EP0854757A1

EP0854757A1 - Method and device for applying sprayable lacquers to the inner surface of unilaterally open packaging, and the corresponding internally lacquered packaging

Info

Publication number: EP0854757A1
Application number: EP96934680A
Authority: EP
Inventors: Terence Cooke
Original assignee: PPG Industries Inc
Current assignee: PPG Industries Ohio Inc
Priority date: 1995-10-14
Filing date: 1996-10-14
Publication date: 1998-07-29
Also published as: ZA968085B; WO1997014507A1; DE19538340A1; EP0854758A1; ZA968086B; AU7292696A; TW380058B; AU7292496A; AR003883A1; WO1997014506A1; AR003882A1; TW352345B

Abstract

The invention relates to a new method and a new device for applying sprayable lacquers to the inner surface of unilaterally open packaging (2), in particular of drinks cans, during the production of packaging, in particular drinks cans, in which method and device use is made on the production line of new types of spray heads (1) which have a dispensing head (6) with a plurality of spray nozzles. The atomising cone axes coming from at least two of these spray nozzles are arranged so as to be convex, i.e. they converge and overlap. The spray nozzles are mounted on the dispensing head (6) sides facing the packaging opening. The sides concerned incline towards the axis of rotation (12) of the turning, unilaterally open packaging with the result that the spray outlines (3a, 3b, 3c) which come from the spray nozzles hit at an angle the neck of the packaging 'neck', the packaging body directly behind the 'neck' ('neck shadow'), the packaging body, the inwardly-arched packaging bottom ('dome') and the bearing ring integrated into the packaging bottom ('rim'). Uncoated parts of the inner surface are then completely coated using a conventional spray head. However, it is also possible firstly to coat using a conventional spray head and subsequently a new type of spray head. The new process produces inner coatings in a very purposeful manner with either a uniform or substantially uniform thickness, or different thicknesses depending on the area.

Description

Method and device for applying spray paints to the inner surface of one-sided open packaging and the corresponding internally coated packaging

description

The invention relates to a new method for applying spray paints to the inner surface of one-sided open packaging, in which the packaging to be coated

1) is rotated about the axis of symmetry that passes through its packaging opening (axis of rotation),

2) with continued rotation, its opening is guided in front of a hydraulic or pneumatic spray head which has a spray nozzle from which a spray cone originates and which is located in front of the opening during the spraying process,

3) is sprayed on its inner surface with continued spraying with the spray paint and

4) is optionally fed to further spray heads, where process steps (1) to (3) are repeated.

In addition, the present invention relates to a new device (spray station) for performing the new method, which (A) at least one arrangement for feeding packaging that is open on one side before a hydraulic or pneumatic spray head,

(B) a hydraulic or pneumatic spray head with a spray nozzle from which a spray cone emerges,

(C) electronic, mechanical, pneumatic and / or hydraulic arrangements for controlling the spray conditions,

(D) where appropriate, arrangements for continuing the packaging coated in their interior in front of any further spray heads (B) which may be present,

(E) an arrangement for guiding the packaging coated on the inside away from the spray head or the spray heads and from the device,

(F) at least one arrangement for rotating the packaging around its axis of rotation,

contains.

Furthermore, the present invention relates to a new spray head for applying spray paints to the inner surface of packaging that is open on one side. Last but not least, the present invention relates to packaging which has been coated on the inside in the device according to the invention by the method according to the invention.

Processes of the type mentioned at the outset for the internal coating of packaging that is open on one side in high-speed production lines are known. Examples of packaging, which are made from the open on one side, are in particular cans for beer and other beverages. They are generally referred to by experts as "two piece cans".

These production lines usually contain commercially available devices or spray stations for applying spray paints, which have the above arrangements (A) to (F). These devices generally have two hydraulic or pneumatic spray heads, each with a spray nozzle. However, devices are also used which have only one spray head with one spray nozzle. In order to meet the specifications required by the packaging manufacturers, in particular the beverage can manufacturers, two of these spraying stations must be present.

US Pat. No. 5,366,162 describes a spray head for coating open-sided packaging, which carries two spray nozzles which direct two non-overlapping, fan-shaped spray figures ("fans") with diverging cone axes onto different areas of the inner surface of the packaging. In this way, the goal should be achieved are able to direct coating agents into the necessary areas of the packaging with increased efficiency and thereby minimize losses due to overspray and deposits on the nozzles. With the arrangement of the nozzles disclosed, in particular an uneven coating thickness is achieved, which reaches a minimum in the middle of the packaging wall. However, such a thickness distribution is not optimal for all types of packaging and coating requirements. In addition, the problem arises from the two diverging spray cone axes that the two spray cones, starting from the spray head, assume a very large solid angle. The spray head must therefore be positioned close to the opening of the packaging so that overspray does not result in excessive losses. There can also be difficulties when coating elongated packaging, since the spray cones diverge too much to reach the packaging floor.

Although the inner coating in the production lines could be improved a little more by providing a second or third spraying station, this is always forbidden for reasons of space and production speed: each additional processing station would increase energy costs and lower overall speed, both of which cannot be accepted by beverage can manufacturers for economic reasons.

For the same reasons, it is also disadvantageous to improve the inner coating, in particular on the lower packaging hull and the inwardly curved packaging floor ("dome") with the integrated standing ring ("rim") by means of a high-pressure spray lance, because this only enters the interior the packaging has to be inserted and withdrawn from it after the spraying process.

Due to economic constraints, the packaging manufacturers and in particular beverage can manufacturers must continuously increase the speed of their production lines. As a result, the time available for the inner coating becomes less and less. Conventional coating technology quickly reaches a limit here. Either it turns out to be a bottleneck in terms of production technology, because a certain spraying time must not be undercut if you want to achieve interior coatings that meet specifications. Or you are satisfied with the inner coating, which is obtained within the shorter spraying time. In this case, however, the disadvantages of conventional technology become particularly apparent, particularly in the case of modern beverage cans with their pronounced "rims", their more complex "domes" and, if appropriate, their brand-typical shaped hulls. In the case of steel cans, in contrast to aluminum cans, it is aggravated that the neck area of the can is narrowed even before the coating. The disadvantages are exacerbated by the current use of aqueous spray paints.

These disadvantages consist in an ineffective use of the spray stations, a distribution of the inner coating, which does not meet the requirements, especially in the "neck" area and in the area of the packaging directly behind the "neck"("neckshadow"), an excessive spray paint consumption and a low adaptability to new ones Packaging forms, spray paints and spray conditions. In particular, the unsatisfactory distribution of the inner coating can reduce the usefulness of the packaging concerned or even completely destroy it. In this way, aggressive and corrosive packaging fillings can remove metal from the area of the "neck" and "neck shadow", after which the use of the packaging concerned in the food and beverage sector is automatically prohibited. The only way to counteract this is by generally strengthening the inner coating, which, however, cannot be a permanent solution for economic reasons alone and for reasons of resource consumption.

The object of the present invention is to find a new process for applying spray paints to the inner surface of unilaterally open packaging, which no longer has the disadvantages of the prior art, but instead enables the short time required in modern production lines it is still available, depending on the requirement, to produce a uniform or largely uniform coating or a coating of different thickness depending on the location, whereby only as much spray paint as is absolutely necessary should be used. In addition, the new method should make it possible to achieve an excellent internal coating in the critical areas "neck", "neck shadow", "dome" and "rim", so that corrosion problems caused by insufficient coating no longer occur. Furthermore, the new process should be able to be easily adapted to new packaging forms, spray paints and spray conditions. Last but not least, the new one Processes can do without additional spray stations of the type mentioned.

