EP1327844A2 - Process and apparatus for treating a substrate and/or a coating material on a substrate - Google Patents

Abstract

A substrate (16,52) or a substrate with a coating (50) is prepared and then either cured, cross-linked and/or dried using microwaves (60,62) with two or more wavelengths. Independent claims are made for: (1) the process equipment which includes a microwave source (36), an emitter (38) and control unit (66) for producing microwaves with two different wavelengths; (2) a use of a microwave tunnel oven (10) for treatment of a coating material on a substrate and/or a substrate.

Description

The invention relates to a method and an apparatus for treating a Coating material on a substrate and / or a substrate and a new one Use of a microwave oven.

When treating the coating materials and / or the substrates, it can be to harden crosslinking and / or drying the coating materials and / or Trade substrates.

The coating materials can be all types of Trade coating materials, for example all types of paints and Powders.

The substrates can be metal, plastic, ceramic, wood and glass and mixtures, combinations or compounds of these materials act.

Methods and devices for drying Known paints.

In particular, there are also methods and devices for drying paints become known on metal surfaces. The are traditionally Coating materials, for example in large series production in the Automotive industry, initially applied in separate areas and then dried. The application is traditionally done either by means of an immersion bath or with the help of manual application or by means of automatic application, e.g. using spray robots. In a subsequent one Step then the painted metal parts are provided in separately Drying chambers using hot air at temperatures of around Dried 80 ° - 200 ° C. The painted metal parts can be Bodies or small parts. The above drying step is associated with considerable energy expenditure, so that the resulting Energy costs have a large share in the overall cost of painting.

The drying of paints by means of microwaves is known from the "Deutsche Farben-Zeitschrift, 23rd year 1969, No. 12, page 585, 1969". Here, with the aid of microwaves in the range from 10 ⁸ to 10 ¹⁰ Hz, film material is heated, which essentially brings about the conversion into the solid state. The heating occurs due to the dielectric losses that occur, but only varnishes that contain water as a solvent are suitable.

From the article by Brä Bridegroom, Graf, Emmerich, Schüller "Microwave drying of water-based paints, dielectric properties of paint systems, MO, vintage 55 (2001) 3, Carl Hanser Verlag, Munich "is the drying of water-based paints known on plastic. The dipole property of the water-based paints for the Drying used.

From the essay by Groom, Hegemann and Schüller "Microwave drying of water-based paints, process parameters and qualitative comparison with the Umlufttrocknung, MO, year 55, (2001) 8, Carl Hanser Verlag, Munich "is the Drying of water-based paints on plastic using microwaves is known. Here too, the dipole property of the water-based paints is used for drying.

From the patent "Patent Abstracts of Japan, C-1021, 1993, Volume 17, No. 46 JP 4-260472 A "it is known to use a special lacquer which is a through Contains microwavable powder. This leads to the heating of the powder for drying the paint, the resins of the paint and the However, substrate materials must be heat-resistant.

FR 2458323 describes a method for coating a substrate with which a thin layer of a coating is applied to the substrate is applied. The coating on the glass or a similar fabric existing substrate is heated by applying microwave energy, this energy being in a selected frequency range that determined Selectively excites components of the coating. The regulation is the Microwave radiation designed so that the fed into the drying room Microwave radiation is changed in frequency to the extent that the Temperature of the coating maintains a constant nominal value. This will a pyrometer is used. At the same time, the paints are specially made for the microwave radiation used, for example, by the introduction of Coal dust modified. For the microwave, frequencies in the range of 2.45 GHz is used, only non-conductive substrates being used.

DE 4121203 A1 discloses a method and a device for drying of water-soluble dispersion varnish on paper or cardboard webs or sheets with the help of microwaves. In doing so, commercially available and approved Oscillators are used, the microwave energy in multiple arrangement Couple the waveguide. It is dried in a pass, after drying residual moisture remains when using the lowest energy level.

DE 19626512 A1 describes a continuous microwave oven for baked goods known with a housing having an inlet and an outlet which is a conveyor belt for transporting the baked goods in that extends through and out of the housing, the at least one Microwave device comprising a microwave generator which can be cooled by cooling air having a transmitter antenna, is arranged in a waveguide, which of the transmitter antenna conducts emitted microwaves and in the range of Conveyor belt has a radiation opening for radiating the microwaves, the cooling air cooling the microwave generator via at least one im Waveguide trained breakthrough in the waveguide and from it Beam opening is inflatable.

DE 19721461 A1 also describes a process for drying paints metallic or non-metallic individual parts or assembled assemblies any structure in the continuous process or in stationary operation in one heated drying room known, being the heat source in the drying room at least one microwave module for generating by means of waveguides defined exit openings in the drying room introduced microwaves is used, air to flow around the individual parts in the Drying room is introduced, the air introduced with an additive is enriched with dipole character such that the air mixture has a relative Proportion of additive within a specified controllable range of 20 has up to 90%, and the proportion of additive in the drying room is observed.

From US 4,765,773 a motor vehicle is known which has a trailer has, the color applied to a road surface by means of a in the If the microwave radiation device is attached, it dries.

A method is known from US Pat Lacquer applied to the glass substrate can be dried using a microwave.

From US 4,728,762 is the heating of food by means of a Microwave oven disclosed. This document discloses a method in which Air is heated using the microwaves and parallel to the microwave for heating the food is used.

