-resistant, acid and solvent-resistant decorative panel which has a high surface hardness and only a low surface gloss.

This object is achieved by the plate specified in claim 1 and by the method for its production with the features mentioned in claim 6; the subclaims relate to special embodiments of the plate or further developments of the method. The plate is a flat body, its surface shape and Surface structure is adapted to the application and can, for example, also have a curved shape. A plate in the sense of the invention is also to be understood as films.

When measuring the scratch resistance according to DIN 53799, Part 10, the force with which a diamond needle creates a visible scratch on the plate surface is determined. This assessment is carried out immediately after the action of the diamond needle, since the surface layer can be gradually reset due to the elasticity of the surface layer after the scratching. The scratch resistance is a measure of the surface hardness.

Surprisingly, it was found that this decorative plate with the special synthetic resin layer polymerized by radiation on at least one of the outer surfaces not only has excellent weather resistance compared to the previously known plates, but surprisingly has an increased surface hardness. It is also much less sensitive to acids and organic solvents.

The reflectometer value is used as a measure of the gloss of the plate surface with a reflectometer type RB / Dr. Determined for a long time according to DIN 67 530. A reflectometer value determined according to this standard represents an optical parameter for the surface of a test specimen which is related to the gloss of the surface. It is to take into account that the gloss is not a purely physical, but also a physiologically and psychologically related variable. A direct measurement of the gloss is therefore not possible, but the "glossiness", namely the proportion which the surface contributes to the appearance of the gloss due to its reflective properties, can in principle be measured in a suitable manner. The reflectometer value can be used as a measure of the gloss, because it is essentially determined by the reflective properties of the surface.

The reflectometer system defined by this standard is based on the arrangements described in the ASTM D 523-67 standard. The radiation angles 20 °, 60 ° and 85 ° are chosen arbitrarily.

The 20 ° measuring geometry is used for test specimens with a 60 ° reflectometer value above 70, the 85 ° measuring geometry for test specimens with a 60 ° reflectometer value below 30.

In the reflectometer, a light source is imaged centrally in the opening of an aperture. The light rays hit the surface of the plate at the specified angle of incidence (20 °, 60 ° or 85 °) and are reflected in a scattered manner. The luminous flux passing through the aperture is measured with a photoelectronic receiver located behind the aperture.

The core layer has the supporting function of the plate. they is made of wood, for example. Sheets or foils made of plastic, for example based on polyvinyl chloride, polyethylene and polystyrene, or made of metal, for example made of steel, aluminum, copper, brass or other alloys, are also suitable as the core layer. The radiation-polymerized synthetic resin layer is located directly on the surface of these core layers or is connected to the core layer by means of glue films or glue joints, but preferably with adhesion-promoting synthetic resins such as phenol-formaldehyde or resorcinol-formaldehyde precondensate. Glue joints are pure adhesive layers, glue films are carrier layers that are coated or soaked with adhesive. Adhesion promoters are substances that, without being adhesive themselves, promote the connection of two different types of material.

The core layer can also consist of the sheets of paper, in particular sodium kraft paper, impregnated with heat-curable synthetic resin, in particular phenol-formaldehyde resin, which are customary in H.P.L. plates and are pressed in the heat. Depending on the desired plate thickness, 1 to about 100 sheets are superimposed in the heat.

The core layer can also consist of pressure-hardened nonwoven or mats made of mineral fibers, glass fibers, plastic fibers or a fiber mixture, but preferably made of cellulose. Cellulose-containing fiber layers are, for example, tangled wood fibers or wood chips. The nonwoven, or mat, made of wood and / or cellulose fibers is produced by applying a synthetic resin to the fibers, drying the resin-coated fibers, shaping a fiber mat and pre-compressing this mat under the action of pressure (EP-A-0 081 147) .

On the outer surface (s) of this fiber-containing core layer there is possibly an underlay which contains a thermosetting aminoplast or phenoplast resin. This layer consists e.g. from a pigmented or unpigmented nonwoven or paper.

In a preferred embodiment, the fiber-containing core layer or this underlay layer is followed directly by a radiation-polymerized synthetic resin layer which is decorative, i.e. shows special optical effect or decorative effect by added dyes. A clear, i.e. transparent and dye-free, radiation-polymerized synthetic resin layer, which forms the outermost surface (s) of the plate; however, it is entirely possible to omit this clear synthetic resin layer, so that the decorative synthetic resin layer (s) then form (s) the outermost layer (s).