In addition, it is the object of the present invention to find a spray head and, moreover, a device with which the new method for applying spray paints to the inner surface of packaging that is open on one side can be carried out particularly simply and efficiently, and which can perform the abovementioned ones No longer have disadvantages of the prior art.

Furthermore, it is an object of the new invention to provide packaging, in particular beverage cans, which have inner coatings which are excellently adapted to the respective requirements and which also require less spray paint than the inner coatings of the prior art.

Surprisingly, the object of the present invention could be achieved with the help of the new method, the new spray head and the new device for applying spray paints on the inner surface of packaging that is open on one side and with the packaging coated with it. The new method and the new device make use of a spray head according to the invention, whereby

a) the spray head contains a distributor head with at least two outlet openings, which have channels with a

Spray paint supply are connected, b) cone-like spray figures can be generated with the outlet openings, which have predetermined minimum and maximum opening angles and a predetermined orientation of the spray cone axis, and

c) the spray head can be used in a device for applying spray paints to the inner surface of open-sided packaging, there being a positioning axis which is fixed relative to the spray head and which, in the inserted state of the

Spray head is parallel to the axis of rotation of the packaging,

and which is characterized in that

d) at least two of the spray cone axes are convex, i.e. that in one or both of them the point is at the shortest distance from the other spray cone axis in the spray direction behind the outlet opening.

The new process for applying spray paints to the inner surface of one-sided open packaging, in which the packaging to be coated

1) is rotated about the axis of symmetry that passes through its packaging opening (axis of rotation), 2) with continued rotation, its opening is guided in front of a hydraulic or pneumatic spray head which has at least one spray nozzle from which a spray cone originates and which is located in front of the opening during the spraying process,

3) sprayed with the spray paint on its inner surface with continued rotation, and

4) if necessary, it is fed to further spray heads, where process steps (1) to (3) are repeated,

is characterized in that at least one spray head according to the invention is used.

Another object of the present invention is the new device (spray station) for performing the new method, which

(A) at least one arrangement for feeding packaging that is open on one side before a hydraulic or pneumatic spray head,

(C) electronic, mechanical, pneumatic and / or hydraulic arrangements for controlling the spray conditions, (D) where appropriate, arrangements for continuing the packaging coated in their interior in front of any further spray heads (B) which may be present,

(E) arrangements for guiding the packaging coated on the inside away from the spray head or spray heads and from the device,

contains and which is characterized in that at least one spray head according to the invention is used.

Furthermore, the internally lacquered packaging, which has been produced with the aid of the new method and the new device for applying spray paints to the inside surface of packaging that is open on one side, are the subject of the present invention and their use for the packaging of foods.

In view of the prior art, it was not to be expected that the object on which the invention was based could be achieved by the new process for applying spray paints to the inner surface of packaging which was open on one side and by the new spray head or the new device, the extraordinarily numerous advantageous Design options of the new method on the one hand and the equally numerous design options of the new device on the other hand were even more surprising. For the person skilled in the art, however, the significant advantage was completely unpredictable that with the aid of the new device and the new process, aqueous spray paints with a considerably higher solids content than previously possible could be processed without problems.

For the sake of brevity, the following describes the new process for applying spray paints to the inside of one-sided open packaging as the "process according to the invention", the new device for carrying out the process according to the invention as the "device according to the invention" and the process according to the invention in the device according to the invention internally painted packaging depending on what is referred to as "packaging according to the invention" or "beverage cans according to the invention".

An essential element of the invention is the spray head according to the invention for applying spray paints to the inner surface of packaging that is open on one side. This spray head contains a spray paint supply, which in principle can be a commercially available arrangement, and a distributor head, which is connected to the spray paint supply. The distributor head has at least two outlet openings which are connected to the spray paint supply via channels. In this case, nozzle inserts can be arranged in the outlet openings of the distributor head. This can again be commercially available components. It is also possible to design the outlet openings themselves so that they can dispense the spray paint in a suitable manner. For example, the outlet nozzles can be made in one piece with the Distribution head be formed. The following always speaks of nozzle inserts, but the information applies equally to the other configurations of the outlet openings mentioned. Cone-like spray figures can be created with the nozzle inserts. These arise because spray paint droplets are ejected out of the nozzle inserts in a more or less straight line. The space of the trajectories of these droplets forms the so-called spray figure. In the present invention, the spray figures are cone-like. For example, they can have the shape of a mathematical cone with an elliptical base surface, which can be characterized by a minimum and a maximum opening angle. For the sake of simplicity, "spray cones" are referred to below, although more general, cone-like spray figures are expressly to be included. The spray cones have a defined, ie predetermined and reproducible opening angle and a defined orientation of the cone axis. From a mathematical point of view, the cone axis is understood to mean the beam that begins at the cone tip and runs along the bisector of the opening angle. The spray head is also set up to be used in a device for applying spray paints to the inner surface of packaging that is open on one side ("spray station"). This is usually done using standardized threads on the spray head holder. In a spray head used in this way in a spray station The nozzle inserts with their spray cones face the opening of the packaging. There is then a reference axis fixed in the spray head, which is parallel to the axis of rotation of the packaging. This is referred to as the "positioning axis", since it is an important reference axis for the alignment of the spray head. If the spray head can only be inserted into the spray station in a single fixed position, the positioning axis is fixed except for parallel displacements. However, it is explicitly included in the scope of the invention that a spray head can also be arranged in the spray station in several different positions - possibly also during the spraying process. In this case there can be several positioning axes that are not parallel to each other. As a rule, the positioning axis (or one of the positioning axes) will coincide with an axis characterized by the geometry of the spray head. This can be, for example, its longitudinal axis or the axis of the spray paint supply. The spray head according to the invention is characterized in that at least two of the spray cone axes are arranged convexly, ie that in one or both of them the point lies behind the outlet opening with the shortest distance to the other spray cone axis in the spray direction. A spray paint particle that moves along such a spray cone axis first approaches the other spray cone axis until it passes through the point of the shortest distance. It can therefore also be said that the two convex spray cone axes (initially) converge on one another.

The particular advantage of convex cone axis arrangements is that the spray paint is initially held closer together after leaving the spray head than with diverging cone axes. This avoids or minimizes spray paint losses that can occur outside the packaging. Within the scope of the invention, it is possible to implement all conceivable arrangements of nozzle inserts and spray cones by means of a corresponding configuration of the distributor head. In principle, there are no limits to the number of nozzle inserts, the alignment of the spray cone axes and the opening angles of the spray cones, provided that at least two of them are arranged convexly and it is guaranteed that the cones do not overlap before and when the inner surface of the packaging is reached. In particular, it is also part of the scope of the invention to use differently sized nozzle inserts in the same spray head in order to thereby produce spray cones of different sizes, which in particular also transport a differently strong flow of spray paint. In this way it is not only possible to control which parts of the inner surface of the packaging are hit, but also how much coating agent is deposited there.

In a preferred arrangement of the nozzle inserts, at least two of them and at least one spray cone axis are arranged in one plane. All nozzle inserts can preferably also lie in such a plane. This arrangement enables a particularly flat and compact construction of the distributor head.

A plurality of spray cone axes can preferably also lie in the same plane, in particular this condition can also be fulfilled for all nozzle inserts used. With this arrangement, however, it should be noted that the spray cones, whose cone axes are in the same plane, must not overlap. To avoid such overlap problems, it is therefore possible for at least two of the spray cone axes to be arranged in two parallel planes which are at a distance (different from zero). As long as the diameter of the spray cones does not exceed a certain value, the corresponding spray cones cannot overlap. Due to this spaced arrangement, it is therefore easier to align the spray cones without overlap and, in particular, to allow them to be crossed.

