US20120201630A1

US20120201630A1 - Method of producing metal packages

Info

Publication number: US20120201630A1
Application number: US13/369,326
Authority: US
Inventors: Rainer Klenk
Original assignee: Individual
Current assignee: Huber Packaging Group GmbH
Priority date: 2009-08-12
Filing date: 2012-02-09
Publication date: 2012-08-09
Also published as: DE102009038129A1; WO2011018493A1; EP2464573A1; EP2464573B1

Abstract

A method for producing metal packages is disclosed, comprising the steps of forming a metal package, in particular from steel or aluminum, from a sheet metal material, in particular from thin or very thin sheet or tin plate, wherein the metal package comprises a cavity having inner surfaces that are coated with a paraffin-based coating material. The coating material is preferably heated after coating to a temperature above the solidifying temperature.

Description

CROSSREFERENCES TO RELATED APPLICATIONS

This application is a continuation of international patent application PCT/EP2010/061732, filed on Aug. 12, 2010 designating the U.S., which international patent application has been published in German language and claims priority from German patent application 10 2009 038 129.2, filed on Aug. 12, 2009. The entire contents of these applications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention relates to a method for producing metal packages from metal sheets with a coating and to metal packages of sheet material, in particular of thin or very thin sheet or tin plate, for receiving in an interior space a product with which they are filled.
Such metal packages are known in principle in the prior art and are sold by the applicant in various forms including those of flat-top drums, canisters, seamed-lid cans, hobbocks and barrels.
Such metal packages are used for packaging and storing chemical/technical products, foodstuffs and, in particular, beverages. They are produced by means of methods that are generally known in the prior art, including separating and reforming processes. Connections are thereby created by various operations including that of seaming, with previously flanged edge regions of metal sheets being connected to one another by folding them over.
The known metal packages make it possible for the aforementioned products with which they are filled to be received in a mechanically stable container in such a way that they are protected from light and sealed. The sealing extends here to liquid, gaseous and gas-tight constituents of the products, and similarly undesired permeation through the packaging material is avoided. In addition, such containers are suitable for receiving pressurized products. Metal packages are almost completely recyclable, it being possible to obtain a virtually closed material cycle for the packaging materials if they are consistently recovered and reused.
To ensure that the containers are resistant to corrosion, acid and general media, it is necessary to provide their surfaces, in particular also the inner sides, with a protective coating. This coating may be, for example, a combination of a metallic layer, for example a tin coating in the case of tin sheet, and an organic coating applied on top, such as for example a lacquering or an applied film. Such coatings are generally applied before the reforming operation to the semifinished product, flat material, plate material or metal strip.
It has been found that the operations for reforming the starting material that follow in the course of the production of the metal package, such as for example drawing, flanging or seaming operations, can impair the protective effect of a lacquer layer particularly. For this reason there has been a change in the practice employed, to alternatively or additionally coating the interior space of a completed or semifinished metal package with lacquers by an internal spraying method. However, it must be noted here that the internal spraying method does not allow the lacquer layer to be applied to all the component parts of the package, such as for example in the case of interior spaces in a package with areas that are difficult to access or with very small filling openings.
In the course of the subsequent application of lacquers, it is necessary for the coating to be followed by a drying operation. This involves the lacquer layer being dried or baked at a greatly increased temperature, for instance at 180 to 200° C., which is applied for a considerable time period, for example approximately 12 minutes. This high thermal loading necessarily requires more complex equipment and greater expenditure on the supply of energy and the disposal of emissions, such as for example of degasifying and evaporating matter. Furthermore, such treatment may cause the risk of a coating, printing or lacquering of the outer side of the package being damaged.

SUMMARY OF THE INVENTION

In view of this, it is a first object of the invention to disclose a method of producing metal packages allowing for improved corrosion protection.
It is a second object of the invention to disclose a method of producing metal packages that renders possible a relatively simple production.
It is a third object of the invention to disclose a metal package that has increased corrosion protection.
According to one aspect these or other objects are solved by a method comprising the steps of:

