EP2737099A2

EP2737099A2 - Method for applying a coating to a substrate, coating, and use of particles

Info

Publication number: EP2737099A2
Application number: EP12741312.8A
Authority: EP
Inventors: Markus Rupprecht; Christian Wolfrum; Marco Greb; Eckart Theophile
Original assignee: Eckart GmbH
Current assignee: Eckart GmbH
Priority date: 2011-07-25
Filing date: 2012-07-25
Publication date: 2014-06-04
Also published as: WO2013014212A2; WO2013014212A3; KR20140068031A; DE102011052118A1; US20140170410A1; CN103703159A; JP2014521835A

Abstract

The present invention relates to a method for applying a coating to a substrate, using cold plasma, wherein particles provided with a polymer coating are fed into a cold plasma at less than 3000 K and the particles activated thereby are deposited on a substrate. In addition, the present invention relates to a substrate coating which can be obtained by the methods according to the invention. In addition, the present invention relates to the use of platelet-shaped particles having a polymer coating having a median thickness of less than 2 µm in the substrate coating, using a cold plasma.

Description

Method for applying a coating to a substrate, coating and use of particles

The present invention relates to a method and a device for applying a coating to a substrate, in which by passing a working gas through an excitation zone a plasma jet of a

Low-temperature plasma is generated. Moreover, the invention relates to a

Coating on a substrate of at least partially with each other

grown particles. Furthermore, the invention relates to the use of particles which are surrounded by a shell consisting of a crosslinked polymer.

The generation of layers on substrates has long been known and of high economic interest. There are a variety of different methods used, the partially procedurally reduced pressure, very high

Gas speeds or high temperatures condition. In particular, so-called spraying methods are used.

One known method is plasma spraying, in which a gas or gas mixture flowing through an arc of a plasma torch is ionized. In the

Ionization is a highly heated, electrically conductive gas produced at a temperature of up to 20,000 K. In this plasma jet powder, usually injected in a particle size distribution between 5 to 120 μιτι, which by the high

Plasma temperature is melted. The plasma jet entrains the powder particles and places them on the substrate to be coated. The plasma coating by way of plasma spraying can be carried out under normal atmosphere.

The high gas temperatures of over 10,000 ° C are required to melt the powder and thus to be able to deposit as a layer. So that's it Plasma spraying energetically very expensive, creating a cost-effective

Coating of substrates is often not possible. In addition, must to

Generation of high temperatures consuming apparatuses are used.

Due to the high temperatures, temperature-sensitive and / or very thin substrates, such as polymer films and / or paper, can not be coated. Due to the high thermal energy, such substrates are involved

Damage. In some cases, elaborate pretreatment steps are necessary to ensure adequate adhesion of the deposited layers to the surface. Another disadvantage is that during plasma spraying, a high thermal load of the particles used occurs, as a result of which

especially when using metallic particles, at least partially oxidize. This is particularly disadvantageous when metallic layers are to be deposited, for example, for printed conductors or as

Corrosion protection should be used.

For these reasons, methods have been developed which use so-called atmospheric cold plasma, also referred to as low temperature plasma, to create layers on substrates. In the methods, a method known in the art is a cold plasma jet at atmospheric

Conditions generated and introduced into the plasma jet, a powder, which is then deposited on the substrate.

From EP 1 230 414 B1 a generic method for applying a coating to a substrate is known, in which by passing the

Working gas through an excitation zone a plasma jet of a

Low-temperature plasma is generated under atmospheric conditions. In the plasma jet, a precursor material consisting of monomeric compounds is fed separately from the working gas. For sensitive precursor materials, the feed can be made into the relatively cool plasma jet downstream of the excitation zone. As a result, it is possible to coat the substrate with precursor materials which are stable only at temperatures of up to 200 degrees Celsius or less. A disadvantage of this method is that monomeric compounds are fed as a precursor material in a plasma and reacted there, whereby only relatively low deposition rates of 300-400 nm / sec can be achieved. These are compared to the deposition rates, which are achieved in corresponding processes with powdered starting materials, even with the use of particles which are present in the order of 100 μιτι, by a factor of 10-1000 lower. Accordingly, an economical coating on an industrial scale is not possible with this method. From EP 1 675 971 B1 is another method for coating a

Substrate surface using a plasma jet of a

Low-temperature plasma known to which a fine-grained, coating-forming powder in a size of 0.001 -100 μιτι is supplied by means of a powder conveyor. In contrast to the thermal plasmas, the temperature of a low-temperature plasma in the core of the plasma jet at ambient pressure reaches less than 900 degrees Celsius. For thermal plasmas, however, EP 1 675 971 B1 specifies temperatures in the core of the occurring plasma jet of up to 20,000 degrees Celsius. The document DE102006061435A1 teaches a method for spraying a web, in particular a printed conductor, onto a substrate by introducing into a spray lance, in which a cold plasma (<3000 K) is produced, a powder by means of a carrier gas, which is subsequently applied to a substrate incident. In both methods, fine-grained powder in sizes of 0.001-100 μιτι in a cold plasma (<500 ° C) are fed and as a layer on a surface

deposited. A disadvantage of the described method is that

Higher melting point materials, e.g. ceramic materials or refractory metals can not be melted in the process unless particles of very small mean diameter, i.

For example, less than 1 μιτι used. The offset in the plasma state gas flow rates and thus the plasma gas velocity is so high in the said method, that the residence time of the particles in the hot zones of the plasma is not sufficient to complete melting of the To reach particles. For materials with elevated melting temperature (eg

Ag, Cu, Ni, Fe, Ti, W), therefore, the maximum occurs at the particle surface

Melting and it forms a porous layer in which the particles adhere to each other almost in the initial dimension. Therefore, the references describe a preferred use of low melting metals such as tin and zinc. The effect that the particles melt to a maximum of their outer shell, can be explained by the fact that due to the conditions in the plasma is primarily an activation on the surface. By using very small particles, the specific surface area can be increased, but such powders are difficult to convey, so that they can not be industrially used industrially.

The described methods therefore have fundamental disadvantages.

The object of the invention is to provide a method in which a sufficient activation of the particles is achieved while maintaining good conveyability.