If the cone axes lie in the same plane itself, cutting the convex cone axes at one point inevitably leads to penetration of the spray cones. Since this penetration of the spray cones is not desired, the convex cone axes are preferably arranged in parallel planes. In this case, as described above, the distance between the planes and a penetration-free crossing of the spray cones can be used. Arrangements are preferred in which all, in particular three, cone axes are arranged convexly. According to the above explanations, all the taper axes lie in parallel planes at different distances from one another.

The arrangement of the convex nozzle inserts on the inner surface of an (imaginary) ball is also particularly advantageous. This can be achieved, for example, in such a way that the end of the distributor head facing the packaging has a spherically curved shape inwards. An arrangement has also proven to be particularly advantageous in which at least two cone axes are arranged convexly and with the positioning axis an angle of 10 to 18 °, preferably 13 ° (1st cone), or 50 to 70 °, preferably 60 ° ( 2nd cone). Here and in the following, the angle between any two non-intersecting straight lines lying in space is understood to mean the angle which they form with one another when they are brought to the cut by parallel displacement.

Further preferred angle values of the arrangement described are 0 to -12 °, preferably -6 ° (1st cone), or 50 to 70 °, preferably 60 ° (2nd cone).

Other preferred angle values of this arrangement are 15 to 25 °, preferably 20 ° (1st cone), or 50 to 70 °, preferably 60 ° (2nd cone).

In the case of an arrangement in which at least two cone axes are spaced apart in parallel planes as described above, this spacing is 1 to 10 mm, preferably 2 to 5 mm, very particularly preferably 3 mm.

The spray cones of the spray head according to the invention can have an opening angle of 5 to 60 °, preferably 5 to 45 °.

The invention further relates to a device (spray station) for applying spray paints to the inner surface of one-sided open packaging. According to the invention, devices are suitable which have at least one arrangement (A) for feeding packaging that is open on one side before a hydraulic or pneumatic spray head. Arrangements of this type are customary and known and are based on the conveyor technology which is usually used in the production lines of packaging manufacturers, in particular beverage can manufacturers.

The devices according to the invention also contain at least one hydraulic or pneumatic spray head, as are generally used in the production lines in question here. Spray heads of this type are available on the market, for example, under the trade name "Nordson Standard Gun".

Such a known spray head usually contains a spray nozzle from which the spray paint is sprayed. The spray paint spreads out in a cone-like shape as described above, which is referred to in the context of the present invention as a spray cone. If necessary, the spray cone can be directed towards the packaging with electrostatic arrangements.

Furthermore, the device according to the invention contains the electronic, mechanical, pneumatic and / or hydraulic arrangements (C) which are necessary for controlling and regulating the spray conditions and are usually used in devices of the type in question here. Further components of the device according to the invention can be arrangements (D) which guide the packaging which is open on one side and which has been coated on the inside by means of a spray head, in front of further spray heads. For this, the arrangements (D) come into consideration, as are usually used for the feeders (A). The usual and known spray heads mentioned above can be used as further spray heads.

The device according to the invention contains arrangements (E) which serve to lead the packaging according to the invention away from the spray head or any further spray heads which may be present, and from the device according to the invention. Such arrangements (D) are common and known and are similar in principle and in terms of their operation to arrangements (A) or (D).

Last but not least, the device according to the invention contains at least one arrangement (F) for rotating the packaging that is open on one side about its axis of rotation, which is understood to mean the axis of symmetry that passes through the center of the packaging opening and the packaging base. Here, arrangements (F) are used as are customary and known in the technical field in question.

For the device according to the invention, it is essential to the invention that its spray head or at least one of its spray heads is designed as a spray head according to the invention as described above. If devices according to the invention are used with a plurality of spray heads, the first spray head from the point of view of the one-sided open packaging can be a spray head according to the invention or a customary and known spray head. In this case, only the second or third spray head would be the one according to the invention. However, it is advantageous for the device according to the invention if the first spray head is the one according to the invention.

Although there may be three, four or more spray nozzles on the spray head according to the invention, two spray nozzles have proven to be particularly advantageous for design, material technology, production, process and control reasons. With their help, the advantages according to the invention can be achieved in full.

Suitable spray nozzles (nozzle inserts) for the spray head according to the invention are all spray nozzles as are usually used in the known spray heads. Overall, the possibility of using customary and known arrangements and components for the spray head according to the invention, apart from the distributor head, has proven to be a further particular advantage of the device according to the invention.

It is advantageous for the device according to the invention if the longitudinal axis of the spray head according to the invention is parallel to the axis of rotation of the packaging which is open on one side. Slight deviations can be tolerated, but these can make it more difficult to regulate the spray conditions. It is also advantageous if the spray nozzles are arranged on the spray head according to the invention in such a way that the spray cones are inclined against the axis of rotation. This can be achieved in a simple manner constructively in that the surfaces of the distributor head according to the invention facing the packaging opening, in which the spray nozzles are located, are chamfered in the required manner.

Although here too there is basically the possibility of realizing the inclination of the spray cones against the axis of rotation by inclining the entire arrangement which carries the spray head according to the invention, this would however require a higher technical outlay. Instead, the use of distributor heads according to the invention with differently beveled surfaces carrying spray nozzles offers the extraordinary advantage that the device according to the invention can be adapted at any time in a simple manner to the respective production process and the packaging that is open on one side, without changing the entire spray station significantly to have to.

For the spray head according to the invention, it is also advantageous if the spray nozzles are arranged in such a way that the bisector of the opening angle of at least one spray cone (spray cone axis) lies in the plane in which the axis of rotation of the unilaterally open packaging and the longitudinal axis of the spray head are located. Due to the high symmetry of this arrangement, the process parameters can be determined and controlled particularly easily. The spray nozzles are advantageously arranged in such a way that the first spray cone ("first spray cone", with the shortest distance to the packaging) seen in the direction of the "packaging opening-packaging base" strikes the inner surface immediately behind the packaging opening. In addition, it is ensured by a corresponding arrangement that the last spray cone ("last spray cone") seen in the direction of the "packaging opening-packaging floor" strikes the inner surface immediately in front of the packaging floor, the internal surface of the packaging floor or these two internal surfaces at the same time. Which of the three advantageous variants is chosen depends primarily on the geometry of the packaging.

It is particularly advantageous to arrange the spray nozzles in such a way that the last spray cone hits the inner surface immediately in front of the packaging floor and on the inner surface of the packaging floor. Its target area should advantageously cover 10 to 90% of the inner surface of the packaging base. In the context of the present invention, “impact surface” is always to be understood as the part of the inner surface which would be covered by a spray cone if the packaging which was open on one side were not rotating, but at rest. Below 10% of the inner surface of the packaging base, a single spray cone can no longer coat the rotating packaging base to the extent that would be desirable. With an impact area of more than 90%, the spray cone can be scattered on the edge of the packaging opening. In the range of 10 to 90%, therefore best results achieved, which is why the corresponding spray nozzle arrangement is advantageously used.

The spray nozzles can furthermore be arranged such that their contact surfaces cover 10 to 90% of the entire inner surface of the packaging. Below 10% of the total inner surface, the particular advantages of the device according to the invention are no longer noticeable to the extent that this would be desirable. If, on the other hand, you select more than 90% of the entire inner surface as the impact surface, problems such as scattering of the spray cones at the edge of the opening of the packaging can arise due to the packaging geometry. The best results are therefore achieved in the range from 10 to 90%, which is why the corresponding spray nozzle arrangement is used with advantage.

