WO2019238347A1 - Method for coating a substrate - Google Patents

Abstract

The invention relates to a method for coating a substrate (18), comprising the application of a sol gel layer (S) onto the substrate (18) and the curing of the sol gel layer (S) applied onto the substrate (18), in which it is proposed that the sol gel layer (S) is provided with particles (P) from an atmospheric plasma beam (AP) that is directed onto the substrate (18) before, during and after the application of the sol gel layer (S) and contains the particles (P). After the application of the sol gel layer (S), the sol gel layer (S) is cured by irradiation with an atmospheric plasma beam (AP) directed onto the sol gel layer (S). The present invention enables a method for producing durable, hard, corrosion-, abrasion-, and wear-resistant coatings having a biocidal effect, which can also be used economically.

Description

Process for coating a substrate

The invention relates to a method for coating a substrate, which comprises the application of a sol-gel layer to the substrate and the curing of the sol-gel layer applied to the substrate, according to the preamble of claim 1.

Public transport (buses, trains, planes) are the main transmission points for bacteria and viruses due to the close contact between passengers. Studies showed that public transport users were at least six times as likely to get influenza-related respiratory infections. In addition to rhinoviruses, rota- / noro-viruses (triggers of diarrhea) are mainly transmitted in crowds of people. In addition to viral infections, bacterial infections with E. coli, Klebsiella _r Proteus, Staph. Haemoloticus and saprophyticus, which cause inflammation of the intestines, ears and bladder, are often transmitted in public transport. Based on aircraft, this led to widespread use of HEPA filters in air conditioning and circulating air systems, which was able to significantly minimize the risk of droplet infection, but showed a shift towards smear infection via the hands and subsequent transport to the mucous membranes. Bacteria and viruses are mainly found on seats, handles, buttons / switches, braille braille signs and folding tables, although nosocomial antibiotic-resistant staphylococcal types are also increasingly being found. The transfer is most efficient over hard, non-porous surfaces, whereby up to 60% of all people have high densities of faecal bacteria on their hands due to the lack of access to hand hygiene during the "journey". Detailed studies on the transfer of various pathogens (ie disease-causing bacteria , Viruses, spores) show that 100% of E. coli, Salmonella spp Staph. Aureus, 90% of C. albicans, 61% of the rhinoviruses, 22-33% of the

Hepatitis A viruses and 16% of rotaviruses are transmitted across surfaces. Once transferred, bacteria and viruses - depending on the type - usually survive for several days to years even on dry surfaces. In the end, studies showed that due to the high passenger density, even daily cleaning has no influence on the microbes. Surfaces pretending to be clean are particularly at risk, for example stainless steel has no antibacterial / antiviral effect.

Therefore, the creation of antibacterial surfaces was tried. For example, Ti02 with a photocatalytic effect has been integrated into organic coatings, with the service life being very limited due to the abrasive stress. Inorganic vacuum coatings would be significantly more wear-resistant, but are technically difficult and too expensive for large areas. Another alternative is the "nickel plating" (Ni-Sn matrix with Ti02 particles), which is problematic for nickel allergy sufferers and, moreover, can no longer be applied without disassembly. The latter is due to the long service life (up to 35 Years) is particularly important in order to be able to retrofit existing means of transport.

It is therefore the aim of the invention to provide a process for the permanent, hard, corrosion, abrasion and wear-resistant coating of a substrate with a biocidal effect, which is also subsequently and repeatedly economically usable.

This goal is achieved by the features of claim 1. Claim 1 relates to a method for coating a substrate, which comprises applying a sol-gel layer to the substrate and curing the sol-gel layer applied to the substrate, according to the invention It is provided that the sol-gel layer is provided with particles with an atmospheric plasma jet which is directed onto the substrate and contains the particles before, during or after the application of the sol-gel layer, and after the application of the sol-gel layer. Layer the hardening of the sol-gel layer takes place by irradiation with an atmospheric plasma beam directed onto the sol-gel layer. The method according to the invention thus provides for a combination of thick-film and thin-film technologies by means of sol-gel layer application and atmospheric plasma. In this way, as will be described in more detail, a thick-film system can be realized which can be provided with a high biocide particle density in a wear-resistant, also biocidal matrix and which shows controlled degeneration and corrosion behavior through corrosion inhibitors and reservoir-forming intermediate layers.

