EP1366331A1

EP1366331A1 - Method for producing a coating on a quasi-continuously fed material strip

Info

Publication number: EP1366331A1
Application number: EP02702389A
Authority: EP
Inventors: Rainer Gaus; Kai K. O. BÄR; Rolf Wirth; Klaus Gabel
Original assignee: Adphos Advanced Photonics Technologies AG
Current assignee: Adphos Innovative Technologies GmbH
Priority date: 2001-03-01
Filing date: 2002-03-01
Publication date: 2003-12-03
Anticipated expiration: 2022-03-01
Also published as: EP1366331B2; ATE489594T1; EP1366331B1; DE10109847A1; WO2002070973A1; DE50214786D1

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

Method for producing a coating on a quasi-endlessly conveyed material belt

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

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

The coating of quasi-endlessly conveyed flexible material strips, e.g. of metal strips, plastic foils, composite material systems and laminates, which are conveyed for example by rolls or stacks.

Quasi-endless coated metal sheets, in particular steel and aluminum sheets, are used in huge quantities in the automotive industry and also for the manufacture of household appliances (the so-called white goods) and also for the manufacture of air and water vehicles and cladding for the building industry processed. The steel sheets are primarily bare, galvanized or nickel-plated (steel) sheets with thicknesses in the range between a few tenths of a millimeter and over a millimeter. Such sheets are Coils are wound up on rolls 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 have an anti-corrosion coating and / or a primer or a coating on the coil primer application.

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

Since the coating agent must be completely dried or crosslinked before the subsequent process steps, the metal strip is subsequently fed to an oven, which often works on the principle of forced air drying. In this furnace, the coating agent is heated together with the entire sheet of the metal strip, so that the coating agent dries and / or cross-links. Due to the strong heating of the metal strip, cooling of the metal strip is necessary after the drying process. Since the metal strip is often subjected to bending, embossing and welding processes after the coating process, particularly high demands are placed on the quality of the dried or crosslinked coating agent. So it must not flake off when bending or embossing. Furthermore, the coated metal strip must remain weldable.

In another conventional drying method, the thermal energy required for drying or crosslinking the coating agent is transferred inductively, ie by means of electromagnetic coupling, to the metal strip. That so heated metal strip releases the thermal energy to the coating agent by thermal conduction, as a result of which it is dried or crosslinked.

In the conventional methods described above, the entire metal strip must be heated from the ambient temperature outside the system to at least the temperature required for drying or crosslinking the coating agent. In a system working with inductive heat transfer, it is necessary with thin metal strip thicknesses and / or large coating agent thicknesses (i.e. depending on their specific heat capacity) to even heat the metal strip above the temperature required for drying or crosslinking. This means that in the case of a coating agent which requires a temperature of 180 ° C. for crosslinking, the metal strip must be heated inductively to approximately 250 ° C. in order to produce a sufficient temperature gradient between the metal strip and the coating agent, so that the coating agent is in one 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 has to be heated. In certain cases, its heating is even disadvantageous because it can change certain physical properties of the metal, which were set in previous steps by means of carefully coordinated thermal processing methods. 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 fast moving material belts 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 maximum load. In a "coil coating system", the metal strip unwinding from a roll is fed through the individual stations of this system, for example at a conveying speed of 120 m / min. Due to such high conveying speeds and the resulting lower interaction time when drying or cooling the metal strip the individual stations, ie the drying oven and the cooling station, have considerable lengths, which can be up to 100 m.

It is clear that the size of such a system causes considerable costs due to its space requirements and increased maintenance. In addition, the long drying time when passing through the metal strip before it can be fed to a forming process increases the manufacturing costs of the metal strip to a corresponding extent. Overall, the disadvantages mentioned lead to a relatively high price of sheet metal processed with the so-called "coil coating", which is becoming increasingly noticeable in the face of increasing cost pressure among suppliers to the automotive and consumer goods industries.

Thin-film structures on large, thin, quasi-endlessly conveyed material belts or carriers are also becoming increasingly important in various fields of technology. Known and economically most important examples of this are thin-film transistor structures, such as are used in particular in liquid crystal display arrangements, and other thin-film systems for display units, for example for 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.) as well as highly differentiated membrane systems for material separation and energy generation, for example in fuel cells. To produce such thin layer systems, a thin coating applied to a thin carrier in an initial state usually has to be converted into a functional layer and firmly connected to the carrier. The important thing here is to realize a process with a very high degree of reliability and excluding damage to the carrier or the coating material with a high productivity, ie a high area throughput per unit of time.

