WO2001007330A1

WO2001007330A1 - Sealing ring, comprising a sealing diaphragm and production of the same

Info

Publication number: WO2001007330A1
Application number: PCT/EP2000/007039
Authority: WO
Inventors: Daniel Vetter; Jürg Frey
Original assignee: Alcan Rorschach Ag
Priority date: 1999-07-22
Filing date: 2000-07-21
Publication date: 2001-02-01
Also published as: AU6565600A

Abstract

The inventive method uses an uncoated metal sheet which is punched out in the shape of a ring and which is subsequently reshaped into a ring with a profiled cross-section. Either before or after the reshaping process, the sealing ring (4) produced is coated with a powder lacquer which can be sterilised and sealed, before the sealing diaphragm is applied (31). The invention also relates to a sealing ring consisting of crude metal, comprising a peripheral sealing surface for a sealable, peelable sealing diaphragm which is coated with a polyolefin-based lacquer.

Description

OPERATING MEMBRANE PROVIDED LOCKING RING AND ITS PRODUCTION

The invention relates to a method for producing a closure ring with a circumferential sealing surface for sealing a closure membrane and a border for applying the closure ring to the edge of the container, as well as a corresponding closure ring.

Containers made of sheet steel, aluminum, plastic or laminates made of paper and plastic are used for powdery, pasty or liquid contents. In order to ensure an airtight and / or liquid- or water vapor-tight seal, these must also be tightly sealed on the cover side for storage and transport, and yet be opened easily and without tools for consumption.

It is known, among other things, on the edge of the container, ie on the edge of the body forming the container Put the locking ring on and connect it to the container body by mechanical deformation, as is the case when applying floors that are not opened. The removal opening is closed by a membrane which is sealed with the ring. This membrane, usually made of aluminum or a laminate of sealable plastic and aluminum, can be peeled off from the ring or separated along a score.

The production of such rings has been known for a long time and is carried out by punching and bending operations from band-shaped or tabular material coated with lacquer. When the rings are punched out, they can not only be circular, but can also have any other shape that corresponds to the cross section of the container body to be subsequently sealed, a great deal of lattice-like waste arises, since both a part outside the ring and the future removal opening in can not be used in most cases. On average, punched out rings produce between 60% and 70% waste. In some cases, the central rondelles, which are created when the removal opening is punched out, can still be used for other purposes. In general, however, the demand for such rondelles does not coincide with that in each case in the production of the lock ring, so that either there are too many rondelles, or if there is a temporarily larger demand for rondelles, they have to be made from the full, which leads to higher material costs for the By-product leads and a sensible calculation of both the lock rings and the rondelles is impossible.

The use of uncoated starting material for the locking rings, in which the lead frames could be melted and reprocessed, has not previously been considered. This is because the locking rings cannot be used without appropriate corrosion protection. However, if, as is the case today, coated metal sheets are used, the waste, i.e. the leadframes are probably recycled, but the revenue that can be achieved on the market is considerably lower than with uncoated materials due to the significantly higher processing costs. This results in costs for the finished closure, which are often no longer competitive in comparison to other closure systems.

The varnish for the coating of the sheets must meet several conditions. In addition to excellent adhesion to the base made of raw metal, it meets the high requirements with regard to corrosion resistance and food suitability as well as sterilizability. Furthermore, and this is essential for the high demands of the consumer, he must allow the sealing membrane to be sealed on without it loosening during sterilization, but being easily removable from it to open the container. Coating with lacquer should be possible in one or more layers, the wet or powder lacquer used as coating material being able to change from layer to layer.

Commercial lacquers do not meet these requirements since they do not have one or more of the required characteristics.

Closures of the type mentioned at the outset are known and shown, for example, from the "Alcan packaging material" catalog from ALCAN RORSCHACH AG, dated 5.96. These known closures are also manufactured, among other things, according to Swiss patent CH 674 829.