DE 19616692 describes a method and a device for drying Colors on plastic films using microwaves are known.

DE 4433904 discloses continuous drying of colors using a microwave known on paper or the like.

The drying of paints with the aid of infrared radiation is also known.

From the article "K.K.O Behr, M. Sedlmayer, Fast and gentle drying working principle The NIR technology "mo", January 98 "is the drying of paints using infrared radiation with a wavelength between 0.76 µm and 1.2 µm known.

From "K.K.O. Behr, M. Sedlmayer, Drying powder coatings within seconds, Special print from JOT, February 1998 "is the use of infrared radiation for Drying of paints in a temperature range from 120 ° C to 300 ° C known. The high radiation intensity of the infrared radiation becomes Achieving high energy densities exploited.

A disadvantage of the above-mentioned drying processes and devices also the high energy consumption for drying are the long ones Drying times that are necessary and furthermore the need having to use special paints. For example, when it comes to infrared radiation furthermore disadvantageous that due to the formation of shadows only Components of simple geometric shape can be dried.

The object of the invention is to provide the known treatment methods and improve devices.

This object is achieved according to the invention by a method according to claim 1, by a device according to claim 30 and by using a Microwave oven for treating a coating material on a substrate solved according to claim 42.

Microwaves are understood here to mean an electromagnetic wave, the one Has a wavelength between 0.1 mm and 1000 m. Are preferred in the Invention microwaves with a wavelength between 3m and 30 m used.

With the method according to the invention, the device according to the invention and All types of coating materials can be used according to the invention be treated. This includes water-thinnable, solvent-based ingredients Multi-component paints on a wide variety of raw material bases, e.g. on Epoxy or polyurethane base, and also stove enamels, synthetic resin lacquers, oxidative-curing lacquers, moisture-curing, UV-curing lacquers and Powder coatings.

With the invention, the coating materials on the substrates alone, the Coating materials on the substrates simultaneously with the substrates or only the uncoated or coated substrates are treated alone.

The advantages of the invention are in particular that due to the use of microwaves according to the invention for the treatment of Coating materials on the substrate an inexpensive and above all very fast method is provided, applied to metal surfaces Dry layers of paint.

In addition, it is advantageous in the invention that it is used in the treatment of glass fiber reinforced plastic components, especially based on SMC (sheet molding compound) to reduce outgassing more volatile Components comes from the plastic component. As a result, one subsequent painting of the component even with conventional convective Drying leads to lacquer films, which are the usual and referred to as popups the degassing of the plastic is not due to surface defects aufweißt. This in turn means that there is considerably less waste arises. It is also possible to pretreat the components using a microwave Avoiding outgassing and drying the paintwork of such Combine component in a single process step. That is, becomes a unpainted component painted and then the paint in the here described way dried using microwave radiation, so Pop-ups in the paint film are also prevented.

It is also particularly advantageous that the Throughput time for the treatment of coating materials on substrates, especially for drying paints on plastic or metal surfaces is significantly reduced. This increases the economy according to the invention Devices over the prior art. In addition, the Using microwaves requires considerably less energy than with the Prior art method for drying lacquers on substrate was necessary. This also increases the economy of the invention Devices. Finally, the footprint is also called space footprint Devices according to the invention less, since the microwaves small-scale magnetrons can be generated and on long ventilation distances can be dispensed with.

As a particular advantage of the invention it is to be seen that due to the treatment according to the invention the quality of the cross-linked, hardened and / or dried coating compared to that known from the prior art is increased. For all of the above Coating materials can have an increased chemical and demonstrate mechanical resistance. Even the optical properties coatings treated in accordance with the invention are of better quality than in the state of the art.

Overall, thanks to the invention, coating material can be clearly seen Dry cheaper than before. Because the total cost of industrial Painting processes become crucial due to the drying of the paint Expenses determined. When using convective drying processes of the The state of the art is generally systems with extensive evaporation, Drying and cooling zones required. Among other things, these cause substantial Energy costs as well as costs for depreciation on plants and buildings. Due to increasing demands on environmental compatibility Coating materials are increasingly coming to a greater extent than before water-dilutable coating materials are used. However, these require in Compared to conventional paints a greater energy input when Drying process. The process step is due to high energy prices Paint drying important for the economy of the whole Coating process.

The invention allows a greater energy input and Realize cost savings in the drying process. Because the invention enables it, both when using conventional as well as from water-thinnable paint systems, the drying time, drying time and cooling time to reduce. The invention includes the knowledge that it Offers the possibility of selective paint drying, i.e. a paint drying under largely avoiding heating of the substrate used. Though have also recently found ultraviolet, infrared and microwave drying more attention; is the use of ultraviolet and infrared drying processes however due to the shadow formation that occurs on drying limited geometrically simple components. This is the one used Microwave radiation of the invention is not the case.

The selection of raw materials to formulate a microwave radiation coating material to be dried is not subject to the restrictions which apply to the selection of raw materials for the formulation of coating materials with UV or IR radiation can be dried. Consequently, too the range of paint services available for drying with a microwave Coating materials are significantly less restricted than those with UV and IR radiation coating materials to be dried.

Microwaves have already been used for drying in the prior art used, however, the overheating of metallic substrates was not to avoid leaving microwaves for the treatment of coating materials could not previously be used on metal or metal-containing substrates. Through the invention, the drying of coating materials, such as e.g. of paints, on metal or metal-containing substrates.