Techniques for sol-gel layer application are well known. Using sol-gel synthesis, inorganic or organic-inorganic (hybrid polymer) coatings can be produced from colloidal dispersions. Sol-gel layers are mainly applied to 3D surfaces by dipping or spraying. The coating is finished in a conventional manner by curing at elevated temperature thermally and / or under UV radiation photochemically (with the addition of photoinitiators).

According to the invention, however, the applied sol-gel layer is cured by means of an atmospheric plasma jet. In the case of atmospheric pressure plasma, the pressure in the plasma corresponds to the surrounding atmospheric pressure, which means that, in contrast to the low / high pressure plasma, no cost-intensive reaction vessel (eg vacuum chamber) is necessary. Such plasmas can through nozzles (plasma jet), dielectric Barrier discharge (DBD), corona discharge, electrostatic filters and ionizers are produced technically, only the first two being significant for the technical production of coatings according to the invention. In the case of plasma nozzles, a high-frequency ignition pulse (10 kV) is used to generate an arc and to maintain the voltage at a constant current, through which the working gas flows and is ionized. The outlet takes place at the nozzle head as thermal hot gas plasma, which is at ground potential and thus largely retains potential-carrying parts of the plasma stream. The internal structure of the plasma nozzle and the excitation voltage and frequency used define the achievable plasma properties such as density or energy. In principle, however, a lower temperature load for the substrate and thus the use of, for example, plastics as a substrate are made possible. Alternatively, by means of appropriate electrode and nozzle shape and gas flows, a very large working distance compared to the prior art (up to 120 mm vs. 30 mm) with an enlarged plasma jet diameter (up to 55 mm vs. 20 mm) can be used, which makes the Allows the inventive method for 3D surfaces.

According to the invention, the atmospheric plasma jet is also used to provide the sol-gel layer with particles with an atmospheric plasma jet directed before, during or after the application of the sol-gel layer. The particles are preferably biocidal particles. In the recent past, metals have come into focus for the achievement of biocidal effects, although their tendency to form resistance is low. Currently silver is predominantly used, which has a wide spectrum of antimicrobial activity for a large part of all nosocomial bacteria, germs, spores, fungi and viruses. Since silver is also very well tolerated by the body in vivo, non-allergenic and therefore optimal for surfaces of Suitable implants and surgical instruments, its large-scale use in the non-clinical area to avoid the development of resistance is increasingly viewed critically or is also restricted by law. In the context of the present invention, therefore, biocidal particles which contain copper, zinc or tungsten and / or their oxides, metal salts or titanium dioxide are preferably proposed. These particles can be supplied as powdered precursor materials in the form of suitable metal compounds to the plasma jet by means of a carrier gas, which subsequently melt in the plasma jet and are accelerated in the molten or pasty state by the volume expansion of the plasma jet and deposited on the substrate to be coated. This process can take place before, during or after the application of the sol-gel layer to the substrate, the goal in each case in the production of a primer layer or covering layer for the sol-gel layer, or in the incorporation of the particles into the sol -Gel layer as well as a combination of these measures can exist. The invention can also be used more broadly in that the particles are nanoparticles, microparticles or fibers which have the electrical conductivity, thermal conductivity, piezoelectric properties, magnetic properties, optical reflection / transmission / emission properties, optoelectric properties , biological-functional properties or decorative-colored properties of the sol-gel layer either as storage or change.

According to one embodiment of the invention, the sol-gel layer is applied by means of a sol-gel matrix which already contains quaternary ammonium salts with a biocidal action, for example Q-POSS, in order to further increase the biocidal effectiveness of the coating. It can also be provided that the sol-gel layer application by means of a sol-gel matrix which contains cerium in order to increase the corrosion resistance of the hardened sol-gel layer.

