CH716413A1 - Method and device for the production of easy-open lids and easy-open lids. - Google Patents

Abstract

The invention relates to a method for the production of tear-open lids in which a lid blank is treated on both sides with a lacquer, from the lid blank a lid ring (2) with a central removal opening, which is surrounded by an initial flange, is drawn in from the initial flange Sealing flange (7) and a collar (4) projecting away from the sealing flange (7) are formed, on the collar (4) an annular strip (32) made of a thermoplastic material compatible with the lacquer layer on a collar outside (41a) facing away from the removal opening or is applied to the inside of the collar (40) facing the removal opening, the collar (4) is rolled up at its free end (31) to the outside of the collar (41a) or to the inside of the collar (40) until the curl is fully in contact with the annular strip (32) and a tear-off film is sealed onto a sealing surface of the sealing flange (7).

Description

description

Field of the invention

The invention relates to a method for producing easy-open lids, a device for producing easy-open lids and a tear-open lid according to the respective independent claim.

background

Tear-off lids are used to close containers and are typically used in the food industry for packaging food. The tear-off lids comprise a lid ring which is attached to the opening of the container. A tear-off film is attached to the lid ring, which must be removed before the contents of the container are consumed. If such a container, which is closed with the tear-off lid, contains a liquid, corrosive product, such as salt water, the bare cut edge of the lid opening of the container can corrode. In the case of a tear-off lid with a so-called retort-curl, the rolling of the area with the cut edge upwards and inwards and with the covering by the tear-off foil provides a certain protection against the influence of the product. The bare or possibly corroded cut edge is also not visible. However, depending on the aggressiveness of the product and the storage time of the filled container, traces of corrosion can still be visible. In EP-A 1 153 840 it is proposed that the tear-off film should also be sealed onto the curl itself, as a result of which the cut edge is protected from the contents of the can by a seal. It turns out, however, that the sealing both on the sealing flange and also on the curling in production with a high manufacturing rate is difficult to master perfectly. WO-A 02/790041 incidentally mentions that the gap created during the curling can be filled with the heat-seal coating of the tear-off film without explaining how this would actually be feasible in the industrial production of tear-off films. Known tear-off foils are only provided with a very thin heat-sealing layer and it is not apparent to the person skilled in the art how this layer can be used to fill the gap when a heat-sealing known to the person skilled in the art is carried out. The possibility mentioned in WO-A 02/790041 can therefore hardly be implemented in practice. WO 2018/191828 A1 proposes that, before the free end of the collar is rolled up, a band-shaped strip of plastic is applied to the inside of the collar. Nonetheless, even with this solution, in rare cases the contents of the container may come into contact with the cut edge, making the view unappetizing for the consumer.

Presentation of the invention

The invention is based on the object of creating a method and a manufacturing device for tear-off lids, with which a tear-open lid can be produced industrially at high rates and at low cost and which, even with corrosive products, has the possibility of contamination of the contents by corrosion of the cut edge minimized.

The object is achieved in a first aspect of the invention with a method for producing tear-open lids according to claim 1 and in a second aspect of the invention with a device for producing tear-open lids according to claim 10.

In that an annular strip is applied to the outside or inside of the collar and then the collar is rolled up to form a so-called "reverse curl" towards the outside of the collar or to form the "retort curl" towards the inside of the collar However, the cut edge exposed as a result of the punching is brought into contact with the annular strip and sealed by it.

If the subsequent curling of the collar to form the "reverse curl" takes place in accordance with the outside of the collar, the product is also prevented from accumulating between the curling and the tear-off film, with the cut edge being protected from corrosion at the same time even more reliably There is a risk that the user himself or the rest of the contents in the container will come into contact with this accumulation of contents after the tear-off film has been peeled off. Last but not least, the appearance is improved after the tear-off film has been peeled off since the user does not see any "dirty" curling.

