WO1999031449A1

WO1999031449A1 - Lacquer processing device and method

Info

Publication number: WO1999031449A1
Application number: PCT/EP1998/008240
Authority: WO
Inventors: Keld Gabelgaard; Heinz Jonas; Artur Kunder
Original assignee: Keld Gabelgaard; Heinz Jonas; Artur Kunder
Priority date: 1997-12-17
Filing date: 1998-12-16
Publication date: 1999-06-24
Also published as: EP1040308A1; EP1040308B1; DE59809597D1; DE19756194A1; ATE249609T1; DE19756194B4

Abstract

The invention relates to a method and device for processing, especially drying, lacquers in a working area (10). The inventive method comprises the following steps: (a) preparing a closed working area (10) which is filled with air; (b) drying the air in the working area (10); and (c) depositing the lacquer on the surface which is to be lacquered. The inventive device comprises the corresponding structural configurations for carrying out the method.

Description

Paint processing device and method

The present invention relates to a method and an apparatus for processing paints in a work area. In particular, the present device relates to a method and a device for drying water-soluble paints applied by means of spray guns in a work area.

Methods and devices for processing and in particular drying lacquers are known in the prior art. Traditionally, paints are first applied and then dried, especially in large series production in the automotive industry, in separate areas. The application is traditionally done either by means of an immersion bath or with spray guns (spray robots). In a subsequent step, the painted parts are then dried in separately provided drying chambers using hot air at temperatures of approx. 80 ° C. This drying step results in considerable energy costs, which make up a large proportion of the overall cost of the painting.

Solvent-based paints are traditionally used in the paint processing industry because they are easy and inexpensive to process. However, these solvent-based paints lead to considerable environmental pollution, since the solvent escapes into the atmosphere during the drying process. Although it would be technically possible to filter out the solvents using suitable filters, this leads to an undesired increase in the painting costs, since such filters are technically complex.

For ecological reasons, the use of water-soluble paints has therefore already been proposed, which from an ecological point of view solvent-based paints are preferable. However, compared to solvent-based paints, water-soluble paints are currently not particularly attractive for economic reasons, since the drying times in the traditional hot air booths are too long, which again increases the costs. For these reasons, the ecologically preferred water-based paints have so far been insufficiently adopted by the industry.

The present invention therefore has the problem of providing a method and a device with which the energy costs incurred in the coating processing can be considerably reduced in comparison to previously known methods, the quality of the coating being improved at the same time.

This problem is solved by a method for processing paints in a work area according to claim 1, and by a corresponding device according to claim 14.

More specifically, the above problem is solved by a method and a device according to which the air in a closed work area (the painting booth) is continuously dried. The consequence of this is that the air humidity in the work area is below that of the ambient air, as a result of which the water is removed from the paint to be applied even during the spraying process. This leads to a significant reduction in the drying time, which makes it possible to dispense with drying with hot air entirely.

Another advantage of the method according to the invention and the corresponding device is that particularly homogeneous layers of paint can be produced, since the continuous drying of the air in the work area not only leads to water removal in the paint, but in particular also dries the surface to be painted, ie makes water free. This leads to an increase in the homogeneity of the lacquer layer during the spraying process, since the Arrange color pigments on the surface to be painted the more homogeneous the drier it is.

According to a particularly preferred embodiment of the present invention, the air in the work area is dried by means of an adsorption rotary dehumidifier which has an adsorption line connected to the work area and a separate regeneration circuit. The particular advantage of this drying system is that it works continuously and requires very little maintenance.

According to a further preferred embodiment, the device according to the invention has, in addition to the drying system, a circulating and / or pre-cooling arrangement which circulates and cools the air in the work area. The cooling of the air initially leads to an increase in the relative air humidity, but to a decrease in the dew point of the air. This allows a particularly effective, subsequent drying of the air to the desired relative humidity.

Further preferred embodiments of the present invention result from the attached patent claims and the description of the currently preferred embodiment. The presently preferred embodiment is explained in the following with reference to the drawing, in which:

Fig. 1 shows schematically a paint processing device according to the present invention;

2 shows the currently preferred adsorption rotary dryer which is preferably used in the drying system according to the present invention; and

Fig. 3 is a Vernon curve in which the water-related corrosion rate is shown for steel.

In Figure 1, an inventive device for processing and in particular for drying paints is shown schematically.