The invention also avoids the disadvantages of shadowing the prior art Technology, since the shadow formation itself is avoided by the invention.

The invention includes the finding that due to the use of at least two wavelengths, preferably an entire wavelength spectrum, is advantageously possible to radiate a higher output overall and thus overall to achieve a higher energy input into the paint to be dried. By using several microwave modes, heating in the Coating material allows, which only dries the above mentioned coatings on metal or metal-containing substrates is possible.

Electromagnetic radiation in the above Wavelength range of the microwaves unlike ultraviolet or X-rays, it does not have an ionizing effect. By However, absorption of microwave radiation becomes the absorbent material heated. This happens above all through one in the material Molecular movement, which in part depends on the dielectric properties of the Material can depend. This applies to both the coating material and the substrate. It comes under the influence of the electric field of the microwaves in every material about changes of state. For conductors such as for metals, there are displacements of freely moving electrons inside the material and thus for the formation of an electrical opposing field up to compensation of the outer field. In non-conductors, however, under the influence of a electric field charges shifted as far as the restoring forces allow in the material. The speed of the process determining step for the absorption of microwave energy always the Relaxation of the excited states after switching off the microwave field.

The polarization of a material in the electric field occurs according to different Mechanisms whose importance depends heavily on the frequency of the acting Field. For example, by exposure to ultraviolet or infrared radiation the resonance frequencies of electron and Atomic polarization due to the relatively short prevailing there Relaxation times stimulated. The polarization must be distinguished from this on the basis of orienting polar molecules as well as due to ion conduction, which Range of the microwave radiation used according to the invention Have resonance frequencies. The position of the absorption maxima within the microwave frequency spectrum used by the Mobility of the particles contributing to the polarizability of the material certainly. As a result, the position of the absorption maxima is also dependent on the molar mass of the considered particles and the temperature of the material.

In addition, in heterogeneous systems, for example in metal-plastic connections, an interphase polarization possible, which influences the Has absorption behavior of such a material.

Through the steps described in the input and Turning off the magnetron and using the anode of the magnetron as a sensor for the microwave energy reflected by the material but also treat such a composite material according to the invention. That's the way it is thanks to the above knowledge of the invention and the Process steps according to the invention described on the following pages For example, so-called SMC (Sheet Molding Compounds) materials dry, for their manufacture polyester resin mats pressed with metal threads become. So far, the drying of such materials or drying of paints on such materials in the prior art is possible, but with high expenditure of time, space and energy required and led to high Scrap rates. However, such materials are in the modern technology increasingly important materials. The Invention can thus not only dry paint on metal substrates, but is also able to apply paint simultaneously in a single drying pass the metal parts and on the plastic parts of a metal-plastic connection dry without the surroundings of the metal parts remaining moist or the metal parts get too hot.

The frequency spectrum according to the invention can be particularly advantageous realize if a microwave source used, preferably a used one Magnetron, always on, more preferably on and off all the time becomes. It has proven to be advantageous if these inputs and Switch-off operations are carried out with a period of 5 ms. This Period ensures an optimal drying process of the above Paints. Especially with water-thinnable and solvent-based paints is advantageously achieved that the solvent the paint before crosslinking the Leave the paint so that no stoves can appear on the paint.

In a particularly preferred embodiment of the invention, the Microwave energy from two sides in a stationary range of action Microwave sources irradiated. It is further preferred if two Microwave sources are aligned and only one of the two opposite microwave sources with the help of the invention Control means is switched on and off periodically.

In a further preferred embodiment of the invention, using a Sensor the starting from the stationary range of action of the microwaves Reflection captured. In this way it can be determined whether stationary area of action is an object to be dried. This will the device is preferably calibrated so that the sensor on the one hand no stationary area of action to be dried and on the other hand stationary on an object to be dried Effective range is calibrated. If an object to be dried now enters the stationary area of effect, the sensor can determine that such is present in the stationary sphere of activity. The magnetron will then preferably switched on every 5 ms and then switched off again. Provides the sensor determined that there is no object to be dried in the stationary Effective range of the magnetrons, the magnetrons are preferred only switched on and then off again every 500 ms. In this way energy is saved.

It is particularly preferred if the sensor is the anode of the Magnetrons. Through an appropriate one connected to the anode Control circuit, the reflected microwave energy can be detected and adjusted evaluate the aforementioned calibration in such a way that it can be determined whether there is an object to be dried in the stationary area of action or not. In this way, the provision of a avoid additional sensors.

In a particularly preferred embodiment, the device is like this calibrated that the sensor, preferably the anode of the magnetron, not only can detect whether there is an object to be dried in the stationary Effective area is located, but can also capture what type of Subject matter. So can be done with the previously Calibration step the reflections detected by the anode of the magnetron various items stored and the corresponding item be assigned. Now such an object occurs in the stationary Effective range of the magnetron, so by the reflection of the Subject caused change in the anode current and the corresponding Control circuitry for processing such a change to be determined what object it is. After that, it is preferred possible, the total power of the emitted microwave energy but also the Composition of the frequency spectrum on the respective object to adjust adjusted. For example, in the case of exterior mirror housings from Automobiles, a different microwave energy and a different frequency spectrum displayed to enable optimal drying than this at fine jagged metal parts such as windshield wipers.