After application of the sol-gel layer provided with biocidal properties, the sol-gel layer is cured according to the invention by irradiation with an atmospheric plasma jet directed onto the sol-gel layer. Curing can be carried out with the same plasma generator with which the sol-gel layer was also provided with particles, only the supply of the precursor material for the introduction of the particles into the plasma beam being prevented. The hardening of the sol-gel layer by means of atmospheric plasma jet can be carried out more quickly than with conventional thermal treatment, so that higher layer thicknesses can be achieved, and in particular the production of a multilayer structure of the applied layer is economically possible, in that several sol-gel layers each after Curing can be applied to the substrate one after the other by the atmospheric plasma. The atmospheric plasma has also proven to be extremely suitable for curing a sol-gel layer. Due to the high, but briefly acting temperatures of the atmospheric plasma - the core temperature of an atomic plasma is around 5000-10,000 ° C - a sol-gel layer can be cured quickly and without cracks even with thick layers. In addition, the UV radiation generated in the plasma can also be used for curing, in particular when photoinitiators are present in the sol-gel layer. Through the use of atmospheric pressure processes according to the invention, namely the sol-gel layer application and the atmospheric plasma treatment, continuous processes can also be realized by moving the substrate from one location of the sol-gel layer application to the plasma head. Simultaneous surface treatment of the substrate with sol-gel layer application and plasma treatment is also conceivable. It is also it is also conceivable to cure only selected partial areas of the applied sol-gel layer with the atmospheric plasma and to remove the remaining areas of the sol-gel layer in order to coat only selected partial areas of the substrate. The use of atmospheric pressure processes according to the invention also ensures economic feasibility.

It is also preferably proposed that the particles be admixed as a coating material with the atmospheric plasma jet which causes the hardening of the sol-gel layer. The coating material can in turn be applied with the same plasma generator, with the plasma jet merely being supplied with a suitable precursor for the desired coating. It is preferably a polymerizable precursor. By means of plasma polymerization processes under atmospheric pressure, SiO 2, TiO 2, SnO _x , CrO _x , diamond-like carbon and polymer layers can be produced in a known manner. The process proceeds from the formation of radicals in the gas phase through collision with surrounding particles and the very intense UV radiation in the plasma, which enables polymerization. The structure of the plasma polymers is close to that of conventional polymers, especially with low energy input per precursor monomer. These precursors (eg HMDSO, TEOS, TiC14, C2H2, etc.) can be added in the highly ionized discharge zone or only in the quasi-neutral plasma zone without interaction of electrons and ions. A special position is the "atmospheric plas a liquid deposition", where droplets are sprayed into the plasma instead of precursor vapor, which prevents damage to fragile organic molecules by ionization. The use of an atmospheric plasma jet according to the invention thus enables curing and surface modification because of the intense (UV) radiation also the production of polymer and oxide ceramic thin layers, whereby the significantly larger working distance gives decisive advantages in the use of 3D objects. The (simultaneous) use of precursors for layer deposition is very advantageous for single-step functionalization during curing, i.e. the use of intermediate layers to increase toughness, hardness or wear resistance and as permeation barrier layers to increase corrosion protection by minimizing the Nanoporosity. Alternatively, the coating material can also be metallic or ceramic particles.

In a corresponding manner, a coating of a substrate with a biocidal effect is proposed, which comprises a hardened sol-gel layer containing copper, zinc, tungsten and / or their oxides, metal salts, or titanium dioxide, and a layer consisting of a polymerized and by means of a atmospheric plasma jet polymerizable precursor is formed. The precursor polymerizable by means of an atmospheric plasma jet is preferably HMDSO or TEOS. The method according to the invention can be expanded in that a multilayer structure is carried out with the aid of a sequence of sol-gel layer applications and irradiation with the atmospheric plasma jet. Thanks to the multilayer structure, high layer thicknesses can be achieved, which maintain the functionality of the biocidal coating over a long period of time. Furthermore, a coating of a substrate with a biocidal effect is proposed, which comprises a hardened sol-gel layer containing copper, zinc, tungsten and / or their oxides, metal salts, or titanium dioxide, and a layer which is formed from metallic or ceramic particles , The invention is explained in more detail below on the basis of exemplary embodiments with the aid of the attached figures. Here show the

Fig. 1 is a sectional view through a possible embodiment of a plasma generator for curing the sol-gel layer and for supplying the biocidal particles and the

Coating material,

Fig. 2a is a schematic representation of a possible

Execution of the method according to the invention,

2b is a schematic representation of a further possible embodiment of the method according to the invention,

3a shows a schematic representation of a coating produced by the method according to the invention, and the

3b shows a schematic representation of a multilayer structure produced by the method according to the invention.

