EP2106903A1 - Method for scattering friction-inhibiting materials and accompanying device - Google Patents

Abstract

The method comprises sequentially introducing two particle fractions, each of which has different sizes and/or compositions, on a flat substrate using electrostatic field with different potential differences. The electrostatic field has a potential difference of 30-100 kV. A distance of the electrodes developing the electrostatic field is 15-300 mm. The particles have an average particle size of 20-70 mu m. The substrate has an adhesion promoting layer that is conductive and is a resin layer or a lacquer layer. The average applied quantity of the particles is 20-30 g/m 2>. The method comprises sequentially introducing two particle fractions, each of which has different sizes and/or compositions, on a flat substrate using electrostatic field with different potential differences. The electrostatic field has a potential difference of 30-100 kV. A distance of the electrodes developing the electrostatic field is 15-300 mm. The particles have an average particle size of 20-70 mu m. The substrate has an adhesion promoting layer that is conductive and is a resin layer or a lacquer layer. The average applied quantity of the particles is 20-30 g/m 2>, where the distribution accuracy is 2% or better. The particles have a surface resistance of 10 1> 2>omega /cm 2>. An independent claim is included for a device for applying wear-resistant particles on a flat substrate.

Description

The invention relates to a method and an apparatus for the production of abrasion-resistant surfaces which are coated with resin and / or other adhesion promoters or paints. Such methods are used in the production of coated wood materials, which are then processed for example to countertops or laminate floors. In particular, laminate flooring is exposed to a high mechanical load, so that the wood material with the applied decorative layer on the surface is not usable without additional wear protection. This wear protection is usually made of a synthetic resin and hard particles, preferably corundum. Depending on the type, the amount, the type of application and the constructive integration in the entire structure can be achieved by means of the hard particles high resistance to wear due to continuous loads, as well as against damage from scratches. It comes to varying degrees to a deterioration of the visual appearance, for example, by bright, schlieren-like structures, which adversely affect the color, contrast, transparency and sharpness of the decor. A lifelike reproduction of the wood or the decors and a high resistance to wear and scratches are therefore key quality criteria for laminate flooring and other coated Floor coverings of wood and wood-based materials. The wear protection by hard particles is therefore of great importance in the production. However, the state of the art in this area differs less in the type of hard materials, but rather in the nature of their constructive involvement and in the nature of the application.

Fig. 1 shows an example of the structure of a laminate floor. These are usually constructed of an elastic polymer (impact sound insulation) (1), a wood material as a carrier material (3) with a counter-pull (2), a decorative paper (5) with optional underlay paper (4) and the overlay paper (6 ) made of thin cellulose.

The plastic and the hard particles as wear protection are applied in different ways, but generally in the area of the decorative layer and the overlay. When assessing the different production methods and constructions, not only the low wear of the final product and its optical quality but also aspects of production economy have to be considered.

The prior art discloses various methods of making a wear-resistant coating of laminate flooring.

That's how it describes US 4,940,503 a method wherein abrasion resistant particles are optionally applied to a melamine resin impregnated overlay or melamine resin impregnated decorative paper. The application is carried out by scattering or by electrostatic coating, for example by triboelectric charging of the particles. Overlay and decorative paper are then pressed together so that a decorative paper with abrasion-resistant surface is obtained. Alternatively, powdered α-cellulose may be applied instead of the overlay. However, the abrasion resistance that can be achieved with such a process is relatively low compared to other processes. It must be made separately an overlay, so a paper.

The WO 00/44984 A1 discloses a process in which a dispersion consisting of a binder and abrasion-resistant particles such as corundum or silicon carbide is sprayed onto a decorative paper. By the spray process particles of coarser grain size can be used. This layer immediately forms the surface to be stressed, whereby an overlay is dispensed with. Because the hard particles are integrated directly at the surface and at the same time efficiently, this method achieves high abrasion values. However, the expenditure on the application of the dispersion is comparatively large and expensive in comparison to the scattering of abrasion-resistant particles in the form of a powder. The high cost also results from the increased wear of the nozzles and conveyors. Another disadvantage is that during pressing, the hard particles are located directly on the surface and thus they permanently damage the surfaces of the press plates, with the result of an unsatisfactory surface image of the end product.