The object is achieved according to the invention by a method with the

Features of claim 1. Accordingly, the coating of substrates with an atmospheric cold plasma, in which the material forming the layer, for example in the form of particles, which are provided with an existing of a crosslinked polymer shell, is introduced. Such a shell can be produced, for example, by applying monomers, oligomers, polymers or mixtures of the abovementioned to the surface of the particles and crosslinking them there.

The present invention relates to a method for applying a coating to a substrate using cold plasma, which is characterized in that the method comprises the following steps:

(A) introducing coated with a polymer coating particles in a directed onto a substrate to be coated cold plasma with a

Plasma temperature of less than 3000 K,

(b) depositing the particles activated in the cold plasma in step (a) on the substrate. According to the invention, "activated particles" mean that the particles can be adhesively applied to the substrate, whereby the particles can be superficially or completely softened or melted or adhere to adhere to the substrate, but the particles can also be in an energy-containing state be offset, which allows the formation of a physical or chemical bond with the substrate.

In certain embodiments of the aforesaid method, the coating, preferably spraying, of the coating is performed on a substrate using a longitudinally extending coating die which is moved or movable at a relative velocity relative to the substrate, in a plasma zone disposed internally one of the coating nozzle upstream electrode, a cold plasma is generated with a plasma temperature of less than 3,000 K, and wherein in the coating die by means of a

Carrier gas, a powder is introduced, which is carried by the plasma toward a front end outlet opening from the coating die, there emerges and strikes the substrate, wherein the powder is particles with a polymer shell.

In certain embodiments of the aforementioned method, the cold plasma is generated in or in front of a coating nozzle and the particles are introduced into the coating nozzle via a carrier gas, wherein the coating nozzle and the substrate are movable relative to one another. Thus, the coating die may be movably disposed or moved relative to the substrate or substrate relative to the coating die. Of course, the

Coating nozzle and the substrate to be arranged movable or moved to each other.

In certain embodiments of the aforementioned methods, the average layer thickness of the, preferably enveloping, polymer coating is less than 2 μm.

In certain embodiments of the aforementioned methods, the cold plasma is applied by applying a pulsed DC voltage or AC voltage generates an ionizable gas.

In certain embodiments of the aforementioned methods, the particles are platy.

In certain embodiments of the aforementioned methods, the particles, preferably the platelet-shaped particles in the plasma zone, react at least partially chemically or physically. Preferably, in some of the foregoing embodiments, the particles at least partially melt.

In certain embodiments of the aforementioned methods, the carrier gas is passed at a flow rate through a container in which the particles are stored as a powder, so that the powder to produce a

Powder dust at least partially swirled and powder dust generated in the

Coating nozzle is introduced.

In certain embodiments of the aforementioned methods, the carrier gas flows through the coating nozzle with a volume flow from a range of 1 Nl / min to 15 Nl / min and preferably at pressures between 0.5 bar to 2 bar. The term "standard liters" or "Nl" in the context of the present invention denotes the

Gas volume that fills 1 liter of room volume in the normal state (1013 mbar and 0 ° C).

In certain embodiments of the aforementioned methods, the cold plasma is generated under pressure and the particles are then applied to the substrate, which corresponds largely to atmospheric conditions.

Preferably, in certain embodiments, the pressure is in a range of 0.5-10 ⁵ - 1.5 x 10 ⁵ Pa.

In certain embodiments of the aforementioned methods, the average thickness of the preferably enveloping polymer coating is less than 300 nm.

In certain embodiments of the aforementioned methods, the

Polymer coating a polymerized (meth) acrylate resin. In certain of the aforementioned embodiments, it is preferably in the Polymer coating around a polymerized acrylate resin.

In certain embodiments of the foregoing methods, the particles are metal particles, preferably platelet-shaped metal particles, and the metals are selected from the group consisting of aluminum, zinc, tin, titanium, iron, copper, silver, gold, tungsten, nickel, lead, platinum, silicon and alloys thereof and mixtures thereof are selected.

In certain embodiments of the foregoing methods, the substrate is selected from the group consisting of metals, plastics, paper, biological materials, glass, ceramics, and mixtures thereof. Preferably, in certain of the foregoing embodiments, the substrate is selected from the group consisting of metals, wood, plastics, paper, and mixtures thereof,

selected.

In certain embodiments of the foregoing processes, the polymer-coated particles are selected from the group consisting of oxides, carbides, silicates, nitrides, phosphates, sulfates, and mixtures thereof.

selected.

Furthermore, the present invention relates to a coating on a substrate, obtainable by a method according to any one of the preceding claims.

In certain embodiments of the aforementioned coating, the particles are platelet-shaped metal particles and the coating has platelet-shaped metal particles at least partially intergrown with each other.

In certain embodiments of the aforementioned coatings, the coating consists of at least partially fused platelet-shaped metal particles produced by spraying the coating onto the substrate by means of a longitudinally extending coating die which is movable or moved at a relative speed relative to the substrate in a plasma zone, which is inside one of the coating nozzle

upstream electrode, a cold plasma with a plasma temperature less than 3000 K is generated and wherein in the coating nozzle by means of a carrier gas, a powder is introduced, which is carried by the plasma towards a front end outlet opening from the coating die, there emerges and strikes the substrate, wherein

a) a carrier gas is passed at least partially through a powder with a polymer shell before entering the plasma zone,

b) the powder is introduced into the coating nozzle with the aid of the carrier gas, c) the powder is carried by the carrier gas from the plasma in the direction of a front end outlet opening of the coating nozzle, exits there and strikes the substrate.

Furthermore, the present invention relates to the use of platelet-shaped particles, preferably of platelet-shaped metal particles, which have a

Polymer coating having an average thickness of less than 2 μηη, applying a coating to a substrate using cold plasma.

The generation of layers on substrates through the use of powders and cold atmospheric plasma requires an interaction of plasma and particles. While the parameters of the plasma are known to those skilled in the art, the requirements for the powder are mostly dictated by the application. This will be specific for certain applications

Materials needed. For example, the formation of conductive layers requires the use of powders of conductive materials.

