EP1366331B2 - Method for producing a coating on a quasi-continuously fed material strip - Google Patents

Abstract

The invention relates to a method for producing a coating for quasi-continuously fed material strips, displaced in the direction of transport, in particular band-shaped, flexible material strips. According to said method, a coating agent is applied to at least one side of the material strip and is at least partially dried and/or cross-linked by means of electromagnetic radiation, the latter having a fundamental active component in the near-infrared wavelength range.

Description

The invention relates to a method for producing a coating by means of electromagnetic radiation on a moving in the conveying direction quasi-endlessly funded, in particular band-shaped, flexible material band.

Coatings of surfaces not only play a role in the aesthetic effect, but also serve, for example, to protect a certain object against external influences, such as e.g. against light radiation, water, heat and mechanical effects to make them more resistant. In addition, the coating can impart physical properties which the body to be coated as such does not possess, e.g. electrical conductivity or magnetizability.

Of particular importance in this regard is the coating of quasi-endless conveyed flexible material belts, such as e.g. of metal strips, plastic films, composite material systems and laminates, which are conveyed by rollers or stacks, for example.

Quasi-endless coated metal sheets, especially steel and aluminum sheets, are being processed in huge quantities in the automotive industry and also for the production of household appliances (the so-called white goods) and also for the manufacture of aircraft and watercraft and of cladding for the construction industry. The steel sheets are primarily bare, galvanized or nickel-plated (steel) sheets with thicknesses in the range of a few tenths of a millimeter and over one millimeter. Such sheets are wound on rolls, so-called. "Coils" before they are continuously fed to a specific forming or stamping process. As a pretreatment for a subsequent coating or plastic coating, the sheets already receive a corrosion protection coating and / or a primer or a primer coat on the "coil".

The coating of these metal strips is done for reasons of rationalization before the process step of bending, stamping, etc., in which the sheet ultimately in the desired shape is brought. In such a system, at least one coating agent is usually rolled on a first station of this system or applied to the metal strip by another technique. Such coating compositions are usually applied in the liquid state, but sometimes also as a powder coating.

Since the coating material must be completely dried or crosslinked before the subsequent process steps, the metal strip is subsequently fed to a furnace, which often operates on the principle of circulating air drying. In this furnace, the coating agent is heated together with the entire metal sheet of the metal strip, so that the coating agent dries and / or crosslinked. Due to the strong heating of the metal strip cooling of the metal strip is necessary following the drying process. Since the metal strip is subjected to bending, embossing and welding processes frequently after the coating process, the quality of the dried or crosslinked coating composition is particularly stringent. So this may not peel off when bending or embossing. Furthermore, the coated metal strip must remain weldable.

In another conventional drying method, the heat energy necessary for drying or crosslinking the coating agent becomes inductive, i. transmitted by electromagnetic coupling on the metal strip. The metal strip heated in this way releases the heat energy to the coating agent by heat conduction, as a result of which it is dried or crosslinked.

In the above-described conventional methods, the entire metal strip must be heated from the ambient temperature outside the plant at least to the temperature required for drying or crosslinking of the coating composition. With an inductive heat transfer system, with thin metal strip thicknesses and / or large coating thicknesses (i.e., depending on their specific heat capacity), it is necessary to heat the metal strip even above the temperature required for drying or crosslinking. That is, for a coating agent requiring a temperature of 180 ° C for cross-linking, the metal tape must be inductively heated to about 250 ° C to produce a sufficient temperature gradient between metal tape and coating agent such that the coating agent will be in an acceptable time can be dried or crosslinked.

The thermal energy required in the above-described methods for drying or crosslinking the coating agent is considerable since the entire metal strip must be heated. Its heating is in some cases even disadvantageous because it can change certain physical properties of the metal set in previous steps by means of carefully matched thermal processing methods. Incidentally, the energy lost due to the unnecessary heating of the metal strip adds up to economically significant amounts in view of the very large tonnages of coated metal strip dried in this way.

In addition, systems for coating material belts moving rapidly in the direction of conveyance are associated with high investment costs, which, for economic reasons, make it necessary to run the systems at the highest possible conveying speed and under the highest utilization.

In a "coil coating plant", the metal strip unwinding from a roll is guided through the individual stations of this plant, for example at a conveying speed of 120 m / min. Due to such high conveying speeds and the resulting shorter interaction time during drying or cooling of the metal strip, the individual stations, i. the drying oven and the cooling station, considerable length expansions, which can be up to 100 m.

It can be seen that the size of such a plant, due to its space requirements and increased maintenance costs, causes considerable costs. In addition, the long drying time when passing through the metal strip, before it can be fed to a forming process, increases the manufacturing cost of the metal strip to a corresponding extent. All in all, the mentioned disadvantages lead to a still relatively high price of sheet metal treated with the so-called "coil coating", which is becoming increasingly disadvantageous in view of the increasing cost pressure on the suppliers of the automobile and consumer goods industry.

Even thin-film structures on large-area, thin quasi-endless conveyed material bands or carriers are becoming increasingly important in various fields of technology. Known and economically most significant examples of these are thin-film transistor structures, as used in particular in liquid crystal display devices, and other thin-film systems for display units, such as plasma displays. Other technically and economically important thin-film structures are the separator structures of electrochemical elements, in particular primary or secondary elements based on lithium (lithium batteries and lithium-ion batteries, etc.) and highly differentiated membrane systems for the separation of substances and energy, for example in fuel cells.