The spray nozzles are advantageously arranged such that the spray cones do not overlap. Although embodiments are conceivable in which the spray cones overlap to a certain extent, problems in the area of the overlap can result in the precise regulation of the spraying conditions, caused by scattering of the spray paint.

The spray nozzles are advantageously arranged so that the bisectors of the opening angles of the spray cones (cone axis) form angles between 5 and 70 °, in particular between 10 and 45 °. Below 5 °, either the spray cones would be too pointed and the impact surfaces would be too small for practical purposes, or the spray cones would have to be overlap to a significant extent, which would be less advantageous. At angles above 70 °, problems may arise due to the geometry of the packaging, such as scattering of the spray cones at the edge of the packaging opening. Accordingly, the range from 5 to 70 ° proves to be advantageous, the range from 10 to 45 ° providing particularly good results. The corresponding arrangement of the spray nozzles is therefore particularly preferred.

If the taper axes do not intersect, but run anywhere in the room, they can only be brought to the intersection by parallel displacement in order to determine the intersection angle.

Spray nozzles are advantageously used in the spray heads according to the invention, which spray the spray paint in a spray cone with an opening angle of 5 to 60 °, in particular 5 to 45 °. Since below 5 ° the particular advantages of the device according to the invention can only be achieved with increased control effort, because the impact surface is too small or too thick a coating results in a narrow band, it is advantageous to use spray nozzles which have spray cones with a larger opening angle send out. Spray nozzles which produce spray cones with angles wider than 60 ° can be used, but also lead to control problems. In addition, there is also the risk of scattering at the edge of the packaging opening. Of the spray nozzles mentioned, those which spray spray cones with an opening angle of 5 to 45 ° have proven particularly advantageous. They deliver the best coating results. The spray nozzles can be arranged in such a way that the bisectors of the angles of the opening angles of the spray cones (cone axis) form angles of 10 to 85, in particular 15 to 60 °, with the packaging body and / or its escape line. This can be accomplished in a simple manner by the corresponding inclination of the distributor head surfaces in which the spray nozzles are located. If the spray cones hit the inner surface to be coated with the appropriate inclination, particularly good coating results are achieved. Within the range from 10 to 85 °, the one from 15 to 60 ^{u should} be emphasized because this gives the best results.

Overall, the spray nozzles should be arranged in such a way that the walls of the spray cones do not touch the edge of the packaging opening. This avoids an overspray and thus a considerable loss of spray paint, irregular interior coatings and hygiene problems from the outset. An exception, however, can be the spray nozzle of the "first spray cone". This can be designed so that the volume of the "first spray cone" extends beyond the edge of the packaging opening, so that an "overspray" is deliberately generated. This procedure proves to be advantageous if a packaging has to be coated with a particularly elongated and / or tight "neck". In this case, it is advisable to provide the collecting and suction devices as are customary and known in the field of painting technology, and to keep the "overspray" as low as possible. The person skilled in the art can carry out the design and the adaptation of the device according to the invention to a given production process with certain packaging forms that are open on one side at any time on the basis of the geometrical spatial relationships shown. If necessary, he can experimentally verify his theoretical considerations for the design and adaptation by simple preliminary tests and, if necessary, carry out a fine-tuning.

The method according to the invention is carried out with the device according to the invention described above or using the spray head according to the invention.

Accordingly, it is essential for the process according to the invention that two or more spray cones of a spray paint strike simultaneously on the inner surface of the open-ended packaging under optimal conditions with regard to the special packaging. This is achieved according to the invention by using at least one spray head according to the invention with a distributor head and several, but in particular two, spray nozzles.

The process according to the invention is carried out in the course of the production of coated packaging, in particular beverage cans, in the customary and known production lines. Here, the packaging that is open on one side is rotated around the axis of symmetry that passes through its packaging opening (axis of rotation). With continued rotation, it is guided with its opening in front of at least one hydraulic or pneumatic spray head. If only one spray head is used, it is the invention. If several spray heads are present, the first spray head from the point of view of the packaging that is open on one side can be the one according to the invention. This variant is advantageous according to the invention and is therefore preferably used.

Spray cones emanate from the spray nozzles of the spray heads or the spray head according to the invention, and during the spraying process the spray heads or the spray head according to the invention are always in front of the opening of the packaging which is open on one side. Your inner surface is then sprayed in this position with continued rotation with the spray paint, and then the packaging, which is open on one side, is optionally fed to further spray heads or finally led away from the spray station according to the invention.

In the method according to the invention, application conditions are used as are customary and known in the field of interior coating of packaging, in particular beverage cans. For example, the packaging that is open on one side can be rotated about its axis of rotation at speeds of 500 to 3000, in particular 1500 to 2500, rpm. Depending on the requirements and the size of the packaging that is open on one side, the coating time can be 80 to 500, preferably 100 to 200 and in particular 110 to 150 ms. Different amounts of spray paint can be applied. In conventional and known beverage cans, this can be 80 to 200, preferably 90 to 180, and in particular 100 to 160 mg dry weight. The application pressure can range from 10 to 100, preferably 20 to 70 and in particular 30 to 65 bar. The temperature of the spray paint before spraying is generally at room temperature or slightly above.

When carrying out the method according to the invention, the spray head according to the invention with the positioning axis is parallel to the axis of rotation, the spray cones being inclined against this. In a particularly advantageous embodiment of the method according to the invention, the bisector of the opening angle of at least one spray cone (cone axis) lies in the plane in which the axis of rotation of the packaging is located. Here, the "first spray cone" can strike the inner surface immediately behind the opening of the packaging and the "last spray cone" on the inner surface immediately in front of the packaging floor, the inside surface of the packaging floor or these two inside surfaces. In most cases, preference is given to the last variant of the method, it having turned out to be particularly advantageous if the impact surface of the "last spray cone" covers 10 to 90% of the inner surface of the packaging base. As a result, by turning the packaging, a particularly uniform inner coating in the critical "thorn" and "rim" area is achieved in terms of its application properties.

It is also advantageous if the inner surface is sprayed in such a way that the contact surfaces of all spray cones cover 10 to 90% of the entire inner surface of the packaging. This is not only on the

Emballage body, but also in the critical "neck" - and "neck shadow" - Area achieved a particularly uniform interior coating with optimal application properties.

It should be emphasized that the interior coating applied under the specified conditions after drying and after customary and known curing, for example by heating against aggressive and corrosive packaging fillings, is extremely stable and non-porous and thus offers excellent corrosion protection.

By means of further advantageous refinements of the method according to the invention, its implementation and the inner coatings of the packaging according to the invention produced therewith can be optimized. It is advantageous if the spray cones do not overlap or only overlap to a small extent, since otherwise there may be uncontrolled spray paint deposition in the overlap area.

It is also advantageous if the bisectors of the opening angles of the spray cones (cone axis) form angles between 5 and 70 °, in particular 10 and 45 °. The spray cones particularly preferably have opening angles of 5 to 60 °, in particular 5 to 45 °. The bisector of the opening angle of the spray cone with the body and / or its escape line can form angles of 10 to 85, in particular 15 to 60 °. These process measures result in an optimal impact area overall, which has a positive effect on the application properties of the inner coatings. When carrying out the method according to the invention, the walls of the spray cones should not touch the edge of the packaging opening, because this produces undesirable "overspray". In addition, uncontrolled separation of spray paint can occur inside the packaging due to scatter. The "first spray cone" can make an exception, the volume of which can extend beyond the edge of the packaging opening. As a result, a particularly excellent internal coating is achieved, especially in the critical "neck" area. However, one will take care to produce as little "overspray" as possible.