The preferred positioning of the ring-shaped strip in the corner area on the outside of the collar is advantageous for reverse curl, as this offers very good stability due to the partially horizontal application, in contrast to a completely vertical application on the wall of the collar.

[0008] Another object of the invention is to create a tear-open cover which does not have the disadvantages mentioned and which can be produced in a cost-effective manner on an industrial scale at high rates and quality.

This object is achieved with a tear-off cover having the features of claim 15.

Brief description of the drawings

[0010] Further refinements, advantages and applications of the invention emerge from the dependent claims and from the description that follows with reference to the figures. Show:

1 shows a schematic side view of an apparatus for producing tear-open lids;

Fig. 2

a vertical sectional view of a cover ring in the production of a tear-off cover according to the invention;

Fig. 3a

an enlarged view of part of the cover ring from FIG. 2 after further manufacturing steps in a first embodiment;

Figure 3b

an enlarged view of part of the cover ring from FIG. 2 after further manufacturing steps in a second embodiment;

Fig. 4

a schematic representation of the processing station for applying the seal, in particular with the positioning of the application nozzle for applying the plastic for a tear-off lid with reverse curl;

Fig. 5

the cover ring from FIG. 2 after the edge of the removal opening has been rolled up;

Fig. 6

a plan view of the lid ring of a tear-off lid with retort curl; and

Fig. 7

a top view of the lid ring of a tear-off lid with reverse curl.

Definitions used below

For the present text, the following terms are defined:

- With regard to a collar 4 (Figs. 3a, 3b), an inside collar 40 directed towards the removal opening and an outside collar 41a directed away from the removal opening,

- With regard to the lid blank 1, the lid ring 2 and the tear-off lid 10, a lid outside or "outside" in the direction of the surroundings of the later container closed with the tear-off lid (reference numerals 7, 40) and a lid inside or "inside" for the the side facing the interior of this container (reference numerals 41a, 41b in FIGS. 3a, 3b).

Ways of Carrying Out the Invention

Fig. 1 shows schematically an apparatus for producing tear-open lids. Fig. 2 shows a vertical sectional view of a cover ring in the production of a tear-off cover according to the invention and Figs. 3a and 3b each show an enlarged view of a part of the cover ring of FIG Description of the cover rings shown, reference is made again and again to FIG. 1 in order to show the relationship with the individual manufacturing steps or processing stations.

At the beginning of the transport path of the manufacturing device 20, a stack 12 is shown which contains a plurality of cover blanks 1, which are individually stacked and processed along the transport path by different processing stations, with cover rings 2 being formed from the cover blanks 1 first and then these can be processed further up to the finished tear-off cover 10. The cover blanks 1 are, for example, round disks made of coated metal that is largely protected against corrosion, such as tin-coated steel, also known as tinplate, or tin-free steel (TFS). TFS is understood to mean a steel provided with an electrolytically applied chrome coating (Electrolytic Chromium Coated Steel, ECCS). In the context of this invention, TFS has proven to be particularly well suited because, due to the electrolytic deposition of the chromium, it provides a good substrate for the further processing steps (good adhesion for paints).

Since the chrome layer on the later inner side of the lid 41a, 41b should not come into direct contact with the contents of the can, e.g. food, and the later outer side of the lid 7, 40 should be hot-sealable in some areas, the sheet metal is on both sides, at least in the relevant areas of the sealing flange 7 and the collar 4, with respect to the inside of the lid 41a, 41b, preferably on the whole inside of the lid 41a, 41b with a lacquer layer described in more detail within the scope of the present invention. The outer lacquer layer can be different from the inner lacquer layer, but in the context of this invention it should have at least similar properties, in particular with regard to polarity and melting points. The same paint is preferably used for both paint layers.

Similar polarity is to be understood to mean that both are either apolar or polar, the same polarity means that they have the same degree of polarity.