The WO 00/44576 A1 tries to overcome this disadvantage by first abrasion-resistant particles such as corundum are sprinkled on impregnated decorative paper. On top of this surface are then fibers together with a binder applied and the layer system pressed. Covering with fibers prevents direct contact between the hard particles and the press plate. This process offers advantages in terms of production, but the surface does not achieve the decorative appearance or the wear resistance of products which have an overlay over the decorative layer.

The disadvantages such as high expenditure on equipment and high wear also apply to the air spray ( EP 1 801 290 ). With this method, a uniform distribution of the hard particles is to be achieved.

In contrast, the application by means of a sieve or a roller is a simple and easy-to-use method. However, this is limited by the lack of possibilities of a specific area and depth distribution. In particular, the area distribution is subject here, as well as in the air spray or the use of a dispersion, large statistical fluctuations. In order to obtain wear-resistant products in the use of these methods, fluctuations must be compensated for by a correspondingly increased application weight.

In the WO 2005/080096 A2 are used an electrically non-conductive scattering roller, doctor blade or brush, which are charged with electrical charge, so as to transfer electrical charges to the fibers. These are applied to the abrasion-resistant layer so that they straighten up due to their charge. The disadvantage of this charging process is the considerable dependence on the fiber material and on the climatic factors.

The lack of a powerful application method thus limits not only the quality of the final product, but also the applicability of improved manufacturing methods such as the direct coating of decorative layers with resins or paints. This dispenses with the use of an overlay, which includes not only simplifications in terms of production, but also the option of an improved visual appearance. However, very high demands are placed on the application technology of the hard particles. This must first allow an exactly reproducible area distribution, so that there is no need to compensate for inaccuracies with a generally increased entry. Furthermore, the process must ensure the separation of the particles and, for example, dissolve agglomerates. In addition, particularly in the case of a direct coating of decorative layers with resins and paints, it is particularly important to have a specific three-dimensional arrangement of the particles within the resin layer. If these could be incorporated in the depth of the resin or lacquer layer in a defined concentration or size ratio, then even with a direct coating, an effective protection against fading with good optical properties can be assumed.

The invention is therefore based on the object to develop a coating method, which ensures a precise, well-controlled and reliably reproducible application of hard particles. It should not only allow a surface but also a depth distribution and be easy to handle in terms of production technology.

The object is achieved by an electrostatic application method with high voltage generators. The hard particles are electrostatically charged by conduction and / or corona. The potential differences between the electrode and machine elements or the workpiece surface are used to specifically control the direction and velocity of the particles during the application. The invention is defined in the patent claims.

According to the invention, it is provided that the electrostatic field used for the application has a potential difference of at least 10 kV, preferred potential differences are in particular 10 to 100 kV, more preferably 20 to 100 kV, further preferably 30 to 100 kV. The potential difference used is preferably adjusted to the intended distance of the electrodes, that the breakdown voltage of the medium between the electrodes (usually air) is not exceeded with sufficient certainty. For air, this breakdown voltage in the inhomogeneous field of these electrode arrangements is for example about 5 kV / cm. The potential difference is measured between the electrode which lastly electrostatically charges the particles before striking the substrate and / or accelerates the one hand and the counterelectrode belonging to the substrate (generally earthed) on the other hand. The method offers significant advantages compared to the conventional methods. As a result of the electrostatic charge, the particles are not only reliably separated in the sense of dissolving agglomerates. The particles form additional spatial arrangements during the application, whereby the distance of individual Affect particles to each other. This spatial arrangement finds a correspondence in the uniformity of the surface application.