Due to the use of several spray nozzles for one spraying process, an inner coating can be applied which has the same or approximately the same thickness regardless of the location. This is particularly advantageous in the coating of aluminum beverage cans, where this is required by the beverage can manufacturers. However, it is the special feature of the method according to the invention that it is not limited to this, but that it can also be used to produce an inner coating which has a different thickness depending on the location. In this way it is possible to provide the critical "rim", "neck" and "neck shadow" areas with an optimally strong inner coating without the need to apply an excessive amount of spray paint to the packaging body. This results in an overall reduction in the amount of spray paint to be applied, which represents a further particular advantage of the method according to the invention. After the inner coating in the procedure according to the invention, the entire inner surface of the packaging does not necessarily have to be completely covered with spray paint, but instead, for example, only the "thorn", "rim", "neck" and / or "neck shadow" area and a Part of the packaging hull be coated. In these cases, it is advisable to supply the packaging to at least one other conventional and known spray head, by means of which the parts of the inner surface which are still free can be coated.

However, the variant can also be selected in which the unilaterally open packaging is first coated by means of a conventional spray head and then only with the aid of the invention. This also results in a complete inner coating.

After the process according to the invention has been carried out, the spray paint applied is dried and, for example, cured by heating, whereby a hardened lacquer layer, i.e. the finished inner coating results.

The process according to the invention can be carried out with all spray paints as are customary in the field of the inner coating of packaging that is open on one side, in particular beverage cans. A particular advantage is shown when using aqueous spray paints: it is possible to use aqueous spray paints which, based on their respective total amount, have a solids content of more than 22% by weight, in particular 25% by weight. Thanks to the conventional spraying process aqueous paints with such a high solids content can no longer be processed. In this respect, the method and the device according to the invention thus prove to be superior to the prior art.

Examples of aqueous spray paints are described in EP-417,091, EP-116,225, EP-006,334, EP-006,336 and DE 3006 175.

A spray paint suitable according to the invention consists of a self-emulsifying epoxy ester copolymer mixture. This is produced in a process in which a polymer which contains carboxyl groups and is soluble in a solvent is esterified with an epoxy resin. The epoxy resin is a mixture containing aromatic polyethers with epoxy groups, at least 5% of the aromatic polyethers being composed of diepoxide. The mixture of the aromatic polyethers makes up about 40% of the total solids content of the resin and provides the epoxy groups which are present in a stochiometric sub-ratio of 1: 2 to 1:20 with respect to the carboxyl groups. The esterification takes place in an organic solvent in the presence of more than 2% (based on the total weight of the reactants of the esterification) of an aminic esterification catalyst. The temperature is raised sufficiently to drive the reaction of the epoxy groups with the carboxyl groups until the epoxy groups have essentially been consumed and until at least some of the carboxyl groups in the resulting polymer-epoxy resin have a hydroxy-ester product of a base have reacted to make the reaction product self-emulsifying in water.

An ungelled hydroxy ester copolymer composition which is essentially free of epoxy groups and which contains the hydroxy ester product of an acidic copolymer with epoxy resin is also suitable as spray paint according to the invention. The epoxy resin is a mixture containing at least 5% by weight of an aromatic polyether which bears two epoxy groups and is consumed in the reaction with the acidic copolymer. The acidic copolymer is a dissolved copolymer of monoethylenically unsaturated monomers containing at least about 20% (based on the total weight of the monomers) of a monoethylenically unsaturated carboxylic acid. The epoxy resin mixture makes up at least 40% of the total solids content of the resin and provides the epoxy groups which are present in a stochiometric sub-ratio of 1: 2 to 1:20 with respect to the carboxyl groups. At least a portion of the carboxyl groups in the resulting copolymer epoxy hydroxy ester product react with a base to make the reaction product self-emulsifying in water.

Another usable aqueous spray paint contains the neutralized, water-dispersible ionic polymer from the reaction of an epoxy resin with an acidic polymer and also another resin which is not necessarily self-dispersible in water. The other resin is either supplied preformed at any stage, or is added in situ either before or after the ionic epoxy resin is dispersed. acidic polymer product in water prepares in the presence of the epoxy resin that is esterified with the acidic polymer. The epoxy resin acid-polymer product behaves as a polymeric surface-active substance, which can even keep the normally non-self-dispersible second polymer in a stable aqueous dispersion.

The following known spray paint can also be used in the system according to the invention. This varnish is obtained by the addition reaction of a monomer, e.g. Styrene, in a reaction medium containing a modified epoxy resin. The epoxy resin is modified by combining some of its epoxy groups with epoxy-reactive groups of an ethylenically unsaturated monomer and by reacting others of its epoxy groups with a tertiary amine and a preformed addition polymer containing carboxyl groups to form an ionic resin compound, with enough carboxyl groups present are to make the paint self-dispersible in water in neutralized form.

Finally, a coating resin composition in the form of an aqueous dispersion can also be used, containing an aromatic epoxy resin component and an acrylic resin component which has been copolymerized from acrylic acid or methacrylic acid and a monoethylene monomer and has excess carboxyl groups, and ammonia or an amine for partial neutralization. The pH of this coating composition is between 5 and 11. The epoxy resin component and the acrylic resin component are in the form of a partial reaction product (A) an alkali-neutralizable acrylic resin with a number average molecular weight of 5,000 to 100,000, which by copolymerization of 12 to 50% by weight of acrylic acid or methacrylic acid with 50 to 88% by weight of styrene, methylstyrene, vinyltoluene and alkyl esters of acrylic acid and / or methacrylic acid with 1 to 8 carbon atoms in the alkyl group, and (B) an aromatic epoxy resin having an average of 1.1 to 2.0 epoxy groups per molecule and a number average molecular weight of at least 1400, except for a coating composition containing a nonionic surfactant.

Aqueous spray paints which can be processed particularly well with the aid of the process according to the invention

(I) at least one water-soluble or water-dispersible binder which has acid groups, in particular carboxyl groups, and

(II) at least one epoxy resin with more than one epoxy group per molecule.

Advantageously, the components (I) and (II) contain in a ratio (I): (II) of 0.1 to 2.

Aqueous spray paints are particularly preferred, as component (I) of which at least one copolymer is used which is characterized by Copolymerization of a mixture of, based in each case on the total amount of the mixture,

(Ia) 10 to 45% by weight of at least one α, β-unsaturated carboxylic acid, in particular acrylic acid, methacrylic acid and / or itaconic acid,

(lb) 10 to 35% by weight of at least one aromatic vinyl monomer, in particular styrene, 2-, 3- and / or 4-alkylstyrene and / or α-methylstyrene, and

(Ic) 20 to 80% by weight of at least one alkyl and / or aryl ester of at least one α, β-unsaturated carboxylic acid (Ia)

can be produced.