In order to improve the adhesion of the paint layer on the sheet metal, it has been found to be preferred to provide the sheet metal with a primer before the paint is applied. Primers or adhesion promoters for metal surfaces are known and commercially available. The choice of primer depends, among other things, on the composition of the paint whose adhesion it is intended to improve. Since the chrome coating is oxidized in the contact area with air, adhesion can be achieved, for example, by means of special silanes which, in addition to the silanol groups, contain functional groups that are also part of paint components. In addition, suitable primers do not contain any wax components.

In the context of this invention, suitable paints contain at least one component which is liquid at room temperature and which can be a resin component and / or a solvent. Examples of suitable resin components are:

se thermosetting epoxy resins, such as epoxyphenol resins, or polyester resins. Another type of paint contains thermoplastic materials in particle form in a solvent, in which they dissolve when the temperature rises, so that when the solvent is removed they form a continuous film with a suitably high melting point. One such type of product based on polyvinyl chloride is known as an organosol.

As heat-sealable materials, polyolefins are mostly used in pure form or in a mixture with one another, such as polyethylene, polypropylene and mixtures thereof. The heat-sealable materials can be added to the thermally curing or thermally layer-forming lacquer, e.g. in particle form.

A lacquer coating (including the heat-sealable layer) comprises epoxy and polypropylene, for example in a quantitative ratio of 80:20 to 95: 5, preferably 85:15 to 90:10, such as 88:12.

The strip 32 is usually a thermoplastic material that contains at least one polyolefin or consists of at least one polyolefin. Preferred polyolefins are polyethylene, polypropylene and mixtures thereof, in particular a mixture of polypropylene and polyethylene with a melting point of approx. 150.degree. In special cases it can be advantageous to use modified polyolefins, such as graft polymers and / or block polymers, which, due to functional groups, optimize the adhesion to the cut edge 31, for example.

All materials that have to be melted during application should have a melting point which - if the lid is subjected to thermal sterilization - is at least 10 ° C, preferably at least 20 ° C above the sterilization temperature, but should be as low as possible for reasons of process economy should, ie at a sterilization temperature of approx. 130 ° C, preferably approx. 150 ° C.

So that the tin and in particular the chromium layer is covered completely and pore-free, layer thicknesses for the primer from 5 to 15 pm, preferably from 7 to 12 pm and for the lacquer layer (including a heat-sealable layer) from 5 to 12 pm, preferably from 5 to 8 pm advantageous.

The lid blanks 1 have, for example, a diameter of 11 cm. These blanks have already been preformed at their edge 6 by a processing machine, not shown, and the formation of the edge 6 is later used to attach the finished tear-off lid to a container or a can by means of a folded joint. This is known to the person skilled in the art and is not explained further here.

A conveyor 22 (Fig. 1), which conveys the cover blanks, the cover rings and the tear-off cover in the manufacturing device 20 along the transport path in the direction of arrow A from one processing station to the next processing station, is formed in particular by two toothed belts running in parallel, on which receptacles for the cover blanks or cover rings are provided, as is known to the person skilled in the art from WO 2006/017953 and is therefore not explained further here. At the respective processing stations, which are only shown schematically here, the cover blank to be processed is lifted off the conveyor device, processed by the processing station and given back to the conveyor device. This is indicated by arrows pointing up and down at the processing stations.

In a punching processing station (not shown), a cover ring 2 is first formed from the cover blank 1 by cutting out a central part of the blank and disposing of it as waste. This forms the removal opening 15 (see FIG. 6 or 7) of the later container, which is closed with the tear-off film in a later manufacturing step. Following the removal opening 15, there remains an initial flange 44 (see FIG. 2), which is further processed later. The metal material lies bare at the cut edge 31 of the initial flange or the sheet metal of the cover ring 2 is no longer protected there by the coating. In a processing station 23, the edge of the initial flange 44 is pulled up to form a collar 4 with reference to FIG. 2. As can be seen from the synopsis of FIGS. 2 and 3, after this processing step the initial flange 44 is divided into two sections, which result from the drawing of the initial flange in a drawing station 24. One section is the already mentioned collar 4 and another section is identified by 7 and represents the sealing flange, which later serves as a surface for sealing the tear-off film. Together, the two sections form a corner region 45, which is indicated in FIGS. 3a and 3b with the corresponding arrow. The collar 4 has an inner side 40 of the collar facing the removal opening and an outer side 41a of the collar facing away from the removal opening, and the cover blank 1, the cover ring 2 and the tear-open cover 10 have an outer side 7, 40 and an inner side 41a, 41b of the cover. In the corner region 45, FIG. 3a shows a strip 32 which is ring-shaped with respect to the circumference of the cover ring and is essentially triangular in cross section, and FIG. 3b shows a strip 32 which is ring-shaped with respect to the circumference of the cover ring and essentially L-shaped in cross section 32 shown.