Instead of the decorative synthetic resin layer, a decorative layer based on a colored and / or printed plastic film or based on paper can also be used are, which usually consists of a pigmented, colored and / or printed decorative paper. The synthetic resin layer polymerized by radiation, in this case transparent and dye-free, is located on the plastic film or the decorative paper. For this purpose, the decorative paper contains the usual thermosetting synthetic resin, in particular aminoplast resin, and is located on core layers, which are made up of the sodium kraft paper typical of HPL boards or of phenol-resinous, tangled wood or cellulose fibers.

The compounds provided for the production of the uppermost layer of resin polymerized by radiation comprise acrylic acid esters or methacrylic acid esters which are radically polymerizable by actinic radiation and which are present individually or together in a polymerizable mixture. The preferred component is a polyfunctional, ie polyunsaturated, prepolymer. In addition to this predominant component, a further component with a diluting effect is optionally present in the copolymerizable mixture, which component is referred to as the dilution monomer or dilution oligomer. In a mixture, the polyfunctional prepolymer has a proportion of 50 to 100, in particular 60 to 90,% by weight of the total weight of the copolymerizable components. Low viscosity prepolymers (less than 100 poise at 20 ° C) are used without the thinning monomers or oligomers.

The components used have a strong tendency to polymerize radically when exposed to actinic radiation. Close UV light or high-energy radiation comes as actinic radiation, e.g. Electron-corpuscular or X-ray radiation into consideration. The free-radically polymerizable prepolymer is a polyfunctional unsaturated aliphatic or aromatic acrylate or methacrylate, preferably an unsaturated polyester acrylate oligomer, but in particular an aliphatic urethane acrylate oligomer. Aromatic urethane acrylate oligomers also lead to scratch-resistant surface layers, but yellow after a while in outdoor applications.

In addition to the prepolymer, a mono-, di-, tri-, tetra-, penta- or hexaacrylate or -methacrylate, but preferably a di- or triacrylate, is used in the free-radically copolymerizable mixture as an additional suitable monomer or oligomer. These mono- to hexaacrylates or methacrylates are esters of polyols with 1 to 6 OH groups with acrylic acid or methacrylic acid and are therefore also referred to as polyol acrylates or polyol methacrylates. Suitable diacrylates are esters of acrylic acid with aliphatic, dihydric alcohols, in particular ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, butanediols, 1,6-hexanediol or neopentyl glycol, with aliphatic ether alcohols, in particular diethylene glycol, dipropylene glycol, dibutylene glycol, polyethylene or polyethylene Polypropylene glycols, with oxyalkylated compounds of the aforementioned aliphatic Alcohols and ether alcohols or also with aromatic dihydroxyl compounds, in particular bisphenol A, pyrocatechol, resorcinol, hydroquinone, p-xylylene glycol or p-hydroxybenzyl alcohol. Preferred diacrylates are 1,6-hexanediol diacrylate, tripropylene glycol diacrylate and 1,4-butanediol diacrylate. Preferred triacrylates are trimethylolpropane triacrylate and pentaerythritol triacrylate.

In addition to the urethane acrylate and unsaturated polyester acrylate oligomers already mentioned, suitable polyfunctional prepolymers are also epoxy acrylate and silicone acrylate oligomers, which are preferably used in the free-radically copolymerizable mixture with the diacrylates or triacrylates mentioned.

The prepolymers are known compounds and are produced, for example, from hydroxylated copolymers in which the hydroxyl groups are randomly distributed along the copolymer chain. Statistically unsaturated acrylic copolymers are obtained from this copolymer by esterification of the hydroxyl groups with acrylic acid. To produce semi-terminal unsaturated acrylic copolymers, the hydroxyl group is attached to the end of the chain in the preparation of the hydroxylated copolymer. Urethane acrylate oligomers are produced by reacting (meth) acrylic acid esters containing hydroxy groups, for example hydroxyethyl methacrylate, with polyvalent isocyanates, preferably diisocyanates. The di- or polyisocyanates can preferably be reaction products of diols, polyether diols or polyester diols with a stoichiometric excess of monomeric di- or polyisocyanate.