Furthermore, powder coating slurries can also be used with the spray heads according to the invention. Suitable powder coating slurries can be produced by an aqueous dispersion of a clear powder coating with a glass transition temperature of 20 to 90 ° C, a viscosity of 10 to 1000 mPas and a solids content of 10 to 50%, a grinding process while maintaining a temperature of 0 to 60 ° C is subjected. They preferably consist of a solid, powdery component A and an aqueous component B, component A being a powder clearcoat comprising a) at least one epoxy-containing binder with a content of 30 to 45% by weight, preferably 30 to 35% by weight, of glycidyl-containing Monomers optionally containing vinyl aromatic compounds, preferably styrene, b) at least one crosslinking agent, preferably straight-chain, aliphatic dicarboxylic acids and / or carboxy-functional polyesters, and c) optionally catalysts, auxiliaries, additives typical of powder clearcoat such as degassing agents, leveling agents, UV absorbers, radical scavengers, antioxidants and component B is an aqueous dispersion comprising a) at least one nonionic thickener and b) optionally catalysts, auxiliaries, defoamers, wetting agents, dispersion auxiliaries, preferably carboxy-functional dispersants, antioxidants, UV absorbers, radical scavengers, biocides, small amounts of solvents, leveling agents, Neutralizing agents, preferably amines and / or water retention agents.

Examples of suitable epoxy-functional binders for the solid powder clearcoat used for the preparation of the dispersion are epoxy group-containing polyacrylate resins which are obtained by copolymerizing at least one ethylenically unsaturated monomer which contains at least one epoxy group in the molecule with at least one further ethylenically unsaturated monomer which is none Contains epoxy group in the molecule, can be prepared, at least one of the monomers being an ester of acrylic acid or methacrylic acid. Such epoxy groups Polyacrylate resins are known, for example, from EP-A-299420, DE-B-22 14 650, DE-B-2749 576, US-A-4,091,048 and US-A-3,781,379.

Examples of ethylenically unsaturated monomers which do not contain any epoxy group in the molecule are alkyl esters of acrylic and methacrylic acid which contain 1 to 20 carbon atoms in the alkyl radical, in particular methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate and 2 -Ethylhexyl methacrylate called. Further examples of ethylenically unsaturated monomers which do not contain any epoxy groups in the molecule are acid amides, such as e.g. Acrylic acid and methacrylic acid amide, vinyl aromatic compounds such as styrene, methyl styrene and vinyl toluene, nitriles such as acrylonitrile and methacrylonitrile, vinyl and vinylidene halides such as vinyl chloride and vinylidene fluoride, vinyl esters such as e.g. Vinyl acetate and hydroxyl group-containing monomers such as e.g. Hydroxyethyl acrylate and hydroxyethyl methacrylate.

The epoxy group-containing polyacrylate resin usually has an epoxy equivalent weight of 400 to 2500, preferably 420 to 700, a number average molecular weight (determined by gel permeation chromatography using a polystyrene standard) from 2,000 to 20,000, preferably from 3,000 to 10,000, and a glass transition temperature (TG) from 30 to 80, preferably from 40 to 70, particularly preferably from 40 to 60 ° C to (measured with the aid of differential scanning calorimetry (DSC)). Approx. 50 ° C. is very particularly preferred. Mixtures of two or more acrylic resins can also be used. The epoxy group-containing polyacrylate resin can be produced by polymerization by generally well known methods.

Suitable crosslinkers are carboxylic acids, in particular saturated, straight-chain, 5 aliphatic dicarboxylic acids with 3 to 20 C atoms in the molecule. Dodecane-l, 12-dicarboxylic acid is very particularly preferably used. To modify the properties of the finished powder clearcoat materials, other crosslinkers containing carboxyl groups may also be used. Examples of these are saturated branched or 10 unsaturated straight-chain di- and polycarboxylic acids and polymers with carboxyl groups.

Powder clearcoats which contain an epoxy-functional crosslinker and an acid-functional binder are also suitable.

* 5

Suitable acid-functional binders are, for example, acidic polyacrylate resins which, by copolymerizing at least one ethylenically unsaturated monomer which contains at least one acid group in the molecule, with at least one further ethylenically unsaturated monomer,

20 which contains no acid group in the molecule, can be produced.

The epoxy group-containing binder or the epoxy group-containing crosslinker and the carboxyl group-containing crosslinker or the epoxy group-containing binder are usually used in an amount such that 0.5 to 1.5, preferably 0.75 to 1.25, equivalents of carboxyl groups are present per equivalent of epoxy groups. The amount of The carboxyl groups present can be determined by titration with an alcoholic KOH solution.

According to the invention, the binder contains vinyl aromatic compounds, in particular styrene. However, in order to limit the risk of cracking, the content is not more than 35% by weight. 10 to 25% by weight are preferred.

The solid powder coatings may contain one or more suitable catalysts for epoxy curing. Suitable catalysts are phosphonium salts of organic or inorganic acids, quaternary ammonium compounds, amines, imidazole and imidazole derivatives. The catalysts are generally used in proportions of 0.001% by weight to about 2% by weight, based on the total weight of the epoxy resin and the crosslinking agent.

Examples of suitable phosphonium catalysts are

Ethyltriphenylphosphonium iodide, ethyltriphenylphosphonium chloride,

Ethyltriphenylphosphonium thiocyanate, ethyltriphenylphosphonium acetate-acetic acid complex, tetrabutylphosphonium iodide, tetrabutylphosphonium bromide and tetrabutylphosphonium acetate-acetic acid complex. These and other suitable phosphonium catalysts are e.g. described in U.S. Patent 3,477,990 and U.S. Patent 3,341,580.

Suitable imidazole catalysts are, for example, 2-styrylimidazole, 1-benzyl-2-methylimidazole, 2-methylimidazole and 2-butylimidazole. This as well further imidazole catalysts are described, for example, in Belgian Patent No. 756,693.

In addition, the solid powder coatings can optionally also contain auxiliaries and additives. Examples of these are leveling agents, antioxidants, UV absorbers, radical scavengers, trickling aids and degassing agents, such as, for example, benzoin.

The solid powder coatings are produced by known methods (cf., for example, product information from the company BASF Lacke + Farben AG, "powder coatings", 1990) by homogenization and dispersion, for example by means of an extruder, screw kneader and others Powder coatings are prepared for dispersion by grinding and, if necessary, by sifting and sieving.

The aqueous powder clearcoat dispersion can then be prepared from the powder by wet grinding or by stirring in dry-ground powder coating. Wet grinding is particularly preferred.

In the production of aqueous powder coating dispersions based on the described component A, this is dispersed in a component B. The latter consists of an aqueous dispersion of catalysts, auxiliary substances, anti-foaming agents, antioxidants, wetting agents, UV absorbers, radical scavengers, biocides, water retention agents, small amounts Solvents and / or dispersing aids, preferably carboxy-functional dispersing aids.

As a further essential constituent, the aqueous component B of the powder coating dispersion contains at least one nonionic thickener a). Non-ionic associative thickeners a) are preferably used. Structural features of such associative thickeners a) are:

aa) a hydrophilic scaffold which ensures sufficient water solubility and ab) hydrophobic groups which are capable of an associative interaction in the aqueous medium.

Long-chain alkyl residues such as e.g. Dodecyl, hexadecyl or octadecyl residues, or alkaryl residues, such as e.g. Octylphenyl or nonylphenyl radicals used.

Polyacrylates, cellulose ethers or particularly preferably polyurethanes which contain the hydrophobic groups as polymer building blocks are preferably used as the hydrophilic frameworks. Polyurethanes which contain polyether chains as building blocks, preferably made of polyethylene oxide, are very particularly preferred as the hydrophilic frameworks. In the synthesis of such polyether polyurethanes, the di- and / or polyisocyanates, preferably aliphatic diisocyanates, particularly preferably optionally alkyl-substituted 1,6-hexamethylene diisocyanate, are used to link the hydroxyl-terminated polyether building blocks to one another and to link the polyether building blocks with them hydrophobic end group units which can be, for example, monofunctional alcohols and / or amines with the long-chain alkyl radicals or aralkyl radicals already mentioned.