In order to produce such thin film systems, it is customary to convert a thin coating applied to a thin support in an initial state into a functional layer and to firmly bond it to the support. It is important here to have a process with a high level of productivity, ie very high reliability and to the exclusion of damage to the carrier or the coating material. H. a high surface throughput per unit time to realize.

There are various manufacturing processes known for the various thin-film systems, which have achieved great technical importance today, which only partially meet these requirements.

The preamble of claims 1 and 14 is known from DE 4435077 A1 derived.

It is an object of the present invention to provide an improved, highly universal method and apparatus which is easily adaptable to various concrete layer structures and to a device for producing a coating on a material belt moving rapidly in the conveying direction, with which material and particularly quickly and with low energy consumption a coated quasi-endless conveyor belt can be produced. This object is achieved according to the invention by a method for producing a coating according to the Features in the characterizing part of claim 1 and by a device according to the features in the characterizing part of claim 14. Advantageous embodiments of the invention are the subject of the dependent claims.

• eine Zuführungs- und Vorschubeinrichtung für das Materialband,
• eine Zuführungs- und Schichterzeugungseinrichtung zur, insbesondere kontinuierlichen Zuführung und Aufbringung des Beschichtungsmittels auf dem Materialband,
• eine Strahlungsquelle zur Erzeugung von elektromagnetischer Strahlung mit hoher Leistungsdichte und im Bereich des nahen Infrarot, die als Laserdiode ausgebildet ist,

dadurch gekennzeichnet dass die Leistungsdichte der elektromagnetischen Strahlung oberhalb von 100 kW/m², bevorzugt oberhalb von 200 kW/m² und besonders bevorzugt oberhalb von 500 kW/m², insbesondere oberhalb von 750 kW/m² liegt.Thus, the present invention relates to a method for producing a coating of quasi-endless conveyed and in the conveying direction moving flexible Materialbändem in which a coating agent is applied to at least one side of the material strip and at least partially dried and / or crosslinked by electromagnetic radiation, wherein the electromagnetic radiation has a substantial active component in the wavelength range of the near infrared, and the radiation is generated by at least one emitter, which is designed as a laser diode, characterized in that the power density of the electromagnetic radiation above 100 kW / m ² , preferably above 200 kW / m ² and more preferably above 500 kW / m ² , in particular above 750 kW / m ² . Furthermore, the invention relates to an apparatus for carrying out the method according to one of claims 1 to 13, in particular with the steps of applying a coating agent and the drying or crosslinking of the coating agent to a coating, which are carried out respectively on the continuous material band, which comprises:

• a feeding and feeding device for the material strip,
• a feeding and layer-producing device for, in particular continuous feeding and application of the coating agent on the material strip,
• a radiation source for generating electromagnetic radiation with high power density and in the range of the near infrared, which is designed as a laser diode,

characterized in that the power density of the electromagnetic radiation above 100 kW / m ² , preferably above 200 kW / m ² and more preferably above 500 kW / m ² , in particular above 750 kW / m ² .

In particular, the present invention relates to a method for producing a coating or a thin layer structure from a band-shaped, flexible, in particular quasi-endless, carrier having at least one functional coating bonded to the carrier, which has a thickness which is in particular of the order of thickness of the carrier comprising the steps of forming a starting layer structure by coating a coating agent on the carrier and irradiating the carrier provided with the coating agent with electromagnetic radiation having a near-infrared active power to form the functional coating of the Coating agent while being combined with the support, including drying and / or thermal crosslinking. An important application of the proposed method is in particular the drying and / or crosslinking of a corrosion inhibitor or primer or a primer for a subsequent coating, especially on the surface of a bare, galvanized or nickel-plated steel sheet, especially for the automotive or household appliance production (coil coating).

Another important application is the

Coating agent (in the initial state) to a powder or liquid paint layer, which is dried or crosslinked to an intermediate or final coating.

The inventive method is characterized by potentially high productivity, simplicity and reliability with substantial exclusion of damage to the coating (s) and / or the carrier.

With the method according to the invention it is possible, the coating on a strip of material with particularly short irradiation times, preferably in less than 30s, preferably less than 10s, more preferably less than 5s, especially 2s and therefore, compared with a conventional coating or coil -Coating process, especially fast to produce. Due to the short treatment or irradiation time, the material band is thermally stressed little. This makes it possible to use thermally sensitive materials, e.g. Coating thermoplastics with coating materials that require temperatures higher than the damage temperature of the material strip for cross-linking. Thus, it becomes particularly possible with the method according to the invention to coat material strips whose coating was previously impossible or only with great technical difficulties because of their thermal sensitivity.

Also, changes in the material structure and / or changes in material properties can be avoided by applying the method according to the invention, which was often not possible in conventional methods, or only with considerable extension of the time required to carry out the method. This applies in particular to materials which, for example, deform with high heat input, such as e.g. Plastics. Furthermore, strips of material may be coated whose microscopic structure changes with high heat input (which may reduce their mechanical strength properties or cause microstructural changes in the material), e.g. Aluminum or alloys, or strips of material whose materials segregate, e.g. Composites.