As already described above, the annular strip 32 is made of thermoplastic material and forms a seal for the cut edge 31 when the collar 4 is later rolled in, which is described below.

The application of the annular strip 32 according to the invention is carried out by applying melted, liquid plastic material in an application station 24a (according to the third processing station), which is arranged between the drawing station 24 and a rolling station 25, by means of an application nozzle 3, which is shown in FIG Fig. 4 is shown. Accordingly, the application nozzle 3 comprises an outlet opening 3a which is designed in terms of shape in such a way that the annular strip 32 fills the corner region 45 and is thus essentially triangular, which can be seen in FIG. 3a. With reference to FIG. 3b, the outlet opening can, for example, also be shaped in such a way that the annular strip 32 is applied in a substantially uniform thickness d2 over its entire width. When

"Width" in this context is understood to mean the sum of the two strip legs S1 and S2 shown in FIG. 3b. The length of the two legs S1 and S2 need not be the same in both embodiments from FIGS according to the dimensions (diameter) of the tear-off cover to be produced or depending on the size relationships between the removal opening and the ring width of the cover ring. In the context of FIGS. 3a and 3b, an element of the application nozzle defining the outlet opening can be exchanged for another such element, which is a larger / smaller one and / or has a differently shaped outlet opening.

In the embodiment of FIG. 3b, the strip 32 preferably has a thickness d2 in the range from 0.05 millimeters to 0.5 millimeters, preferably a thickness of approximately 0.1 millimeters.

The application station 24a comprises a spacer element (not shown) to maintain a substantially constant distance between the application nozzle 3 and the outside 41a of the collar 4, so that the annular strip 32 in the triangular embodiment (Fig. 3a) a substantially has a constant maximum thickness d1, in particular a maximum thickness d1 of 0.4 mm, over its entire length and, in the embodiment from FIG. 3b, in addition to its essentially constant thickness d2 over its entire width, also has an essentially uniform thickness d2 over its entire length. The length here denotes the total circumference of the ring-shaped strip. The term “fully” in this text also relates to this. During the application, care is therefore taken that the distance between the outlet opening 3a remains essentially constant when the liquid plastic is applied, so that the thickness d2 or the maximum thickness d1 of the strip 32 is essentially constant and the strip can be made thin. This can be done, for example, in that the cover ring 2 is precisely centered on a receptacle in the processing station 29 and the application nozzle 3 with the outlet opening is at a defined distance from this receptacle with a subsequent centering takes time, however, so that for the very high production rates aimed at, the preferred procedure is that the cover ring in the processing station is pressed with the collar outside 41a against a roller that is precisely positioned with respect to the nozzle position during application, whereby the distance between the Application nozzle for Kr agenaussseite 41 a is precisely defined in a simple manner.

The application nozzle 3 is preferably stationary in an application position for the annular strip 32. The cover ring is moved in a rotating manner in the processing station 29 and the outside of the collar 41a is moved past the outlet opening 3a of the application nozzle in order to apply the plastic in liquid form to the rotating cover ring via the application nozzle 3. Alternatively, the application nozzle could be moved around the cover ring, while the cover ring would be held stationary. However, this alternative is not preferred because it would be more difficult to maintain the required strip thickness and the process would take longer.