Various types of manufacturing processes are known for the various thin-film systems which have become of great technical importance today, and which only partially meet these requirements.

It is therefore an object of the present invention to provide an improved, highly universal method and a device for producing a coating on a material belt that moves quickly in the conveying direction, with which or with which particularly quickly and with little, and adaptable to different concrete layer structures Energy expenditure can produce a coated quasi-endless conveyed material band. This object is achieved according to the invention by a method for producing a coating according to the features of claim 1 and by a device according to the features of claim 16. Advantageous embodiments of the invention are the subject of the dependent claims.

The present invention thus relates to a method for producing a coating of quasi-endless, conveyed and conveyed material belts which are provided with a coating agent which is at least partially dried and / or crosslinked at least partially by means of electromagnetic radiation, the essential one Active component of the electromagnetic radiation is in the wavelength range of the near infrared. The present invention relates in particular to a method for producing a coating or a thin layer structure from a band-shaped, flexible, in particular quasi-endless, carrier with at least one functional coating connected to the carrier, which has a thickness that is in particular of the order of the thickness of the carrier has the steps of forming an output layer structure by surface-coating a coating agent on the carrier and irradiating the carrier provided with the coating agent with electromagnetic radiation, which has an active component in the near infrared range, to form the functional coating from the Coating agent with simultaneous connection to the carrier including drying and / or thermal crosslinking. An important application of the proposed method is in particular the drying and / or crosslinking of an anti-corrosion agent or a primer or a primer for subsequent painting, in particular on the surface of a bare, galvanized or nickel-plated steel sheet, in particular for automobile or household appliance production (coil coating).

In another important application, the coating agent (in the initial state) is a powder or liquid lacquer layer which is dried or crosslinked to give an intermediate or final lacquer.

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

With the method according to the invention, it is possible to coat on a material strip with particularly short irradiation times, preferably in less than 30s, preferably in less than 10s, more preferably less than 5 s, in particular 2s, and therefore compared to a conventional coating or Coil coating process, particularly quick to produce. Due to the short treatment or irradiation time, the material strip is subjected to little thermal stress. sprucht. This makes it possible to coat thermally sensitive materials such as thermoplastics with coating agents that require temperatures for crosslinking that are higher than the damage temperature of the material strip. Thus, the method according to the invention makes it possible, in particular, to coat strips of material whose coating was previously not possible due to their thermal sensitivity or only with great technical difficulties.

Changes in the material structure and / or changes in material properties can also be avoided by applying the method according to the invention, which was often not possible with conventional methods, or only if the time required to carry out the method was considerably extended. This applies in particular to materials that, for example, deform when subjected to strong heat, e.g. Plastics. Furthermore, strips of material can be coated, the microscopic structure of which changes when heat is applied (which can reduce their mechanical strength properties or structural changes in the material), e.g. Aluminum or alloys, or strips of material, the materials of which segregate, e.g. Composites.

Due to the short irradiation times, a higher quality of the coating can also be achieved in many cases. The energy and cost required to produce a coating can also be significantly reduced. In order to achieve the most efficient possible transmission of radiation energy to the coating agent, according to a preferred embodiment the intensity maximum or the spectral composition of the electromagnetic radiation is adapted to the absorption and transmission properties of the coating agent and, optionally, of the material strip. The wavelength of the maximum intensity and or the spectral composition of the electromagnetic radiation is preferably selected so that the coating The radiation energy is absorbed substantially uniformly over its layer thickness, an inadmissible thermal load on the carrier and also individual areas of the coating being avoided. It can thereby be achieved that the coating agent is at least partially heated and / or crosslinked directly and at least partially by the radiation within a very short time.

The spectral composition of the electromagnetic radiation is preferably set by at least one filter.

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

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

In addition to the costs of the coating process, the costs of the device or system required for this are also significantly reduced, since the drying and crosslinking times, which are considerably shorter compared to conventional processes, also significantly reduce the distance required for drying or crosslinking while the conveying speed remains the same is. Infrastructure savings are particularly noticeable.