In this case, it is in particular also possible, for example made of plastic existing windshield wipers with metal threads, i.e. combinations to dry out of metal and plastic, as already mentioned above.

In addition, it is even possible to use the aforementioned function of the anode Sensor for the microwave energy reflected from the object that adaptive radiation of microwave energy by the Magnetron can be reached, depending on whether more at the time or less retroreflected energy is detected by the anode. So it can also an irregular switching on and off of the magnetron according to the energy recorded by the anode. It is so in particular possible that in the event of a sharp increase in the retroreflected and from the Anode detected energy, for example, due to a metal part on the material the radiated magnetron energy is immediately reduced, so that excessive heating can be avoided. In particular on this Any metal-plastic combination can be made using the device according to the invention and with the aid of the method according to the invention to treat. In particular, paint can be applied to such a composite component Dry metal and plastic using the invention.

In another preferred embodiment of the present invention several magnetrons or preferably several opposing pairs of magnetrons one behind the other switched to carry out the drying. In this way it can be advantageous a staggering of the microwave power within the stationary Effective area along a movement path of the to be dried Reach object. It can also ensure this way be that a possible loss of performance at the beginning of the Movement path of the magnetron lying to be dried compensated by a magnetron behind it in the direction of movement can be.

In a particularly preferred embodiment of the invention, this is Staggering the microwave power in the direction of movement of the patient to be treated Realized zones lying one behind the other. For example, a constant microwave fundamental frequency of about 2.5 gigahertz is an adjustable one and modulating frequency increasing from zone to zone. In this way the above-mentioned different absorption maxima different materials and material combinations, in which each Zone a particularly advantageous to the absorption maxima of the to be dried Materials matched modulation frequency. Here it has turned out to be proven beneficial for drying paints on plastic materials when five zones are set up, in which the basic frequency of about 2.5 Gigahertz in ascending order with modulated frequencies of about 1.2, about 1.6, about 1.9, about 2.1, about 2.5, and about 3 gigahertz is modulated. The Plastic substrates can also contain metal.

If, on the other hand, a lacquer is to be dried on ceramic or wood, it should still another zone with a base frequency of about 2.5 gigahertz modulated frequency of about 900 megahertz can be set up as this has proven to be particularly advantageous for ceramics and wood.

Overall, the microwave drying according to the invention thus offers the advantage that the paint drying directly on the chemistry of the to be dried Coating materials and substrates are matched and tailored.

It should also be mentioned here again that those treated according to the invention Coating materials and substrates do not require a subsequent flash-off time because cooker-free dry lacquer surfaces are created.

Overall, the invention thus offers one treatment, in particular one Drying paints on substrates with selective heating of the paint low thermal stress on the component and thus new ones Lacquer / substrate pairing enabled. Since the substrate is not heated, that is Energy consumption is also lower since there is no heat loss for the Substrate heating is consumed. At the same time, a smaller one Consumption of cooling capacity and thus again lower energy consumption required, since the substrate itself does not need to be cooled after drying, because there is no energy or only a negligible amount of energy is entered.

In a further embodiment of the invention, the stationary Area of effect over the waveguide over which the magnetron Microwave energy radiates into the stationary area of action, including the Waste heat from the magnetron supplied. This way, in the stationary Effective range an air temperature of below 120 ° C, preferred between 60 and 80 ° C can be reached. This is particularly advantageous for Drying coating materials on heat sensitive substrates, such as for example plastics. This temperature has proven to be optimal for drying of paint on metal or metal-containing substances. Because on this In this way it is achieved that the surface of the paint does not dry first, while the inside of the paint is still damp. Rather, it achieves that the drying of the paint starts inside the paint and continues continues on the outside so that the paint dries completely becomes.

It is also advantageous if with the help of before and / or after stationary area of action concentrically around a movement path of the Drying objects arranged cooling hoses cooling the air is carried out in front of and behind the stationary effective area. To this If the air humidity is too high, targeted condensation of the Humidity can be made on such cooling hoses without it a condensation on the object to be dried and thus one disadvantageous droplet formation on the object to be dried can. It is preferred if using such coolants or other devices in the stationary area of effect a humidity of about 50% is maintained constantly. This humidity is special advantageous because in this way the microwave energy in the optimal Paint is entered and also the reflection of the object to be dried can be optimally detected by the anode of the magnetron.

It is further preferred if in the method according to the invention or the device according to the invention within the stationary range of action constant air flow is maintained to heat concentrations to avoid certain places on the object to be dried.

Furthermore, it is advantageous and easily possible thanks to the invention, the Drying the paints on the metal surfaces in a continuous process because the microwaves have a certain effective range can be limited without excessive loss of energy. In addition, such a continuous process can be a very large one Number of small parts in particular can be dried in a relatively short time because with the use of microwave ovens according to the invention for drying the paints are guaranteed to dry very quickly.

In addition, it has with the invention, in particular with the use of the microwave oven described below, proved that the use of Microwave dried lacquer layers in no time down to the Metal surface are dry without causing excessive and causing harmful heating of the metal parts. The metal parts can thus can be processed immediately since there is no need to wait for cooling.

The invention thus sets itself against long-held prejudices against use of microwaves when drying paints or varnishes on metal surfaces time.

