EP0118756B2 - Process for coating hollow tins - Google Patents

Abstract

In order to coat hollow bodies, which are open at one end, such as a metal can provided with a bottom, with a lacquer or the like, the hollow bodies are passed in a continuous operating cycle through en electrophoretic immersion bath in such a way, that they are rapidly and completely flooded with immersion bath liquid, so that they can be coated electrophoretically with a wet film in the immersion bath. After a sufficiently long coating time, the hollow bodies are lifted out of the immersion bath and the immersion bath liquid, contained in them, is poured out. The hollow bodies, so coated, are carried at a distance from each other to a drying kiln, in which they are dried, whereupon they can be printed or labelled.

Description

The invention relates to a method for coating cans which are open on one side, such as a metallic cans provided with a bottom, with lacquer, in which the individual cans are washed on the outside and coated and dried and then, if appropriate, printed and dried again and also flared at the open end.

The increasingly stringent requirements of environmental protection lead to considerations of what the electrocoating process is also called electrocoating (EC), for which the can manufacturer industry can be introduced as a fully automatic painting process. It is known to paint can bodies for three-part cans or also to coat a weld seam by immersing them in an electrodeposition bath (US Pat. No. 3,694,336, DE-OS 21 16 715). The can bodies are easy to handle because they do not yet have a bottom and the bath liquid for coating can enter easily and can also run out again after coating.

US Pat. No. 3,253,943 describes a device for coating bottles which is held at the bottle neck and introduced into and removed from a coating bath on a pitch circle, so that the bath liquid is emptied downwards after being removed. The coated bottles are then fed into a drying oven on an endless conveyor belt. US Pat. No. 3,391,073 describes an anodizing device in which cups attached to an endless belt pass through an anodizing bath on a partial circular path. Cans which are open on one side, such as cans provided with a bottom, cannot simply be coated electrophoretically, because it is necessary for a uniform coating that the air in the hollow body escapes completely. Therefore, the mechanical engineering industry has developed special methods that are carried out step by step, i.e. it is painted in individual successive steps, for example first on the inside. The constructions known for this have some things in common. In this way, the cans for the interior painting are held on the floor and at the same time the necessary electrical contacts are made. A counterelectrode is built into the open end of the can, which must have a small distance of 0.25 to 5 mm from the inner wall of the can. The shape of the electrode must therefore be adapted very precisely to that of the box. Because of the complicated structure of the corresponding system, the cans have to be coated individually one after the other, so that only short coating times of 10 to 500 msec are available if one wants to achieve a high can throughput. In the case of a closed system in, for example, a vertical arrangement (EP 50 045, EP 19 669, GB-PS 1 117 831, US-PS 3 922 213 and DE-OS 29 29 570), liquid must be pumped at high speeds in order to alternate EC liquid and to be able to flush the water in short periods of time and to discharge the gases generated during the EC coating (depending on the polarity, oxygen or hydrogen). In the open system, the approximately horizontally arranged cans must be rotated in order to achieve a uniform coating (DE-PS 26 33 179 and US-PS 4 107 016). When blowing out the cans, there is a great risk of contamination.

The disadvantage of all these known constructions is that the cans have to be coated individually one after the other with a high mechanical outlay. The large space requirement of the plant makes economic mass production almost impossible. Inner electrodes can only be inserted precisely in cans with straight, smooth walls, i.e. Can shapes deviating from the cylindrical shape lead to great difficulties. Because of the small distance between the inner electrode and the can wall, there is a risk of short circuits and electrical breakdowns in very high current density zones. Accordingly, lacquers must be used which, with suitable electrical voltages, enable a trouble-free coating in the short times available.

The object of the invention is to simplify the electrophoretic coating of cans which are open on one side, such as metal cans provided with a base, in such a way that coating can be carried out both externally and internally in one continuous operation.

This object is achieved by the process according to the invention for the electrophoretic coating of metal cans which are open on one side and subsequent drying, which is characterized in that each can is passed through an electrophoretic immersion bath and in the process from 3 to 60 seconds with one on it Surface-depositing wet film is coated, which has an electrical sheet resistance of at least 0.6 x 10 ⁸ ohm x cm, being immersed in a continuous operation with its opening pointing obliquely downwards in the immersion bath, immersed in the bath in such a way that its The opening points upwards, and then with its opening pointing downwards it is lifted out of the bath and then guided with an endless means of transport through one or more drying ovens, several cans being coated and dried at the same time next to one another and at a mutual distance from one another and one at e in a transport element provided holder for the individual cans is electrically switched as an electrode for electrophoretic coating, while in the individual cans retractable hill counter electrodes are used, which are at a distance greater than half the radius of the cans from the inner wall of the cans.