If the polyfunctional prepolymer predominates in the polymerizable mixture, the chemical nature of the base polymer determines the properties of the hardened surface layer. The added mono- to hexaacrylate or methacrylate, as the diluting monomer or oligomer, allows the viscosity of the mixture to be cured to be adjusted, which is normally in a viscosity range from 20 to 100 poise (20 ° C.), and fully takes on the radical polymerization part. During the irradiation, the coating is cured by radical polymerization between the double bonds of the prepolymer and the dilution monomers or oligomers which may be present.

When curing under the action of actinic radiation, photoinitiators must be added which absorb UV light and facilitate the initiation of radical polymerization with the formation of radicals. On the other hand, no photoinitiators are required when curing with electron beams. Most photoinitiators contain at least one carbonyl group that is conjugated to an aromatic ring. A photoinitiator system consisting of several components is usually used.

In addition, the radiation-polymerized synthetic resin contains, if necessary, to achieve the desired decorative, mechanical and physical surface properties suitable additives such as plasticizers, fillers, dye pigments, agents to improve the abrasion resistance and stabilizers. These substances include, for example, barium sulfate, silica, aluminum oxide and light-stable pigments.

To produce the decorative panel, the liquid compounds polymerizable by radiation are applied to the substrate to be coated, e.g. by spraying, pouring, a doctor blade system, a roller or screen printing. The applied layer, when applied to a decorative layer, is transparent. But it can also be decorative itself and is then colored and is on a non-decorative paper layer or directly on the core layer. In a further embodiment, an additional layer, which can be polymerized by radiation, is applied to this decorative synthetic resin layer after radiation curing, but is not decorative but transparent.

The base used for the application of the compounds polymerizable by radiation is thus a paper layer, a decorative paper layer or the above-mentioned core layers based on wood, plastic, metal or a stack of further fiber-containing layers, which forms the core of the plate obtained later. The fibrous layers of the stack, which are preferably made of sodium kraft paper or a Nonwovens made of wood and / or cellulose fibers contain the heat-curable pre-hardened resins that are customary in HPL boards, in particular phenol-formaldehyde resins, while the papers which may additionally be present on the stack contain an aminoplast resin, but in particular a phenoplast resin . The content of thermosetting resins is 20 to 250 wt .-%, based on the respective layer.

The fiber-containing layers or the paper layers are impregnated or impregnated, for example, by immersion in a bath with a solution or dispersion containing the thermosetting resin or by application or spraying on using a metering system. Depending on the synthetic resin used, the solvent or dispersant is aqueous-alcoholic, aqueous-acetone or aqueous. It can also contain up to 20% by weight of flame retardant. The distribution of the desired amount of resin is then carried out by stripping or squeezing, e.g. with rollers.

Before the compounds polymerizable by radiation are applied to the intended base, the thermosetting resins of the base are precured and dried as usual.

During the radiation polymerization, the outermost, still liquid layer is made of radiation-polymerizable compounds with a film or plate made of plastic or paper or a composite film various plastic layers or plastic and paper layers with a rough surface structure, which must be sufficiently permeable to actinic radiation. The film or plate provided for covering must not have a highly porous surface, since otherwise there is a risk that the liquid compounds which can still be polymerized by radiation penetrate into the surface. In this case, the film or plate can no longer be removed after the polymerization. This outermost liquid layer can itself be decorative and contain a dye or non-decorative, that is to say transparent, and can then be located on a decorative layer or on a decorative synthetic resin layer polymerized by radiation. Films with a thickness of up to 0.1 mm are preferably used, since thicker covers for electron beams or UV rays do not have sufficient permeability or require relatively long exposure times. In general, foils with a thickness of 20 to 60 μm are used, since on the one hand they are sufficiently transparent to the radiation and on the other hand they also have sufficient mechanical strength. For the sake of simplicity, the following is referred to as foils or cover foils.

The plastic film consists in particular of a polyester or polypropylene film oriented by biaxial stretching. The rough structure of the film provided for covering is produced, for example, by adding pigments, at least in the vicinity of its outer surface. This surface roughness is due to Elevations in the film surface, the height of which, however, is only small in comparison to the film thickness and is in the range of a maximum of a few micrometers. The pigments consist, for example, of inorganic particles, in particular of aluminum oxide, aluminum sulfate, barium sulfate, calcium carbonate, magnesium carbonate, kaolin, talc, silicon dioxide, titanium dioxide or microglass beads, or organic plastic particles which are incompatible with the plastic of the film and are dispersed in the film in particulate form. The pigments usually have a particle size of 0.1 to 20 μm, the average particle size being in the range of 0.1 to 4 μm. Their concentration is 0.01 to 10% by weight, based on the film weight. The concentration of the pigments in the film and their size is set depending on the desired surface roughness of the plastic film.