- providing a metal package made of sheet metal and having a cavity formed by inner surfaces;

providing a paraffin-based coating material;
heating said coating material to a temperature above a solidifying temperature thereof;
applying said coating material onto said inner surfaces of said cavity;
solidifying said coating material; and
cooling said metal package to room temperature.
With respect to a material package of the type mentioned at the outset, the object of the invention is achieved in that at least the interior space of the package has a surface coating comprising a paraffin-based coating agent.
The object of the invention is completely achieved in this way.
This is so because, according to the invention, a metal package is formed and then its interior space is coated with a paraffin-based coating agent, so as to obtain an organic coating which ensures excellent corrosion protection and is not subjected to any subsequent mechanical deformation or damage caused by reforming processes in the production of the metal package. In this way, a high integrity of the coating can be ensured.
One particular advantage of the solution according to the invention is that a greatly reduced porosity is achieved in comparison with spray lacquered coatings. Consequently, corrosion currents can in principle be minimized or prevented, which leads to much improved corrosion protection. Accordingly, it may also be possible for a package according to the invention to be successfully filled with aggressive products, which for instance contain acids or lyes.
Paraffinic hydrocarbons are non-toxic and are not considered to be a health hazard, and so they can certainly come into consideration for use in packages for foodstuffs or beverages. In addition, on account of their non-reactivity, paraffins are outstandingly suitable as corrosion protection agents; they are, in particular, not water-soluble and are very resistant to many kinds of acids. Consequently, they are particularly suitable for use in metal packages for carbonated beverages, such as for example beer or cola.
For the purposes of this application, the paraffin-based coating agent should be understood as meaning a substantially paraffin-containing coating agent which advantageously consists of paraffin to over 75%, preferably to over 85% and more preferably to over 95%. The coating agent may be supplemented by adding fillers, solvents, dyes, binders and other additional substances, for example fats and natural or synthetic waxes, or else by additions of production-related residual constituents, such as for example oil residues.
It is conceivable for the coating agent to consist completely or almost completely of paraffin. In this way it can be ensured that no, or only insignificant, constituents of the coating agent are released after coating by degassing or dissolving.
It should be noted in this connection that paraffins should be understood as meaning substantially paraffinic hydrocarbons, which generally have a low reaction tendency. Paraffins may be composed of unbranched (n-) and branched (iso-) alkanes, the reason for their advantageous properties. Paraffinic hydrocarbons are substantially wax-like, odorless and tasteless, electrically nonconducting and hydrophobic.
Depending on their chain structure, paraffins may be classified according to their viscosity and their solidifying temperature. This application is primarily, but not exclusively, intended to focus on mixtures with particularly long-chain hydrocarbons. Furthermore, paraffins should also be understood as including what are known as micro waxes.
According to a development of the invention, the coating agent is applied under pressure, in particular by the airless spraying method.
In this way it is made possible to apply the coating agent by means of known techniques. A uniform initial coating is obtained. The airless spraying method is particularly suitable for applying the coating agent, since, by contrast with air-pressure-based spraying methods, the coating agent is applied here without an additional carrier medium. This allows contamination of the metal package or the coating agent with constituents of the process air that occur in a method with compressed air to be avoided. Similarly, there is no need for laborious preparation, cleaning or filtering of the process air. In an alternative refinement of the invention, the coating agent is applied by means of a pouring or sprinkling method.
This measure allows the coating agent to be applied without pressure. Consequently, the complexity of the production and equipment is reduced. It is also possible here to dispense with the use of process air for applying the coating agent, so that contamination of the metal package and of the coating agent can be reduced, thereby increasing the quality of production and the reliability of the process.
Applying the coating agent by gravitational force by means of pouring or sprinkling methods can similarly ensure influencing of the layer thickness to be achieved. By variation of various parameters, such as for example the viscosity of the coating agent, the temperature of the coating agent or of the metal package to be coated or else the surface finish of the interior space of the metal package, a desired layer thickness can be set.
In an advantageous development of the invention, for coating, the coating agent is heated to a temperature above the solidifying temperature.
This measure makes it possible to process paraffin-based coating agents without the addition of solvents. In this way, only local areas of the production plant have to be heated, thus promoting rapid adhering and solidifying of the coating agent on the metal package not heated by the plant. It is conceivable to heat the coating agent directly in a storage container or reservoir or else to achieve the introduction of heat into the coating agent indirectly by heating up parts of the coating device.
In a preferred development of the invention, the coating agent has a solidifying temperature of over 70° C., preferably of over 85° C., more preferably of over 90° C.