In a preferred embodiment, the application station 24a comprises a pivot element (not shown) for pivoting the cover ring 2 from a feed position in which the cover ring can be introduced into the application station (normally horizontal), into the application position, and back. Depending on the embodiment of the application station, it can be advantageous to move the cover ring from its horizontal position from FIG. 3a or 3b into an inclined position so that the application nozzle can more easily reach the corner area 45. Of course, an application in the horizontal position of the cover ring is also possible, as shown in FIG. 4.

The processing station 29 comprises a heated supply line and a heated and controllable valve (not shown), wherein the application nozzle 3 can be supplied via the valve with the melted plastic, which passes through the channel 3b to the application opening 3a. In this context, it is noted that the application is preferably understood here as application and not as spraying. In this way, a shape-related, better-defined strip is achieved.

The cover ring 2 is thus raised at the processing station 29, possibly pivoted, set in rotation and the application is activated when the cover ring has reached the correct position with respect to the outlet opening 3 a of the application nozzle 3. After at least one full turn, when a continuous strip is formed in the corner area 45, the cover ring with the strip 32 is moved back down to the conveyor device, the rotation being stopped so that the cover ring is placed back onto the receptacles of the conveyor device 22 can. When the thin plastic strip is applied, the cover ring can be rotated at a high rotational speed, which is understood to mean a rotation of more than 200 revolutions per minute. A preferred speed of rotation is in the range from 400 to 600 per minute.

After the application of the annular strip 32, the promotion to the roll-in station 25 takes place. The plastic of the strip 32 cools as soon as it is applied to the cover ring and solidifies, so that the plastic does not flow during the further promotion and the strip is in the shape shown in Fig. 3a or 3b is stable. At most, a coolant, for example in the form of a fan, can be provided in the application station 24a or processing station 29.

In the embodiments shown in FIGS. 3a and 3b (or beforehand in a separate step), a curvature (also called "precurl") towards the outside (away from the removal opening) has been produced at the upper free end of the collar 4, In an embodiment with retort-curl (not shown), this curvature points inwards accordingly (towards the removal opening). In the curling station 25, the curling is carried out upwards and towards the outside of the collar 41a The indication of direction "upwards" relates to the position of the cover ring shown in FIGS. 2 and 3 (with the intended top of the cover ring pointing downwards in these figures). When the reverse curl is formed, the strip 32 forms a seal which the

Prevents liquid from entering the inside of the reverse curl. The bare cut edge 31 is thus protected against the influence of a liquid located in the subsequent container. It does not matter whether the curling takes place in such a way that the cut edge 31 is partially embedded in the band 32 or whether it is only in contact with the band 32. Even the opposite, that the cut edge 31 cuts through the band 32 and rests against the metal of the collar outer side 41a, does not interfere with the function of the strip 32. In one embodiment, however, it is preferred if the cut edge 31 lies within the reverse curl, as shown in FIG. 5. In any case, it is only important that the curl is in full contact with the strip 32 and thus a sealing effect is achieved. This full circumferential contact is brought about with regard to the pressure of the curling on the ring-shaped strip in such a way that the seal withstands subsequent sterilization (typically 60 minutes at 121 ° C.). The seal also ensures that none of the contents of the container to be closed with the tear-open lid come into contact with the unprotected cut edge. The curl that forms the edge of the removal opening ensures that the user of the container is protected from the sharp-edged cut edge when removing the contents.

The previous manufacturing steps have been carried out in a position in which the cover blanks and cover rings, as mentioned, were arranged with their later top or with the sealing flange 7 pointing downwards. This is the preferred embodiment also in the case of the present invention, although the cover blanks or cover rings could also be transported upside down if this would be expedient. As mentioned, the blank or the ring is lifted off the conveyor device in the individual processing stations 23, 24, 24a, 29 and 25, processed and put back again, whereupon the conveyor device carries out conveying steps which lead the lid blanks or lid rings to the next processing station .