A continuous microwave oven which is provided with can be used particularly advantageously for carrying out the method according to the invention
a housing with an inlet and an outlet, and
a conveyor belt extending through the housing for transporting metal parts into, through and out of the housing and at least one microwave device which has a microwave generator which can be cooled by cooling air and has a transmitter antenna which is arranged in a waveguide which transmits microwaves emitted by the transmitter antenna conducts and in the area of the conveyor belt has a radiation opening for radiating the microwaves, the cooling air cooling the microwave generator being able to be introduced into the waveguide via at least one opening formed in the waveguide and being able to be blown out from its radiation opening.

In the continuous microwave oven used, each waveguide serves both to transport the microwave energy as well as to transport the cooling air, the comes from the microwave generator. For this purpose there are one in the wall each waveguide is provided with one or more openings through which the cooling air, which (immediately) flowed around and cooled the microwave generator into the Waveguide flows in. The now heated cooling air is through the waveguide transported to the metal via the radiation opening of the waveguide impinge. Separate cooling air lines are no longer required.

In particular, in the continuous microwave oven used Microwave device each have a waveguide and a ventilation duct with each other connected. The connection is made via the at least one breakthrough in the Wall of the waveguide. This breakthrough is in the direction of air flow viewed behind the microwave generator and in the direction of propagation Microwaves viewed behind the transmitter antenna. Conveniently, the waveguide runs in a straight line in the area of the at least one opening, during the ventilation duct, which is in the area of the microwave generator in particular runs parallel to the waveguide, behind the microwave generator runs obliquely towards the waveguide. The wall that runs diagonally to the waveguide of the ventilation duct conducts the cooling air through the at least one opening into the waveguide.

Fig. 1

eine Seitenansicht eines ersten Ausführungsbeispiels der Erfindung, eines Durchlauf-Mikrowellenofens für Metallplatten mit drei Zonen, innerhalb derer die Metallplatten Mikrowellenenergie und Warmluft ausgesetzt sind, wobei jede Zone insgesamt sechs Mikrowellenvorrichtungen umfasst,

Fig. 2

einen Schnitt entlang der Linie II-II der Fig. 1 zur Verdeutlichung der Anordnung der Hohlleiter und der Durchbrüche in den Hohlleiterwandungen zur Einleitung der erwärmten Kühlluft in die Hohlleiter, und

Fig. 3

eine Seitenansicht eines zweiten Ausführungsbeispiels der Erfindung, eines Durchlaufmikrowellenofens für Metallplatten mit zwei sich gegenüberliegenden Magnetrons.

Two exemplary embodiments of the invention are explained in more detail below with reference to the drawing. The figures show:

Fig. 1

3 shows a side view of a first exemplary embodiment of the invention, a continuous microwave oven for metal plates with three zones, within which the metal plates are exposed to microwave energy and hot air, each zone comprising a total of six microwave devices,

Fig. 2

a section along the line II-II of FIG. 1 to illustrate the arrangement of the waveguide and the openings in the waveguide walls for introducing the heated cooling air into the waveguide, and

Fig. 3

a side view of a second embodiment of the invention, a continuous microwave oven for metal plates with two opposing magnetrons.

In Fig. 1, a continuous microwave oven 10 is shown in side view, the one Has frame 12; on the top is a preferably made of Teflon Endless conveyor belt 14 is located on the upper run metal plates 16 in Direction of arrow 18 are transported. On the top of the frame 12 there is also a housing 20 which has an inlet opening 22 and a Has outlet opening 24 through which the metal plates 16 from Conveyor belt 14 are transported. The frame 12 is also with a Provided holding plate 26 which is arranged below the conveyor belt 14 and 1 the attachment of several arranged in groups Microwave devices 28 is used. The microwave devices 28 are shown in FIG arranged a total of three groups, each group six Microwave devices 28 includes (see Figure 2). Any microwave device 28 has a blower 30, on the housing 32 of which a cooling air duct 34 connected. A microwave generator 36 is located in the cooling air duct 34 (hereinafter also called magnetron), whose transmitter antenna 38 protrudes into a waveguide 40 arranged adjacent to the cooling air duct 34. The waveguide 40 is attached to the holding plate 26 from below, on which Waveguide 40 itself held the ventilation duct 34 with the blower housing 32 is.

As can be seen from FIG. 2, two of the six waveguides 40 end immediately below the conveyor belt 14, which for microwave energy and is permeable to air and in particular from each other spaced transport chains. The waveguide 40, the too both sides of the middle waveguide ending below the conveyor belt 14 40 are arranged, have angled substantially L-shaped Extension pieces 42, which protrude into the housing 20 and each other end opposite. At the two outer waveguides 40 are Waveguide extension pieces 44 connected, which are also inside the Housing 20 extend and immediately adjacent to each other above the Conveyor belt 14 end opposite the two middle waveguides 40. As illustrated in FIG. 2, the radiation openings 46 of all waveguides are thus located 40, 42, 44 of a group of microwave devices 28 around the metal plate around them from their sides, from below and from above To irradiate microwave energy. In this way, a lacquer layer 50, the is applied to the surface 52 of the metal plate 16 during the Stay in the continuous microwave oven 10 by means of the symbolic shown microwaves 54 completely dried.