Such high solidifying temperatures can be advantageously achieved with micro waxes. In this way, a sufficiently high thermal stability of the applied coating for the further processing, filling with the product and later use can be ensured.
Furthermore, the solidifying temperatures are still chosen low enough to keep down the energy requirement for heating the coating agent, and consequently restrict the complexity of the production and the production plants. Furthermore, protection of the outer surface of the metal package from high thermal loads is ensured. This allows a lacquering, printing or coating that is applied to the outside of the container to be applied already before the sheet-reforming operation, on the flat semifinished product, without being damaged by such thermal loads.
It is particularly preferred to heat the coating agent after coating once again to a temperature above the solidifying temperature.
In this way, the applied, already partially or completely solidified coating agent can be partly or fully melted in order to wet the interior space of the metal container completely with the again liquefied or viscous paraffin. This allows wetting of even inaccessible areas in which initial application of the coating agent could not take place. In addition, the integrity and homogeneity of the coating agent and the surface of the coating agent can be improved, since the liquid or viscous coating agent is capable of filling or healing microcracks on its surface or gaps in the application.
For this purpose, the applied coating agent is preferably brought to a temperature of approximately 100° C. and kept at this temperature for approximately two to three minutes. This can greatly simplify the production process and improve the corrosion protection, since possible defects and cracks in the initial layer can be closed or healed in a dependable way by a subsequent production step.
In an advantageous development of the invention, during the forming of the metal package there is formed at least one folded seam connection, which is coated with the coating agent during the subsequent coating of the interior space.
In this way it has been made possible to use reforming and joining processes that are simple, inexpensive and suitable for mass production to form the metal package, since it can be ensured by the coating with a paraffin-based coating agent that even areas that are particularly difficult to access, such as for example seaming channels, can be covered with the coating agent.
In an advantageous development of the invention, for applying or reheating the coating agent, the metal package is arranged such that it is aligned so as to completely wet the interior space with the coating agent.
Consequently, with suitable alignment, the applied liquid or viscous coating agent can, under the influence of gravitational force, penetrate of its own accord into areas of the metal package that are difficult to access, such as for example folded seam connections, in order to ensure complete coating of the interior space. It is conceivable to align the metal package a number of times during production, and in this way further increase the reliability of the process in terms of the coating operation, and similarly thereby allow areas that are particularly difficult to access to be wetted with the coating agent.
For example, in the course of alignment the metal package may be turned by 180 degrees, in order after complete covering of the bottom area of the metal package to then cover the area opposite that dependably with the coating agent. When doing so, any opening there may be in the lid may be suitably closed. It is alternatively conceivable in the course of the coating process to allow excess coating agent to run out of the metal package simply under the effect of gravitational force after it has been suitably aligned.
In a preferred development of the invention, when applying or re-heating the coating agent, the metal package is pivoted so as to completely wet the interior space with the partly or fully melted coating agent.
By means of a continuous pivoting movement, it can be achieved in this way that the coating agent is applied particularly dependably and quickly to the entire interior space of the metal package.
The pivoting movement may take place already during the initial application of the coating agent, but similarly in the course of possible subsequent follow-up steps of heating the applied coating.
According to a development of the invention, the coating agent is mixed with a solvent for paraffin.
This can bring about the effect that the viscosity of the coating agent and the processing temperature for applying the coating agent are lowered. This allows energy savings to be achieved, since the coating agent does not first have to be brought to a higher processing temperature. Furthermore, by adding solvents to the coating agent, further process-relevant properties can be suitably influenced. It is conceivable for the creep of the coating agent or the adhesion on the specific sheet material to be improved.
It goes without saying that non-toxic and unharmful solvents should preferably be used. It is alternatively conceivable for it to be possible to use other solvents that have an outstanding dissolving effect in the case of paraffins, such as for example benzene, ether and chloroform. It also goes without saying that the solvents should escape completely after application, after which the coating agent can have the advantageous properties of almost pure or completely pure paraffin.
It should be noted in this connection that the proportion of paraffin in the coating agent may be altered by constituents undergoing degassing or other releasing processes, in any event may be greater after the production of the metal package than before the application of the coating agent.
It goes without saying that the features of the invention mentioned above and still to be explained below can be used not only in the respectively specified combination but also in other combinations or on their own without departing from the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention emerge from the following description of a number of preferred exemplary embodiments with reference to the drawings, in which:

FIG. 1 shows a perspective representation of a partially cut-open metal package according to the invention in the form of a barrel;

FIG. 2 shows a perspective view of a further metal package according to the invention in the form of a can;

FIG. 3 shows a perspective representation of a further metal package according to the invention in the form of a canister;

FIG. 4 shows a section through a metal package according to the invention with a seamed lid;

FIG. 5 shows a schematic representation of an installation for coating the interior space of a metal package using the method according to the invention;

FIG. 6 shows a view of a nozzle for use in the method according to the invention;

FIG. 7 shows a partial section of an embodiment of a nozzle that has been modified in comparison with FIG. 6;

FIG. 8 shows a schematic partial view of an embodiment of an installation for coating a metal container that has been modified in comparison with FIG. 5;

FIG. 9 shows an enlarged partial section through a metal package according to the invention in the area of a folded seam connection with an applied coating agent;

FIG. 10 shows a view according to FIG. 9 with an interior space of the metal container that has been completely wetted by a partly or completely melted coating agent; and

FIG. 11 shows a schematic representation of a pivoting device for pivoting or aligning a metal container according to the invention when carrying out the method according to the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In FIG. 1, a metal package according to the invention in the form of a barrel is represented and denoted as a whole by 10.
Such metal packages are widely used for packaging and storing chemical or technical products or else foodstuffs, in particular beverages. Packages of such a design have found widespread use as beer barrels. In general, such beer barrels have a filling volume from approximately three to approximately twenty liters, barrels known as 5-liter party barrels having become established as a common container size. However, barrels with a filling volume from just a few liters to several hundred liters are offered primarily for wholesale demand and for chemical or technical products.
Metal packages of such a design are usually formed from thin or very thin metal sheets. Usually, very thin sheets have thicknesses of less than 0.5 millimeter, while thin sheets cover approximately the thickness range from 0.5 to 3 millimeters. Materials and semifinished products for producing such metal packages are flat strips, plates and coils of tin plate, non-tin plate or else special electrolytically chrome-coated steel sheet.
The metal package 10 shown in FIG. 1 is fashioned from the flat material by various re-forming and joining operations. The metal package 10 has a shell element 15, which surrounds an interior space 12 and is connected in its lower area to a bottom element 11 and in its upper area to a lid element 13 by means of folded seam connections 17. The lid element 13 has a filling opening 16, for example for filling with beer. The bottom element 11 and the lid element 13 may be formed, for example, from pre-punched round blanks. The shell element 15 is formed from flat strip, the cylindrical form being produced by bending over and joining two ends of the substantially rectangular starting material by means of a folded seam connection (not represented). It is alternatively conceivable to form the shell element 15 from a tubular semifinished product.
A metal package according to the invention may well have in addition to the filling opening 16 further openings, such as for example for integrating a tap cock or for aerating or venting.
In the course of shaping such a container, many separating, joining or reforming processes may be used, such as in particular punching, cutting, expanding, flanging, seaming, welding or beading.
It should be noted in this connection that the term “metal package” must not be understood as implying that the finished package or the filled container does not have any non-metal component parts. It is normal and conceivable to provide plastic-based closures, valves or transporting aids, such as handles or edge protectors, and so “metal package” should not be understood restrictively in this respect.
FIG. 2 shows a further metal package 10 a according to the invention. By contrast with the metal package 10 that is represented in FIG. 1, the metal package 10 a in FIG. 2 is represented in a one-part state. The shell element 15 may be formed by expanding or deep-drawing a flat or preformed semifinished product. The form of container that is shown in FIG. 2 usually serves for receiving carbonated beverages, in particular beer or cola, but is also used for filling with other products. Such packages, known in the form of beverage cans, may be made of the aforementioned steel sheets, alternatively of aluminum sheets, but also of a combination of metal material. Widely used filling capacities are for instance 0.2, 0.25, 0.33, 0.5, 0.75, 1.0 and 1.5 liters.
The usual form of a beer or cola can with a metal single-use closure gives rise to a special technical feature in terms of production or filling; that is that a lid element (not represented in FIG. 2) is only connected to the shell element 15 after the product has been introduced through the filling element 15 of the metal package 10 a.
A further modified embodiment of a metal package according to the invention is shown in FIG. 3 and is denoted by 10 b. The metal package 10 b in the form of a canister may serve for receiving liquid chemical products, such as for example paint or varnishes, but also for storing free-flowing granules or powder. In the foodstuffs sector, such containers are used for applications including the storing of edible oil.
In a configuration given by way of example, the metal package 10 b has a shell element 15, which also bounds the bottom area of the metal package 10 b, so that all that is additionally provided is a lid element 13, which is connected to the shell element 15 by way of a folded seam connection 17. In an alternative refinement, such a canister may also have an additional folded seam connection for receiving a bottom element, for instance by analogy with FIG. 1.