The skilled person is therefore limited by the task of the application mostly in the choice of materials. However, it is free in the selection of powder parameters. An important parameter that determines the properties of the powder is the

Diameter of the powder particles. For a given powder usually can not be given a simple diameter, but the diameter has a distribution. This distribution is usually characterized by the specification of D values, for example the D50 value. These D values can be determined by means of

Laser granulometry can be determined for example with HELOS or CILAS devices. At the D ₅₀ value, 50% of the aforementioned are by means of laser granulometry volume-averaged particle size distribution below the specified value.

In this method, the metal particles can be measured in the form of a dispersion of particles. The scattering of the irradiated laser light is in

recorded according to the Fraunhofer diffraction theory by means of in conjunction with a HELOS or CILAS device according to

Evaluated manufacturer information. The particles are treated mathematically as spheres. Thus, the determined diameters always refer to the equivalent spherical diameter averaged over all spatial directions, irrespective of the actual shape of the metal particles. It determines the size distribution, which is calculated in the form of a volume average (based on the equivalent spherical diameter). This volume-averaged size distribution can be represented inter alia as a cumulative frequency curve, which is also called the cumulative frequency distribution. The cumulative frequency curve in turn is usually characterized simplifying by certain characteristics, z. B. the D50 or D90 value. By a D90 value is meant that 90% of all particles are below the specified value. At a D50 value, 50% of all particles are below the specified value.

The particle diameter determines in particular the specific surface area of the individual particle and thus also the total powder. By specific surface is meant the outer surface referred to the mass, which describes the surface per kilogram of the powder and is defined as follows:

Surface _r m ² _^

^S M ^{= -} M TTasse ^[~ krg

For an ideal sphere with the particle diameter dp, the specific surface is therefore obtained

_{Sm =Sm =} ⁶⁶ _{{ ^mm

d _P * p kg

It is known in the literature that nanoparticles, i. Particles with three

Dimensions smaller than 100 nm, due to a reduced melting point over the Mark macro material. Such nanoparticles have a very large surface area in relation to their volume. This means that they have far more atoms on their surface than larger particles. Since atoms on the surface are less binding partners available, as atoms in the core of the particle, such atoms are very reactive. For this reason, they can interact with particles in their immediate environment much more than macroparticles.

Since essentially the surface of the particles reacts with the plasma, the person skilled in the art knows that the increased surface area of smaller particles generally results in a significantly better melting behavior of the particles.

Thus, those skilled in the art will use small diameter particles for applications where higher melting metals and ceramic particles must be used. A disadvantage of such powders with a small particle diameter, however, is that they are difficult to fluidize, which also makes their promotion difficult. However, good eligibility is imperative for industrial application of the cold atmospheric plasma coating. A known to the expert advantageous device for applying a

Particulate coating is characterized in that the apparatus comprises a jet generator having an inlet for the supply of a flowing working gas and an outlet for a plasma jet guided by the working gas, the jet generator two having an AC or a pulsed one

DC voltage source connectable electrodes to form a

Discharge path along which the working gas is guided, the

Beam generator opening in the region of the discharge gap

Feed inlet, via which the plasma jet particles, preferably platelet-shaped particles, can be fed.

As the working gas of the device are supplied via the inlet ionizable gases, in particular pressurized air, nitrogen, argon, carbon dioxide or hydrogen. The working gas is previously cleaned so that it is free of oil and lubricant. The gas flow in a conventional jet generator is between 10 to 70 l / min, in particular between 10 to 40 l / min, at a

Speed of the working gas between 10 to 100 m / s, in particular between 10 to 50 m / s. The jet generator further comprises two, in particular coaxially spaced

mutually arranged electrodes which are connected to an AC voltage,

but in particular be connected to a pulsed DC voltage source. Between the electrodes, the discharge path is formed. The pulsed

DC voltage of the DC voltage source is preferably between 500 V to 12 kV. The pulse frequency is between 10 to 100 kHz, but in particular between 10 to 50 kHz.

Due to the pulsed operation of the DC voltage source, it can be assumed that no thermal equilibrium can form between the light electrons and the heavy ions. This results in a low temperature load of the injected platelet-shaped particles. The coating process with the jet generator according to the invention is preferably controlled such that the plasma jet of the low-temperature plasma in the core zone has a gas temperature of less than 900 degrees Celsius, but in particular of less than 500 degrees Celsius (low-temperature plasma).

By opening the feed opening in the region of the discharge gap between the electrodes of the jet generator, the particles reach a region in which a direct plasma excitation takes place through the plasma jet. By this measure, the energy input is maximized in the powder.

Preferably, the feed opening is located immediately adjacent to the outlet for the plasma jet in the region of the discharge path. However, if the feed is below the outlet of the device, which is basically possible, it is only an indirect

Plasma excitation by the gas-guided plasma jet, which is energetically unfavorable. In industrial use, the location of the powder feed into the plasma flame and the location where the powder is stored are spatially separated. Industrial operation requires the provision of certain amounts of powder, since otherwise, for example, an approximately continuous coating process is not feasible due to the time required for refilling the powder. A very close storage is not feasible for technical reasons, Therefore, the powder must be promoted over a certain distance. This explains the need to use powders with good pumpability.

However, such good conveyability is in powders with small

Particle diameters not given. However, such small particle diameters must be used as described for certain applications where refractory materials are used. In order to still allow a promotion of such powders, new conveyor units have been developed in the prior art. For this purpose, for example, vibrations are introduced into the powder or the powder is fluidized in vortex chambers and then conveyed. By means of such special conveyor units a promotion of fine powders is possible in principle. However, the conveyor units have disadvantages. On the one hand, these are complex in terms of equipment, so that they have to be serviced frequently. On the other hand, they often require complex control technology. Furthermore, they each require larger amounts of energy, which significantly worsen the economics of the overall process. For this reason, intensive work is being done on improving the delivery units. The inventors have now completely surprisingly found that this

Avoid delivery difficulties by sheathing the powder particles with a surrounding polymer shell, without adversely affecting the properties of the deposited layer. That an improvement of the flow properties through the application of

Modifications on the surface is possible, is known in the art. However, one skilled in the art avoids coating powder for use in cold plasma coating processes. As described, the application and its requirements specify the type of material of the powder. It follows that the Professional changes of the powder considered disadvantageous, since they lead in principle to changes in the chemical composition of the powder and thus the resulting layer. In particular, the person skilled in the art must assume that changes in the powder as impurities in the layer will affect its properties.