1, a possible embodiment of a plasma generator 1 for curing a sol-gel layer S and for supplying particles P as deposits or deposits of the sol-gel layer S is described. The device comprises a plasma generator 1, which has a cathode 2 and an anode 5. The cathode 2 is cylindrical and has at its free end a conical end region 3 which, in the exemplary embodiment shown, projects into an outlet channel 4 for the plasma jet AP. The anode 5 is arranged coaxially with the cathode 2, the cathode 2 and the anode 5 being connected to a controllable voltage source 6. A direct voltage in the range of 10-30 V at a current of 60-500 A is applied between the cathode 2 and the anode 5. The electrical power of the plasma generator moves in the Range of 600-10000 W. The inside of the cathode 2 can optionally be provided with cathode cooling (not shown in FIG. 1). Furthermore, coolant channels 10 are provided in the jacket body of the plasma generator 1, which are connected to a coolant source 11 and cool the plasma generator 1.

The cathode 2 and the anode 5 delimit a working gas channel 7, which is connected to a controllable working gas source 8. For example, argon, helium, nitrogen or primarily inert mixed gases such as argon-hydrogen mixed gases or also air can be used as the working gas. The working gas channel 7 opens into the outlet channel 4, which opens into the surrounding atmosphere via an outflow opening 9. In operation, a voltage is applied to the cathode 2 and the anode 5 which is selected to be sufficiently high to ignite an arc between the tapering end region of the cathode 2 and the anode 5 surrounding the cathode 2. This electrical discharge ionizes the working gas flowing through the working channel 7, which subsequently flows through the outlet channel 4 as a plasma and exits as a plasma jet AP through the outflow opening 9 into the surrounding atmosphere. The atmospheric area adjoining the outflow opening 9 is subsequently referred to as the outflow area 14 and is indicated in FIG. 1 with dotted lines. The outflow of the plasma jet AP in the surrounding atmosphere depends in particular on the operating pressure of the working gas source 8 and the current applied to the cathode 2 and anode 5.

A holder 12 is also arranged on the plasma generator 1 at its outflow end, via which a feed device of a corresponding precursor material PP for a first type of particles P to be introduced and the precursor PB for a second type serving as coating material B. particle P to be introduced is attached. The

In the exemplary embodiment shown, the feed device comprises two feed tubes 13, each of which is connected on the inlet side to an evaporator 15 for the precursor material PP for a first type of particle P to be introduced and for the precursor PB for a second type of particle P to be used as coating material B, and one on the outlet side Have outlet opening 16 which are directed into the outflow region 14. The evaporator 15 is connected to at least one storage container 17 for the precursor PB or for the precursor material PP.

FIG. 2a shows a schematic representation of a possible embodiment of the method according to the invention as a continuous method, in which the substrate 18 is moved from a place where a sol-gel layer matrix SM is applied to the plasma generator 1. If a multilayer structure is desired, alternating positioning between the location of the application of the sol-gel layer matrix SM and the plasma generator 1 can also be assumed (dashed arrow in FIG. 2a). 2b shows a schematic representation of a further possible embodiment of the method according to the invention, in which a simultaneous surface treatment of the substrate 18 is carried out by applying a sol-gel layer matrix SM and plasma treatment.