The device according to the invention comprises a working area 10, which can preferably have the shape of a painting booth known per se. Within the work area 10, in addition to the objects to be painted (for example motor vehicle body parts), there are also the usual spraying devices (spray guns) used in the painting industry or in small paint shops, with which the paint is applied to the parts to be painted. Since these parts are sufficiently known to the person skilled in the art, a separate illustration is dispensed with.

It is of particular importance for the present invention that the work area 10 is isolated from the surroundings in order to largely prevent air exchange between the air 5 in the work area 10 and the ambient air.

Furthermore, the drying system 20, 30 according to the invention, shown schematically, can be seen in FIG. In the embodiment shown in FIG. 1, it comprises an adsorption dryer 20, and a circulating and pre-cooling arrangement 30, which are described below.

According to the present invention, in the preferred embodiment of the drying system according to the invention, an adsorption dryer 20 is used, which is connected to the working area 10 via an adsorption line 21. The adsorption dryer 20 uses a continuously operating adsorption rotor 20 '(see FIG. 2), which sucks in fresh air, dries it and introduces it into the work area 10 via the adsorption line 21. The adsorption dryer 20 also has a separate regeneration circuit 29, which - as described in more detail below - regenerates the adsorption rotor 20 '.

The adsorption dryer 20 according to the invention is described below with reference to FIG. 2. Essentially, the adsorption dryer 20 consists of an adsorption rotor 20 'which is provided with axially directed air channels (not shown). These ensure a laminar flow of air through the dryer with a low pressure drop. The air to be dehumidified is drawn in by an adsorption fan 24 through the adsorption rotor 20 'via a pre-filter 22. For the regeneration of the adsorption rotor 20 '(i.e. for its dehumidification), a separately provided regeneration area is provided which removes the moisture accumulated in the rotor and releases it to the outside. The air passed through the regeneration circuit 29 is drawn in through the regeneration section by a regeneration fan 30, having previously been cleaned by a filter 26 and subsequently raised to the necessary process temperature by a heater 28.

The adsorption rotor 20 'essentially consists of a slowly rotating rotor made of a ceramic composite material which is permanently impregnated with either silica gel or lithium chloride. Silica gel is currently preferred as the adsorbent because it is physiologically harmless and insoluble in water, and as a result can neither be washed out nor discharged with the air stream. The described arrangement of adsorption and regeneration areas results in a continuous operation of the adsorption dryer, since the adsorption process runs parallel to the regeneration process.

Furthermore, in the currently preferred embodiment, a circulation and pre-cooling arrangement 30 is provided, which has a circulation and pre-cooling circuit

32 is connected to the work area 10. The circulation and Pre-cooling arrangement 30 provides for an air exchange in the work area 10, and optionally for a pre-cooling. In addition, the circulation and pre-cooling arrangement 30 can also have filter elements (not shown) that filter the air in the work area 10.

Since the mode of operation of air circulation and cooling systems is well known to the person skilled in the art, a detailed description of them is omitted here.

The method according to the invention for processing and in particular for drying paints and the corresponding device have significant advantages over the known methods used hitherto, since on the one hand they make the subsequent drying of water-soluble paints with hot air unnecessary and on the other hand to a more homogeneous paint layer on the paint surface. As already mentioned before, the paint pigments arrange themselves more homogeneously on the surface to be painted, the drier the surface to be painted is. At painting temperatures of approx. 20 ° C, the dew point of the surrounding air must be at least 15 ° C in order to achieve an effective anchoring of the picments on the surface. If it is intended to paint steel, for example, it must be taken into account that the dry bulb temperature of the steel surface is always lower than that of the ambient air adjacent to it. This inevitably creates a cooling effect, which leads to aerosol deposition on the steel surface, even if the resulting water film is not visible to the naked eye.

This is illustrated by the Vernon curve shown in FIG. 3, which represents the corrosion curve of steel as a function of the relative air humidity (the ordinate shows the increase in weight as a measure of the susceptibility to corrosion). As you can see from the diagram, a relative increases Humidity of more than 60% increases the corrosion curve steeply, while rust formation no longer occurs if the humidity is below 30%. This means that no aerosol film has deposited on the steel.

Accordingly, if the coating is carried out at a relative humidity of less than 60%, or better still less than 30%, this enables a very homogeneous arrangement of the color pigments on the steel.

