EP1144129B1 - Coating and drying of articles with infrared radiation - Google Patents

Description

The invention relates to a method for drying coated and / or impregnated objects, in particular of painted wood, one on the surface of each Object applied coating and / or impregnating agent a solution to be expelled during drying and / or Contains diluent, especially water, and wherein the solvent or diluent has the property in undried state to penetrate into the object, so that uniformly structured areas, in particular fibers of the Subject, change their position in the subject and after a characteristic period of time since the application of the Impregnating or coating agent the surface structure change such that a post-treatment of the surface (Grinding, coating or impregnation) required or is desirable. The invention further relates to a method for drying a coated and / or impregnated Object, especially of lacquered wood, one on the surface of the respective object applied coating and / or impregnating agent has a component, especially color pigments, which has the property by its presence in the surface and / or in the quality of the coating or impregnation to ensure, however, the property continues has to penetrate the object in an undried state and after a characteristic period of time since the application of the impregnating or coating agent no longer in sufficient quantity in the area of the surface and / or in the Coating to be present, so that an aftertreatment of the Surface, in particular a repainting, required or is desirable. Finally, the invention relates to the Use of an agent for drying coated and / or impregnated objects.

The problem occurs when using water-based paints on that in the area of an initially smooth wooden surface determined by water penetration, each uniform Set up structured areas or fibers of the wood because the water penetrates into the wood and swells the uniformly structured areas and / or intermediate areas leads between the fibers. After the paint has dried or the drying of the paint and the wooden object therefore usually the painted surface is sanded and painted again. The layer of lacquer applied first acts thereby as a water barrier, since it prevents water from entering the wood prevents.

The same or at least similar effects occur in others absorbent materials, each of which is uniform have structured areas and / or fibers. Also the effects occur not only with water-based paint, but entirely generally for water-dilutable or water-based coating and / or impregnating agents, such as, for example Glazes, stains, flame retardant coatings and / or other protective and impregnating agents applied to the surface of the object to be treated. Farther the effects do not only occur with water-containing coating and / or impregnating agents, but also in such Means, the other to be driven out during drying and / or contain solvents and / or diluents to be bound.

One observes when using pigmented lacquers continue on wood or similar absorbent objects that after a characteristic period of time, the pigments knock away, which includes the penetration of the pigments inside of the object understands. The pigments that - to their optical To develop effect - in the area of the surface of the Object and / or in the applied layer should therefore undesirably penetrate the object. This leads to the coating and / or impregnation does not have the required or desired quality. Also here is a post-treatment of the surface, especially one Repainting, necessary or at least desirable.

Knocking away not only with pigments, but also with other, for the quality of the coating or impregnation essential components of coating and / or impregnating agents occur when these hit the surface of a absorbent or permitting penetration applied become.

Drying the coated and / or impregnated items can be caused passively by waiting until the wet component changes due to a concentration gradient about the surroundings of the object and / or about the Environment and has distributed the object. Especially in industrial Production lines, however, find active drying instead of the items to be dried, for example go through an oven or are irradiated with infrared radiation become. It is also known, especially water-based Coating and / or impregnating agent by UV radiation cure. The solvent can, in this case Water, through the hardening firmly in the coating and / or Impregnation agents are included. Including too the moist component so that they no longer leave the agent can, is understood by "drying".

Water is known to be a solvent and / or diluent to be preferred because it is environmentally friendly. Especially drying can then work with open systems the expelled water, possibly after passing one Filters, released into the environment.

DE-A-2029557 describes a method for drying coated plates known in which the drying by irradiation of the surfaces of the Plate with infrared radiation follows. This should make it possible to be coated and hardened plates immediately after exiting the corresponding Stacking device or further processing. With the corresponding Irradiation after a trowel coating is said to cause signs of decay be avoided.

The present invention has for its object a method of type mentioned at the beginning for drying coated and / or impregnated To specify objects, by the use of which a post-treatment of the coated and / or impregnated surface is unnecessary. Another The object of the invention is to use an agent for drying of coated and / or impregnated objects that it makes it possible to dispense with post-treatment after drying.

The object is achieved by a method having the features of claim 1 and / or solved by a method with the features of claim 2. The Use according to the invention is the subject of claim 10. Further developments are the subject of the respective dependent claims.

On the process side, drying is carried out before the characteristic time period expires causes, with the expiry of the position of the fibers or the respective uniform structured areas would change so that post-treatment the surface is necessary or desirable, or with their Process of the essential for the quality of the coating or impregnation Part would knock away, so that an aftertreatment is required or is desirable.