In addition, the short irradiation times mean that in many cases a higher quality of the coating can be achieved. Also, the energy and cost required to produce a coating can be significantly reduced.

In order to achieve the most efficient transmission of radiant energy to the coating agent, the intensity maximum or the spectral composition of the electromagnetic radiation is adapted to the absorption and transmission properties of the coating composition and optionally the material band according to a preferred embodiment. Preferably, the wavelength of the maximum intensity and / or the spectral composition of the electromagnetic radiation is selected so that the coating agent absorbs the radiation energy substantially uniformly over its layer thickness, whereby an unacceptable thermal stress on the carrier as well as individual areas of the coating is avoided. It can thereby be achieved that the coating agent is uniformly and at least partially heated and / or crosslinked directly by the radiation within the shortest possible time.

Preferably, the spectral composition of the electromagnetic radiation is adjusted by at least one filter.

On the other hand, the intensity maximum of the electromagnetic radiation can preferably be adjusted so that relatively little radiation is absorbed in the band of material in order to avoid useless heating thereof. In addition, due to the very short irradiation times, an energy transfer by heat conduction, which takes place slowly in comparison to energy transfer by radiation, can be greatly reduced to the material band in contact with the coating agent.

Thus, in the case of the method according to the invention, in certain cases, depending on the thickness or the specific heat capacity of the material strip or coating agent, a clear temperature gradient in the material band and thus an energy separation between the material strip and the coating composition to be dried or crosslinked are achieved. A significantly higher efficiency compared to conventional methods can be achieved, and the amount of energy required to carry out the method according to the invention can be compared with the conventional methods, depending on the material properties, e.g. the specific heat capacity, the thickness of the material strip or the coating agent are significantly reduced, since comparatively little heat energy is transferred to the material band. This effect is particularly important for materials with a particularly high heat capacity such as sheet steel, because these materials absorb a large amount of energy. For example, for sheet thicknesses greater than 0.5 mm in the process of the present invention, the heating of the sheet may be as high as 250 ° C, e.g. in a conventional inductive method, the case is reduced to 200 ° C. Accordingly, this means a reduction of the energy required for drying or crosslinking of the coating agent by one fifth. For thicker materials, larger temperature differences, i. Energy savings possible.

In addition to the cost of the coating process, the costs of the device or system required for this purpose are significantly reduced, since due to the significantly shorter compared to conventional drying or curing times and the necessary for drying or curing distance at constant delivery speed is significantly reduced. In particular, infrastructure savings are particularly noticeable.

In many cases, reflections at the interface between the coating agent and the strip of material can bring about a renewed irradiation of the coating agent and thus the efficiency of the energy transfer to it can be increased. For this purpose, the surface of the material strip is preferably treated for the purpose of a specific adjustment of its reflectivity before the actual application of the coating agent. This is done for example by smoothing, polishing or roughening the surface.

According to a further preferred embodiment of the method according to the invention, the intensity maximum of the electromagnetic radiation is adapted to the absorption and / or transmission properties of the material strip such that the electromagnetic radiation at least partially penetrates the material band. This is particularly useful when applied on both sides of the material tape coating agent. In order to dry and / or crosslink the coating material applied on the other side of the material band, drying or crosslinking can be carried out in certain coating compositions / material band combinations in such a way that the electromagnetic radiation used for drying or crosslinking, in addition to the coating agent, which is applied to the radiation source facing the material band side, also penetrates the material band. In this case, preferably substantially no radiation energy is absorbed in the material band. The application of electromagnetic radiation takes place in this case only from one side of the material band. The coating agent applied to the material band on both sides is dried or crosslinked substantially simultaneously on both sides of the material band.

Accordingly, the method according to the invention can be carried out such that the coating material applied on both sides is dried or crosslinked substantially simultaneously with a radiation source which has only one side of the material band and which has at least one emitter.

It is also conceivable use of the method according to the invention in an application in which the coating agent is applied on one side, but on the side facing away from the radiation source. The electromagnetic radiation preferably penetrates the material band, substantially without being absorbed by it, and then drying or crosslinking the coating agent. By means of this arrangement, the radiation source can be protected from the volatile material and flammable components leaving it by the material band and / or one or more further processing steps can be carried out simultaneously with the irradiation process on the side of the material band on which the coating composition is applied the coating agent and / or the material band are performed without hindering the irradiation process.

According to the findings of the inventors, the drying or crosslinking processes of the coating agent are essentially thermally conditioned. That is, when drying a water or solvent coating agent, energy is transferred to the solvent with the electromagnetic radiation from the near infrared wavelength region to separate the solvent from the coating agent. For crosslinking, energy is transferred to the coating agent, which in the form of heat energy is used to effect the formation of polymer chains. For many coating agents, a certain temperature of the coating agent is required for this, so that the crosslinking process takes place.

In addition, photoreactions caused by the electromagnetic radiation from the near infrared wavelength range can lead to an additional acceleration of the crosslinking processes.

According to a further preferred embodiment, it is provided to dry or crosslink coating agents substantially completely by photoreactions, whereas thermal processes play only a minor or no role at all.