As indicated in FIG. 1, the cooling air flowing around the magnetron 36 arrives laterally into the waveguide 40. For this purpose, the waveguide 40 in its opening adjacent to the ventilation duct 34 has several openings 48. In the area of these openings 48, the ventilation duct runs obliquely, which is indicated at 50 in FIG. 1. In this way it is about Radiation openings 46 of the waveguide 40, 42 and 44 not only microwave radiation 54, but also radiated warm air directed at the metal plate. Both Energy sources (microwave radiation and warm air) enter via and same channel, namely the waveguide to the metal plate, which increases the effort Feed lines or channels in the continuous microwave oven described here 10 is reduced.

FIG. 3 shows a side view of a second exemplary embodiment of the invention, a continuous microwave oven 10 with 2 magnetrons 36. Parts that those of Figures 1 and 2 correspond to the same reference numerals. With regard to the function of these parts, reference is made to the description of FIGS. 1 and 2 directed.

The oven 10 according to FIG. 3 shows a metal plate 16 to be dried with one on a surface 52 applied varnish layer 50. In contrast to the The embodiment according to FIGS. 1 and 2 is the one in FIG. 3 furnace 10, the lower magnetron 36 is another magnetron 36 arranged opposite each other. The lower magnetron 36 radiates constantly Microwaves 60 from. The upper magnetron 36 shown in FIG. 3 shines pulsed microwaves 62. This is done by a periodic, every 5 ms the magnetron 36 is switched on and off. In this way it is achieved that the microwaves 62 have a spectrum of wavelengths. This spectrum is calibrated to the properties of the Metal plate 16 set. To grasp what type of item it is acts on the metal plate 16, with the help of the serving as a transmitting antenna Anode 38 also reflects that from surface 52 of metal plate 16 Microwave radiation 64 detected and with the help of a magnetron connected Evaluation and control circuit 66 evaluated. This control circuit 66 compares the evaluated reflection 64 with one in a memory 68 stored set of objects acquired by prior calibration. The evaluation and control circuit 66 recognizes a correspondence between the Reflection 64 with a reflection pattern stored in the memory 68, see it adjusts the radiation power of the anode 38 and the on / off frequency of the Anode 38 accordingly.

In contrast, the lower magnetron 36 shown in FIG. 3 shines the microwave energy 60 decreases constantly without interruption.

If it is detected with the aid of the anode 38 and the control circuit 66, that no object in the effective range shown in dashed lines in FIG. 3 69 of the magnetrons 36, the on / off frequency of the Magnetrons 36 increased by control circuit 66 to 500 ms to power save. Once from the transmitter antenna 38 and the control circuit 66 again an object is detected in the area of effect 69, the on / off frequency again reduced to 5 ms. The effective area 69 is in 3 is shown only schematically, since in reality it is slightly arched, since the microwaves 60 and 62 easily enter the housing 20 diverge.

Cooling hoses 70 are provided for cooling the input area 22 of the housing 20 intended. Possible moisture caused by the Entrance 22 arrives, condense so that it does not on the paint 50th can deposit. Within the housing 20 is thus in particular in the Area of effect 69 reaches a humidity of 50 ° C.

The configuration of the cooling air duct 34 of the waveguide 40 and the Cooling air duct 34 with air grille 72 connecting waveguide 40 becomes such chosen that the waste heat of the magnetron 36 in the stationary Area of effect 69 causes an air temperature between 60 and 80 ° C, which a Temperature of the surface 52 of the metal plate 16 of about 45 to 50 ° C result Has. In this way it is achieved that the lacquer layer 50 through the Microwave radiation 60 or 62 is dried and not by heat or Infrared radiation is dried. Because the latter would either have to dry the surface 74 of the lacquer layer 50 before the lacquer layer 50 dries itself, which could disadvantageously develop bubbles, or too long a drying time, which is also thanks to the use of microwaves according to the invention can be avoided.

The arrangement of two magnetrons 36 shown in FIG. 3 can - as by the dots 76 indicated are continued in the figure 3 to the left. The magnetron pairs further to the left can do other things Show frequency spectra and other energy inputs. In particular can the other magnetron pairs controlled by higher or lower power the control circuit 66 a too low or too high power of the in FIG compensate the magnetron pair shown.

In addition, for example, magnetron pairs operating according to FIG 30 according to Figure 1 can be arranged one behind the other and different stationary Form effective areas 69 of microwaves 60, 62. The can Microwave radiation 62 from a fundamental frequency, for example about 2.5 Gigahertz, and a modulated modulation frequency are formed. The modulated frequency modulated increases from zone to zone, for example on. With five zones, for example, it has proven to be advantageous for drying Paint on plastic and metal substrates 16 proven if the Zones increasing from modulation frequencies of about 1.2 gigahertz, about 1.6 Gigahertz, about 1.9 gigahertz, about 2.1 gigahertz, about 2.5 gigahertz and about 3 Gigahertz can be modulated.

It has proven to be advantageous when drying lacquers on ceramics or wood proven if another zone enters, in which a modulation frequency of about 900 megahertz is used.

Furthermore, other magnetrons can be circular around the movement path of the substrate 16 are arranged around. This can happen that the magnetrons 30 themselves circle around the path of movement of the substrate 16 are arranged and concentric on the path of movement of the substrate 16 irradiate or are provided with waveguides, which according to FIG Radiate essentially concentrically on the path of movement of the substrate 16. With particularly effective for drying substrates 16 with complicated Geometry, for example with fine grooves or depressions, has proven when the concentrically radiating on the path of movement of the substrate 16 Microwave sources 36 are switched on and off in succession, so that a microwave field rotating around the path of movement of the substrate 16 results. The magnetrons 30 are controlled one after the other in this way turned off that the microwaves of the magnetron previously turned off 30 still slightly with the subsequently to be generated in the direction of rotation Microwave field of the subsequent magnetron 30 overlap, but not too mutual amplification of neighboring microwave fields.