In many cases, reflections at the interface between the coating agent and the material strip can cause the coating agent to be re-irradiated, thus increasing the efficiency of the energy transfer to it. For this purpose, the surface of the material strip is preferably treated for the purpose of specifically adjusting its reflectivity before the coating agent is actually applied. 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 band in such a way that the electromagnetic radiation at least partially penetrates the material band. This is particularly useful when the coating agent is applied to both sides of the material strip. In order to also dry and / or crosslink the coating agent applied to the other side of the material strip, certain coating agent / material strip combinations can be used the drying or crosslinking is carried out in such a way that the electromagnetic radiation used for drying or crosslinking, in addition to the coating agent which is applied to the material strip side facing the radiation source, also penetrates the material strip. Essentially no radiation energy is preferably absorbed in the material band. In this case, electromagnetic radiation is only applied from one side of the material strip. The coating agent applied to the material strip on both sides is dried or crosslinked essentially simultaneously on both sides of the material strip.

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

It is also conceivable to use 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 strip, essentially without being absorbed by it, in order then to dry or crosslink the coating agent. With this arrangement, the radiation source can be protected from the volatile and highly flammable components emerging from the coating agent by the material strip and / or one or more further processing steps can be carried out simultaneously with the irradiation process on the side of the material strip to which the coating agent is applied the coating agent and / or the material strip can be carried out without impeding the irradiation process.

According to the inventors' knowledge, the drying or crosslinking processes of the coating agent are essentially thermal. This means that when drying a water or solvent Layering means the solvent with the electromagnetic radiation from the wavelength range of the near infrared energy is transferred to separate the solvent from the coating agent. For crosslinking, energy is transferred to the coating agent, which is used in the form of thermal energy to cause the formation of polymer chains. With many coating compositions, a certain temperature of the coating composition is required for the crosslinking process to take place.

In addition, photo reactions caused by the electromagnetic radiation from the near infrared wavelength range can lead to an additional acceleration of the cross-linking processes.

According to a further preferred embodiment, it is provided that coating agents are dried or crosslinked essentially completely by photoreactions, while thermal processes play only a minor role or not at all.

The coating agent can be dried or crosslinked either completely or only partially by means of the electromagnetic radiation, the essential active component of which lies in the wavelength range of the near infrared. However, it is also possible to dry or crosslink the coating agent in a plurality of time intervals which are separated or offset from one another. Drying or crosslinking can also be supported at the same time or at different times from the above-mentioned radiation by at least one additional radiation source, in particular with an active component in a different wavelength range, and / or by at least one other energy or heat source.

For drying and / or crosslinking the coating agent, the radiation field of the electromagnetic radiation in a proven and cost-effective manner according to the invention is preferred by at least one thermal one Radiant body or emitter generated, the radiator temperature is above 2900 K and preferably above 3200 K.

In order to achieve particularly short drying times or particularly short irradiation times, electromagnetic radiation with a high power density is preferably used. Typical power densities characteristic of the method according to the invention are in particular above 100 kW / m ² , preferably above 200 kW / m ² and particularly preferably above 500 kW / m ² . Such high power densities can be achieved, for example, by the arrangement of a plurality of interacting, in particular parallel, halogen lamps which extend over the entire width of the moving material strip and have correspondingly assigned highly effective reflectors. A further adjustment of the power density can be achieved in that, according to the present invention, the electromagnetic radiation is focused on the surface of the material strip provided with the coating agent.

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

It is preferably irradiated with an electromagnetic radiation, the intensity maximum of which lies in the wavelength range from 0.8 μm to 2 μm. Such a wavelength range of the electromagnetic radiation has proven to be particularly effective for a highly effective polymer formation or polymer crosslinking of the coating agents used for coating material strips.

When using wavelengths that match the specific absorption and / or transmission or reflection properties of the material band and / or the

Take coating agent into account, and / or when using the for the In a preferred embodiment, the invention preferably enables the above-mentioned short irradiation times for specific material strips and / or coating agents for optimal power densities to be determined. Depending on the coating agent used, pre-treatment of the material strip is often provided before application. In particular, heating of the material strip is necessary. Steel sheet usually has to 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. Conventionally, methods using convection or induction heating are used for this. The processes in which convection heating is used take a long time to heat the steel strip to the high temperature. Efficiency and homogeneous heating are problematic in induction heating.