The infrared radiation preferably has essential drying effects Radiation components in the near infrared, especially at wavelengths less than 1.0 / jm. The wavelength range is called "near infrared" understood between the visible range and 1.4 / jm. advantageously, is the amount of energy of thermal radiation in the near infrared of objects that are at room temperature. electromagnetic Radiation in the near infrared and temperature radiation from in the in most cases inevitably existing objects at room temperature can therefore easily be separated from each other. The controllability of close Infrared radiation is therefore particularly good.

Furthermore, water in particular absorbs near infrared radiation with a high degree of absorption, so that targeted water molecules in the not yet dried coating or impregnation and can be knocked out. This has the advantage that the rest of the coating or impregnation and in particular the object on the surface of which this has been applied is not significantly or not at all heated. On a subsequent cooling or waiting time can therefore be dispensed with. Further processing or storage, e.g. B. stacking of items can continue without interruption to the drying process consequences.

In a training, the infrared radiation is in front of it Impingement on the surface adjusted and / or filtered that spectral radiation that is an undesirable Heating the coating or impregnation and / or of the object would be missing. For filtering can those known from the prior art or the expert common optical filters, especially transparent filters, be used. Also with other solvents or thinners as water can be a targeted stimulation respectively.

In a further development, the infrared radiation has a spectral one Radiation flux density maximum in the near infrared, especially at wavelengths less than 1.0 µm. preferably is the infrared radiation as a temperature radiation Radiation emitter emitted at temperatures of 2500 K. or higher, in particular from 2900 K or higher. This approach has several advantages. On the one hand, finds because of the large temperature differences between the radiation emitters and which is usually at room temperature or at least approximately at room temperature rapid cooling of the radiation emitter takes place when the Heating is switched off. Second is the one emitted Radiance, d. i.e., the radiated per emitter surface Radiant power, greater at high temperatures than at lower temperatures. Accordingly, the volume of the radiation emitter can be chosen accordingly small, so that its overall heat capacity is low. Hence is a Radiation emitter excellent at the high temperatures mentioned controllable. Preferably, the heater takes place in a known Way in an electrical way instead of an electrical one Current through the trained as electrical resistance Radiation emitter flows. Electric currents are well known Way controllable at low cost.

Especially with wood that is coated with water-based paint, it has been found that erecting wood fibers typically after 5 seconds. Contains the water-based paint Pigments is a negative influence on the quality of the paint Knocking off typically after 3 seconds observable. The drying is therefore preferably within of 5 seconds, especially within 3 seconds since Applying the impregnating or coating agent.

In the industrial coating or impregnation of Objects are usually continuously in one Funding direction funded. According to the invention respective object preferably an order zone in which the Coating and / or impregnating agent is applied, and the object or its coated or impregnated Longitudinal sections conveyed into a drying zone, in which the coated or impregnated surface with infrared radiation is irradiated. Applying the coating and / or Impregnation agent can be all around or only on parts the surface of the object. Accordingly preferably the infrared radiation at about evenly above the coated or impregnated surface is more distributed Radiant energy simultaneously coated on the entire or impregnated surface of a longitudinal section of the object irradiated. Preferably a plurality of Radiation sources used and / or is the radiation through Scattering and / or reflection deflected accordingly.

To dry as early as possible after application To be able to end, an embodiment is preferred in which the object or its longitudinal sections immediately after Leaving the order zone or already after partially passing through in the application zone enter the drying zone. Known are already devices for applying liquid or pasty coating and / or impregnating agents which the agent in the application zone through a gas flow is transported, which is located in a storage room Entrains the agent and deposits on the surface of the object. For example, the coating systems of the "VACUMAT" series from Schiele Maschinenbau GmbH, Kapellenstr. 7, D-56651 Niederzissen based on this principle. With further training the invention is preferably the gas flow before Reaching the storage room for cooling one or more Radiation sources of infrared radiation and / or for cooling others involved in the radiation in the drying zone Components such as reflectors, radiation filters and / or radiation transparent Room divider used. For coating agents and / or impregnating agents which are expedient be heated to positively influence the viscosity, acts on the gas absorbed during the cooling process Heat particularly advantageous. It leads alone or together with additional heating to the desired heating of the Coating and / or impregnating agent.

The invention for use as a drying agent proposed means is an infrared lamp for drying one with a coating and / or impregnating agent coated or impregnated object. Preferably the infrared lamp is a halogen lamp.

In one development, the infrared lamp is a tube emitter with a line-like in a radiolucent Tube, especially in a quartz glass tube, extending filament formed.

In another development, the infrared lamp with a Combined reflector body that extends along the tube and this in cross-section like a gutter on the back surrounds that emitted towards the front Infrared radiation is amplified by reflected radiation.