After component A has been dispersed in component B, the mixture is optionally ground, the pH is adjusted to 4.0 to 7.0, preferably 5.5 to 6.5, and the mixture is filtered. The average grain size is between 1 and 25 μm, preferably below 20 μm, particularly preferably 3 to 1 μm. The solids content of the aqueous powder clearcoat dispersion is between 15 and 50%.

0 to 5% by weight of a defoamer mixture, an ammonium and / or alkali salt, a carboxy-functional or nonionic dispersion aid, wetting agent and / or thickener mixture and other additives can be added to the dispersion before or after the wet grinding or the introduction of the dry powder coating into the water be added. According to the invention, defoamers, dispersing aids, wetting agents and / or thickeners are preferably first dispersed in water. Then small portions of the powder clear lacquer are stirred in. Then defoamers, dispersing aids, thickeners and wetting agents are dispersed again. Finally, powder clear lacquers are stirred in again in small portions.

The pH is preferably adjusted with ammonia or amines. The pH value can initially rise that strongly basic dispersion arises. However, the pH falls back to the above values within several hours or days.

The packaging according to the invention produced in the procedure according to the invention, in particular the beverage cans according to the invention, are characterized by a uniform or largely uniform thickness of the hardened lacquer layer in the range of less than 15, preferably less than 10 and in particular less than 5 g / m 2. Here, all application-technical requirements, in particular regarding the corrosion protection and the impermeability of the layer even in the range below 5 g / m 2, are fully met.

The packaging and beverage cans according to the invention can, however, also be distinguished by a hardened lacquer layer which, depending on the location, has a different thickness in the range of less than 15, preferably less than 10 and in particular less than 5 g / m 2. The cured lacquer layer can have the following thickness: in the area of the "neck" under 10, in the area of the "neck shadow" under 8, in particular under 6, in the area of the packaging body under 6, in particular 5, in the area of the "dome" under 8, especially under 6, and in the area of the "rim" under 6, especially 5 g / π-Λ

These packaging and beverage cans according to the invention accordingly have an inner coating which, with less spray paint than before, meets the requirements of the packaging and beverage can manufacturers in an outstanding manner. Overall, because of the extraordinary quality of the inner coating produced thereby, the method and the device according to the invention enable the production of packaging of the invention with a capacity of more than 400 g from packaging that is open on one side. This will give the "two piece cans" access to the food cans market segment that was previously closed to them.

The spray head according to the invention and the device according to the invention are explained below using the figures as examples.

Figure la shows a spray head with two convex nozzle inserts. Figure lb shows a frontal view of this spray head. Figure 2 shows the coating of a packaging.

FIG. 1 a shows a side section through the spray head 1 according to the invention. The spray head initially consists of a commercially available spray head holder 4 with a channel for spray paint supply 5. This spray head holder 4 has an external thread onto which the distributor head 6 is screwed. Within the distributor head 6, the spray paint supply 5 merges into the channels 8a and 8b, which lead through the distributor head to the insert bores 7a, 7b. These insert bores 7a, 7b generally have an internal thread into which the nozzle inserts 9a, 9b can be screwed. The nozzle inserts 9a, 9b can be commercially available elements. In particular, different Nozzle inserts are used which differ, for example, in the opening angle and in the flow of the spray cones generated.

A positioning axis 11 is defined within the spray head 1 for reference. When using the spray head in a spray station, this positioning axis 11 must, by definition, be aligned parallel to the axis of rotation of the packaging. The positioning axis 11 in FIG. 1 a passes through a (arbitrarily defined) reference nozzle insert 9 b and is usually related to the geometry of the spray head, preferably by being parallel to the longitudinal extension of the spray head or the spray head holder or to the spray paint supply 5. In Figures 1 to 2 the "last" nozzle insert is always chosen as the reference nozzle insert, i.e. the one who has the greatest distance from the packaging in the usual application of the spray head. Furthermore, the positioning axis 11 is always parallel to the spray paint supply 5. In FIG. 1 a, the positioning axis 11 therefore runs through the nozzle insert 9b. The cone axes 13a, 13b of the spray cones, which emanate from the nozzle inserts 9a, 9b and are shown in broken lines in the figures, intersect the positioning axis 11 at the angles α and β. In Figure la, these angles are α = 60 °, β = -6 °.

The cone axis 13b of the reference nozzle insert 9b and the positioning axis 11 form a plane which contains both lines. When the nozzle inserts 9a, 9b are arranged in FIG. 1 a, the projections of their cone axes onto the plane mentioned (ie the plane of the drawing in FIG. 1 a) intersect at one point. This is also the point The shortest distance between the cone axes, and since it lies behind the nozzle inserts in the spray direction, the nozzle inserts are by definition "convex". The corresponding spray cones intersect. To prevent the cones from penetrating when the spray cones are crossed in this way, the invention can be used one of the nozzle inserts, namely 9a, is arranged at a distance in a parallel plane. This offset arrangement can be seen in the front view of the spray head according to FIG. 1a in FIG. 1b. The cone axes of the nozzle inserts 9a, 9b run in two parallel planes (perpendicular to Drawing plane in Fig. Lb) with a distance 10. Since the associated spray cones have not yet expanded very far in the crossover area, they do not penetrate each other.

FIG. 2 shows a spray head 1 according to the invention with three convex spray nozzles when coating a packaging 2 that is open on one side. This packaging 2 is located with its opening in front of the spray head 1 and is rotated about its central axis, which is the axis of symmetry of the packaging 2. This axis is therefore also referred to as the axis of rotation 12. The spray cones 3a, 3b and 3c extend from the spray nozzles of the spray head 1. They hit the bottom ("dome") and the lower body of the packaging, the middle body of the packaging, as well as the area immediately behind the can opening ("neck") in the order given.

Reference symbol list 2 = packaging

3a, b, c = spray cone

1 = spray head 4 = spray head holder 5 = spray paint supply

6 = distributor head

7a, b = insert hole

8a, b = channel

9a, b, c = outlet opening /

Nozzle inserts

10 = nozzle distance

11 = positioning axis

12 = axis of rotation

13a, b = cone axes α, ß = cutting angle

Ya »Yb> ic cone opening angle

Claims

claims

1. Spray head (1) for applying spray paints to the inner surfaces of one-sided open packaging, wherein

a) the spray head contains a distributor head (6) with at least two outlet openings (9) which are connected via channels (8) to a spray paint supply (5),

b) with the outlet openings (9) cone-like spray figures (3) can be generated, the predetermined minimum and maximum opening angles (γ) and a predetermined orientation of the spray cone axis (13), and

c) the spray head (1) can be used in a device for applying spray paints to the inner surface of packaging which is open on one side, there being a positioning axis (11) which is fixed relative to the spray head (1) and which is in the inserted state of the spray head parallel to the axis of rotation of the

Packaging lies,

characterized in that

d) at least two of the spray cone axes (13) are arranged convexly, that is, in one or both of them the point with shortest distance to the other spray cone axis in the spray direction behind the outlet opening.

2. Spray head according to claim 1, characterized in that at least two of the spray cone axes

(13) are arranged in two parallel planes, which have a distance (10) different from zero.

3. Spray head according to one of claims 1 to 2, characterized in that at least two outlet openings (9) and at least one spray cone axis (13) are arranged in one plane.

4. Spray head according to one of claims 1 to 3, characterized in that the spray figures (3) before and at the

Impingement on the inner surface of the packaging does not overlap spatially.