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

The electromagnetic radiation used for this preferably has its essential active component likewise in the wavelength range from 0.8 μm to 2.0 μm. The wavelength is preferably adjusted 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 belt, appropriate quality assurance and process reliability of the process management is necessary. For this purpose, according to the present invention, at least one measurable process parameter is used, which allows a conclusion to be drawn about the condition and quality of the coating by means of a corresponding automated process control. The temperature is particularly suitable for this the surface of the material band, which can be changed on the one hand by a corresponding change in the electrical power and thus the radiation power of the emitter and on the other hand by varying the distance between the emitters and the surface of the material band. A device for realizing a possibly automatic setting of radiation parameters comprises at least one sensor for detecting the relevant physical quantities, in particular one or more photoelectric sensors for detecting the brightness, the reflectivity or the refractive index or other optical parameters which provide information about the Provide the drying or crosslinking state of the coating agent, or a contactless, in particular pyrometric temperature sensor.

To set the individual irradiation parameters, the sensor or the sensors is connected to a control input or control inputs of a radiation control device via an evaluation circuit. Depending on the recorded measured values or a result of the evaluation of these measured values, the radiation parameters to be set in the further course of the process, in particular the power density and possibly 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 implemented.

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 carried out by means of a gas flow, preferably at right angles to the conveying direction, along the latter, in particular air flow. meaningful.

This gas stream sweeping over the material strip preferably strikes the material to be removed at a certain predetermined speed

Particles of the separated wet component and entrains it, the Gas flow preferably impinges knife-like on the material to be dried. In particular, a dry, cold gas with high momentum is supplied. A gas flow sweeping over the surface of the applied coating agent and / or the rear surface of the carrier can, on the one hand, achieve a uniform distribution of the temperature and, if necessary, lower the surface temperature, and on the other hand can quickly remove volatile constituents of the coating agent. This further increases the reliability and efficiency of the method. The gas stream (air stream) is preferably dry and cold and is supplied at high pressure or pulse. Further details in this regard are disclosed in DE-A 198 07 643 by the applicant.

The endlessly conveyed material band is preferably a metal band, in particular a steel band. The endlessly conveyed material band can, however, also be metal foils or fine metal mesh, especially made of aluminum or copper or their alloys or made of an alloy containing aluminum or copper, plastic foils, especially polyethylene (PE), polypropylene ( PP) or PVC films, around glass layers or sheets, around material composite systems, such as Wood veneers to laminates such as Capacitors or displays, or thermoplastics or thermosets. Other preferred areas of application are films for packaging, such as Blister films or adhesive films. In preferred layer structures, both the coating agent and the material band or the 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 lμm and lOOμm, in particular between 2μm and 20μm.

The coating agent is applied to the material strip to be coated depending on the nature, in particular the surface and / or the material composition of the material band. The coating agent is preferably applied as a fluid or pasty system, which can be accomplished using known application methods, in particular by rolling on, spreading on, spraying on, pouring, spinning on, trickling on, inflating or knife coating. According to a further preferred embodiment, the coating composition is applied in the form of a powder, in particular using electrostatic forces, in particular sprinkled on or inflated. In addition, it can also be sputtered onto the material tape. Depending on the surface quality of the material strip, a pretreatment, in particular by roughening, etching or also by applying an adhesion promoter, may be appropriate. This pretreatment serves, inter alia, to improve the adhesion between the coating agent and the material strip moving in the conveying direction.

The following are to be mentioned in particular as coatings: paints, in particular powder coatings, one-component or two-component wet coatings, both water-based and based on organic solvents, coatings for corrosion protection, coatings for pretreatment and for the functionalization of metal surfaces, conductivity pastes and photoresist.

The paints are substances that are at least partially dryable and / or crosslinkable with radiation. Paint systems are typically systems that contain at least one additive, preferably one additive and one binder, as discussed in detail below. In many paints, radiation curing often takes place by polymerizing the binder contained in the paint.

An example of this is the polymerization of low-viscosity coating materials with binders of reactive monomers, oligomers and prepolymers started optically via photoinitiators, for example free-radical or cationic polymerization or the crosslinking of linear polymers with reactive side chains. Wet lacquers or powder lacquers can be used for the process according to the invention. Water-based paints and solvent-based paints are referred to as wet paints. Wet lacquers can be one-component lacquers, such as UV lacquers, and two-component lacquers, it being possible to use water-based lacquers or else based on organic solvents. Combinations of these are also conceivable for multilayer structures. Furthermore, weldable coating systems are also of interest for the above-mentioned coil coating processes.