A spatial arrangement, as well as an exact area distribution, is only partially possible in the conventional scattering by sieving or air spraying. As a result, areas with an increased particle density thus arise, which has a direct effect on the quality of the scattered image.

The electrostatic application also allows a targeted acceleration of particles, so that the type of particles and their size can be considered. This option not only improves the control of the area application. In addition, the penetration depth into the resin or lacquer layer can be preset via the kinetic energy. Thus, within the resin layer several layers - even differentiated by particle sizes - are introduced. If, for example, fine particles are preferably introduced in the surface region and coarser particles in an underlying layer according to this process, a very efficient wear protection can be achieved with little optical impairment. Regardless of a three-dimensional distribution, the orientation of the particles in the room can additionally be influenced ( Fig. 2 ). While with round grain shapes (A, C) only a deeper integration into the resin layer can be achieved, with a needle-like grain shape (B, D) a uniform spatial positioning in the resin or lacquer layer can be achieved. Thus, according to the invention, two or more particle fractions can be successively applied, each particle fraction having different sizes and / or compositions may have and these fractions can be applied with different potential differences and thus different depths in the corresponding surface of the substrate (usually a resin layer) can penetrate. For example, depending on the particle shape, size, and the potential difference used, the application conditions may be set such that a particle fraction is wetted with resin at about 50% of its surface area (correspondingly protruding out of the resin layer), and, for example, application conditions may be set in which 80% or 100% of the surface (in the middle) are wetted with resin. Furthermore, composite materials of fibers and hard particles can be applied; Such composite particles are described, for example, in European Patent Application 08 003 273, the priority of which is claimed. If sequentially applied particle fractions have different sizes, it may be advantageous to introduce the larger particles first and into deeper resin layers (with correspondingly large potential differences) and then introduce the smaller particle fractions into the higher resin layers.

It is thus possible, in general, also to determine the shape of the particles which are effective on the surface via the application method. Wear tests with particles of different grain shape and surface have shown that these significantly affect the wear behavior. Accordingly, it can be assumed that targeted spatial positioning of particles also represents an option for improving wear protection.

The distance of the electrostatic field building up Electrodes are preferably 15 to 300 mm. The electrode arranged at a distance from the substrate can, for example, be an electrically conductive metal wire mesh, the counterelectrode is effectively formed by the corresponding receiving layer (in particular a resin or lacquer layer) of the substrate, which preferably has a certain conductivity. Since the substrate in the method according to the invention is preferably passed continuously under the device according to the invention, a counter electrode located in contact with the rear side of the substrate is preferably provided, which is preferably earthed.

According to the invention, it is possible to set the surface resistivity of the recording layer of the substrate such that given the given vectorial properties of the electrostatic field used, desired accuracies in the area and depth distribution of the applied particles are achieved. In addition to the adjustment of the conductivity or the surface resistance of the coating, the surface resistance of the applied particles can also be selectively modified, for example by appropriate surface coatings. By way of example, mention may be made here of silanization. A preferable surface resistance is, for example, 10 ¹² Ω / cm ² or smaller.

According to the invention, the corresponding parameters can be set in such a way that wear-inhibiting particles, in particular wear-inhibiting particles of a size of approximately 10 μm, are introduced into the corresponding layer of the substrate in an agglomerate-free and evenly distributed manner. so that a high transparency and scratch resistance of the surface is achieved. Particle distributions (in particular structure and concentration profiles of the particles) can also be set in a defined manner with the aim of optimizing the flow behavior during the pressing process, so that a pressure plate wear minimizes static charge of the ready-to-use carrier layers, eg in the subsequent inspection, and good transparency within the desired abrasion class or wear resistance class is achieved.

When sequentially depositing grain particle fractions, the substrate may already be repeatedly coated with resin or varnish on the same application device, alternatively it may sequentially pass through two or more sequential application devices that apply the appropriate particle fraction. For example, as a first particle fraction coarse corundum to improve the abrasion resistance, as a second particle fraction medium corundum to improve the resistance to scratches, and as a third particle fraction fine alumina to improve the micro scratch resistance and reduce the electrostatic charge of the floor coverings (laminate or other coated floor coverings of wood and Wood materials) are applied.