5. Spray head according to one of claims 1 to 4, characterized in that at least two spray cone axes are arranged convexly and they with the positioning axis (11) an angle of 10 to 18 °, preferably 13 °, or 50 to 70 °, vor¬ preferably 60 °.

6. Spray head according to one of claims 1 to 5, characterized in that at least two spray cone axes (13) are arranged convexly and form with the positioning axis (11) at an angle of 0 to -12 °, preferably -6 °, or 50 to 70 °, preferably 60 °.

7. Spray head according to one of claims 1 to 6, characterized in that at least two spray cone axes are arranged convexly and they with the positioning axis (11) at an angle of 15 to 25 °, preferably 20 °, or 50 to 70 °, preferably 60 °, form.

8. Spray head according to claim 2, characterized in that the distance (10) is 1 to 10 mm, preferably 2 to 5 mm, very particularly preferably 3 mm.

9. Spray head according to one of claims 1 to 8, characterized in that the spray figures have opening angles (γ) of 5 to 60 °.

10. Spray head according to claim 9, characterized in that the spray figures have opening angles (γ) of 5 to 45 °.

11. Spray head according to one of claims 1 to 10, characterized in that the outlet openings of the distributor head (6) are formed by nozzle inserts (9).

12. Spray head according to one of claims 1 to 11, which belong to the convex spray cone axes (13) belonging outlet openings (9) on the inner surface of a ball.

13.Device for applying spray paints to the inner surface of packaging that is open on one side, comprising (A) at least one arrangement for supplying packaging that is open on one side before a hydraulic or pneumatic spray head (B) a hydraulic or pneumatic spray head with a spray nozzle, one of which is a spray figure goes out, (C) electronic, mechanical, pneumatic and / or hydraulic arrangements for regulating the spraying conditions, (D) optionally arrangements for continuing the packaging coated on the inside in front of any further spray heads that may be present, (E) arrangements for guiding away the ones in their Inside, coated packaging from the spray head or spray heads and from the device, (F) at least one arrangement for rotating the packaging around its axis of rotation, characterized in that it contains at least one spray head according to one of claims 1 to 12.

14. Process for applying spray paints to the inner surface of one-sided open packaging, in which the packaging to be coated

1) is rotated about the axis of symmetry that passes through its opening in the packaging (axis of rotation),

2) with continued opening, its opening is guided in front of a hydraulic or pneumatic spray head which has a spray nozzle from which a spray figure emanates and which is located in front of the opening during the spraying process,

4) optionally further spray heads are fed, where process steps 1) to 3) are repeated, characterized in that at least one spray head according to one of claims 1 to 12 or a device according to claim 13 is used.

15. The method according to claim 14, characterized in that the positioning axis (11) of the spray head (1) is set fixed parallel to the axis of rotation (12).

16. The method according to any one of claims 14 or 15, characterized in that at least one spray cone axis (13) and the axis of rotation (12) lie in one plane.

17. The method according to any one of claims 14 to 16, characterized in that the first spray figure, the smallest from the spray nozzle

Distance to the opening of the packaging comes into contact with the inner surface immediately behind the opening of the packaging.

18. The method according to any one of claims 14 to 17, characterized in that the last spray figure, the largest from the spray nozzle

Distance to the opening of the packaging comes on the inside surface immediately in front of the packaging floor, the inside surface of the packaging floor or these two inside surfaces at the same time.

19. The method according to claim 14 to 18, characterized in that the last spray figure at the same time on the inner surface immediately before the Emballagenboden and on the inner surface of the Emballagen¬ floor.

20. The method according to claim 18 or 19, characterized in that the impact surface of the last spray cone covers 10 to 90% of the inner surface of the packaging base.

21. The method according to any one of claims 14 to 20, characterized gekenn¬ characterized in that the impact surfaces of all spray figures cover 10 to 90% of the entire inner surface of the packaging.

22. The method according to claim 14 to 21, characterized in that the spray cone axes (13) form angles between 5 and 70 °.

23. The method according to claim 22, characterized in that the spray cone axes (13) form angles between 10 and 45 °.

24. The method according to any one of claims 14 to 23, characterized gekenn¬ characterized in that the spray figures have opening angles (γ) of 5 to 60 °.

25. The method according to claim 24, characterized in that the spray figures have opening angles (γ) of 5 to 45 °.

26. The method according to any one of claims 14 to 25, characterized gekenn¬ characterized in that spray cone axes (13) form angles of 10 to 85, in particular 15 to 60 ° with the body and / or its escape line.

27. The method according to any one of claims 14 to 26, characterized gekenn¬ characterized in that the walls of the spray figures do not touch the edge of the Emballagen¬ opening.

28. The method according to any one of claims 14 to 27, characterized gekenn¬ characterized in that the volume of the first spray cone extends beyond the edge of the packaging opening.

29. The method according to any one of claims 14 to 28, characterized in that an inner coating is applied by means of the individual spray nozzles, which has the same or approximately the same thickness regardless of the location.

30. The method according to any one of claims 14 to 28, characterized in that an inner coating is applied by means of the individual spray nozzles, which has a different thickness depending on the location.

31. The method according to any one of claims 14 to 30, characterized gekenn¬ characterized in that an aqueous spray paint is used which, based on its total amount, has a solids content of more than 22% by weight, in particular more than 25% by weight .-%, Has.

32. The method according to claim 31, characterized in that the aqueous spray paint

(I) at least one water-soluble or water-dispersible binder which has acid groups, in particular carboxyl groups, and (II) at least one epoxy resin with more than one epoxy group per

Molecule.

33. The method according to claim 32, characterized in that the aqueous spray paint contains the components (I) and (II) in a ratio (I): (II) of 0.1 to 2.

34. The method according to claim 32 or 33, characterized in that at least one copolymer is used here as component (I), which by copolymerizing a mixture of, in each case based on the total amount of the mixture, (Ia) 10 to 45 wt .-% of at least one α, β-unsaturated carboxylic acid, in particular acrylic acid, methacrylic acid and / or

Itaconic acid, (lb) 10 to 35% by weight of at least one aromatic vinyl monomer, in particular styrene, 2-, 3- and / or 4-alkylstyrene and / or α-methylstyrene, (Ic) 20 to 80% by weight at least one alkyl and / or aryl ester of at least one ot, ß-unsaturated carboxylic acid (Ia) can be prepared.

35. The method according to any one of claims 14 to 30, characterized in that powder coating slurries are used here.

36. packaging with a coated inner surface, producible by the method according to any one of claims 14 to 35.

37. The packaging according to claim 36, characterized in that the hardened lacquer layer on its inner surface has a uniform or approximately uniform thickness of less than 15, preferably less than 10 and in particular less than 5 g / m ^.

38. The packaging according to claim 36, characterized in that the hardened lacquer layer has a different thickness depending on the location in the range of less than 15, preferably less than 10 and in particular less than 6 g / m ² .

39. The packaging according to claim 36, characterized in that the strength of the hardened lacquer in the area

(i) the neck formation of the packaging ("neck") less than 10 g / m ² ,

(ii) the packaging hull directly behind the "neck"("neckshadow") less than 8, in particular less than 6 g / m ² , (iii) the packaging hull less than 6, in particular less than 5 g / m ² ,

(iv) the inwardly bulging base ("dome") less than 8, in particular less than 6 g / m ² , and (v) the stand ring ("rim") integrated in the base of the rim less than 6, in particular less than 5 g / m ² .

40. The packaging according to one of claims 36 to 39, characterized gekenn¬ characterized in that it has a capacity of over 400 g.

41. Use of the packaging according to claim 40 for the packaging of food.