In FIG. 4, a further metal package 10 c is represented. The sectional view clearly shows the configuration of the folded seam connection 17 for connecting the lid element 13 to the shell element 15. It is immediately evident that, to fashion such a folded seam connection in the case of the shell element 15 and the lid element 13, flanging or seaming operations must be performed, whereby the individual metal sheets are subjected to high degrees of re-forming in these areas.
It should once again be pointed out that it is known in the prior art to provide the sheets that are used with coatings, such as for example decorative lacquerings or printings or corrosion protection agents, either in the flat state before the re-forming or else in the re-formed or joined state. In the areas of the sheets that have high degrees of re-forming, these coatings may be weakened or damaged by these operations if they are applied before the re-forming or joining.
This disadvantage can be obviated by alternative or additional coating of the metal package, in particular of the interior space of the metal package, after the reforming and joining, although this increases the complexity of the production and may give rise to other disadvantages. For example, it is known that with the drying of a coating or lacquering applied to the interior space 12 of the metal package 10 c, which in the case of conventional lacquers is performed at high temperatures of approximately 180 to 200° C., a decorative lacquering applied on the outer side 18 of the metal package 10 c may be impaired or damaged by discolorations or the like.
Alternatively, by omitting this additional inner coating, a reduced corrosion protection would have to be accepted in the interior space 12 of the metal container 10 c, and there in particular in the area in which individual elements come together to form a folded seam connection.
To avoid such disadvantages, it is thus proposed according to the invention to apply a coating with a paraffin-based coating agent in the interior space of a metal package.
FIG. 5 shows a schematic representation of an installation for carrying out the method according to the invention.
A metal package 10, represented in a simplified state and formed for instance according to FIGS. 1 to 4 is arranged in relation to a coating device denoted by 20. Here it is conceivable for the feeding movement and further possible relative movements of the metal package 10 with respect to the coating device 20 to be produced by a handling device that is schematically represented in FIG. 5 and denoted as a whole by 40. The handling device may have lifting means or turning means, as indicated by the arrows 46 and 44, respectively, in order to move the metal package 10 in relation to a nozzle part 24.
Alternatively, it is conceivable to move the coating device 20, or at least a feeding means 22 assigned thereto and having the nozzle part 24, in relation to the metal package, which will be explained in more detail later with reference to FIG. 8.
The feeding element 22 serves for supplying the nozzle 24 with the coating agent 30. Provided for this purpose are lines 28, configured in FIG. 5 by way of example as a ring line. It goes without saying that the feeding element 22 may have a valve suitable for controlling the coating operation (not represented). The line 28 connects a container means 34, which serves for receiving a supply of the coating agent 30, to the nozzle part 24, it being possible for excess coating agent that is not applied to be introduced once again into the container means by way of a return. A pump 35 in the line 28 serves for generating the pressure for applying the coating agent 30.
Before being applied, the coating agent 30 is advantageously heated or liquefied by means of heating devices 32 or 32 a. The heating device 32 may serve for heating the coating agent 30 when it flows through the line 28. Additionally shown is a heating device 32 a, which serves the purpose of heating the coating agent 30 located in the container means 34, so that the target temperature of the coating agent 30 can alternatively be ensured by permanent circulation in the line 28 by means of the pump 35.
In FIGS. 6 and 7, design developments of the feeding means 22 are represented. Here, the nozzle part 24 a in FIG. 6 has a spherical shape, thereby ensuring that virtually the entire space surrounding the nozzle part 24 a can be wetted with a coating agent.
On the other hand, in FIG. 7 the nozzle part 24 b is additionally provided with a joint 26, which makes it possible for the nozzle part 24 b to be additionally pivoted, in order to be able to coat areas of a metal package that are difficult to access.
According to the arrangement in FIG. 5, it is sufficient to move the metal package 10 in an axis 46 in relation to the nozzle part 24 in order to be able to achieve complete wetting of the interior space 12 of the metal package 10. A rotation 44 may be additionally introduced in order to bring about a uniform distribution of the coating agent 30 over the circumference of the interior space 12 of the metal package 10.
By contrast with this, schematically represented in FIG. 8 is a metal package 10 which has only a relatively small filling opening 16. This may make it more difficult in particular to coat corner areas of the interior space 12 of the metal package 10. This is so particularly when a directed nozzle part 24 is used, for instance a nozzle with an emission angle of only 90 degrees or 180 degrees.
To overcome such disadvantages, in FIG. 8 there is provided an alternative handling device 40 a, which serves for advancing a feeding means 22 a with the nozzle part 24 into the interior space 12 of the metal package 10. The handling device 40 a may have lifting means or turning means, as indicated by the arrows 46 a and 44 a, respectively. In this way, the feeding means 22 a can be introduced into the interior space 12 and also moved there. For the fine alignment of the nozzle part 34, further joints 26 a, 26 b are provided. By combining the handling device 40 a with the feeding means 22 a it is thus possible to wet almost the entire interior space 12 of the metal package 10.