Claims (46)

Method for treating a coating material (50) on a substrate (16, 52) and / or a substrate (16, 52), comprising the steps: the substrate (16, 52) or the substrate (16, 52) provided with the coating material (50) is provided, the substrate (16, 52) or the substrate (16, 52) provided with the coating material (50) is treated with the aid of microwaves (54, 60, 62) having at least two wavelengths. Method according to claim 1,
wherein the substrate (16, 52) or the substrate (16, 52) provided with the coating material (50) is passed through a stationary effective area (69) of the microwaves (54, 60, 62) during the treatment. Method according to claim 1,
an effective range (69) of the microwaves (54, 60, 62) for treating the coating material (50) and / or the substrate (16, 52) via the substrate (16, 52) or the substrate provided with the coating material (50) (16, 52) is led away. Method according to one of the preceding claims,
wherein the substrate (16, 52) or the substrate (16, 52) provided with the coating material (50) is irradiated simultaneously with the at least two wavelengths. Method according to one of the preceding claims,
wherein the at least two wavelengths of the microwaves (54, 60, 62) are generated by switching on a microwave source (36) generating the microwaves (54, 60, 62). Method according to claim 5,
the switching on is carried out repeatedly. Method according to claim 6,
switching on periodically. Method according to one of claims 5-7,
the microwave source (36) being switched off each time it is switched on. Method according to one of claims 5-8,
switching on every 5 ms. Method according to claim 2 and according to one of claims 5-9,
wherein the microwaves (54, 60, 62) are switched on approximately every 5 ms when the substrate (16, 52) or the substrate (16, 52) provided with the coating material (50) to be dried is in the stationary effective range (69) while the microwaves (54, 60, 62) are switched on approximately every 500 ms when the substrate (16, 52) or the substrate (16, 52) provided with the coating material (50) to be dried is outside the stationary effective range ( 69) of the microwaves (54, 60, 62). Method according to one of the preceding claims,
wherein the microwaves (54, 60, 62) are radiated from different angles onto the substrate (16, 52) or the substrate (16, 52) provided with the coating material (50) to be dried. Method according to the preceding claim,
the angle being changed continuously or in regular steps. Method according to the preceding claim,
wherein the angle is changed by successively switching on microwave sources (36) arranged at different angles to the substrate (16, 52) or the substrate (16, 52) provided with the coating material (50) to be dried or a path of movement thereof. Method according to the preceding claim,
the microwave sources (36, 30) being switched off again after the next microwave source (36) has been switched on, so that a microwave field rotating in a predetermined direction results. Method according to the preceding claim,
the time at which the next microwave source (36) lying in the predetermined direction of rotation behind the microwave source (36) to be switched off is switched on so that there is an overlap but no mutual amplification of the neighboring microwave fields. Method according to the preceding claim,
it is detected whether there is a substrate (50) or a substrate (16, 52) provided with coating material (50) to be dried in the stationary effective range (69) of the microwaves (54, 60, 62). Method according to one of the preceding claims,
the material from which the substrate (16, 52) or the substrate (16, 52) provided with the coating material (50) to be dried is essentially made. Method according to the preceding claim,
wherein the switching on and off of the microwaves (54, 60, 62) is controlled in dependence on the detected material. Method according to one of the preceding claims,
the amplitude of the microwaves (54, 60, 62) being controlled as a function of the material detected. Method according to one of the preceding claims,
wherein the substrate (16, 52) or the substrate (16, 52) provided with the coating material (50) to be dried is successively passed through zones (69) which are irradiated with microwaves (54, 60, 62) which have an identical one Fundamental frequency, preferably of about 2.5 gigahertz, and are modulated with different modulation frequencies, preferably with about 1.2 gigahertz, about 1.6 gigahertz, about 1.9 gigahertz, about 2.1 gigahertz, about 2.5 gigahertz and / or about 3 gigahertz. Method according to the preceding claim,
the modulation frequencies being selected as a function of the substrate (16, 52) or the substrate (16, 52) provided with the coating material (50) to be dried. Method according to the preceding claim,
wherein in the case of a substrate (16, 52) consisting essentially of wood and / or ceramic, at least about 900 megahertz is used as the modulation frequency. Method according to one of claims 16-22,
wherein the detection is carried out with the aid of the microwave source (36), preferably with an anode (38) serving as a transmitter antenna, in that the microwaves (54, 60, 62) retroreflected by the substrate (16, 52) from the microwave source (36), preferably detected by the anode (38) and evaluated with an evaluation circuit (66). Method according to one of the preceding claims,
wherein the substrate (16, 52) or the substrate (16, 52) provided with the coating material (50) is irradiated from two sides with microwaves (54, 60, 62). Method according to one of the preceding claims,
wherein one of the two sides of the substrate (16, 52) or the substrate (16, 52) provided with the coating material (50) is constantly irradiated with microwaves (54, 60, 62). Method according to one of the preceding claims,
the drying being carried out at a constant ambient temperature, preferably at a temperature between 10 ° and 120 ° C., more preferably at about 45 ° C. Method according to one of the preceding claims,
the drying being carried out at a constant atmospheric humidity, preferably at 30% to 70%, more preferably at about 45% atmospheric humidity. Method according to one of the preceding claims,