Advantageous embodiments of the invention are the subject of the dependent claims.

The invention makes it possible to coat cans which are open on one side, such as metal cans provided with a bottom, in one operation at the same time on the outside and on the inside, and to dry them immediately afterwards and, if appropriate, to print or label them. The mechanical effort and space requirements are relatively low, so that an economical mode of operation is possible. For example, 16 cans at the same time, i.e. passed side by side through an electro-dip bath and thereby coated with lacquer. When passing through the immersion bath, the cans are tilted by the transport elements holding them by at least 90 °, so that they first dip into the bath with a longitudinal axis inclined up to 45 ° to the bath surface, in which they are tilted so that their longitudinal axis is now in the opposite direction runs obliquely so that the opening now points upwards. To lift the cans out of the immersion bath, they are tilted again so that the opening is at the bottom so that the liquid in the cans can run off completely. Tipping can take place in the bathroom while it is being lifted out of the bathroom.

The transport element can be an endless conveyor belt or an endless chain on which the cans are rotatably suspended and which is guided through the EC immersion bath. Wheels or rollers are also suitable as transport elements which continuously guide the cans to be coated through an aqueous immersion bath.

Since the cans for coating are passed through an immersion bath and it is also possible to pass several cans next to one another simultaneously through the immersion bath, sufficiently long coating times can be achieved even with mass production with high throughput in order to be able to apply flawless lacquer coatings. With a coating time of more than 3 to less than 60 seconds, a pigmented or unpigmented lacquer is applied electroproretically by means of direct current, the wet film deposited on the cans having a sheet resistance of at least 0.6 x 10 ⁸ ohm x cm.

The cans to be coated are switched via the holding device when using an anionic EC lacquer as an anode and when using a cationic EC lacquer as a cathode. The counter electrode is located at the necessary distance from the can surfaces in the immersion bath. The inside and outside coating is carried out with the help of the so-called throwing power, which the paint achieves because of its high possible insulating effect in the deposited wet film. Before the inner coating starts, all air in the cans must escape from the interior.

In order to achieve the highest possible wrap, a number of factors must be taken into account when developing the paint. The electrophoretic coating is such that the wall of the can opposite the counter electrode is coated first. The deposition time and the insulating effect of the material, characterized by the sheet resistance and easy coagulation, must be coordinated in order to achieve a good grip. The lower limit of the coating time is over 3 seconds, in particular over 5 seconds and particularly suitably over 10 seconds. The upper limit is determined by the length of the immersion bath, the transport speed and the amount of cans to be coated to be handled. In order to achieve an economically acceptable level, the upper limit is less than 60 seconds and preferably less than 30 seconds of coating time. The amount of film applied depends on the deposition voltage, which is between 50 and 400 volts, preferably between 100 and 300 volts. With increasing tension, the wrap is improved. In order to avoid electrical breakdowns, the voltage is either continuously increased or gradually with a low or several increasing bias voltages. For example, before the actual coating, voltages of less than 100 volts are used for 0.1 to 0.5 seconds.

In principle, the wet film resistance required for good insulation should be as high as possible. However, its lower limit is limited by the desired short coating time. For example, the lower limit should be at least 0.6 x 10 ⁸ ohm x cm, expediently above 1 x 10 ⁸ and preferably above 2 x 10 ⁸ ohm x cm. The higher the layer resistance, the thinner the layer that can be reached on the can wall. The upper limit is therefore below 10 × 10 ⁸ ohm × cm, expediently below 7 × 10 ⁸ ohm × cm and preferably below 4 × 10 ⁸ ohm × cm. In order to provide the necessary amount of electrical current for the ectrophoretic deposition analogous to Faraday's laws, it is necessary that the bath conductivity, which is determined by the degree of neutralization of the binder, is above 600gScm- ¹ , suitably above 800 / gScm ^l and preferably above 1200f..lScm -1 lies.