Fig. 1

ein zweiseitig beschichtetes Profilstück, bei dem ein Wegschlagen von Pigmenten vor Beendigung der Trocknung stattfindet,

Fig. 2

eine frischlackierte Holzoberfläche,

Fig. 3

die Holzoberfläche nach Fig. 2, bei der ein Aufstellen von Holzfasern stattgefunden hat,

Fig. 4

eine Vorrichtung zum Beschichten und Trocknen von Gegenständen.

The invention will now be explained in more detail on the basis of exemplary embodiments. Reference is made to the attached drawing. However, the invention is not restricted to these exemplary embodiments. The individual figures of the drawing show:

Fig. 1

a profile piece coated on two sides, in which pigments knock away before drying has ended,

Fig. 2

a freshly painted wooden surface,

Fig. 3

2, in which a placement of wood fibers has taken place,

Fig. 4

a device for coating and drying objects.

Fig. 1 shows a profile piece 1 made of medium-density fiber material (MDF). MDF profile 1 is fresh with a layer of water-based paint 2 coated. The water-based paint layer 2 is, however on MDF profile 1 for so long that knocking away of Color pigments 6 has taken place in the water-based paint layer 2 were included. The direction is indicated by three arrows in the indicated on the left half of the picture. The representation shown in Fig. 1 corresponds to a time of approx. 3 seconds since Start of the application process in which the water lacquer layer 2 has been applied.

According to the invention, the achievement of that shown in FIG. 1 is achieved Condition prevents drying within 3 Seconds, especially within a second since The beginning of the order process is effected.

2 shows a coated surface of a wooden profile 5 in partial representation in cross section. The coating consists of a water lacquer layer 2. The wood profile 5 has fibers 4, that end on the surface of the wooden profile 5. The surface was sanded before coating and is accordingly smooth.

Fig. 3 shows the wooden profile 5 of FIG. 2 for a later Point in time since the drying of the water-based paint layer 2 or Water-based paint layer 2 and the wooden profile 5 not in time has been effected since that shown in Fig. 2 State water in the fibers 4 and in spaces 3 between penetrated the fibers 4 so that the fibers 4 set up and both the surface that supports the water-based paint layer of the wooden profile 5 and the outer surface of the water-based paint layer 2 has become rough or uneven. Especially from Customers of industrially manufactured products will be one of them Surface structure not accepted. It is therefore an after-treatment required, usually grinding the dried Paint outer surface and subsequent painting.

To the state of the wooden profile 5 shown in Fig. 2, the any time less than 5 seconds since Corresponds to the start of the application process for water-based paint layer 2, To obtain permanent drying according to the invention 5 seconds, especially within 1 Second since the job started.

Fig. 4 shows a device for painting wooden yardware in cross section. The wooden yard goods is in the representation of Fig. 4 from left to right by those skilled in the art Funded by funding agencies. Here are high working speeds, d. i.e., conveyor speeds, desirable, especially conveyor speeds of 8-80 m / min or even, using special feed units, conveyor speeds up to 240 m / min. Such special aggregates will be for example driven by two synchronously controlled motors and have a relatively small space requirement.

The wood yard goods shown in Fig. 4 is a concrete one Wood profile 5, as it is in sections in Fig. 2 has been shown. The wooden profile has a length of about 2 m and is conveyed at a conveying speed of 1 m / s or Conveyed 60 m / min. It initially runs from the left coming an application chamber 20, whose dimensions in An order zone is defined in the conveying or longitudinal direction. Immediately, without any distance from the application chamber 20, closes the drying zone of the device through the Longitudinal section of the conveyor path is defined, the one Infrared radiation can be exposed. For this purpose, the device two halogen lamps 11, which are perpendicular to the image plane 4 extend. The halogen lamps 11 are as Tube radiator trained. They have a quartz glass tube 13 and one approximately in the center line of the respective quartz glass tube arranged tungsten wire 12. The tungsten wire 12 serves as a radiation emitter. During the radiation period the tungsten wire 12 has electrical current flowing through it and has accordingly a temperature of about 3200 K.

The radiation emitted by the halogen lamps 11 spreads either directly in the direction of the piece of wood to be dried off, or indirectly. The indirect spread can be spread over several different ways.

The halogen lamps 11 have a lamp reflector body 10 combined, the two gutter-like, along the quartz glass tubes 13 has extending recesses in cross section are partially filled by the halogen lamps 11. The Surface on the underside of the lamp reflector body 10, including the surface of the channel-like recesses is reflective of infrared radiation. For example, there is the lamp reflector body 10 made of aluminum and is the reflective surface of the lamp reflector body 10, called the top reflector surface 14 of the device Polishing aluminum formed.