The drying or crosslinking of the coating agent can be either completely or only partially by the electromagnetic radiation whose essential active component is in the wavelength range of the near infrared. However, it is also possible to dry or crosslink the coating composition at several time intervals or staggered intervals. Also, the drying or crosslinking can be supported at the same time or offset in time with the above-mentioned irradiation by at least one additional radiation source, in particular with an active component in another wavelength range, and / or by at least one other energy or heat source. In order to achieve particularly short drying times or particularly short irradiation periods, electromagnetic radiation with a high power density is used. For the inventive method characteristic power densities are above 100 kW / m ² , preferably above 200 kW / m ² and more preferably above 500 kW / m ² . Such high power densities can be accomplished for example by the arrangement of a plurality of cooperating, in particular parallel to each other, over the entire width of the moving material band extending radiators with correspondingly assigned highly effective reflectors. A further adjustment of the power density can be achieved by focusing the electromagnetic radiation on the surface of the material band provided with the coating agent according to the present invention.

The adjustment of the power density can also be done via the operating voltage; Furthermore, filters can be used. In a further refined process control, a power control on the basis of feedback sensor signals (for example of temperature sensors) is provided.

According to the invention, irradiation is effected with electromagnetic radiation whose intensity maximum lies in the wavelength range from 0.8 μm to 2 μm. Such a wavelength range of the electromagnetic radiation has proved to be particularly effective for a highly effective polymer formation or polymer crosslinking of the coating compositions used for coating material strips.

When using wavelengths that take into account the specific absorption and / or transmission or reflection properties of the material strip and / or the coating agent, and / or when using the optimal power densities to be determined for the specific material band and / or coating agent, the invention enables a preferred embodiment preferably the above short irradiation periods. Depending on the coating agent used, pre-treatment of the material band is often provided before application. In particular, a heating of the material strip is necessary. Steel sheet must in this case usually be heated to temperatures of 900 ° C to 1100 ° C to achieve a structural change, which is usually carried out under an inert atmosphere or hydrogen atmosphere. Traditionally, methods using convection or induction heating have been used. The methods using convection heating take a long time to heat the steel strip to the high temperature. In induction heating, the efficiency and the homogeneous heating is problematic.

According to a preferred embodiment of the method according to the invention This preheating is also effected by means of electromagnetic radiation, the essential active component is in the wavelength range of the near infrared. This makes it possible to heat the steel strip much faster than conventional methods based on slow heat conduction.

The electromagnetic radiation used for this purpose preferably also has its essential active component in the wavelength range from 0.8 μm to 2.0 μm. Preferably, the wavelength is adapted so that a large part of the electromagnetic radiation is absorbed by the material band.

Due to the preferably very high conveying speed of the material strip, a corresponding quality assurance and process reliability of the process control is necessary. For this purpose, according to the present invention, at least one measurable process parameter is used, which allows a conclusion about the state and the quality of the coating via a corresponding automated process control. In particular, the temperature on the surface of the material strip is suitable for this purpose, which can be changed on the one hand via a corresponding change in the electrical power and thus the radiation power of the emitter and on the other hand via a variation of the distance between the emitters and the surface of the material strip. An apparatus for realizing an optionally automatic adjustment of irradiation parameters comprises at least one sensor for detecting the relevant physical quantities, ie in particular one or more photoelectric sensors for detecting the brightness, the reflectivity or the refractive index or other optical parameters, the information about the drying or crosslinking state of the coating agent, or a non-contact, in particular pyrometric temperature sensor.

To set the individual irradiation parameters, the sensor or the sensors are connected via an evaluation circuit to a control input or control inputs of a radiation control device. Depending on the detected measured values or a result of the evaluation of these measured values, the irradiation parameters to be set in the further course of the process, in particular the power density and optionally the spectral composition of the radiation, can be optimized. By providing a closed control loop, an automatically controlled real-time operational management can also be realized.

In special applications in which volatile constituents of the coating composition are separated from it by the interaction with the electromagnetic radiation, cooling and / or removal of these volatile constituents is also effected by a gas stream, in particular air flow, guided along the latter, preferably transversely to the conveying direction. meaningful.

This gas stream sweeping over the material strip preferably impinges on the particles of the separated moist component to be transported off at a certain predetermined speed and tears it with it, the gas stream preferably impinging on the material to be dried in a knife-like manner. In particular, a dry, cold gas is supplied with a high pulse. By a the surface of the applied coating agent and / or the back surface of the carrier sweeping gas stream on the one hand, a homogenization of the temperature distribution and optionally lowering the surface temperature and on the other hand, the rapid removal of volatile constituents of the coating agent can be achieved. As a result, the reliability and efficiency of the method can be further increased. The gas stream (air stream) is preferably dry and cold and is supplied at high pressure or momentum. Further details in this regard are in the DE-A 198 07 643 the applicant discloses.

Preferably, the endlessly conveyed material strip is a metal strip, in particular a steel strip. However, the endlessly conveyed material strip can also be metal foils or fine metal mesh, especially of aluminum or copper or their alloys or of an aluminum or copper-containing alloy, plastic foils, especially polyethylene (PE), polypropylene ( PP) or PVC films to glass layers or plates to composite material systems, such as Wood veneers to form laminates, e.g. Capacitors or displays, or to act thermoplastics or thermosets. Further preferred fields of application are films for packaging, e.g. Blister foils or adhesive films. In preferred layer constructions, both the coating agent and the material band or carrier have an average thickness in the range between 5 μm and 500 μm, in particular between 20 μm and 200 μm.