A particularly advantageous method step is then illustrated in FIGS. 9 and 10.
An area of a folded seam connection 17 between a bottom element 11 and a shell element 15 of a metal package is respectively shown in section in these figures. This detail may be representative of areas of further folded seam connections, more generally of areas of a metal package that are difficult to access. These may also be, in particular, lid seams or lateral vertical seams and any areas that are not wetted in the course of the initial coating.
The initially applied coating agent 30′ is shown in FIG. 9. It can be seen here that the area in which the shell element 15 and the bottom element 11 come together to go into a folded seam connection, known as a seaming channel 19, is possibly not covered completely by the coating agent on account of its narrowness and depth. However, the coating agent 30′ according to the invention can be partly or fully melted particularly easily at relatively low temperatures by suitably supplying heat, indicated by 38. For this purpose, a melting device 36 is thus used for generating the heat input 38. The heat input 38 may advantageously take place by way of convection, heat conduction and by way of radiation into or around the metal package, for example by means of circulation of heated air or else by infrared radiation, in particular near infrared radiation. It is particularly advantageous in terms of production to make the coating agent 30′ that is to be heated melt partly or fully indirectly by heating metal sheet material 14 in the shell element 15 or the bottom element 11.
It should especially be mentioned in this connection that the temperatures thereby occurring on the outer side of the metal package are much lower than the temperatures during the drying of conventional lacquers on the inner side of the metal package. This dependably avoids instances of damage, such as for example deviations in color, of the coating of the outer side of the package.
FIG. 10 then illustrates the desired state aimed for, in which the coating agent then denoted by 30″ has penetrated of its own accord into the seaming channel 19 and completely wetted it. Dependable corrosion protection and later separation of the product from the sheet metal material 14 of the metal package 10 is consequently also ensured in this area. The partly or fully melted coating agent 30″ is sufficiently viscous to ensure that, in spite of running of its own accord under the effect of gravitational force, areas once wetted are not exposed again.
This particularly preferred method step is also suitable in particular for dependably coating inaccessible areas on outer sides of metal packages. These may be, for example, pronounced depressions, beads or outer seam geometries. As is known, metal containers tend to corrode specifically in such areas.
In order to assist penetration of the coating agent into areas of the interior space of the metal package that are difficult to access, or make it possible in the first place, it is particularly advantageous to align or pivot the metal package suitably, so that the entire interior area can also actually be wetted by means of gravitationally induced flowing.
FIG. 11 schematically shows a pivoting device suitable for this, which is denoted as a whole by 42. The pivoting device 42 is provided with various pivoting or turning axes 52, 54, 56 and 58. Also provided are gripping means 50, to allow the metal package 10 to be gripped and held. By means of the pivoting device 42, the metal package 10 can then be suitably aligned or pivoted in order to direct or help the flowing of the coating agent. This pivoting or aligning may be performed both discretely and continuously. It is thus conceivable to move the metal package 10 already during the heating of the applied coating agent in such a suitable way as to keep the process time short.
As an example of discrete alignment of a metal package 10, it is conceivable to heat a container, for instance according to FIG. 1, after the initial application of coating agent in a position in which the bottom element 11 is on the ground, so that the coating agent can penetrate of its own accord into the seaming channel of the folded seam connection 17 between the bottom element 11 and the shell element 15. After that, the metal package 10 may simply be turned by 180 degrees, so that the coating agent 30, which is still in the partly or fully melted state, or is brought once again into this state by re-heating, can also penetrate into the seaming channel between the lid element 13 and the shell element 15. When doing so, the inlet opening 16 may be suitably closed, in order to avoid flowing out of the molten coating agent 30.
It is similarly conceivable to introduce a greater amount of coating agent into a metal package, deliberately allow it to flow around in the interior space of the metal package and subsequently pour out of the metal package an excess amount of the coating agent that is not required.
It goes without saying that the handling, pivoting and feeding devices shown can be suitably combined, reduced and simplified in order to make the plant for carrying out the method according to the invention as simple and inexpensive as possible and allow it to be integrated in the established production sequence in the production of metal containers.
It has been accomplished within the scope of the invention to provide a particularly simple and effective method for producing metal packages in which, in particular, corrosion protection in the interior space of the metal packages is ensured to an improved extent with at the same time less complex production and at the same time improved production quality.
A metal package according to the invention accordingly ensures high corrosion protection along with a simplified way in which it can be produced, particularly also meeting the requirements for suitability for food contact applications.