To ensure effective infrared radiation, is on a side reflector body on the right side of the drying zone 16 arranged, the inner, facing the drying zone Surface, a side reflector surface 15, which is for Infrared radiation is designed to be reflective. Farther there is a lower one at the bottom of the drying zone Reflector body 19 with the drying zone pointing inwards lower 17 and side 15 reflector surfaces. Finally is also the outer surface of the part facing the drying zone the surface of the application chamber 20 as a side Reflector surface 15 formed. Because of the sectional view 4 further reflector surfaces not shown below and above the image plane of FIG. 4 complete the Edging of the drying zone so that an almost closed, the drying zone enclosing space is formed in which the infrared radiation is almost homogeneous due to reflections distributed and so all sides of the through the drying zone promoted wood profile 5 with approximately the same radiation flux density be irradiated.

There are openings in the edge of the drying zone, where the wood yard goods enter the drying zone from the left, where the wooden yardage leaves the drying zone on the right and above to the side, right and left of the lamp reflector body 10. The last-mentioned openings serve that air at the Blown along the bottom of the lamp reflector body 10 can be to the halogen lamps 11 and the lamp reflector body 10 to cool. Cooling minimizes unwanted difficult to control temperature radiation of the Tungsten wires 12 device components involved in the radiation. These are in particular the quartz glass tubes 13, the Lamp reflector body 10, the side reflector body 16, the another side reflector body, not shown, the lower reflector body 19 and a glass sheet 18, the Drying zone divided into a lower and upper section. Cooling takes place separately in both the upper and also take place in the lower section.

Like the cooling in the upper section, this takes place Cooling in the lower section by forced convection from Air. The forced convection is shown by a not shown Pump driven, the air in suction from the right coming through the outlet opening provided for the wooden yard goods from the drying zone in the lower part of the Drying zone can enter. There the airflow divides first on to the glass pane 18 on its underside and the Cool the reflector surfaces in the lower section. Subsequently the air flows through the right opening of the application chamber 20 into this, swirls the liquid there Paint on, so that a uniform paint mist forms, which is reflected in the wooden profile 5. On the right The air flows through the opening of the application chamber 20 close to the coated surface of the wooden profile 5. The passage opening is dimensioned accordingly, that around the wooden profile 5 only a few Millimeter space to the edge of the passage opening are. At the left passage opening of the application chamber 20, through which the wooden profile 5 into the application chamber 20th is conveyed in, air also enters the application chamber 20 a, the space between the Wood profile 5 and the edge of the passage opening is lower, to ensure that the majority of those in the Application chamber incoming air through the right Flow opening flows. Through an outlet opening 21 Application chamber 20, the paint mist leaves the application chamber 20. By device components, not shown the paint components of the paint mist are separated, cleaned and from the supply of paint 23 back out of stock liquid paint 22 supplied in the application chamber 20.

Since the throughput time of each individual longitudinal section of the Wood profile 5 through the drying zone about a second and since the drying when leaving the drying zone is carried out on the painted surface of the wooden profile 5 does not knock away color pigments and has that water contained in the liquid paint and / or others Solvents or thinners no time, so in the wooden profile 5 to penetrate that putting up its fibers takes place. To ensure complete drying, emit the halogen lamps 11 with a correspondingly sufficient Radiation power. Depending on the one to be dried Surface per longitudinal section of the wooden yard goods and dependent the radiant power depends on the conveying speed set accordingly. The maximum radiation power is sufficient not, additional halogen lamps (not shown) switched on.

The glass pane 18, which divides the drying zone, enables one of the respective cooling load in the upper section and in Adjusted air cooling in the lower section. On the other hand decoupling the air flow required for painting in the application chamber 20 from the temperature or from the cooling requirements of the halogen lamps 11 and the lamp reflector body 10. In alternative embodiments it may be desirable to pass through the right opening air flowing into the application chamber 20 to higher Warm temperatures (for example, for heating the paint). In this case, alternatively or additionally Air flow along the halogen lamps into the application chamber instead of.