In a further preferred embodiment, the coating agent and the solid thin layer formed therefrom have a thickness in the range between 1 μm and 100 μm, in particular between 2 μm and 20 μm.

The application of the coating composition to the material to be coated strip of material is carried out depending on the nature, in particular the surface and / or the material composition of the material strip. Preferably, the coating agent is applied as a fluid or paströses system, which can be accomplished with known per se application method, in particular by rolling, brushing, spraying, pouring, spin-coating, trickling, inflation or doctoring. The coating composition is applied in accordance with a further preferred embodiment in the form of a powder, in particular by utilizing electrostatic forces, in particular puffed or inflated. In addition, it can also be sputtered onto the material tape. Depending on the surface condition of the material strip may u.U. a pretreatment, in particular by roughening, etching or by applying a primer be appropriate. This pretreatment is used i.a. the improvement of the adhesion between the coating agent and the material strip moving in the conveying direction.

Particularly suitable coating agents are: paints, in particular powder coatings, one-component or two-component wet paints, both water-based and on the basis of organic solvents, coatings for corrosion protection, coatings for pretreatment and for the functionalization of metal surfaces, conductive pastes and photoresist.

The paints are substances that are at least partially dryable with radiation and / or crosslinkable. Varnishing agents are typically systems containing at least one additive, preferably an additive and a binder, as discussed in detail below. Irradiation curing often occurs in many coating agents by polymerization of the binder contained in the paint.

An example of this is the optically initiated via photoinitiators polymerization of low-viscosity coating compositions with binders of reactive monomers, oligomers and prepolymers, such as free-radical or cationic polymerization or crosslinking of linear polymers with reactive side chains.

For the process according to the invention, wet paints or powder coatings can be used. As wet paints are u.a. Water-based paints and solvent-based coatings. Wet paints can be one-component paints, e.g. UV paints, and two-component paints, which can be used on water-based or even on the basis of organic solvents. In multilayer structures, combinations of these are also conceivable. Furthermore, weldable coating systems are also of interest for the coil coating processes mentioned above.

Depending on the solvent content, solvent-based paints are subdivided into conventional, solvent-based paints, low-solvent and solvent-free paints. The solids content of solvent-poor paints is greater than 70% by mass; At a solids content of less than 70% by mass, this is referred to as solvent-based paints. For solids-rich coatings such as spray paints, the term high solids is used.

Low-solvent and solvent-free coatings are subdivided into one- and two-component systems according to the type of curing reaction. In the case of one-component coatings, the polymerization and thus the crosslinking commence after the addition of initiators and accelerators or through the action of UV or electron beams. As one-component paints, for example, vinyl chloride polymers or copolymers and unsaturated polyester resins, such as low molecular weight hydroxyl-carrying acrylate, alkyd and polyester resins are used. Two-component coatings cure by an addition reaction in which unlike the one-component paints no polluting cleavage products are released. The binders are usually epoxy resins in combination with curing agents or polyisocyanates in combination with hydroxyl-bearing resins.

Powder coatings are thermoplastic or thermosetting plastics which are applied in powder form to substrates. In this case, various application methods such as electrostatic powder spraying, electrostatic vortex sintering, bulk sintering, vortex sintering, Rotationstsintem or Zentrifugalgießen be used. Powder coatings used are, for example, epoxy resin powders, saturated polyester resin powders, polyacrylate powders, polyethylene powders, polyvinyl chloride powders, polyamide powders, cellulose acetobutyrate powders, chlorinated polyethers, ethylene-vinyl acetate copolymer powders or polymethacrylic acid methyl ester powders.

UV lacquers require a so-called UV initiator, which is an expensive component of the lacquer, but is necessary for crosslinking. With the aid of the method according to the invention, the use of the UV initiators can be dispensed with in many cases, yet such UV lacquers can be dried by means of the method according to the invention.

Today, in paints, since they often use polyester resin as a binder, large amounts of solvent are used. However, the development is to the effect that attempts are increasingly being made, for various reasons such as for environmental protection and to avoid odor nuisance, to use lacquers with resins which require relatively little solvent, such as, for example, acrylate resins. The low-solvent coating systems (high-solids and water-dilutable systems) will therefore be increasingly used in the future. By using the method according to the invention, the disadvantageous longer drying time of these systems can be avoided.

As binders which can be crosslinked by radiation-induced processes, all customary radiation-curable binders or mixtures thereof which are known to the person skilled in the art can be used in the process according to the invention. They are either binders crosslinkable by free-radical polymerization or crosslinkable by cationic polymerization. In the former, by the action of electromagnetic radiation on the binder radicals, which then trigger the crosslinking reaction. In the cationic curing systems, the irradiation of initiators forms Lewis acids, which then trigger the crosslinking reaction.

According to their field of use, other coating compositions contain corresponding additives such as polymers, in particular crosslinkers, catalysts for crosslinking, initiators, especially pigments, dyes, fillers, reinforcing fillers, rheology aids, wetting and dispersing agents, adhesion promoters, additives for improving substrate wetting, additives for improving surface smoothness , Matting agents, flow control agents, film-forming adjuvants, driers, skin preventatives, light stabilizers, corrosion inhibitors, biocides, flameproofing agents, polymerization inhibitors, in particular photoinhibitors or plasticizers, as are customary and known, for example, in the coatings sector. The choice of additives depends on the desired property profile of the coating composition and its intended use.