The cover film is applied to the liquid layer which can still be polymerized by radiation by first applying this liquid layer to the base in the manner described above and then providing it with the cover film, the rough surface side of the cover film having the liquid, polymerisable layer Layer comes into contact. However, it is also possible to first apply the liquid polymerizable layer to the rough surface side of the cover film and then to apply the cover film with this liquid layer to the base.

The roughness of the surface is reflected on the surface of the transferred by radiation to the layer to be polymerized, which then adopts the surface structure of the cover film and receives a matt surface. This result is all the more surprising since the surface gloss of the end product can practically no longer be reduced by using structured separating media during the final pressing.

A common source of free radical formation, such as e.g. a photoinitiator, or just heat is applied. If the photopolymerizable layer contains photoinitiators, the polymerization is initiated as it passes under mercury vapor lamps. The absence of oxygen is not required for curing with UV radiation. The electron beams used to harden the polymerizable compounds expediently have an energy corresponding to 150 to 350 KeV. The energy of the electron accelerator is determined by the thickness of the synthetic resin layer to be formed, the necessary radiation dose and the duration of exposure or the speed at which it is carried out.

The devices used to accelerate the electron beams are commercially available. These are the accelerators known as "scanner type" and "linear cathode type". By interacting with the components of the polymerizable layer, free radicals are formed. This curing process is usually carried out at room temperature. Also for curing by means of electron beams, it is not necessary for this process to take place in an inert, ie largely oxygen-free, atmosphere, since the polymerizable surface layer is protected by the plastic film lying thereon.

After the polymerization caused by radiation, the cover film can be removed. However, the cover film can also only be removed after the process has ended, i.e. after heat pressing, remove or use as a covering of the finished plate. If they are sufficiently flexible, the documents are wound up for storage or cut to the desired format. If the base comprising the radiation-polymerized resin consists only of a paper layer, it is placed on a stack of fiber-containing layers forming the core layer. It is also possible to additionally provide the lower side of the stack with such a base.

The resulting layer package of fiber-containing core layer and radiation-polymerized surface layer (s) and, if necessary, intermediate layers of paper or decorative paper is, as is customary in the production of HPL plates, pressed into a decorative plate in the heat, the thermosetting resins being cured . The temperature is preferably 120 to 210 ° C, the pressure in the range of 10 to 100 bar and the exposure time is 1 to 30 minutes.

If the core layer consists of a wooden, plastic or metal plate, the temperature and pressure can usually be reduced to values of 80 ° C and 5 bar.

The pressing takes place in a known stationary, continuous or continuous pressing device. The number and the thickness of the fiber-containing layers of the core layer or the thickness of the core layer is selected depending on the use of the plate, with plate thicknesses of 3 to 25 mm being required for external applications depending on the intended use. If a large number of plates, which have radiation-polymerized synthetic resin layers, are stacked on top of one another in the press, which is economically advantageous when the core layer is thin, the individual plates are separated from one another by a separating medium. The separation medium is e.g. a layer of paper, plastic film or metal plate. If the separation medium has a rough surface structure, i.e. Elevations or depressions, the rough outer structure of the respective plate is given this rough structure, while the existing matt fine structure is retained. The degree of gloss of the plate surface already determined by the radiation process can practically no longer be changed by the separating medium.

The decorative panels produced are surprisingly particularly weather-resistant and extremely scratch-resistant, which may be unpredictable Interaction between the different resins or maybe also based on a post-crosslinking of the free-radically polymerizable compounds during the heat pressing. The scratch resistance and chemical resistance is surprisingly much higher than in the case of a plate which is coated with the same compounds which can be polymerized by radiation and whose coating - without the heat compression - has only been radically polymerized by radiation. In addition, the plate surface shows a greatly reduced gloss, which cannot be achieved even when matting agents are used in the surface layer.

The invention is illustrated by FIGS. 1 to 4 and the following examples. The percentages are percentages by weight.