Both anionic and cationic resins can be used as binders, the anionic for acidic and the cationic for basic fillers being preferred. The anionic resins such as maleinized or acrylated butadienols, maleinized natural oils, carboxyl group-containing epoxy resin esters and acrylate resins, acrylic epoxy resins unmodified or modified with fatty acids, have an acid number of 30 to 180, in particular between 40 and 80, and are mixed with ammonia, amines or aminoal alcohols at least partially neutralized. Highly volatile amines are preferred so that they are removed as completely as possible from the film with the desired short stoving times of 10 seconds to 300 seconds. Ammonia is particularly preferred.

The crosslinking takes place either oxidatively via unsaturated double bonds or by thermal reaction with corresponding crosslinking agents such as phenolic resins, amine-formaldehyde resins or blocked polyisocyanates. External or self-crosslinking acrylate resins are preferred for the production of white lacquer coatings. For coating with clear lacquers, externally or self-crosslinking acrylate resins, acrylated or maleinized epoxy esters or epoxy acrylates are preferred.

The cationic resins such as butadienol-aminoalkylimide Mannich bases of phenol resins, amino group-containing acrylate resins or amino-epoxy resins have an amine number of 30 to 120 mg KOH / g solid resin, preferably before 50 to 90 and are combined with organic monocarboxylic acids such as carbonic acid, formic acid, acetic acid, lactic acid etc. at least partially neutralized. In addition to unsaturated double bonds, the crosslinking agents used are preferably blocked polyisocyanates or resins which contain ester groups capable of transesterification.

The binders are neutralized with the neutralizing agents and, if appropriate, diluted with deionized or distilled water in the presence of solvents. Suitable solvents are primary, secondary and / or tertiary alcohols, ethylene or propylene glycol mono- or diether, diacetone alcohol or even small amounts of non-water-dilutable solvents such as petroleum hydrocarbon.

The aim is to keep the solvent content as low as possible, expediently less than 15% by weight and preferably less than 5% by weight, because with increasing solvent content the wrap worsens.

The bath solids are generally between 5 and 30% by weight, in particular above 8 and below 20% by weight. With increasing solids, the bath conductivity is increased and the deposition equivalent (amps - sec / g) is reduced, which means that the wrap can be increased. Due to the high concentration of layer-forming ions, the layer resistance goes through a maximum.

The bath temperature is between 20 and 35 ° C. As the temperature drops, the wrap increases. Temperatures below 20 ° C are uneconomical because the heat generated by the EC coating has to be dissipated again by plenty of cooling water. Temperatures above 35 ° C make it difficult to run the bath because too much solvent evaporates and hydrolysis phenomena on the binder system produce fluctuations in the electrical data.

The coating agent can additionally contain customary technical auxiliaries such as catalysts, leveling agents, anti-foaming agents, lubricants, etc. Naturally, additives should be selected which do not cause any disturbing reactions with water at the pH of the bath, do not carry in any disturbing foreign ions, and do not precipitate out in a non-agitated form when they are left standing for a long time.

The binders can be used pigmented or unpigmented. Such materials can be used as pigments and fillers which, owing to their small particle size below 10 f..lm, particularly below 5 µm, can be dispersed stably in the lacquer and can be stirred up again when standing. They must not contain any interfering foreign ions and must not react chemically with water or the neutralizing agent.

The pigmentation can be both white and colored. White is preferred. With the additional incorporation of interference pigments, it is possible to achieve metal-effect coatings with aluminum-silver-brass-copper-gold effects, etc. The pigments, such as titanium dioxide, are rubbed into a concentrated millbase and then adjusted to a pigment-binder ratio of about 0.1 to 1 to 0.7 to 1 with further binder. The wrap is increased by the incorporation of pigments. Instead of pigments, it is also possible to use finely powdered nonionic resins, such as powdered polycarbonate resins, epoxy resins and / or blocked polyisocyanates, the amounts added being selected so that they do not exceed the maximum sheet resistance. The binder, pigment content, bath solids content, solvent content, choice of neutralizing agent and the degree of neutralization are coordinated with the coating conditions such as bath temperature, deposition voltage and deposition time so that a complete coating takes place in the electrocoating bath, which after baking inside the can with layer thicknesses of at least 3 µm, is preferably at least 4 µm, very preferably at least 5 µm and at most 10 µm, particularly at most 7 µm povenfvei.