An advantageous variant of the method according to the invention Fig. 4 Uses the direct electrostatic charging principle through line and / or corona using a metering unit (4) and two distribution units (II). These are installed one above the other within a correspondingly insulated support frame, wherein the metering unit (4) is slightly offset relative to the upper distribution unit. Thus, the distribution units (II) are located above the carrier material (1) to be coated, and above this the metering unit (4).

The metering unit (4) consists of a container whose lower portion is formed as an electrode (9) and which has a high voltage - either DC or pulsed AC voltage with pulsed half-wave - has. The electric field between this and the ground potential resin or adhesive layer of the workpiece (2) is several 10 kV. The spatial form of the electrical field thus obtained corresponds to that of a plane-parallel plate pair, is relatively homogeneous and its field strength can be easily maintained in a rollover or non-impact area. The upper part of the dosing unit is potential-free. The principle of charging is in Fig. 3 shown.

The distribution units (II) consist of a frame and a bottom made of conductive mesh or parallel corona wires stretched. The trays are interchangeable to vary in terms of mesh size and wire spacing. The upper distribution unit is kept floating, while the lower one has a voltage of preferably at least 30 kV (or some 10 kV).

When the high voltage is applied to the electrode in the metering unit (4), the hard particles are charged, an alignment in the electric field and finally an accelerated movement in the direction of the ground potential-carrying resin or lacquer layer (2). in the In contrast to a mechanically or by air vortex induced particle movement causes an acceleration by electric field forces a trajectory with improved directional accuracy and distance accuracy when hitting the resin or paint layer.

This directional determination and distance accuracy is again significantly improved by the distribution units (II). After leaving the dosing unit (4), the particles (3) first describe an arcuate trajectory with differing directions and speeds. With the passage through the first, potential-free distribution aggregate it is adjusted. The distance to the surface of the resin or adhesive layer is rectilinear and accelerated by the potential gradient between the first and second distribution aggregate or between the second distribution aggregate and the earth potential having resin or adhesive layer covered.

Instead of the described metering unit with a fluidization of the particles in the electrostatic field, other devices can be used. Thus, the particles can be supplied via a belt feeder, a vibrating trough or a gap-shaped metering hopper with highly sensitive layer thickness limitation (both by means of gravimetric control). Alternatively, the material supply can also be made via an example vibrating or vibrating sieve. If a dosing unit is used which is not connected to the high-voltage potential, the construction of different electrostatic cells takes place Potentials by means of the stepwise construction of the distribution units or the resin or lacquer layer.

A particular advantage of the application method according to the invention consists in the option of adapting the apparatus arrangement and process parameters to the respective materials to be applied. However, based on the materials, it is also possible to select or modify them in such a way that the specific advantages of the electrostatic application process can be fully exploited.

The materials to be applied consist, for example, of hard particles, hard particles with associated additional components or else additional materials whose application improves the effect of the hard particles.

The suitability of the materials to be applied for the electrostatic process is largely determined by the degree of charging in electric fields.

This depends on the external electric field strength and the electrical properties - specific surface resistance and permittivity - as well as the geometric shape of the materials to be applied. The electrical properties carry the scattering materials in themselves or may be due to surface modifications, e.g. by Wasseranlagerung, be changed.