Fig. 1

den Ablauf der im Beispiel 1 beschriebenen Verfahrensvariante,

Fig. 1a

einen Teilquerschnitt durch eine Platte gemäß Fig.1,

Fig. 2

den Ablauf der im Beispiel 2 beschriebenen Verfahrensvariante,

Fig. 3

den Ablauf der im Beispiel 3 beschriebenen Verfahrensvariante.

Fig. 3a

einen Teilquerschnitt durch eine Platte gemäß Fig. 2 und 3.

It shows:

Fig. 1

the sequence of the process variant described in Example 1,

Fig. 1a

a partial cross section through a plate according to Figure 1,

Fig. 2

the sequence of the process variant described in Example 2,

Fig. 3

the sequence of the process variant described in Example 3.

Fig. 3a

3 and a partial cross section through a plate according to FIGS. 2 and 3.

In the figures, functionally identical components are provided with the same numbers. In Fig. 1, the partially cured synthetic resin-containing kraft paper 1 is provided with a dye-containing radiation-polymerizable liquid layer 2. The layer 2 is covered with the plastic film 3 and cured in the device 4 with electron beams. 2, the dye-containing layer 5 has already been partially cured by radiation when it is provided with the transparent liquid layer 6 polymerizable by radiation. The plastic film 3 is applied to the layer 6. 3 differs from FIG. 1 only in that there is still a transparent liquid layer 6 polymerizable by radiation on the plastic film 3. In the figures, the deflection rollers are 7,8,9,10 and the coating devices 11 and 12. 1a and 3a, according to the layer arrangements of FIGS. 1, 2 and 3, pressed plates 14 can be seen. The stack forming the core is designated 13.

example 1

As shown in Fig. 1, a paste-like liquid 2 (viscosity 50 poise at 25 ° C) from a radiation. After a partial curing of the resin with a first hardened with phenol-formaldehyde resin (resin application 70%) impregnated polymerizable mixture of 85 parts by weight aliphatic urethane acrylate oligomers as prepolymer, 15 parts by weight Hexanediol diacrylate as a dilution monomer and 10 parts by weight organic dye pigments applied, forming a closed film (layer thickness about 80 microns). Immediately afterwards, a matt biaxially stretched monofoil 3 made of polypropylene, which contains 8% by weight calcium carbonate, average particle size 3 μm, is applied to this film made of radiation-polymerizable compounds and the film is crosslinked largely homogeneously with electron beams at room temperature without applying pressure. The absorbed radiation dose is 60 kGy.

• Dekorative Schicht 2 (durch Strahlung polymerisiertes Kunstharz mit organischen Farbstoffpigmenten) als äußere Schicht auf einer vorimprägnierten Papier schicht 1,
• 50 Papierbahnen (mit Phenol-Formaldehyd-Harz getränkt) als Kernschicht 13.
• Dekorative Schicht 2 (durch Strahlung polymerisiertes Kunstharz mit organischen Farbstoffpigmenten) als äußere Schicht auf einer vorimprägnierten Papierschicht 1.

After removing the plastic film 3, the paper 1 with the synthetic resin layer 2 lying on the outside, which is copolymerized by radiation, is placed on the outside of a stack 13 of 50 papers lying one above the other. The papers were previously soaked in thermosetting phenol-formaldehyde resin and the resin was partially cured. The layer package is pressed in a press between two structured sheets at 150 ° C. and 80 bar for 10 minutes. It has the following structure:

• Decorative layer 2 (radiation-polymerized synthetic resin with organic dye pigments) as an outer layer on a pre-impregnated paper layer 1,
• 50 paper webs (impregnated with phenol-formaldehyde resin) as core layer 13.
• Decorative layer 2 (polymerized by radiation Synthetic resin with organic dye pigments) as an outer layer on a pre-impregnated paper layer 1.

The 10 mm thick decorative plate 14 obtained on both sides has a scratch resistance of greater than 3.0 N (DIN 53799, part 10). It is insensitive to hydrolysis and shows no changes after boiling in water for 100 hours. Concentrated mineral acid does not attack its surface for a period of 6 hours (DIN 53230). The light fastness of this plate is rated 8 (DIN 54004). The resistance of the plate to weather influences is measured according to ASTM G 53-84, whereby a time cycle of 4 h UV / 4 h CON (condensation period) at a test temperature of 50 ° C. is observed over 1500 h. The decorative surfaces show a low surface gloss corresponding to a reflectometer value of 20-22, radiation angle 60 ° or a reflectometer value of 44-45, radiation angle 85 ° (DIN 67 530). After weathering, the panel shows no discoloration or change in gloss.