The inventors have now surprisingly found that modification of the powder with a surrounding polymer shell improves the conveyability without affecting the properties of the layer. In particular, the inventors have surprisingly found that the surrounding polymer shell is no longer present in the deposited layer, so that the quality of the layer is not affected.

By means of the method according to the invention, it is thus possible to modify poorly transportable powders by applying a surrounding polymer sheath so that good conveyability can be achieved without having to carry out a complex optimization of conveying units. As a result, the method according to the invention offers the advantage over the prior art that powders with particle sizes can be used on existing systems which can not be conveyed without the coating applied according to the invention with the powder conveyor in the system. As the application of the surrounding

Polymer shell on almost all powder materials is possible, the inventive method is a great advantage. The surrounded with a polymer shell particles of the method according to the invention are characterized in that the particles of the powder are surrounded by a closed shell of a crosslinked polymer. The advantage of using a crosslinked polymer is that the layer thickness of the surrounding shell can be minimized since the density of the polymer shell is maximized.

The average thickness of the surrounding shell is less than 2 μιτι, preferably less than 500 nm, more preferably less than 300 nm, most preferably less than 200 nm. The average thickness is on the other hand minimal 3 Nanometer (nm) is preferably 5 nm, particularly preferably 10 nm, very particularly preferably 15 nm.

To determine the thickness of the surrounding polymer shell, there are no measuring instruments in the prior art which can easily determine this value. A

Determination is therefore carried out by default by determining the thickness of the shell of a statistically sufficiently large number of particles surrounded by a polymer shell in SEM (scanning electron microscope) analyzes. For this purpose, the particles are dispersed, for example in a paint and then applied to a film. The film coated with the lacquer coated with a polymer shell is subsequently cut with a suitable tool so that the cut runs through the lacquer. Subsequently, the prepared film is introduced into the SEM such that the observation direction is directed perpendicular to the cutting edge. In this way, the particles are largely viewed from the side thereof, so that the thickness of the polymer layer can be easily determined. By default, the determination is made by marking the corresponding limits by means of a suitable tool such as the software packages supplied by the manufacturer as standard with the SEM devices.

For example, the determination can be carried out by means of a REM device of the Leo series of the manufacturer Zeiss (Germany) and the software Axiovision 4.6 (Zeiss, Germany). Of course, the thickness of the polymer shell surrounding the particles is not homogeneous over all particles. The fluctuation width of the polymer layer can be +/- 50% of the average thickness. The polymer layer can basically consist of all organic polymers known to the person skilled in the art. Preferably, it consists of polymerized

Plastic resin. Particularly preferably from polymerized acrylate resin. Most preferably, the polymer shell is made of polyacrlate or polymethacrylate. Of course, synthetic resin coatings consisting of e.g.

Epoxies, polyesters, polyurethanes, or polystyrenes, and mixtures thereof.

Under a surrounded polymer shell according to the invention is thereby a

Polymer coating of a polymer, in particular a synthetic resin understood, which is composed of a single layer, that is not made up of several recognizable substructures. The term crosslinked polymer shell denotes in the context of the invention that the proportion of monomers or uncrosslinked molecules in the shell less than 20 wt .-%, preferably less than 15 wt .-%, more preferably less than 10 wt .-% , Total mass of the shell.

According to a preferred embodiment of the invention, the polymer coating is carried out by direct Aufpolymerisierung of the monomers on the particles.

The shell can be constructed from one or more monomer units. It is preferably composed of at least two monomer units. Both

Monomer units are preferably acrylate or methacrylate groups, which are characterized in that they have at least two functional acrylate or methacrylate groups. In addition to the acrylate or methacrylate groups, the shell preferably additionally comprises organofunctional silane.

In addition to acrylate and / or methacrylate compounds, other monomers and / or polymers in the synthetic resin coating of the invention

MetaNeffektpigmente present. Preferably, the proportion of acrylate and / or methacrylate compounds including organofunctional silane at least 70 wt .-%, more preferably at least 80 wt .-%, even more preferably at least 90 wt .-%, each based on the total weight of

Resin coating. According to a preferred variant is the

Synthetic resin coating exclusively from acrylate and / or

Compounds methacrylates and one or more organofunctional silanes, wherein additionally additives such as corrosion inhibitors, colored pigments, dyes, UV stabilizers, etc., or mixtures thereof in the

Resin coating may be included. It is inventively preferred that the acrylate and / or

Methacrylate starting compounds with a plurality of acrylate groups and / or

Methacrylate each have at least three acrylate and / or methacrylate groups. With further preference these starting compounds may each also have four or five acrylate and / or methacrylate groups. The use of multifunctional acrylates and / or methacrylates allows the provision of metallic effect pigments with very good chemical resistance and higher electrical resistance. The using of

polyfunctional acrylates and / or methacrylates

Metallic effect pigments of the invention are not electrically conductive, which considerably extends the possible uses of metallic effect pigments. It is thus possible to use the metallic effect pigments according to the invention,

Apply metallic finishes to objects that are not electrically conductive, such as protective housings, insulators, etc.

It has surprisingly been found that already two or three acrylate and / or methacrylate groups per acrylate and / or methacrylate starting compound in

Compound with an organofunctional silane sufficient to a chemically highly resistant and electrically non-conductive resin layer on the

To produce metallic effect pigment.

The synthetic resin layer has, in particular at 2 to 4 acrylate and / or

Methacrylate groups per acrylate and / or methacrylate starting compound, surprisingly an extraordinary tightness and strength, without being brittle. As extremely suitable have 3 acrylate and / or

Methacrylate groups per acrylate and / or methacrylate starting compound proved. These mechanical properties, which are valuable in combination, make it possible to expose the metallic effect pigments according to the invention also to high shear forces, for example when pumping through pipelines, such as in a ring line, without damaging or detaching the metal effect pigments

Synthetic resin layer comes from the metallic effect pigment surface.