The EC painting is done in an immersion bath. The cans which are closed on one side can be guided at the can opening with the aid of a magnetic electromagnetic or mechanical holding device, which is also understood to mean the holding with a vacuum. The screwing of the can into the filled electro-dip lacquer basin and the position of the can in the electrophoretic coating ensures that the resulting gases can escape upwards. Due to the transport speed and the rotatable bearing, a flow is generated in the can, which dissipates the heat generated during electrophoresis. The simple construction of the hangers allows the cans to be closely spaced apart. Emptying the The can is turned by turning the can bottom upwards. Direct current is used as the current source. Depending on the type of binder, the socket is electrically connected via the holding device as an anode or as a cathode. Due to the encompassing of the paint and the deposition voltage and coating time required for the respective can shape, the can is completely coated inside and out. This process has the advantage that the entire coating or the remaining external and internal coating is carried out in a single process step and, due to the low mechanical outlay on the hanger, many cans can be coated side by side at the same time.

To achieve high throughput speeds, an auxiliary counter electrode is inserted into the can. The immersion electrode has a shape not determined by the can and is less than half the diameter of the can. It is preferably arranged so that it is inserted into the interior of the can at the same time as the can holder. In order to achieve a flow in the can that improves the paint quality, the inner electrode can be made hollow. Filtered varnish is pumped into the can through this feed line. By installing nozzles in the electrophoresis basin, which are directed towards the curved can bottom, gas bubbles can also be removed from the bottom wall by directed paint streams. The can is emptied by rotating the can with the can bottom up. When the hanger is extended, it is rinsed together with the cans first with ultrafiltrate and then with water, to which solvents and / or emulsifiers can optionally be added to avoid wetting problems. The lacquer is then baked at times of 1 to 300 seconds at temperatures of 180 to 250 ° C., preferably 120 to 180 seconds at 210 to 230 ° C. The conveyor belt with hanger and box is passed through the furnace. In a preferred embodiment, the can base can be predried and provided with a protective auxiliary layer. Afterwards, the transfer can take place on a conveyor belt leading through the drying oven. The opening of the can can be directed downwards or preferably upwards.

Another procedure is gradual, i.e. first the outer can body is painted conventionally and then - after an intermediate drying - the remaining part of the can (bottom and inside of the can) is coated electrophoretically, whereby the counter electrode is inserted into the can. This "reserve method" has the advantage that this is the case for each operation necessary paint system can be optimally matched to its special properties.

A special case of this process is the printing of the unpainted can with one or more essentially electrically non-conductive printing inks and a subsequent EC coating in which the non-printed parts of the can are then coated with EC varnish. When using this variant, an improved manufacturing process is possible. The printing of the bare, not flared can can be carried out in conventional printing machines, as was previously the case in the prior art. Then the printed can can will be printed with a common printing ink. For example, it is possible that 5 to 95% of the outer surface of the can is imaged with at least one printing ink (it is also possible to print several different printing inks in succession) in offset printing and is dried to produce a print which is stable after drying in the EG bath with a sufficient specific sheet resistance, for example of more than 10 ⁷ ohm × cm in the entire area of the printed image, so that no EC varnish is deposited here, and the printed substrate is coated with an EC varnish in a different color or transparent. The specific sheet resistance should naturally be so high that the deposition of the EC varnish is avoided. It is therefore preferably higher than 10 ⁸ ohm x cm and particularly preferably more than 10 ¹⁰ ohm x cm in the entire area of the printed image. Care should be taken with printing inks that they do not contain any constituents, in particular pigments, which would cause substantial electrical conductivity. The printing is carried out in a manner known per se, for example using the wet offset, dry offset or screen printing method. There is an unexpectedly sharp distinction between printed areas and areas coated in the EC bathroom. With the printing ink on the one hand and with the coating in the EC bath on the other hand, different layer thicknesses can be achieved if this is desired.

Continuous coating in the EC tank enriches the amine in the anionic binder and the carboxylic acid in the case of a cationic binder. To compensate for this effect, the refill materials are either neutralized correspondingly lower or the excess neutralizing agents are removed by electrodialysis. The rinse water is enriched by ultrafiltration and returned to the paint basin, which increases the degree of utilization of the paint and removes unwanted foreign ions.

In the drawing, an example of a system for carrying out the method according to the invention is shown schematically, namely shows

Fig. 1 shows a system in which the cans to be electrophoretically coated are held at their ends by an immersion bath and are conveyed by means of a single conveying element to the conveyor belt leading through a drying oven.