E=

Elektrisches Feld

D=

Äußere elektrische Erregung

ε₀=

Permittivität des Vakuums

ε_r =

Materialspezifischer Faktor zur Feldkonstante ε₀

The dielectric properties of the scattering materials, the construction materials and the ambient atmosphere are thus able to strengthen or weaken the electric field in the interior of the respective substances, according to $$\overrightarrow{e}=\frac{\overrightarrow{D}}{\epsilon }=\frac{\overrightarrow{D}}{{\epsilon }_{\tau }{\epsilon }_0}\mathrm{,}$$

e =

Electric field

D =

External electrical excitation

ε ₀ =

Permittivity of the vacuum

ε _r =

Material-specific factor for the field constant ε ₀

1. 1. die Ausrichtung länglicher Partikel parallel zu den elektrischen Feldlinien,
2. 2. Verstärkung der elektrischen Felder im Inneren der einzelnen Partikel, verbunden mit der Ausbildung von Feldstärkespitzen an den Austrittsstellen der Feldlinien, die bei scharfkantigen Oberflächenprofilen die Stärke des äußeren Feldes um das Vielfache übertreffen,
3. 3. die Abhängigkeit des Streuverhaltens der Materialien von der Permittivität des Luftvolumens im Streuraum, besonders durch Schwankungen der Luftfeuchte (ε_r Luft = 1; ε_r Wasser= 80)

This field enhancement or attenuation acquires significance in the method according to the invention

1. 1. the alignment of elongated particles parallel to the electric field lines,
2. 2. intensification of the electric fields inside the individual particles, combined with the formation of field strength peaks at the exit points of the field lines, which exceed the strength of the external field by many times in the case of sharp-edged surface profiles,
3. 3. the dependence of the scattering behavior of the materials on the permittivity of the air volume in the scattered space, in particular due to fluctuations in the air humidity (ε _r air = 1; ε _r water = 80)

F =

Kraft auf ein Partikel

E =

Äußere elektrische Feldstärke

m =

Partikelmasse

g =

Erdbeschleunigung

q =

Überschussladung

The specific surface resistance has just as much influence on the force that moves the particles: $$\overrightarrow{\mathrm{F}}\mathrm{=}\mathrm{m}\overrightarrow{\mathrm{G}}\mathrm{+}\mathrm{/}\mathrm{-}\overrightarrow{\mathrm{e}}\mathrm{xq}$$

F =

Force on a particle

E =

External electric field strength

m =

particle mass

g =

acceleration of gravity

q =

Excess charge

With the classical dipole, the size of the opposite charges is the same and thus there is no linear motion.
Forces, which can translate such a dipole into a translational motion, consequently result only from field inhomogeneities or from the interaction of the O-surface dipole layer with the electric field. Estimates show that these two forces are not sufficient in normal field to control the particles in their movement.

As a decisive condition for the directional movement of the particles, there must be an absolute charge surplus on the grain surface, negative if the lower electrode poled as the cathode and positive, if it is poled as the anode.

The lower the surface resistance, the more free charge carriers can absorb this surface during the contact time.

The electric force is then proportional to the field strength (E) and the stronger, the larger the excess charge q is. The force acts in the direction of the voltage gradient. For this reason the trajectories are dependent on the course of the field.

Given in electrostatic application process conditions in the form of specific material properties the particle to be applied and the maximum electric field strength of 5kV / cm. This is determined by the dielectric strength of the air. Particularly common wear-inhibiting substances such as aluminum oxide have no advantageous behavior in electrostatic scattering due to their specific material properties.

However, for such materials to be used as well, surface-modified products are used. The modification generally improves the permittivity of the entire particles. This can also be adapted gradually to the specific conditions of the application. By choosing a suitable surface modification, there is thus a further option for a targeted optimization of the electrostatic application method.

The surface modification has been tested in the form of a coating. For example, a colloidal solution or dispersion based on water and / or resin, which contains synthetic, amorphous nanoscale particles, is used. In addition to metal oxides, SiO ₂ in particular has proved successful, because the visual appearance of the surface to be protected is scarcely impaired in terms of transparency and color fidelity.