The object of the present invention is now to provide a method for producing such a locking ring, in which the lead frames and roundels can be reprocessed with little loss of value, and to provide a corresponding locking ring.

This object is achieved on the one hand by the method according to the features of patent claim 1.

Surprisingly, it is possible to subsequently coat the ring-shaped blank according to the invention for the locking ring, which has been punched out of uncoated sheet metal, with a coating which also includes the cut edges and which fulfills the high requirements with regard to corrosion resistance with respect to the contents and at the same time enables the central sealing membrane to be sealed and the sterilization survives without damage. The rondelles and leadframes made of raw metal that are produced when punching out can be easily melted into new material. Due to their purity, their value is only slightly less than the value of the sheet used for production.

The necessary corrosion protection is applied after completion of the locking ring by coating with powder coating, which has the property of also protecting the cut edges properly. The powder coating also has the property that the sealed sealing membrane can be peeled off the sealing ring.

The invention is explained on the basis of an illustrated exemplary embodiment. Show it:

FIG. 1 shows a top view of the flat annular disks punched out from strip-like or sheet-like uncoated material,

FIG. 2 shows a top view of an individual annular disk before it is formed into a locking ring,

3 shows an enlarged cross section through the preformed locking ring. Annular disks 4 are punched out of a sheet or of strip-shaped, uncoated material 1, for example pure aluminum sheet.

In the following operation, the washer 4 is deformed in a deep-drawing process. The material used in its most cost-effective form is very easy to process.

Of course, depending on the requirements, the geometric shape of the border area 25 can also be designed differently than is shown schematically in FIG. 3. For an optimal stacking of the completed locking rings, the peripheral edge 27 can be slightly compressed. In a conventional manner, the necessary sealing material 29 is also injected on the concave side of the flange area 25 for sealing with the container body. The sealing of a closure membrane 31, which spans the center opening 15, takes place - as was previously the case with conventionally produced closure rings - before the closure rings are applied to a container.

A tendon-like section X on the center opening edge serves to form a sufficiently large sealing surface for the membrane 31, which is sealed onto the sealing area 9, also on the folded edge of a flap 32. The tab 32 is part of the membrane 31 and is folded against the center of the latter. This creates a straight line in the fold area Section that runs parallel to section X, so that sealing is perfectly possible even with round containers. The same is also possible for rings / cans with a non-round cross-section, because the placement of the torn-open tab 32 always comes to lie in an area with a small can radius. By forming the locally widened area X of the sealing surface 9, a sealing width of, for example, only 2 mm can be maintained over the entire circumference of the sealing area. It is therefore no longer necessary to design the entire sealing area, ie the area 9, so wide that a sufficiently wide sealing or contact area 9 is also present at the point where the tab 32 comes to rest. With a much narrower sealing area 9, this measure allows a sufficiently large sealing area, which enables the container to be sealed, to be achieved. Not only is material saved, but at the same time the container opening remains unchanged, the center opening becomes larger.

The coating serving as corrosion protection is applied to the finished locking ring before the sealing compound is introduced into the concave part of the Bördeis 25. The coating is carried out by powder coating, which is applied electrostatically and then melted.

To meet the complex conditions, a powder coating, as described below, is preferably used. The powder coating is preferably based on polyolefins, in particular polypropylene or polyethylene with polar functional groups. The use of such lacquers enables sealable coatings to be produced with the required high adhesion to the metallic surface. Acid or acid anhydride groups are modified as polar functional groups. Stabilizing the paint with antioxidants prevents embrittlement of the paint layer due to oxidation processes, such as those caused by heat sterilization and long storage. Due to the surface-specific stabilization of the powder with antioxidants, a particularly high antioxidant concentration is achieved at the location of the lacquer, which is particularly sensitive to oxidation. This enables particularly effective stabilization.

The powder coating is then applied using conventional powder coating systems, e.g. electrostatic powder spray guns, applied to the locking ring.