the drying is carried out with a constant air flow. Method according to claim 2 and according to one of the preceding claims,
wherein the space (22) through which the substrate (16, 52) or the substrate (16, 52) provided with the coating material (50) to be dried enters and / or exits in the stationary effective area (69) is cooled. Device for treating a coating material (50) on a substrate (16, 52) and / or a substrate (16, 52), comprising: a microwave source (36) for generating microwaves (54, 60, 62), an emitting means (38) for emitting the microwaves generated (54, 60, 62), characterized by control means (66) for controlling the microwave source (36) in such a way that the microwave source (36) emits microwaves (54, 60, 62) with at least two wavelengths. Device according to the preceding claim,
the control means (66) comprising an on / off device for switching the microwave source (36) on and off. Apparatus according to claim 30 or 31,
further showing: a stationary effective area (69) in which the microwaves (54, 60, 62) act on the substrate (16, 52), the substrate (16, 52) provided with the coating material (50) to be dried, at least two microwave sources (36) are provided in order to be able to irradiate the effective range (69) from two different directions with microwaves (54, 60, 62). Device according to the preceding claim,
wherein at least one of the at least two microwave sources (36) constantly emits microwaves (54, 60, 62). Device according to one of claims 30-33,
wherein the microwave source is arranged relative to the stationary operating range (69) in order to control the air temperature in the stationary operating range (69) between 10 ° C and 120 ° C, preferably between 60 ° C and 80 ° C, more preferably around 45 ° C, keep. Device according to one of claims 30-34,
wherein at least three microwave sources (36) are arranged around the stationary effective area (69) such that they radiate the microwaves (54, 60, 62) essentially concentrically onto the stationary effective area (69). Device according to one of claims 30-35,
further showing: at least one further stationary effective range (69) in which the microwaves (54, 60, 62) act on the substrate (16, 52) or the substrate (16, 52) provided with the coating material (50) to be dried, the at least one a further stationary effective area (69) is arranged behind the first stationary effective area (69) in a direction of movement of the substrate (16, 52) or of the substrate (16, 52) provided with the coating material (50) to be dried. Device according to the preceding claim,
wherein in at least two of the effective areas (69) the microwaves (54, 60, 62) have different frequencies, preferably in one direction of movement of the substrate (16, 52) or of the substrate (16, 52) provided with the coating material (50) to be dried have microwaves with increasing modulation frequency at the same fundamental frequency. Device according to one of claims 30-37,
wherein the microwave source (36) has an anode which is designed to serve as an sensor for an evaluation circuit (66) for the microwave energy retroreflected by the substrate (16, 52),
wherein the evaluation circuit (66) is designed to evaluate the detected retroreflected microwave energy in such a way that when the detected retroreflected microwave energy rises, the microwave energy emitted by the microwave source (36) decreases, while when the retroreflected microwave energy decreases, that by the microwave source (36 ) emitted microwave energy is increased. Device according to one of claims 30-38,
wherein coolants (70) are provided in front of and / or behind the stationary effective area (69) in order to keep the air humidity in the stationary effective area (69) between 30% and about 60%, preferably to about 45%, of air humidity. Device according to the preceding claim,
wherein the coolants comprise cooling hoses (70) which are essentially concentric around a movement path of the substrate (16, 52) or of the substrate (16, 52) provided with the coating material (50) to be dried to and / or from the stationary effective area (69 ) are arranged around. Device according to one of claims 30-40,
ventilation means (30) being provided to produce a substantially constant air flow within the stationary effective area (69). Use of a microwave oven (10) for the treatment of a Coating material (50) on a substrate and / or the or a substrate (16, 52). Use according to claim 42,
the microwave oven being a continuous microwave oven (10). Use according to claim 43,
the continuous microwave oven (10) being provided with: a housing (20) with an inlet (22) and an outlet (24), a conveyor belt (14) extending through the housing (20) for transporting the substrate (16) provided with the coating material (50) into, through and out of the housing (20) and at least one microwave device (28) which has a microwave generator (36) which can be cooled by means of cooling air and has a transmitter antenna (38) which is arranged in a waveguide (40) which transmits microwaves (54, 60, 62) from the transmitter antenna (38) conducts and in the area of the conveyor belt (14) has a radiation opening (46) for radiating the microwaves (54, 60, 62), the cooling air cooling the microwave generator (36) via at least one opening (48) formed in the waveguide (40) in the waveguide (40) can be introduced and can be blown out of its radiation opening (46). Use according to claim 44,
wherein a cooling air generating device (30) is provided with a ventilation duct (34) in which the microwave generator (36) with its transmitter antenna (38) is arranged protruding into the waveguide (40), and that the ventilation duct (34) and the waveguide (40 ) viewed in the flow direction of the cooling air and in the direction of propagation of the microwaves (54, 60, 62) behind the microwave generator (36) or behind the transmitter antenna (38) via which at least one opening (48) is connected. Use according to claim 45,
wherein the waveguide (40) extends in a straight line in the region of the connection to the ventilation duct (34), the ventilation duct (34) in this region extending obliquely (50) to the waveguide (40).

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