An example of the present invention will be explained below. A painting booth 10 is used which, according to the invention, is circulated with 20,000 m ³ / h or 25,000 m ³ / h air. The dried fresh air portion supplied via the adsorption dryer 20 should be approximately 10%.

Accordingly, 2,000 m ³ / h or 2,500 m ³ / h fresh air are passed through an adsorption dehumidifier (for example, available from ARKU-Verfahrenstechnik GmbH, Olehing, Germany) and brought to a low dew point. At the same time, the recirculation and pre-cooling arrangement 30 provides for pre-cooling of the air in the work area 10. If, for example, one looks at predictable conditions in summer, the following results:

example

Where T is the temperature, RH is the relative humidity, W is the water load, and TP is the dew point.

If one compares the energy balance for the drying of the classic methods (with hot air drying) compared to the above method according to the invention, it results that approximately 50% of the energy costs can be saved with the above parameters. It should be noted that the less total air volume is circulated, the more effectively the drying process can be designed (ratio of the water-containing circulating air to the highly dry fresh air portion). Therefore, the increase in the highly dry fresh air portion should lead to a further reduction in the necessary energy costs.

Finally, it is pointed out that the preferred embodiment described above is only to be understood as an example; other designs are possible without leaving the inventive idea. For example, in the embodiment according to FIG. 1, the adsorption dryer, circulating and pre-cooling arrangements according to the invention are arranged outside the working area 10. It is clear to the person skilled in the art that these can of course also be arranged within the work area.

Furthermore, in the preferred embodiment, the adsorption dryer is provided as a separate element (separate from the circulating and pre-cooling arrangement). Of course, an integrated device can also be provided.

Finally, it is pointed out that the method and the corresponding device can be used not only for water-based paints, but also for solvent-based paints. If the method according to the invention and the corresponding device are used for solvent-based paints, this leads to the fact that drying by hot air, which is still necessary, can be considerably reduced; in this case it will Process according to the invention used as a predrying process.

Claims

claims

1. A method for processing, in particular drying, lacquers in a work area (10), which comprises the steps:

a. Provision of an air-filled, closed work area (10);

b. Drying the air in the work area (10); and

c. Applying the paint to a surface to be painted.

2. The method of claim 1, wherein the relative humidity in the drying step is reduced to below 25%.

3. The method of claim 1, wherein the relative humidity in the drying step is reduced to below 10%.

4. The method of claim 1, in which the relative humidity in the drying step is reduced to about 6%.

5. The method according to any one of claims 1 to 4, which additionally comprises the step of pre-cooling the air before the step of drying the air in the work area (10).

6. The method of claim 5, in which the air is cooled to below 20 degrees Celsius in the pre-cooling step.

7. The method of claim 5, wherein the air in the pre-cooling step is cooled below 15 degrees Celsius.

8. The method of claim 5, in which the air is cooled to about 10 degrees Celsius in the pre-cooling step.

5

9. The method according to any one of claims 1 to 8, which additionally comprises the step of continuously circulating the air in the work area (10).

10. The method according to claim 9, in which the circulation and drying 10 of the air by means of an outside of the work area (10) arranged

Air cycle sy stemes takes place, and which additionally includes the step of mixing in a fresh air portion.

11. The method of claim 10, wherein the ratio of circulated air 15 to fresh air is 90:10.

12. The method of claim 10, wherein the ratio of recirculated air to fresh air is 60:40.

13. The method of claim 10, wherein the ratio of recirculated air to fresh air is less than 50:50.

14. Device for processing, in particular drying, of paints in a work area (10), which comprises:

25 a. an air-filled, closed work area (10);

b. a paint application system for applying the paint to a surface to be painted; and

30 c. a drying system (20, 30), which the air in the above-mentioned beitsbereich (10) dries.

15. The apparatus of claim 14, wherein the drying system (20, 30) comprises an adsorption dryer (20).

16. The apparatus of claim 15, wherein the adsorption dryer (20) comprises silica gel or lithium chloride as adsorbent.

17. The apparatus of claim 15 or 16, in which the adsorption dryer (20) comprises an adsorption rotor (20 ') which consists of a ceramic composite material and is impregnated with the adsorbent.

18. The apparatus of claim 14 to 17, in which the adsorption dryer (20) has an adsorption line (21) and a separate regeneration circuit (29).

19. Device according to one of claims 14-18, in which the drying system (20, 30) additionally has a circulation and pre-cooling arrangement (30).