In a preferred embodiment of the invention, only the last lacquer layer is created with a powder lacquer stabilized with antioxidants.

According to the invention, a closure ring made of raw metal with a circumferential sealing surface for a sealable and peelable closure membrane is also provided, which is coated with such a lacquer based on polyolefins. Furthermore, the invention provides the use of such a lacquer for coating a corresponding locking ring. For example:

0.5 g of a suitable antioxidant, e.g. IRGANOX B215 from Ciba Specialty Chemicals Inc., Basel, is dissolved in 200 g acetone. After adding 200 g of a polypropylene powder grafted with maleic anhydride, the resulting mass is ground in a mortar for five minutes. This mass is then dried in a rotary evaporator at 80 ° C. until the powder has a free-flowing and processable consistency. The powder is then ready for application using conventional powder coating systems, e.g. electrostatic powder spray guns.

Claims

claims

1. A method for producing a closure ring with a circumferential sealing surface (9) for sealing a closure membrane (31) and with a flanged edge (25) for applying the closure ring to the edge of a container body, characterized in that: ^■ that an annular disc (4) punched out of an uncoated metal sheet and then deep-drawn by shaping a circumferential flanged edge (25) and the sealing surface (9) surrounding a central removal opening and coating the entire surface with a paint that is sterilisable and forms a sealable and peelable base.

2. The method according to claim 1, characterized in that a widening on the sealing surface (9) is formed on the closure ring on the periphery of the removal opening by a chord-like section (X).

3. The method according to any one of claims 1 or 2, characterized in that the coating of the locking ring takes place before or after the shaping of the disc (4).

4. The method according to any one of claims 1 to 3, characterized in that the coating of the complete surface is carried out by means of at least one layer of powder coating.

5. The method according to claim 4, characterized in that the coating is made with powder coating based on polyolefins, which is modified with polar functional groups.

6. The method according to claim 5, characterized in that polypropylene or polyethylene are used as polyolefins.

⁷ . Method according to one of claims 5 or 6, characterized in that acid or acid anhydride groups are used as polar functional groups.

⁸ . Method according to one of claims 5 to 7, characterized in that the powder coating is stabilized with antioxidants.

⁹ . Method according to one of Claims 4 to 8, characterized in that 0.5 g of a suitable antioxidant is dissolved in 200 g of acetone and, after adding 200 g of a polypropylene powder grafted with maleic anhydride, the resulting mass _is ground in a mortar for five minutes and _d connect the earth in a rotary evaporator at 80 ° C is dried until the powder has a free-flowing consistency.

10. The method according to any one of claims 5 to 9, characterized in that only the uppermost layer of lacquer forming the sealable surface is stabilized with antioxidants.

11. Locking ring made of raw metal, with a circumferential sealing surface for a sealable and peelable sealing membrane, which is coated with a varnish based on polyolefins.

12. Locking ring according to claim 11, characterized in that the polyolefin is polypropylene or polyethylene with polar functional groups.

13. Locking ring according to claim 12, characterized in that acid or acid anhydride groups are modified as polar functional groups.

14. Locking ring according to one of claims 11 to 13, characterized in that antioxidants are used to stabilize the lacquer.

15. Locking ring according to claim 14, characterized in that the stabilization takes place on the powder grain surface of the lacquer.

16. Locking ring according to one of claims 11 to 15, characterized in that the lacquer is obtainable by dissolving 0.5 g of a suitable antioxidant in 200 g of acetone and adding 200 g of a polypropylene powder grafted with maleic anhydride, grinding the resulting mass during 5 Minutes in a mortar and then drying the mass in a rotary evaporator at 80 ° C until the powder has a free-flowing consistency.

17. Closure device according to claim 16, characterized in that IRGANOX B215 is used as the antioxidant.

18. Use of a varnish based on polyolefins for coating a closure ring made of raw metal with a circumferential sealing surface for a sealable and peelable closure membrane.