Depending on the solvent content, solvent-based paints are divided into conventional, solvent-based paints, low-solvent and solvent-free paints. The solids content of low-solvent paints is greater than 70% by mass; with a solids content of less than 70 mass% one speaks of solvent-based paints. The term high-solids is also used for high-solids paints such as spray paints.

Low-solvent and solvent-free lacquers are divided into one and two-component systems according to the type of curing reaction. In the case of one-component paints, the polymerization and thus the crosslinking commence after the addition of initiators and accelerators or through the action of UV or electron beams. For example, vinyl chloride polymers or copolymers and unsaturated polyester resins such as low molecular weight hydroxyl-bearing acrylate, alkyd and polyester resins are used as one-component paints. Two-component paints harden through an addition reaction, in which, in contrast to the one-component paints, no environmentally harmful fission products are released. The binders are usually epoxy resins in combination with hardeners or polyisocyanates in combination with hydroxyl-containing resins.

Powder coatings are thermoplastic or thermosetting plastics that are applied in powder form to substrates. Here are different Application methods such as electrostatic powder spraying, electrostatic whirl sintering, bulk sintering, whirl sintering, rotary sintering or centrifugal casting are used. For example, epoxy resin powder, powder of saturated polyester resins, polyacrylate powder, polyethylene powder, polyvinyl chloride powder, polyamide powder, cellulose acetate butyrate powder, chlorinated polyether, ethylene-vinyl acetate mixed polymer powder or polymethacrylic acid methyl ester powder are used as powder coatings.

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 UV initiators can be dispensed with in many cases, but UV lacquers of this type can nevertheless be dried using the method according to the invention.

Nowadays, large quantities of solvents are used in paints and varnishes, since they often use polyester resin as a binder. However, the trend is that increasingly for different reasons such as for environmental protection and to avoid unpleasant smells, attempts are being made to use varnishes with resins that require relatively little solvent, such as acrylic resins. The low-solvent coating systems (high-solids and water-thinnable systems) should therefore be used increasingly in the future. The disadvantageous longer drying time of these systems can be avoided by using the method according to the invention.

All customary radiation-curable binders or mixtures thereof which are known to the person skilled in the art can be used as binders which can be crosslinked by radiation-induced processes in the process according to the invention. They are either binders that can be crosslinked by radical polymerization or can be crosslinked by cationic polymerization. In the former, radicals are generated by the action of electromagnetic radiation on the binders then trigger the crosslinking reaction. In the case of the cationically curing systems, Lewis acids are formed by the irradiation from initiators, which then trigger the crosslinking reaction.

Depending on their field of application, other coating compositions contain appropriate additives such as polymers, in particular crosslinking agents, catalysts for crosslinking, initiators, in particular pigments, dyes, fillers, reinforcing fillers, rheology aids, wetting and dispersing agents, adhesion promoters, additives for improving the surface wetting, additives for improving the surface smoothness , Matting agents, leveling agents, film-forming aids, drying agents, skin-preventing agents, light stabilizers, corrosion inhibitors, biocides, flame retardants, polymerization inhibitors, in particular photoinhibitors or plasticizers, as are customary and known, for example, in the paint industry. The choice of additives depends on the desired property profile of the coating agent and its intended use.

The coating compositions can also 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, molybdenum orange and red, chrome orange and red, iron oxide red, chromium 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 for example azo pigments, indigoids, dioxazine, cliinacridone, phthalocyanine, isoindolidone, perylene and perinone, metal complex and alkali blue Pigments can be components of the coating compositions.

The coating compositions can also contain luminescent pigments to produce a metallic effect. Metal platelets can be used in particular, preferably aluminum plates, which give a special optical effect through 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 can also contain luminescent pigments for producing metamerism effects. Here, for example, pigments can be used to create a pearlescent sheen. In particular, bismuth oxide chloride, titanium dioxide mica and lead carbonate are to be found.

As interference pigments for heat protection, the coating compositions can contain pigments with high reflectivity for IR radiation, in particular lead carbonate and titanium dioxide mica. Destructive interference leads to the extinction of essential radiation components, whereby thermal protection is achieved.

Within the scope of the invention, the coating compositions can also contain pigments for corrosion protection. Lead (II) orthoplumbate, chromate pigments, phosphate pigments, zinc dust or lead dust are preferably used.