Claims

1. A method of producing a metal package, comprising the steps of:

providing a metal package made of sheet metal and having a cavity formed by inner surfaces;

providing a paraffin-based coating material;

heating said coating material to a temperature above a solidifying temperature thereof;

applying said coating material under pressure by airless spraying onto said inner surfaces of said cavity;

solidifying said coating material;

re-heating said metal package to a temperature above said solidifying temperature of said coating material; and

cooling said metal package to room temperature;

wherein said metal package is pivoted at least during said step of applying said coating material or said step of re-heating said metal package.

2. The method of claim 1, wherein said paraffin-based coating material comprises at least 85% of paraffin.

3. The method of claim 1, wherein said paraffin-based coating material comprises at least 95% of paraffin.

4. The method of claim 1, wherein said metal package is made from a material selected from the group consisting of steel sheet metal and tin plate metal.

5. The method of claim 1, wherein said container after said application step is turned upside down for pouring out excess coating material by gravity assistance.

6. The method of claim 1, wherein a coating material is used having a solidifying temperature of more than 90° C.

7. The method of claim 1, wherein said step of providing a metal package further comprises at least one seaming step for forming a folded seam connection, wherein said folded seam connection is completely coated with said coating material during a subsequent step of applying said coating material onto said inner surfaces of said cavity.

8. The method of claim 1, wherein said inner surfaces of said cavity are fully wetted at least during one step selected form said step of applying said coating material and said step of re-heating said coating material.

9. The method of any of claim 1, wherein said coating material, before being applied onto said inner surfaces of said cavity, is mixed with a solvent for paraffin.

10. A method of producing a metal package, comprising the steps of:

providing a paraffin-based coating material;

applying said coating material onto said inner surfaces of said cavity;

solidifying said coating material; and

cooling said metal package to room temperature.

11. The method of claim 10, wherein said coating material is applied under pressure.

12. The method of claim 11, wherein said coating material is applied by an airless spraying method.

13. The method of claim 10, wherein said coating material is applied by means of pouring or sprinkling.

14. The method of claim 10, further comprising the step of pivoting said metal package during said step of applying said coating material.

15. The method of claim 10, further comprising the step of pivoting said metal package during said step of re-heating said coating material.

16. The method of claim 10, wherein said step of providing a metal package further comprises at least one seaming step for forming a folded seam connection, wherein said folded seam connection is coated with said coating material during a subsequent step of applying said coating material onto said inner surfaces of said cavity.

17. The method of any of claim 10, wherein said coating material is mixed with a solvent for paraffin.

18. The method of claim 10, wherein said container after said application step is turned upside down for pouring out excess coating material by gravity assistance.

19. A metal package of a sheet metal material comprising a cavity having inner surfaces which are completely covered by a paraffin-based coating material.

20. The metal package of claim 19, in which said inner surfaces comprise a shell element and at least one bottom or lid element, wherein at least said bottom element or lid element is connected to said shell element by a folded seam connection which is covered by said paraffin-based coating material.