In embodiments of the invention, the curling is heated in order to at least partially melt the strip 32 at least in the contact area with the metal of the lid or the coatings thereon and thus establish a good connection, which is explained below.

In a first exemplary embodiment, a processing station 35 is provided in front of the turning station 26, in which processing station 35 the heating of the curling takes place. This can be carried out in such a way that also at this processing station 35 the cover is lifted off the conveying means 22, followed by heating in the processing station 35 and then placing on the conveying means. The cover ring or its curling can, however, also be heated in the processing station 35 while it is located on the conveying means 22, that is to say without being lifted off the conveying means. In the processing station 35 in front of the turning station, the cover ring is still with the curl pointing upwards. This enables heating from above. For this purpose, an induction heating device is preferably provided in the processing station 35. The configuration of such a heating device is known to the person skilled in the art and does not need to be explained in more detail here. Instead of an induction heating device, an infrared radiation source or a hot air source could also be provided.

In another exemplary embodiment, the processing station for heating the curling can be provided after the turning station and is shown in the example shown as processing station 35 '. In this processing station 35 'the curling is at the bottom and accordingly it is preferred if the heating source acts from below, so that it can be more advantageous to design the processing station 35' in such a way that the cover ring 2 is lifted from the conveying means 22 in it to carry out the machining with the heating source. In this case too, induction heating or another type of heating can be provided.

After the curling has been heated, cooling can be provided, for example by means of a fan. This is particularly advantageous if the processing station 35 ′ is present after the turning station 26 and a presealing station 27 is also provided for presealing the tear-open film on the sealing flange 7. Otherwise, the heating of the curl can have an undesirable effect on the temperature for the pre-sealing.

As an alternative to heating in a processing station 35 or 35 'or in addition to this, the heating of the curling can be provided in a sealing station, which is preferably divided into a pre-sealing station 27 and a main sealing station 28.

If the manufacturing steps are carried out with the sealing flange 7 pointing downwards, the cover ring is now turned in the turning station 26, so that during further processing the sealing flange 7 is at the top after the turning station in the conveyor 22 and in the processing stations. Fig. 5 shows this position, which corresponds to the intended use of the tear-open cover. In this position, the cover ring is thus conveyed into the sealing station in which the tear-off film is sealed over the removal opening 15. The tear-open film is completely sealed onto the area shown by the arrow 7. This takes place in two stages with the pre-sealing station 27 and the main sealing station 28. The sealing process is also known to the person skilled in the art and is not explained further here. Further processing stations can follow in which the sealing film is embossed, the tear-off tab is positioned and a leak test is carried out. This is also known to the person skilled in the art and is not explained further here.

At the end of the manufacturing device 20, finished tear-off lids 10 are issued, the removal opening 15 of which is spanned by a tear-off film (not shown) which is sealed onto the sealing flange 7.

From a synopsis of FIG. 6, which shows a tear-off lid 10a with retort curl, and FIG. 7, which shows a tear-open lid 10 with reverse curl, the difference can be seen that in retort curl the curling with the annular Strip 32 is visible from above when the tear-off film is peeled off from the removal opening 15. To

Claims (16)