First, a sol-gel layer matrix SM is applied to the substrate 18, in the exemplary embodiment shown in FIG. 2, for example using a spraying method. Methods for applying a sol-gel layer matrix SM to a substrate 18 are well known. In this case, sol or gel synthesis can be used to produce inorganic or organically inorganic (hybrid polymer) coatings from colloidal dispersions, chemical process engineering first requiring a hydrolysis reaction of the alcoholate precursor (Formation of “sol particles”). These are condensed catalytically into chains by adding acid or base. Precursor molecules are often based on silicon (TEOS, TMOS), titanium or zirconium compounds, with the incorporation of appropriate organo-functional silicon compounds in the inorganic network in the condensation, the properties of the resulting sol-gel layers S can be set in a targeted manner.Possibilities include making the network more flexible, setting the curing conditions, forming an additional organic network (in addition to the inorganic), varying the surface energy, or increasing the Scratch resistance through co-condensation with metal alkoxides such as aluminum alkoxide All essential basic reactions, ie hydrolysis and the subsequent condensation reaction between the resulting reactive species to form the 3D network, are dynamic processes of many interlocking equilibrium reactions and can be controlled via pH, temperature or precursor molecule concentrations. As an alternative to the spraying process, sol-gel layers S can also be applied to 3D surfaces by immersion processes or spin coating.

The sol-gel layer application can be carried out by means of a sol-gel layer matrix SM which already contains biocidal substances, for example quaternary ammonium salts with a biocidal effect, in particular Q-POSS. Provision can also be made for the sol-gel layer to be applied by means of a sol-gel layer matrix SM which contains cerium in order to increase the corrosion resistance of the hardened sol-gel layer S.

Metallic materials, but also plastics, in particular thermoplastics, can be used as substrate 18, since due to the indirectly transmitted arc in the subsequent plasma treatment, both electrically conductive and non-conductive substrates such as glass-like materials, composite materials (CFRP / GFRP) or plastics can be coated.

In the exemplary embodiment shown in FIG. 2a, the substrate 18 is exposed to the plasma jet AP of a plasma generator 1 after the sol-gel layer S has been applied, in order to introduce particles P of a first type, for example biocidal particles, into the sol-gel layer S. If the sol-gel layer S already contains biocidal substances, this step can also be omitted. The particles P are added in the form of a corresponding precursor material PP to the evaporator 15 and subsequently to the plasma jet AP by means of a carrier gas and applied in the form of the particles P to the substrate 18, where they are embedded in the sol-gel layer S. In the context of the present invention, biocidal particles P which contain copper, zinc or tungsten and / or their oxides or titanium dioxide are preferably proposed. 2b shows a schematic representation of a further possible embodiment of the method according to the invention, in which a simultaneous surface treatment of the substrate 18 is carried out by applying a sol-gel layer S and introducing the particles P through the atmospheric plasma AP.

After the application of the sol-gel layer S, the sol-gel layer S is cured according to the invention by irradiation with an atmospheric plasma jet AP directed onto the sol-gel layer S. Particles P of a second type serving as coating material B can be admixed with the atmospheric plasma jet AP causing the hardening of the sol-gel layer S. This coating material B can in turn be applied with the same plasma generator 1, the plasma jet AP merely having a suitable precursor PB for the desired coating is fed. It is preferably a polymerizable precursor PB. These precursors PB, preferably HMDSO or TEOS, can be added to the plasma jet AP in the highly ionized discharge zone or only in the zone of quasi-neutral plasma without interaction of electrons and ions. The use of an atmospheric plasma jet AP according to the invention thus enables not only curing and surface modification due to the intense (UV) radiation, but also the production of polymer and oxide-ceramic thin layers, the decisive advantage being achieved in the use of 3D objects due to the significantly larger working distance.

The hardening of the sol-gel layer by means of atmospheric plasma jet AP can be carried out more quickly than with conventional thermal treatment, so that higher layer thicknesses can be achieved, and in particular a multilayer structure of the applied layer is economically possible by using several sol-gel layers S each Curing by the atmospheric plasma AP can be applied successively to the substrate 18, as will be explained with reference to FIG. 3.