Another special type of surface modification consists of a coating by means of a colloidal solution or dispersion and an additional fibrous material, preferably cellulose. This can be due to the nature, the fiber size, the proportion and the type of integration within a wide range can be varied. On the one hand, the fiber material is suitable for controlling the permittivity and the surface resistance of the material to be applied or, for particles under 80 μm, it is the latter in the first place which enables it to be electrostatically scattered. Irrespective of this, the proportion of fibers causes a significantly improved incorporation of the hard particles into the resin or lacquer layer of the material to be coated. The fiber component consists of a cellulosic material, for example of cellulose microfibers and / or microcrystalline cellulose with a maximum extension between 5 .mu.m and 100 .mu.m, preferably between 20 .mu.m and 70 .mu.m. The hard particles preferably consist of corundum having an average particle size of between 0.7 μm and 70 μm, preferably between 5 μm and 30 μm. Accordingly, a composite material of hard particles and fiber material can be obtained comprising 2-90% by weight of cellulosic material, 1-50% by weight of nanoscale particles (15-100 nm in diameter, amorphous SiO ₂ ) and 1-97% by weight. contains% hard particles.

example 1

According to Fig.4 an application device according to the invention as a component to be coated on a provided with melamine resins or paints carrier material (1) made of a wood material with decorative layer. The dosing unit (4) consists of a cup-shaped container made of polypropylene and a grounded sieve as a counter electrode (8) in the form of a rectangular mesh with a mesh size of 225 microns. The stray cup is made of an electrical insulating material (polyethylene) and has in the bottom of an electrode (9) made of solid stainless steel sheet and with projecting into the interior of the container tips. This is a voltage of 30 kV, while the rest of the container is kept potential free. Due to the electrostatic charge is a separation and repulsion of the particles. The scattering cup is oriented in such a way that the particles describe an inclined trajectory in the form of a trajectory parabola and thus fall into the sieve serving as a grounded counterelectrode (8). In the immediate vicinity of the sieve, the charge of the separated particles is predominantly released and they reach the distribution unit (5) by gravity.

As abrasion-resistant material is a composite of corundum (50 wt .-%, average particle size 20 microns), cellulose microfibers (30 wt .-%, maximum extension 40 microns) and nanoscale particles (20 wt .-%, about 15 nm Diameter, amorphous SiO ₂ ) are used. The distribution unit (5) also consists of a sieve with conductive sieve fabric made of stainless steel wire with a mesh size of 106 microns. It acts as a high voltage electrode and was subjected to a high voltage of -60 kV to ground. When passing through this sieve, the particles are reloaded. Below this Verteilungssiebes is the carrier material (1), which takes over the function of the counter electrode in conjunction with the grounded machine-structural support (6). The electric field is established between the distribution screen and the carrier material. The spacing between the distribution screen and the carrier material was preferably set at 15 cm and that between the distribution screen and the overlying metering screen at a maximum of 50 cm. According to the function of the components, a distinction can be made between a metering system (I) and a distribution system (II). At a feed rate of the carrier material of 15 m / min, the applied amount of wear-resistant material, for example, 22 g / m ² . The deviation of the area-related order amounts to +/- 4 mg / dm ² , measured on material cut-outs of 10 cm x 10 cm. The wear-inhibiting material (3) is again singled and accelerated with the passage through the distribution unit (5) and strikes the carrier material (1) in a straight line. It has an intensive contact with the resin layer and is partially embedded in this. It differs significantly from similar composite particles that are scattered according to the prior art, for example by means of a sieve or applied by means of an air flow. If wear-inhibiting material (3) is applied in excess and thus to the carrier material (1) in such a way that it has no direct contact with the resin layer (2), then it is excess and is recovered by means of a suction device (7).