on the other hand, in the solution with the reverse curl, the curling and the strip 32 are not visible, since in this view they have been carried out downwards and towards the outside of the collar 41a. In addition to the fact that this results in a better appearance for the consumer, the solution with reverse-curl has the important advantage that no product can collect between the roll and the tear-off film. While preferred embodiments of the invention are described in the present application, it should be clearly pointed out that the invention is not limited to these and can also be carried out in other ways within the scope of the following claims. Terms used in the description such as “preferred”, “in particular”, “advantageous”, etc. relate only to optional and exemplary embodiments 1. A method for the production of tear-off lids (10), in which - a sheet or a blank cover (1) punched out of it made of tinplate or tin-free steel (Tin Free Steel or TFS) is treated on both sides with at least one lacquer in such a way that both sides have a lacquer layer of similar, preferably the same polarity, - A cover ring (2) with a central removal opening (15), which is surrounded by an initial flange (44), is formed from the cover blank (1) by punching; - A sealing flange (7) and a collar (4) protruding away from the sealing flange (7) are formed from the initial flange (44) by drawing, which together form a corner region (45); - A ring-shaped strip (32) made of a thermoplastic material that is compatible with the at least one layer of lacquer is applied to the collar (4) on an outer side of the collar (41a) facing away from the removal opening (15) or on an inner side (40) of the collar facing the removal opening; - The collar (4) is rolled up at its free end (31) towards the outside of the collar (41a) or towards the inside of the collar (40) until the roll (33) comes into full contact with the annular strip (32) and - A tear-off film is sealed onto a sealing surface of the sealing flange (7). 2. The method according to claim 1, in which the sheet metal or the blank cover (1) punched out of it was subjected to a step which improves the adhesion of the paint layer, in particular a primer application, before the application of the paint layer. 3. The method of claim 1 or 2, wherein - In the corner area (45), an annular strip (32) made of plastic is applied over the full circumference by means of an application nozzle (3) on an outer side of the collar (41a) facing away from the removal opening (15); - The collar (4) is rolled up at its free end (31) towards the outside of the collar (41a) until the roll-up (33) comes into full contact with the annular strip (32); - A tear-off film is sealed onto a sealing surface of the sealing flange (7). 4. The method according to any one of the preceding claims, wherein an outlet opening (3a) of the application nozzle (3) for the plastic is designed in a shape-related manner such that the annular strip (32) is applied in a substantially uniform thickness (d2) over its entire width , in particular is applied, or that the annular strip (32) is applied, in particular applied, in such a way that it fills the corner region (45) essentially in a triangular cross-section. 5. The method according to any one of the preceding claims, wherein the distance between the application nozzle (3) and the cover ring (2) is kept constant during application, so that the annular strip (32) with a substantially uniform thickness (d2) over its entire Length applied, in particular applied, or applied with an essentially constant maximum thickness (dl) over its entire length, in particular applied. 6. The method according to any one of the preceding claims, wherein the cover ring (2) in a horizontal position, in particular with the sealing surface of the sealing flange (7) pointing downwards, is brought up to the application nozzle (3), and before the annular strip is applied ( 32) is pivoted from the horizontal position into an inclined position until the outlet opening (3a) of the application nozzle (3) is properly aligned on the corner area (45) or on the inside of the collar (40), and the cover ring (2) in the inclined position is rotated around its axis while the application nozzle (3) is held stationary. 7. The method according to any one of the preceding claims, wherein the lid ring on its lid outer side (7, 40) at least in the area of the sealing flange (7) and the collar (4) has a coating that is heat-sealable with a contact side of the tear-off film and wherein the lid inner side (41 a, 41 b) has a coating that is compatible with the contents and has a similar or the same polarity as the coating on the outside of the lid (7, 40). 8. The method according to any one of the preceding claims, wherein the cover ring has a primer layer which improves the adhesion of the paint layer under the paintwork. 9. The method according to any one of the preceding claims, wherein the annular strip (32) is applied by applying a melt-liquefied thermoplastic plastic, the thermoplastic plastic adheres to the lacquer layer on the outside of the lid (7, 40) and the lacquer layer on the inside of the lid (41a, 41b) and on the cut edge (31) and in particular where the plastic contains at least one polyolefin or consists of at least one polyolefin, in particular polyethylene and / or polypropylene . 