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

The proposed method is particularly suitable for the production of a functional coating for the production of thin-film transistor arrangements, in particular for liquid crystal display arrangements, of separator membranes for electrochemical elements, in particular of 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 which has a substrate and a dried and / or crosslinked coating agent which is applied on one or both sides. The substrate is selected in particular from a thermoplastic substrate, a metal foil or sheet, a plastic film, a glass plate, a composite material system such as a wood veneer, a laminate such as capacitors or displays. The coating agent is preferably selected from a lacquer, in particular powder lacquer, a one-component or two-component wet lacquer, both water-based and organic solvent-based, a coating for corrosion protection, a coating for pretreatment and for the functionalization of metal surfaces, a conductivity paste or a photoresist ,

A suitable arrangement for producing a thin layer structure from a band-shaped, flexible, in particular quasi-endless, carrier with at least one functional coating firmly connected to the carrier, which has a thickness that is in particular in the order of magnitude of the thickness of the carrier, with the steps the formation of an initial layer structure by the surface application of a coating agent to the carrier and the irradiation of the carrier provided with the coating agent with electromagnetic radiation, which has an active component in the near infrared range, to form the functional coating from the coating agent while being combined with the Carrier including drying and / or thermal crosslinking, preferably has a feed and feed device for the carrier, which can in particular comprise a carrier supply roll and a roller feed device, a feed and layer ore Diffraction device for, in particular continuous, supply and application of the coating agent to the carrier and a radiation device which is arranged downstream of the supply and layer generating device and faces the carrier provided with the coating agent and has an active component in the near infrared range. The radiation device is preferred. device designed as a halogen lamp, in particular operated at elevated operating temperature.

In addition, in particular a means for setting 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 addition, the method according to the invention is preferably carried out using a device which has an essentially closed device through which the material strip provided with a coating agent is conveyed on one or both sides, in which at least one emitter is mounted and the inner walls of which are equipped with at least one electromagnetic one Radiation reflecting device, such as are provided with a reflector.

In principle, it is sensible in all cases to equip the system with reflectors to increase efficiency and to optimize energy, so that a closed radiation space is generated where emitters are used. In addition to counter reflectors, it is also useful to provide side reflectors and reflectors arranged transversely to the conveying direction.

According to a preferred embodiment, the side reflectors can be adjusted, for example by means of displacement devices, and can be adapted to the width of the material strip to be coated while 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 independently of the width of the material strip. When processing a strip of material that is smaller than the maximum width that is possible for the system, the emitters located outside the supplied side reflectors are not used. In this way, optimal and thus energy-saving drying or crosslinking of the coating agent can always be achieved. Such an adjustment Solution of the energy sources used for drying or for crosslinking is not possible with conventional methods and is a major problem.

For coating material strips on both sides, it is useful, depending on the type of coating agent or material, to arrange emitter modules only on one side of the material strip or on both sides of the material strip. If the electromagnetic radiation used for drying or crosslinking can be selected so that in addition to the coating agent, the material strip can also be penetrated by the radiation, it is sensible for investment reasons to arrange emitter modules only on one side of the material strip. To increase the effectiveness of the system, it then makes sense 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 strip and the layers of the applied coating agent back through the coating agent and the material strip.

With radiation-impermeable material strips and in cases in which the crosslinking of the coating agent is essentially caused by photo reactions, an arrangement of emitter modules on both sides is advantageous.

For drying and / or crosslinking the coating agent, the device has at least one emitter, which in particular contains a thermal radiating body, in particular an incandescent lamp or a halogen lamp, which is operated in particular at an increased operating temperature. In a preferred embodiment, the emitter is provided by a tube radiator formed with a filament extending in a radiation-permeable tube, in particular in a quartz glass tube, as a thermal radiant body.

Instead of the thermal radiation body, alternative radiation sources such as laser diodes, plasma emitters, UV emitters or radiation sources based on other physical effects can also be used. If necessary, it is also possible to arrange a plurality of emitters, preferably parallel to one another, 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 band. This has the essential advantage that the irradiance remains homogeneous over the entire material band, both in the conveying direction and in the direction perpendicular to it, even if, for example, the aging process of the emitters or another effect changes the radiation homogeneity along the longitudinal direction of the emitters , assuming that this change is the same for all emitters.