The coating compositions may further contain ceramic colors such as titanium dioxide, carbon black or colored pigments such as lead chromate, red lead, zinc yellow, zinc green, cadmium red, cobalt blue, berlin blue, ultramarine, manganese violet, cadmium yellow, molybdate orange and red, chrome orange and red, iron oxide red, chrome dioxide green and strontium yellow.

Also organic colors, for example naturally occurring pigments such as sepia, indigo, chlorophyll, or in particular synthetic pigments such as azo pigments, indigoids, dioxazine, quinacridone, phthalocyanine, isoindolidone, perylene and perinone, metal complex and alkali metal Pigments can be components of the coating compositions.

Likewise, the coating compositions may contain luminescent pigments to produce a metallic effect. Usable are in particular metal platelets, preferably aluminum platelets, which give a special optical effect on their reflection behavior. Other metal platelets are, for example, those based on gold bronzes, copper-zinc alloys, nickel, stainless steel and mica.

The coating compositions may also contain luminescent pigments to produce metameric effects. Here, for example, pigments for the production of Pearlescent are used. Specifically, bismuth oxychloride, titanium dioxide mica and lead carbonate are mentioned.

As interference pigments for thermal protection, the coating agents may contain high reflectivity pigments for IR radiation, especially lead carbonate and titanium dioxide mica. Destructive interference leads to the extinction of significant radiation components, which provides thermal protection

The coating compositions may also contain pigments for corrosion protection in the context of the invention. Preferably, lead (II) orthoplumbate, chromate pigments, phosphate pigments, zinc dust or lead dust are used.

In addition, the coating compositions may contain magnetic pigments such as pure iron, iron oxide or chromium (IV) oxide.

The proposed method is particularly suitable for producing a functional coating for the production of thin-film transistor arrangements, in particular for liquid crystal display arrangements, separator membranes for electrochemical elements, in particular lithium-ion batteries, for the production of thin-film structures for plasma displays and for the production of membrane structures for fuel cells.

By applying the method according to the invention, it is thus possible to produce a coated substrate comprising a substrate and a dried and / or crosslinked coating agent applied on one or both sides. The substrate is in particular selected from a thermoplastic substrate, a metal foil or sheet, a plastic foil, a glass plate, a composite material system, such as e.g. a wood veneer, a laminate, e.g. Capacitors or displays. The coating composition is preferably under a paint, in particular powder paint, a one-component or two-component wet paint, both water-based and on the basis of organic solvents, a coating for corrosion protection, a coating for pretreatment and for the functionalization of metal surfaces, a conductive paste or a Photoresist selected.

A suitable arrangement for producing a thin layer structure of a band-shaped, flexible, in particular quasi-endless, carrier having at least one functional coating firmly bonded to the carrier, which has a particular thickness of the thickness of the carrier thickness, with the steps of formation a starting layer structure by applying a coating agent to the carrier and irradiating the carrier provided with the coating agent with electromagnetic radiation having an active portion in the near infrared range, to form the functional coating from the coating agent while being combined with the carrier under Including drying and / or thermal crosslinking, preferably comprises a supply and feed device for the carrier, which may in particular comprise a carrier supply roll and a roll feed device, a supply and Schichterzeugu ngseinrichtung for, in particular continuous, supply and application of the coating agent to the carrier and a downstream of the supply and layer generating means arranged and facing the carrier provided with the coating medium, radiation having an active component in the region of the near infrared-generating irradiation device.

Furthermore, a means for adjusting or a regulating device for regulating the radiation power, in particular adjusting means for precision adjustment of at least one radiation source of the irradiation device is provided in particular.

The inventive method is moreover preferably carried out with a device which comprises a substantially closed device, through which the material strip provided on one or both sides with a coating agent, in which at least one emitter is mounted and the inner walls with at least one electromagnetic Radiation reflecting device, such as a reflector are provided.

In principle, it is advisable in all cases to equip the system with reflectors for increasing the efficiency and for energy optimization, so that where emitters are used a closed radiation space is generated. In addition to counter reflectors, the provision of side reflectors and reflectors arranged transversely to the direction of conveyance is additionally useful.

According to a preferred embodiment, the side reflectors are deliverable, for example, by means of displacement devices and can be adapted to the width of the material band to be coated by forming the radiation space. As a result, the width of the radiation space can be adapted to the width of the material strip and the efficiency of the system can be optimized regardless of the width of the material strip. When processing a strip of material having a lower than the maximum width possible for the system, the emitter located outside of the delivered side reflectors are not used. Thus, an optimal and thus energy-saving drying or crosslinking of the coating agent can always be achieved. Such an adaptation of the energy sources used for drying or for crosslinking is not possible with conventional methods and represents a major problem.