According to a further preferred embodiment, the weight ratio of polyacrylate and / or polymethacrylate to organofunctional silane is 10: 1 to 0.5: 1. Further preferred is the weight ratio of polyacrylate and / or polymethacrylate to organofunctional silane in a range of 7: 1 to 1: 1.

It has been shown that also, in terms of weight, deficit organofunctional silane to polyacrylate and / or polymethacrylate is sufficient to apply a firmly adhering to the metallic effect pigment surface and at the same time resistant to chemicals or highly corrosive environmental conditions resin layer.

According to a preferred embodiment of the invention, the

Metallic effect pigments of the present invention have a coating which are composed of at least two monomer components a) and b), wherein a) is at least one acrylate and / or methacrylate and b) at least one

organofunctional silane, which preferably has at least one free-radically polymerizable functionality.

Component a) preferably comprises polyfunctional acrylates and / or methacrylates, the corresponding monomers having di-, tri- or polyfunctional acrylate and / or methacrylate groups.

Examples of suitable difunctional acrylates a) are: allyl methacrylate, bisphenol-adimethacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol dimethacrylate,

Ethylene glycol dimethacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, diethylene glycol dimethacrylate, diurethane dimethacrylate, dipropylene glycol diacrylate, 1,12-dodecanediol dimethacrylate, ethylene glycol dimethacrylate, methacrylic anhydride, Ν, Ν-methylene-bis-methacrylamide, neopentyl glycol dimethacrylate,

Polyethylene glycol dimethacrylate, polyethylene glycol 200 diacrylate, polyethylene glycol 400 diacrylate, polyethylene glycol 400 dimethacrylate, tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate, tricyclodecanedimethanol diacrylate,

Tripropylene glycol diacrylate, triethylene glycol dimethacrylate or mixtures thereof.

As higher-functionality acrylates can z. B.

Pentaerythritol triacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, tris (2-hydroxyethyl) isocyanurate triacrylate, pentaerythritol tetraacrylate,

Dipentaerythritol pentaacrylate or mixtures thereof.

Particular preference is given to trifunctional acrylates and / or methacrylates. Acrylates which are very useful in the present invention include dipentaerythritol pentaacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, tris (2-hydroxyethyl) isocyanurate triacrylate, 1,6-hexanediol dimethacrylate, or the like

Mixtures proved.

As organofunctional silanes b) according to the invention, for example

(Methacryloxymethyl) nnethyldinnethoxysilan, methacryloxymethyltrimethoxysilane, (methacryloxymethyl) nnethyldiethoxysilan, methacryloxymethyltriethoxysilane, 2- Acryloxyethylmethyldimethoxysilan, 2-Methacryloxyethylthmethoxysilan, 3- acryloxypropylmethyldimethoxysilane, 2-Acryloxyethyltrimethoxysila [pi], 2-methacryloxyethyltriethoxysilane, 3-Acryloxypropylthmethoxysilan, 3- Acryloxypropyltripropoxysilan, 3-methacryloxypropyltriethoxysilane, 3 Methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriacetoxysilane, 3-methacryloxypropymethyldimethoxysilane, vinyltrichlorosilane, vinyltrimethoxysilane, vinyldimethoxymethylsilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, vinyltriacetoxysilane, or mixtures thereof.

Particularly preferred are acrylate and / or methacrylate-functional silanes.

In certain embodiments of the present invention, the

organofunctional silane preferably selected from the group consisting of 2-methacryloxyethyltrimethoxysilane, 2-methacryloxyethyltriethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane,

(Methacryloxymethyl) methyldimethoxysilane, vinyltrimethoxysilane and their

Mixtures.

The aforementioned compounds as well as other suitable monomers useful in the present invention are described, for example, by Degussa AG, Frankfurt, Germany; Röhm GmbH & Co. KG, Darmstadt, Germany; Sartomer Europe, Paris, France; GE Silicons, Leverkusen, Germany or Wacker Chemie AG, Munich, Germany.

The synthetic resin layer of the particles preferably to be used according to the invention, preferably metallic effect pigments, preferably has an average layer thickness in a range from 20 nm to 200 nm, more preferably from 30 nm to 100 nm. According to a further variant of the invention, the average layer thickness is in a range of 40 to 70 nm. Surprisingly enough, the metallic particles preferably to be used according to the invention are preferably sufficient

Metallic effect pigments, extremely low average layer thicknesses from around the

To protect against aggressive environmental conditions very sensitive metal cores of these pigments reliable. In particular it comes with the

indicated average layer thicknesses to no significant deterioration of gloss or color of the metal cores through the resin layer.

For the production of the polymer shell, the powder particles are preferably initially pre-loaded with a functional group-carrying silane, which is used as

Adhesion promoter for the polymer shell is used. The functional group is more preferably acrylate or methacrylate groups.

According to one embodiment of the invention, the powder has particles with a size distribution with a D50 value from a range of 1 to 150 μιτι on. According to a further preferred embodiment, the size distribution between 1, 5 μιτι and 100 μιτι. According to a very preferred embodiment, it is between 2 μιτι and 50 μιτι. The measurements can be carried out, for example, using the particle size analyzer HELOS from Sympatec GmbH, Clausthal-Zellerfeld, Germany. The dispersion of a dry powder can take place here with a dispersion unit of the Rodos T4.1 type at a primary pressure of, for example, 4 bar. Alternatively, the size distribution curve of

Particles can be measured, for example, with a device from the company Quantachrome (device: Cilas 1064) according to the manufacturer's instructions. For this purpose, 1, 5 g of the particles are suspended in about 100 ml of isopropanol, 300 seconds in an ultrasonic bath (device:

Sonorex IK 52, Fa. Bandelin) treated and then by means of a

Pasteur pipette into the sample preparation cell of the measuring device and measure several times. From the individual results are the

resulting average values formed. The evaluation of the scattered light signals is carried out according to the Fraunhofer method. The material constituting the powders may be a metal, a non-metal, a polymer or an oxide.