10. Device (20) for producing tear-open lids (10) by means of the method according to one of the preceding claims, in which tear-open lids (10) each have a tear-open film sealed on a sealing surface (7) arranged around a removal opening (15), wherein the device (20) comprises a conveying device (22) for lid blanks (1), lid rings (2) and tear-open lids (10) as well as processing stations (23-28) which follow one another in the conveying direction (A) for processing the lid blanks, lid rings and Tear-open lids are provided, a first processing station as a punching station for forming a cover ring (2) from a blank cover (1), a second processing station (23) for forming the collar (4), a third processing station (24a) for applying the annular strip ( 32) are provided on the cover ring (2) and a fourth processing station (25) is provided for rolling the collar, which is designed in this way is designed so that the curl (33) comes into contact with the annular strip (32), and further at least one sealing station (27, 28) is provided which is designed to seal a tear-off film onto the sealing surface (7), characterized in that, that the annular strip (32) can be applied, in particular applied, to an outer side of the collar (41a) facing away from the removal opening (15) in the corner region (45) of the collar (4) or on an inner side (40) of the collar, and that the collar (4) can be rolled up towards the outside of the collar (41a) or towards the inside of the collar (40). 11. The device according to claim 10, wherein the third processing station (24a) for applying the annular strip (32) made of plastic comprises an application nozzle (3) with an outlet opening (3a), which outlet opening (3a) is designed in terms of shape such that the annular Strip (32) is applied in an essentially uniform thickness (d2) over its entire width, or that the annular strip (32) is essentially triangular in cross-section, and the third processing station (24a) has a spacer element for maintaining an essentially constant distance between the application nozzle (3) and the cover ring (2), so that the annular strip (32) has a substantially uniform thickness (d2) over its entire length, in particular with a thickness (d2) in the range of 0, 05 mm to 0.5 mm, preferably with a thickness of approx. 0.1 mm, or so that the annular strip (32) has an essentially uniform maxi paint thickness (d1) over its entire length. 12. Device according to one of claims 10 or 11, wherein the application nozzle (3) is stationary in an application position for the annular strip (32), the third processing station (24a) having a receptacle for a cover ring (2) that can be rotated by means of a drive. comprises in order to apply the plastic in liquid form to the rotatingly drivable cover ring (2) in liquid form via the application nozzle. 13. The device according to claim 12, wherein the third processing station (24a) has a pivoting element for pivoting the cover ring (2) from a feed position in which the cover ring (2) can be introduced into the third processing station (24a), into the application position, and back , includes. 14. Device according to one of claims 10 to 13, wherein the third processing station (24a) comprises a heated supply line and a heated and controllable valve, wherein the application nozzle (3) can be supplied with the melted plastic via the valve. 15. Tear-open cover (10) made of tinplate or tin-free steel (TFS) provided on both sides with a layer of lacquer, comprising a circumferential fastening section (6), a sealing flange (7) with a tear-off film sealed on this and a rolled-up collar surrounding the sealing flange (7) (4), which forms a corner area (45) with the sealing flange (7) and which laterally delimits the removal opening (15), the collar (4) facing a collar outer side (41 a) facing away from the removal opening (15) or to one of the The inside of the collar (40) facing the removal opening is rolled up, and is further characterized by an annular strip (32) made of thermoplastic material, which is ring-shaped and which is applied, in particular applied, to the outside of the collar (41a) in the corner area (45) or to the inside of the collar (40) The entire circumference of the strip (32) is in sealing contact with the collar (33), which is rolled up outwards or inwards, and the lacquer layer on the outside of the lid (7, 40) and the lacquer layer on the inside of the lid (41a, 41b) at least in the area of the sealing flange (7) and the collar (4) have similar or the same polarity and the strip (32) is made of thermoplastic material , which is compatible with the layer of lacquer on the outside of the lid (7, 40) and with the layer of lacquer on the inside of the lid (41a, 41b) and with the metal of the cut edge (31), ie adheres well to it, in particular a thermoplastic material that has at least one Contains polyolefin or consists of at least one polyolefin, particularly preferably polyethylene and / or polypropylene. 16. The tear-off lid (10) according to claim 15, wherein the collar (4) is rolled up towards an outer side of the collar (41a) facing away from the removal opening (15), and is further characterized by one applied to the outer side of the collar (41a) in the corner region (45), in particular applied, annular strips (32).