For two-sided coating of material bands, it makes sense, depending on the nature of the coating composition or the material emitter modules only on one side of the material band or on both sides of the material band to order. If the electromagnetic radiation used for drying or crosslinking can be selected so that the radiation can be penetrated in addition to the coating agent and the material band, it makes sense to arrange emitter modules only on one side of the material band for investment reasons. In order to increase the effectiveness of the system, it is then appropriate to arrange one or more reflectors on the side opposite the at least one emitter in order to reflect the radiation passing through the material band and the layers of the applied coating agent back through the coating agent and the material band.

In radiopaque material tapes, as well as in cases where the crosslinking of the coating agent is essentially effected by photoreactions, bilateral emitter module arrangement is advantageous.

For drying and / or crosslinking of the coating composition, the device has at least one emitter laser diode.

Optionally, a plurality of emitters, preferably parallel to one another, can also be arranged as so-called emitter modules over the entire width of the material band moving rapidly in the conveying direction.

In a preferred embodiment, the emitters are arranged parallel to the conveying direction of the endlessly conveyed material strip. This has the significant advantage that the irradiance across the entire band of material both in the conveying direction as well as in the direction perpendicular thereto remains homogeneous, even if, for example, due to the aging process of the emitter, or changed by another effect, the radiation homogeneity along the longitudinal direction of the emitter , assuming that this change is the same for all emitters.

According to a further preferred embodiment, a specific line-shaped arrangement of the emitter is selected for irradiation of linear, for example, lattice-shaped endlessly conveyed material bands in the conveying direction, so that in each case arranged opposite to a parallel to the conveying direction material part of the lattice-like material strip arranged substantially parallel emitter or optionally a number of located in a row arranged emitters. Additionally, to increase efficiency, the radiation emitted by the emitters may be focused on the parts of material by appropriate reflective means. Furthermore, the arrangement of a reflector on the side opposite the material band relative to the emitters side to increase the efficiency of the system is desirable. To coating agent, which is applied to extending transversely to the conveying direction of material parts, also efficient to dry or crosslink, additionally oriented transversely to the conveying direction linear emitters are provided, which can be moved with the material parts with their conveying speed. Further details of this particular embodiment are contained in a patent application entitled "Method and Apparatus for Heating Continuously Supported Latticed Material or Similar Structures" by the Applicant DE 10062633 filed application.

According to another embodiment, the space in which volatile components of the coating agent, such as solvents escape during the drying process, is separated from the emitters by a quartz glass disk. According to a further preferred embodiment, in order to further increase the security between the material band and the emitter or emitters, two juxtaposed quartz glass panes are provided, between which additionally a cooling gas, e.g. Nitrogen gas flows.

In a preferred embodiment of this device, a gas flow generating device for generating and aligning the above-mentioned gas flow and / or a device for adjusting or regulating the power is additionally provided, the latter preferably comprising means for adjusting the distance between the radiation source and the layer structure.

Preferably, the gas flow generating device is designed so that a directed substantially parallel to the surface of the material strip, this is generated in the range of action of the irradiation device sweeping, especially dry and cold gas flow with high pulse.

A device for producing a quasi-endless coated, windable sheet, in particular of body panels for the automotive industry or of housing panels for household appliances, with the steps of applying a, in particular liquid, coating agent and the drying or crosslinking of the coating agent into a solid thin layer, each carried out on the fast-running sheet, ie An apparatus for carrying out the coil coating method has an irradiation device for generating electromagnetic radiation with high power density and in the range of the near infrared, which in particular has its substantial active component in the wavelength range between 0.8 μm and 1.5 μm.

Advantages and advantages of the invention with respect to the coil coating method will become apparent from the following description of a preferred embodiment of a coil coating apparatus with reference to the single figure. This shows in outline a coil coating device 1 for coating a quasi-endless steel sheet 3, which is wound on a coil 5, and for drying the coating. The coil 5 is rotated by an electric drive 7 in rotation, and thereby the sheet 3 is moved under a spray coater 9 and a NIR drying section 11 along.

Through the spray coater 9, an aqueous solution 13 'is applied to the sheet 3 as the starting material for a corrosion protection or primer layer 13. This is dried in an elongated irradiation zone A formed by the NIR drying section 11 with NIR radiation of high power density, in particular above 500 kW / m ² .

The NIR drying section 11 comprises a solid Al reflector 15 having a plurality of approximately W-shaped reflector sections 15a in cross-section, which is internally water-cooled and, for this purpose, connected via cooling water lines 17 to an external cooler (not shown). In the center of each reflector portion 15a sits an emitter 19th

The emitters 19 are energized by an irradiation control unit 21 and controlled to emit NIR radiation having an intensity maximum in the range between 0.8 μm and 1.5 μm.

The radiation control device assigned to the irradiation device is preferably suitable for setting the power density of the radiation on the surface of the coating agent to a value of more than 500 kW / m ² , in particular more than 750 kW / m ² , and / or for adjusting the temperature in the coating agent a value above 200 ° C, in particular to a value in the range between 200 and 250 ° C.

In the A1 reflector 15 is a pyrometer element 23 for detecting the

Surface temperature of the coating 13 in a T-detection zone B, which is connected to a signal input of the irradiation control unit 21. The irradiation is controlled so as to maintain a substantially constant temperature in the coating which is selected as a function of the physical and chemical properties of the precursor 13 'of the anticorrosive or primer layer 13, typically at about 200 ° C.