Preferably, the material is a metal or a mixture of at least two metals or an alloy consisting of at least two metals. The degree of purity of the individual metals is preferably more than 70 wt .-%, more preferably more than 90 wt .-%, more preferably more than 95 wt .-%, each based on the total weight of the metal, alloy or mixture. To produce the powders, the metal, the metal mixture or metal alloy can be melted under heat, for example, and then converted to powder by atomization or by application to rotating components. Such produced metallic powder or metal powder have, for example, a particle size distribution with an average size (D50 value) in the range of 1 to 100 μιτι, preferably from 2 to 80 μιτι on. The particle or particle shape of the generated metallic powder is preferably approximately spherical. However, the powder may also have particles which are irregularly shaped and / or in the form of needles, rods, cylinders or platelets.

In the case of metallic particles, these may consist, for example, of aluminum, zinc, tin, titanium, iron, copper, silver, gold, tungsten, nickel, lead, platinum, silicon, further alloys or mixtures thereof. According to a variant of the method according to the invention are aluminum, copper, zinc and tin or

Alloys or mixtures thereof are particularly preferred. In the case of non-metallic particles, for example, these may consist of oxides or hydroxides of the metals already mentioned or of other metals, furthermore the particles may consist of glass or sheet silicates such as mica or bentonites. In addition, the particles may consist of carbides, silicates, nitrides, phosphates and sulfates. The recovery and processing for the process of suitable particles may also be by other means (e.g.

Crystallization, drawing, etc. s. Breeding methods, or by means of conventional grazing and flooding etc.). The particles may also be organic and inorganic salts. Furthermore, the particles may consist of pure or mixed homo-, co-, block- or prepolymers or plastics or mixtures thereof, but also be organic pure or mixed crystals or amorphous phases.

The particles can also consist of mixtures of at least two materials, wherein basically all mixing ratios of the two materials are possible. Preferably, the amount of material that is the lowest in mass is more than 2 percent by weight, based on the total weight of the particles.

During the coating process, layers with the highest possible packing density should in principle be produced, since in most cases they have ideal application properties. The highest possible packing density is synonymous with a layer that is as similar as possible to a closed, non-particulate layer, ie a layer that corresponds to the ideal base material. Such layers are sought since they have the best physical and chemical properties. For example, silver traces show an increasing resistance as the packing density decreases.

On the other hand, a low packing density results especially when the particles retain their shape and structure as far as possible during the coating process and are still present as individual particles, in particular in the resulting layer. The particles tend to show such behavior if they consist of higher-melting metals (melting point> 500 ° C) and non-metallic material. The energy of the plasma activates such particles only on their surface, whereby the shape of the particles as such remains in the layer formed on the substrate. The inventive method can be used to coat a variety of

Substrates are used. Substrates may be, for example, metals, wood, plastics or paper. The substrates can be present in the form of geometrically complex shapes, such as components or finished goods but also as a film or sheet. The applications for the inventive method are also very diverse. With the method, for example, layers for applications for

Production of optical and electromagnetic reflective or

absorbent, electrically conductive, semiconductive or insulating layers, diffusion barriers for gases and liquids, sliding layers, wear and corrosion protection layers and layers for influencing the

Surface tension as well as the adhesion mediation are made. Conductive layers produced by the process can

For example, be used to produce Heizleiterbahnen that are used for heating substrates. Furthermore, such conductive layers can also be used as shielding, as electrical contact and as antenna, in particular RFID (Radio Frequency Identification) antennas. Sensor surfaces (for example for HMI interfaces, control panels etc)

EMC / EMI shielding applied to cable / housing etc.

Electrical contacts generally across different materials.

Encapsulation (e.g., populated wafers) The layers may be applied in the form of laminar layers which cover the substrate over a large area, preferably greater than 70% of the area of the substrate. The layers can also be applied in the form of patterns, which are preferably adapted to the desired functionality. The

Generation of geometric patterns, for example, by the

Use of masks done.

The device for carrying out the method will be explained in more detail below with reference to the figures. 1 shows a schematic representation of an embodiment of a

beam generator according to the invention and

Figure 2 is an enlarged view of the beam generator of Figure 1 in

Area of the outlet. Figures 3 and 4 SEM photographs of a steel sheet applied

Copper layer.

The beam generator (1) according to the invention for generating a plasma jet (2) of a low-temperature plasma comprises two electrodes (4, 5) arranged in the flow of a working gas (3) and a voltage source (6) for generating a pulsed direct voltage between the electrodes (4, 5). , The first electrode (4) is designed as a pin electrode, while the spaced-apart second electrode (5) is designed as an annular electrode. The distance between the tip of the pin electrode (4) and the ring electrode (5) forms a discharge path (16). A jacket (7) of electrically conductive material is arranged concentrically with the pin electrode (4) and insulated from the pin electrode (4). At the, the annular electrode (5), opposite end face of the jet generator (1), the working gas (3) via an inlet (21) is supplied. The inlet (21) is located on a front side on the hollow cylindrical jacket (7) patch, the pin electrode (4) holding sleeve (22) made of electrically insulating material. At the

opposite to the end face of the jacket (7) tapers nozzle-shaped to an outlet (8) for the plasma jet (2).

Immediately adjacent to the in the axial direction of the jet generator (1)

extending outlet (8) is transverse to the longitudinal extent of a feed opening (9) through which the plasma jet (2) platelet-shaped particles (10) can be fed. The feed opening (9) of the jet generator is connected for this purpose via a line (12) with a swirl chamber (1 1), in the

platelet-shaped particles (10) are stored. The vortex chamber (1 1) is at most up to a maximum level (13) with the platelet-shaped

Particles (10) filled. Below the maximum level (13) opens in the vortex chamber (1 1) an inlet (23) for a carrier gas (14) under a

compared to the ambient pressure increased pressure is injected into the particle supply. As a result, the particles (10) in the space above the maximum Fluid level (13) swirled and pass through an outlet (15), the line (12) and the feed opening (9) in the discharge path (16) of the jet generator (1).

As can be seen in particular from the enlargement in FIG. 2, the platelet-shaped particles (10) transversely to the propagation direction of the plasma jet (2) into a core zone (17) of the plasma jet (2), in which a temperature of less than 500 degrees Celsius prevails (low-temperature plasma ).