According to a further preferred embodiment, a special linear arrangement of the emitters is selected for the irradiation of linearly, for example, lattice-shaped, endlessly conveyed material belts in the conveying direction, so that in each case an emitter or is arranged essentially parallel to a material part of the lattice-like material belt arranged parallel to the conveying direction optionally a series of emitters arranged one behind the other. In addition, in order to increase the efficiency, the radiation emitted by the emitters can be focused on the material parts by appropriate reflective devices. Furthermore, the arrangement of a reflector on the side opposite the material strip in relation to the emitters is desirable in order to increase the efficiency of the system. In order to also efficiently dry or crosslink coating material which is applied to material parts running transversely to the conveying direction, linear emitters oriented transversely to the conveying direction are additionally provided which can be moved with the material parts at their conveying speed. Further details of this special embodiment can be found in one of the applicants under the title “Method and device for heating continuously conveyed, lattice-like material or similar structures "with the application number DE 10062633 filed application.

According to a further embodiment, the space in which volatile components of the coating agent, such as solvents, for example, escape during the drying process, is separated from the emitters by a quartz glass pane. This can prevent solvents from igniting due to the high temperatures on the outer surface of the emitter body. According to a further preferred embodiment, two quartz glass panes arranged next to one another are provided between the material band and the emitter or emitters, between which an additional cooling gas, e.g. Nitrogen gas flows to prevent heating of the solvent more effectively.

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 power adjustment or control is additionally provided, the latter preferably comprising means for adjusting the distance between the radiation source and the layer structure.

The gas flow generating device is preferably designed in such a way that a gas pulse which is directed essentially parallel to the surface of the material strip and which passes over the irradiation device, particularly dry and cold gas flow, is generated with a high pulse.

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

Advantages and advantages of the invention with regard to the coil coating method result from the following description of a preferred exemplary embodiment of a coil coating device with reference to the single figure. This shows a sketch of a coil coating device 1 for coating a quasi-endless steel sheet 3, which is wound onto a coil 5, and for drying the coating. The coil 5 is set in rotation by an electric drive 7, and the sheet 3 is thereby moved under a spray coater 9 and an NIR drying section 11.

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

The NIR drying section 11 comprises a solid Al reflector 15 with a plurality of reflector sections 15a which are approximately W-shaped in cross section and which are internally water-cooled and, for this purpose, connected to an external cooler (not shown) via cooling water lines 17. In the center of each reflector section 15a is an elongated tubular halogen filament lamp 19. Preferably, each elongated halogen lamp is assigned a reflector section with a partially elliptical, partially parabolic or essentially W-shaped cross section. The halogen filament lamps 19 are supplied with current by an irradiation control unit 21 and controlled in such a way that they emit NIR radiation with an intensity maximum in the range between 0.8 μm and 1.5 μm with a radiator temperature above 2900 K.

The radiation control device assigned to the radiation 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 setting the temperature in the layering agent to a value above 200 ° C, in particular to a value in the range between 200 and 250 ° C.

Arranged in the AI 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 radiation control unit 21. The radiation is controlled in such a way that an essentially constant temperature is maintained in the coating, which temperature is selected as a function of the physical and chemical properties of the starting material 13 ′ of the corrosion protection or primer layer 13 and is typically around 200 ° C.

By suitably controlling the drive 7, the throughput speed of the steel sheet 13 through the irradiation zone A is set such that a residence time of the aqueous solution 13 'in the irradiation zone A of a few seconds is obtained, which is necessary for the complete evaporation of the solvent component and for the thermal crosslinking of the layer 13 is sufficient.

The sheet is typically conveyed through the drying device 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, one is then Irradiation device with a length of 2 to 5 meters and more than one megawatt, preferably 2 to 5 MW, to use power consumption which has a radiation power density of more than 500 kW / m ² , in particular more than 750 kW /, on the surface of the coating to be dried or crosslinked. m ² .

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

In particular for use with powder coatings, the method preferably does not require an active gas flow supply to remove evaporating coating components; essentially convection over the heated coating is used for this purpose. When drying liquid systems, however, a gas stream sweeping over the surface, in particular an air stream generated by a suitable fan, can certainly be used.

For quality control when carrying out the process, 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.

The present invention is not limited to the previously described embodiments, but also extends to other possible uses of the method within the scope of the skills of a person skilled in the art.