Example 2

• Transparente Schicht 6 (durch Strahlung polymerisiertes Kunstharz) als äußerste Schicht,
• Dekorative Schicht 5 (durch Strahlung polymerisiertes Kunstharz mit organischen Farbstoffpigmenten) beide Schichten auf einer vorimprägnierten Papierschicht 1,
• 50 Papierbahnen (mit Phenol-Formaldehyd-Harz getränkt) als Kernschicht 13.
• Dekorative Schicht 5 (durch Strahlung polymerisiertes Kunstharz mit organischen Farbstoffpigmenten)
• Transparente Schicht 6 (durch Strahlung polymerisiertes Kunstharz) als äußerste Schicht, beide Schichten auf einer vorimprägnierten Papierschicht 1.

The viscous, radiation-polymerizable, dye-containing liquid 2 of Example 1 is, as described in Example 1, applied to a pre-hardened phenol-formaldehyde resin containing sodium kraft paper 1 and largely homogeneously crosslinked with electron beams. The absorbed dose is 5 to 10 kGy. On the paper surface on which the radiation polymerized decorative synthetic resin layer 5 is, as shown in Fig. 2, a further layer 6 of transparent - ie dye-free - radiation-polymerizable liquid is applied with rollers or rotary screen printing, which contains, apart from the dye, the same compounds as the first applied layer. This layer forms a closed film with a layer thickness of approximately 20 µm. Immediately after this second layer has been applied, a matt monofoil 3 made of polyethylene terephthalate and biaxially oriented by stretching is placed on the wet layer 6. Analogously to Example 1, curing is carried out using electron beams. The absorbed radiation dose is 60 kGy. After removing the plastic film 3, the paper 1 with the synthetic resin layer 6 lying on the outside, which is copolymerized by radiation, is placed on the outside of a stack 13 of 50 papers lying one above the other. The papers were previously soaked in thermosetting phenol-formaldehyde resin and the resin was partially cured. The layer package is pressed in a press between two sheets at 150 ° C. and 80 bar for 10 minutes. It has the following structure:

• Transparent layer 6 (radiation polymerized synthetic resin) as the outermost layer,
• Decorative layer 5 (radiation-polymerized synthetic resin with organic dye pigments) both layers on a pre-impregnated paper layer 1,
• 50 paper webs (impregnated with phenol-formaldehyde resin) as core layer 13.
• Decorative layer 5 (polymerized by radiation Synthetic resin with organic dye pigments)
• Transparent layer 6 (radiation polymerized synthetic resin) as the outermost layer, both layers on a pre-impregnated paper layer 1.

The decorative plate 14 obtained has a scratch resistance of greater than 2.0 N (DIN 53 799, part 10). Concentrated mineral acid does not attack its surface for 6 hours. The light fastness of this plate is rated 8 (DIN 54 004). It shows a surface gloss corresponding to a reflectometer value of 22-24, radiation angle 60 °, or a reflectometer value of 44-45, radiation angle 85 ° (DIN 67 530).

Example 3

After partial curing of the resin, the pasty dye-containing liquid 2 made of radiation-polymerizable compounds of Example 1 is applied to a sodium kraft paper 1 initially impregnated with heat-curable phenol-formaldehyde resin (resin application 70%), a closed film (layer thickness approximately 80 μm) trains (see FIG. 3).

A transparent layer 6 of a pasty, dye-free liquid made of the same compounds polymerizable by radiation (layer thickness about 20 to 40 μm) is applied to a matted plastic film 3 made of polypropylene. The paper 1 and the plastic film 3 are then placed one on top of the other in sheet or web form, so that the two liquid layers 2, 6 come into contact with one another. Make sure that there are no air pockets. The polymerizable compounds are crosslinked by means of electron beams which strike the liquid layers 2, 6 through the plastic film 3. The absorbed dose is 60 kGy. After removal of the plastic film 3, the paper 1 with the polymerized surface layer 2, 6 is further processed into a decorative plate 14 by heat pressing with a paper stack 13 as described in Example 2.