The voltage source (6) increases, during each pulse, the voltage applied between the electrodes (4, 5) until, between the electrodes (4, 5), the ignition voltage for the formation of an arc is applied between the electrodes (4, 5).

Due to the conductive jacket (7), discharges also occur in the direction of the inner circumferential surface, as indicated by the dotted lines in FIG. When the ignition voltage is reached, the discharge path (16) between the electrodes (4, 5) becomes conductive. The voltage source (6) is preferably designed such that it generates a voltage pulse with an ignition voltage for the

Arc discharge and a pulse frequency generated, which can extinguish the arc between two consecutive voltage pulses respectively. As a result, there is a pulsed gas discharge in the plasma jet (2). The pulse frequency is preferably in a range between 10 kHz to 100 kHz, in the illustrated embodiment at 50 kHz. The voltage of the voltage source is a maximum of 12 kV. As working gas (3) compressed air is used, with 40 l / min are supplied in the normal operating condition. Provided that with the help of the beam generator (1) deviating from the illustrated

Embodiment not only a punctiform coating on the substrate (20) is to be produced, in one embodiment of the invention, the possibility that the plasma jet (2) and the substrate (20), at least temporarily moved during the application of the coating relative to each other. The

Relative movement can be effected by moving the substrate (20), for example on a movable table in the horizontal plane. Alternatively, the beam generator (1) is arranged on a movable at least in a plane parallel to the substrate (20) plane, so that the generator with a defined Speed is movable relative to the substrate. By the relative movement can be webs or even full-surface coatings of the substrate produce.

LIST OF REFERENCE NUMBERS

No. Designation No. Designation

1 jet generator 22 sleeve

2 plasma jet 23 inlet carrier gas

3 working gas 24 powder-gas mixture

4 electrodes 25 conveying gas

5 electrodes 26 core area of the discharge /

plasma space

6 Voltage source 27 Supply area

7 coat 28 plasma

8 outlet 29 nozzle

9 Infeed opening 30 Earth connection

10 particles 31 generator

1 1 vortex chamber 32 electrical line

12 line 33 core zone plasma

13 Maximum level 34 Activated particles

14 carrier gas 35 atmospheric plasma

15 outlet 36 layer

16 discharge gap 37 particles

17 core zone 38 supply line

18 powders

19 coating

20 substrate

21 inlet working gas

Embodiments The present invention will be illustrated by, but not limited to, the following examples. Used measuring methods:

Particle size:

The determination of particle size was made using a Cilas 1064 instrument using the standard measurement software.

Example 1: Production of Spherical (Spherical) Aluminum Powder

In an induction crucible furnace (Induga, Cologne, Germany), about 2.5 tons of aluminum ingots (metal) were continuously introduced and melted. in the

so-called forehearth, the molten aluminum was liquid at a temperature of about 720 ° C. Several nozzles, which work according to an injector principle, dipped into the melt and atomize the aluminum melt vertically upwards. The atomizing gas was compressed in compressors (Kaeser, Coburg, Germany) up to 20 bar and heated in gas heaters up to about 700 ° C. The aluminum powder produced after spraying / atomization solidified and cooled down in the air. The induction furnace was integrated in a closed system. The atomization was carried out under inert gas (nitrogen). The deposition of the aluminum powder was carried out first in a cyclone, wherein there deposited powdered aluminum powder had a D50 of 14-17 μιτι. For further deposition served in a multi-cyclone, wherein the deposited in this powdered aluminum powder had a D50 of 2.3-2.8 μιτι possessed. The gas-solid separation was carried out in a filter (Fa. Alpine, Thailand) with metal elements (Pall). Here, as the finest fraction, an aluminum powder having a d10 of 0.7 μm, a d50 of 1.9 μm and a d90 of 3.8 μm was obtained.

Example 2 Production of Metallic Platelet-shaped Particles

Marriage:

In a pot mill (length: 32 cm, width: 19 cm) were 4 kg of glass beads

(Diameter: 2 mm), 75 g of the finest aluminum powder, 200 g of white spirit and 3.75 g of oleic acid. It was then ground for 15 hours at 58 rpm. The Product was separated from the grinding balls by rinsing with white spirit and then screened in a wet sieving on a 25 μηη sieve. The fine grain was largely freed of white spirit via a suction filter (about 80%).

Solids).

Example 3: Preparation of non-metallic platelet-shaped particles

(Aluminum hydroxide) by oxidation of metallic platelet-shaped particles (aluminum)

In a 5 L glass reactor, 300 g of a shaped aluminum powder described in Example 2 were dispersed in 1000 ml of isopropanol (VWR, Germany) by stirring with a propeller stirrer. The suspension was heated to 78 ° C. Subsequently, 5 g of a 25% strength by weight ammonia solution (VWR, Germany) were added. After a short time a strong evolution of gas could be observed. Three hours after the first addition of ammonia, another 5 g of 25% strength by weight ammonia solution was added. After another three hours, again 5 g of 25 wt .-% - ammonia solution was added. The suspension was further stirred overnight. The next morning, the solid was separated by means of a suction filter and dried in a vacuum oven for 48 h at 50 ° C. A white powder was obtained. This powder was subsequently characterized. First, particle size and zeta potential as a function of pH were studied. The pH was adjusted by means of 1, 0 M NaOH or 1, 0 M HCl. The results are shown in Figure 2. At low as well as at high pH the zeta potential shows a maximum and the particle diameter a minimum. An XRD analysis of the material is shown in Figure 3. From this, a composition of about 33 wt .-% boehmite (AIOOH) and 67 wt .-% gibbsite (Al (OH) ₃ ) are derived.

Example 4: Preparation of non-metallic platelet-shaped particles

(Alumina) by thermal treatment of non-metallic

platelet-shaped particles (aluminum hydroxide) 500 g of a material prepared according to Example 3 were heated for 10 minutes in a rotary kiln (Nabertherm, Germany) to 1 100 ° C. There were obtained 335 g of a white powder. This was examined as described. The results are shown in Figures 4 and 5. In contrast to the uncalcined material, the particle diameter is slightly larger and the zeta potential is positive throughout the entire pH range. The XRD analysis shows theta-Al ₂ O ₃ .