By suitable control of the drive 7, the passage speed of the steel sheet 13 is adjusted by the irradiation zone A such that a residence time of the aqueous solution 13 'in the irradiation zone A of a few seconds is obtained, which for complete evaporation of the solvent component and for thermal crosslinking of the layer 13th is sufficient.

The sheet is typically conveyed through the drying apparatus at a speed in the range between 50 and 200 m / min, in particular between 75 and 150 m / min. In order to achieve advantageously short irradiation times of less than 10 s, in particular less than 5 s, an irradiation device with a length of 2 to 5 meters and more than one megawatt, preferably 2 to 5 MW, is then to be used to record power consumption on the surface of the surface to be dried crosslinking coating a radiation power density of more than 500 kW / m ² , in particular more than 750 kW / m ² , produced.

These values are to be used for the primary drying or crosslinking of a layer applied as a liquid or in powder form, where in the coating in the drying or crosslinking step the temperature is at a value above 200 ° C., in particular in the range between 200 ° C. and 250 ° ° C is held.

In particular, for use with powder coatings, the method is preferably without an active gas stream supply for the removal of evaporating coating components from; For this purpose, essentially the convection over the heated coating is utilized. In the drying of liquid systems, however, it is quite possible to use a gas stream sweeping over the surface, in particular a stream of air produced by a suitable blower.

For quality control in carrying out the method, at least one process-relevant physical variable of the coating system, in particular its temperature and possibly also optical properties, is preferably measured and evaluated for process control.

Claims (18)

1. Method for producing a coating for quasi-continuously fed flexible material bands moved in the direction of transport, wherein a coating agent is applied to at least one side of the material band and is at least partially dried and/or cross-linked by means of electromagnetic radiation, the electromagnetic radiation having a fundamental active component in the near-infrared wavelength range, and the radiation is generated by at least one emitter being configured as a laser diode,
   characterized in that
   the power density of the electromagnetic radiation is above 100 kW/m², preferably above 200 kW/m² and even more preferably above 500 kW/m², particularly above 750 kW/m².
2. Method according to claim 1, wherein the intensity maximum of the electromagnetic radiation is adapted to the absorption and transmission properties of the coating agent so that the coating agent absorbs the radiant energy substantially uniformly across its layer thickness.
3. Method according to claim 1 or 2, wherein the intensity maximum of the electromagnetic radiation is adapted to the absorption and/or transmission properties of the material band such that the electromagnetic radiation at least partially penetrates the material band.
4. Method according to one of the preceding claims, wherein coating agent applied to both sides of the material band is dried and cross-linked, respectively, on both sides of the material band substantially at the same time.
5. Method according to claim 4, wherein the coating agent applied to both sides is dried and cross-linked, respectively, substantially at the same time by means of at least one radiation source disposed on only one side of the material band.
6. Method according to one of the preceding claims, wherein the drying and/or cross-linking of the coating agent is at least partially accomplished by a photoreaction.
7. Method according to one of the preceding claims, wherein the fundamental active component of the electromagnetic radiation is in the wavelength range of 0.8 µm to 2 µm.
8. Method according to one of the preceding claims, wherein the exposure using electromagnetic radiation lasts less than 30s, preferably less than 10s, particularly less than 5s and even more preferably less than 2s.
9. Method according to one of the preceding claims, wherein the surface of the material band is pretreated, preferably heated, prior to applying the coating agent.
10. Method according to one of the preceding claims, wherein volatile components separated from the coating agent are removed by means of a gas flow sweeping over the material band.
11. Method according to one of the preceding claims, wherein the material band is a metal band, particularly a bright, galvanized or nickel-plated sheet steel, particularly a body sheet-metal for the automobile industry or a casing sheet-metal for household appliances.
12. Method according to one of the preceding claims, wherein the coating agent is a lacquer, particularly a liquid coating or powder coating, a corrosion prevention coating, for the pretreatment and/or the functionalization of the surface of the material band, a conductivity paste or a photoresist.
13. Method according to one of claims 1 to 10 or 12, wherein a substrate selected among a thermoplastic substrate, a metal foil, a plastic foil, a glass plate, a material composite system or a laminate is used.
14. Apparatus for performing the method according to one of claims 1 to 13, particularly including the steps of applying a coating agent and drying and cross-linking, respectively, the coating agent to form a coating, each of which are carried out on the material band being passed through, the apparatus comprising:

    - a feeding and advancing means for the material band,

    - a supplying and layer producing means for, in particular continuously, supplying and applying the coating agent to the material band,

    - a radiation source for generating electromagnetic radiation with a high power density and in the near-infrared range, which is configured as a laser diode

    characterized in that
    the power density of the electromagnetic radiation is above 100 kW/m², preferably above 200 kW/m² and even more preferably above 500 kW/m², particularly above 750 kW/m².
15. Apparatus according to claim 14, wherein the layer producing means is substantially closed and in which the inner walls are provided with at least one device reflecting electromagnetic radiation.
16. Apparatus according to claim 15, further comprising side walls, which are substantially arrangeable at the fed material band and can be adapted to the width of the material band by forming the radiation area.
17. Apparatus according to one of claims 14 to 16, which has at least one emitter provided on each side of the material band.
18. Apparatus according to one of claims 14 to 17, wherein the emitter has a substantially elongated shape and is aligned along the material band feeding direction.