In the system according to FIG. 1, cans 2 which are open on one side are produced in this way by a chute 1 stated that their inwardly curved bottom 3 is outside. The chute 1 ends above a bath tank 4, which is filled up to a mirror 5 with an electrocoating liquid. The chute i ends above the liquid level 5. A star wheel 7 is rotatably mounted about a horizontal axis 6 above the bath container 4 in the direction of an arrow 8, which is not shown in detail in FIG. 1. On the outer circumference of this star wheel 7 there are mechanical holders 9 which mechanically grasp the sockets 2 at their open ends 10 and at the same time form the necessary electrical contacts. The counter electrode is arranged on the bath tank 4 and at a distance from the star wheel 7 below the liquid level 5.

Although only one star wheel 7 is indicated in FIG. 1, several star wheels of this type are actually arranged next to one another and can be rotated together about the axis 6. For example, a total of 16 star wheels 7 are provided side by side, so that 16 cans 2 can be passed through the immersion bath 4 at the same time. The star wheels 7 lie next to one another at a sufficient distance so that the adjacent boxes 2 do not touch one another.

The cans 2, as shown in FIG. 1, are guided by the starwheels 7 in a circular path through the immersion bath 2, with them being slightly inclined downwards, i.e. H. hit the liquid level 5 with a horizontal longitudinal axis and immerse in the bath in this position. This quickly floods the interior of the individual cans. The cans immersed in the bath move through the same, so that their longitudinal axis becomes more and more vertical, so that the air inside the cans can escape through the opening that points upwards and the cans are accordingly quickly completely filled with liquid. The immersed cans 2 are electrophoretically coated with the lacquer of the immersion bath filling as they pass through the immersion bath.

At the end of the run through the immersion bath, the cans are again inclined slightly, i.e. with approximately horizontal longitudinal axis lifted out of the bath and then tilted further, so that the bath liquid in them runs out with certainty.

Above the star wheels 7 there is an endless magnetic tape 11 to which the coated cans 2 released by the holders 9 are transferred with their base 3 lying on the tape. This magnetic tape 11 serves as a transfer section, and the wet film applied to the cans can be predried. It is also possible to carry out rinsing operations on the coated cans 2 in the area of the magnetic tape.

The cans 2 are transferred from the magnetic tape 11 to a further magnetic tape 12, on which the cans 2 are held with their open ends. This magnetic tape 12 transfers the cans 2 to a conveyor belt 13 of a drying oven 14, on which the cans 2 are placed with the floor facing downwards at a mutual distance from one another in the exemplary embodiment shown.

After passing through the drying oven 14, the electrophoretically applied coating of the cans 2 is dry, so that the cans can now, if desired, also be labeled or printed.

If for any reason the cans 2 are to be passed through the drying oven 14 with the opening 10 downward, the magnetic tape 11 can deliver the cans 2 directly to the conveyor belt 13 of the drying oven 14. It is essential that the cans 2 guided one behind the other and next to one another are always moved at a sufficient distance from one another that they cannot touch one another to rule out surface defects on the coating with certainty.

The system shown in Fig. 1 can be used in connection with existing drying ovens 14, i.e. the drying oven 14 and its conveyor belt 13 need not be converted or dealt with for use with the upstream system parts. The system shown in the drawing can accordingly be operated with existing system parts.

example 1

An anionic, self-crosslinking acrylate resin according to DE-B-16 69 107 was neutralized with ammonia and diluted to a solids content of 15% by weight with deionized water. A flared can (diameter 65 mm, length 116 mm) was held at the flanged edge with an electrically conductive clamp and carefully immersed completely in a conductive container insulated against earth and filled with diluted lacquer with a diameter of 19 cm. The box was connected to the anode, the outer vessel and the auxiliary electrode as a cathode to a direct current source. The auxiliary electrode inside the can had an immersion depth of 8 cm and an electrode diameter of 2 cm. After rinsing with water, the mixture was baked in a forced air oven at 215 ° C. for 3 minutes. The inside and outside of the can was completely covered with a thin clear varnish that was pore-tight.

Measured values, see Table 1.