Example 5-8: Coating of particles with an acrylate shell

The materials prepared in Examples 1 -4 were surrounded in a further step with a shell of a crosslinked acrylate. The following sets of approaches were used.

Name Starting material Solvent Composition

product

Example 5 Example 1 Ethanol 6.6 g

(Aluminum powder)

Polymer coating 93.4 g

aluminum shot

Example 6 Example 2 Ethanol 6.3 g

polymer coating

(Platy

Aluminum) 93.7 g

Flaky

aluminum

Example 7 Example 3 Ethanol 6.1 g

Polymer coating non-metallic

platelet-shaped 93.9 g non-metallic particles

platy

particles

Example 8 Example 4 Ethanol 6.2 g non-metallic polymer coating

platelet-shaped 93.8 g

Particles metallic

platy

particles

In each case, 100 g of the product from Examples 1-4 were dispersed in 525 g of ethanol, resulting in a 16% strength by weight dispersion. Subsequently, 0.65 g of methacryloxypropyltrimethoxysilane (MEMO) was added and stirred for 1 h at 25 ° C and 3 h at 75 ° C. Subsequently, at 78 ° C., 100 ml of a solution of 6 g of trimethylolpropane trimethacrylate (TMPTMA) and 0.6 g of dimethyl 2,2'-azobis (2-methylpropionate) (trade name V 601; available from WAKO Chemicals GmbH, Fuggerstrasse 12, 41468 Neuss) in ethanol for 5 h. Subsequently, stirred for 16 h at 72 ° C, the reaction mixture was filtered off and isolated as a paste. The resulting pastes were dried under vacuum with a slight inert gas at 100 ° C and then sieved with 71 μιτι mesh size.

Example 9 Production of Polyacrylate-Coated, Metallic Particles Tin particles or copper particles in paste form were used to prepare a 35

W .-% dispersion dispersed in 600 g of ethanol. 100 ml of a solution of 0.5 g of dimethyl 2,2'-azobis (2-methylpropionate) (trade name V 601, available from WAKO Chemicals GmbH, Fuggerstrasse 12, 41468 Neuss), 1 g of methacryloxypropyltrimethoxysilane, were subsequently added over a period of 1 hour (MEMO) and 10 g of trimethylolpropane trimethacrylate (TMPTMA) in white spirit.

The mixture was then stirred for a further 15 h at 75 ° C, the reaction mixture filtered off, isolated as a paste and dried under reduced pressure.

Example metal D ₅ o

9-1 copper grit 25 μηη

9-2 copper flakes 35 μηη

9-3 copper grit 9 μηη 9-4 tin grit 28 μηη

Example 10: Low Temperature Plasma Coating

The coated particles were applied by means of a Plasmatron system from Inocon, Attnang-Puchheim, Austria, argon and nitrogen being used as ionizable gases. Standard process parameters were used.

Examples 9-1 to 9-4 were applied to aluminum sheets, steel sheets and wafers. This showed a very uniform application of the powder, a slight overspray, a good adhesion of the layer to the surface and a color of the coating, which can be concluded with a small amount of oxidation. This was also confirmed in subsequent SEM images. Exemplary images of the spherical copper grit coating according to Example 9-1 can be found in FIGS. 3 and 4. For example, FIG

Detecting connection to the surface. Figure 4 shows the surprisingly uniform distribution of the individual particles in relation to the size of the individual particles (D ₅₀ = 25 μm). Attempts to apply uncoated particles by means of the coating system using a low-temperature plasma resulted in no useful coatings. In particular, hereby could not coherent

Coating can be achieved. Surface agglomerates showed no appreciable binding to the substrate surface.

Claims

claims

1 . Method for applying a coating to a substrate below

Use of cold plasma,

characterized,

the method comprises the following steps:

(a) introducing particles provided with a polymer coating into a cold plasma having a plasma temperature of less than 3000 K, which is directed onto a substrate to be coated;

(b) depositing the particles activated in the cold plasma in step (a) on the substrate.

2. The method according to claim 1,

characterized,

in that the cold plasma is generated in a coating nozzle and the particles are introduced into the coating nozzle via carrier gas, the coating nozzle and the substrate being movable relative to one another. 3. The method according to claim 1 or 2,

characterized,

the average layer thickness of the polymer coating is less than 2 μm. 4. Method according to one of the preceding claims,

characterized,

that the cold plasma is generated by applying a pulsed DC voltage or AC voltage to an ionizable gas.

5. The method according to any one of the preceding claims,

characterized,

that the particles are platelet-shaped particles.

Method according to one of claims 2 to 5,

characterized,

that the carrier gas at a flow rate through a

Container in which the particles are stored as a powder, is passed, so that the powder is at least partially fluidized to generate a powder dust and powder dust is introduced into the coating die.

Method according to one of claims 2 to 6,

characterized,

that the carrier gas flows through the coating nozzle with a volume flow from a range of 1 Nl / min to 15 Nl / min.

8. The method according to any one of the preceding claims,

characterized,

the cold plasma is generated under pressure and applied to the substrate in a range of 0.5 10 ⁵ - 1.5 x 10 ⁵ Pa.

9. The method according to any one of the preceding claims,

characterized,

the average thickness of the polymer coating is less than 300 nm.

10. The method according to any one of the preceding claims,

characterized,

the polymer coating is a polymerized (meth) acrylate resin. 1 1. Method according to one of the preceding claims,

characterized;

that the particles are metal particles and the metals from the group consisting of aluminum, zinc, tin, titanium, iron, copper, silver, gold, tungsten, nickel, lead, platinum, silicon and alloys thereof and mixtures thereof, to be selected.

12. The method according to any one of claims 1 to 10,

characterized,

that the polymer-coated particles are selected from the group consisting of

Oxides, carbides, silicates, nitrides, phosphates, sulfates and mixtures thereof are selected.

13. The method according to any one of the preceding claims,

characterized,

the substrate is selected from the group consisting of metals, plastics, paper, biological materials, glass, ceramics and mixtures thereof. 14. Coating on a substrate, obtainable by a method according to one of the preceding claims.

15. The use of platelet-shaped particles having a polymer coating with an average thickness of less than 2 μηη, when applying a coating to a substrate using cold plasma.