LIST OF REFERENCE NUMBERS

1

MDF Profile

2

Water-based paint layer

3

gap

4

fiber

5

wood profile

6

color pigment

10

Lamp reflector body

11

halogen lamp

12

tungsten wire

13

quartz glass tube

14

upper reflector surface

15

side reflector surface

16

Side reflector body

17

lower reflector surface

18

pane

19

lower reflector body

20

application chamber

21

outlet opening

22

liquid paint

23

paint supply

Claims (14)

1. Method of drying coated and/or impregnated objects (1; 5) that comprise a plurality of regions, in particular fibres, that are each uniformly structured, in particular for drying lacquered wood, in cases such that a coating agent and/or impregnation agent (22) applied to the surface of the object (1; 5) contains a solvent and/or dilution fluid, in particular water, that is to be driven out and/or bound during drying, and such that the solvent or dilution fluid has the property of penetrating into the object in the undried state with the result that the uniformly structured regions (4) change their position in the object (1; 5) and, after a characteristic period of time following application of the impregnation or coating agent (22), alter the surface structure in such a way as to make secondary treatment of the surface necessary or desirable,
   wherein the drying is completed before the characteristic period of time has elapsed, by irradiating the coated or impregnated surface with infrared radiation.
2. Method of drying coated and/or impregnated objects (1; 5), in particular lacquered wood, in cases such that a coating agent and/or impregnation agent (22) applied to the surface of the object (1; 5) includes a component (6), in particular colouring pigments, with the properties that

   its presence in the region of the surface and/or in the coating (2) ensures the quality of the coating (2) or impregnation, however

   in the undried condition it penetrates into the object (1; 5) and after a characteristic period of time following application of the impregnation or coating agent (22) it is no longer present in sufficient quantity in the region of the surface and/or in the coating (2), so that a secondary treatment of the surface, in particular a secondary lacquering, is necessary or desirable,

   wherein the drying is completed before the characteristic period of time has elapsed, by irradiating the coated or impregnated surface with infrared radiation.
3. Method according to Claim 1 or 2,
   characterized in that the infrared radiation comprises substantial components, which bring about the drying, in the near infrared, in particular at wavelengths below 1.0 µm.
4. Method according to Claim 3,
   characterized in that the infrared radiation has a spectral radiation flux density maximum in the near infrared, in particular at a wavelength below 1.0 µm.
5. Method according to Claim 4,
   characterized in that the infrared radiation is emitted as thermal radiation from a radiation emitter (12) that is heated to temperatures of 2500 K or higher, in particular 2900 K or higher.
6. Method according to one of the claims 1-5,
   characterized in that the drying is completed within 5 seconds, in particular within 3 seconds, after the application of the impregnation or coating agent.
7. Method according to one of the claims 1-6,
   characterized in that the object (1; 5) being processed is conveyed continually in a longitudinal direction, in the course of which it first passes through an application zone in which the coating and/or impregnation agent (22) is applied, and that the object (1; 5) or more specificially its coated or impregnated longitudinal sections are conveyed into a drying zone in which the coated or impregnated surface is irradiated with the infrared radiation.
8. Method according to Claim 7,
   characterized in that the object (1; 5) or more specificially its coated or impregnated longitudinal sections enter the drying zone immediately after leaving the application zone or after having partially passed through the application zone.
9. Method according to Claim 8, wherein the application of the impregnation or coating agent (22) in the application zone is brought about by a stream of gas that carries along the impregnation or coating agent (22), which is contained in a reservoir, and deposits it on the surface of the object (1; 5),
   characterized in that before the stream of gas reaches the reservoir, it is used to cool an infrared-radiation source (11) and/or to cool other components (16, 18, 19) involved in the irradiation in the drying zone, such as reflectors, radiation filters and/or partitions transparent to radiation.
10. Use of an infrared lamp (11) to dry an object (1; 5) coated or impregnated with a coating agent and/or impregnation agent (22), in particular to dry lacquered wood, in cases such that the nature of the coating agent and/or impregnation agent (22) is as described in Claim 1 and/or in Claim 2.
11. Use according to Claim 10, wherein the infrared lamp (11) is a halogen lamp.
12. Use according to Claim 10 or 11,
    wherein the infrared lamp (11) is constructed as a tubular radiator with an incandescent filament (12) that extends linearly within a tube (13) that is transparent to radiation, in particular within a quartz-glass tube.
13. Use according to Claim 12,
    wherein the infrared lamp (11) is combined with a reflector element (10) that extends along the tube (13) and in cross section has a groove-like structure, enclosing back side of the tube in such a way that the infrared radiation is intensified by addition of reflected radiation to the radiation emitted towards the front side.
14. Apparatus for coating and/or impregnating objects, in particular wooden objects, comprising

    an application chamber (20) for continuously applying an impregnation or coating agent,

    a transport mechanism for continuously transporting the objects from the application chamber (20) to an irradiation device (10-19) for drying the impregnation or coating agent,

    wherein the transport mechanism is so constructed that its speed is adjustable in such a way that the object can be conveyed from the application chamber (20) into the irradiation device (10-19) and thereby dried within less than 5 seconds.

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