The synthetic resin layers polymerized by radiation in the examples still show relatively low scratch resistance values in the range from about 0.7 to 0.9 Newton before the hot pressing. Only after the synthetic resin layer polymerized by radiation has been subjected to heat compression according to the invention is a surprisingly obtained a significantly higher surface hardness of the plate.

The one with a reflectometer type RB according to Dr. A long reflectometer value measured according to DIN 67 530 is 45 to 47, radiation angle 20 ° or approximately 83, radiation angle 60 ° if the matt plastic film is missing when crosslinked with electron beams. It can be reduced to values from 37 to 41, angle of incidence 20 ° or approximately 79, angle of incidence 60 °, if structured pressing elements are used in the heat pressing, which, for example, include an outermost layer of the plate Give surface texture similar to orange structure. By adding matting agents to the surface layer, even lower reflectometer values can be achieved, which are approximately 30 to 36, angle of incidence 20 °, or approximately 75, angle of incidence 60 °. However, the particularly low gloss values according to the invention can only be achieved by the special measures in the polymerization of the synthetic resin layer.

Claims (9)

1. A decorative panel having at least one mat surface, comprising, a core layer (13) and a decorative layer on one or both sides, at least the outermost layer (2,6) of the panel (14) on at least one of the two surfaces of the panel being predominantly composed of a synthetic resin comprising one or more components polymerized by radiation and selected from the group consisting of unsaturated acrylates and methacrylates, and this layer (2,6) being scratch-resistant at a scratch loading of at least 1.5 Newtons, preferably 2 to 7 Newtons (DIN 53,799, Part 10) and having a reflectometer value within the range of not more than 50, 85° angle of incidence (DIN 67,530).
2. A decorative panel as claimed in claim 1, wherein the synthetic resin is composed of an epoxy-acrylate or silicone-acrylate oligomer, preferably a polyester acrylate oligomer and especially a urethane acrylate oligomer or the corresponding methacrylate oligomers as prepolymers capable of polymerization by radiation, which has been polymerized by radiation, if appropriate with a mono-, tetra-, penta- and/or hexaacrylate, preferably a diacrylate or triacrylate, of polyols or ether-polyols, or the corresponding methacrylates.
3. A decorative panel as claimed in claim 2, wherein the prepolymer is an aliphatic urethane acrylate oligomer which has been polymerized by radiation with a diacrylate or triacrylate.
4. A decorative panel as claimed in any of claims 1 to 3, wherein the radiation-polymerized, outermost layer (2) of the panel (14) is decorative, and a sheet of paper (1) is optionally located between the core layer (13) and the outermost layer.
5. A decorative panel as claimed in any of claims 1 to 3, wherein the radiation-polymerized, outermost layer (6) of the panel (14) is transparent, and a decorative layer (2) composed of a decorative paper or comprising the components which have been polymerized by radiation is located between the core layer (13) and this outermost layer.
6. A process for the production of the decorative panel (14) as claimed in any of claims 1 to 5, wherein, in a first stage, at least one liquid surface layer (2,5,6) which comprises the radiation-polymerizable components of claim 1 is applied to a substrate (1) and is subsequently polymerized by radiation in a second stage, a film (3) or panel based on plastics and/or paper and having a rough surface being located, during the second stage, on the liquid surface layer (2), and, after the second stage, the surface layer (2) which has been polymerized by radiation is compressed at an elevated temperature together with the substrate (1), the thermosetting resins being cured in the process and the film (3) or panel based on plastics and/or paper and having a rough surface being, if appropriate, subsequently removed.
7. The process as claimed in claim 6, wherein the liquid surface layer (5) comprises colored pigments and/or further decorative additives, and to this layer there is applied, if appropriate, after the polymerization effected by radiation, a further, transparent surface layer (6) which comprises the radiationpolymerizable components, and this further surface layer (6) is polymerized by radiation.
8. The process as claimed in claim 6 or 7, wherein the substrate is a sheet of paper (1) containing thermosetting, partly cured synthetic resin, and, when compressing, the sheet of paper (1) together with the outer surface layer (2,5,6) which has been polymerized by radiation, rests on a stack of fiber layers, in particular paper layers, intended to form the core layer (13).
9. The process as claimed in any of claims 6 to 8, wherein the surface layer (2,5,6) which has been polymerized by radiation is compressed at a temperature from 80 to 220 °C and a pressure from 5 to 100 bar.

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