Example 2

A deep-drawn metal can is washed, dried and printed in an all-round printing machine according to the dry offset process with an electrically essentially non-conductive red printing ink of the usual composition with a decor imagewise under the usual prestressing to produce a pore-free, uniform ink layer. After drying, the printed image has a specific sheet resistance of approximately 2 × 10 ⁸ ohm × um. The can printed in this way is dried in a conventional manner for 70 seconds at 180 ° C. in a continuous oven, then drawn in, crimped and, as described in Example 1, coated with a white pigmented BC lacquer which contains a carboxyl group-containing, self-crosslinking polyacrylate resin mixture . The total solids content of the bath is 15% by weight, the pigment: binder ratio 0.5: 1, the MEQ value 49, the pH value 8.8. The pH is adjusted with ammonia. The bath conductivity is 170 ° wScm ^-1 . The box is connected as an anode and the EG basin, which is insulated against earth, as a cathode. Separation voltage: 110 volts. Deposition time: 15 seconds. After coating, the can is rinsed with deionized water and dried on a wire rack with the opening facing upwards in a drying oven at 210 ° C. for 90 seconds. The deposition conditions, in particular voltage and time, were chosen in such a way that a good wrap was achieved using an electrode which protruded into the can. The EC varnish was coated on the outside of the can on the non-printed metal surfaces and also inside the can. The layer thickness of white lacquer achieved is approximately 10 to 12 μm.

A clean and delimited, but not overlapping, coating is achieved in the EC bath. Instead of the deep-drawn box with a bottom used in the example, soldered or welded boxes can also be used, the solder or weld seams or places in the EG bath being coated properly.

The image-wise printing with decors can be done over the whole area as a raster print or as a line pattern.

Example 3

Carried out essentially as in Example 2. The can is printed with four colors in a conventional four-color printing machine. The EC coating is carried out on the areas that have not yet been printed with a clear varnish that contains an externally cross-linking acrylate-melamine-resin system as a binding agent. Separation conditions: 15 volts, 15 seconds, 25 ° C. Layer thickness of the EG coating after baking: 7 to 8 µm. The coating was only done with an inner electrode in an insulated EG basin.

The term "slightly" in connection with the definition of the inclination of the cans upon entry and exit from the immersion bath means that the angle of the longitudinal axis to the liquid level is above 1 °, particularly preferably above 3 °, and preferably less than 20 °, particularly preferably less than 15 °.

Claims (9)

1. A process for electrocoating of metal cans open at one end with subsequent drying, characterized in that each can is led through an electrocoating bath and in the course of this, in a period of more than 3 to less than 60 seconds, is coated with a wet film having a film electrical resistivity of at least 0.6 x 10⁸ ohm x cm depositing on its surface, the can being dipped into the bath in one continuous operation with its opening pointing obliquely downwards, moved when submerged in the bath so that its opening points upwards, and then, with its opening pointing downwards, lifted out of the bath and then led by a continuous means of transportation through one or several drying ovens, several cans simultaneously being coated and dried, beside each other and distanced from each other, and a mounting on a transporting element provided for the individual cans being electrically con nected as an electrode for electrocoating, while auxiliary counter-electrodes, insertable into the individual cans and lying at a distance from the inside wall of the cans exceeding half the radius of the cans, are used.

2. A process according to claim 1, characterized in that the cans are led through the bath on a path in the form of a circular arc.

3. A process according to one of claims 1 or 2, characterized in that during the coating the cans are held by their open end on a transporting element leading them through the bath.

4. A process according to one of claims 1 to 3, characterized in that the cans are initially beaded at their open end, then washed, subsequently coated and finally dried and optionally labelled or printed.

5. A process according to claim 4, characterized in that after coating and before drying the cans are rinsed with water.

6. A process according to one or more of claims 1 to 3, characterized in that after lifting out of the bath the cans are put, distanced from each other, on a continuous means of transportation leading through one or several drying ovens.

7. A process according to one of claims 1 to 6, characterized in that, after washing, the cans are first lacquered externally on the body and dried aid then their bottom and interior are coated in the electrocoating bath.

8. A process according to claim 7, characterized in that the cans are printed on the body with one or several printing inks that are essentially non-conductors of electricity and then coated in the electrocoating bath.

9. A process according to claim 8, characterized in that 5 to 95 % of the body of the can is printed pictorially with at least one printing ink in offset or screen printing and dried, with production of an imprint which after drying is resistant in the electrocoating bath with a film specific resistivity of more than 10⁷ ohm x cm in the whole area of the print image, onto which a differently-coloured or transparent coating is applied in the electrocoating bath.

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