Example 2

Deviating from Fig. 4 is appropriate Fig.5 the metering unit designed as a vibrating trough. The wear-inhibiting particles are scattered from a reservoir (9) on the vibrating trough (8). The reservoir is controlled gravimetrically, so that a defined amount of anti-wear particles is released per unit time. The vibrating trough (8) has a tilt angle of 15 degrees, oscillates with a frequency of 40-60 Hz and an amplitude of 0.1-5 mm. As a result of the vibration, the particles are fed to the front edge of the vibrating trough and at the same time distributed over the width thereof. However, there is an uneven distribution of the particles across the width of the vibrating trough. Uniform feeding of the particles to the distribution aggregate over the entire width is achieved by forming the front edge of the channel as a gap. In doing so, a baffle mounted perpendicular to the plane of the conveyor trough limits and standardizes the thickness of the conveyed particle layer. In contrast to Fig. 4 sets the metering unit formed as a vibrating trough, the particles in a linear area free, with an exact, uniform dosage over the entire width is achieved. This exact dosage remains even after passage of the particles through the distribution unit (5), so that a particularly uniform application of the particles can be achieved on the carrier material. In particular when using fine particles, the particle flow between metering pump and Verteilunsaggreat over a high voltage electrode consisting of 200 micron thick corona wires fed with - 30 kV (4) are passed. As a result, by means of electrostatic charging, an additional separation and mutual spacing of the particles is achieved.

The wear-resistant material used is a corundum coated with nanoscale, amorphous SiO ₂ (diameter approx. 15 nm). The mean diameter of the coated particles is 50μm. Notwithstanding Example 1, the distribution unit (5) is subjected to a voltage of -60 kV. At a feed rate of the carrier material of 10 m / min, the applied amount of wear-resistant material is 24 g / m ² . The deviation of the area-related application was determined to be +/- 5 mg / dm ² , measured on material sections 10 cm x 10 cm. The wear-resistant material (3) is wetted in the majority to at least 50% of its surface with resin. When the high voltage at the distribution unit is increased to -100 kV, the surface of the majority of the wear-inhibiting particles is at least 80% wetted with resin. With the control of the high voltage on the distribution unit, a three-dimensional distribution of the wear-inhibiting particles in the resin matrix can thus be achieved in the case of a plurality of successive application processes. Excess particles are removed by means of a suction device (7).

Claims (13)

Method for applying wear-inhibiting particles to a planar substrate, characterized in that the application is effected by means of an electrostatic field with a potential difference of at least 10 kV. A method according to claim 1, characterized in that the potential difference is 10 to 100 kV, preferably 20 to 100 kV, more preferably 30 to 100 kV. A method according to claim 1 or 2, characterized in that sequentially at least two particle fractions are applied, preferably each particle fraction having different sizes and / or compositions and / or wherein the particle fractions are applied with different potential differences. Method according to one of claims 1 to 3, characterized in that the distance of the electrodes constituting the electrostatic field is 15 to 300 mm. Method according to one of claims 1 to 4, characterized in that the substrate is a cellulose or wood material, preferably a laminate, a wood-based panel, or an overlay paper. Method according to one of claims 1 to 5, characterized in that the wear-inhibiting particles have average particle sizes of 1 micron to 700 microns, preferably 5 to 100 microns, more preferably 20 to 70 microns. Method according to one of claims 1 to 6, characterized in that the substrate has an adhesion-promoting layer, which is preferably conductive. A method according to claim 7, characterized in that the adhesion-promoting layer is a resin or lacquer layer. Method according to one of claims 1 to 8, characterized in that the average application amount of the anti-wear particles is 5 to 100 g / m ² , preferably 10 to 50 g / m ² , more preferably 20 to 30 g / m ² ; wherein preferably the distribution accuracy is 10% or better, preferably 5% or better, more preferably 3% or better, further preferably 2% or better. Method according to one of claims 1 to 9, characterized in that the wear-inhibiting particles have a surface resistance of 10 ¹² Ω / cm ² or less. Device for carrying out the method according to one of claims 1 to 9, characterized in that it comprises a metering device and a distribution device for wear-inhibiting particles. Apparatus according to claim 11, characterized in that the metering device has a high voltage electrode or a vibrating trough. Apparatus according to claim 11 or 12, characterized in that the distribution device comprises a sieve, which is preferably additionally designed as a high voltage electrode.

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