3a shows a schematic illustration of a coating produced by the method according to the invention, comprising a sol-gel layer S and a layer of a coating material B, and FIG. 3b shows a schematic illustration of a multilayer structure comprising two sol- Gel layers S and two layers of a coating material B. Biocidal particles P are embedded in the sol-gel layer S, for example in the form of biocidal metal (oxide) particles. In addition, the sol-gel layer S can contain biocidal quaternary ammonium salts in order to further increase the biocidal effectiveness of the coating. It can also be provided that the sol-gel layer S contains cerium-based corrosion inhibitors to increase the corrosion resistance of the hardened sol-gel layer S. Furthermore, the coating according to FIGS. 3a and 3b comprises a layer of a coating material B which, in the exemplary embodiment shown, is formed from a polymerized precursor PB which can be polymerized by means of an atmospheric plasma jet AP. The precursor PB polymerizable by means of an atmospheric plasma jet AP is, for example, HMDSO or TEOS. This layer can be referred to as a permeation barrier layer since it represents a spatial delimitation of the biocidal reservoir given by the particles P of the sol-gel layer S.

The multilayer structure shown in FIG. 3 enables high layer thicknesses to be achieved which maintain the functionality of the biocidal coating over a long period of time. The subject invention thus enables a process for producing durable, hard, corrosion, abrasion and wear resistant coatings with a biocidal effect, which is also economically applicable.

Claims

Claims: 1. A method for coating a substrate (18), which comprises applying a sol-gel layer (S) to the substrate (18) and curing the sol-gel layer (S) applied to the substrate (18), characterized in that the sol-gel layer (S) with particles (P) with a before, during or after the application of the sol-gel layer (S) directed onto the substrate (18) and the particles (P)  containing atmospheric plasma jet (AP), and after the application of the sol-gel layer (S), the hardening of the sol-gel layer (S) by irradiation with a directed at the sol-gel layer (S),  atmospheric plasma jet (AP) takes place. 2. The method according to claim 1, characterized in that the particles (P) are biocidal particles (P). 3. The method according to claim 2, characterized in that the biocidal particles (P) contain copper, zinc or tungsten and / or their oxides, metal salts, or titanium dioxide. 4. The method according to claim 1, characterized in that the particles (P) are nanoparticles, microparticles or fibers which have the electrical conductivity, thermal conductivity, piezoelectric properties, magnetic properties, optical reflection / transmission / emission Change properties, optoelectric properties, biological-functional properties or decorative color properties of the sol-gel layer (S). 5. The method according to any one of claims 1 to 4, characterized characterized in that the sol-gel layer is applied by means of a sol-gel layer matrix (SM) which contains biocidal quaternary ammonium salts. 6. The method according to any one of claims 1 to 5, characterized in that the particles (P) are added to the atmospheric plasma jet (AP) causing the hardening of the sol-gel layer as coating material (B). 7. The method according to claim 6, characterized in that the coating material (B) is a  polymerized and by means of an atmospheric  Plasma jet (AP) polymerizable precursor (PB) is. 8. The method according to claim 6, characterized in that the coating material (B) is metallic or ceramic particles (P). 9. The method according to any one of claims 1 to 8, characterized  characterized in that a multilayer build-up takes place with the aid of a sequence of sol-gel layer applications and irradiation with the atmospheric plasma jet (AP). 10. Substrate with a according to the method according to one of the  Claims 1 to 9 applied coating. 11. Coating of a substrate with a biocidal effect according to a manufacturing method according to one of claims 1 to 9, characterized in that it contains a hardened sol-gel layer (S) containing copper, zinc, tungsten and / or their oxides, metal salts, or titanium dioxide comprises, as well as a layer which is formed from a polymerized precursor (PB) which can be polymerized by means of an atmospheric plasma jet (AP). 12. Coating according to claim 11, characterized in that it is by means of an atmospheric Plasma jet (AP) polymerizable precursor (PB) is HMDSO or TEOS. 13. Coating a substrate with a biocidal effect according to a production method according to one of claims 1 to 9, characterized in that it contains a hardened sol-gel layer (S) containing copper, zinc, tungsten and / or their oxides, metal salts, or titanium dioxide includes, as well as a layer made of metallic or ceramic  Particles (P) is formed.