Claims

claims

1. A method for producing a coating of quasi-endlessly conveyed and moved in the conveying direction, in particular band-shaped, flexible material strips, in which a coating agent is applied to at least one side of the material strip and is at least partially dried and / or crosslinked by means of electromagnetic radiation, the electromagnetic radiation has a significant active component in the wavelength range of the near infrared.

2. The method according to claim 1, in which 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 radiation energy substantially uniformly over its layer thickness.

3. The method according to claim 1 or 2, wherein the maximum intensity 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 strip.

4. The method according to any one of the preceding claims, in which coating agent applied to both sides of the material strip is dried or crosslinked on both sides of the material strip substantially simultaneously.

5. The method according to claim 4, in which the coating agent applied on both sides is dried or crosslinked essentially simultaneously with at least one radiation source arranged on only one side of the material strip.

6. The method according to any one of the preceding claims, wherein the drying and / or crosslinking of the coating agent is carried out at least partially by a photo reaction.

7. The method according to any one of the preceding claims, in which the power density of the electromagnetic radiation is set by the distance of the radiating body from the material band and / or via the temperature of the radiating body, preferably above 2500 K, preferably above 2900 K and particularly preferably above 3200 K. becomes.

Method according to one of the preceding claims, in which the power density of the electromagnetic radiation is above 100 kW / m ² , preferably above 200 kW / m ² and particularly preferably above 500 kW / m ² , in particular above 750 kW / m ² lies.

9. The method according to any one of the preceding claims, in which the essential active component of the electromagnetic radiation is in the wavelength range from 0.8 μm to 2 μm.

10. The method according to any one of the preceding claims, wherein the irradiation with electromagnetic radiation lasts less than 30s, preferably less than 10s, in particular less than 5s and particularly preferably less than 2s.

11. The method according to any one of the preceding claims, in which the surface of the material strip is pretreated, preferably heated, before the coating agent is applied.

12. The method according to any one of the preceding claims, wherein the volatile constituents separated from the coating agent are removed by means of a gas stream sweeping over the material strip.

13. The method according to any one of the preceding claims, wherein the material band is a metal band, in particular a bright, galvanized, or nickel-plated steel sheet, in particular a body panel for the automotive industry or a housing panel for household appliances.

14. The method according to any one of the preceding claims, wherein the coating agent is a lacquer, in particular a wet or powder lacquer, a coating for corrosion protection, for pretreatment and / or for functionalizing the surface of the material strip, a conductivity paste, or a photoresist.

15. Coated substrate, producible by means of a method according to one of claims 1 to 14, comprising:

- A substrate, selected from a thermoplastic substrate, a metal foil or sheet, a plastic film, a glass plate, a

Composite material system, a laminate; and

- A dried and / or crosslinked coating agent which is applied on one or both sides, the coating agent being selected from a paint, in particular powder paint, a one-component or two-component water-based wet paint or on the

Basis of organic solvents, a coating for corrosion protection, a coating for pretreatment and / or for functionalizing the surface of the material strip, in particular of metal surfaces, a conductivity paste, a photoresist or a combination of two or more thereof.

16. Device for carrying out the method according to one of claims 1 to 14, in particular with the steps of applying a coating agent and drying or crosslinking the coating agent to form a coating, which are each carried out on the continuous material strip, which comprises:

- A feed and feed device for the material band,

a supply and layer generation device for, in particular continuous supply and application of the coating agent on the material strip, a radiation source for generating electromagnetic radiation with a high power density and / or in the near infrared range.

17. The apparatus of claim 16, wherein the layer generating device is substantially closed and the inner walls are provided with at least one electromagnetic radiation reflecting device.

18. The apparatus of claim 17, which further has side walls that are deliverable to the material belt being conveyed and below

Formation of the irradiation area can be adapted to the width of the material strip.

19. Device according to one of claims 16 to 18, in which at least one emitter is provided on each side of the material strip.

20. Device according to one of claims 16 to 19, in which the electromagnetic radiation is generated by at least one emitter with a thermal radiation body, in particular an incandescent lamp or halogen lamp.

21. Device according to one of claims 16 to 20, wherein the electromagnetic radiation is generated by at least one emitter having a laser diode or a plasma emitter.

22. Device according to one of claims 16 to 21, wherein the emitter has a substantially elongated shape, and is aligned along the conveying direction of the material band.